A highly flexible polymerization technique to prepare fluorescent nanospheres for trace ammonia detection

International Nuclear Information System (INIS)

Waich, K.; Sandholzer, M.; Mayr, T.; Slugovc, C.; Klimant, I.

2010-01-01

The preparation of pH-sensitive nanospheres by emulsion polymerization for the detection of trace levels of ammonia is described. A fluorescent, polymerizable xanthene dye was copolymerized with styrene, crosslinkers and further copolymers aimed at enhancing the sensitivity to obtain materials for sensing of ammonia. A half-seeded technique was used to obtain stable emulsions of the monomers which were cured to obtain nanospheres with covalently attached active components. The nanospheres were embedded in a silicon matrix and the sensor films obtained were investigated regarding their response to ammonia at concentrations between 25 and 1,000 ppb. Sensors containing polystyrene nanospheres crosslinked with divinylbenzene showed the best performance in ammonia measurements exhibiting detection limits (LODs) of less than 25 ppb ammonia.

Limited-preparation CT colonography in frail elderly patients: a feasibility study.

LENUS (Irish Health Repository)

Keeling, Aoife N

2010-05-01

Full colonic preparation can be onerous and may be poorly tolerated in frail elderly patients. The purpose of this study was to prospectively assess the image quality and diagnostic yield of limited-preparation CT colonography (CTC) in elderly patients with suspected colorectal cancer who were deemed medically unfit or unsuitable for colonoscopy.

Establishment of limits of detection and decision

International Nuclear Information System (INIS)

Mende, O.; Michel, R.

1995-01-01

The purpose of this project was to develop and test procedures to establish limits of decision and detection for spectrometric nuclear radiation measurements. Beside the determination of the limits of application of DIN 25482 part 2 and 5 - both primarily suitable for high resoluted spectra areas -the statistical model was expanded in such a way that henceforth blanks and influences of sample treatment can also be taken into account; the corresponding procedures to calculate the limits of decision and detection have a high precision. Additional procedures of calculation were developed to take the special characteristics of the analysis of complex spectra areas into account. (orig.) [de

Working with Detection Limits in X-Ray and Nuclear Spectrometry

International Nuclear Information System (INIS)

Van Espen, P.

2003-01-01

Full Text: Detection limits are important in many measurement procedures. Especially in analytical work we often need to take a decision about the presence or absence of a compound, or we need to guarantee that or instrument can detect the compound. Especially in regulatory work the concept of detection limits plays a crucial role. Data acquisition in x-ray and gamma-ray spectrometry is done by counting events for a preset time; hence the fluctuations in the observed spectra are governed by Poisson (counting) statistics. This makes the calculation of detection limits in principle very easy. However it is observed that there exists a great deal of confusion concerning the definition(s) and especially concerning the practical calculation and reporting of detection limits. In this contribution a simple but rigorous treatment of the concept of detection limits will be given, emphasizing on aspects such as a-priori and a-posterior i limits and on the effect of sample blank and instrumental blank in the calculation of the true detection limit. The problem of near zero background as observed in e.g. total reflection x-ray fluorescence analysis (T-XRF) and some low level counting applications will also be discussed. In this case Poisson statistics might not be applicable, affecting the decision limits with respect to the presence of absence of a signal. Finally handling data sets that contain detection limit values next to normal measured values, the so called problem of missing data will be discussed. Some suggestions to deal with this frequently occurring situation will be given

Colloidal silver nanoparticles prepared by UV-light induced citrate reduction technique for the quantitative detection of uric acid

Science.gov (United States)

Maity, Anupam; Panda, Sovan Kumar

2018-04-01

Reddish-yellow color colloid consisting of silver nanoparticles (Ag NPs) has been synthesized by reducing aqueous AgNO3 solution by photo-induced citrate reduction technique under UV light. As prepared colloid exhibits single and intense plasmonic absorption peak in the violet region of the visible spectra with the peak centered at 405 nm. The NPs are fine and spherical with diameter ranging from 5 to 10 nm. These colloidal NPs have been used for the quantitative detection of uric acid by UV-VIS spectroscopy. A linear red shifting of the characteristics Plasmonic absorption peak of Ag NPs is observed with uric acid concentration. Uric acid can be detected by UV-VIS spectroscopy down to 5 nM limit using the prepared colloid.

Limits of qualitative detection and quantitative determination

International Nuclear Information System (INIS)

Curie, L.A.

1976-01-01

The fact that one can find a series of disagreeing and limiting definitions of the detection limit leads to the reinvestigation of the problems of signal detection and signal processing in analytical and nuclear chemistry. Three cut-off levels were fixed: Lsub(C) - the net signal level (sensitivity of the equipment), above which an observed signal can be reliably recognized as 'detected'; Lsub(D) - the 'true' net signal level, from which one can a priori expect a detection; Lsub(Q) - the level at which the measuring accuracy is sufficient for quantitative determination. Exact definition equations as well as a series of working formulae are given for the general analytical case and for the investigation of radioactivity. As it is assumed that the radioactivity of the Poisson distribution is determined, it is dealt with in such a manner that precise limits can be derived for short-lived and long-lived radionuclides with or without disturbance. The fundamentals are made clear by simple examples for spectrophotometry and radioactivity and by a complicated example for activation analysis in which one must choose between alternative nuclear reactions. (orig./LH) [de

Combining Electrochemical Sensors with Miniaturized Sample Preparation for Rapid Detection in Clinical Samples

Science.gov (United States)

Bunyakul, Natinan; Baeumner, Antje J.

2015-01-01

Clinical analyses benefit world-wide from rapid and reliable diagnostics tests. New tests are sought with greatest demand not only for new analytes, but also to reduce costs, complexity and lengthy analysis times of current techniques. Among the myriad of possibilities available today to develop new test systems, amperometric biosensors are prominent players—best represented by the ubiquitous amperometric-based glucose sensors. Electrochemical approaches in general require little and often enough only simple hardware components, are rugged and yet provide low limits of detection. They thus offer many of the desirable attributes for point-of-care/point-of-need tests. This review focuses on investigating the important integration of sample preparation with (primarily electrochemical) biosensors. Sample clean up requirements, miniaturized sample preparation strategies, and their potential integration with sensors will be discussed, focusing on clinical sample analyses. PMID:25558994

On the lower of limit detection of radiometric systems

International Nuclear Information System (INIS)

Kamburov, H.; Boneva, S.

1983-01-01

The existing definitions of the quantity Asub(min), the lower detection limit, introduced as a characteristic of the sensitivity of radiometric systems are reviewed. A convenient way is found for comparing the different definitions by showing that each definition is connected with a specific value of the probability a of Type I error. The detection limits are calculated for a normal and Poisson distributions of the measured quantities. A criterion is proposed for the applicability of the normal distiribution to the problem of determining the lower detection limit

Determination of detection limits for a VPD ICPMS method of analysis; Determination des limites de detection d'une methode d'analyse VPD ICPMS

Energy Technology Data Exchange (ETDEWEB)

Badard, M.; Veillerot, M

2007-07-01

This training course report presents the different methods of detection and quantifying of metallic impurities in semiconductors. One of the most precise technique is the collection of metal impurities by vapor phase decomposition (VPD) followed by their analysis by ICPMS (inductively coupled plasma mass spectrometry). The study shows the importance of detection limits in the domain of chemical analysis and the way to determine them for the ICPMS analysis. The results found on detection limits are excellent. Even if the detection limits reached with ICPMS performed after manual or automatic VPD are much higher than detection limits of ICPMS alone, this method remains one of the most sensible for ultra-traces analysis. (J.S.)

Limits of Tumor Detectability in Nuclear Medicine and PET

Directory of Open Access Journals (Sweden)

Yusuf Emre Erdi

2012-04-01

Full Text Available Objective: Nuclear medicine is becoming increasingly important in the early detection of malignancy. The advantage of nuclear medicine over other imaging modalities is the high sensitivity of the gamma camera. Nuclear medicine counting equipment has the capability of detecting levels of radioactivity which exceed background levels by as little as 2.4 to 1. This translates to only a few hundred counts per minute on a regular gamma camera or as few as 3 counts per minute when using coincidence detection on a positron emission tomography (PET camera. Material and Methods: We have experimentally measured the limits of detectability using a set of hollow spheres in a Jaszczak phantom at various tumor-to-background ratios. Imaging modalities for this work were (1 planar, (2 SPECT, (3 PET, and (4 planar camera with coincidence detection capability (MCD. Results: When there is no background (infinite contrast activity present, the detectability of tumors is similar for PET and planar imaging. With the presence of the background activity , PET can detect objects in an order of magnitude smaller in size than that can be seen by conventional planar imaging especially in the typical clinical low (3:1 T/B ratios. The detection capability of the MCD camera lies between a conventional nuclear medicine (planar / SPECT scans and the detection capability of a dedicated PET scanner Conclusion: Among nuclear medicine’s armamentarium, PET is the closest modality to CT or MR imaging in terms of limits of detection. Modern clinical PET scanners have a resolution limit of 4 mm, corresponding to the detection of tumors with a volume of 0.2 ml (7 mm diameter in 5:1 T/B ratio. It is also possible to obtain better resolution limits with dedicated brain and animal scanners. The future holds promise in development of new detector materials, improved camera design, and new reconstruction algorithms which will improve sensitivity, resolution, contrast, and thereby further

Global Health: Preparation for Working in Resource-Limited Settings.

Science.gov (United States)

St Clair, Nicole E; Pitt, Michael B; Bakeera-Kitaka, Sabrina; McCall, Natalie; Lukolyo, Heather; Arnold, Linda D; Audcent, Tobey; Batra, Maneesh; Chan, Kevin; Jacquet, Gabrielle A; Schutze, Gordon E; Butteris, Sabrina

2017-11-01

Trainees and clinicians from high-income countries are increasingly engaging in global health (GH) efforts, particularly in resource-limited settings. Concomitantly, there is a growing demand for these individuals to be better prepared for the common challenges and controversies inherent in GH work. This is a state-of-the-art review article in which we outline what is known about the current scope of trainee and clinician involvement in GH experiences, highlight specific considerations and issues pertinent to GH engagement, and summarize preparation recommendations that have emerged from the literature. The article is focused primarily on short-term GH experiences, although much of the content is also pertinent to long-term work. Suggestions are made for the health care community to develop and implement widely endorsed preparation standards for trainees, clinicians, and organizations engaging in GH experiences and partnerships. Copyright © 2017 by the American Academy of Pediatrics.

Search times and probability of detection in time-limited search

Science.gov (United States)

Wilson, David; Devitt, Nicole; Maurer, Tana

2005-05-01

When modeling the search and target acquisition process, probability of detection as a function of time is important to war games and physical entity simulations. Recent US Army RDECOM CERDEC Night Vision and Electronics Sensor Directorate modeling of search and detection has focused on time-limited search. Developing the relationship between detection probability and time of search as a differential equation is explored. One of the parameters in the current formula for probability of detection in time-limited search corresponds to the mean time to detect in time-unlimited search. However, the mean time to detect in time-limited search is shorter than the mean time to detect in time-unlimited search and the relationship between them is a mathematical relationship between these two mean times. This simple relationship is derived.

Methodologies for the practical determination and use of method detection limits

International Nuclear Information System (INIS)

Rucker, T.L.

1995-01-01

Method detection limits have often been misunderstood and misused. The basic definitions developed by Lloyd Currie and others have been combined with assumptions that are inappropriate for many types of radiochemical analyses. A partical way for determining detection limits based on Currie's basic definition is presented that removes the reliance on assumptions and that accounts for the total measurement uncertainty. Examples of proper and improper use of detection limits are also presented, including detection limits reported by commercial software for gamma spectroscopy and neutron activation analyses. (author) 6 refs.; 2 figs

No evidence for an item limit in change detection.

Directory of Open Access Journals (Sweden)

Shaiyan Keshvari

Full Text Available Change detection is a classic paradigm that has been used for decades to argue that working memory can hold no more than a fixed number of items ("item-limit models". Recent findings force us to consider the alternative view that working memory is limited by the precision in stimulus encoding, with mean precision decreasing with increasing set size ("continuous-resource models". Most previous studies that used the change detection paradigm have ignored effects of limited encoding precision by using highly discriminable stimuli and only large changes. We conducted two change detection experiments (orientation and color in which change magnitudes were drawn from a wide range, including small changes. In a rigorous comparison of five models, we found no evidence of an item limit. Instead, human change detection performance was best explained by a continuous-resource model in which encoding precision is variable across items and trials even at a given set size. This model accounts for comparison errors in a principled, probabilistic manner. Our findings sharply challenge the theoretical basis for most neural studies of working memory capacity.

Determination of detection limits for a VPD ICPMS method of analysis

International Nuclear Information System (INIS)

Badard, M.; Veillerot, M.

2007-01-01

This training course report presents the different methods of detection and quantifying of metallic impurities in semiconductors. One of the most precise technique is the collection of metal impurities by vapor phase decomposition (VPD) followed by their analysis by ICPMS (inductively coupled plasma mass spectrometry). The study shows the importance of detection limits in the domain of chemical analysis and the way to determine them for the ICPMS analysis. The results found on detection limits are excellent. Even if the detection limits reached with ICPMS performed after manual or automatic VPD are much higher than detection limits of ICPMS alone, this method remains one of the most sensible for ultra-traces analysis. (J.S.)

CT colonography with limited bowel preparation: prospective assessment of patient experience and preference in comparison to optical colonoscopy with cathartic bowel preparation

International Nuclear Information System (INIS)

Jensch, Sebastiaan; Bipat, Shandra; Vries, Ayso H. de; Heutinck, Anneke; Stoker, Jaap; Peringa, Jan; Montauban van Swijndregt, Alexander D.; Dekker, Evelien; Baak, Lubbertus C.

2010-01-01

The purpose of this study was to prospectively compare participant experience and preference of limited preparation computed tomography colonography (CTC) with full-preparation colonoscopy in a consecutive series of patients at increased risk of colorectal cancer. CTC preparation comprised 180 ml diatrizoate meglumine, 80 ml barium and 30 mg bisacodyl. For the colonoscopy preparation 4 l of polyethylene glycol solution was used. Participants' experience and preference were compared using the Wilcoxon signed rank test and the chi-squared test, respectively. Associations between preference and experience parameters for the 173 participants were determined by logistic regression. Diarrhoea occurred in 94% of participants during CTC preparation. This side effect was perceived as severely or extremely burdensome by 29%. Nonetheless, the total burden was significantly lower for the CTC preparation than for colonoscopy (9% rated the CTC preparation as severely or extremely burdensome compared with 59% for colonoscopy; p<0.001). Participants experienced significantly more pain, discomfort and total burden with the colonoscopy procedure than with CTC (p<0.001). After 5 weeks, 69% preferred CTC, 8% were indifferent and 23% preferred colonoscopy (p<0.001). A burdensome colonoscopy preparation and pain at colonoscopy were associated with CTC preference (p<0.04). In conclusion, participants' experience and preference were rated in favour of CTC with limited bowel preparation compared with full-preparation colonoscopy. (orig.)

Importance of the lower limit of detection in radiological safety

International Nuclear Information System (INIS)

Rafael Terol T.; Hermenegildo Maldonado M.

1991-01-01

The concept of the Lower Limit of Detection (LLD) it contributes in the solution of some problems related with the radiological safety, such as the realization of the tests of flight of the sealed radioactive sources; the determination of radioisotopes in environmental samples; the estimate of present radionuclides in polluted foods; in general, the detection of small quantities of radioactive materials present in materials of use or consumption by part of the man in his daily life; as the one Lower Limit of Detection is related with topics of statistics, in this work a small review of them is made, it was superficially discussed the mensuration problems related with the establishment of the Lower Limit of Detection

Confirmation of identity and detection limit in neutron activation analysis

International Nuclear Information System (INIS)

Yustina Tri Handayani; Slamet Wiyuniati; Tulisna

2010-01-01

Neutron Activation Analysis (NAA) based on neutron capture by nuclides. Of the various possibilities of radionuclides that occur, radionuclides and gamma radiation which provides the identity of the element were analyzed and the best sensitivity should be determined. Confirmation for elements in sediment samples was done theoretically and experimentally. The result of confirmation shows that Al, V, Cr K, Na, Ca and Zn were analyzed based on radionuclides of Al-28, V-52, Cr-51 , K-42, Na-24, Ca-48, Zn-65. Elements of Mg, Mn, Fe, Co were analyzed based on radionuclides of Mg-27, Mn-56, Fe-59, Co-60 through peak which the highest value of combined probability of radiation emission and efficiency. Cu can be analyzed through Cu-64 or Cu-66, but the second is more sensitive. Detection limit is determined at a certain measurement conditions carried out by a laboratory. Detection limit in the NAA is determined based on the Compton continue area by Curie method. The detection limit of Al, V, Ca, Mg, Mn, As, K, Na, Mg, Ce, Co, Cr, Fe, La, Sc, and Zn in sediment samples are 240, 27, 4750, 2600, 21, 3.3 , 75, 1.4, 1.8, 0.5, 2.7, 29, 1, 0.05, and 37 ppm. Analysis of Cu in sediments which concentrations of 98.6 ppm, Cu-66 is not detected. Tests using pure standard solutions of Cu obtained detection limit of 0.12 µg, or 7.9 ppm in samples of 15 mg. In general, the detection limit obtained was higher than the detection limit of the reference, it was caused by the differences in the sample matrix and analytical conditions. (author)

Lower detectable limit of sulfur by fast neutron activation analysis

Energy Technology Data Exchange (ETDEWEB)

Shani, G; Cohen, D [Ben-Gurion Univ. of the Negev, Beersheba (Israel). Dept. of Nuclear Engineering

1976-07-01

For the purpose of air pollution research, the possibility of fast neutron activation analysis of sulfur was investigated. The only reaction that can be used for this purpose is S/sup 34/(n, p)P/sup 34/. A rabbit system was installed, synchronized with a 150 kV D-T neutron generator and an electronic analysing system. The whole system was operated so that the sample was irradiated for 10 sec and the 2.13 MeV ..gamma..-ray was counted for 10 sec. 5 samples were prepared containing sulfur from 0.5 to 0.1 g. Each measurement lasted 30 min and the activity was plotted as a function of sulfur weight. The relative error is increased very much when the amount of sulfur is below 0.1 g. This is what sets the lower detectable limit. Collection of more than 0.1 g of sulfur even during a long collection time means a very high SO/sub 2/ concentration in the air.

Sample Preparation for Electron Probe Microanalysis-Pushing the Limits.

Science.gov (United States)

Geller, Joseph D; Engle, Paul D

2002-01-01

important, and, under certain conditions, may even be the limiting factor in the analytical uncertainty budget. This paper considers preparing samples to get known geometries. It will not address the analysis of samples with irregular, unprepared surfaces or unknown geometries.

Stochastic fluctuations and the detectability limit of network communities.

Science.gov (United States)

Floretta, Lucio; Liechti, Jonas; Flammini, Alessandro; De Los Rios, Paolo

2013-12-01

We have analyzed the detectability limits of network communities in the framework of the popular Girvan and Newman benchmark. By carefully taking into account the inevitable stochastic fluctuations that affect the construction of each and every instance of the benchmark, we come to the conclusion that the native, putative partition of the network is completely lost even before the in-degree/out-degree ratio becomes equal to that of a structureless Erdös-Rényi network. We develop a simple iterative scheme, analytically well described by an infinite branching process, to provide an estimate of the true detectability limit. Using various algorithms based on modularity optimization, we show that all of them behave (semiquantitatively) in the same way, with the same functional form of the detectability threshold as a function of the network parameters. Because the same behavior has also been found by further modularity-optimization methods and for methods based on different heuristics implementations, we conclude that indeed a correct definition of the detectability limit must take into account the stochastic fluctuations of the network construction.

Pushing the limits of NAA. Accuracy, uncertainty and detection limits

International Nuclear Information System (INIS)

Greenberg, R.R.

2008-01-01

This paper describes some highlights from the author's efforts to improve neutron activation analysis (NAA) detection limits through development and optimization of radiochemical separations, as well as to improve the overall accuracy of NAA measurements by identifying, quantifying and reducing measurement biases and uncertainties. Efforts to demonstrate the metrological basis of NAA, and to establish it as a 'Primary Method of Measurement' will be discussed. (author)

Electronic cleansing for 24-h limited bowel preparation CT colonography using principal curvature flow

NARCIS (Netherlands)

van Ravesteijn, Vincent F.; Boellaard, Thierry N.; van der Paardt, Marije P.; Serlie, Iwo W. O.; de Haan, Margriet C.; Stoker, Jaap; van Vliet, Lucas J.; Vos, Frans M.

2013-01-01

CT colonography (CTC) is one of the recommended methods for colorectal cancer screening. The subject's preparation is one of the most burdensome aspects of CTC with a cathartic bowel preparation. Tagging of the bowel content with an oral contrast medium facilitates CTC with limited bowel

Preparation of three-dimensionally ordered macroporous polycysteine film and application in sensitive detection of 4-chlorophenol

International Nuclear Information System (INIS)

Zhang, Shenghui; Shi, Zhen; Wang, Jinshou; Cheng, Qin; Wu, Kangbing

2014-01-01

Highlights: • Polycysteine film with three-dimensionally ordered porous structures was prepared. • 3-DOM polycysteine film exhibited large active area and signal enhancement effects. • 3-DOM polycysteine film increased oxidation signal of 4-chlorophenol by 5-fold. - Abstract: Polystyrene microspheres with diameter of 350 nm were prepared, and then used to arrange on the surface of glassy carbon electrode (GCE) as structure-directing template. By successive cyclic sweeps between −1.0 V and 2.0 V in pH 7 phosphate buffer containing 10 mM cysteine, polycysteine film was electrodeposited on polystyrene microspheres-arranged GCE. After removing polystyrene template, a three-dimensionally ordered macroporous (3-DOM) polycysteine film was achieved, as confirmed by scanning electron microscopy measurements. Electrochemical responses of K 3 [Fe(CN) 6 ] probe indicated that 3-DOM polycysteine film-modified GCE exhibited larger active area, compared with GCE, polycysteine film-modified GCE and electrochemically oxidized GCE. The application of 3-DOM polycysteine film in electrochemical detection of 4-chlorophenol was studied. Due to ordered porous structures, the 3-DOM polycysteine film-modified GCE displayed signal enhancement effects, and enhanced the oxidation peak currents of 4-chlorophenol. As a result, a sensitive electrochemical method was developed for the detection of 4-chlorophenol, and the detection limit was 1.67 × 10 −8 M. This new method was used to detect 4-chlorophenol in water samples, and the value of recovery was over the range from 99.6% to 107%

DETERMINATION OF LIMIT DETECTION OF THE ELEMENTS N, P, K, Si, Al, Fe, Cu, Cd, WITH FAST NEUTRON ACTIVATION USING NEUTRON GENERATOR

Directory of Open Access Journals (Sweden)

Sunardi Sunardi

2010-06-01

Full Text Available Determination of limit detection of the elements N, P, K, Si, Al, Fe, Cu, Cd, with fast neutron activation using neutron generator has been done.  Samples prepared from SRM 2704, N, P, K elements from MERCK, Cu, Cd, Al from activation foil made in San Carlos, weighted and packed for certain weight then iradiated during 30 minutes with 14 MeV fast neutron using the neutron generator and then counted with gamma spectrometry (accuspec.  At this research condition of neutron generator was set at current 1 mA that produced neutron flux about 5,47.107 n/cm2.s and  experimental result shown that the limit detection for the elements N, P, K, Si, Al, Fe, Cu, Cd are  2,44 ppm, 1,88 ppm, 2,15 ppm, 1,44 ppm, 1,26 ppm, 1,35 ppm, 1,05 ppm, 2,99 ppm, respectively.  The data  indicate that the limit detection or sensitivity of appliance of neutron generator to analyze the element is very good, which is feasible to get accreditation AANC laboratory using neutron generator.   Keywords: limit detection, AANC, neutron generator

Miniaturized Sample Preparation and Rapid Detection of Arsenite in Contaminated Soil Using a Smartphone

Directory of Open Access Journals (Sweden)

Mohd Farhan Siddiqui

2018-03-01

Full Text Available Conventional methods for analyzing heavy metal contamination in soil and water generally require laboratory equipped instruments, complex procedures, skilled personnel and a significant amount of time. With the advancement in computing and multitasking performances, smartphone-based sensors potentially allow the transition of the laboratory-based analytical processes to field applicable, simple methods. In the present work, we demonstrate the novel miniaturized setup for simultaneous sample preparation and smartphone-based optical sensing of arsenic As(III in the contaminated soil. Colorimetric detection protocol utilizing aptamers, gold nanoparticles and NaCl have been optimized and tested on the PDMS-chip to obtain the high sensitivity with the limit of detection of 0.71 ppm (in the sample and a correlation coefficient of 0.98. The performance of the device is further demonstrated through the comparative analysis of arsenic-spiked soil samples with standard laboratory method, and a good agreement with a correlation coefficient of 0.9917 and the average difference of 0.37 ppm, are experimentally achieved. With the android application on the device to run the experiment, the whole process from sample preparation to detection is completed within 3 hours without the necessity of skilled personnel. The approximate cost of setup is estimated around 1 USD, weight 55 g. Therefore, the presented method offers the simple, rapid, portable and cost-effective means for onsite sensing of arsenic in soil. Combined with the geometric information inside the smartphones, the system will allow the monitoring of the contamination status of soils in a nation-wide manner.

Miniaturized Sample Preparation and Rapid Detection of Arsenite in Contaminated Soil Using a Smartphone.

Science.gov (United States)

Siddiqui, Mohd Farhan; Kim, Soocheol; Jeon, Hyoil; Kim, Taeho; Joo, Chulmin; Park, Seungkyung

2018-03-04

Conventional methods for analyzing heavy metal contamination in soil and water generally require laboratory equipped instruments, complex procedures, skilled personnel and a significant amount of time. With the advancement in computing and multitasking performances, smartphone-based sensors potentially allow the transition of the laboratory-based analytical processes to field applicable, simple methods. In the present work, we demonstrate the novel miniaturized setup for simultaneous sample preparation and smartphone-based optical sensing of arsenic As(III) in the contaminated soil. Colorimetric detection protocol utilizing aptamers, gold nanoparticles and NaCl have been optimized and tested on the PDMS-chip to obtain the high sensitivity with the limit of detection of 0.71 ppm (in the sample) and a correlation coefficient of 0.98. The performance of the device is further demonstrated through the comparative analysis of arsenic-spiked soil samples with standard laboratory method, and a good agreement with a correlation coefficient of 0.9917 and the average difference of 0.37 ppm, are experimentally achieved. With the android application on the device to run the experiment, the whole process from sample preparation to detection is completed within 3 hours without the necessity of skilled personnel. The approximate cost of setup is estimated around 1 USD, weight 55 g. Therefore, the presented method offers the simple, rapid, portable and cost-effective means for onsite sensing of arsenic in soil. Combined with the geometric information inside the smartphones, the system will allow the monitoring of the contamination status of soils in a nation-wide manner.

Preparation of conjugated poly(ethyl acetylene carboxylate) as optical limiter of laser radiation

International Nuclear Information System (INIS)

Allaf, A. W.; Al-Zier, A.; Al-Naima, D.

2009-03-01

The optical limiting action of poly (ethylacetylene carboxylate) dissolved in dichloroethane were investigated under irradiation with 8 ns laser pulses at 532 nm. The optical limiting measurements were performed at a series of concentrations. The threshold limiting fluence was observed for high concentrations at 5 J/cm 2 with a transmission of about 20 %. No optical limiting action was observed at very low concentration of the prepared polymer in the dichloroethane solvent. The observed data show that poly (ethylacetylene carboxylate) has the potential for the use as optical limiting material for future applications. (author)

Sample Preparation for Electron Probe Microanalysis—Pushing the Limits

Science.gov (United States)

Geller, Joseph D.; Engle, Paul D.

2002-01-01

important, and, under certain conditions, may even be the limiting factor in the analytical uncertainty budget. This paper considers preparing samples to get known geometries. It will not address the analysis of samples with irregular, unprepared surfaces or unknown geometries. PMID:27446757

Detection of colloidal silver chloride near solubility limit

Science.gov (United States)

Putri, K. Y.; Adawiah, R.

2018-03-01

Detection of nanoparticles in solution has been made possible by several means; one of them is laser-induced breakdown detection (LIBD). LIBD is able to distinguish colloids of various sizes and concentrations. This technique has been used in several solubility studies. In this study, the formation of colloids in a mixed system of silver nitrate and sodium chloride was observed by acoustic LIBD. Silver chloride has low solubility limit, therefore LIBD measurement is appropriate. Silver and chloride solutions with equal concentrations, set at below and above the solubility of silver chloride as the expected solid product, were mixed and the resulting colloids were observed. The result of LIBD measurement showed that larger particles were present as more silver and chloride introduced. However, once the concentrations exceeded the solubility limit of silver chloride, the detected particle size seemed to be decreasing, hence suggested the occurrence of coprecipitation process. This phenomenon indicated that the ability of LIBD to detect even small changes in colloid amounts might be a useful tool in study on formation and stability of colloids, i.e. to confirm whether nanoparticles synthesis has been successfully performed and whether the system is stable or not.

Impact of sensor detection limits on protecting water distribution systems from contamination events

International Nuclear Information System (INIS)

McKenna, Sean Andrew; Hart, David Blaine; Yarrington, Lane

2006-01-01

Real-time water quality sensors are becoming commonplace in water distribution systems. However, field deployable, contaminant-specific sensors are still in the development stage. As development proceeds, the necessary operating parameters of these sensors must be determined to protect consumers from accidental and malevolent contamination events. This objective can be quantified in several different ways including minimization of: the time necessary to detect a contamination event, the population exposed to contaminated water, the extent of the contamination within the network, and others. We examine the ability of a sensor set to meet these objectives as a function of both the detection limit of the sensors and the number of sensors in the network. A moderately sized distribution network is used as an example and different sized sets of randomly placed sensors are considered. For each combination of a certain number of sensors and a detection limit, the mean values of the different objectives across multiple random sensor placements are calculated. The tradeoff between the necessary detection limit in a sensor and the number of sensors is evaluated. Results show that for the example problem examined here, a sensor detection limit of 0.01 of the average source concentration is adequate for maximum protection. Detection of events is dependent on the detection limit of the sensors, but for those events that are detected, the values of the performance measures are not a function of the sensor detection limit. The results of replacing a single sensor in a network with a sensor having a much lower detection limit show that while this replacement can improve results, the majority of the additional events detected had performance measures of relatively low consequence.

Censoring approach to the detection limits in X-ray fluorescence analysis

International Nuclear Information System (INIS)

Pajek, M.; Kubala-Kukus, A.

2004-01-01

We demonstrate that the effect of detection limits in the X-ray fluorescence analysis (XRF), which limits the determination of very low concentrations of trace elements and results in appearance of the so-called 'nondetects', can be accounted for using the statistical concept of censoring. More precisely, the results of such measurements can be viewed as the left random censored data, which can further be analyzed using the Kaplan-Meier method correcting the data for the presence of nondetects. Using this approach, the results of measured, detection limit censored concentrations can be interpreted in a nonparametric manner including the correction for the nondetects, i.e. the measurements in which the concentrations were found to be below the actual detection limits. Moreover, using the Monte Carlo simulation technique we show that by using the Kaplan-Meier approach the corrected mean concentrations for a population of the samples can be estimated within a few percent uncertainties with respect of the simulated, uncensored data. This practically means that the final uncertainties of estimated mean values are limited in fact by the number of studied samples and not by the correction procedure itself. The discussed random-left censoring approach was applied to analyze the XRF detection-limit-censored concentration measurements of trace elements in biomedical samples

Importance of the lower limit of detection in radiological safety; Importancia del limite inferior de deteccion en seguridad radiologica

Energy Technology Data Exchange (ETDEWEB)

Rafael, Terol T; Hermenegildo, Maldonado M [Comision Nacional de Seguridad Nuclear y Salvaguardias (Mexico)

1991-07-01

The concept of the Lower Limit of Detection (LLD) it contributes in the solution of some problems related with the radiological safety, such as the realization of the tests of flight of the sealed radioactive sources; the determination of radioisotopes in environmental samples; the estimate of present radionuclides in polluted foods; in general, the detection of small quantities of radioactive materials present in materials of use or consumption by part of the man in his daily life; as the one Lower Limit of Detection is related with topics of statistics, in this work a small review of them is made, it was superficially discussed the mensuration problems related with the establishment of the Lower Limit of Detection.

Errors detected in pediatric oral liquid medication doses prepared in an automated workflow management system.

Science.gov (United States)

Bledsoe, Sarah; Van Buskirk, Alex; Falconer, R James; Hollon, Andrew; Hoebing, Wendy; Jokic, Sladan

2018-02-01

The effectiveness of barcode-assisted medication preparation (BCMP) technology on detecting oral liquid dose preparation errors. From June 1, 2013, through May 31, 2014, a total of 178,344 oral doses were processed at Children's Mercy, a 301-bed pediatric hospital, through an automated workflow management system. Doses containing errors detected by the system's barcode scanning system or classified as rejected by the pharmacist were further reviewed. Errors intercepted by the barcode-scanning system were classified as (1) expired product, (2) incorrect drug, (3) incorrect concentration, and (4) technological error. Pharmacist-rejected doses were categorized into 6 categories based on the root cause of the preparation error: (1) expired product, (2) incorrect concentration, (3) incorrect drug, (4) incorrect volume, (5) preparation error, and (6) other. Of the 178,344 doses examined, 3,812 (2.1%) errors were detected by either the barcode-assisted scanning system (1.8%, n = 3,291) or a pharmacist (0.3%, n = 521). The 3,291 errors prevented by the barcode-assisted system were classified most commonly as technological error and incorrect drug, followed by incorrect concentration and expired product. Errors detected by pharmacists were also analyzed. These 521 errors were most often classified as incorrect volume, preparation error, expired product, other, incorrect drug, and incorrect concentration. BCMP technology detected errors in 1.8% of pediatric oral liquid medication doses prepared in an automated workflow management system, with errors being most commonly attributed to technological problems or incorrect drugs. Pharmacists rejected an additional 0.3% of studied doses. Copyright © 2018 by the American Society of Health-System Pharmacists, Inc. All rights reserved.

Calculation of the detection limit in radiation measurements with systematic uncertainties

International Nuclear Information System (INIS)

Kirkpatrick, J.M.; Russ, W.; Venkataraman, R.; Young, B.M.

2015-01-01

The detection limit (L D ) or Minimum Detectable Activity (MDA) is an a priori evaluation of assay sensitivity intended to quantify the suitability of an instrument or measurement arrangement for the needs of a given application. Traditional approaches as pioneered by Currie rely on Gaussian approximations to yield simple, closed-form solutions, and neglect the effects of systematic uncertainties in the instrument calibration. These approximations are applicable over a wide range of applications, but are of limited use in low-count applications, when high confidence values are required, or when systematic uncertainties are significant. One proposed modification to the Currie formulation attempts account for systematic uncertainties within a Gaussian framework. We have previously shown that this approach results in an approximation formula that works best only for small values of the relative systematic uncertainty, for which the modification of Currie's method is the least necessary, and that it significantly overestimates the detection limit or gives infinite or otherwise non-physical results for larger systematic uncertainties where such a correction would be the most useful. We have developed an alternative approach for calculating detection limits based on realistic statistical modeling of the counting distributions which accurately represents statistical and systematic uncertainties. Instead of a closed form solution, numerical and iterative methods are used to evaluate the result. Accurate detection limits can be obtained by this method for the general case

Preparation of Dithizone Functionalized Polystyrene for Detecting Heavy Metal Ion

Energy Technology Data Exchange (ETDEWEB)

Shin, Hyeon Ho; Kim, Younghun [Kwangwoon University, Seoul (Korea, Republic of)

2015-04-15

Colorimetric sensors were usually used to detect specific metal ions using selective color change of solutions. While almost organic dye in colorimetric sensors detected single molecule, dithizone (DTZ) solution could be separately detected above 5 kinds of heavy metal ions by the change of clear color. Namely, DTZ could be used as multicolorimetric sensors. However, DTZ was generally used as aqueous type and paper/pellet-type DTZ was not reported yet. Therefore, in this work, polystyrene (PS) was prepared to composite with DTZ and then DTZ/PS pellet was obtained, which was used to selectively detect 10 kinds of heavy metal ions. When 10 ppm of Hg and Co ions was exposed in DTZ/PS pellets, clear color change was revealed. It is noted that DTZ/PS pellet could be used in detecting of heavy metal ion as dry type.

Preparation of ultra-thin polypyrrole nanosheets decorated with Ag nanoparticles and their application in hydrogen peroxide detection

International Nuclear Information System (INIS)

Mahmoudian, M.R.; Alias, Y.; Basirun, W.J.; Ebadi, M.

2012-01-01

Highlights: ► Ag nanoparticles-decorated ultra thin polypyrrole nanosheets were prepared. ► Higher surface area of the polymer increased interaction between the polymer and Ag + . ► The sensitivity was estimated to be 4.477 μA mM −1 for linear segment. ► The LOD and LOQ (S/N = 3) were estimated to be 0.57 μM and 1.93 μM, respectively. - Abstract: This study examines the preparation of ultra-thin polypyrrole nanosheets decorated with Ag nanoparticles (Ag-UTPNSs) and their application in the enzyme-less detection of hydrogen peroxide (H 2 O 2 ) detection. The X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) results confirmed that Ag nanoparticles (NPs) were deposited onto the surface of the UTPNSs. The increase of the H 2 O 2 reduction current peak to 120 μA in the presence of the Ag-UTPNS/glassy carbon electrode (GCE) as compared to the UTPNS/GCE indicates that the sensitivity of the electrode to H 2 O 2 is significant. This observation can be explained by the larger surface area of the UTPNSs, which can increase the interactions between the polymer and the AgNO 3 solution during the deposition of the Ag NPs, and by the small size of the deposited Ag NPs, which can produce a surface area of Ag that is suitable for the reaction with H 2 O 2 . The amperometric responses show that the limit of detection, the limit of quantification (S/N = 3) and the sensitivity are estimated to be 0.57 μM, 1.93 μM and 4.477 μA mM −1 , respectively, for the linear segment. The results of the reproducibility experiments show that the use of Ag-UTPNS/GCE is feasible for the quantitative detection of certain concentration ranges of H 2 O 2 .

Detection limits of antimicrobials in ewe milk by delvotest photometric measurements.

Science.gov (United States)

Althaus, R L; Torres, A; Montero, A; Balasch, S; Molina, M P

2003-02-01

The Delvotest method detection limits per manufacturer's instructions at a fixed reading time of 3 h for 24 antimicrobial agents were determined in ewe milk by photometric measurement. For each drug, eight concentrations were tested on 20 ewe milk samples from individual ewes. Detection limits, determined by means of logistic regression models, were (microg/kg): 3, amoxycillin; 2, ampicillin; 18, cloxacillin; 1, penicillin "G"; 34, cefadroxil; 430, cephalosporin "C"; 40, cephalexin; 20, cefoperazone; 33, Ceftiofur; 18, cefuroxime; 6100, streptomycin; 1200, gentamycin; 2600, neomycin; 830, erythromycin; 100, tylosin; 180, doxycycline; 320, oxytetracycline; 590, tetracycline; 88, sulfadiazine; 44, sulfamethoxazole; 140, sulfametoxypyridazine; 48, sulfaquinoxaline; 12,000, chloramphenicol; and 290, trimethoprim. Whereas the beta-lactam antibiotics, sulphonamides, and tylosin were detected by Delvotest method at levels equal to those of maximum residue limits, its sensitivity needs to be enhanced to detect aminoglycosides, tetracyclines, streptomycin, chloramphenicol, and trimethoprim residues in ewe milk or to develop an integrated residue detection system for ewe milk with different sensitive microorganisms for each group of antiinfectious agents.

Limiter discriminator detection of M-ary FSK signals

Science.gov (United States)

Fonseka, John P.

1990-10-01

The performance of limiter discriminator detection of M-ary FSK signals is analyzed at arbitrary modulation indices. It is shown that the error rate performance of limiter discriminator detection can be significantly improved by increasing the modulation index above 1/M. The optimum modulation index that minimizes the overall error probability is determined for the cases M = 2, 4 and 8. The analysis is carried out for wideband and bandlimited channels with Gaussian and second-order Butterworth filters. It is shown that the optimum modulation index depends on the signal/noise ratio (SNR), in a wideband channel, and on both SNR and time-bandwidth product in a bandlimited channel. Finally, it is shown that the optimum sampling instance in presence of a nonzero phase IF filter can be approximately determined by using only the worst case symbol pattern.

Realistic limitations of detecting planets around young active stars

Directory of Open Access Journals (Sweden)

Pinfield D.

2013-04-01

Full Text Available Current planet hunting methods using the radial velocity method are limited to observing middle-aged main-sequence stars where the signatures of stellar activity are much less than on young stars that have just arrived on the main-sequence. In this work we apply our knowledge from the surface imaging of these young stars to place realistic limitations on the possibility of detecting orbiting planets. In general we find that the magnitude of the stellar jitter is directly proportional to the stellar vsini. For G and K dwarfs, we find that it is possible, for models with high stellar activity and low stellar vsini, to be able to detect a 1 MJupiter mass planet within 50 epochs of observations and for the M dwarfs it is possible to detect a habitable zone Earth-like planet in 10s of observational epochs.

One-step preparation of silver–polyaniline nanotube composite for non-enzymatic hydrogen peroxide detection

Energy Technology Data Exchange (ETDEWEB)

Lorestani, Farnaz, E-mail: Farnaz.lorestani@siswa.um.edu.my; Shahnavaz, Zohreh; Nia, Pooria Moozarm; Alias, Y.; Manan, Ninie S.A., E-mail: niniemanan@um.edu.my

2015-08-30

Graphical abstract: - Highlights: • Silver nanoparticle-decorated polyaniline nanotube composites (AgNPs–PANINTs) have been fabricated through a one step modified method without adding any extra acids, template and surface modifier. • The sensor showed excellent selectivity, reproducibility, and stability properties. • The AgNPs–PANINTs composite that prepared with silver ammonia solution (Ag(NH{sub 3}){sub 2}OH) exhibits better electrochemical performance than the AgNPs–PANINTs composite that was prepared with silver nitrite (AgNO{sub 3}) due to smaller size and higher surface area of silver nanoparticle (AgNPs) in the composite. • The electrocatalytic activity for the reduction was strongly affected by the concentration of silver ammonia solution in the nanocomposites, with the best electrocatalytic activity observed for the composite of 6:1 volume ratios of PANI to Ag(NH{sub 3}){sub 2}OH (0.04 M). - Abstract: A modified glassy carbon electrode with silver nanoparticles–polyaniline nanotubes (AgNPs–PANINTs) composite is used as a non-enzymatic nanobiosensor for detecting hydrogen peroxide (H{sub 2}O{sub 2}). The electrocatalytic activity for the reduction was strongly affected by the concentration of silver ammonia solution in the nanocomposites, with the best electrocatalytic activity observed for the composite of 6:1 volume ratios of PANI to Ag(NH{sub 3}){sub 2}OH (0.04 M). Field emission scanning electron microscope images and their size distribution diagrams indicated that using the silver ammonia complex instead of silver nitrate caused uniform distribution of nanometer-sized silver nanoparticles with a narrow size distribution in the composite. The corresponding calibration curve for the current response showed a linear detection range of 0.1–90 mM (R{sup 2} = 0.9986), while the limit of detection was estimated to be 0.2 μM at the signal to noise ratio of 3.

Sandwiched gold/PNIPAm/gold microstructures for smart plasmonics application: towards the high detection limit and Raman quantitative measurements.

Science.gov (United States)

Elashnikov, R; Mares, D; Podzimek, T; Švorčík, V; Lyutakov, O

2017-08-07

A smart plasmonic sensor, comprising a layer of a stimuli-responsive polymer sandwiched between two gold layers, is reported. As a stimuli-responsive material, a monolayer of poly(N-isopropylacrylamide) (PNIPAm) crosslinked globules is used. A quasi-periodic structure of the top gold layer facilitates efficient excitation and serves as a support for plasmon excitation and propagation. The intermediate layer of PNIPAm efficiently entraps targeted molecules from solutions. The sensor structure was optimized for efficient light focusing in the "active" PNIPAm layer. The optimization was based on the time-resolved finite-element simulations, which take into account the thickness of gold layers, size of PNIPAm globules and Raman excitation wavelength (780 nm). The prepared structures were characterized using SEM, AFM, UV-Vis refractometry and goniometry. Additional AFM scans were performed in water at two temperatures corresponding to the collapsed and swollen PNIPAm states. The Raman measurements demonstrate a high detection limit and perfect reproducibility of the Raman scattering signal for the prepared sensor. In addition, the use of created SERS structures for the detection of relevant molecules in the medical, biological and safety fields was demonstrated.

Ion chromatographic analysis of high specific activity 18FDG preparations and detection of the chemical impurity 2-deoxy-2-chloro-D-glucose

International Nuclear Information System (INIS)

Alexoff, D.L.; Casati, R.; Fowler, J.S.; Wolf, A.P.; Shea, C.; Schlyer, D.J.; Chyng-Yann Shiue

1992-01-01

Because of the widespread use of 2-deoxy-2-[ 18 F]fluoro-D-glucose(FDG) prepared by the ''Julich'' method or its variants it was decided necessary to determine the major chemical impurities present in the final product. An analytical system for quantifying FDG was developed using pulsed amperometry after separation by high-performance anion exchange chromotography. With this system a heretofore unidentified impurity, 2-deoxy-2-chloro-D-glucose(C1DG) was found in our preparation and in those from other laboratories using the ''Julich'' method. C1DG arises from C1 - ion displacement during the labeling procedure where C1 - ion comes from several sources, and C1 - ion displacement from the HC1 used in the hydrolysis step. FDG mass was present in the same preparations at a level of ca 1-40 μg. Other major chemical constituents were glucose (ca 1-6 mg) and mannose (ca 10-18 μg). Glycerol, arising from sterilizing filters, was also detected in most preparations. Although C1DG is a chemical impurity which has not been detected previously in nca FDG preparations, its biochemical and pharmacological properties are similar to FDG and 2-deoxy-D-glucose. Thus it is unlikely that the presence of small quantities of C1DG found in typical FDG preparations (ca 100 μg) would have adverse pharmacological or toxicological consequences that would limit continued application of this radiopharmaceutical in basic and clinical studies. (Author)

Correction to the count-rate detection limit and sample/blank time-allocation methods

International Nuclear Information System (INIS)

Alvarez, Joseph L.

2013-01-01

A common form of count-rate detection limits contains a propagation of uncertainty error. This error originated in methods to minimize uncertainty in the subtraction of the blank counts from the gross sample counts by allocation of blank and sample counting times. Correct uncertainty propagation showed that the time allocation equations have no solution. This publication presents the correct form of count-rate detection limits. -- Highlights: •The paper demonstrated a proper method of propagating uncertainty of count rate differences. •The standard count-rate detection limits were in error. •Count-time allocation methods for minimum uncertainty were in error. •The paper presented the correct form of the count-rate detection limit. •The paper discussed the confusion between count-rate uncertainty and count uncertainty

Theoretical detection limit of PIXE analysis using 20 MeV proton beams

Science.gov (United States)

Ishii, Keizo; Hitomi, Keitaro

2018-02-01

Particle-induced X-ray emission (PIXE) analysis is usually performed using proton beams with energies in the range 2∼3 MeV because at these energies, the detection limit is low. The detection limit of PIXE analysis depends on the X-ray production cross-section, the continuous background of the PIXE spectrum and the experimental parameters such as the beam currents and the solid angle and detector efficiency of X-ray detector. Though the continuous background increases as the projectile energy increases, the cross-section of the X-ray increases as well. Therefore, the detection limit of high energy proton PIXE is not expected to increase significantly. We calculated the cross sections of continuous X-rays produced in several bremsstrahlung processes and estimated the detection limit of a 20 MeV proton PIXE analysis by modelling the Compton tail of the γ-rays produced in the nuclear reactions, and the escape effect on the secondary electron bremsstrahlung. We found that the Compton tail does not affect the detection limit when a thin X-ray detector is used, but the secondary electron bremsstrahlung escape effect does have an impact. We also confirmed that the detection limit of the PIXE analysis, when used with 4 μm polyethylene backing film and an integrated beam current of 1 μC, is 0.4∼2.0 ppm for proton energies in the range 10∼30 MeV and elements with Z = 16-90. This result demonstrates the usefulness of several 10 MeV cyclotrons for performing PIXE analysis. Cyclotrons with these properties are currently installed in positron emission tomography (PET) centers.

Sample preparation and detection device for infectious agents

Science.gov (United States)

Miles, Robin R.; Wang, Amy W.; Fuller, Christopher K.; Lemoff, Asuncion V.; Bettencourt, Kerry A.; Yu, June

2003-06-10

A sample preparation and analysis device which incorporates both immunoassays and PCR assays in one compact, field-portable microchip. The device provides new capabilities in fluid and particle control which allows the building of a fluidic chip with no moving parts, thus decreasing fabrication cost and increasing the robustness of the device. The device can operate in a true continuous (not batch) mode. The device incorporates magnetohydrodynamic (MHD) pumps to move the fluid through the system, acoustic mixing and fractionation, dielectropheretic (DEP) sample concentration and purification, and on-chip optical detection capabilities.

Censoring: a new approach for detection limits in total-reflection X-ray fluorescence

International Nuclear Information System (INIS)

Pajek, M.; Kubala-Kukus, A.; Braziewicz, J.

2004-01-01

It is shown that the detection limits in the total-reflection X-ray fluorescence (TXRF), which restrict quantification of very low concentrations of trace elements in the samples, can be accounted for using the statistical concept of censoring. We demonstrate that the incomplete TXRF measurements containing the so-called 'nondetects', i.e. the non-measured concentrations falling below the detection limits and represented by the estimated detection limit values, can be viewed as the left random-censored data, which can be further analyzed using the Kaplan-Meier (KM) method correcting for nondetects. Within this approach, which uses the Kaplan-Meier product-limit estimator to obtain the cumulative distribution function corrected for the nondetects, the mean value and median of the detection limit censored concentrations can be estimated in a non-parametric way. The Monte Carlo simulations performed show that the Kaplan-Meier approach yields highly accurate estimates for the mean and median concentrations, being within a few percent with respect to the simulated, uncensored data. This means that the uncertainties of KM estimated mean value and median are limited in fact only by the number of studied samples and not by the applied correction procedure for nondetects itself. On the other hand, it is observed that, in case when the concentration of a given element is not measured in all the samples, simple approaches to estimate a mean concentration value from the data yield erroneous, systematically biased results. The discussed random-left censoring approach was applied to analyze the TXRF detection-limit-censored concentration measurements of trace elements in biomedical samples. We emphasize that the Kaplan-Meier approach allows one to estimate the mean concentrations being substantially below the mean level of detection limits. Consequently, this approach gives a new access to lower the effective detection limits for TXRF method, which is of prime interest for

Accuracy, precision, and lower detection limits (a deficit reduction approach)

International Nuclear Information System (INIS)

Bishop, C.T.

1993-01-01

The evaluation of the accuracy, precision and lower detection limits of the determination of trace radionuclides in environmental samples can become quite sophisticated and time consuming. This in turn could add significant cost to the analyses being performed. In the present method, a open-quotes deficit reduction approachclose quotes has been taken to keep costs low, but at the same time provide defensible data. In order to measure the accuracy of a particular method, reference samples are measured over the time period that the actual samples are being analyzed. Using a Lotus spreadsheet, data are compiled and an average accuracy is computed. If pairs of reference samples are analyzed, then precision can also be evaluated from the duplicate data sets. The standard deviation can be calculated if the reference concentrations of the duplicates are all in the same general range. Laboratory blanks are used to estimate the lower detection limits. The lower detection limit is calculated as 4.65 times the standard deviation of a set of blank determinations made over a given period of time. A Lotus spreadsheet is again used to compile data and LDLs over different periods of time can be compared

Potentials and Limitations of Real-Time Elastography for Prostate Cancer Detection: A Whole-Mount Step Section Analysis

Directory of Open Access Journals (Sweden)

Daniel Junker

2012-01-01

Full Text Available Objectives. To evaluate prostate cancer (PCa detection rates of real-time elastography (RTE in dependence of tumor size, tumor volume, localization and histological type. Materials and Methods. Thirdy-nine patients with biopsy proven PCa underwent RTE before radical prostatectomy (RPE to assess prostate tissue elasticity, and hard lesions were considered suspicious for PCa. After RPE, the prostates were prepared as whole-mount step sections and were compared with imaging findings for analyzing PCa detection rates. Results. RTE detected 6/62 cancer lesions with a maximum diameter of 0–5 mm (9.7%, 10/37 with a maximum diameter of 6–10 mm (27%, 24/34 with a maximum diameter of 11–20 20 mm (70.6%, 14/14 with a maximum diameter of >20 mm (100% and 40/48 with a volume ≥0.2 cm3 (83.3%. Regarding cancer lesions with a volume ≥ 0.2 cm³ there was a significant difference in PCa detection rates between Gleason scores with predominant Gleason pattern 3 compared to those with predominant Gleason pattern 4 or 5 (75% versus 100%; P=0.028. Conclusions. RTE is able to detect PCa of significant tumor volume and of predominant Gleason pattern 4 or 5 with high confidence, but is of limited value in the detection of small cancer lesions.

Recent advances in sample preparation techniques and methods of sulfonamides detection - A review.

Science.gov (United States)

Dmitrienko, Stanislava G; Kochuk, Elena V; Apyari, Vladimir V; Tolmacheva, Veronika V; Zolotov, Yury A

2014-11-19

Sulfonamides (SAs) have been the most widely used antimicrobial drugs for more than 70 years, and their residues in foodstuffs and environmental samples pose serious health hazards. For this reason, sensitive and specific methods for the quantification of these compounds in numerous matrices have been developed. This review intends to provide an updated overview of the recent trends over the past five years in sample preparation techniques and methods for detecting SAs. Examples of the sample preparation techniques, including liquid-liquid and solid-phase extraction, dispersive liquid-liquid microextraction and QuEChERS, are given. Different methods of detecting the SAs present in food and feed and in environmental, pharmaceutical and biological samples are discussed. Copyright © 2014 Elsevier B.V. All rights reserved.

Prediction of the limit of detection of an optical resonant reflection biosensor.

Science.gov (United States)

Hong, Jongcheol; Kim, Kyung-Hyun; Shin, Jae-Heon; Huh, Chul; Sung, Gun Yong

2007-07-09

A prediction of the limit of detection of an optical resonant reflection biosensor is presented. An optical resonant reflection biosensor using a guided-mode resonance filter is one of the most promising label-free optical immunosensors due to a sharp reflectance peak and a high sensitivity to the changes of optical path length. We have simulated this type of biosensor using rigorous coupled wave theory to calculate the limit of detection of the thickness of the target protein layer. Theoretically, our biosensor has an estimated ability to detect thickness change approximately the size of typical antigen proteins. We have also investigated the effects of the absorption and divergence of the incident light on the detection ability of the biosensor.

Systematic optimization of multiplex zymography protocol to detect active cathepsins K, L, S, and V in healthy and diseased tissue: compromise among limits of detection, reduced time, and resources.

Science.gov (United States)

Dumas, Jerald E; Platt, Manu O

2013-07-01

Cysteine cathepsins are a family of proteases identified in cancer, atherosclerosis, osteoporosis, arthritis, and a number of other diseases. As this number continues to rise, so does the need for low cost, broad use quantitative assays to detect their activity and can be translated to the clinic in the hospital or in low resource settings. Multiplex cathepsin zymography is one such assay that detects subnanomolar levels of active cathepsins K, L, S, and V in cell or tissue preparations observed as clear bands of proteolytic activity after gelatin substrate SDS-PAGE with conditions optimal for cathepsin renaturing and activity. Densitometric analysis of the zymogram provides quantitative information from this low cost assay. After systematic modifications to optimize cathepsin zymography, we describe reduced electrophoresis time from 2 h to 10 min, incubation assay time from overnight to 4 h, and reduced minimal tissue protein necessary while maintaining sensitive detection limits; an evaluation of the pros and cons of each modification is also included. We further describe image acquisition by Smartphone camera, export to Matlab, and densitometric analysis code to quantify and report cathepsin activity, adding portability and replacing large scale, darkbox imaging equipment that could be cost prohibitive in limited resource settings.

Systematic optimization of multiplex zymography protocol to detect active cathepsins K, L, S, and V in healthy and diseased tissue: compromise between limits of detection, reduced time, and resources

Science.gov (United States)

Dumas, Jerald E.; Platt, Manu O.

2013-01-01

Cysteine cathepsins are a family of proteases identified in cancer, atherosclerosis, osteoporosis, arthritis and a number of other diseases. As this number continues to rise, so does the need for low cost, broad use quantitative assays to detect their activity and can be translated to the clinic in the hospital or in low resource settings. Multiplex cathepsin zymography is one such assay that detects subnanomolar levels of active cathepsins K, L, S, and V in cell or tissue preparations observed as cleared bands of proteolytic activity after gelatin substrate SDS-PAGE with conditions optimal for cathepsin renaturing and activity. Densitometric analysis of the zymogram provides quantitative information from this low cost assay. After systematic modifications to optimize cathepsin zymography, we describe reduced electrophoresis time from 2 hours to 10 minutes, incubation assay time from overnight to 4 hours, and reduced minimal tissue protein necessary while maintaining sensitive detection limits; an evaluation of the pros and cons of each modification is also included. We further describe image acquisition by smartphone camera, export to Matlab, and densitometric analysis code to quantify and report cathepsin activity, adding portability and replacing large scale, darkbox imaging equipment that could be cost prohibitive in limited resource settings. PMID:23532386

Improvement in Limit of Detection of Enzymatic Biogas Sensor Utilizing Chromatography Paper for Breath Analysis.

Science.gov (United States)

Motooka, Masanobu; Uno, Shigeyasu

2018-02-02

Breath analysis is considered to be an effective method for point-of-care diagnosis due to its noninvasiveness, quickness and simplicity. Gas sensors for breath analysis require detection of low-concentration substances. In this paper, we propose that reduction of the background current improves the limit of detection of enzymatic biogas sensors utilizing chromatography paper. After clarifying the cause of the background current, we reduced the background current by improving the fabrication process of the sensors utilizing paper. Finally, we evaluated the limit of detection of the sensor with the sample vapor of ethanol gas. The experiment showed about a 50% reduction of the limit of detection compared to previously-reported sensor. This result presents the possibility of the sensor being applied in diagnosis, such as for diabetes, by further lowering the limit of detection.

Determining the lower limit of detection for personnel dosimetry systems

International Nuclear Information System (INIS)

Roberson, P.L.; Carlson, R.D.

1992-01-01

A simple method for determining the lower limit of detection (LLD) for personnel dosimetry systems is described. The method relies on the definition of a critical level and a detection level. The critical level is the signal level above which a result has a small probability of being due to a fluctuation of the background. All results below the critical level should not be reported as an indication of a positive result. The detection level is the net signal level (i.e., dose received) above which there is a high confidence that a true reading will be detected and reported as a qualitatively positive result. The detection level may be identified as the LLD. A simple formula is derived to allow the calculation of the LLD under various conditions. This type of formula is being used by the Department of Energy Laboratory Accreditation Program (DOELAP) for personnel dosimetry. Participants in either the National Voluntary Laboratory Accreditation Program (NVLAP) for personnel dosimetry or DOELAP can use performance test results along with a measurement of background levels to estimate the LLDs for their dosimetry system. As long as they maintain their dosimetry system such that the LLDs are less than half the lower limit of the NVLAP or DOELAP test exposure ranges, dosimetry laboratories can avoid testing failures due to poor performance at very low exposures

How low can the detection limit go with VPD-TXRF

International Nuclear Information System (INIS)

Wang, J.; Balazs, M.; Pianetta, P.; Baur, K.; Brennan, S.; Boone, T.; Rosamilia, J.

2000-01-01

The detection limit for synchrotron radiation total reflection x-ray fluorescence (TXRF) that can routinely be achieved for transition metals is about 8E7 atoms/cm 2 for a standard 1000 second counting time. This high sensitivity can be further improved by using a pre-concentration process such as vapor phase decomposition (VPD). The sensitivity enhancement of VPD-TXRF over TXRF is usually estimated from the ratio of the total wafer surface area to the instrumental sampling area on the wafer. For example, a 200 mm wafer with a 5 mm edge exclusion has a total surface area of 283.5 cm 2 . Assuming a sampling area of 0.126 cm 2 for the TXRF instrument at the Stanford Synchrotron Radiation Laboratory (SSRL) the gain in sensitivity for the VPD-TXRF technique will be 1 : 2250. This means, theoretically, that the TXRF detection limit of 8E7 atoms/cm 2 could be further reduced to 3.6 E4 atoms/cm 2 by applying this technique. During the VPD process, the contaminants on the wafer surface will be collected into a single droplet and dried on the wafer surface for TXRF analysis. However, impurities in the UPW (ultra pure water), chemicals or from handling cannot be ignored. Our investigation of wafers subjected, to different cleaning processes has revealed that background signals on the dry spot could arise from the VPD process itself. Therefore, the baseline determined by the purity of the UPW and starting chemicals limits the detection limits of VPD-SR-TXRF. (author)

Visualizing the Limits of Low Vision in Detecting Natural Image Features

NARCIS (Netherlands)

Hogervorst, M.A.; Damme, W.J.M. van

2008-01-01

Purpose. The purpose of our study was to develop a tool to visualize the limitations posed by visual impairments in detecting small and low-contrast elements in natural images. This visualization tool incorporates existing models of several aspects of visual perception, such as the band-limited

Minimum detection limit and spatial resolution of thin-sample field-emission electron probe microanalysis

International Nuclear Information System (INIS)

Kubo, Yugo; Hamada, Kotaro; Urano, Akira

2013-01-01

The minimum detection limit and spatial resolution for a thinned semiconductor sample were determined by electron probe microanalysis (EPMA) using a Schottky field emission (FE) electron gun and wavelength dispersive X-ray spectrometry. Comparison of the FE-EPMA results with those obtained using energy dispersive X-ray spectrometry in conjunction with scanning transmission electron microscopy, confirmed that FE-EPMA is largely superior in terms of detection sensitivity. Thin-sample FE-EPMA is demonstrated as a very effective method for high resolution, high sensitivity analysis in a laboratory environment because a high probe current and high signal-to-noise ratio can be achieved. - Highlights: • Minimum detection limit and spatial resolution determined for FE-EPMA. • Detection sensitivity of FE-EPMA greatly superior to that of STEM-EDX. • Minimum detection limit and spatial resolution controllable by probe current

Optimizing detectability

International Nuclear Information System (INIS)

Anon.

1992-01-01

HPLC is useful for trace and ultratrace analyses of a variety of compounds. For most applications, HPLC is useful for determinations in the nanogram-to-microgram range; however, detection limits of a picogram or less have been demonstrated in certain cases. These determinations require state-of-the-art capability; several examples of such determinations are provided in this chapter. As mentioned before, to detect and/or analyze low quantities of a given analyte at submicrogram or ultratrace levels, it is necessary to optimize the whole separation system, including the quantity and type of sample, sample preparation, HPLC equipment, chromatographic conditions (including column), choice of detector, and quantitation techniques. A limited discussion is provided here for optimization based on theoretical considerations, chromatographic conditions, detector selection, and miscellaneous approaches to detectability optimization. 59 refs

Research on the preparation, uniformity and stability of mixed standard substance for rapid detection of goat milk composition.

Science.gov (United States)

Zhu, Yuying; Wang, Jianmin; Wang, Cunfang

2018-05-01

Taking fresh goat milk as raw material after filtering, centrifuging, hollow fiber ultrafiltration, allocating formula, value detection and preparation processing, a set of 10 goat milk mixed standard substances was prepared on the basis of one-factor-at-a-time using a uniform design method, and its accuracy, uniformity and stability were evaluated by paired t-test and F-test of one-way analysis of variance. The results showed that three milk composition contents of these standard products were independent of each other, and the preparation using the quasi-level design method, and without emulsifier was the best program. Compared with detection value by cow milk standards for calibration fast analyzer, the calibration by goat milk mixed standard was more applicable to rapid detection of goat milk composition, detection value was more accurate and the deviation showed less error. Single factor analysis of variance showed that the uniformity and stability of the mixed standard substance were better; it could be stored for 15 days at 4°C. The uniformity and stability of the in-units and inter-units could meet the requirements of the preparation of national standard products. © 2018 Japanese Society of Animal Science.

Calculation of risk-based detection limits for radionuclides in the liquid effluents from Korean nuclear power plants

International Nuclear Information System (INIS)

Cheong, Jae Hak

2017-01-01

In order to review if present detection limits of radionuclides in liquid effluent from nuclear power plants are effective enough to warrant compliance with regulatory discharge limits, a risk-based approach is developed to derive a new detection limit for each radionuclide based on radiological criteria. Equations and adjustment factors are also proposed to discriminate the validity of the detection limits for multiple radionuclides in the liquid effluent with or without consideration of the nuclide composition. From case studies to three nuclear power plants in Korea with actual operation data from 2006 to 2015, the present detection limits have turned out to be effective for Hanul Unit 1 but may not be sensitive enough for Kori Unit 1 (8 out of 14 radionuclides) and Wolsong Unit 1 (9 out of 42 radionuclides). However, it is shown that the present detection limits for the latter two nuclear power plants can be justified, if credit is given to the radionuclide composition. Otherwise, consideration should be given to adjustment of the present detection limits. The risk-based approach of this study can be used to determine the validity of established detection limits of a specific nuclear power plant. (author)

Gold nanoparticle-based low limit of detection Love wave biosensor for carcinoembryonic antigens.

Science.gov (United States)

Li, Shuangming; Wan, Ying; Su, Yan; Fan, Chunhai; Bhethanabotla, Venkat R

2017-09-15

In this work, a Love wave biosensing platform is described for detecting cancer-related biomarker carcinoembryonic antigen (CEA). An ST 90°-X quartz Love wave device with a layer of SiO 2 waveguide was combined with gold nanoparticles (Au NPs) to amplify the mass loading effect of the acoustic wave sensor to achieve a limit of detection of 37pg/mL. The strategy involves modifying the Au NPs with anti-CEA antibody conjugates to form nanoprobes in a sandwich immunoassay. The unamplified detection limit of the Love wave biosensor is 9.4ng/mL. This 2-3 order of magnitude reduction in the limit of detection brings the SAW platform into the range useful for clinical diagnosis. Measurement electronics and microfluidics are easily constructed for acoustic wave biosensors, such as the Love wave device described here, allowing for robust platforms for point of care applications for cancer biomarkers in general. Copyright © 2017 Elsevier B.V. All rights reserved.

DETERMINATION OF LIMIT DETECTION OF THE ELEMENTS N, P, K, Si, Al, Fe, Cu, Cd, WITH FAST NEUTRON ACTIVATION USING NEUTRON GENERATOR

OpenAIRE

Sunardi, Sunardi; Muryono, Muryono

2010-01-01

Determination of limit detection of the elements N, P, K, Si, Al, Fe, Cu, Cd, with fast neutron activation using neutron generator has been done.  Samples prepared from SRM 2704, N, P, K elements from MERCK, Cu, Cd, Al from activation foil made in San Carlos, weighted and packed for certain weight then iradiated during 30 minutes with 14 MeV fast neutron using the neutron generator and then counted with gamma spectrometry (accuspec).  At this research condition of neutron generator was set at...

Experience with dose limitation during preparations for sea dumping operations

International Nuclear Information System (INIS)

Fieuw, G.; Voorde, N. van de; Baekelandt, L.

1982-01-01

Since 1967 low-level radioactive wastes from operational nuclear facilities in Belgium have been dumped into the sea. The dumping is carried out in accordance with the recommendations issued by the IAEA under the London Convention. All these dumping operations have taken place under the surveillance of the Nuclear Energy Agency of the OECD. To limit the doses received by workers and the public during the various phases leading up to sea dumping, appropriate measures are required in connection with waste treatment and packaging, limitation of radiation levels, storage and handling, organization and selection of the means of transport and organization and means of monitoring. Although treatment and handling at the nuclear sites are entrusted to occupationally exposed workers, temporary labour is used for the transport and handling operations. Effective treatment and packaging reduce the risk of internal exposure to a negligible value. Meticulous planning and permanent personnel monitoring reduce the doses received by the workers to acceptable values not exceeding the statutory dose limits. The doses received by personnel involved in the preparations for sea dumping operations from 1967 to 1980 are given and a relationship is established between these doses and the activities handled. Experience shows that sea dumping operations do not entail unacceptable risks either for the workers concerned or for the population and allows us to optimize the methods used for loading, handling and transport. (author)

Detection limit of 238U by gamma spectrometry

International Nuclear Information System (INIS)

Tartaglione, A.; Blostein, J.; Mayer, R

2004-01-01

The detection limit of 238 U was determined by gamma spectra measurements of a depleted uranium sample using four NaI(Tl) scintillators in a compact arrangement.The sample was shielded with 5 and 10 cm of lead.Two different methods for data processing were used and compared.It was established that an appropriate array of 40 detectors could establish the presence of 220 g of this material in only 5 minutes [es

Magnetic resonance colonography with a limited bowel preparation and automated carbon dioxide insufflation in comparison to conventional colonoscopy: Patient burden and preferences

Energy Technology Data Exchange (ETDEWEB)

Paardt, M.P. van der, E-mail: m.p.vanderpaardt@amc.uva.nl [Department of Radiology, Academic Medical Center Amsterdam, Amsterdam (Netherlands); Boellaard, T.N., E-mail: t.n.boellaard@amc.uva.nl [Department of Radiology, Academic Medical Center Amsterdam, Amsterdam (Netherlands); Zijta, F.M., E-mail: fmzijta@yahoo.com [Department of Radiology, Medisch Centrum Haaglanden, Den Haag (Netherlands); Baak, L.C., E-mail: l.c.baak@olvg.nl [Department of Gastroenterology and Hepatology, Onze Lieve Vrouwe Gasthuis, Amsterdam (Netherlands); Depla, A.C.T.M., E-mail: actm.depla@slz.nl [Department of Gastroenterology and Hepatology, Slotervaartziekenhuis, Amsterdam (Netherlands); Dekker, E., E-mail: e.dekker@amc.uva.nl [Department of Gastroenterology and Hepatology, Academic Medical Center Amsterdam, Amsterdam (Netherlands); Nederveen, A.J., E-mail: a.j.nederveen@amc.uva.nl [Department of Radiology, Academic Medical Center Amsterdam, Amsterdam (Netherlands); Bipat, S., E-mail: s.bipat@amc.uva.nl [Department of Radiology, Academic Medical Center Amsterdam, Amsterdam (Netherlands); Stoker, J., E-mail: j.stoker@amc.uva.nl [Department of Radiology, Academic Medical Center Amsterdam, Amsterdam (Netherlands)

2015-01-15

Highlights: • MR colonography with a limited bowel preparation and automated carbon dioxide insufflation demonstrated less burden compared to colonoscopy. • When discarding the bowel preparation, the examinations were rated equally burdensome. • The majority of patients preferred MR colonography over colonoscopy for their future examination of the bowel. - Abstract: Objectives: To evaluate patient burden and preferences for MR colonography with a limited bowel preparation and automated carbon dioxide insufflation in comparison to conventional colonoscopy. Methods: Symptomatic patients were consecutively recruited to undergo MR colonography with automated carbon dioxide insufflation and a limited bowel preparation followed within four weeks by colonoscopy with a standard bowel cleansing preparation. Four questionnaires regarding burden (on a five-point scale) and preferences (on a seven-point scale) were addressed after MR colonography and colonoscopy and five weeks after colonoscopy. Results: Ninety-nine patients (47 men, 52 women; mean age 62.3, SD 8.7) were included. None of the patients experienced severe or extreme burden from the MR colonography bowel preparation compared to 31.5% of the patients for the colonoscopy bowel preparation. Colonoscopy was rated more burdensome (25.6% severe or extreme burden) compared to MR colonography (5.2% severe or extreme burden) (P < 0.0001). When discarding the bowel preparations, the examinations were rated equally burdensome (P = 0.35). The majority of patients (61.4%) preferred MR colonography compared to colonoscopy (29.5%) immediately after the examinations and five weeks later (57.0% versus 39.5%). Conclusion: MR colonography with a limited bowel preparation and automated carbon dioxide insufflation demonstrated less burden compared to colonoscopy. The majority of patients preferred MR colonography over colonoscopy.

A low-volume polyethylene glycol solution was associated with an increased suboptimal bowel preparation rate but had similar recommendations for an early repeat colonoscopy, procedure times, and adenoma detection rates.

Directory of Open Access Journals (Sweden)

Sam C Hankins

Full Text Available Low-volume polyethylene glycol (PEG bowel preparations are better tolerated by patients than high-volume preparations and may achieve similar preparation quality. However, there is little data comparing their effects on a recommendation for an early repeat colonoscopy (because of a suboptimal preparation, procedure times, adenoma detection rate (ADR, and advanced adenoma detection rate (AADR.This is a retrospective cohort study of outpatient colonoscopies performed during a one-year period at a single academic medical center in which low-volume MoviPrep® (n = 1841 or high-volume Colyte® (n = 1337 was used. All preparations were split-dosed. Appropriate covariates were included in regression models assessing suboptimal preparation quality (fair, poor, or inadequate, procedure times, recommendation for an early repeat colonoscopy, ADR, and AADR.MoviPrep® was associated with an increase in having a suboptimal bowel preparation (OR 1.36; 95% CI: 1.06-1.76, but it was not associated with differences in insertion (p = 0.43, withdrawal (p = 0.22, or total procedure times (p = 0.10. The adjusted percentage with a suboptimal preparation was 11.7% for patients using MoviPrep® and 8.8% for patients using Colyte®. MoviPrep® was not associated with a significant difference in overall ADR (OR 0.93; 95% CI: 0.78-1.11, AADR (OR 1.18; 95% CI: 0.87-1.62, or recommendation for early repeat colonoscopy (OR 1.16; 95% CI: 0.72-1.88.MoviPrep® was associated with a small absolute increase in having a suboptimal preparation, but did not affect recommendations for an early repeat colonoscopy, procedure times, or adenoma detection rates. Mechanisms to reduce financial barriers limiting low-volume preparations should be considered because of their favorable tolerability profile.

Practical low dose limits for passive personal dosemeters and the implications for uncertainties close to the limit of detection

International Nuclear Information System (INIS)

Gilvin, P. J.; Perks, C. A.

2011-01-01

Recent years have seen the increasing use of passive dosemeters that have high sensitivities and, in laboratory conditions, detection limits of <10 μSv. However, in real operational use the detection limits will be markedly higher, because a large fraction of the accrued dose will be due to natural background, and this must be subtracted in order to obtain the desired occupational dose. No matter how well known the natural background is, the measurement uncertainty on doses of a few tens of microsieverts will be large. Individual monitoring services need to recognise this and manage the expectations of their clients by providing sufficient information. (authors)

Non-enzymatic hydrogen peroxide detection at NiO nanoporous thin film- electrodes prepared by physical vapor deposition at oblique angles

International Nuclear Information System (INIS)

Salazar, Pedro; Rico, Victor; González-Elipe, Agustín R.

2017-01-01

Highlights: • A non-enzymatic sensor for H 2 O 2 detection based on nickel thin film is reported. • Nanostructured nickel thin films are prepared by physical vapor deposition at oblique angles. • Main analytical parameters were obtained under optimal operation conditions. • Sensors depict an outstanding selectivity and a high stability. • Sensors are successfully used to determine H 2 O 2 in antiseptic solutions. - Abstract: In this work we report a non-enzymatic sensor for hydrogen peroxide (H 2 O 2 ) detection based on nanostructured nickel thin films prepared by physical vapor deposition at oblique angles. Porous thin films deposited on ITO substrates were characterized by X-ray diffraction analysis, scanning electron microcopy (SEMs), X-ray photoelectron spectroscopy (XPS) and electrochemical techniques such as Cyclic Voltammetry (CV) and Constant Potential Amperometry (CPA). The microstructure of the thin films consisted of inclined and separated Ni nanocolumns forming a porous thin layer of about 500 nm thickness. Prior to their use, the films surface was electrochemically modified and the chemical state studied by CV and XPS analysis. These techniques also showed that Ni 2+ /Ni 3+ species were involved in the electrochemical oxidation and detection of H 2 O 2 in alkaline medium. Main analytical parameters such as sensitivity (807 mA M −1 cm −2 ), limit of detection (3.22 μM) and linear range (0.011–2.4 mM) were obtained under optimal operation conditions. Sensors depicted an outstanding selectivity and a high stability and they were successfully used to determine H 2 O 2 concentration in commercial antiseptic solutions.

Possibilities for decreasing detection limits of analytical methods for determination of transformation products of unsymmetrical dimethylhydrazine in environmental samples

Directory of Open Access Journals (Sweden)

Bulat Kenessov

2015-12-01

Full Text Available Most rockets of middle and heavy class launched from Kazakhstan, Russia, China and other countries still use highly toxic unsymmetrical dimethylhydrazine (UDMH as a liquid propellant. Study of migration, distribution and accumulation of UDMH transformation products in environment and human health impact assessment of space rocket activity are currently complicated due to the absence of analytical methods allowing detection of trace concentrations of these compounds in analyzed samples. This paper reviews methods and approaches, which can be applied for development of such methods. Detection limits at a part-per-trillion (ppt level may be achieved using most selective and sensitive methods based on gas or liquid chromatography in combination of tandem or high-resolution mass spectrometry. In addition, 1000-fold concentration of samples or integrated sample preparation methods, e.g., dynamic headspace extraction, are required. Special attention during development and application of such methods must be paid to purity of laboratory air, reagents, glassware and analytical instruments.

Automated radioanalytical system incorporating microwave-assisted sample preparation, chemical separation, and online radiometric detection for the monitoring of total 99Tc in nuclear waste processing streams.

Science.gov (United States)

Egorov, Oleg B; O'Hara, Matthew J; Grate, Jay W

2012-04-03

An automated fluidic instrument is described that rapidly determines the total (99)Tc content of aged nuclear waste samples, where the matrix is chemically and radiologically complex and the existing speciation of the (99)Tc is variable. The monitor links microwave-assisted sample preparation with an automated anion exchange column separation and detection using a flow-through solid scintillator detector. The sample preparation steps acidify the sample, decompose organics, and convert all Tc species to the pertechnetate anion. The column-based anion exchange procedure separates the pertechnetate from the complex sample matrix, so that radiometric detection can provide accurate measurement of (99)Tc. We developed a preprogrammed spike addition procedure to automatically determine matrix-matched calibration. The overall measurement efficiency that is determined simultaneously provides a self-diagnostic parameter for the radiochemical separation and overall instrument function. Continuous, automated operation was demonstrated over the course of 54 h, which resulted in the analysis of 215 samples plus 54 hly spike-addition samples, with consistent overall measurement efficiency for the operation of the monitor. A sample can be processed and measured automatically in just 12.5 min with a detection limit of 23.5 Bq/mL of (99)Tc in low activity waste (0.495 mL sample volume), with better than 10% RSD precision at concentrations above the quantification limit. This rapid automated analysis method was developed to support nuclear waste processing operations planned for the Hanford nuclear site.

Determination and Interpretation of Characteristic Limits for Radioactivity Measurements: Decision Threshhold, Detection Limit and Limits of the Confidence Interval

International Nuclear Information System (INIS)

2017-01-01

Since 2004, the environment programme of the IAEA has included activities aimed at developing a set of procedures for analytical measurements of radionuclides in food and the environment. Reliable, comparable and fit for purpose results are essential for any analytical measurement. Guidelines and national and international standards for laboratory practices to fulfil quality assurance requirements are extremely important when performing such measurements. The guidelines and standards should be comprehensive, clearly formulated and readily available to both the analyst and the customer. ISO 11929:2010 is the international standard on the determination of the characteristic limits (decision threshold, detection limit and limits of the confidence interval) for measuring ionizing radiation. For nuclear analytical laboratories involved in the measurement of radioactivity in food and the environment, robust determination of the characteristic limits of radioanalytical techniques is essential with regard to national and international regulations on permitted levels of radioactivity. However, characteristic limits defined in ISO 11929:2010 are complex, and the correct application of the standard in laboratories requires a full understanding of various concepts. This publication provides additional information to Member States in the understanding of the terminology, definitions and concepts in ISO 11929:2010, thus facilitating its implementation in Member State laboratories.

Preparation of miniantibodies to Azospirillum brasilense Sp245 surface antigens and their use for bacterial detection.

Science.gov (United States)

Dykman, Lev A; Staroverov, Sergei A; Guliy, Olga I; Ignatov, Oleg V; Fomin, Alexander S; Vidyasheva, Irina V; Karavaeva, Olga A; Bunin, Viktor D; Burygin, Gennady L

2012-01-01

This article reports the first preparation of miniantibodies to Azospirillum brasilense Sp245 surface antigens by using a combinatorial phage library of sheep antibodies. The prepared phage antibodies were used for the first time for lipopolysaccharide and flagellin detection by dot assay, electro-optical analysis of cell suspensions, and transmission electron microscopy. Interaction of A. brasilense Sp245 with antilipopolysaccharide and antiflagellin phage-displayed miniantibodies caused the magnitude of the electro-optical signal to change considerably. The electro-optical results were in good agreement with the electron microscopic data. This is the first reported possibility of employing phage-displayed miniantibodies in bacterial detection aided by electro-optical analysis of cell suspensions.

Facile preparation of a DNA sensor for rapid herpes virus detection

Energy Technology Data Exchange (ETDEWEB)

Tam, Phuong Dinh, E-mail: tampd-hast@mail.hut.edu.vn [Hanoi Advanced School of Science and Technology, Hanoi University of Technology (Viet Nam); Tuan, Mai Anh, E-mail: tuanma-itims@mail.hut.edu.vn [International Training Institute for Materials Science, Hanoi University of Technology (Viet Nam); Huy, Tran Quang [National Institute of Hygiene and Epidemiology (NIHE), 01 Yersin, Hai Ba Trung District, Hanoi (Viet Nam); Le, Anh-Tuan [Hanoi Advanced School of Science and Technology, Hanoi University of Technology (Viet Nam); Hieu, Nguyen Van, E-mail: hieu@itims.edu.vn [International Training Institute for Materials Science, Hanoi University of Technology (Viet Nam)

2010-10-12

In this paper, a simple DNA sensor platform was developed for rapid herpes virus detection in real samples. The deoxyribonucleic acid (DNA) sequences of the herpes simplex virus (DNA probe) were directly immobilized on the surface of interdigitated electrodes by electrochemical polymerization along with pyrrole monomers. The potential was scanned from - 0.7 to + 0.6 V, and the scanning rate was 100 mV/s. Fourier transform infrared spectroscopy was employed to verify specific DNA sequence binding and the conducting polymer. The morphology of the conducting polymer doped with DNA strands was characterized using a field emission scanning electron microscope. As-obtained DNA sensor was used to detect the herpes virus DNA in the real samples. The results show that the current DNA sensors detected the lowest DNA concentration of 2 nM. This sensitivity appears to be better than that of the DNA sensors prepared by immobilization of the DNA probe on the 3-aminopropyl-triethoxy-silance (APTS) membrane.

Preparation of bioconjugates of CdTe nanocrystals for cancer marker detection

International Nuclear Information System (INIS)

Hu Fengqin; Ran Yuliang; Zhou Zhuan; Gao Mingyuan

2006-01-01

Highly fluorescent CdTe quantum dots (Q-dots) stabilized by 3-mercaptopropionic acid (MPA) were prepared by an aqueous solution approach and used as fluorescent labels in detecting a cancer marker, carcinoembryonic antigen (CEA), expressed on human colon carcinoma cell line LS 180. Nonspecific adsorptions of CdTe Q-dots on carcinoma cells were observed and effectively eliminated by replacing MPA with a thiolated PEG (poly(ethylene glycol), Mn = 750) synthesized according to literature. It was unexpectedly found out that the PEG-coated CdTe Q-dots exhibited very strong and specific affinity to anti-CEA monoclonal antibody rch 24 (rch 24 mAb). The resultant CdTe-(rch 24 mAb) conjugates were successfully used in detections of CEA expressed on the surface of cell line LS 180. Further experiments demonstrated that the fluorescent CdTe Q-dots exhibited much better photostability and a brighter fluorescence than FITC, which consequently led to a higher efficiency in the cancer marker detection

Facile preparation of a DNA sensor for rapid herpes virus detection

International Nuclear Information System (INIS)

Tam, Phuong Dinh; Tuan, Mai Anh; Huy, Tran Quang; Le, Anh-Tuan; Hieu, Nguyen Van

2010-01-01

In this paper, a simple DNA sensor platform was developed for rapid herpes virus detection in real samples. The deoxyribonucleic acid (DNA) sequences of the herpes simplex virus (DNA probe) were directly immobilized on the surface of interdigitated electrodes by electrochemical polymerization along with pyrrole monomers. The potential was scanned from - 0.7 to + 0.6 V, and the scanning rate was 100 mV/s. Fourier transform infrared spectroscopy was employed to verify specific DNA sequence binding and the conducting polymer. The morphology of the conducting polymer doped with DNA strands was characterized using a field emission scanning electron microscope. As-obtained DNA sensor was used to detect the herpes virus DNA in the real samples. The results show that the current DNA sensors detected the lowest DNA concentration of 2 nM. This sensitivity appears to be better than that of the DNA sensors prepared by immobilization of the DNA probe on the 3-aminopropyl-triethoxy-silance (APTS) membrane.

Weighted Polynomial Approximation for Automated Detection of Inspiratory Flow Limitation

Directory of Open Access Journals (Sweden)

Sheng-Cheng Huang

2017-01-01

Full Text Available Inspiratory flow limitation (IFL is a critical symptom of sleep breathing disorders. A characteristic flattened flow-time curve indicates the presence of highest resistance flow limitation. This study involved investigating a real-time algorithm for detecting IFL during sleep. Three categories of inspiratory flow shape were collected from previous studies for use as a development set. Of these, 16 cases were labeled as non-IFL and 78 as IFL which were further categorized into minor level (20 cases and severe level (58 cases of obstruction. In this study, algorithms using polynomial functions were proposed for extracting the features of IFL. Methods using first- to third-order polynomial approximations were applied to calculate the fitting curve to obtain the mean absolute error. The proposed algorithm is described by the weighted third-order (w.3rd-order polynomial function. For validation, a total of 1,093 inspiratory breaths were acquired as a test set. The accuracy levels of the classifications produced by the presented feature detection methods were analyzed, and the performance levels were compared using a misclassification cobweb. According to the results, the algorithm using the w.3rd-order polynomial approximation achieved an accuracy of 94.14% for IFL classification. We concluded that this algorithm achieved effective automatic IFL detection during sleep.

Aerosol quantification with the Aerodyne Aerosol Mass Spectrometer: detection limits and ionizer background effects

Directory of Open Access Journals (Sweden)

S. Borrmann

2009-02-01

Full Text Available Systematic laboratory experiments were performed to investigate quantification of various species with two versions of the Aerodyne Aerosol Mass Spectrometer, a Quadrupole Aerosol Mass Spectrometer (Q-AMS and a compact Time-of-Flight Aerosol Mass Spectrometer (c-ToF-AMS. Here we present a new method to continuously determine the detection limits of the AMS analyzers during regular measurements, yielding detection limit (DL information under various measurement conditions. Minimum detection limits range from 0.03 μg m⁻³ (nitrate, sulfate, and chloride up to 0.5 μg m⁻³ (organics for the Q-AMS. Those of the c-ToF-AMS are found between 0.003 μg m⁻³ (nitrate, sulfate and 0.03 μg m⁻³ (ammonium, organics. The DL values found for the c-ToF-AMS were ~10 times lower than those of the Q-AMS, mainly due to differences in ion duty cycle. Effects causing an increase of the detection limits include long-term instrument contamination, measurement of high aerosol mass concentrations and short-term instrument history. The self-cleaning processes which reduce the instrument background after measurement of large aerosol concentrations as well as the influences of increased instrument background on mass concentration measurements are discussed. Finally, improvement of detection limits by extension of averaging time intervals, selected or reduced ion monitoring, and variation of particle-to-background measurement ratio are investigated.

Including Below Detection Limit Samples in Post Decommissioning Soil Sample Analyses

Energy Technology Data Exchange (ETDEWEB)

Kim, Jung Hwan; Yim, Man Sung [KAIST, Daejeon (Korea, Republic of)

2016-05-15

To meet the required standards the site owner has to show that the soil at the facility has been sufficiently cleaned up. To do this one must know the contamination of the soil at the site prior to clean up. This involves sampling that soil to identify the degree of contamination. However there is a technical difficulty in determining how much decontamination should be done. The problem arises when measured samples are below the detection limit. Regulatory guidelines for site reuse after decommissioning are commonly challenged because the majority of the activity in the soil at or below the limit of detection. Using additional statistical analyses of contaminated soil after decommissioning is expected to have the following advantages: a better and more reliable probabilistic exposure assessment, better economics (lower project costs) and improved communication with the public. This research will develop an approach that defines an acceptable method for demonstrating compliance of decommissioned NPP sites and validates that compliance. Soil samples from NPP often contain censored data. Conventional methods for dealing with censored data sets are statistically biased and limited in their usefulness.

Detection limit for rate fluctuations in inhomogeneous Poisson processes

Science.gov (United States)

Shintani, Toshiaki; Shinomoto, Shigeru

2012-04-01

Estimations of an underlying rate from data points are inevitably disturbed by the irregular occurrence of events. Proper estimation methods are designed to avoid overfitting by discounting the irregular occurrence of data, and to determine a constant rate from irregular data derived from a constant probability distribution. However, it can occur that rapid or small fluctuations in the underlying density are undetectable when the data are sparse. For an estimation method, the maximum degree of undetectable rate fluctuations is uniquely determined as a phase transition, when considering an infinitely long series of events drawn from a fluctuating density. In this study, we analytically examine an optimized histogram and a Bayesian rate estimator with respect to their detectability of rate fluctuation, and determine whether their detectable-undetectable phase transition points are given by an identical formula defining a degree of fluctuation in an underlying rate. In addition, we numerically examine the variational Bayes hidden Markov model in its detectability of rate fluctuation, and determine whether the numerically obtained transition point is comparable to those of the other two methods. Such consistency among these three principled methods suggests the presence of a theoretical limit for detecting rate fluctuations.

Detection limit for rate fluctuations in inhomogeneous Poisson processes.

Science.gov (United States)

Shintani, Toshiaki; Shinomoto, Shigeru

2012-04-01

Estimations of an underlying rate from data points are inevitably disturbed by the irregular occurrence of events. Proper estimation methods are designed to avoid overfitting by discounting the irregular occurrence of data, and to determine a constant rate from irregular data derived from a constant probability distribution. However, it can occur that rapid or small fluctuations in the underlying density are undetectable when the data are sparse. For an estimation method, the maximum degree of undetectable rate fluctuations is uniquely determined as a phase transition, when considering an infinitely long series of events drawn from a fluctuating density. In this study, we analytically examine an optimized histogram and a Bayesian rate estimator with respect to their detectability of rate fluctuation, and determine whether their detectable-undetectable phase transition points are given by an identical formula defining a degree of fluctuation in an underlying rate. In addition, we numerically examine the variational Bayes hidden Markov model in its detectability of rate fluctuation, and determine whether the numerically obtained transition point is comparable to those of the other two methods. Such consistency among these three principled methods suggests the presence of a theoretical limit for detecting rate fluctuations.

Preparation of genosensor for detection of specific DNA sequence of the hepatitis B virus

International Nuclear Information System (INIS)

Honorato Castro, Ana C.; França, Erick G.; Paula, Lucas F. de; Soares, Marcia M.C.N.; Goulart, Luiz R.; Madurro, João M.; Brito-Madurro, Ana G.

2014-01-01

Graphical abstract: - Highlights: • Specific oligonucleotide detection for hepatitis B based on poly-4-aminophenol matrix. • Electrochemical detection of the gene specific using ethidium bromide as indicator. • The detection limit was 2.61 nmol L −1 , with a correlation coefficient of 0.998 (n = 3). • The system discriminates three-base mismatches and non-complementary target. - Abstract: An electrochemical genosensor was constructed for detection of specific DNA sequence of the hepatitis B virus, based on graphite electrodes modified with poly(4-aminophenol) and incorporating a specific oligonucleotide probe. The modified electrode containing the probe was evaluated by differential pulse voltammetry, before and after incubation with the complementary oligonucleotide target. Detection was performed by monitoring oxidizable DNA bases (direct detection) or using ethidium bromide as indicator of the hybridization process (indirect detection). The device showed a detection limit for the oligonucleotide target of 2.61 nmol L −1 . Indirect detection using ethidium bromide was promising in discriminating mismatches, which is a very desirable attribute for detection of disease-related point mutations. In addition, it was possible to observe differences between hybridized and non-hybridized surfaces by atomic force microscopy

Preparation of genosensor for detection of specific DNA sequence of the hepatitis B virus

Energy Technology Data Exchange (ETDEWEB)

Honorato Castro, Ana C.; França, Erick G. [Institute of Genetics and Biochemistry, Federal University of Uberlândia, Uberlândia (Brazil); Paula, Lucas F. de [Institute of Chemistry, Federal University of Uberlândia, Uberlândia (Brazil); Soares, Marcia M.C.N. [Adolfo Lutz Institute, Regional Laboratory in São José do Rio Preto (Brazil); Goulart, Luiz R. [Institute of Genetics and Biochemistry, Federal University of Uberlândia, Uberlândia (Brazil); Madurro, João M. [Institute of Chemistry, Federal University of Uberlândia, Uberlândia (Brazil); Brito-Madurro, Ana G., E-mail: agbrito@iqufu.ufu.br [Institute of Genetics and Biochemistry, Federal University of Uberlândia, Uberlândia (Brazil)

2014-09-30

Graphical abstract: - Highlights: • Specific oligonucleotide detection for hepatitis B based on poly-4-aminophenol matrix. • Electrochemical detection of the gene specific using ethidium bromide as indicator. • The detection limit was 2.61 nmol L{sup −1}, with a correlation coefficient of 0.998 (n = 3). • The system discriminates three-base mismatches and non-complementary target. - Abstract: An electrochemical genosensor was constructed for detection of specific DNA sequence of the hepatitis B virus, based on graphite electrodes modified with poly(4-aminophenol) and incorporating a specific oligonucleotide probe. The modified electrode containing the probe was evaluated by differential pulse voltammetry, before and after incubation with the complementary oligonucleotide target. Detection was performed by monitoring oxidizable DNA bases (direct detection) or using ethidium bromide as indicator of the hybridization process (indirect detection). The device showed a detection limit for the oligonucleotide target of 2.61 nmol L{sup −1}. Indirect detection using ethidium bromide was promising in discriminating mismatches, which is a very desirable attribute for detection of disease-related point mutations. In addition, it was possible to observe differences between hybridized and non-hybridized surfaces by atomic force microscopy.

Improved detection limits for phthalates by selective solid-phase micro-extraction

KAUST Repository

Zia, Asif I.; Afsarimanesh, Nasrin; Xie, Li; Nag, Anindya; Al-Bahadly, I. H.; Yu, P. L.; Kosel, Jü rgen

2016-01-01

Presented research reports on an improved method and enhanced limits of detection for phthalates; a hazardous additive used in the production of plastics by solid-phase micro-extraction (SPME) polymer in comparison to molecularly imprinted solid

Fabrication of Stretchable Copper Coated Carbon Nanotube Conductor for Non-Enzymatic Glucose Detection Electrode with Low Detection Limit and Selectivity

Directory of Open Access Journals (Sweden)

Dawei Jiang

2018-03-01

Full Text Available The increasing demand for wearable glucose sensing has stimulated growing interest in stretchable electrodes. The development of the electrode materials having large stretchability, low detection limit, and good selectivity is the key component for constructing high performance wearable glucose sensors. In this work, we presented fabrication of stretchable conductor based on the copper coated carbon nanotube sheath-core fiber, and its application as non-enzymatic electrode for glucose detection with high stretchability, low detection limit, and selectivity. The sheath-core fiber was fabricated by coating copper coated carbon nanotube on a pre-stretched rubber fiber core followed by release of pre-stretch, which had a hierarchically buckled structure. It showed a small resistance change as low as 27% as strain increasing from 0% to 500% strain, and a low resistance of 0.4 Ω·cm−1 at strain of 500%. This electrode showed linear glucose concentration detection in the range between 0.05 mM and 5 mM and good selectivity against sucrose, lactic acid, uric acid, acrylic acid in phosphate buffer saline solution, and showed stable signal in high salt concentration. The limit of detection (LOD was 0.05 mM, for the range of 0.05–5 mM, the sensitivity is 46 mA·M−1. This electrode can withstand large strain of up to 60% with negligible influence on its performance.

The detection limits of antimicrobial agents in cow's milk by a simple Yoghurt Culture Test.

Science.gov (United States)

Mohsenzadeh, M; Bahrainipour, A

2008-09-15

The aim of this study was to study performance of Yoghurt Culture Test (YCT) in the detection of antimicrobial residues in milk. For this purpose, the sensitivity of YCT for 15 antibiotics were determined. For each drug, 8 concentrations were tested. The detection limits of YCT at 2.5 h and 4 h incubation were determined (microg kg(-1)): 15 and 37.5, penicillin G; 4 and 5, ampicillin; 5 and 7.5, amoxycillin; 100 and 200, cephalexin; 80 and 100, cefazoline; 100 and 200, oxytetracycline; 500 and 100, chlortetracycline; 100 and 200, tetracycline; 150 and 200, doxycycline; 200 and 400, sulphadimidine; 500 and 1000, gentamycin; 1000 and 1500, spectinomycin; 400 and 500, erythromycin; 50 and 100, tylosin; 5000 and 10000, chloramphenicol. The YCT detection limits at 2.5 h incubation for ampicillin, cephalexin, tetracycline, oxytetracycline and tylosin are similar to those obtained as Maximum Residue Limit (MRL) according to Regulation 2377/90 EEC as set out by the European Union. In addition the detection limits of YCT for some antibiotics were lower than some of microbial inhibitor test.

Facile preparation of surfactant-free Au NPs/RGO/Ni foam for degradation of 4-nitrophenol and detection of hydrogen peroxide

Science.gov (United States)

Liu, Y. Y.; Guo, X. L.; Zhao, L.; Zhu, L.; Chen, Z. T.; Chen, J.; Zhang, Y.; Sun, L. T.; Zhao, Y. H.

2018-06-01

The application of Au nanoparticles (Au NPs) often requires surface modification with chemical surfactants, which dramatically reduce the surface activity and increase the chemical contamination and cost of Au NPs. In this research, we have developed a novel Au NPs/reduced graphene oxide/Ni foam hybrid (Au NPs/RGO/NiF) by in situ reduction through ascorbic acid and replacement reaction. This method is green, facile and efficient. The Au NPs are free of chemical surfactants and are homogeneously distributed on the surface of the RGO/NiF. The as-prepared Au NPs/RGO/NiF hybrid is uniform, stable and exhibits not only a high reduction efficiency for the reduction of 4-nitrophenol with a catalytic kinetic constant of up to 0.46 min‑1 (0.15 cm3 catalysis) but also a sensitive and selective detection of H2O2 with a detection limit of ∼1.60 μM.

Carbon quantum dots prepared with polyethyleneimine as both reducing agent and stabilizer for synthesis of Ag/CQDs composite for Hg{sup 2+} ions detection

Energy Technology Data Exchange (ETDEWEB)

Liu, Ting; Dong, Jiang Xue; Liu, Shi Gang; Li, Na; Lin, Shu Min; Fan, Yu Zhu [Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), School of Chemistry and Chemical Engineering, Southwest University, No.2 Tiansheng Road, BeiBei District, Chongqing 400715 (China); Lei, Jing Lie [School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400044 (China); Luo, Hong Qun, E-mail: luohq@swu.edu.cn [Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), School of Chemistry and Chemical Engineering, Southwest University, No.2 Tiansheng Road, BeiBei District, Chongqing 400715 (China); Li, Nian Bing, E-mail: linb@swu.edu.cn [Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), School of Chemistry and Chemical Engineering, Southwest University, No.2 Tiansheng Road, BeiBei District, Chongqing 400715 (China)

2017-01-15

Highlights: • The carbon quantum dots (CQDs) synthesized with PEI showed an extraordinary reducibility. • The Ag/CQDs composite was prepared by using CQDs as reducing and stabilizing agent. • A simple Ag/CQDs composite-based dual-signal probe was provided for Hg{sup 2+} detection. • The proposed strategy shows a potential for detecting Hg{sup 2+} in real water samples. - Abstract: A stable silver nanoparticles/carbon quantum dots (Ag/CQDs) composite was prepared by using CQDs as reducing and stabilizing agent. The CQDs synthesized with polyethyleneimine (PEI) showed an extraordinary reducibility. When Hg{sup 2+} was presented in the Ag/CQDs composite solution, a color change from yellow to colorless was observed, accompanied by a shift of surface plasmon resonance (SPR) band and decrease in absorbance of the Ag/CQDs composite. On the basis of the further studies on TEM, XPS and XRD analysis, the possible mechanism is attributed to the formation of a silver-mercury amalgam. Hence, a two dimensional sensing platform for Hg{sup 2+} detection was constructed upon the Ag/CQDs composite. Based on the change of absorbance, a good linear relationship was obtained from 0.5 to 50 μM for Hg{sup 2+}. And the limit of detection for Hg{sup 2+} was as low as 85 nM, representing high sensitivity to Hg{sup 2+}. More importantly, the proposed method also exhibits a good selectivity toward Hg{sup 2+} over other metal ions. Besides, this strategy demonstrates practicability for the detection of Hg{sup 2+} in real water samples with satisfactory results.

Limited interlaboratory comparison of Schmallenberg virus antibody detection in serum samples

DEFF Research Database (Denmark)

van der Poel, W. H. M.; Cay, B.; Zientara, S.

2014-01-01

Eight veterinary institutes in seven different countries in Europe participated in a limited interlaboratory comparison trial to evaluate laboratory performances of Schmallenberg virus (SBV) antibody detection in serum. Seven different sheep sera and three different cattle sera were circulated, a...

Detection limits for nanoparticles in solution with classical turbidity spectra

Science.gov (United States)

Le Blevennec, G.

2013-09-01

Detection of nanoparticles in solution is required to manage safety and environmental problems. Spectral transmission turbidity method has now been known for a long time. It is derived from the Mie Theory and can be applied to any number of spheres, randomly distributed and separated by large distance compared to wavelength. Here, we describe a method for determination of size, distribution and concentration of nanoparticles in solution using UV-Vis transmission measurements. The method combines Mie and Beer Lambert computation integrated in a best fit approximation. In a first step, a validation of the approach is completed on silver nanoparticles solution. Verification of results is realized with Transmission Electronic Microscopy measurements for size distribution and an Inductively Coupled Plasma Mass Spectrometry for concentration. In view of the good agreement obtained, a second step of work focuses on how to manage the concentration to be the most accurate on the size distribution. Those efficient conditions are determined by simple computation. As we are dealing with nanoparticles, one of the key points is to know what the size limits reachable are with that kind of approach based on classical electromagnetism. In taking into account the transmission spectrometer accuracy limit we determine for several types of materials, metals, dielectrics, semiconductors the particle size limit detectable by such a turbidity method. These surprising results are situated at the quantum physics frontier.

Improvement of detection limits of PIXE by substrate signal reduction

International Nuclear Information System (INIS)

Beaulieu, S.; Nejedly, Z.; Campbell, J.L.; Edwards, G.C.; Dias, G.M.

2002-01-01

Limits of detection (LODs) for aerosol samples collected using PIXE International cascade impactors, were improved approximately 50% after reducing the cross-sectional area of the analytical beam based on results obtained from microscope photographs of aerosol deposits. Improvements in LODs were most noticeable for selected elements collected on the smaller stages of the impactor (stages 1-3)

Detection of Salmonella enterica in Meat in Less than 5 Hours by a Low-Cost and Noncomplex Sample Preparation Method

Science.gov (United States)

Hoorfar, J.; Hansen, F.; Christensen, J.; Mansdal, S.; Josefsen, M. H.

2016-01-01

ABSTRACT Salmonella is recognized as one of the most important foodborne bacteria and has wide health and socioeconomic impacts worldwide. Fresh pork meat is one of the main sources of Salmonella, and efficient and fast methods for detection are therefore necessary. Current methods for Salmonella detection in fresh meat usually include >16 h of culture enrichment, in a few cases meat, consisting of a 3-h enrichment in standard buffered peptone water and a real-time PCR-compatible sample preparation method based on filtration, centrifugation, and enzymatic digestion, followed by fast-cycling real-time PCR detection. The method was validated in an unpaired comparative study against the Nordic Committee on Food Analysis (NMKL) reference culture method 187. Pork meat samples (n = 140) were either artificially contaminated with Salmonella at 0, 1 to 10, or 10 to 100 CFU/25 g of meat or naturally contaminated. Cohen's kappa for the degree of agreement between the rapid method and the reference was 0.64, and the relative accuracy, sensitivity, and specificity for the rapid method were 81.4, 95.1, and 97.9%, respectively. The 50% limit of detections (LOD50s) were 8.8 CFU/25 g for the rapid method and 7.7 CFU/25 g for the reference method. Implementation of this method will enable faster release of Salmonella low-risk meat, providing savings for meat producers, and it will help contribute to improved food safety. IMPORTANCE While the cost of analysis and hands-on time of the presented rapid method were comparable to those of reference culture methods, the fast product release by this method can provide the meat industry with a competitive advantage. Not only will the abattoirs save costs for work hours and cold storage, but consumers and retailers will also benefit from fresher meat with a longer shelf life. Furthermore, the presented sample preparation might be adjusted for application in the detection of other pathogenic bacteria in different sample types. PMID:27986726

Calculation of the detection limits for radionuclides identified in gamma-ray spectra based on post-processing peak analysis results.

Science.gov (United States)

Korun, M; Vodenik, B; Zorko, B

2018-03-01

A new method for calculating the detection limits of gamma-ray spectrometry measurements is presented. The method is applicable for gamma-ray emitters, irrespective of the influences of the peaked background, the origin of the background and the overlap with other peaks. It offers the opportunity for multi-gamma-ray emitters to calculate the common detection limit, corresponding to more peaks. The detection limit is calculated by approximating the dependence of the uncertainty in the indication on its value with a second-order polynomial. In this approach the relation between the input quantities and the detection limit are described by an explicit expression and can be easy investigated. The detection limit is calculated from the data usually provided by the reports of peak-analyzing programs: the peak areas and their uncertainties. As a result, the need to use individual channel contents for calculating the detection limit is bypassed. Copyright © 2017 Elsevier Ltd. All rights reserved.

Detection of radiation-induced hydrocarbons in baked sponged cake prepared with irradiated liquid egg

Science.gov (United States)

Schulzki, G.; Spiegelberg, A.; Bögl, K. W.; Schreiber, G. A.

1995-02-01

For identification of irradiated food, radiation-induced volatile hydrocarbons (HC) are determined by gas chromatography in the non-polar fraction of fat. However, in complex food matrices the detection is often disturbed by fat-associated compounds. On-line coupling of high performance liquid chromatography (LC) and gas chromatography (GC) is very efficient to remove such compounds from the HC fraction. The high sensitivity of this fast and efficient technique is demonstrated by the example of detection of radiation-induced HC in fat isolated from baked sponge cake which had been prepared with irradiated liquid egg.

Signal detection without finite-energy limits to quantum resolution

OpenAIRE

Luis Aina, Alfredo

2013-01-01

We show that there are extremely simple signal detection schemes where the finiteness of energy resources places no limit on the resolution. On the contrary, larger resolution can be obtained with lower energy. To this end the generator of the signal-dependent transformation encoding the signal information on the probe state must be different from the energy. We show that the larger the deviation of the probe state from being the minimum-uncertainty state, the better the resolution.

Investigation of contactless detection using a giant magnetoresistance sensor for detecting prostate specific antigen.

Science.gov (United States)

Sun, Xuecheng; Zhi, Shaotao; Lei, Chong; Zhou, Yong

2016-08-01

This paper presents a contactless detection method for detecting prostate specific antigen with a giant magnetoresistance sensor. In contactless detection case, the prostate specific antigen sample preparation was separated from the sensor that prevented the sensor from being immersed in chemical solvents, and made the sensor implementing in immediately reuse without wash. Experimental results showed that applied an external magnetic field in a range of 50 Oe to 90 Oe, Dynabeads with a concentration as low as 0.1 μg/mL can be detected by this system and could give an approximate quantitation to the logarithmic of Dynabeads concentration. Sandwich immunoassay was employed for preparing PSA samples. The PSA capture was implemented on a gold film modified with a self-assembled monolayer and using biotinylated secondary antibody against PSA and streptavidinylated Dynabeads. With DC magnetic field in the range of 50 to 90 Oe, PSA can be detected with a detection limit as low as 0.1 ng/mL. Samples spiked with different concentrations of PSA can be distinguished clearly. Due to the contactless detection method, the detection system exhibited advantages such as convenient manipulation, reusable, inexpensive, small weight. So, this detection method was a promising candidate in biomarker detection, especially in point of care detection.

In vitro bioassays for detecting dioxin-like activity--application potentials and limits of detection, a review.

Science.gov (United States)

Eichbaum, Kathrin; Brinkmann, Markus; Buchinger, Sebastian; Reifferscheid, Georg; Hecker, Markus; Giesy, John P; Engwall, Magnus; van Bavel, Bert; Hollert, Henner

2014-07-15

Use of in vitro assays as screening tool to characterize contamination of a variety of environmental matrices has become an increasingly popular and powerful toolbox in the field of environmental toxicology. While bioassays cannot entirely substitute analytical methods such as gas chromatography-mass spectrometry (GC-MS), the increasing improvement of cell lines and standardization of bioassay procedures enhance their utility as bioanalytical pre-screening tests prior to more targeted chemical analytical investigations. Dioxin-receptor-based assays provide a holistic characterization of exposure to dioxin-like compounds (DLCs) by integrating their overall toxic potential, including potentials of unknown DLCs not detectable via e.g. GC-MS. Hence, they provide important additional information with respect to environmental risk assessment of DLCs. This review summarizes different in vitro bioassay applications for detection of DLCs and considers the comparability of bioassay and chemical analytically derived toxicity equivalents (TEQs) of different approaches and various matrices. These range from complex samples such as sediments through single reference to compound mixtures. A summary of bioassay derived detection limits (LODs) showed a number of current bioassays to be equally sensitive as chemical methodologies, but moreover revealed that most of the bioanalytical studies conducted to date did not report their LODs, which represents a limitation with regard to low potency samples. Copyright © 2014 Elsevier B.V. All rights reserved.

Method to Solve the Problem of the Radioactivity Detection in Environmental Samples. Characteristic Limits

International Nuclear Information System (INIS)

Gasco, C.; Martinez, M.; Heras, M.

2009-01-01

The problem of the detection or when the radioactivity can be considered as higher than the background using different measurement techniques has been the objective of several statistical studies and controversies. The detection limit and the critical limit were studied by Currie in year 1968 and used by radiochemistry laboratories considering different ways of calculation that introduced confusion and not correct implementations. In the last few years, and due to the increasing number of standardization processes on the field of radioactivity and accreditation, several international institutions have chosen to unify the criteria for using common determination of detection limits. The most used methods are those developed by MARLAP and International Standard Organization ISO (Standard-11929). In this report are summarised both standards doing a comparative study and giving some examples of how to apply these limits. In same cases, little differences in the uncertainty calculation have been observed but the final results have been concordant. A deeply study of these standards can be done consulting the web page of the American Labs that developed MARLAP or buying the original ISO standard ISO-11929 recently approved (2009). (Author) 17 refs

Predictive inference for best linear combination of biomarkers subject to limits of detection.

Science.gov (United States)

Coolen-Maturi, Tahani

2017-08-15

Measuring the accuracy of diagnostic tests is crucial in many application areas including medicine, machine learning and credit scoring. The receiver operating characteristic (ROC) curve is a useful tool to assess the ability of a diagnostic test to discriminate between two classes or groups. In practice, multiple diagnostic tests or biomarkers are combined to improve diagnostic accuracy. Often, biomarker measurements are undetectable either below or above the so-called limits of detection (LoD). In this paper, nonparametric predictive inference (NPI) for best linear combination of two or more biomarkers subject to limits of detection is presented. NPI is a frequentist statistical method that is explicitly aimed at using few modelling assumptions, enabled through the use of lower and upper probabilities to quantify uncertainty. The NPI lower and upper bounds for the ROC curve subject to limits of detection are derived, where the objective function to maximize is the area under the ROC curve. In addition, the paper discusses the effect of restriction on the linear combination's coefficients on the analysis. Examples are provided to illustrate the proposed method. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Carbon nanotubes for gas detection: materials preparation and device assembly

International Nuclear Information System (INIS)

Terranova, M L; Lucci, M; Orlanducci, S; Tamburri, E; Sessa, V; Reale, A; Carlo, A Di

2007-01-01

An efficient sensing device for NH 3 and NO x detection has been realized using ordered arrays of single-walled C nanotubes deposited onto an interdigitated electrode platform operating at room temperature. The sensing material has been prepared using several chemical-physical techniques for purification and positioning of the nanotubes inside the electrode gaps. In particular, both DC and AC fields have been applied in order to move and to align the nanostructures by electrophoresis and dielectrophoresis processes. We investigated the effects of different voltages applied to a gate contact on the back side of the substrate on the performances of the device and found that for different gas species (NH 3 , NO x ) a constant gate bias increases the sensitivity for gas detection. Moreover, in this paper we demonstrate that a pulsed bias applied to the gate contact facilitates the gas interaction with the nanotubes, either reducing the absorption times or accelerating the desorption times, thus providing a fast acceleration and a dramatic improvement of the time dependent behaviour of the device

Decreasing of the detection limit for gamma-ray Spectrometry with the influence of sample treatment

International Nuclear Information System (INIS)

Karami, M.; Sadighzadeh, A.; Asgharizadeh, F.; Sardari, D.; Tavassoli, A.; Arbabi, A.; Hochaghani, O.

2009-01-01

Full text: In this study the ash method has been applied for environmental sample treatment in order to decrease of the detection limit in gamma-ray spectrometry for low level radioactivity measurements. Detection limit in gamma ray spectrometry is the smallest expectation value of the net counting rate that can be detected on given probabilities. The environmental test samples have been changed into ash using a suitable oven. The heating were made under controlled temperature to avoid the escape of some radionuclides such as radiocaesium. The ash samples were measured by high resolution gamma-ray spectrometry system. (author)

40 CFR Appendix B to Part 136 - Definition and Procedure for the Determination of the Method Detection Limit-Revision 1.11

Science.gov (United States)

2010-07-01

... calculated method detection limit. To insure that the estimate of the method detection limit is a good...) where: MDL = the method detection limit t(n-1,1- α=.99) = the students' t value appropriate for a 99... Determination of the Method Detection Limit-Revision 1.11 B Appendix B to Part 136 Protection of Environment...

Clinical Application of Picodroplet Digital PCR Technology for Rapid Detection of EGFR T790M in Next-Generation Sequencing Libraries and DNA from Limited Tumor Samples.

Science.gov (United States)

Borsu, Laetitia; Intrieri, Julie; Thampi, Linta; Yu, Helena; Riely, Gregory; Nafa, Khedoudja; Chandramohan, Raghu; Ladanyi, Marc; Arcila, Maria E

2016-11-01

Although next-generation sequencing (NGS) is a robust technology for comprehensive assessment of EGFR-mutant lung adenocarcinomas with acquired resistance to tyrosine kinase inhibitors, it may not provide sufficiently rapid and sensitive detection of the EGFR T790M mutation, the most clinically relevant resistance biomarker. Here, we describe a digital PCR (dPCR) assay for rapid T790M detection on aliquots of NGS libraries prepared for comprehensive profiling, fully maximizing broad genomic analysis on limited samples. Tumor DNAs from patients with EGFR-mutant lung adenocarcinomas and acquired resistance to epidermal growth factor receptor inhibitors were prepared for Memorial Sloan-Kettering-Integrated Mutation Profiling of Actionable Cancer Targets sequencing, a hybrid capture-based assay interrogating 410 cancer-related genes. Precapture library aliquots were used for rapid EGFR T790M testing by dPCR, and results were compared with NGS and locked nucleic acid-PCR Sanger sequencing (reference high sensitivity method). Seventy resistance samples showed 99% concordance with the reference high sensitivity method in accuracy studies. Input as low as 2.5 ng provided a sensitivity of 1% and improved further with increasing DNA input. dPCR on libraries required less DNA and showed better performance than direct genomic DNA. dPCR on NGS libraries is a robust and rapid approach to EGFR T790M testing, allowing most economical utilization of limited material for comprehensive assessment. The same assay can also be performed directly on any limited DNA source and cell-free DNA. Copyright © 2016 American Society for Investigative Pathology and the Association for Molecular Pathology. Published by Elsevier Inc. All rights reserved.

Limits of detection of americium-241 in air

International Nuclear Information System (INIS)

Bereznai, T.

1995-01-01

Seven semiconductor detectors with various characteristics (type, form, size, etc.) were tested and compared in gamma-spectrometric assays for Am-241 aerosols in air. The problem at hand (determining a low activity or attaining a set detection limit (approx. 2 mBq/m 3 ) as soon as possible after sampling) was solved best by a large-volume n-type detector with a Be-window. In addition to the detector parameters commonly used (energy resolution and effectiveness), the peak-to-background ratio and the background counting rate at the gamma-energy of the nuclide to be determined are important criteria influencing the choice of equipment. (orig.) [de

Detection of radiation-induced hydrocarbons in baked sponge cake prepared with irradiated liquid egg

International Nuclear Information System (INIS)

Schulzki, G.; Spiegelberg, A.; Boegl, K.W.; Schreiber, G.A.

1995-01-01

For identification of irradiated food, radiation-induced volatile hydrocarbons (HC) are determined by gas chromatography in the non-polar fraction of fat. However, in complex food matrices the detection is often disturbed by fat-associated compounds. On-line coupling of high performance liquid chromatography (LC) and gas chromatography (GC) is very efficient to remove such compounds from the HC fraction. The high sensitivity of this fast and efficient technique is demonstrated by the example of detection of radiation-induced HC in fat isolated from baked sponge cake which had been prepared with irradiated liquid egg. (Author)

In-house preparation of lectin panel and detection of Tn polyagglutination

Directory of Open Access Journals (Sweden)

Sudipta Sekhar Das

2015-01-01

Full Text Available Polyagglutination is a condition in which red cells are agglutinated by ABO-compatible adult human sera, but not by cord blood sera and may be acquired or inherited. Lectins are invaluable reagents in the investigation of red cells polyagglutination. We prepared in-house lectin panel and confirmed Tn polyagglutination in a pregnant lady. The lady was anemic and refused blood transfusion elsewhere due to serological discrepancy. We found ABO discrepancy and an incompatible minor cross-match in the initial investigation and suspected polyagglutination. Confirmation of polyagglutination was done using adult and cord sera. We then used the in-house lectin panels to detect the type of polyagglutination. The agglutination pattern with the various lectins was suggestive of Tn polyagglutination, which was further supported by the enzyme study. Most blood banks in India lack commercial lectin panels because of cost and procurement difficulty. Lectins play an important role in the diagnosis and differentiation of polyagglutination and immunohematological management of patient. The important and basic lectins can be prepared in-house using specific raw seeds following standardized protocol.

In-house preparation of lectin panel and detection of Tn polyagglutination.

Science.gov (United States)

Das, Sudipta Sekhar

2015-01-01

Polyagglutination is a condition in which red cells are agglutinated by ABO-compatible adult human sera, but not by cord blood sera and may be acquired or inherited. Lectins are invaluable reagents in the investigation of red cells polyagglutination. We prepared in-house lectin panel and confirmed Tn polyagglutination in a pregnant lady. The lady was anemic and refused blood transfusion elsewhere due to serological discrepancy. We found ABO discrepancy and an incompatible minor cross-match in the initial investigation and suspected polyagglutination. Confirmation of polyagglutination was done using adult and cord sera. We then used the in-house lectin panels to detect the type of polyagglutination. The agglutination pattern with the various lectins was suggestive of Tn polyagglutination, which was further supported by the enzyme study. Most blood banks in India lack commercial lectin panels because of cost and procurement difficulty. Lectins play an important role in the diagnosis and differentiation of polyagglutination and immunohematological management of patient. The important and basic lectins can be prepared in-house using specific raw seeds following standardized protocol.

Sample preparation for arsenic speciation analysis in baby food by generation of substituted arsines with atomic absorption spectrometry detection.

Science.gov (United States)

Huber, Charles S; Vale, Maria Goreti R; Dessuy, Morgana B; Svoboda, Milan; Musil, Stanislav; Dědina, Jiři

2017-12-01

A slurry sampling procedure for arsenic speciation analysis in baby food by arsane generation, cryogenic trapping and detection with atomic absorption spectrometry is presented. Several procedures were tested for slurry preparation, including different reagents (HNO 3 , HCl and tetramethylammonium hydroxide - TMAH) and their concentrations, water bath heating and ultrasound-assisted agitation. The best results for inorganic arsenic (iAs) and dimethylarsinate (DMA) were reached when using 3molL -1 HCl under heating and ultrasound-assisted agitation. The developed method was applied for the analysis of five porridge powder and six baby meal samples. The trueness of the method was checked with a certified reference material (CRM) of total arsenic (tAs), iAs and DMA in rice (ERM-BC211). Arsenic recoveries (mass balance) for all samples and CRM were performed by the determination of the tAs by inductively coupled plasma mass spectrometry (ICP-MS) after microwave-assisted digestion and its comparison against the sum of the results from the speciation analysis. The relative limits of detection were 0.44, 0.24 and 0.16µgkg -1 for iAs, methylarsonate and DMA, respectively. The concentrations of the most toxic arsenic species (iAs) in the analyzed baby food samples ranged between 4.2 and 99µgkg -1 which were below the limits of 300, 200 and 100µgkg -1 set by the Brazilian, Chinese and European legislation, respectively. Copyright © 2017 Elsevier B.V. All rights reserved.

Detection and grading of dAVF: prospects and limitations of 3T MRI.

Science.gov (United States)

Bink, Andrea; Berkefeld, Joachim; Wagner, Marlies; You, Se-Jong; Ackermann, Hanns; Lorenz, Matthias W; Senft, Christian; du Mesnil de Rochemont, Richard

2012-02-01

DSA is currently the criterion standard for the assessment of dural arteriovenous fistulas (dAVF). Recently, evolving MRA techniques have emerged as a non-invasive alternative. The aim of this study is to assess the value of 3 T MRI in detecting and describing dAVF and to determine whether MRI can replace DSA as diagnostic procedure. A total of 19 patients with dAVF and 19 without dAVF underwent the same MRI protocol, including 3D time-of-flight MRA and time-resolved contrast-enhanced MRA. The images were evaluated retrospectively by three independent readers with different levels of experience blinded to clinical information. The readers assessed the presence, the site, the venous drainage and the feeders of dAVF. Sensitivity, specificity, accuracy, intertechnique and interobserver agreements were calculated. DAVF can be detected with high sensitivity, specificity and accuracy by experienced and also by less experienced readers. However, MRI has limitations when used for grading and evaluation of the angioarchitecture of the dAVF. Different experience, the limited resolution of MRI and its inability to selectively display arteries were the reasons for these limitations. With MRI dAVF can be detected reliably. Nevertheless, at present MRI can not fully replace DSA, especially for treatment planning.

Limits of detection in instrumental neutron activation analysis

International Nuclear Information System (INIS)

Guinn, V.P.

1990-01-01

Lower limits of detection (LLODs), frequently referred to simply as limits of detection and abbreviated as LODs, often appear in the literature of analytical chemistry - for numerous different methods of elemental and/or molecular analysis. In this chapter, one particular method of quantitative elemental analysis, that of instrumental neutron activation analysis (INAA), is the subject discussed, with reference to LODs. Particularly in the literature of neutron activation analysis (NAA), many tables of 'interference-free' NAA LODs are available. Not all of these are of much use, because (1) for many the definition used for LOD is not clear, or reasonable, (2) for many, the analysis conditions used are not clearly specified, and (3) for many, the analysis conditions used are specified, but not very practicable for most laboratories. For NAA work, such tables of interference-free LODs are, in any case, only applicable to samples in which, at the time of counting, only one radionuclide is present to any significant extent in the activated sample. It is important to note that tables of INAA LODs, per se, do not exist - since the LOD for a given element, under stated analysis conditions, can vary by orders of magnitude, depending on the elemental composition of the matrix in which it is present. For any given element, its INAA LOD will always be as large as, and usually much larger than, its tabulated 'interference-free' NAA LOD - how much larger depending upon the elemental composition of the matrix in which it is present. As discussed in this chapter, however, an INAA computer program exists that can calculate realistic INAA LODs for any elements of interest, in any kind of specified sample matrix, under any given set of analysis conditions

Gravitational wave detection using laser interferometry beyond the standard quantum limit

Science.gov (United States)

Heurs, M.

2018-05-01

Interferometric gravitational wave detectors (such as advanced LIGO) employ high-power solid-state lasers to maximize their detection sensitivity and hence their reach into the universe. These sophisticated light sources are ultra-stabilized with regard to output power, emission frequency and beam geometry; this is crucial to obtain low detector noise. However, even when all laser noise is reduced as far as technically possible, unavoidable quantum noise of the laser still remains. This is a consequence of the Heisenberg Uncertainty Principle, the basis of quantum mechanics: in this case, it is fundamentally impossible to simultaneously reduce both the phase noise and the amplitude noise of a laser to arbitrarily low levels. This fact manifests in the detector noise budget as two distinct noise sources-photon shot noise and quantum radiation pressure noise-which together form a lower boundary for current-day gravitational wave detector sensitivities, the standard quantum limit of interferometry. To overcome this limit, various techniques are being proposed, among them different uses of non-classical light and alternative interferometer topologies. This article explains how quantum noise enters and manifests in an interferometric gravitational wave detector, and gives an overview of some of the schemes proposed to overcome this seemingly fundamental limitation, all aimed at the goal of higher gravitational wave event detection rates. This article is part of a discussion meeting issue `The promises of gravitational-wave astronomy'.

78 FR 38024 - Magnolia LNG, LLC; Liquefied Natural Gas Limited; Notice of Intent To Prepare an Environmental...

Science.gov (United States)

2013-06-25

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. PF13-9-000] Magnolia LNG, LLC; Liquefied Natural Gas Limited; Notice of Intent To Prepare an Environmental Impact Statement for the Planned Magnolia Liquefied Natural Gas Project, Request for Comments on Environmental Issues, and Notice of Public Scoping Meeting The staff of...

Efficient sample preparation method based on solvent-assisted dispersive solid-phase extraction for the trace detection of butachlor in urine and waste water samples.

Science.gov (United States)

Aladaghlo, Zolfaghar; Fakhari, Alireza; Behbahani, Mohammad

2016-10-01

In this work, an efficient sample preparation method termed solvent-assisted dispersive solid-phase extraction was applied. The used sample preparation method was based on the dispersion of the sorbent (benzophenone) into the aqueous sample to maximize the interaction surface. In this approach, the dispersion of the sorbent at a very low milligram level was achieved by inserting a solution of the sorbent and disperser solvent into the aqueous sample. The cloudy solution created from the dispersion of the sorbent in the bulk aqueous sample. After pre-concentration of the butachlor, the cloudy solution was centrifuged and butachlor in the sediment phase dissolved in ethanol and determined by gas chromatography with flame ionization detection. Under the optimized conditions (solution pH = 7.0, sorbent: benzophenone, 2%, disperser solvent: ethanol, 500 μL, centrifuged at 4000 rpm for 3 min), the method detection limit for butachlor was 2, 3 and 3 μg/L for distilled water, waste water, and urine sample, respectively. Furthermore, the preconcentration factor was 198.8, 175.0, and 174.2 in distilled water, waste water, and urine sample, respectively. Solvent-assisted dispersive solid-phase extraction was successfully used for the trace monitoring of butachlor in urine and waste water samples. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Extending the detection limit of dopants for focused ion beam prepared semiconductor specimens examined by off-axis electron holography

DEFF Research Database (Denmark)

Cooper, David; Rivallin, Pierrette; Hartmann, Jean-Michel

2009-01-01

Silicon specimens containing p-n junctions have been prepared for examination by off-axis electron holography using focused ion beam (FIB) milling. FIB milling modifies the surfaces of the specimens due to gallium implantation and the creation of defects which has the effect of reducing the active...

Novel Sample Preparation Method for Safe and Rapid Detection of Bacillus anthracis Spores in Environmental Powders and Nasal Swabs

OpenAIRE

Luna, Vicki A.; King, Debra; Davis, Carisa; Rycerz, Tony; Ewert, Matthew; Cannons, Andrew; Amuso, Philip; Cattani, Jacqueline

2003-01-01

Bacillus anthracis spores have been used as a biological weapon in the United States. We wanted to develop a safe, rapid method of sample preparation that provided safe DNA for the detection of spores in environmental and clinical specimens. Our method reproducibly detects B. anthracis in samples containing

One-step electrochemical deposition of a graphene-ZrO₂ nanocomposite: Preparation, characterization and application for detection of organophosphorus agents

Energy Technology Data Exchange (ETDEWEB)

Du, Dan; Liu, Juan; Zhang, Xiao-Yan; Cui, Xiao-Li; Lin, Yuehe

2011-04-27

This paper described the preparation, characterization, and electrochemical properties of a graphene-ZrO₂ nanocomposite (GZN) and its application for both the enrichment and detection of methyl parathion (MP). GZN was fabricated using electrochemical deposition and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), which showed the successful formation of nanocomposites. Due to the strong affinity to the phosphoric group and the fast electron-transfer kinetics of GZN, both the extraction and electrochemical detection of organophosphorus (OP) agents at the same GZN modified electrochemical sensor was possible. The combination of solid-phase extraction and stripping voltammetric analysis allowed fast, sensitive, and selective determination of MP in garlic samples. The stripping response was highly linear over the MP concentrations ranging from 0.5 ng mL^-1 to 100 ng mL^-1, with a detection limit of 0.1 ng mL^-1. This new nanocomposite-based electrochemical sensor provides an opportunity to develop a field-deployable, sensitive, and quantitative method for monitoring exposure to OPs.

Investigation of a gamma sensitive Ge-detector with Marinelligeometry. Determination of the detection limits

International Nuclear Information System (INIS)

Moricz, P.

1984-01-01

Different Marinelli geometries have been compared with a 180 ml standard plastic breaker geometry as a reference. The results show that the Marinelli geometries are the best. E.g. the detection limit with a Marinelli geometry of 0.5 l is only half compared with the limit when the standard geometry is used. (Edv)

Preparation of genosensor for detection of specific DNA sequence of the hepatitis B virus

Science.gov (United States)

Honorato Castro, Ana C.; França, Erick G.; de Paula, Lucas F.; Soares, Marcia M. C. N.; Goulart, Luiz R.; Madurro, João M.; Brito-Madurro, Ana G.

2014-09-01

An electrochemical genosensor was constructed for detection of specific DNA sequence of the hepatitis B virus, based on graphite electrodes modified with poly(4-aminophenol) and incorporating a specific oligonucleotide probe. The modified electrode containing the probe was evaluated by differential pulse voltammetry, before and after incubation with the complementary oligonucleotide target. Detection was performed by monitoring oxidizable DNA bases (direct detection) or using ethidium bromide as indicator of the hybridization process (indirect detection). The device showed a detection limit for the oligonucleotide target of 2.61 nmol L-1. Indirect detection using ethidium bromide was promising in discriminating mismatches, which is a very desirable attribute for detection of disease-related point mutations. In addition, it was possible to observe differences between hybridized and non-hybridized surfaces by atomic force microscopy.

Trace element analysis by EPMA in geosciences: detection limit, precision and accuracy

Science.gov (United States)

Batanova, V. G.; Sobolev, A. V.; Magnin, V.

2018-01-01

Use of the electron probe microanalyser (EPMA) for trace element analysis has increased over the last decade, mainly because of improved stability of spectrometers and the electron column when operated at high probe current; development of new large-area crystal monochromators and ultra-high count rate spectrometers; full integration of energy-dispersive / wavelength-dispersive X-ray spectrometry (EDS/WDS) signals; and the development of powerful software packages. For phases that are stable under a dense electron beam, the detection limit and precision can be decreased to the ppm level by using high acceleration voltage and beam current combined with long counting time. Data on 10 elements (Na, Al, P, Ca, Ti, Cr, Mn, Co, Ni, Zn) in olivine obtained on a JEOL JXA-8230 microprobe with tungsten filament show that the detection limit decreases proportionally to the square root of counting time and probe current. For all elements equal or heavier than phosphorus (Z = 15), the detection limit decreases with increasing accelerating voltage. The analytical precision for minor and trace elements analysed in olivine at 25 kV accelerating voltage and 900 nA beam current is 4 - 18 ppm (2 standard deviations of repeated measurements of the olivine reference sample) and is similar to the detection limit of corresponding elements. To analyse trace elements accurately requires careful estimation of background, and consideration of sample damage under the beam and secondary fluorescence from phase boundaries. The development and use of matrix reference samples with well-characterised trace elements of interest is important for monitoring and improving of the accuracy. An evaluation of the accuracy of trace element analyses in olivine has been made by comparing EPMA data for new reference samples with data obtained by different in-situ and bulk analytical methods in six different laboratories worldwide. For all elements, the measured concentrations in the olivine reference sample

Ultrasensitive and simultaneous detection of hydroquinone, catechol and resorcinol based on the electrochemical co-reduction prepared Au-Pd nanoflower/reduced graphene oxide nanocomposite

International Nuclear Information System (INIS)

Chen, Yuan; Liu, Xiaoying; Zhang, Si; Yang, Liuqing; Liu, Meiling; Zhang, Youyu; Yao, Shouzhuo

2017-01-01

A simple and efficient eletrochemical sensing platform for simultaneous detection of hydroquinone (HQ), catechol (CC) and resorcinol (RC) based on the Au-Pd bimetallic and graphene is described in this paper. The Au-Pd reduced graphene oxide (Au-Pd NF/rGO) was prepared by the electrochemical co-reduction deposition via cyclic voltammetry method (CV). The Au-Pd NF/rGO nanocomposite was examined by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and electrochemical methods CV and differential pulse voltammety (DPV) study showed that the three dihydroxybenzene isomers can be catalytically oxidized and discriminated simultaneously on the Au-Pd NF/rGO/GCE. The presence of Pd makes the performance of the sensor superior to that of in the absence of it. Owing to the integrated superior conductivity and excellent catalytic property of Au-Pd NF/rGO, the sensitive and simultaneous detection of HQ, CC and RC was realized in the individual or triple-components solution based on the as proposed Au-Pd NF/rGO/GCE, which shows wide linear range and low detection limit. The detection of them in tap water, river water and lake water were also successfully performed and good recovery was obtained.

Preparation, characterization and evaluation of water-soluble L-cysteine-capped-CdS nanoparticles as fluorescence probe for detection of Hg(II) in aqueous solution

International Nuclear Information System (INIS)

Cai Zhaoxia; Yang Hong; Zhang Yi; Yan Xiuping

2006-01-01

Water-soluble L-cysteine-capped-CdS nanoparticles were prepared in aqueous solution at room temperature through a straightforward one-pot process by using safe and low-cost inorganic salts as precursors, and characterized by transmission electron microscopy, X-ray diffraction spectrometry, Fourier transform infrared spectrometry, spectrofluorometry and ultraviolet-visible spectrometry. The prepared L-cysteine-capped-CdS nanoparticles were evaluated as fluorescence probe for Hg(II) detection. The fluorescence quenching of the L-cysteine-capped-CdS nanoparticles depended on the concentration and pH of Hg(II) solution. Maximum fluorescence quenching was observed at pH 7.4 with the excitation and emission wavelengths of 360 nm and 495 nm, respectively. Quenching of its fluorescence due to Hg(II) at the 20 nmol l -1 level was unaffected by the presence of 5 x 10 6 -fold excesses of Na(I) and K(I), 5 x 10 5 -fold excesses of Mg(II), 5 x 10 4 -fold excesses of Ca(II), 500-fold excesses of Al(III), 91-fold excesses of Mn(II), 23.5-fold excesses of Pb(II), 25-fold excesses of Fe(III), 25-fold excesses of Ag(I), 8.5-fold excesses of Ni(II) and 5-fold excesses of Cu(II). Under optimal conditions, the quenched fluorescence intensity increased linearly with the concentration of Hg(II) ranging from 16 nmol l -1 to 112 nmol l -1 . The limit of detection for Hg(II) was 2.4 nmol l -1 . The developed method was applied to the detection of trace Hg(II) in aqueous solutions

Detection tube with composite carrier for detection of phosgene and diphosgene in air

Directory of Open Access Journals (Sweden)

Pitschmann Vladimír

2012-01-01

Full Text Available A new highly sensitive detection tube for measurement of concentration of phosgene and diphosgene in air has been developed. The detection is based on chemical reaction of 4-(p-nitrobenzylpyridine and N-phenylbenzylamine which with phosgene (diphosgene give characteristic red methine dye. As a carrier serves spherical granules (pellets of composite material prepared by granulation of microcrystalline cellulose with MgO. This new indication filling is stable, resistant to interferences and climatic influences. The detection limit (0.05 mg.m-3 meets the requirements for conducting hygienic checks of air quality in the workplace environment. In addition, the tube allows a prolonged and continuous monitoring of phosgene and diphosgene in air for at least 240 minutes.

Application of Statistical Methods to Activation Analytical Results near the Limit of Detection

DEFF Research Database (Denmark)

Heydorn, Kaj; Wanscher, B.

1978-01-01

Reporting actual numbers instead of upper limits for analytical results at or below the detection limit may produce reliable data when these numbers are subjected to appropriate statistical processing. Particularly in radiometric methods, such as activation analysis, where individual standard...... deviations of analytical results may be estimated, improved discrimination may be based on the Analysis of Precision. Actual experimental results from a study of the concentrations of arsenic in human skin demonstrate the power of this principle....

TXRF 'measurements' of concentration distribution below the detection limit

International Nuclear Information System (INIS)

Kubala-Kukus, A.; Banas, D.; Braziewicz, J.; Majewska, U.; Mrowczynski, S.; Pajek, M.

2000-01-01

We demonstrate that a shape of the concentration distribution of the element in a set of samples, as measured by the TXRF method, can be determined even for the concentrations below the detection limit (DL). This can be done, when the measurements reporting the concentration below DL level are included properly in the analysis of the results. The method developed for such correction is presented and discussed. It is demonstrated that this correction is particularly important when the studied concentrations are close to the DL level of the method, which is a common case for TXRF. In the paper a precision of the developed correction is discussed in details, by using the results of numerical simulations of experiments for different concentration distributions and number of performed measurements. It is demonstrated that the factor, which limits the accuracy of the correction, is the number of measurements, not the correction procedure itself. The applicability and importance of the developed correction is demonstrated for routine TXRF analysis of different types of samples of bio-medical interest. (author)

Investigation on feasibility and detection limits for determination of coating film thickness by neutron activation analysis

International Nuclear Information System (INIS)

Yao Maoying; Xu Jiayun; Zhang Dida; Yang Zunyong; Yao Zhenqiang; Wang Mingqiu; Gao Dangzhong

2010-01-01

A method for the determination of coating film thickness by neutron activation was proposed in this paper. After Au, Al and Cu et al.films were activated with a Am-Be neutron source, the characteristic γ-rays emitted by the activated nuclides in the films were counted with a HPGe γ spectrometer. The detection limits of film thickness by using a nuclear reactor neutron source were deduced on the basis of the γ-ray counts and the Monte-Carlo simulated detection efficiencies. The possible detection limits are typically 4-5 orders of magnitude better than those by fluorescent X-ray method, which is currently widely used to determine coating film thickness. (authors)

Preparing a scientific manuscript in Linux: Today's possibilities and limitations.

Science.gov (United States)

Tchantchaleishvili, Vakhtang; Schmitto, Jan D

2011-10-22

Increasing number of scientists are enthusiastic about using free, open source software for their research purposes. Authors' specific goal was to examine whether a Linux-based operating system with open source software packages would allow to prepare a submission-ready scientific manuscript without the need to use the proprietary software. Preparation and editing of scientific manuscripts is possible using Linux and open source software. This letter to the editor describes key steps for preparation of a publication-ready scientific manuscript in a Linux-based operating system, as well as discusses the necessary software components. This manuscript was created using Linux and open source programs for Linux.

Discuss the technology for decrease the detection limit of NaI(Tl) gamma spectrometer

International Nuclear Information System (INIS)

Guo Xiaobin; Qu Guopu; Liu Zhiying; Wang Hongyan; Wang Lieming

2011-01-01

The radioelement species is complex and quantity is few after nuclear explosion, thus it is hard to tell the difference when using the Nal (TI) Gamma spectrometer detection due to several kinds of the peak of nuclide overlapped in the scattering region. So there is a high demand for spectrometer stability, energy resolution, solution spectrum and minimum detective activity. The paper analysed the influenced factors to Nal (TI) Gamma spectrometer and the measures of detection limit decrease by experiments and MCNP simulation, which proposed the methods to reduce background through shielding in order to improve minimum detective activity. The experiment shows that choosing reasonable shielding can reduce the background effectively and improve the spectrometer low level radioactive detect ability. (authors)

Evaluation of a single-item screening question to detect limited health literacy in peritoneal dialysis patients.

Science.gov (United States)

Jain, Deepika; Sheth, Heena; Bender, Filitsa H; Weisbord, Steven D; Green, Jamie A

2014-01-01

Studies have shown that a single-item question might be useful in identifying patients with limited health literacy. However, the utility of the approach has not been studied in patients receiving maintenance peritoneal dialysis (PD). We assessed health literacy in a cohort of 31 PD patients by administering the Rapid Estimate of Adult Literacy in Medicine (REALM) and a single-item health literacy (SHL) screening question "How confident are you filling out medical forms by yourself?" (Extremely, Quite a bit, Somewhat, A little bit, or Not at all). To determine the accuracy of the single-item question for detecting limited health literacy, we performed sensitivity and specificity analyses of the SHL and plotted the area under the receiver operating characteristic (AUROC) curve using the REALM as a reference standard. Using a cut-off of "Somewhat" or less confident, the sensitivity of the SHL for detecting limited health literacy was 80%, and the specificity was 88%. The positive likelihood ratio was 6.9. The SHL had an AUROC of 0.79 (95% confidence interval: 0.52 to 1.00). Our results show that the SHL could be effective in detecting limited health literacy in PD patients.

Continuous preparation of Fe3O4 nanoparticles through Impinging Stream-Rotating Packed Bed reactor and their electrochemistry detection toward heavy metal ions

International Nuclear Information System (INIS)

Fan, Hong-Lei; Zhou, Shao-Feng; Gao, Jing; Liu, You-Zhi

2016-01-01

We reported the continuous preparation and electrochemical behavior toward heavy metal ions of the Fe 3 O 4 nanoparticles (Fe 3 O 4 NPs). This Fe 3 O 4 NPs were fabricated through a novel Impinging Stream-Rotating Packed Bed reactor with a high production rate of 2.23 kg/hour. The as-prepared Fe 3 O 4 NPs were quasi-spherical with a mean diameter of about 10 nm and shown the characteristics of superparamagnetism with the saturated magnetization of 60.5 emu/g. The electrochemical characterization of the as-prepared Fe 3 O 4 NPs toward heavy metal ions were evaluated using square wave anodic stripping voltammetry (SWASV) analysis. The results indicated that the modified electrode could be used to individual detection of Pb(II), Cu(II), Hg(II) and Cd(II). In particular, the modified electrode exhibited the selective detection toward Pb(II) with higher sensitivity of 14.9 μA/μM, while the response to Cu(II), Hg(II) and Cd(II) were negligible. Besides, the modified electrode shown good stability and potential practical applicability in the electrochemical determination of Pb(II). This above results offered a simple method for continuous preparation sensing materials in the application field of electrochemical detection of toxic metal ions through the technology of process intensification. - Highlights: • Fe 3 O 4 nanoparticles were continuous prepared through IS-RPB reactor. • The Fe 3 O 4 nanoparticles showed selective detection of heavy metal ions. • It exhibited favorable sensitivity (14.9 μA μM −1 ) and LOD (0.119 μM) for Pb(II). • The as-prepared nanoparticles showed favorable potential application.

Preparation of gold nanoparticles-agarose gel composite and its application in SERS detection

Science.gov (United States)

Ma, Xiaoyuan; Xia, Yu; Ni, Lili; Song, Liangjing; Wang, Zhouping

2014-03-01

Agarose gel/gold nanoparticles hybrid was prepared by adding gold nanoparticles to preformed agarose gel. Nanocomposite structures and properties were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and UV-Vis-NIR absorption spectroscopy. Based on the swelling-contraction characteristics of agarose gel and the adjustable localized surface plasmon resonance (LSPR) of the gold nanoparticles, the nanocomposites were used as surface enhanced Raman scattering (SERS) substrate to detect the Raman signal molecules (NBA, MBA, 1NAT). Results revealed that the porous structure of the agarose gel provided a good carrier for the enrichment of the gold nanoparticles. The gold nanoparticles dynamic hot-spot effect arising from the agarose gel contraction loss of water in the air greatly enhanced the Raman signal. Furthermore, the gel could be cleaned with washing solution and recycling could be achieved for Raman detection.

RCRA materials analysis by laser-induced breakdown spectroscopy: Detection limits in soils

International Nuclear Information System (INIS)

Koskelo, A.; Cremers, D.A.

1994-01-01

The goal of the Technical Task Plan (TTP) that this report supports is research, development, testing and evaluation of a portable analyzer for RCRA and other metals. The instrumentation to be built will be used for field-screening of soils. Data quality is expected to be suitable for this purpose. The data presented in this report were acquired to demonstrate the detection limits for laser-induced breakdown spectroscopy (LIBS) of soils using instrument parameters suitable for fieldable instrumentation. The data are not expected to be the best achievable with the high pulse energies available in laboratory lasers. The report presents work to date on the detection limits for several elements in soils using LIBS. The elements targeted in the Technical Task Plan are antimony, arsenic, beryllium, cadmium, chromium, lead, selenium, and zirconium. Data for these elements are presented in this report. Also included are other data of interest to potential customers for the portable LIBS apparatus. These data are for barium, mercury, cesium and strontium. Data for uranium and thorium will be acquired during the tasks geared toward mixed waste characterization

Power-limited low-thrust trajectory optimization with operation point detection

Science.gov (United States)

Chi, Zhemin; Li, Haiyang; Jiang, Fanghua; Li, Junfeng

2018-06-01

The power-limited solar electric propulsion system is considered more practical in mission design. An accurate mathematical model of the propulsion system, based on experimental data of the power generation system, is used in this paper. An indirect method is used to deal with the time-optimal and fuel-optimal control problems, in which the solar electric propulsion system is described using a finite number of operation points, which are characterized by different pairs of thruster input power. In order to guarantee the integral accuracy for the discrete power-limited problem, a power operation detection technique is embedded in the fourth-order Runge-Kutta algorithm with fixed step. Moreover, the logarithmic homotopy method and normalization technique are employed to overcome the difficulties caused by using indirect methods. Three numerical simulations with actual propulsion systems are given to substantiate the feasibility and efficiency of the proposed method.

Deposition and detection of particles during integrated circuit manufacturing

NARCIS (Netherlands)

Wali, F.; Knotter, D. Martin; Kelly, John J.; Kuper, F.G.

2006-01-01

Abstract—Deposition mechanism of silica particles on silicon wafers was investigated by depositing specially prepared mono-dispersed particles (mean diameter = 330 nm). To measure particles of the size below the detection limit of our particle measurement tools, silica particles with luminance core

STATISTICAL METHODS FOR ENVIRONMENTAL APPLICATIONS USING DATA SETS WITH BELOW DETECTION LIMIT OBSERVATIONS AS INCORPORTED IN PROUCL 4.0

Science.gov (United States)

Nondetect (ND) or below detection limit (BDL) results cannot be measured accurately, and, therefore, are reported as less than certain detection limit (DL) values. However, since the presence of some contaminants (e.g., dioxin) in environmental media may pose a threat to human he...

CARIES DETECTION WITH LASER FLUORESCENCE DEVICES. LIMITATIONS OF THEIR USE

Directory of Open Access Journals (Sweden)

Andreas Spaveras

2017-03-01

Data synthesis: DD and DDPen are useful devices for caries detection on the occlusal tooth surfaces. Their main advantages are the very high reproducibility of measurements (>0.90, the ease of handling and the quantification and monitoring capacity. Their main limitations are the relatively low specificity for enamel lesions, the necessity of unstained surfaces and absence of plaque and pastes during measurements and the absence of a universal, clinically functional calibration value (COV. Conclusion: Further studies are required for more reliable data analysis and clinical interpretation of the relevant results.

Label-free virus detection using silicon photonic microring resonators.

Science.gov (United States)

McClellan, Melinda S; Domier, Leslie L; Bailey, Ryan C

2012-01-15

Viruses represent a continual threat to humans through a number of mechanisms, which include disease, bioterrorism, and destruction of both plant and animal food resources. Many contemporary techniques used for the detection of viruses and viral infections suffer from limitations such as the need for extensive sample preparation or the lengthy window between infection and measurable immune response, for serological methods. In order to develop a method that is fast, cost-effective, and features reduced sample preparation compared to many other virus detection methods, we report the application of silicon photonic microring resonators for the direct, label-free detection of intact viruses in both purified samples as well as in a complex, real-world analytical matrix. As a model system, we demonstrate the quantitative detection of Bean pod mottle virus, a pathogen of great agricultural importance, with a limit of detection of 10 ng/mL. By simply grinding a small amount of leaf sample in buffer with a mortar and pestle, infected leaves can be identified over a healthy control with a total analysis time of less than 45 min. Given the inherent scalability and multiplexing capability of the semiconductor-based technology, we feel that silicon photonic microring resonators are well-positioned as a promising analytical tool for a number of viral detection applications. Copyright © 2011 Elsevier B.V. All rights reserved.

Proposal for a methodology for the determination of the Detection Limit: Case of bulks detector for the Chlorothalonil

International Nuclear Information System (INIS)

Gonzalez G, J.; Parra M, C.M.; Romero R, R.M.

1998-01-01

As it usually found in the literature, the Lower Detection Limit for an analytical method is obtained by means of a simple statistical exercise whose value is seldom attained in practice. For this reason a method was designed for achieving a Practical Lower Detection Limit for the lowest concentration of the compound that could be detected, S= 2 R, with a probability of at least, 0.90. A methodological design was formulated to get a Practical Lower Detection Limit that is not timed consuming for the analyst. It is presented using an example and, additionally its benefits are discussed versus the unattainable values that are obtained by the traditional use of the standard deviation of a series of measurements of the compound at concentrations near zero, which is then multiplied by the t student for a one tailed test for n-1 degrees of freedom

Preparation of novel silver nanoplates/graphene composite and their application in vanillin electrochemical detection.

Science.gov (United States)

Huang, Linhong; Hou, Keyu; Jia, Xiao; Pan, Haibo; Du, Min

2014-05-01

Hexagonal Ag nanoplates (NPs) were synthesized by polyvinylpyrrolidone (PVP) and trisodium citrate (TSC) which selectively absorbed to Ag (100) and Ag (111) surfaces, then were anchored to graphene (GN) to form novel Ag NPs/GN composite. The thickness of Ag NPs is ~4 nm and the length is 18-66 nm. Transmission electron microscopy (TEM) image shows that the plates are f-c-c crystals containing {111} facets on their two planar surfaces. Zeta potential indicated that the surface of Ag NPs/GN is negatively charged while vanillin is positively charged. Thus Ag NPs/GN modified on glass carbon electrodes (GCE) allowed abundant adsorption for vanillin and electron transfer between vanillin and Ag NPs/GN/GCE. Square wave voltammetry (SWV) results indicated that the over potential on Ag NPs/GN/GCE negatively shifts 52 mV than that on Ag NPs/GCE. Ag NPs/GN with enhanced surface area and good conductivity exhibited an excellent electrocatalytic activity toward the oxidation of vanillin. The corresponding linear range was estimated to be from 2 to 100 μM (R(2)=0.998), and the detection limit is 3.32×10(-7) M (S/N=3). The as-prepared vanillin sensor exhibits good selectivity and potential application in practical vanillin determination. Copyright © 2014 Elsevier B.V. All rights reserved.

Detection limits should be a thing of the past in gamma-ray spectrometry in general as well as in neutron activation analysis

NARCIS (Netherlands)

Blaauw, Menno

2016-01-01

In gamma-ray spectrometry with high-resolution detectors, full-energy peaks are often to be detected by a peak-search algorithm, with a threshold for detection. Detection limits can be derived from this. Detection limits are often computed along with measured activities or concentrations. When an

Optimising Mycobacterium tuberculosis detection in resource limited settings.

Science.gov (United States)

Alfred, Nwofor; Lovette, Lawson; Aliyu, Gambo; Olusegun, Obasanya; Meshak, Panwal; Jilang, Tunkat; Iwakun, Mosunmola; Nnamdi, Emenyonu; Olubunmi, Onuoha; Dakum, Patrick; Abimiku, Alash'le

2014-03-03

The light-emitting diode (LED) fluorescence microscopy has made acid-fast bacilli (AFB) detection faster and efficient although its optimal performance in resource-limited settings is still being studied. We assessed the optimal performances of light and fluorescence microscopy in routine conditions of a resource-limited setting and evaluated the digestion time for sputum samples for maximum yield of positive cultures. Cross-sectional study. Facility-based involving samples of routine patients receiving tuberculosis treatment and care from the main tuberculosis case referral centre in northern Nigeria. The study included 450 sputum samples from 150 new patients with clinical diagnosis of pulmonary tuberculosis. The 450 samples were pooled into 150 specimens, examined independently with mercury vapour lamp (FM), LED CysCope (CY) and Primo Star iLED (PiLED) fluorescence microscopies, and with the Ziehl-Neelsen (ZN) microscopy to assess the performance of each technique compared with liquid culture. The cultured specimens were decontaminated with BD Mycoprep (4% NaOH-1% NLAC and 2.9% sodium citrate) for 10, 15 and 20 min before incubation in Mycobacterium growth incubator tube (MGIT) system and growth examined for acid-fast bacilli (AFB). Of the 150 specimens examined by direct microscopy: 44 (29%), 60 (40%), 49 (33%) and 64 (43%) were AFB positive by ZN, FM, CY and iLED microscopy, respectively. Digestion of sputum samples for 10, 15 and 20 min yielded mycobacterial growth in 72 (48%), 81 (54%) and 68 (45%) of the digested samples, respectively, after incubation in the MGIT system. In routine laboratory conditions of a resource-limited setting, our study has demonstrated the superiority of fluorescence microscopy over the conventional ZN technique. Digestion of sputum samples for 15 min yielded more positive cultures.

Estimation of the limit of detection with a bootstrap-derived standard error by a partly non-parametric approach. Application to HPLC drug assays

DEFF Research Database (Denmark)

Linnet, Kristian

2005-01-01

Bootstrap, HPLC, limit of blank, limit of detection, non-parametric statistics, type I and II errors......Bootstrap, HPLC, limit of blank, limit of detection, non-parametric statistics, type I and II errors...

Detection of cytomegalovirus in blood donors by PCR using the digene SHARP signal system assay: effects of sample preparation and detection methodology.

OpenAIRE

Krajden, M; Shankaran, P; Bourke, C; Lau, W

1996-01-01

Cytomegalovirus (CMV) is an important cause of transfusion-associated morbidity and mortality; however, only 0.4 to 12% of the blood products obtained from seropositive blood donors transmit infection. The effects of three commercially available whole-blood sample preparation kits on the detection of CMV PCR products by a semiquantitative adaptation of the Digene SHARP Signal System Assay (DSSSA) in samples from volunteer blood donors was assessed. Of 101 samples from seropositive blood donor...

Detection limits for real-time source water monitoring using indigenous freshwater microalgae

Energy Technology Data Exchange (ETDEWEB)

Rodriguez Jr, Miguel [ORNL; Greenbaum, Elias [ORNL

2009-01-01

This research identified toxin detection limits using the variable fluorescence of naturally occurring microalgae in source drinking water for five chemical toxins with different molecular structures and modes of toxicity. The five chemicals investigated were atrazine, Diuron, paraquat, methyl parathion, and potassium cyanide. Absolute threshold sensitivities of the algae for detection of the toxins in unmodified source drinking water were measured. Differential kinetics between the rate of action of the toxins and natural changes in algal physiology, such as diurnal photoinhibition, are significant enough that effects of the toxin can be detected and distinguished from the natural variance. This is true even for physiologically impaired algae where diminished photosynthetic capacity may arise from uncontrollable external factors such as nutrient starvation. Photoinhibition induced by high levels of solar radiation is a predictable and reversible phenomenon that can be dealt with using a period of dark adaption of 30 minutes or more.

Dispersive detection of radio-frequency-dressed states

Science.gov (United States)

Jammi, Sindhu; Pyragius, Tadas; Bason, Mark G.; Florez, Hans Marin; Fernholz, Thomas

2018-04-01

We introduce a method to dispersively detect alkali-metal atoms in radio-frequency-dressed states. In particular, we use dressed detection to measure populations and population differences of atoms prepared in their clock states. Linear birefringence of the atomic medium enables atom number detection via polarization homodyning, a form of common path interferometry. In order to achieve low technical noise levels, we perform optical sideband detection after adiabatic transformation of bare states into dressed states. The balanced homodyne signal then oscillates independently of field fluctuations at twice the dressing frequency, thus allowing for robust, phase-locked detection that circumvents low-frequency noise. Using probe pulses of two optical frequencies, we can detect both clock states simultaneously and obtain population difference as well as the total atom number. The scheme also allows for difference measurements by direct subtraction of the homodyne signals at the balanced detector, which should technically enable quantum noise limited measurements with prospects for the preparation of spin squeezed states. The method extends to other Zeeman sublevels and can be employed in a range of atomic clock schemes, atom interferometers, and other experiments using dressed atoms.

In situ Silver Spot Preparation and on-Plate Surface-Enhanced Raman Scattering Detection in Thin Layer Chromatography Separation

Science.gov (United States)

Herman, K.; Mircescu, N. E.; Szabo, L.; Leopold, L. F.; Chiş, V.; Leopold, N.

2013-05-01

An improved approach for surface-enhanced Raman scattering (SERS) detection of mixture constituents after thin layer chromatography (TLC) separation is presented. A SERS active silver substrate was prepared under open air conditions, directly on the thin silica film by photo-reduction of silver nitrate, allowing the detection of binary mixtures of cresyl violet, bixine, crystal violet, and Cu(II) complex of 4-(2-pyridylazo)resorcinol. The recorded SERS spectrum provides a unique spectral fingerprint for each molecule; therefore the use of analyte standards is avoided, thus rendering the presented procedure advantageous compared to the conventional detection methodology in TLC.

Limits of 2D-TCA in detecting BOLD responses to epileptic activity.

Science.gov (United States)

Khatamian, Yasha Borna; Fahoum, Firas; Gotman, Jean

2011-05-01

Two-dimensional temporal clustering analysis (2D-TCA) is a relatively new functional MRI (fMRI) based technique that breaks blood oxygen level dependent activity into separate components based on timing and has shown potential for localizing epileptic activity independently of electroencephalography (EEG). 2D-TCA has only been applied to detect epileptic activity in a few studies and its limits in detecting activity of various forms (i.e. activation size, amplitude, and frequency) have not been investigated. This study evaluated 2D-TCA's ability to detect various forms of both simulated epileptic activity and EEG-fMRI activity detected in patients. When applied to simulated data, 2D-TCA consistently detected activity in 6min runs containing 5 spikes/run, 10 spikes/run, and one 5s long event with hemodynamic response function amplitudes of at least 1.5%, 1.25%, and 1% above baseline respectively. When applied to patient data, while detection of interictal spikes was inconsistent, 2D-TCA consistently produced results similar to those obtained by EEG-fMRI when at least 2 prolonged interictal events (a few seconds each) occurred during the run. However, even for such cases it was determined that 2D-TCA can only be used to validate localization by other means or to create hypotheses as to where activity may occur, as it also detects changes not caused by epileptic activity. Copyright © 2011 Elsevier B.V. All rights reserved.

Detection of tire tread particles using laser-induced breakdown spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Prochazka, David, E-mail: prochazka.d@fme.vutbr.cz [Brno University of Technology, Institute of Physical Engineering, Technická 2, 616 00 Brno (Czech Republic); Brno University of Technology, Central European Institute of Technology, Technická 3058/10, CZ-616 00 Brno (Czech Republic); Bilík, Martin [Brno University of Technology, Institute of Forensic Engineering, Údolní 244/53, 602 00 Brno (Czech Republic); Prochazková, Petra [Masaryk University, Faculty of Science, Department of Chemistry, Kamenice 735/5, 625 00 Brno (Czech Republic); Klus, Jakub; Pořízka, Pavel; Novotný, Jan [Brno University of Technology, Central European Institute of Technology, Technická 3058/10, CZ-616 00 Brno (Czech Republic); Novotný, Karel [Masaryk University, Faculty of Science, Department of Chemistry, Kamenice 735/5, 625 00 Brno (Czech Republic); Brno University of Technology, Central European Institute of Technology, Technická 3058/10, CZ-616 00 Brno (Czech Republic); Ticová, Barbora [Masaryk University, Faculty of Science, Department of Chemistry, Kamenice 735/5, 625 00 Brno (Czech Republic); Bradáč, Albert; Semela, Marek [Brno University of Technology, Institute of Forensic Engineering, Údolní 244/53, 602 00 Brno (Czech Republic); and others

2015-06-01

The objective of this paper is a study of the potential of laser induced breakdown spectroscopy (LIBS) for detection of tire tread particles. Tire tread particles may represent pollutants; simultaneously, it is potentially possible to exploit detection of tire tread particles for identification of optically imperceptible braking tracks at locations of road accidents. The paper describes the general composition of tire treads and selection of an element suitable for detection using the LIBS method. Subsequently, the applicable spectral line is selected considering interferences with lines of elements that might be present together with the detected particles, and optimization of measurement parameters such as incident laser energy, gate delay and gate width is performed. In order to eliminate the matrix effect, measurements were performed using 4 types of tires manufactured by 3 different producers. An adhesive tape was used as a sample carrier. The most suitable adhesive tape was selected from 5 commonly available tapes, on the basis of their respective LIBS spectra. Calibration standards, i.e. an adhesive tape with different area content of tire tread particles, were prepared for the selected tire. A calibration line was created on the basis of the aforementioned calibration standards. The linear section of this line was used for determination of the detection limit value applicable to the selected tire. Considering the insignificant influence of matrix of various types of tires, it is possible to make a simple recalculation of the detection limit value on the basis of zinc content in a specific tire. - Highlights: • LIBS experimental measurement parameters for tire tread particles were optimize. • Calibration curve was prepared. • Limit of detection was determined.

Detection of tire tread particles using laser-induced breakdown spectroscopy

International Nuclear Information System (INIS)

Prochazka, David; Bilík, Martin; Prochazková, Petra; Klus, Jakub; Pořízka, Pavel; Novotný, Jan; Novotný, Karel; Ticová, Barbora; Bradáč, Albert; Semela, Marek

2015-01-01

The objective of this paper is a study of the potential of laser induced breakdown spectroscopy (LIBS) for detection of tire tread particles. Tire tread particles may represent pollutants; simultaneously, it is potentially possible to exploit detection of tire tread particles for identification of optically imperceptible braking tracks at locations of road accidents. The paper describes the general composition of tire treads and selection of an element suitable for detection using the LIBS method. Subsequently, the applicable spectral line is selected considering interferences with lines of elements that might be present together with the detected particles, and optimization of measurement parameters such as incident laser energy, gate delay and gate width is performed. In order to eliminate the matrix effect, measurements were performed using 4 types of tires manufactured by 3 different producers. An adhesive tape was used as a sample carrier. The most suitable adhesive tape was selected from 5 commonly available tapes, on the basis of their respective LIBS spectra. Calibration standards, i.e. an adhesive tape with different area content of tire tread particles, were prepared for the selected tire. A calibration line was created on the basis of the aforementioned calibration standards. The linear section of this line was used for determination of the detection limit value applicable to the selected tire. Considering the insignificant influence of matrix of various types of tires, it is possible to make a simple recalculation of the detection limit value on the basis of zinc content in a specific tire. - Highlights: • LIBS experimental measurement parameters for tire tread particles were optimize. • Calibration curve was prepared. • Limit of detection was determined

Detection Limits for Spectro-fluorometry: A Case Study in the Region of Finstersee, Canton Zug, Northern Switzerland

Science.gov (United States)

Otz, M. H.; Otz, H. K.; Keller, P.

2002-05-01

Synthetic fluorescent dyes, applied below the visual detection limit (< 0.1 mg/L), have been used as tracers of ground water flow paths since the beginning of the 1950s. Since 1965, we have used spectro-fluorometers with photomultipliers to measure low concentrations of fluorescent dyes in ground water in Switzerland. In collaboration with the Engineering Geology Department of the ETH, we have separated uranine at 0.1 ng/L and Na-naphtionate at 1 ng/L from background fluorescence of spring water in the Finstersee region. These values are 10-100 times lower than postulated detection limits in the literature. The use of low dye concentrations prevents a study region from being contaminated by increased background levels due to remnant dye within the aquifer, thereby leaving the region available for future dye tracing studies. Lower detection limits also can solve particular hydraulic problems where conventional methods fail and enhance the possibility for using artificial dyes in environmentally sensitive aquifer settings.

Preparation, Characterization, and UV Irradiation of Mars Soil Analogues Under Simulated Martian Conditions to Support Detection of Molecular Biomarkers

Science.gov (United States)

Fornaro, T.; Brucato, J. R.; ten Kate, I. L.; Siljeström, S.; Steele, A.; Cody, G. D.; Hazen, R. M.

2018-04-01

We present laboratory activities of preparation, characterization, and UV irradiation processing of Mars soil analogues, which are key to support both in situ exploration and sample return missions devoted to detection of molecular biomarkers on Mars.

High-Throughput Analysis With 96-Capillary Array Electrophoresis and Integrated Sample Preparation for DNA Sequencing Based on Laser Induced Fluorescence Detection

Energy Technology Data Exchange (ETDEWEB)

Xue, Gang [Iowa State Univ., Ames, IA (United States)

2001-01-01

The purpose of this research was to improve the fluorescence detection for the multiplexed capillary array electrophoresis, extend its use beyond the genomic analysis, and to develop an integrated micro-sample preparation system for high-throughput DNA sequencing. The authors first demonstrated multiplexed capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC) separations in a 96-capillary array system with laser-induced fluorescence detection. Migration times of four kinds of fluoresceins and six polyaromatic hydrocarbons (PAHs) are normalized to one of the capillaries using two internal standards. The relative standard deviations (RSD) after normalization are 0.6-1.4% for the fluoresceins and 0.1-1.5% for the PAHs. Quantitative calibration of the separations based on peak areas is also performed, again with substantial improvement over the raw data. This opens up the possibility of performing massively parallel separations for high-throughput chemical analysis for process monitoring, combinatorial synthesis, and clinical diagnosis. The authors further improved the fluorescence detection by step laser scanning. A computer-controlled galvanometer scanner is adapted for scanning a focused laser beam across a 96-capillary array for laser-induced fluorescence detection. The signal at a single photomultiplier tube is temporally sorted to distinguish among the capillaries. The limit of detection for fluorescein is 3 x 10^-11 M (S/N = 3) for 5-mW of total laser power scanned at 4 Hz. The observed cross-talk among capillaries is 0.2%. Advantages include the efficient utilization of light due to the high duty-cycle of step scan, good detection performance due to the reduction of stray light, ruggedness due to the small mass of the galvanometer mirror, low cost due to the simplicity of components, and flexibility due to the independent paths for excitation and emission.

Matrix effect on the detection limit and accuracy in total reflection X-ray fluorescence analysis of trace elements in environmental and biological samples

International Nuclear Information System (INIS)

Karjou, J.

2007-01-01

The effect of matrix contents on the detection limit of total reflection X-ray fluorescence analysis was experimentally investigated using a set of multielement standard solutions (500 ng/mL of each element) in variable concentrations of NH 4 NO 3 . It was found that high matrix concentration, i.e. 0.1-10% NH 4 NO 3 , had a strong effect on the detection limits for all investigated elements, whereas no effect was observed at lower matrix concentration, i.e. 0-0.1% NH 4 NO 3 . The effect of soil and blood sample masses on the detection limit was also studied. The results showed decreasing the detection limit (in concentration unit, μg/g) with increasing the sample mass. However, the detection limit increased (in mass unit, ng) with increasing sample mass. The optimal blood sample mass of ca. 200 μg was sufficient to improve the detection limit of Se determination by total reflection X-ray fluorescence. The capability of total reflection X-ray fluorescence to analyze different kinds of samples was discussed with respect to the accuracy and detection limits based on certified and reference materials. Direct analysis of unknown water samples from several sources was also presented in this work

Detection limits of Legionella pneumophila in environmental samples after co-culture with Acanthamoeba polyphaga

Science.gov (United States)

2013-01-01

Background The efficiency of recovery and the detection limit of Legionella after co-culture with Acanthamoeba polyphaga are not known and so far no investigations have been carried out to determine the efficiency of the recovery of Legionella spp. by co-culture and compare it with that of conventional culturing methods. This study aimed to assess the detection limits of co-culture compared to culture for Legionella pneumophila in compost and air samples. Compost and air samples were spiked with known concentrations of L. pneumophila. Direct culturing and co-culture with amoebae were used in parallel to isolate L. pneumophila and recovery standard curves for both methods were produced for each sample. Results The co-culture proved to be more sensitive than the reference method, detecting 102-103 L. pneumophila cells in 1 g of spiked compost or 1 m3 of spiked air, as compared to 105-106 cells in 1 g of spiked compost and 1 m3 of spiked air. Conclusions Co-culture with amoebae is a useful, sensitive and reliable technique to enrich L. pneumophila in environmental samples that contain only low amounts of bacterial cells. PMID:23442526

Evaluation of a manual DNA extraction protocol and an isothermal amplification assay for detecting HIV-1 DNA from dried blood spots for use in resource-limited settings.

Science.gov (United States)

Jordan, Jeanne A; Ibe, Christine O; Moore, Miranda S; Host, Christel; Simon, Gary L

2012-05-01

In resource-limited settings (RLS) dried blood spots (DBS) are collected on infants and transported through provincial laboratories to a central facility where HIV-1 DNA PCR testing is performed using specialized equipment. Implementing a simpler approach not requiring such equipment or skilled personnel could allow the more numerous provincial laboratories to offer testing, improving turn-around-time to identify and treat infected infants sooner. Assess performances of a manual DNA extraction method and helicase-dependent amplification (HDA) assay for detecting HIV-1 DNA from DBS. 60 HIV-1 infected adults were enrolled, blood samples taken and DBS made. DBS extracts were assessed for DNA concentration and beta globin amplification using PCR and melt-curve analysis. These same extracts were then tested for HIV-1 DNA using HDA and compared to results generated by PCR and pyrosequencing. Finally, HDA limit of detection (LOD) studies were performed using DBS extracts prepared with known numbers of 8E5 cells. The manual extraction protocol consistently yielded high concentrations of amplifiable DNA from DBS. LOD assessment demonstrated HDA detected ∼470 copies/ml of HIV-1 DNA extracts in 4/4 replicates. No statistical difference was found using the McNemar's test when comparing HDA to PCR for detecting HIV-1 DNA from DBS. Using just a magnet, heat block and pipettes, the manual extraction protocol and HDA assay detected HIV-1 DNA from DBS at levels that would be useful for early infant diagnosis. Next steps will include assessing HDA for non-B HIV-1 subtypes recognition and comparison to Roche HIV-1 DNA v1.5 PCR assay. Copyright © 2012 Elsevier B.V. All rights reserved.

The Impact of Including Below Detection Limit Samples in Post Decommissioning Soil Sample Analyses

Energy Technology Data Exchange (ETDEWEB)

Kim, Jung Hwan; Yim, Man-Sung [KAIST, Daejeon (Korea, Republic of)

2016-10-15

To meet the required standards the site owner has to show that the soil at the facility has been sufficiently cleaned up. To do this one must know the contamination of the soil at the site prior to clean up. This involves sampling that soil to identify the degree of contamination. However there is a technical difficulty in determining how much decontamination should be done. The problem arises when measured samples are below the detection limit. Regulatory guidelines for site reuse after decommissioning are commonly challenged because the majority of the activity in the soil at or below the limit of detection. Using additional statistical analyses of contaminated soil after decommissioning is expected to have the following advantages: a better and more reliable probabilistic exposure assessment, better economics (lower project costs) and improved communication with the public. This research will develop an approach that defines an acceptable method for demonstrating compliance of decommissioned NPP sites and validates that compliance. Soil samples from NPP often contain censored data. Conventional methods for dealing with censored data sets are statistically biased and limited in their usefulness. In this research, additional methods are performed using real data from a monazite manufacturing factory.

Electrochemical aptasensor for detecting tetracycline in milk

International Nuclear Information System (INIS)

Le, Thi Hanh; Pham, Van Phuc; La, Thi Huyen; Le, Quang Huan; Phan, Thi Binh

2016-01-01

A rapid, simple and sensitive biosensor system for tetracycline detection is very important in food safety. In this paper we developed a label-free aptasensor for electrochemical detection of tetracycline. According to the electrochemical impendence spectroscopy (EIS) analysis, there was a linear relationship between the concentration of tetracycline and the electron transfer resistance from 10 to 3000 ng ml −1 of the tetracycline concentration. The detection limit was 10 ng ml −1 in 15 min detection duration. The prepared aptasensor showed a good reproducibility with an acceptable stability in tetracycline detection. The recoveries of tetracycline in spiked milk samples were in the range of 88.1%–94.2%. The aptasensor has sensitivity 98% and specificity of 100%. (paper)

Thermal ionization mass spectrometry (TIMS) of actinides: Pushing the limits of accuracy and detection

Energy Technology Data Exchange (ETDEWEB)

Buerger, Stefan; Boulyga, Sergei; Cunningham, Alan; Klose, Dilani; Koepf, Andreas; Poths, Jane [Safeguards Analytical Laboratory, International Atomic Energy Agency, Vienna (Austria); Richter, Stephan [Institute for Reference Materials and Measurements, JRC-EU, Geel (Belgium)

2010-07-01

New method developments in multi-collector thermal ionization mass spectrometry (MC-TIMS) for actinide isotope ratio analysis to improve accuracy and limits of detection will be presented. With respect to limits of detection, results on improving work function using various carbon additives will be reviewed and presented as well as developments in cavity ion source (as compared to standard flat ribbon filament ion source) for femto- and attogram levels of uranium, plutonium, and americium. With respect to accuracy, results on isotope ratio measurements of isotopes of uranium (relative accuracy of 0.3% to 0.01%) are presented with an example being U-234-Th-230 age-dating (NBL CRM 112-A). In this context, the importance of traceability (to the S.I. units) and the use of (certified) reference materials are emphasized. The focus of this presentation is on applications to nuclear safeguards / forensics.

Flexible Modeling of Survival Data with Covariates Subject to Detection Limits via Multiple Imputation.

Science.gov (United States)

Bernhardt, Paul W; Wang, Huixia Judy; Zhang, Daowen

2014-01-01

Models for survival data generally assume that covariates are fully observed. However, in medical studies it is not uncommon for biomarkers to be censored at known detection limits. A computationally-efficient multiple imputation procedure for modeling survival data with covariates subject to detection limits is proposed. This procedure is developed in the context of an accelerated failure time model with a flexible seminonparametric error distribution. The consistency and asymptotic normality of the multiple imputation estimator are established and a consistent variance estimator is provided. An iterative version of the proposed multiple imputation algorithm that approximates the EM algorithm for maximum likelihood is also suggested. Simulation studies demonstrate that the proposed multiple imputation methods work well while alternative methods lead to estimates that are either biased or more variable. The proposed methods are applied to analyze the dataset from a recently-conducted GenIMS study.

Evaluation on the detection limit of blood hemoglobin using photolepthysmography based on path-length optimization

Science.gov (United States)

Sun, Di; Guo, Chao; Zhang, Ziyang; Han, Tongshuai; Liu, Jin

2016-10-01

The blood hemoglobin concentration's (BHC) measurement using Photoplethysmography (PPG), which gets blood absorption to near infrared light from the instantaneous pulse of transmitted light intensity, has not been applied to the clinical use due to the non-enough precision. The main challenge might be caused of the non-enough stable pulse signal when it's very weak and it often varies in different human bodies or in the same body with different physiological states. We evaluated the detection limit of BHC using PPG as the measurement precision level, which can be considered as a best precision result because we got the relative stable subject's pulse signals recorded by using a spectrometer with high signal-to-noise ratio (SNR) level, which is about 30000:1 in short term. Moreover, we optimized the used pathlength using the theory based on optimum pathlength to get a better sensitivity to the absorption variation in blood. The best detection limit was evaluated as about 1 g/L for BHC, and the best SNR of pulse for in vivo measurement was about 2000:1 at 1130 and 1250 nm. Meanwhile, we conclude that the SNR of pulse signal should be better than 400:1 when the required detection limit is set to 5 g/L. Our result would be a good reference to the BHC measurement to get a desired BHC measurement precision of real application.

Limits on surface gravities of Kepler planet-candidate host stars from non-detection of solar-like oscillations

Energy Technology Data Exchange (ETDEWEB)

Campante, T. L.; Chaplin, W. J.; Handberg, R.; Miglio, A.; Davies, G. R.; Elsworth, Y. P. [School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Lund, M. N.; Arentoft, T.; Christensen-Dalsgaard, J.; Karoff, C.; Kjeldsen, H.; Lundkvist, M. [Stellar Astrophysics Centre (SAC), Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark); Huber, D. [NASA Ames Research Center, MS 244-30, Moffett Field, CA 94035 (United States); Hekker, S. [Astronomical Institute, " Anton Pannekoek," University of Amsterdam, Amsterdam (Netherlands); García, R. A. [Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot (France); IRFU/SAp, Centre de Saclay, F-91191 Gif-sur-Yvette Cedex (France); Corsaro, E. [Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Basu, S. [Department of Astronomy, Yale University, New Haven, CT 06520 (United States); Bedding, T. R. [Sydney Institute for Astronomy, School of Physics, University of Sydney, Sydney (Australia); Gilliland, R. L. [Center for Exoplanets and Habitable Worlds, The Pennsylvania State University, University Park, PA 16802 (United States); Kawaler, S. D., E-mail: campante@bison.ph.bham.ac.uk [Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); and others

2014-03-10

We present a novel method for estimating lower-limit surface gravities (log g) of Kepler targets whose data do not allow the detection of solar-like oscillations. The method is tested using an ensemble of solar-type stars observed in the context of the Kepler Asteroseismic Science Consortium. We then proceed to estimate lower-limit log g for a cohort of Kepler solar-type planet-candidate host stars with no detected oscillations. Limits on fundamental stellar properties, as provided by this work, are likely to be useful in the characterization of the corresponding candidate planetary systems. Furthermore, an important byproduct of the current work is the confirmation that amplitudes of solar-like oscillations are suppressed in stars with increased levels of surface magnetic activity.

The determination of levofloxacin by flow injection analysis using UV detection, potentiometry, and conductometry in pharmaceutical preparations.

Science.gov (United States)

Altiokka, G; Atkosar, Z; Can, N O

2002-10-15

A flow injection analysis (FIA) using UV detection, potentiometry and conductometry for levofloxacin (LVF) are described in this study. The best solvent system was found to consist of 0.2 M acetate buffer at pH 3 having 10% MeOH. A flow rate of 1 ml min(-1) was pumped and active material was detected at 288 nm. The detection limit (LOD) and limit of quantification (LOQ) for FIA were calculated to be 3 x 10(-7) M (S/N = 3) and 1 x 10(-7) M (S/N = 10), respectively. In the analysis of tablets, the RSD values were found to be 0.83, 0.98 and 0.99 for FIA, potentiometric and conductometric methods, respectively. Copyright 2002 Elsevier Science B.V.

Comparison of TXRF detection limits for low Z elements in different beam geometries at the PTB monochromator beamline for undulator radiation at Bessy II

International Nuclear Information System (INIS)

Beckhoff, B.; Ulm, G.; Pepponi, G.; Streli, C.; Wobrauschek, P.; Fabry, L.; Pahlke, S.

2000-01-01

A set of initial TXRF experiments were conducted at the PTB plane grating monochromator beamline for undulator radiation at the electron storage ring BESSY II allowing for exciting energies between 0.1 keV and 1.9 keV. Here, the lower limits of detection of TXRF analysis investigated for some low Z elements such as C, N, 0, Al, Mg and Na in two different detection geometries for various excitation modes. Compared to ordinary XRF geometries involving large incident angles, the TXRF variant offers also at low excitation energies drastically reduced background contributions due to the small penetration depth caused by the total reflection of the incident beam at the polished surface of a flat specimen carrier such as a silicon wafer. For the sake of an application-oriented TXRF approach, droplet samples on Si wafer surfaces were prepared by Wacker Siltronic and investigated in the TXRF irradiation chamber of the Atominstitut offering a semiconductor detector with a thin entrance window that was only 300 nm thick. (author)

Detection Limits for Nanoscale Biosensors

National Research Council Canada - National Science Library

Sheehan, Paul E; Whitman, Lloyd J

2005-01-01

We examine through analytical calculations and finite element simulations how the detection efficiency of disk and wire-like biosensors in unmixed fluids varies with size from the micrometer to nanometer scales...

Development and validation of a sensitive spectrofluorimetric method for the determination of cilazapril of human plasma, urine, in pure and pharmaceutical preparations

Science.gov (United States)

Karasakal, A.

2015-08-01

A selective and sensitive spectrofluorimetric method was developed and validated for the determination of cilazapril in human plasma urine, in pure and pharmaceutical preparations. The proposed method is based on derivatization using 1-dimethylaminonaphthalene-5-sulphonyl chloride (dansyl chloride) as fluorogenic agent and measuring the fluorescence of the products at emission wavelengths of 503 nm after excitation at 374 nm. The method was validated for linearity, limit of detection, limit of quantification, precision, accuracy, recovery. The calibration curves were linear over a concentration range of 100-500 and 50-250 ng/mL for plasma and urine, respectively. The limits of detection were calculated to be 0.26 and 31.59 ng/mL for plasma and urine, respectively. The proposed method was applied to study of cilazapril in pure, human plasma, urine, and pharmaceutical preparations.

Picomolar detection limits with current-polarized Pb2+ ion-selective membranes.

Science.gov (United States)

Pergel, E; Gyurcsányi, R E; Tóth, K; Lindner, E

2001-09-01

Minor ion fluxes across ion-selective membranes bias submicromolar activity measurements with conventional ion-selective electrodes. When ion fluxes are balanced, the lower limit of detection is expected to be dramatically improved. As proof of principle, the flux of lead ions across an ETH 5435 ionophore-based lead-selective membrane was gradually compensated by applying a few nanoamperes of galvanostatic current. When the opposite ion fluxes were matched, and the undesirable leaching of primary ions was eliminated, Nernstian response down to 3 x 10(-12) M was achieved.

High-throughput automated microfluidic sample preparation for accurate microbial genomics.

Science.gov (United States)

Kim, Soohong; De Jonghe, Joachim; Kulesa, Anthony B; Feldman, David; Vatanen, Tommi; Bhattacharyya, Roby P; Berdy, Brittany; Gomez, James; Nolan, Jill; Epstein, Slava; Blainey, Paul C

2017-01-27

Low-cost shotgun DNA sequencing is transforming the microbial sciences. Sequencing instruments are so effective that sample preparation is now the key limiting factor. Here, we introduce a microfluidic sample preparation platform that integrates the key steps in cells to sequence library sample preparation for up to 96 samples and reduces DNA input requirements 100-fold while maintaining or improving data quality. The general-purpose microarchitecture we demonstrate supports workflows with arbitrary numbers of reaction and clean-up or capture steps. By reducing the sample quantity requirements, we enabled low-input (∼10,000 cells) whole-genome shotgun (WGS) sequencing of Mycobacterium tuberculosis and soil micro-colonies with superior results. We also leveraged the enhanced throughput to sequence ∼400 clinical Pseudomonas aeruginosa libraries and demonstrate excellent single-nucleotide polymorphism detection performance that explained phenotypically observed antibiotic resistance. Fully-integrated lab-on-chip sample preparation overcomes technical barriers to enable broader deployment of genomics across many basic research and translational applications.

Sensitive spectrofluorimetric determination of tizanidine in pharmaceutical preparations, human plasma and urine through derivatization with dansyl chloride.

Science.gov (United States)

Ulu, Sevgi Tatar

2012-01-01

A sensitive spectrofluorimetric method was developed for the determination of tizanidine in human plasma, urine and pharmaceutical preparations. The method is based on reaction of tizanidine with 1-dimethylaminonaphthalene-5-sulphonyl chloride (dansyl chloride) in an alkaline medium to form a highly fluorescent derivative that was measured at 511 nm after excitation at 383 nm. The different experimental parameters affecting the fluorescence intensity of tizanidine was carefully studied and optimized. The fluorescence-concentration plots were rectilinear over the ranges 50-500 and 20-300 ng/mL for plasma and urine, respectively, detection limits of 1.81 and 0.54 ng/mL and quantification limits of 5.43 and 1.62 ng/mL for plasma and urine, respectively. The method presents good performance in terms of linearity, detection and quantification limits, precision, accuracy and specificity. The proposed method was successfully applied for the determination of tizanidine in pharmaceutical preparations. The results obtained were compared with a reference method, using t- and F-tests. Copyright © 2011 John Wiley & Sons, Ltd.

The study on the lidar's detection limit for Iodine Gas

Energy Technology Data Exchange (ETDEWEB)

Kim, Dong-lyul; Baik, Seung-Hoon; Park, Seung-Kyu; Park, Nak-Gyu; Ahn, Yong-Jin [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2015-05-15

A powerful and reliable tool for range-resolved remote sensing of gas concentrations that has proven its capabilities in a variety of studies is the differential absorption lidar (DIAL). Differential absorption lidar (DIAL) is frequently used for atmospheric gas monitoring to detect impurities such as nitrogen dioxide, sulfur dioxide, iodine, and ozone. DIAL can measure air pollutant concentrations with a high spatial resolution by adopting two laser systems with different degrees of absorption between the two different wavelengths. The absorption of the reference wavelength is very weak, while the absorption of the other wavelength is very strong. In this paper, we measured the limit of detection capability of our designed DIAL system. The DIAL measurements were performed using a target iodine cell in the laboratory. We confirmed that the concentration of iodine gas ratio increased after the laser passed through the iodine cell. The system of DIAL(Differential Absorption Lidar) was effective to detect the iodine gas. We obtained the signals from the iodine target cell and the lidar signal from the iodine target cell was proportional to frequency locking ratios.

First direct detection limits on sub-GeV dark matter from XENON10.

Science.gov (United States)

Essig, Rouven; Manalaysay, Aaron; Mardon, Jeremy; Sorensen, Peter; Volansky, Tomer

2012-07-13

The first direct detection limits on dark matter in the MeV to GeV mass range are presented, using XENON10 data. Such light dark matter can scatter with electrons, causing ionization of atoms in a detector target material and leading to single- or few-electron events. We use 15  kg day of data acquired in 2006 to set limits on the dark-matter-electron scattering cross section. The strongest bound is obtained at 100 MeV where σ(e)dark-matter masses between 20 MeV and 1 GeV are bounded by σ(e)dark-matter candidates with masses well below the GeV scale.

The Cu-MOF-199/single-walled carbon nanotubes modified electrode for simultaneous determination of hydroquinone and catechol with extended linear ranges and lower detection limits

International Nuclear Information System (INIS)

Zhou, Jian; Li, Xi; Yang, Linlin; Yan, Songlin; Wang, Mengmeng; Cheng, Dan; Chen, Qi; Dong, Yulin; Liu, Peng; Cai, Weiquan; Zhang, Chaocan

2015-01-01

A novel electrochemical sensor based on Cu-MOF-199 [Cu-MOF-199 = Cu 3 (BTC) 2 (BTC = 1,3,5-benzenetricarboxylicacid)] and SWCNTs (single-walled carbon nanotubes) was fabricated for the simultaneous determination of hydroquinone (HQ) and catechol (CT). The modification procedure was carried out through casting SWCNTs on the bare glassy carbon electrode (GCE) and followed by the electrodeposition of Cu-MOF-199 on the SWCNTs modified electrode. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) were performed to characterize the electrochemical performance and surface characteristics of the as-prepared sensor. The composite electrode exhibited an excellent electrocatalytic activity with increased electrochemical signals towards the oxidation of HQ and CT, owing to the synergistic effect of SWCNTs and Cu-MOF-199. Under the optimized condition, the linear response range were from 0.1 to 1453 μmol L −1 (R HQ  = 0.9999) for HQ and 0.1–1150 μmol L −1 (R CT  = 0.9990) for CT. The detection limits for HQ and CT were as low as 0.08 and 0.1 μmol L −1 , respectively. Moreover, the modified electrode presented the good reproducibility and the excellent anti-interference performance. The analytical performance of the developed sensor for the simultaneous detection of HQ and CT had been evaluated in practical samples with satisfying results. - Highlights: • Cu-MOF-199/SWCNTs/GCE was facilely fabricated by the electrodeposition on SWCNTs/GCE. • An electrochemical sensor for detecting HQ and CT was constructed based on this modified electrode. • The proposed electrochemical sensor showed an extended linear range and lower detection limits. • The proposed electrochemical sensor had an excellent stability and reproducibility.

Continuous preparation of Fe{sub 3}O{sub 4} nanoparticles through Impinging Stream-Rotating Packed Bed reactor and their electrochemistry detection toward heavy metal ions

Energy Technology Data Exchange (ETDEWEB)

Fan, Hong-Lei [Shanxi Province Key Laboratory of Higee-Oriented Chemical Engineering, North University of China, Taiyuan, 030051 (China); Zhou, Shao-Feng [Shanxi Province Key Laboratory of Functional Nanocomposites, North University of China, Taiyuan, 030051 (China); Gao, Jing [Shanxi Province Key Laboratory of Higee-Oriented Chemical Engineering, North University of China, Taiyuan, 030051 (China); Liu, You-Zhi, E-mail: lyzzhongxin@126.com [Shanxi Province Key Laboratory of Higee-Oriented Chemical Engineering, North University of China, Taiyuan, 030051 (China)

2016-06-25

We reported the continuous preparation and electrochemical behavior toward heavy metal ions of the Fe{sub 3}O{sub 4} nanoparticles (Fe{sub 3}O{sub 4} NPs). This Fe{sub 3}O{sub 4} NPs were fabricated through a novel Impinging Stream-Rotating Packed Bed reactor with a high production rate of 2.23 kg/hour. The as-prepared Fe{sub 3}O{sub 4} NPs were quasi-spherical with a mean diameter of about 10 nm and shown the characteristics of superparamagnetism with the saturated magnetization of 60.5 emu/g. The electrochemical characterization of the as-prepared Fe{sub 3}O{sub 4} NPs toward heavy metal ions were evaluated using square wave anodic stripping voltammetry (SWASV) analysis. The results indicated that the modified electrode could be used to individual detection of Pb(II), Cu(II), Hg(II) and Cd(II). In particular, the modified electrode exhibited the selective detection toward Pb(II) with higher sensitivity of 14.9 μA/μM, while the response to Cu(II), Hg(II) and Cd(II) were negligible. Besides, the modified electrode shown good stability and potential practical applicability in the electrochemical determination of Pb(II). This above results offered a simple method for continuous preparation sensing materials in the application field of electrochemical detection of toxic metal ions through the technology of process intensification. - Highlights: • Fe{sub 3}O{sub 4} nanoparticles were continuous prepared through IS-RPB reactor. • The Fe{sub 3}O{sub 4} nanoparticles showed selective detection of heavy metal ions. • It exhibited favorable sensitivity (14.9 μA μM{sup −1}) and LOD (0.119 μM) for Pb(II). • The as-prepared nanoparticles showed favorable potential application.

A fluorescence probe based on the nitrogen-doped carbon dots prepared from orange juice for detecting Hg2+ in water

International Nuclear Information System (INIS)

Li, Zhili; Zhang, Ying; Niu, Qianqian; Mou, Mingyao; Wu, Yi; Liu, Xiaoxuan; Yan, Zhengyu; Liao, Shenghua

2017-01-01

An excellent biocompatible nitrogen-doped carbon dots (N-CDs) was successfully synthesized from orange juice and ethylenediamine by hydrothermal decomposition method. The as-prepared N-CDs were mono-dispersed spherical nanoparticles with a narrow size distribution of 0.5–3.0 nm and showed a good dispersion and stability in aqueous solution with the pH value ranging from 3.0 to 13.0. Photoluminescence spectra of as-prepared N-CDs demonstrated that the fluorescence intensity of N-CDs was increased with the doped nitrogen atoms and the FL-QY (fluorescence quantum yield) of N-CDs was up to 31.7%. Compared with Gly-CQDs(CQDs synthesied by Gly), which were prepared from chemical carbon source via hydrothermal decomposition method, the as-prepared N-CDs showed much lower cytotoxicity for Human THP-1 macrophage cells. These results indicated N-CDs prepared by our proposed method have excellent compatibility and more suitable for the application in biolabeling and bioimage. Due to the fluorescence quenching of N-CDs by mercury (II) ion (Hg 2+ ), a sensitive and selective method was developed for detecting Hg 2+ . The results indicated that the fluorescence intensity ratio of N-CDs was proportional to the concentration of Hg 2+ in the range from 4.0 μg/mL to 32.0 μg/mL and the recovery of spiked samples was ranged from 102.0% to 103.0%, which hinted our proposed method has a good sensitivity and accuracy and was suitable for detecting Hg 2+ with satisfactory in tap water.

Preparation of a thin polysulfone phosphor sheet for the detection of alpha particles using adhesive process

International Nuclear Information System (INIS)

Seo, B. K.; Woo, Z. H.; Kim, G. H.; Chang, U. S.; Oh, W. Z.; Lee, K. W.; Han, M. J.

2005-01-01

According to atomic energy law and connection regs, the surface contamination of nuclear facilities should be monitored routinely. Surface contamination is divided into removable and fixed contamination. Fixed contamination is measured by a direct method with a survey meter. And removable contamination is measured by an indirect method using smear paper and a low background proportional counter. Also, in the decommissioning process of a nuclear research facilities, such as Korean Research Reactor 1 and 2 and Uranium Conversion Plant, a significant amount of nuclear wastes is produced. The wastes contaminated must be surveyed for the disposal and reuse in the future. In the previous study the medium, scintillatorembedded polymer membrane for detecting the alpharay, was prepared by impregnating organic scintillators in a membrane structure. The plastic scintillator consists of polysulfone(PSF) as a matrix with PPO as an organic scintillator and POPOP as a wave shifting agent dissolved in the matrix. But, an organic plastic scintillator was inadequate to detect the alpha particle in the alpha-beta mixing field because its light output is smaller than beta ray one. So, a thin phosphor sheet was prepared, which consisted of a very uniform deposit of silver activated zinc sulfide (ZnS(Ag)) phosphor applied to on side of clear polysulfone plastic sheet

Solvent-assisted dispersive solid-phase extraction: A sample preparation method for trace detection of diazinon in urine and environmental water samples.

Science.gov (United States)

Aladaghlo, Zolfaghar; Fakhari, Alireza; Behbahani, Mohammad

2016-09-02

In this research, a sample preparation method termed solvent-assisted dispersive solid-phase extraction (SA-DSPE) was applied. The used sample preparation method was based on the dispersion of the sorbent into the aqueous sample to maximize the interaction surface. In this approach, the dispersion of the sorbent at a very low milligram level was received by inserting a solution of the sorbent and disperser solvent into the aqueous sample. The cloudy solution created from the dispersion of the sorbent in the bulk aqueous sample. After pre-concentration of the diazinon, the cloudy solution was centrifuged and diazinon in the sediment phase dissolved in ethanol and determined by gas chromatography-flame ionization detector. Under the optimized conditions (pH of solution=7.0, Sorbent: benzophenone, 2%, Disperser solvent: ethanol, 500μL, Centrifuge: centrifuged at 4000rpm for 3min), the method detection limit for diazinon was 0.2, 0.3, 0.3 and 0.3μgL(-1) for distilled water, lake water, waste water and urine sample, respectively. Furthermore, the pre-concentration factor was 363.8, 356.1, 360.7 and 353.38 in distilled water, waste water, lake water and urine sample, respectively. SA-DSPE was successfully used for trace monitoring of diazinon in urine, lake and waste water samples. Copyright © 2016 Elsevier B.V. All rights reserved.

The ground fault detection system for the Tore Supra toroidal pump limiter

International Nuclear Information System (INIS)

Zunino, K.; Cara, P.; Fejoz, P.; Hourtoule, J.; Loarer, T.; Pomaro, N.; Santagiustina, A.; Spuig, P.; Villecroze, F.

2003-01-01

The toroidal pump limiter (TPL) of Tore Supra is electrically insulated from the vacuum-vessel, to allow its polarization at a voltage of up to 1 kV. In order to monitor continuously the integrity of the TPL electrical insulation, an electronic diagnostic system called TPL ground fault detection system (GFDS) has been developed. The paper will report on the design and the operation experience of the GFD system and on the evolution of the TPL grounding

A comparison of the sensitivities of detection of Plasmodium falciparum gametocytes by magnetic fractionation, thick blood film microscopy, and RT-PCR

Directory of Open Access Journals (Sweden)

St-Pierre Tim G

2009-05-01

Full Text Available Abstract Background The magnetic properties of Plasmodium-infected erythrocytes have been exploited for different clinical and research purposes. A recent study in a rural clinical setting in Papua New Guinea has demonstrated that Plasmodium falciparum gametocyte detection is facilitated by magnetic deposition microscopy but no study has yet determined the relative sensitivity and limit of detection of a magnetic fractionation technique. The present study compares the detection limit and sensitivity of a technique based on the use of commercially available magnetic fractionation columns with those for thick blood film microscopy and reverse transcriptase polymerase chain reaction (RT-PCR methods. Methods Gametocyte detection in six series of dilutions of cultured P. falciparum parasites with known gametocytaemia was conducted using magnetic fractionation, thick blood film, and RT-PCR techniques. Results The preparations obtained by the magnetic fractionation method were of thin film quality allowing easy gametocyte identification by light microscopy. Magnetic fractionation had a higher sensitivity and approximately two orders of magnitude better limit of detection than thick blood film microscopy. Gametocytes were also more readily detectable on the magnetically fractionated preparations. Magnetic fractionation had a similar limit of detection to that of RT-PCR. Conclusion Magnetic fractionation is a highly sensitive and convenient method for gametocyte detection in comparison with the standard thick blood film and RT-PCR methods, and could readily be adapted to field application.

Detection of urinary creatinine using gold nanoparticles after solid phase extraction

Science.gov (United States)

Sittiwong, Jarinya; Unob, Fuangfa

2015-03-01

Label-free gold nanoparticles (AuNPs) were utilized in the detection of creatinine in human urine after a sample preparation by extraction of creatinine on sulfonic acid functionalized silica gel. With the proposed sample preparation method, the interfering effects of the urine matrix on creatinine detection by AuNPs were eliminated. Parameters affecting creatinine extraction were investigated. The aggregation of AuNPs induced by creatinine resulted in a change in the surface plasmon resonance signal with a concomitant color change that could be observed by the naked eye and quantified spectrometrically. The effect of AuNP concentration and reaction time on AuNP aggregation was investigated. The method described herein provides a determination of creatinine in a range of 15-40 mg L-1 with a detection limit of 13.7 mg L-1 and it was successfully used in the detection of creatinine in human urine samples.

Physiological techniques for detecting expiratory flow limitation during tidal breathing

Directory of Open Access Journals (Sweden)

N.G. Koulouris

2011-09-01

Full Text Available Patients with severe chronic obstructive pulmonary disease (COPD often exhale along the same flow–volume curve during quiet breathing as they do during the forced expiratory vital capacity manoeuvre, and this has been taken as an indicator of expiratory flow limitation at rest (EFLT. Therefore, EFLT, namely attainment of maximal expiratory flow during tidal expiration, occurs when an increase in transpulmonary pressure causes no increase in expiratory flow. EFLT leads to small airway injury and promotes dynamic pulmonary hyperinflation, with concurrent dyspnoea and exercise limitation. In fact, EFLT occurs commonly in COPD patients (mainly in Global Initiative for Chronic Obstructive Lung Disease III and IV stage, in whom the latter symptoms are common, but is not exclusive to COPD, since it can also be detected in other pulmonary and nonpulmonary diseases like asthma, acute respiratory distress syndrome, heart failure and obesity, etc. The existing up to date physiological techniques of assessing EFLT are reviewed in the present work. Among the currently available techniques, the negative expiratory pressure has been validated in a wide variety of settings and disorders. Consequently, it should be regarded as a simple, noninvasive, practical and accurate new technique.

Diamond-based electrochemical aptasensor realizing a femtomolar detection limit of bisphenol A.

Science.gov (United States)

Ma, Yibo; Liu, Junsong; Li, Hongdong

2017-06-15

In this study, we designed and fabricated an electrochemical impedance aptasensor based on Au nanoparticles (Au-NPs) coated boron-doped diamond (BDD) modified with aptamers, and 6-mercapto-1-hexanol (MCH) for the detection of bisphenol A (BPA). The constructed BPA aptasensor exhibits good linearity from 1.0×10 -14 to 1.0×10 -9 molL -1 . The detection limitation of 7.2×10 -15 molL -1 was achieved, which can be attributed to the synergistic effect of combining BDD with Au-NPs, aptamers, and MCH. The examine results of BPA traces in Tris-HCl buffer and in milk, UV spectra of aptamer/BPA and interference test revealed that the novel aptasensors are of high sensitivity, specificity, stability and repeatability, which could be promising in practical applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Detecting ultra high energy neutrinos with LOFAR

International Nuclear Information System (INIS)

Mevius, M.; Buitink, S.; Falcke, H.; Hörandel, J.; James, C.W.; McFadden, R.; Scholten, O.; Singh, K.; Stappers, B.; Veen, S. ter

2012-01-01

The NuMoon project aims to detect signals of Ultra High Energy (UHE) Cosmic Rays with radio telescopes on Earth using the Lunar Cherenkov technique at low frequencies (∼150MHz). The advantage of using low frequencies is the much larger effective detecting volume, with as trade-off the cut-off in sensitivity at lower energies. A first upper limit on the UHE neutrino flux from data of the Westerbork Radio Telescope (WSRT) has been published, while a second experiment, using the new LOFAR telescope, is in preparation. The advantages of LOFAR over WSRT are the larger collecting area, the better pointing accuracy and the use of ring buffers, which allow the implementation of a sophisticated self-trigger algorithm. The expected sensitivity of LOFAR reaches flux limits within the range of some theoretical production models.

Improved sensitivity and limit-of-detection of lateral flow devices using spatial constrictions of the flow-path.

Science.gov (United States)

Katis, Ioannis N; He, Peijun J W; Eason, Robert W; Sones, Collin L

2018-05-03

We report on the use of a laser-direct write (LDW) technique that allows the fabrication of lateral flow devices with enhanced sensitivity and limit of detection. This manufacturing technique comprises the dispensing of a liquid photopolymer at specific regions of a nitrocellulose membrane and its subsequent photopolymerisation to create impermeable walls inside the volume of the membrane. These polymerised structures are intentionally designed to create fluidic channels which are constricted over a specific length that spans the test zone within which the sample interacts with pre-deposited reagents. Experiments were conducted to show how these constrictions alter the fluid flow rate and the test zone area within the constricted channel geometries. The slower flow rate and smaller test zone area result in the increased sensitivity and lowered limit of detection for these devices. We have quantified these via the improved performance of a C-Reactive Protein (CRP) sandwich assay on our lateral flow devices with constricted flow paths which demonstrate an improvement in its sensitivity by 62x and in its limit of detection by 30x when compared to a standard lateral flow CRP device. Crown Copyright © 2018. Published by Elsevier B.V. All rights reserved.

Limit of detection for the determination of Pt in biological material by RNAA using electrolytic separation of gold

International Nuclear Information System (INIS)

Xilei, L.; Heydorn, K.; Rietz, B.

1992-01-01

Neutron activation analysis based on the 199 Au indicator for platinum requires the separation of gold at high radiochemical purity. The limit of detection is strongly affected by the presence of gold; with a gold content of 50 pg/g, irradiating for 5 days at 5*10 13 n/cm 2 is needed to achieve a limit of detection of approximately 30 pg/g. In this case the nuclear interference from gold will exceeded the level of platium by several orders of magnitude and has to be determined with exceedingly high precision. Preliminary results for SRM 1577 Bovine Liver with 95% yield gave consistent results for Au, but Pt could not be detected. (author) 23 refs.; 3 figs.; 4 tabs

Detection limits of pollutants in water for PGNAA using Am-Be source

International Nuclear Information System (INIS)

Khelifi, R.; Amokrane, A.; Bode, P.

2007-01-01

A basic PGNAA facility with an Am-Be neutron source is described to analyze the pollutants in water. The properties of neutron flux were determined by MCNP calculations. In order to determine the efficiency curve of a HPGe detector, the prompt-gamma rays from chlorine were used and an exponential curve was fitted. The detection limits for typical water sample are also estimated using the statistical fluctuations of the background level in the areas of recorded the prompt-gamma spectrum

Determination of ethamsylate in pharmaceutical preparations based on an auto-oxidation chemiluminescence reaction.

Science.gov (United States)

Yang, Fengzhen; Zhang, Chao; Baeyens, Willy R G; Zhang, Xinrong

2002-10-15

Strong chemiluminescence emission has been observed by mixing alkaline hydrolytic products of ethamsylate with Tween 80 in acidic rhodamine 6G solution. This phenomenon has been utilized to design a flow-injection chemiluminescence method for the determination of ethamsylate in a pharmaceutical preparation. Under the optimum conditions, the proposed procedure has a linear range between 0.05 and 2.0 microg ml(-1), with a detection limit of 0.02 microg ml(-1) for ethamsylate. The method was applied to the determination of ethamsylate in pharmaceutical preparations. The possible mechanism of this chemiluminescence reaction was proposed. Copyright 2002 Elsevier Science B.V.

Direct Detection Electron Energy-Loss Spectroscopy: A Method to Push the Limits of Resolution and Sensitivity.

Science.gov (United States)

Hart, James L; Lang, Andrew C; Leff, Asher C; Longo, Paolo; Trevor, Colin; Twesten, Ray D; Taheri, Mitra L

2017-08-15

In many cases, electron counting with direct detection sensors offers improved resolution, lower noise, and higher pixel density compared to conventional, indirect detection sensors for electron microscopy applications. Direct detection technology has previously been utilized, with great success, for imaging and diffraction, but potential advantages for spectroscopy remain unexplored. Here we compare the performance of a direct detection sensor operated in counting mode and an indirect detection sensor (scintillator/fiber-optic/CCD) for electron energy-loss spectroscopy. Clear improvements in measured detective quantum efficiency and combined energy resolution/energy field-of-view are offered by counting mode direct detection, showing promise for efficient spectrum imaging, low-dose mapping of beam-sensitive specimens, trace element analysis, and time-resolved spectroscopy. Despite the limited counting rate imposed by the readout electronics, we show that both core-loss and low-loss spectral acquisition are practical. These developments will benefit biologists, chemists, physicists, and materials scientists alike.

Preparation of venlafaxine hydrochloride sustained-release tablets

Directory of Open Access Journals (Sweden)

ZHANG Yang

2013-02-01

Full Text Available A novel non－enzymatic glucose sensor was developed by electrodepositing copper film onto the graphene(GR substrate.The morphologies and structures of the nanocomposites were characterized by field emission scanning electron microscope (FESEM.The electrochemical performances of the Cu/GR nanocomposite film were investigated.The Cu/GR nanocomposite film showed good electrocatalytic activity towards glucose oxidation in alkaline solution.The Cu/GR nanocomposite film-based sensor displayed a linear concentration range from 8×10-6 to 9.4×10-4 mol/L with the sensitivity of 0.225 A·L·mol-1 and the detection limit (S/N=3 of 2.5 μmol/L for the detection of glucose.With an enhanced electrocatalytic property,high sensitivity and good stability.The as-prepared sensor is promising for the future development of nonenzymatic sensors.

ROBUST ESTIMATION OF MEAN AND VARIANCE USING ENVIRONMENTAL DATA SETS WITH BELOW DETECTION LIMIT OBSERVATIONS

Science.gov (United States)

Scientists, especially environmental scientists often encounter trace level concentrations that are typically reported as less than a certain limit of detection, L. Type 1, left-censored data arise when certain low values lying below L are ignored or unknown as they cannot be mea...

Method to Solve the Problem of the Radioactivity Detection in Environmental Samples. Characteristic Limits; Metodos para la Resolucion del Problema de la Detecfcion de Radiactividad en Muestras Ambientales. Limites Caracteristicos

Energy Technology Data Exchange (ETDEWEB)

Gasco, C.; Martinez, M.; Heras, M.

2009-07-21

The problem of the detection or when the radioactivity can be considered as higher than the background using different measurement techniques has been the objective of several statistical studies and controversies. The detection limit and the critical limit were studied by Currie in year 1968 and used by radiochemistry laboratories considering different ways of calculation that introduced confusion and not correct implementations. In the last few years, and due to the increasing number of standardization processes on the field of radioactivity and accreditation, several international institutions have chosen to unify the criteria for using common determination of detection limits. The most used methods are those developed by MARLAP and International Standard Organization ISO (Standard-11929). In this report are summarised both standards doing a comparative study and giving some examples of how to apply these limits. In same cases, little differences in the uncertainty calculation have been observed but the final results have been concordant. A deeply study of these standards can be done consulting the web page of the American Labs that developed MARLAP or buying the original ISO standard ISO-11929 recently approved (2009). (Author) 17 refs.

Molecularly imprinted polymers for sample preparation and biosensing in food analysis: Progress and perspectives.

Science.gov (United States)

Ashley, Jon; Shahbazi, Mohammad-Ali; Kant, Krishna; Chidambara, Vinayaka Aaydha; Wolff, Anders; Bang, Dang Duong; Sun, Yi

2017-05-15

Molecularly imprinted polymers (MIPs) are biomimetics which can selectively bind to analytes of interest. One of the most interesting areas where MIPs have shown the biggest potential is food analysis. MIPs have found use as sorbents in sample preparation attributed to the high selectivity and high loading capacity. MIPs have been intensively employed in classical solid-phase extraction and solid-phase microextraction. More recently, MIPs have been combined with magnetic bead extraction, which greatly simplifies sample handling procedures. Studies have consistently shown that MIPs can effectively minimize complex food matrix effects, and improve recoveries and detection limits. In addition to sample preparation, MIPs have also been viewed as promising alternatives to bio-receptors due to the inherent molecular recognition abilities and the high stability in harsh chemical and physical conditions. MIPs have been utilized as receptors in biosensing platforms such as electrochemical, optical and mass biosensors to detect various analytes in food. In this review, we will discuss the current state-of-the-art of MIP synthesis and applications in the context of food analysis. We will highlight the imprinting methods which are applicable for imprinting food templates, summarize the recent progress in using MIPs for preparing and analysing food samples, and discuss the current limitations in the commercialisation of MIPs technology. Finally, future perspectives will be given. Copyright © 2017 Elsevier B.V. All rights reserved.

Detecting terrestrial nutrient limitation: a global meta-analysis of foliar nutrient concentrations after fertilization

Directory of Open Access Journals (Sweden)

Rebecca eOstertag

2016-03-01

Full Text Available Examining foliar nutrient concentrations after fertilization provides an alternative method for detecting nutrient limitation of ecosystems, which is logistically simpler to measure than biomass change. We present a meta-analysis of response ratios of foliar nitrogen and phosphorus (RRN, RRP after addition of fertilizer of nitrogen (N, phosphorus (P, or the two elements in combination, in relation to climate, ecosystem type, life form, family, and methodological factors. Results support other meta-analyses using biomass, and demonstrate there is strong evidence for nutrient limitation in natural communities. However, because N fertilization experiments greatly outnumber P fertilization trials, it is difficult to discern the absolute importance of N vs. P vs. co-limitation across ecosystems. Despite these caveats, it is striking that results did not follow conventional wisdom that temperate ecosystems are N-limited and tropical ones are P-limited. In addition, the use of ratios of N-to-P rather than response ratios also are a useful index of nutrient limitation, but due to large overlap in values, there are unlikely to be universal cutoff values for delimiting N vs. P limitation. Differences in RRN and RRP were most significant across ecosystem types, plant families, life forms, and between competitive environments, but not across climatic variables.

Analysis of detection limit to time-resolved coherent anti-Stokes Raman scattering nanoscopy

International Nuclear Information System (INIS)

Liu Wei; Liu Shuang-Long; Chen Dan-Ni; Niu Han-Ben

2014-01-01

In the implementation of CARS nanoscopy, signal strength decreases with focal volume size decreasing. A crucial problem that remains to be solved is whether the reduced signal generated in the suppressed focal volume can be detected. Here reported is a theoretical analysis of detection limit (DL) to time-resolved CARS (T-CARS) nanoscopy based on our proposed additional probe-beam-induced phonon depletion (APIPD) method for the low concentration samples. In order to acquire a detailed shot-noise limited signal-to-noise (SNR) and the involved parameters to evaluate DL, the T-CARS process is described with full quantum theory to estimate the extreme power density levels of the pump and Stokes beams determined by saturation behavior of coherent phonons, which are both actually on the order of ∼ 10 9 W/cm 2 . When the pump and Stokes intensities reach such values and the total intensity of the excitation beams arrives at a maximum tolerable by most biological samples in a certain suppressed focal volume (40-nm suppressed focal scale in APIPD method), the DL correspondingly varies with exposure time, for example, DL values are 10 3 and 10 2 when exposure times are 20 ms and 200 ms respectively. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

Combination could be another tool for bowel preparation?

Science.gov (United States)

Soh, Jae Seung; Kim, Kyung-Jo

2016-01-01

Optimal bowel preparation increases the cecal intubation rate and detection of neoplastic lesions while decreasing the procedural time and procedural-related complications. Although high-volume polyethylene glycol (PEG) solution is the most frequently used preparation for bowel cleansing, patients are often unwilling to take PEG solution due to its large volume, poor palatability, and high incidence of adverse events, such as abdominal bloating and nausea. Other purgatives include osmotic agents (e.g., sodium phosphate, magnesium citrate, and sodium sulfate), stimulant agents (e.g., senna, bisacodyl, and sodium picosulfate), and prokinetic agents (e.g., cisapride, mosapride, and itopride). A combination of PEG with an osmotic, stimulant, or prokinetic agent could effectively reduce the PEG solution volume and increase patients’ adherence. Some such solutions have been found in several published studies to not be inferior to PEG alone in terms of bowel cleansing quality. Although combination methods showed similar efficacy and safety, the value of these studies is limited by shortcomings in study design. New effective and well-tolerated combination preparations are required, in addition to rigorous new validated studies. PMID:26973388

New limits on the detection of a composition-dependent macroscopic force

International Nuclear Information System (INIS)

Boynton, P.; Aronson, S.

1990-01-01

We report here on a continuing experimental search for a macroscopic, composition dependent force coupling to ordinary matter. Within the phenomenological framework commonly employed -- a Yukawa representation of the interaction potential, and composition specified as some linear combination of baryon and lepton numbers -- the Index 3 experiment sets the most stringent upper limits yet on the interaction strength for coupling from B-2L to B-L, and for an interaction range from 200 m to 10 km. It is also the first null result to conflict with the marginal detection reported for the Index 1 experiment for all relevant values of the composition and range parameters

Droplet Size-Aware and Error-Correcting Sample Preparation Using Micro-Electrode-Dot-Array Digital Microfluidic Biochips.

Science.gov (United States)

Li, Zipeng; Lai, Kelvin Yi-Tse; Chakrabarty, Krishnendu; Ho, Tsung-Yi; Lee, Chen-Yi

2017-12-01

Sample preparation in digital microfluidics refers to the generation of droplets with target concentrations for on-chip biochemical applications. In recent years, digital microfluidic biochips (DMFBs) have been adopted as a platform for sample preparation. However, there remain two major problems associated with sample preparation on a conventional DMFB. First, only a (1:1) mixing/splitting model can be used, leading to an increase in the number of fluidic operations required for sample preparation. Second, only a limited number of sensors can be integrated on a conventional DMFB; as a result, the latency for error detection during sample preparation is significant. To overcome these drawbacks, we adopt a next generation DMFB platform, referred to as micro-electrode-dot-array (MEDA), for sample preparation. We propose the first sample-preparation method that exploits the MEDA-specific advantages of fine-grained control of droplet sizes and real-time droplet sensing. Experimental demonstration using a fabricated MEDA biochip and simulation results highlight the effectiveness of the proposed sample-preparation method.

The limits of application of variable-energy slow positron beams for investigating TiN hard coatings prepared by PVD

International Nuclear Information System (INIS)

Marek, T.; Suevegh, K.; Vertes, A.; Szeles, Cs.; Lynn, K.G.

2000-01-01

Samples of TiN hard coatings prepared by physical vapour deposition (PVD) were investigated by means of depth-sensitive positron annihilation spectroscopy. The results indicate that the samples are at the limits of the applicability of this method presumably due to the high defect concentration. Though the samples are thoroughly characterized by other independent methods, they might not be sufficient to explain all aspects of positron-solid interactions in these cases. (author)

Molecular techniques for detection and identification of pathogens in food: advantages and limitations

OpenAIRE

Palomino-Camargo, Carolina; Instituto de Ciencia y Tecnología de Alimentos, Facultad de Ciencias, Universidad Central de Venezuela. Caracas, Venezuela. Magíster en Ciencia y Tecnología de los Alimentos licenciada en Biología; González-Muñoz, Yuniesky; Instituto de Ciencia y Tecnología de Alimentos, Facultad de Ciencias, Universidad Central de Venezuela. Caracas, Venezuela. Ministerio del Poder Popular para la Alimentación. Caracas, Venezuela. licenciado en Ciencias de los Alimentos.

2014-01-01

Foodborne diseases, caused by pathogenic microorganisms, are a major public health problem worldwide. Microbiological methods commonly used in the detection of these foodborne pathogens are laborious and time consuming. This situation, coupled with the demand for immediate results and with technological advances, has led to the development of a wide range of rapid methods in recent decades. On this basis, this review describes the advantages and limitations of the main molecular methods used ...

Evaluation of the limits of visual detection of image misregistration in a brain fluorine-18 fluorodeoxyglucose PET-MRI study

International Nuclear Information System (INIS)

Wong, J.C.H.; Studholme, C.; Hawkes, D.J.; Maisey, M.N.

1997-01-01

In routine clinical work, registration accuracy is assessed by visual inspection. However, the accuracy of visual assessment of registration has not been evaluated. This study establishes the limits of visual detection of misregistration in a registered brain fluorine-18 fluorodeoxyglucose positron emission tomography to magnetic resonance image volume. The ''best'' registered image volume was obtained by automatic registration using mutual information optimization. Translational movements by 1 mm, 2 mm, 3 mm and 4 mm, and rotational movements by 1 , 2 , 3 and 4 in the positive and negative directions in the x- (lateral), y- (anterior-posterior) and z- (axial) axes were introduced to this standard. These 48 images plus six ''best'' registered images were presented in random sequence to five observers for visual categorization of registration accuracy. No observer detected a definite misregistration in the ''best'' registered image. Evaluation for inter-observer variation using observer pairings showed a high percentage of agreement in assigned categories for both translational and rotational misregistrations. Assessment of the limits of detection of misregistration showed that a 2-mm translational misregistration was detectable by all observers in the x- and y-axes and 3-mm translational misregistration in the z-axis. With rotational misregistrations, rotation around the z-axis was detectable by all at 2 rotation whereas rotation around the y-axis was detected at 3-4 . Rotation around the x-axis was not symmetric with a positive rotation being identified at 2 whereas negative rotation was detected by all only at 4 . Therefore, visual analysis appears to be a sensitive and practical means to assess image misregistration accuracy. The awareness of the limits of visual detection of misregistration will lead to increase care when evaluating registration quality in both research and clinical settings. (orig.). With 6 figs., 3 tabs

Nanoplatforms for Detection, Remediation and Protection Against Chem-Bio Warfare

Science.gov (United States)

Denkbaş, E. B.; Bayram, C.; Kavaz, D.; Çirak, T.; Demirbilek, M.

Chemical and biological substances have been used as warfare agents by terrorists by varying degree of sophistication. It is critical that these agents be detected in real-time with high level of sensitively, specificity, and accuracy. Many different types of techniques and systems have been developed to detect these agents. But there are some limitations in these conventional techniques and systems. Limitations include the collection, handling and sampling procedures, detection limits, sample transfer, expensive equipment, personnel training, and detection materials. Due to the unique properties such as quantum effect, very high surface/volume ratio, enhanced surface reactivity, conductivity, electrical and magnetic properties of the nanomaterials offer great opportunity to develop very fast, sensitive, accurate and cost effective detection techniques and systems to detect chemical and biological (chem.-bio) warfare agents. Furthermore, surface modification of the materials is very easy and effective way to get functional or smart surfaces to be used as nano-biosensor platform. In that respect many different types of nanomaterials have been developed and used for the detection, remediation and protection, such as gold and silver nanoparticles, quantum dots, Nano chips and arrays, fluorescent polymeric and magnetic nanoparticles, fiber optic and cantilever based nanobiosensors, nanofibrillar nanostructures etc. This study summarizes preparation and characterization of nanotechnology based approaches for the detection of and remediation and protection against chem.-bio warfare agents.

Eco-friendly plasmonic sensors: using the photothermal effect to prepare metal nanoparticle-containing test papers for highly sensitive colorimetric detection.

Science.gov (United States)

Tseng, Shao-Chin; Yu, Chen-Chieh; Wan, Dehui; Chen, Hsuen-Li; Wang, Lon Alex; Wu, Ming-Chung; Su, Wei-Fang; Han, Hsieh-Cheng; Chen, Li-Chyong

2012-06-05

Convenient, rapid, and accurate detection of chemical and biomolecules would be a great benefit to medical, pharmaceutical, and environmental sciences. Many chemical and biosensors based on metal nanoparticles (NPs) have been developed. However, as a result of the inconvenience and complexity of most of the current preparation techniques, surface plasmon-based test papers are not as common as, for example, litmus paper, which finds daily use. In this paper, we propose a convenient and practical technique, based on the photothermal effect, to fabricate the plasmonic test paper. This technique is superior to other reported methods for its rapid fabrication time (a few seconds), large-area throughput, selectivity in the positioning of the NPs, and the capability of preparing NP arrays in high density on various paper substrates. In addition to their low cost, portability, flexibility, and biodegradability, plasmonic test paper can be burned after detecting contagious biomolecules, making them safe and eco-friendly.

Analysis of uncertainties and detection limits for the double measurement method of {sup 90}Sr and {sup 89}Sr

Energy Technology Data Exchange (ETDEWEB)

Herranz, M., E-mail: m.herranz@ehu.es [Department of Nuclear Engineering and Fluid Mechanics, University of the Basque Country (UPV/EHU), Alameda de Urquijo s/n 48013 Bilbao (Spain); Idoeta, R.; Legarda, F. [Department of Nuclear Engineering and Fluid Mechanics, University of the Basque Country (UPV/EHU), Alameda de Urquijo s/n 48013 Bilbao (Spain)

2011-08-15

The determination process of the {sup 90}Sr and {sup 89}Sr contents in a sample, although it involves their radiochemical isolation, results always in a complex measurement process due to the interferences among their respective beta emissions and also among those of the daughter of {sup 90}Sr, {sup 90}Y, a beta emitter as well. In this paper, the process consisting in a double measurement method after the Sr radiochemical isolation is analyzed, developing the formulae to obtain activity concentrations, uncertainties and detection limits. A study of the trend of uncertainties and detection limits as function of the time in which the first measurement since the isolation is done, the delay between the two measurements and the activity concentration of each strontium isotope in the sample is carried out as well. Results show that with a very precise determination of the times involved in the whole process (isolation, measurement and duration of measurements) this method permits a reliable assessment of both strontium radioisotopes. The quicker the first measurement since the isolation is done and the longer the delay between measurements is chosen, the lower are the detection limits and the uncertainties of the activities obtained. - Highlights: > The double measurement method for {sup 90}Sr and {sup 89}Sr determination is analysed. > Uncertainties and detection limits are determined and their dependences studied. > Proposals for the optimization of the method are given.

Direct and simultaneous detection of organic and inorganic ingredients in herbal powder preparations by Fourier transform infrared microspectroscopic imaging.

Science.gov (United States)

Chen, Jian-Bo; Sun, Su-Qin; Tang, Xu-Dong; Zhang, Jing-Zhao; Zhou, Qun

2016-08-05

Herbal powder preparation is a kind of widely-used herbal product in the form of powder mixture of herbal ingredients. Identification of herbal ingredients is the first and foremost step in assuring the quality, safety and efficacy of herbal powder preparations. In this research, Fourier transform infrared (FT-IR) microspectroscopic identification method is proposed for the direct and simultaneous recognition of multiple organic and inorganic ingredients in herbal powder preparations. First, the reference spectrum of characteristic particles of each herbal ingredient is assigned according to FT-IR results and other available information. Next, a statistical correlation threshold is determined as the lower limit of correlation coefficients between the reference spectrum and a larger number of calibration characteristic particles. After validation, the reference spectrum and correlation threshold can be used to identify herbal ingredient in mixture preparations. A herbal ingredient is supposed to be present if correlation coefficients between the reference spectrum and some sample particles are above the threshold. Using this method, all kinds of herbal materials in powder preparation Kouqiang Kuiyang San are identified successfully. This research shows the potential of FT-IR microspectroscopic identification method for the accurate and quick identification of ingredients in herbal powder preparations. Copyright © 2016 Elsevier B.V. All rights reserved.

Soybean and lactose in meat products and preparations sampled at retail

Directory of Open Access Journals (Sweden)

Filomena Piccolo

2016-06-01

Full Text Available Food allergies and intolerances have increased during the last decades and regulatory authorities have taken different measures to prevent and manage consumers’ adverse reactions, including correct labelling of foods. Aim of this work was to search for soybean and lactose in meat products and meat preparations taken from retail in some provinces of Campania Region (Southern Italy and to evaluate the food labels compliance with Regulation (EU n.1169/2011. Soybean and lactose were searched using commercial kits in n. 58 samples of meat products produced in or distributed by 19 establishments, and in n. 55 samples of meat products and n. 8 of meat preparations produced in 21 plants. All samples were selected on the basis of the absence of any information on the labels about the presence of the two searched allergens, with the exception of n. 5 samples tested for lactose. Traces of soybean were detected in 50 out of the 58 examined samples, at concentrations up to 0.93 mg kg–1. Only two samples contained levels above the detection limit of 0.31 mg kg–1. Lactose levels ranging from 0.11 to 2.95 g/100 g, i.e. above the detection limit, were found in all the tested samples (n. 63. The results of the present research underline the need for careful controls and planning by operators as part of the self-control plans, and deserve attention from the competent authorities considering not only the consumers’ health but also the great attention media pay to regulations providing consumers with information on food.

Lower limit of detection: definition and elaboration of a proposed position for radiological effluent and environmental measurements

International Nuclear Information System (INIS)

Currie, L.A.

1984-09-01

A manual is provided to define and illustrate a proposed use of the Lower Limit of Detection (LLD) for Radiological Effluent and Environmental Measurements. The manual contains a review of information regarding LLD practices gained from site visits; a review of the literature and a summary of basic principles underlying the concept of detection in Nuclear and Analytical Chemistry; a detailed presentation of the application of LLD principles to a range of problem categories (simple counting to multinuclide spectroscopy), including derivations, equations, and numerical examples; and a brief examination of related issues such as reference samples, numerical quality control, and instrumental limitations. An appendix contains a summary of notation and terminology, a bibliography, and worked-out examples. 100 references, 10 figures, 7 tables

Preparation and evaluation of Exendin radio conjugates for detecting insulinomas and gastrinomas by molecular nuclear medicine techniques

International Nuclear Information System (INIS)

Medina G, V.

2015-01-01

The gastro-entero-pancreatic neuroendocrine tumors (GEP-NET) are named based on the secreted hormones. Among them, the insulinomas and gastrinomas represent a diagnostic challenge because of their slow metabolic rate, small size and anatomical location that have limited their detection in some imaging procedures. About 90% of insulinomas are benign and 10% are malignant. Benign insulinomas express the glucagon-like peptide-1 receptor (GLP-1R) and low levels of somatostatin receptors (SSTR), while malignant insulinomas over express SSTR or GLP-1R in low levels. A kit for the preparation of Lys 27 ( 99m Tc-EDDA/HYNIC)-Exendin(9-39)/ 99m Tc-EDDA/HYNIC-Tyr 3 -Octreotide was developed to detect 100% of gastrinomas and insulinomas. In order to reach this aim, the peptides were radiolabeled and characterized. Stability studies will be completed and the in vitro and in vivo behavior was evaluated. The Lys 27 ( 99m Tc-EDDA/HYNIC)-Exendin(9-39)/ 99m Tc-EDDA/HYNIC-Tyr 3 -Octreotide can be labeled with 99m Tc, obtaining high radiochemical purities (>94%), high stability in human serum and affinity to GLP-1 and SST-2 receptor. This new formulation showed properties suitable for use as a target-specific agent for molecular imaging of GLP-1R/SSTR positive tumors. In vivo micro-SPECT/CT images of Lys 27 ( 99m Tc-EDDA/HYNIC)-Exendin(9-39), 99m Tc-EDDA/HYNIC-Tyr 3 -Octreotide and of the pharmaceutical formulation Lys 27 ( 99m Tc-EDDA/HYNIC)-Exendin(9-39)/ 99m Tc-EDDA/HYNIC-Tyr 3 -Octreotide showed the main elimination pathways, and tumors higher uptake compared to the background tissues. The biodistribution and imaging studies demonstrated properties suitable for its use as a target-specific agent for the simultaneous molecular imaging of GLP-1R and SSTR. (Author)

Preparation of novel silver nanoplates/graphene composite and their application in vanillin electrochemical detection

Energy Technology Data Exchange (ETDEWEB)

Huang, Linhong [Fujian Key Lab of Medical Instrument and Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); Institute of Research for Functional Materials, Fuzhou University, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); College of Chemistry and Chemical Engineering, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); Hou, Keyu; Jia, Xiao [Institute of Research for Functional Materials, Fuzhou University, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); College of Chemistry and Chemical Engineering, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); Pan, Haibo, E-mail: hbpan@fzu.edu.cn [Fujian Key Lab of Medical Instrument and Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); Institute of Research for Functional Materials, Fuzhou University, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); College of Chemistry and Chemical Engineering, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); Du, Min [Fujian Key Lab of Medical Instrument and Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China)

2014-05-01

Hexagonal Ag nanoplates (NPs) were synthesized by polyvinylpyrrolidone (PVP) and trisodium citrate (TSC) which selectively absorbed to Ag (100) and Ag (111) surfaces, then were anchored to graphene (GN) to form novel Ag NPs/GN composite. The thickness of Ag NPs is ∼ 4 nm and the length is 18–66 nm. Transmission electron microscopy (TEM) image shows that the plates are f-c-c crystals containing {111} facets on their two planar surfaces. Zeta potential indicated that the surface of Ag NPs/GN is negatively charged while vanillin is positively charged. Thus Ag NPs/GN modified on glass carbon electrodes (GCE) allowed abundant adsorption for vanillin and electron transfer between vanillin and Ag NPs/GN/GCE. Square wave voltammetry (SWV) results indicated that the over potential on Ag NPs/GN/GCE negatively shifts 52 mV than that on Ag NPs/GCE. Ag NPs/GN with enhanced surface area and good conductivity exhibited an excellent electrocatalytic activity toward the oxidation of vanillin. The corresponding linear range was estimated to be from 2 to 100 μM (R{sup 2} = 0.998), and the detection limit is 3.32 × 10{sup −7} M (S/N = 3). The as-prepared vanillin sensor exhibits good selectivity and potential application in practical vanillin determination. - Highlights: • Hexagonal Ag nanoplates were synthesized by controlling of PVP and trisodium citrate. • Ag nanoplates/GN composite allowed adsorption and electron transfer of vanillin. • The composite with good dispersion exhibits enhanced surface area and good catalysis. • Vanillin on the Ag NPs/GN/GCE shows high sensitivity and selectivity.

Preparation of novel silver nanoplates/graphene composite and their application in vanillin electrochemical detection

International Nuclear Information System (INIS)

Huang, Linhong; Hou, Keyu; Jia, Xiao; Pan, Haibo; Du, Min

2014-01-01

Hexagonal Ag nanoplates (NPs) were synthesized by polyvinylpyrrolidone (PVP) and trisodium citrate (TSC) which selectively absorbed to Ag (100) and Ag (111) surfaces, then were anchored to graphene (GN) to form novel Ag NPs/GN composite. The thickness of Ag NPs is ∼ 4 nm and the length is 18–66 nm. Transmission electron microscopy (TEM) image shows that the plates are f-c-c crystals containing {111} facets on their two planar surfaces. Zeta potential indicated that the surface of Ag NPs/GN is negatively charged while vanillin is positively charged. Thus Ag NPs/GN modified on glass carbon electrodes (GCE) allowed abundant adsorption for vanillin and electron transfer between vanillin and Ag NPs/GN/GCE. Square wave voltammetry (SWV) results indicated that the over potential on Ag NPs/GN/GCE negatively shifts 52 mV than that on Ag NPs/GCE. Ag NPs/GN with enhanced surface area and good conductivity exhibited an excellent electrocatalytic activity toward the oxidation of vanillin. The corresponding linear range was estimated to be from 2 to 100 μM (R 2 = 0.998), and the detection limit is 3.32 × 10 −7 M (S/N = 3). The as-prepared vanillin sensor exhibits good selectivity and potential application in practical vanillin determination. - Highlights: • Hexagonal Ag nanoplates were synthesized by controlling of PVP and trisodium citrate. • Ag nanoplates/GN composite allowed adsorption and electron transfer of vanillin. • The composite with good dispersion exhibits enhanced surface area and good catalysis. • Vanillin on the Ag NPs/GN/GCE shows high sensitivity and selectivity

Amorphous semiconductors for particle detection: Physical and technical limits and possibilities

International Nuclear Information System (INIS)

Equer, B.; Karar, A.

1989-01-01

Amorphous silicon is used, at an industrial level, in at least three different fields of application: photovoltaic cells, flat TV screens and line scanners for image processing. In the last two cases, thin film transistors (TFT) are produced with the same technology. Particle detection with amorphous silicon has been demonstrated, but present performances are limited to ionizing particles. In this paper, we discuss the physical basis of amorphous semiconductors and the possible future development that can be expected on the basis of the existing technology. It is concluded that substitution of amorphous for crystalline silicon brings no clear advantage, if possible at all. Positive assets are to be found in using specific properties of thin layers: large area structures like arrays of photodiodes with associated readout are in the state of the art; vertical structures alternating layers of differently doped materials and/or of different semiconductors can be produced by the same technique. The development of large area pixel detectors is technically feasible but requires a very large effort. A joint development effort with industries involved in X-ray detection and 2D photodetectors might be the most appropriate solution. (orig.)

Current Technical Approaches for the Early Detection of Foodborne Pathogens: Challenges and Opportunities

Directory of Open Access Journals (Sweden)

Il-Hoon Cho

2017-09-01

Full Text Available The development of novel and high-tech solutions for rapid, accurate, and non-laborious microbial detection methods is imperative to improve the global food supply. Such solutions have begun to address the need for microbial detection that is faster and more sensitive than existing methodologies (e.g., classic culture enrichment methods. Multiple reviews report the technical functions and structures of conventional microbial detection tools. These tools, used to detect pathogens in food and food homogenates, were designed via qualitative analysis methods. The inherent disadvantage of these analytical methods is the necessity for specimen preparation, which is a time-consuming process. While some literature describes the challenges and opportunities to overcome the technical issues related to food industry legal guidelines, there is a lack of reviews of the current trials to overcome technological limitations related to sample preparation and microbial detection via nano and micro technologies. In this review, we primarily explore current analytical technologies, including metallic and magnetic nanomaterials, optics, electrochemistry, and spectroscopy. These techniques rely on the early detection of pathogens via enhanced analytical sensitivity and specificity. In order to introduce the potential combination and comparative analysis of various advanced methods, we also reference a novel sample preparation protocol that uses microbial concentration and recovery technologies. This technology has the potential to expedite the pre-enrichment step that precedes the detection process.

Current Technical Approaches for the Early Detection of Foodborne Pathogens: Challenges and Opportunities.

Science.gov (United States)

Cho, Il-Hoon; Ku, Seockmo

2017-09-30

The development of novel and high-tech solutions for rapid, accurate, and non-laborious microbial detection methods is imperative to improve the global food supply. Such solutions have begun to address the need for microbial detection that is faster and more sensitive than existing methodologies (e.g., classic culture enrichment methods). Multiple reviews report the technical functions and structures of conventional microbial detection tools. These tools, used to detect pathogens in food and food homogenates, were designed via qualitative analysis methods. The inherent disadvantage of these analytical methods is the necessity for specimen preparation, which is a time-consuming process. While some literature describes the challenges and opportunities to overcome the technical issues related to food industry legal guidelines, there is a lack of reviews of the current trials to overcome technological limitations related to sample preparation and microbial detection via nano and micro technologies. In this review, we primarily explore current analytical technologies, including metallic and magnetic nanomaterials, optics, electrochemistry, and spectroscopy. These techniques rely on the early detection of pathogens via enhanced analytical sensitivity and specificity. In order to introduce the potential combination and comparative analysis of various advanced methods, we also reference a novel sample preparation protocol that uses microbial concentration and recovery technologies. This technology has the potential to expedite the pre-enrichment step that precedes the detection process.

Enhancement of laser-induced breakdown spectroscopy (LIBS) Detection limit using a low-pressure and short-pulse laser-induced plasma process.

Science.gov (United States)

Wang, Zhen Zhen; Deguchi, Yoshihiro; Kuwahara, Masakazu; Yan, Jun Jie; Liu, Ji Ping

2013-11-01

Laser-induced breakdown spectroscopy (LIBS) technology is an appealing technique compared with many other types of elemental analysis because of the fast response, high sensitivity, real-time, and noncontact features. One of the challenging targets of LIBS is the enhancement of the detection limit. In this study, the detection limit of gas-phase LIBS analysis has been improved by controlling the pressure and laser pulse width. In order to verify this method, low-pressure gas plasma was induced using nanosecond and picosecond lasers. The method was applied to the detection of Hg. The emission intensity ratio of the Hg atom to NO (IHg/INO) was analyzed to evaluate the LIBS detection limit because the NO emission (interference signal) was formed during the plasma generation and cooling process of N2 and O2 in the air. It was demonstrated that the enhancement of IHg/INO arose by decreasing the pressure to a few kilopascals, and the IHg/INO of the picosecond breakdown was always much higher than that of the nanosecond breakdown at low buffer gas pressure. Enhancement of IHg/INO increased more than 10 times at 700 Pa using picosecond laser with 35 ps pulse width. The detection limit was enhanced to 0.03 ppm (parts per million). We also saw that the spectra from the center and edge parts of plasma showed different features. Comparing the central spectra with the edge spectra, IHg/INO of the edge spectra was higher than that of the central spectra using the picosecond laser breakdown process.

A facile one-pot preparation of Co3O4/g-C3N4 heterojunctions with excellent electrocatalytic activity for the detection of environmental phenolic hormones

Science.gov (United States)

Sun, Yanjuan; Jiang, Jizhou; Liu, Yi; Wu, Shengli; Zou, Jing

2018-02-01

The Co3O4/g-C3N4 heterojunctions were prepared by a facile one-pot thermal decomposition technique. Compared with g-C3N4, it was found that Co3O4/g-C3N4 heterojunctions possessed a higher Brunner-Emmet-Teller (BET) surface area, which was beneficial to the diffusion of aim molecules on the electrode surfaces. And the optimal Co3O4/g-C3N4 heterojunctions exhibited a narrower band gap and a higher donor density, resulting in an excellent electrocatalytic activity for environmental phenolic hormones. Moreover, the Co3O4/g-C3N4 heterojunctions were used for the electrochemical sensing of environmental phenolic hormones such as bisphenol A, pentachlorophenol, p-nitrophenol and octylphenol. All detection ranges reached three orders of magnitude, showing a lower limit of detection of 10-9 mol L-1. So, sensitivity and accurate determination of environmental phenolic hormones in real water samples may use this Co3O4/g-C3N4 heterojunctions modified electrode.

A novel dNTP-limited PCR and HRM assay to detect Williams-Beuren syndrome.

Science.gov (United States)

Zhang, Lichen; Zhang, Xiaoqing; You, Guoling; Yu, Yongguo; Fu, Qihua

2018-06-01

Williams-Beuren syndrome (WBS) is caused by a microdeletion of chromosome arm 7q11.23. A rapid and inexpensive genotyping method to detect microdeletion on 7q11.23 needs to be developed for the diagnosis of WBS. This study describes the development of a new type of molecular diagnosis method to detect microdeletion on 7q11.23 based upon high-resolution melting (HRM). Four genes on 7q11.23 were selected as the target genes for the deletion genotyping. dNTP-limited duplex PCR was used to amplify the reference gene, CFTR, and one of the four genes respectively on 7q11.23. An HRM assay was performed on the PCR products, and the height ratio of the negative derivative peaks between the target gene and reference gene was employed to analyze the copy number variation of the target region. A new genotyping method for detecting 7q11.23 deletion was developed based upon dNTP-limited PCR and HRM, which cost only 96 min. Samples from 15 WBS patients and 12 healthy individuals were genotyped by this method in a blinded fashion, and the sensitivity and specificity was 100% (95% CI, 0.80-1, and 95% CI, 0.75-1, respectively) which was proved by CytoScan HD array. The HRM assay we developed is an rapid, inexpensive, and highly accurate method for genotyping 7q11.23 deletion. It is potentially useful in the clinical diagnosis of WBS. Copyright © 2018 Elsevier B.V. All rights reserved.

Neutron activation analysis detection limits using 252Cf sources

International Nuclear Information System (INIS)

DiPrete, D.P.; Sigg, R.A.

2000-01-01

The Savannah River Technology Center (SRTC) developed a neutron activation analysis (NAA) facility several decades ago using low-flux 252 Cf neutron sources. Through this time, the facility has addressed areas of applied interest in managing the Savannah River Site (SRS). Some applications are unique because of the site's operating history and its chemical-processing facilities. Because sensitivity needs for many applications are not severe, they can be accomplished using an ∼6-mg 252 Cf NAA facility. The SRTC 252 Cf facility continues to support applied research programs at SRTC as well as other SRS programs for environmental and waste management customers. Samples analyzed by NAA include organic compounds, metal alloys, sediments, site process solutions, and many other materials. Numerous radiochemical analyses also rely on the facility for production of short-lived tracers, yielding by activation of carriers and small-scale isotope production for separation methods testing. These applications are more fully reviewed in Ref. 1. Although the flux [approximately2 x 10 7 n/cm 2 ·s] is low relative to reactor facilities, more than 40 elements can be detected at low and sub-part-per-million levels. Detection limits provided by the facility are adequate for many analytical projects. Other multielement analysis methods, particularly inductively coupled plasma atomic emission and inductively coupled plasma mass spectrometry, can now provide sensitivities on dissolved samples that are often better than those available by NAA using low-flux isotopic sources. Because NAA allows analysis of bulk samples, (a) it is a more cost-effective choice when its sensitivity is adequate than methods that require digestion and (b) it eliminates uncertainties that can be introduced by digestion processes

A program for the a priori evaluation of detection limits in instrumental neutron activation analysis using a SLOWPOKE II reactor

International Nuclear Information System (INIS)

Galinier, J.L.; Zikovsky, L.

1982-01-01

A program that permits the a priori calculation of detection limits in monoelemental matrices, adapted to instrumental neutron activation analysis using a SLOWPOKE II reactor, is described. A simplified model of the gamma spectra is proposed. Products of (n,p) and (n,α) reactions induced by the fast components of the neutron flux that accompanies the thermal flux at the level of internal irradiation sites in the reactor have been included in the list of interfering radionuclides. The program calculates in a systematic way the detection limits of 66 elements in an equal number of matrices using 153 intermediary radionuclides. Experimental checks carried out with silicon (for short lifetimes) and aluminum and magnesium (for intermediate lifetimes) show satisfactory agreement with the calculations. These results show in particular the importance of the contribution of the (n,p) and (n,α) reactions in the a priori evaluation of detection limits with a SLOWPOKE type reactor [fr

Electrochemical Aptamer Scaffold Biosensors for Detection of Botulism and Ricin Proteins.

Science.gov (United States)

Daniel, Jessica; Fetter, Lisa; Jett, Susan; Rowland, Teisha J; Bonham, Andrew J

2017-01-01

Electrochemical DNA (E-DNA) biosensors enable the detection and quantification of a variety of molecular targets, including oligonucleotides, small molecules, heavy metals, antibodies, and proteins. Here we describe the design, electrode preparation and sensor attachment, and voltammetry conditions needed to generate and perform measurements using E-DNA biosensors against two protein targets, the biological toxins ricin and botulinum neurotoxin. This method can be applied to generate E-DNA biosensors for the detection of many other protein targets, with potential advantages over other systems including sensitive detection limits typically in the nanomolar range, real-time monitoring, and reusable biosensors.

Re-evaluation of groundwater monitoring data for glyphosate and bentazone by taking detection limits into account

DEFF Research Database (Denmark)

Hansen, Claus Toni; Ritz, Christian; Gerhard, Daniel

2015-01-01

.e. samples with concentrations below the detection limit, as left-censored observations. The median calculated pesticide concentrations are shown to be reduced 10(4) to 10(5) fold for two representative herbicides (glyphosate and bentazone) relative to the median concentrations based upon observations above...

Reactor operation plan preparing device

International Nuclear Information System (INIS)

Sano, Hiroki; Maruyama, Hiromi; Kinoshita, Mitsuo; Fukuzaki, Koji; Banto, Masaru; Fukazawa, Yukihisa.

1993-01-01

The device comprises a means for retrieving a control rod pattern capable of satisfying a thermal limit upon aimed power/minimum flow rate and providing minimum xenon and a control rod pattern maximum xenon. It further comprises a means for selecting a control rod pattern corresponding to a xenon equilibrium condition, and selecting a control rod which provides a greater thermal margin to provide a control rod operation sequence for each of the patterns. Further, the device comprises an outline plan preparing means and a correction means therefor, a simplified sequence table reference means operated along with sequence change, an operation limit region input means, a control rod operation preferential region changing means, a thermal margin evaluation region and an input means. This can automatically prepare the operation plan, decrease the times for preparation of detailed plans by using the outline plan preparing function, thereby enabling to remarkably shorten the time for preparing of an operation plan. (N.H.)

On the definition of the detection limit for non-selective determination of low activities

International Nuclear Information System (INIS)

Tschurlovits, M.

1977-01-01

Based on the latest published results, a detection limit which is easy to use in practical work without intensive consideration of counting statistics, is presented. The primary application of the given definition is the determination of gross activity. In the definition the error of the second kind as well as one-sided boundedness of the normal distribution are included. The results are given in graphical form. (orig.) [de

Internal Dosimetry Monitoring- Detection Limits for a Selected Set of Radionuclides and Their Translation Into Committed Effective Dose

International Nuclear Information System (INIS)

Brandl, A.; Hrnecek, E.; Steger, F.

2004-01-01

To harmonize the practice of internal dosimetry monitoring across the country, the Austrian Standards Institute is currently drafting a new set of standards which are concerned with occupational incorporation monitoring of individuals handling non-sealed radioactive material. This set of standards is expected to consist of three parts discussing the general necessity and frequency, the requirements for monitoring institutions, and the determination and rigorous calculation of committed effective dose after incorporation of radioactive material, respectively. Considerations of the requirements for routine monitoring laboratories have led to an evaluation of the detection limits for routine monitoring equipment. For a selected set of radionuclides, these detection limits are investigated in detail. The main emphasis is placed on the decay chains of naturally occurring radionuclides showing some significant potential for being out of equilibrium due to chemical processes in certain mining industries. The radionuclides considered in this paper are 226Ra, 228Ra, 228Th, 232Th, 234U, 235U, and 238U. Given the routine monitoring intervals of the Austrian Standard, these detection limits are translated into information on committed effective dose. This paper investigates whether routine monitoring equipment is sufficient to ensure compliance with EC directive 96/29/Euratom for this selected set of radionuclides. (Author) 9 refs

Separation followed by direct SERS detection of explosives on a novel black silicon multifunctional nanostructured surface prepared in a microfluidic channel

DEFF Research Database (Denmark)

Talian, Ivan; Hübner, Jörg

2013-01-01

The article describes the multifunctionality of a novel black silicon (BS) nanostructured surface covered with a thin layer of noble metal prepared in the a microfluidic channel. It is focused on the separation properties of the BS substrate with direct detection of the separated analytes utilizing...

Comparison of detection limits in environmental analysis--is it possible? An approach on quality assurance in the lower working range by verification.

Science.gov (United States)

Geiss, S; Einax, J W

2001-07-01

Detection limit, reporting limit and limit of quantitation are analytical parameters which describe the power of analytical methods. These parameters are used for internal quality assurance and externally for competing, especially in the case of trace analysis in environmental compartments. The wide variety of possibilities for computing or obtaining these measures in literature and in legislative rules makes any comparison difficult. Additionally, a host of terms have been used within the analytical community to describe detection and quantitation capabilities. Without trying to create an order for the variety of terms, this paper is aimed at providing a practical proposal for answering the main questions for the analysts concerning quality measures above. These main questions and related parameters were explained and graphically demonstrated. Estimation and verification of these parameters are the two steps to get real measures. A rule for a practical verification is given in a table, where the analyst can read out what to measure, what to estimate and which criteria have to be fulfilled. In this manner verified parameters detection limit, reporting limit and limit of quantitation now are comparable and the analyst himself is responsible to the unambiguity and reliability of these measures.

Improved detection limits for electrospray ionization on a magnetic sector mass spectrometer by using an array detector.

Science.gov (United States)

Cody, R B; Tamura, J; Finch, J W; Musselman, B D

1994-03-01

Array detection was compared with point detection for solutions of hen egg-white lysozyme, equine myoglobin, and ubiquitin analyzed by electrospray ionization with a magnetic sector mass spectrometer. The detection limits for samples analyzed by using the array detector system were at least 10 times lower than could be achieved by using a point detector on the same mass spectrometer. The minimum detectable quantity of protein corresponded to a signal-to-background ratio of approximately 2∶1 for a 500 amol/μL solution of hen egg-white lysozyme. However, the ultimate practical sample concentrations appeared to be in the 10-100 fmol/μL range for the analysis of dilute solutions of relatively pure proteins or simple mixtures.

Capillary electrophoresis microchip coupled with on-line chemiluminescence detection

International Nuclear Information System (INIS)

Su Rongguo; Lin Jinming; Qu Feng; Chen Zhifeng; Gao Yunhua; Yamada, Masaaki

2004-01-01

In the present work, chemiluminescence detection was integrated with capillary electrophoresis microchip. The microchip was designed on the principle of flow-injection chemiluminescence system and capillary electrophoresis. It has three main channels, five reservoirs and a detection cell. As model samples, dopamine and catechol were separated and detected using a permanganate chemiluminescent system on the prepared microchip. The samples were electrokinetically injected into the double-T cross section, separated in the separation channel, and then oxidized by chemiluminescent reagent delivered by a home-made micropump to produce light in the detection cell. The electroosmotic flow could be smoothly coupled with the micropump flow. The detection limits for dopamine and catechol were 20.0 and 10.0 μM, respectively. Successful separation and detection of dopamine and catechol demonstrated the distinct advantages of integration of chemiluminescent detection on a microchip for rapid and sensitive analysis

Optofluidic analysis system for amplification-free, direct detection of Ebola infection

Science.gov (United States)

Cai, H.; Parks, J. W.; Wall, T. A.; Stott, M. A.; Stambaugh, A.; Alfson, K.; Griffiths, A.; Mathies, R. A.; Carrion, R.; Patterson, J. L.; Hawkins, A. R.; Schmidt, H.

2015-09-01

The massive outbreak of highly lethal Ebola hemorrhagic fever in West Africa illustrates the urgent need for diagnostic instruments that can identify and quantify infections rapidly, accurately, and with low complexity. Here, we report on-chip sample preparation, amplification-free detection and quantification of Ebola virus on clinical samples using hybrid optofluidic integration. Sample preparation and target preconcentration are implemented on a PDMS-based microfluidic chip (automaton), followed by single nucleic acid fluorescence detection in liquid-core optical waveguides on a silicon chip in under ten minutes. We demonstrate excellent specificity, a limit of detection of 0.2 pfu/mL and a dynamic range of thirteen orders of magnitude, far outperforming other amplification-free methods. This chip-scale approach and reduced complexity compared to gold standard RT-PCR methods is ideal for portable instruments that can provide immediate diagnosis and continued monitoring of infectious diseases at the point-of-care.

Graphene quantum dots prepared from glucose as optical sensor for glucose

Energy Technology Data Exchange (ETDEWEB)

Shehab, Mona, E-mail: mona_shehab@alexu.edu.eg [Materials Science Department, Institute of Graduate Studies & Research, Alexandria University (Egypt); General Bureau of Beheira Governorate, Damanhour, Beheira 22111 (Egypt); Ebrahim, Shaker; Soliman, Moataz [Materials Science Department, Institute of Graduate Studies & Research, Alexandria University (Egypt)

2017-04-15

Quantum Dots (QDs) show promise materials for many technological applications. In this work we utilized a simple route to prepare graphene quantum dots (GQDs) using glucose carbonization. GQDs functionalized with phenylboronic acid receptors were employed as a sensing material for a nonenzymatic glucose sensor. Photoluminance spectra of GQDs were used as a property of optical sensor for glucose. GQDs considered as a good sensing probe because of its low toxicity, high photoluminance, water solubility and excelent photochemical properties. The prepared GQDs were characterized using UV-visible, Raman and photoluminance spectroscopies, X-ray diffraction and high resolution transmission electron microscopy (HRTEM). HRTEM micrographs confirmed the preparation of 7–10 nm GQDs and the emission peak of the GQDs appeared at 450 nm. The developed sensor has linear response to glucose over a concentration range of 4–40 mM with a correlation coefficient of 0.97 and a low detection limit of approximately 3.0 mM.

The preparation of tourists to the ski sports tours in a limited time in order to prevent injuries and accidents

Directory of Open Access Journals (Sweden)

A.N. Toporkov

2014-08-01

Full Text Available Purpose: compare indicators of testing tourist skiers at different stages of the preparatory period to ski sports hike of third grade. Determine the effectiveness of training programs created to the tourists Categorical ski sports to prevent injuries and accidents in a limited time. Material: The study involved 13 people aged from 21 to 65 (4 women and 9 men with different experiences of hiking trails and various levels of total tourist preparedness. Results: The test results obtained before beginning the process of preparation are treated upon its completion, and immediately after passing categorical hike. In practice, the effectiveness of the proposed training programs of tourists to ski sports tours is proved. Conclusions : The created program can be recommended to tourist clubs, associations and organizations as the base in preparation for ski sports campaigns for the prevention of accidents and injuries.

Preparation of anti-ciguatoxin monoclonal antibodies using synthetic haptens: sandwich ELISA detection of ciguatoxins.

Science.gov (United States)

Tsumuraya, Takeshi; Fujii, Ikuo; Hirama, Masahiro

2014-01-01

Ciguatera fish poisoning (CFP) is a form of food poisoning caused by the consumption of fish that have accumulated a type of sodium channel activator toxin called ciguatoxins (CTXs), which are produced by dinoflagellates of the genus Gambierdiscus through the food chain. CFP affects more than 50000 people each year. The extremely low level of CTXs in tainted fish has hampered the development of antibodies for the detection of these toxins. Monoclonal antibodies (mAbs) specific against major congeners of CTX3C, 51-hydroxyCTX3C, CTX1B, and 54-deoxyCTX1B were prepared by immunization of mice with protein conjugates of rationally designed synthetic haptens in place of the natural toxins. We found that haptenic groups possessing a surface area larger than 400 angstroms2 were required to produce mAbs that can bind strongly to CTXs. Direct sandwich ELISA utilizing two different monoclonal antibodies that bind specifically to one of the two wings of a CTX were established to detect CTXs. No cross-reactivity was observed against the other marine toxins tested, including brevetoxin A, brevetoxin B, okadaic acid, and maitotoxin.

Generalized linear mixed model for binary outcomes when covariates are subject to measurement errors and detection limits.

Science.gov (United States)

Xie, Xianhong; Xue, Xiaonan; Strickler, Howard D

2018-01-15

Longitudinal measurement of biomarkers is important in determining risk factors for binary endpoints such as infection or disease. However, biomarkers are subject to measurement error, and some are also subject to left-censoring due to a lower limit of detection. Statistical methods to address these issues are few. We herein propose a generalized linear mixed model and estimate the model parameters using the Monte Carlo Newton-Raphson (MCNR) method. Inferences regarding the parameters are made by applying Louis's method and the delta method. Simulation studies were conducted to compare the proposed MCNR method with existing methods including the maximum likelihood (ML) method and the ad hoc approach of replacing the left-censored values with half of the detection limit (HDL). The results showed that the performance of the MCNR method is superior to ML and HDL with respect to the empirical standard error, as well as the coverage probability for the 95% confidence interval. The HDL method uses an incorrect imputation method, and the computation is constrained by the number of quadrature points; while the ML method also suffers from the constrain for the number of quadrature points, the MCNR method does not have this limitation and approximates the likelihood function better than the other methods. The improvement of the MCNR method is further illustrated with real-world data from a longitudinal study of local cervicovaginal HIV viral load and its effects on oncogenic HPV detection in HIV-positive women. Copyright © 2017 John Wiley & Sons, Ltd.

Applying ISO 11929:2010 Standard to detection limit calculation in least-squares based multi-nuclide gamma-ray spectrum evaluation

Energy Technology Data Exchange (ETDEWEB)

Kanisch, G., E-mail: guenter.kanisch@hanse.net

2017-05-21

The concepts of ISO 11929 (2010) are applied to evaluation of radionuclide activities from more complex multi-nuclide gamma-ray spectra. From net peak areas estimated by peak fitting, activities and their standard uncertainties are calculated by weighted linear least-squares method with an additional step, where uncertainties of the design matrix elements are taken into account. A numerical treatment of the standard's uncertainty function, based on ISO 11929 Annex C.5, leads to a procedure for deriving decision threshold and detection limit values. The methods shown allow resolving interferences between radionuclide activities also in case of calculating detection limits where they can improve the latter by including more than one gamma line per radionuclide. The co'mmon single nuclide weighted mean is extended to an interference-corrected (generalized) weighted mean, which, combined with the least-squares method, allows faster detection limit calculations. In addition, a new grouped uncertainty budget was inferred, which for each radionuclide gives uncertainty budgets from seven main variables, such as net count rates, peak efficiencies, gamma emission intensities and others; grouping refers to summation over lists of peaks per radionuclide.

Analysis of background components in Ge-spectrometry and their influence on detection limits

Energy Technology Data Exchange (ETDEWEB)

Heusser, G [Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany)

1997-03-01

In low radioactivity measurements the system own background of the spectrometer is, besides the counting efficiency, the limiting factor for the achievable sensitivity. Since the latter is mostly fixed, background reduction is the only way to gain sensitivity, although it is inversely proportional only to the square root of the background rate but directly proportional to the counting efficiency. A thorough understanding of the background sources and their quantitative contribution helps to choose the most adequate suppression method in order to reach a certain required level of detection limit. For Ge-spectrometry the background can be reduced by 5 to 6 orders of magnitude compared to the unshielded case applying state-of-the-art techniques. This reduction factor holds for the continuous background spectrum as well as for the line background as demonstrated for a Ge detector of the Heidelberg-Moscow double beta decay experiment. (orig./DG)

Preparation of surface enhanced Raman substrate and its characterization

Science.gov (United States)

Liu, Y.; Wang, J. Y.; Wang, J. Q.

2017-10-01

Surface enhanced Raman spectroscopy (SERS) is a fast, convenient and highly sensitive detection technique, and preparing the good effect and repeatable substrate is the key to realize the trace amount and quantitative detection in the field of food safety detection. In this paper, a surface enhanced Raman substrate based on submicrometer silver particles structure was prepared by chemical deposition method, and characterized its structure and optical properties.

State preparation and detector effects in quantum measurements of rotation with circular polarization-entangled photons and photon counting

Science.gov (United States)

Cen, Longzhu; Zhang, Zijing; Zhang, Jiandong; Li, Shuo; Sun, Yifei; Yan, Linyu; Zhao, Yuan; Wang, Feng

2017-11-01

Circular polarization-entangled photons can be used to obtain an enhancement of the precision in a rotation measurement. In this paper, the method of entanglement transformation is used to produce NOON states in circular polarization from a readily generated linear polarization-entangled photon source. Detection of N -fold coincidences serves as the postselection and N -fold superoscillating fringes are obtained simultaneously. A parity strategy and conditional probabilistic statistics contribute to a better fringe, saturating the angle sensitivity to the Heisenberg limit. The impact of imperfect state preparation and detection is discussed both separately and jointly. For the separated case, the influence of each system imperfection is pronounced. For the joint case, the feasibility region for surpassing the standard quantum limit is given. Our work pushes the state preparation of circular polarization-entangled photons to the same level as that in the case of linear polarization. It is also confirmed that entanglement can be transformed into different frames for specific applications, serving as a useful scheme for using entangled sources.

Detection of enterotoxigenic Clostridium perfringens in meat samples by using molecular methods.

Science.gov (United States)

Kaneko, Ikuko; Miyamoto, Kazuaki; Mimura, Kanako; Yumine, Natsuko; Utsunomiya, Hirotoshi; Akimoto, Shigeru; McClane, Bruce A

2011-11-01

To prevent food-borne bacterial diseases and to trace bacterial contamination events to foods, microbial source tracking (MST) methods provide important epidemiological information. To apply molecular methods to MST, it is necessary not only to amplify bacterial cells to detection limit levels but also to prepare DNA with reduced inhibitory compounds and contamination. Isolates carrying the Clostridium perfringens enterotoxin gene (cpe) on the chromosome or a plasmid rank among the most important food-borne pathogens. Previous surveys indicated that cpe-positive C. perfringens isolates are present in only ∼5% of nonoutbreak food samples and then only at low numbers, usually less than 3 cells/g. In this study, four molecular assays for the detection of cpe-positive C. perfringens isolates, i.e., ordinary PCR, nested PCR, real-time PCR, and loop-mediated isothermal amplification (LAMP), were developed and evaluated for their reliability using purified DNA. For use in the artificial contamination of meat samples, DNA templates were prepared by three different commercial DNA preparation kits. The four molecular assays always detected cpe when >10³ cells/g of cpe-positive C. perfringens were present, using any kit. Of three tested commercial DNA preparation kits, the InstaGene matrix kit appeared to be most suitable for the testing of a large number of samples. By using the InstaGene matrix kit, the four molecular assays efficiently detected cpe using DNA prepared from enrichment culture specimens of meat samples contaminated with low numbers of cpe-positive C. perfringens vegetative cells or spores. Overall, the current study developed molecular assay protocols for MST to detect the contamination of foods with low numbers of cells, and at a low frequency, of cpe-positive C. perfringens isolates.

Detection of Enterotoxigenic Clostridium perfringens in Meat Samples by Using Molecular Methods▿

Science.gov (United States)

Kaneko, Ikuko; Miyamoto, Kazuaki; Mimura, Kanako; Yumine, Natsuko; Utsunomiya, Hirotoshi; Akimoto, Shigeru; McClane, Bruce A.

2011-01-01

To prevent food-borne bacterial diseases and to trace bacterial contamination events to foods, microbial source tracking (MST) methods provide important epidemiological information. To apply molecular methods to MST, it is necessary not only to amplify bacterial cells to detection limit levels but also to prepare DNA with reduced inhibitory compounds and contamination. Isolates carrying the Clostridium perfringens enterotoxin gene (cpe) on the chromosome or a plasmid rank among the most important food-borne pathogens. Previous surveys indicated that cpe-positive C. perfringens isolates are present in only ∼5% of nonoutbreak food samples and then only at low numbers, usually less than 3 cells/g. In this study, four molecular assays for the detection of cpe-positive C. perfringens isolates, i.e., ordinary PCR, nested PCR, real-time PCR, and loop-mediated isothermal amplification (LAMP), were developed and evaluated for their reliability using purified DNA. For use in the artificial contamination of meat samples, DNA templates were prepared by three different commercial DNA preparation kits. The four molecular assays always detected cpe when >103 cells/g of cpe-positive C. perfringens were present, using any kit. Of three tested commercial DNA preparation kits, the InstaGene matrix kit appeared to be most suitable for the testing of a large number of samples. By using the InstaGene matrix kit, the four molecular assays efficiently detected cpe using DNA prepared from enrichment culture specimens of meat samples contaminated with low numbers of cpe-positive C. perfringens vegetative cells or spores. Overall, the current study developed molecular assay protocols for MST to detect the contamination of foods with low numbers of cells, and at a low frequency, of cpe-positive C. perfringens isolates. PMID:21890671

Determination of the detection limit and decision threshold for ionizing radiation measurements. Part 2: Fundamentals and application to counting measurements with the influence of sample treatment

International Nuclear Information System (INIS)

2000-01-01

This part of ISO 11929 addresses the field of ionizing radiation measurements in which events (in particular pulses) on samples are counted after treating them (e.g. aliquotation, solution, enrichment, separation). It considers, besides the random character of radioactive decay and of pulse counting, all other influences arising from sample treatment, (e.g. weighing, enrichment, calibration or the instability of the test setup). ISO 11929 consists of the following parts, under the general title Determination of the detection limit and decision threshold for ionizing radiation measurements: Part 1: Fundamentals and application to counting measurements without the influence of sample treatment; Part 2: Fundamentals and application to counting measurements with the influence of sample treatment; Part 3: Fundamentals and application to counting measurements by high resolution gamma spectrometry, without the influence of sample treatment; Part 4: Fundamentals and application to measurements by use of linear scale analogue ratemeters, without the influence of sample treatment. This part of ISO 11929 was prepared in parallel with other International Standards prepared by WG 2 (now WG 17): ISO 11932:1996, Activity measurements of solid materials considered for recycling, re-use or disposal as non radioactive waste, and ISO 11929-1, ISO 11929-3 and ISO 11929-4 and is, consequently, complementary to these documents

Cytological preparations for molecular analysis: A review of technical procedures, advantages and limitations for referring samples for testing.

Science.gov (United States)

da Cunha Santos, G; Saieg, M A; Troncone, G; Zeppa, P

2018-04-01

Minimally invasive procedures such as endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) must yield not only good quality and quantity of material for morphological assessment, but also an adequate sample for analysis of molecular markers to guide patients to appropriate targeted therapies. In this context, cytopathologists worldwide should be familiar with minimum requirements for refereeing cytological samples for testing. The present manuscript is a review with comprehensive description of the content of the workshop entitled Cytological preparations for molecular analysis: pre-analytical issues for EBUS TBNA, presented at the 40th European Congress of Cytopathology in Liverpool, UK. The present review emphasises the advantages and limitations of different types of cytology substrates used for molecular analysis such as archival smears, liquid-based preparations, archival cytospin preparations and FTA (Flinders Technology Associates) cards, as well as their technical requirements/features. These various types of cytological specimens can be successfully used for an extensive array of molecular studies, but the quality and quantity of extracted nucleic acids rely directly on adequate pre-analytical assessment of those samples. In this setting, cytopathologists must not only be familiar with the different types of specimens and associated technical procedures, but also correctly handle the material provided by minimally invasive procedures, ensuring that there is sufficient amount of material for a precise diagnosis and correct management of the patient through personalised care. © 2018 John Wiley & Sons Ltd.

WE-H-207A-09: Theoretical Limits to Molecular Biomarker Detection Using Magnetic Nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Weaver, J [Dartmouth-Hitchcock Medical Center, Lebanon, NH (United States); Geisel School of Medicine, Dartmouth College, Hanover, NH (United States)

2016-06-15

Purpose: Estimate the limits of molecular biomarker detection using magnetic nanoparticle methods like in vivo ELISA. Methods: Magnetic nanoparticles in an alternating magnetic field produce a magnetization that can be detected at exceedingly low levels because the signal at the harmonic frequencies is uniquely produced by the nanoparticles. Because the magnetization can also be used to characterize the nanoparticle rotational freedom, the bound state can be found. If the nanoparticles are coated with molecules that bind the desired biomarker, the rotational freedom reflects the biomarker concentration. The irreducible noise limit is the thermal noise or Johnson noise of the tissue and the contrast that can be measured must be larger than that limit. The contrast produced is a function of the applied field and depends strongly on nanoparticle volume. We have estimated the contrast using a Langevin function of a single composite variable to approximate the full stochastic Langevin equation for nanoparticle dynamics. Results: The thermal noise for a bandwidth reasonable for spectroscopy suggests mid zeptomolar (10–21) to low attomolar (10–18) concentrations can be measured in a volume that is 10cm in scale. The suggested sensitivity is far below the physiologically concentrations of almost all critical biomarkers including cytokines (picomolar), hormones (nanomolar) and heat shock proteins. Conclusion: The sensitivity of in vivo ELISA concentration measurements should be sufficient to measure physiological concentrations of critical biomarkers like cytokines in vivo. Further the sensitivity should be sufficient to measure concentrations of other biomarkers that are six to eight orders of magnitude lower in concentration than immune signaling molecules like cytokines. NIH - 1U54CA151662-01 Department of Radiology.

A new manufacturing process to remove thrombogenic factors (II, VII, IX, X, and XI) from intravenous immunoglobulin gamma preparations.

Science.gov (United States)

Park, Dong Hwarn; Kang, Gil Bu; Kang, Dae Eun; Hong, Jeung Woon; Lee, Min Gyu; Kim, Ki Yong; Han, Jeung Whan

2017-01-01

Coagulation factors (II, VII, IX, X, and particularly XIa) remaining in high concentrations in intravenous immunoglobulin (IVIG) preparations can form thrombi, causing thromboembolic events, and in serious cases, result in death. Therefore, manufacturers of biological products must investigate the ability of their production processes to remove procoagulant activities. Previously, we were able to remove coagulation factors II, VII, IX, and X from our IVIG preparation through ethanol precipitation, but factor XIa, which plays an important role in thrombosis, remained in the intermediate products. Here, we used a chromatographic process using a new resin that binds with high capacity to IgG and removes procoagulant activities. The procoagulant activities were reduced to low levels as determined by the thrombin generation assay: 250 s, FXI/FXIa ELISA: <0.31 ng/mL. Even after spiking with FXIa at a concentration 32.5 times higher than the concentration in normal specimens, the procoagulant activities were below the detection limit (<0.31 ng/mL). These results demonstrate the ability of our manufacturing process to remove procoagulant activities to below the detection limit (except by NaPTT), suggesting a reduced risk of thromboembolic events that maybe potentially caused by our IVIG preparation. Copyright © 2016 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Evaluation of MidIR fibre optic reflectance: Detection limit, reproducibility and binary mixture discrimination

Science.gov (United States)

Sessa, Clarimma; Bagán, Héctor; García, José Francisco

2013-11-01

MidIR fibre optic reflectance (MidIR-FORS) is a promising analytical technique in the field of science conservation, especially because it is non-destructive. Another advantage of MidIR-FORS is that the obtained information is representative, as a large amount of spectral data can be collected. Although the technique has a high potential and is almost routinely applied, its quality parameters have not been thoroughly studied in the specific application of analysis of artistic materials. The objective of this study is to evaluate the instrumental capabilities of MidIR-FORS for the analysis of artwork materials in terms of detection limit, reproducibility, and mixture characterisation. The study has been focused on oil easel painting and several paints of known composition have been analysed. Paint layers include blue pigments not only because of their important role along art history, but also because their physical and spectroscopic characteristics allow a better evaluation of the MidIR-FORS capabilities. The results of the analysis indicate that MidIR-FORS supplies a signal affected by different factors, such as the optical, morphological and physical properties of the surface, in addition to the composition of materials analysed. Consequently, the detection limits established are relatively high for artistic objects (Prussian blue - PB 2.1-6.5%; Phthalocyanine blue - Pht 6.3-10.2%; synthetic Ultramarine blue - UM 12.1%) and may therefore lead to an incomplete description of the artwork. Reproducibility of the technique over time and across surface has been determined. The results show that the major sources of dispersion are the heterogeneity of the pigments distribution, physical features, and band shape distortions. The total dispersion is around 4% for the most intense bands (oil) and increases up to 26% when weak or overlapped bands are considered (PB, Pht, UM). The application of different pre-treatments (cutoff of fibres absorption, Savizky-Golay smoothing

Preparation of Environmental and Food Samples to Support the Heavy Metals Detection by Stripping Electrochemical

International Nuclear Information System (INIS)

Iswani S

2002-01-01

Preparation of environmental and food samples to support the heavy metals detection by stripping electrochemistry was done. The water samples taken directly from the ground water were acidified with 1 mL of HNO 3 acic suprapure was not digested, while the soils samples which have already dried in the oven at 105 o C, ware grinded and sieved through 150 μm, werte digested with HNO 3 acic suprapure in the digestion bomb at 150 o C for 3-4 hours. The mussels samples which have already freezed in the freezer were peeled, dried with N 2 liquid, grinded and dried again in the freeze drier at the pressure of ≅ 10 -2 mBar, and then were grinded again, weighted, digested with HNO 3 acic and HClO 4 suprapure in the digestion bomb at 150 o C for 3 hours. Food samples were homogenized by electric mixer, dried with freeze dried, homogenized again by using ZrO 2 ball mill, weighted, digested by HPA (high Pressure Asher). The heavy metals in the food samples solution of digestion product were detected by using Polarographic Analyzer EGandG of SWV and DPASV methods, while in the water, soils and the mussels solution were detected by using PDV 2000 and Polarograf E-505, DPASV method. The method validity were tested with SRM materials such as soil-5, soil-7, water W-4, and coppepoda. The heavy metals detection results in the water, soils, mussels, and food by electrochemical method were reported in this paper. (author)

Cs2AgBiBr6 single-crystal X-ray detectors with a low detection limit

Science.gov (United States)

Pan, Weicheng; Wu, Haodi; Luo, Jiajun; Deng, Zhenzhou; Ge, Cong; Chen, Chao; Jiang, Xiaowei; Yin, Wan-Jian; Niu, Guangda; Zhu, Lujun; Yin, Lixiao; Zhou, Ying; Xie, Qingguo; Ke, Xiaoxing; Sui, Manling; Tang, Jiang

2017-11-01

Sensitive X-ray detection is crucial for medical diagnosis, industrial inspection and scientific research. The recently described hybrid lead halide perovskites have demonstrated low-cost fabrication and outstanding performance for direct X-ray detection, but they all contain toxic Pb in a soluble form. Here, we report sensitive X-ray detectors using solution-processed double perovskite Cs2AgBiBr6 single crystals. Through thermal annealing and surface treatment, we largely eliminate Ag+/Bi3+ disordering and improve the crystal resistivity, resulting in a detector with a minimum detectable dose rate as low as 59.7 nGyair s-1, comparable to the latest record of 0.036 μGyair s-1 using CH3NH3PbBr3 single crystals. Suppressed ion migration in Cs2AgBiBr6 permits relatively large external bias, guaranteeing efficient charge collection without a substantial increase in noise current and thus enabling the low detection limit.

Microcontact Imprinted Plasmonic Nanosensors: Powerful Tools in the Detection of Salmonella paratyphi

Directory of Open Access Journals (Sweden)

Işık Perçin

2017-06-01

Full Text Available Identification of pathogenic microorganisms by traditional methods is slow and cumbersome. Therefore, the focus today is on developing new and quicker analytical methods. In this study, a Surface Plasmon Resonance (SPR sensor with a microcontact imprinted sensor chip was developed for detecting Salmonella paratyphi. For this purpose, the stamps of the target microorganism were prepared and then, microcontact S. paratyphi-imprinted SPR chips were prepared with the functional monomer N-methacryloyl-L-histidine methyl ester (MAH. Characterization studies of the SPR chips were carried out with ellipsometry and scanning electron microscopy (SEM. The real-time Salmonella paratyphi detection was performed within the range of 2.5 × 106–15 × 106 CFU/mL. Selectivity of the prepared sensors was examined by using competing bacterial strains such as Escherichia coli, Staphylococcus aureus and Bacillus subtilis. The imprinting efficiency of the prepared sensor system was determined by evaluating the responses of the SPR chips prepared with both molecularly imprinted polymers (MIPs and non-imprinted polymers (NIPs. Real sample experiments were performed with apple juice. The recognition of Salmonella paratyphi was achieved using these SPR sensor with a detection limit of 1.4 × 106 CFU/mL. In conclusion, SPR sensor has the potential to serve as an excellent candidate for monitoring Salmonella paratyphi in food supplies or contaminated water and clearly makes it possible to develop rapid and appropriate control strategies.

Development of detection techniques for a single-particle of fissile material(II)

Energy Technology Data Exchange (ETDEWEB)

Sohn, S. C.; Kim, W. H.; Park, Y. J.; Song, B. C.; Jeon, Y. S.; Jee, K. Y.; Pyo, H. Y.; Kwack, E. H

2001-06-01

The Analytical methods and detection limit of signatures, and the particle discrimination techniques of unknown particles by microscope were investigated in this technical report. In connection with pre-treatment of swipe samples, sampling and treatment of particles, etching method, fission track observation and the preparation of sample for the neutron activation analysis were also described in this thchnical report.

Development of detection techniques for a single-particle of fissile material(II)

International Nuclear Information System (INIS)

Sohn, S. C.; Kim, W. H.; Park, Y. J.; Song, B. C.; Jeon, Y. S.; Jee, K. Y.; Pyo, H. Y.; Kwack, E. H.

2001-06-01

The Analytical methods and detection limit of signatures, and the particle discrimination techniques of unknown particles by microscope were investigated in this technical report. In connection with pre-treatment of swipe samples, sampling and treatment of particles, etching method, fission track observation and the preparation of sample for the neutron activation analysis were also described in this thchnical report

Investigation of detection limits for diffuse optical tomography systems: II. Analysis of slab and cup geometry for breast imaging.

Science.gov (United States)

Ziegler, Ronny; Brendel, Bernhard; Rinneberg, Herbert; Nielsen, Tim

2009-01-21

Using a statistical (chi-square) test on simulated data and a realistic noise model derived from the system's hardware we study the performance of diffuse optical tomography systems for fluorescence imaging. We compare the predicted smallest size of detectable lesions at various positions in slab and cup geometry and model how detection sensitivity depends on breast compression and lesion fluorescence contrast. Our investigation shows that lesion detection is limited by relative noise in slab geometry and by absolute noise in cup geometry.

Detection Limits of DLS and UV-Vis Spectroscopy in Characterization of Polydisperse Nanoparticles Colloids

Directory of Open Access Journals (Sweden)

Emilia Tomaszewska

2013-01-01

Full Text Available Dynamic light scattering is a method that depends on the interaction of light with particles. This method can be used for measurements of narrow particle size distributions especially in the range of 2–500 nm. Sample polydispersity can distort the results, and we could not see the real populations of particles because big particles presented in the sample can screen smaller ones. Although the theory and mathematical basics of DLS technique are already well known, little has been done to determine its limits experimentally. The size and size distribution of artificially prepared polydisperse silver nanoparticles (NPs colloids were studied using dynamic light scattering (DLS and ultraviolet-visible (UV-Vis spectroscopy. Polydisperse colloids were prepared based on the mixture of chemically synthesized monodisperse colloids well characterized by atomic force microscopy (AFM, transmission electron microscopy (TEM, DLS, and UV-Vis spectroscopy. Analysis of the DLS results obtained for polydisperse colloids reveals that several percent of the volume content of bigger NPs could screen completely the presence of smaller ones. The presented results could be extremely important from nanoparticles metrology point of view and should help to understand experimental data especially for the one who works with DLS and/or UV-Vis only.

Low-Cost 3D Printers Enable High-Quality and Automated Sample Preparation and Molecular Detection.

Directory of Open Access Journals (Sweden)

Kamfai Chan

Full Text Available Most molecular diagnostic assays require upfront sample preparation steps to isolate the target's nucleic acids, followed by its amplification and detection using various nucleic acid amplification techniques. Because molecular diagnostic methods are generally rather difficult to perform manually without highly trained users, automated and integrated systems are highly desirable but too costly for use at point-of-care or low-resource settings. Here, we showcase the development of a low-cost and rapid nucleic acid isolation and amplification platform by modifying entry-level 3D printers that cost between $400 and $750. Our modifications consisted of replacing the extruder with a tip-comb attachment that houses magnets to conduct magnetic particle-based nucleic acid extraction. We then programmed the 3D printer to conduct motions that can perform high-quality extraction protocols. Up to 12 samples can be processed simultaneously in under 13 minutes and the efficiency of nucleic acid isolation matches well against gold-standard spin-column-based extraction technology. Additionally, we used the 3D printer's heated bed to supply heat to perform water bath-based polymerase chain reactions (PCRs. Using another attachment to hold PCR tubes, the 3D printer was programmed to automate the process of shuttling PCR tubes between water baths. By eliminating the temperature ramping needed in most commercial thermal cyclers, the run time of a 35-cycle PCR protocol was shortened by 33%. This article demonstrates that for applications in resource-limited settings, expensive nucleic acid extraction devices and thermal cyclers that are used in many central laboratories can be potentially replaced by a device modified from inexpensive entry-level 3D printers.

Low-Cost 3D Printers Enable High-Quality and Automated Sample Preparation and Molecular Detection

Science.gov (United States)

Chan, Kamfai; Coen, Mauricio; Hardick, Justin; Gaydos, Charlotte A.; Wong, Kah-Yat; Smith, Clayton; Wilson, Scott A.; Vayugundla, Siva Praneeth; Wong, Season

2016-01-01

Most molecular diagnostic assays require upfront sample preparation steps to isolate the target’s nucleic acids, followed by its amplification and detection using various nucleic acid amplification techniques. Because molecular diagnostic methods are generally rather difficult to perform manually without highly trained users, automated and integrated systems are highly desirable but too costly for use at point-of-care or low-resource settings. Here, we showcase the development of a low-cost and rapid nucleic acid isolation and amplification platform by modifying entry-level 3D printers that cost between $400 and $750. Our modifications consisted of replacing the extruder with a tip-comb attachment that houses magnets to conduct magnetic particle-based nucleic acid extraction. We then programmed the 3D printer to conduct motions that can perform high-quality extraction protocols. Up to 12 samples can be processed simultaneously in under 13 minutes and the efficiency of nucleic acid isolation matches well against gold-standard spin-column-based extraction technology. Additionally, we used the 3D printer’s heated bed to supply heat to perform water bath-based polymerase chain reactions (PCRs). Using another attachment to hold PCR tubes, the 3D printer was programmed to automate the process of shuttling PCR tubes between water baths. By eliminating the temperature ramping needed in most commercial thermal cyclers, the run time of a 35-cycle PCR protocol was shortened by 33%. This article demonstrates that for applications in resource-limited settings, expensive nucleic acid extraction devices and thermal cyclers that are used in many central laboratories can be potentially replaced by a device modified from inexpensive entry-level 3D printers. PMID:27362424

Limit of detection of a fiber optics gyroscope using a super luminescent radiation source

International Nuclear Information System (INIS)

Sandoval R, G.E.; Nikolaev, V.A.

2003-01-01

The main objective of this work is to establish the dependence of characteristics of the fiber optics gyroscope (FOG) with respect to the parameters of the super luminescent emission source based on doped optical fiber with rare earth elements (Super luminescent Fiber Source, SFS), argument the pumping rate election of the SFS to obtain characteristics limits of the FOG sensibility. By using this type of emission source in the FOG is recommend to use the rate when the direction of the pumping signal coincide with the super luminescent signal. The most results are the proposition and argumentation of the SFS election as emission source to be use in the FOG of the phase type. Such a decision allow to increase the characteristics of the FOG sensibility in comparison with the use of luminescent source of semiconductors emission which are extensively used in the present time. The use of emission source of the SFS type allow to come closer to the threshold of the obtained sensibility limit (detection limit) which is determined with the shot noise. (Author)

Limit of detection of a fiber optics gyroscope using a super luminescent radiation source

CERN Document Server

Sandoval, G E

2003-01-01

The main objective of this work is to establish the dependence of characteristics of the fiber optics gyroscope (FOG) with respect to the parameters of the super luminescent emission source based on doped optical fiber with rare earth elements (Super luminescent Fiber Source, SFS), argument the pumping rate election of the SFS to obtain characteristics limits of the FOG sensibility. By using this type of emission source in the FOG is recommend to use the rate when the direction of the pumping signal coincide with the super luminescent signal. The most results are the proposition and argumentation of the SFS election as emission source to be use in the FOG of the phase type. Such a decision allow to increase the characteristics of the FOG sensibility in comparison with the use of luminescent source of semiconductors emission which are extensively used in the present time. The use of emission source of the SFS type allow to come closer to the threshold of the obtained sensibility limit (detection limit) which i...

Grasp Preparation Improves Change Detection for Congruent Objects

Science.gov (United States)

Symes, Ed; Tucker, Mike; Ellis, Rob; Vainio, Lari; Ottoboni, Giovanni

2008-01-01

A series of experiments provided converging support for the hypothesis that action preparation biases selective attention to action-congruent object features. When visual transients are masked in so-called "change-blindness scenes," viewers are blind to substantial changes between 2 otherwise identical pictures that flick back and forth. The…

Radioactivity analyses and detection limit problems of environmental surveillance at a gas-cooled reactor

International Nuclear Information System (INIS)

Johnson, J.E.; Johnson, J.A.

1988-01-01

The lower limit of detection (LLD) values required by the USNRC for nuclear power facilities are often difficult to attain even using state of the art detection systems, e.g. the required LLD for I-131 in air is 70 fCi/m 3 . For a gas-cooled reactor where I-131 has never been observed in effluents, occasional false positive values occur due to: Counting statistics using high resolution Ge(Li) detectors, contamination from nuclear medicine releases and spectrum analysis systematic error. Statistically negative concentration values are often observed. These measurements must be included in the estimation of true mean values. For this and other reasons, the frequency distributions of this and other reasons, the frequency distributions of measured values appear to be log-normal. Difficulties in stating the true means and standard deviations are discussed for these situations

Development of an enzyme-linked immunosorbent assay for the detection of dicamba.

Science.gov (United States)

Clegg, B S; Stephenson, G R; Hall, J C

2001-05-01

A competitive indirect enzyme-linked immunosorbent assay (CI-ELISA) was developed to quantitate the herbicide dicamba (3,6-dichloro-2-methoxybenzoic acid) in water. The CI-ELISA has a detection limit of 2.3 microg L(-1) and a linear working range of 10--10000 microg L(-1) with an IC(50) value of 195 microg L(-1). The dicamba polyclonal antisera did not cross-react with a number of other herbicides tested but did cross-react with a dicamba metabolite, 5-hydroxydicamba, and structurally related chlorobenzoic acids. The assay was used to estimate quantitatively dicamba concentrations in water samples. Water samples were analyzed directly, and no sample preparation was required. To improve detection limits, a C(18) (reversed phase) column concentration step was devised prior to analysis, and the detection limits were increased by at least by 10-fold. After the sample preconcentration, the detection limit, IC(50), and linear working range were 0.23, 19.5, and 5-200 microg L(-1), respectively. The CI-ELISA estimations in water correlated well with those from gas chromatography-mass spectrometry (GC-MS) analysis (r(2) = 0.9991). This assay contributes to reducing laboratory costs associated with the conventional GC-MS residue analysis techniques for the quantitation of dicamba in water.

Limited copy number-high resolution melting (LCN-HRM) enables the detection and identification by sequencing of low level mutations in cancer biopsies.

Science.gov (United States)

Do, Hongdo; Dobrovic, Alexander

2009-10-08

Mutation detection in clinical tumour samples is challenging when the proportion of tumour cells, and thus mutant alleles, is low. The limited sensitivity of conventional sequencing necessitates the adoption of more sensitive approaches. High resolution melting (HRM) is more sensitive than sequencing but identification of the mutation is desirable, particularly when it is important to discriminate false positives due to PCR errors or template degradation from true mutations.We thus developed limited copy number - high resolution melting (LCN-HRM) which applies limiting dilution to HRM. Multiple replicate reactions with a limited number of target sequences per reaction allow low level mutations to be detected. The dilutions used (based on Ct values) are chosen such that mutations, if present, can be detected by the direct sequencing of amplicons with aberrant melting patterns. Using cell lines heterozygous for mutations, we found that the mutations were not readily detected when they comprised 10% of total alleles (20% tumour cells) by sequencing, whereas they were readily detectable at 5% total alleles by standard HRM. LCN-HRM allowed these mutations to be identified by direct sequencing of those positive reactions.LCN-HRM was then used to review formalin-fixed paraffin-embedded (FFPE) clinical samples showing discordant findings between sequencing and HRM for KRAS exon 2 and EGFR exons 19 and 21. Both true mutations present at low levels and sequence changes due to artefacts were detected by LCN-HRM. The use of high fidelity polymerases showed that the majority of the artefacts were derived from the damaged template rather than replication errors during amplification. LCN-HRM bridges the sensitivity gap between HRM and sequencing and is effective in distinguishing between artefacts and true mutations.

Multicomponent analysis of fat- and water-soluble vitamins and auxiliary substances in multivitamin preparations by qNMR.

Science.gov (United States)

Eiff, Julia; Monakhova, Yulia B; Diehl, Bernd W K

2015-04-01

A nuclear magnetic resonance (NMR) spectroscopic method was tested to control 12 vitamins and accompanying substances in multivitamin preparations. The limits of detection (LODs) and limits of quantification (LOQs) varied in the 9.0-77.0 mg/kg and in the 34.5-93.5 mg/kg range, respectively. The coefficients of variation (CVs) ranged between 0.9% and 12%. The (1)H NMR spectra showed linearity for the 140-260 mg sample weight (R(2) > 0.918). The NMR spectra of multivitamin preparations showed the presence of different degradation products of ascorbic acid. The NMR method was applied to 13 different multivitamin preparations including tablets, capsules, and effervescent tablets with average recovery rates between 85% and 132%. A number of accompanying substances (citric acid, mannitol, saccharin, cyclamate, sum of steviol glycosides, and butylhydroxytoluene) were additionally identified and quantified. NMR was found to be suitable for the simultaneous qualitative measurement of water- and fat-soluble vitamins and accompanying substances and shows some promise for quantitative determination of at least 5 vitamins (B1, B3, B5, B6, and E) in multivitamin preparations.

Determining the 95% limit of detection for waterborne pathogen analyses from primary concentration to qPCR

Science.gov (United States)

Stokdyk, Joel P.; Firnstahl, Aaron; Spencer, Susan K.; Burch, Tucker R; Borchardt, Mark A.

2016-01-01

The limit of detection (LOD) for qPCR-based analyses is not consistently defined or determined in studies on waterborne pathogens. Moreover, the LODs reported often reflect the qPCR assay alone rather than the entire sample process. Our objective was to develop an approach to determine the 95% LOD (lowest concentration at which 95% of positive samples are detected) for the entire process of waterborne pathogen detection. We began by spiking the lowest concentration that was consistently positive at the qPCR step (based on its standard curve) into each procedural step working backwards (i.e., extraction, secondary concentration, primary concentration), which established a concentration that was detectable following losses of the pathogen from processing. Using the fraction of positive replicates (n = 10) at this concentration, we selected and analyzed a second, and then third, concentration. If the fraction of positive replicates equaled 1 or 0 for two concentrations, we selected another. We calculated the LOD using probit analysis. To demonstrate our approach we determined the 95% LOD for Salmonella enterica serovar Typhimurium, adenovirus 41, and vaccine-derived poliovirus Sabin 3, which were 11, 12, and 6 genomic copies (gc) per reaction (rxn), respectively (equivalent to 1.3, 1.5, and 4.0 gc L−1 assuming the 1500 L tap-water sample volume prescribed in EPA Method 1615). This approach limited the number of analyses required and was amenable to testing multiple genetic targets simultaneously (i.e., spiking a single sample with multiple microorganisms). An LOD determined this way can facilitate study design, guide the number of required technical replicates, aid method evaluation, and inform data interpretation.

Effects of Kapton Sample Cell Windows on the Detection Limit of Smectite: Implications for CheMin on the Mars Science Laboratory Mission

Science.gov (United States)

Achilles, C. N.; Ming, Douglas W.; Morris, R. V.; Blake, D. F.

2012-01-01

The CheMin instrument on the Mars Science Laboratory (MSL) rover Curiosity is an X-ray diffraction (XRD) and X-ray fluorescence (XRF) instrument capable of providing the mineralogical and chemical compositions of rocks and soils on the surface of Mars. CheMin uses a microfocus X-ray tube with a Co target, transmission geometry, and an energy-discriminating X-ray sensitive CCD to produce simultaneous 2-D XRD patterns and energy-dispersive X-ray histograms from powdered samples. CheMin has two different window materials used for sample cells -- Mylar and Kapton. Instrument details are provided elsewhere. Fe/Mg-smectite (e.g., nontronite) has been identified in Gale Crater, the MSL future landing site, by CRISM spectra. While large quantities of phyllosilicate minerals will be easily detected by CheMin, it is important to establish detection limits of such phases to understand capabilities and limitations of the instrument. A previous study indicated that the (001) peak of smectite at 15 Ang was detectable in a mixture of 1 wt.% smectite with olivine when Mylar is the window material for the sample cell. Complications arise when Kapton is the window material because Kapton itself also has a diffraction peak near 15 Ang (6.8 deg 2 Theta). This study presents results of mineral mixtures of smectite and olivine to determine smectite detection limits for Kapton sample cells. Because the intensity and position of the smectite (001) peak depends on the hydration state, we also analyzed mixtures with "hydrated" and "dehydrated"h smectite to examine the effects of hydration state on detection limits.

Homogeneous immunosubtraction integrated with sample preparation is enabled by a microfluidic format

Science.gov (United States)

Apori, Akwasi A.; Herr, Amy E.

2011-01-01

Immunosubtraction is a powerful and resource-intensive laboratory medicine assay that reports both protein mobility and binding specificity. To expedite and automate this electrophoretic assay, we report on advances to the electrophoretic immunosubtraction assay by introducing a homogeneous, not heterogeneous, format with integrated sample preparation. To accomplish homogeneous immunosubtraction, a step-decrease in separation matrix pore-size at the head of a polyacrylamide gel electrophoresis (PAGE) separation channel enables ‘subtraction’ of target analyte when capture antibody is present (as the large immune-complex is excluded from PAGE), but no subtraction when capture antibody is absent. Inclusion of sample preparation functionality via small pore size polyacrylamide membranes is also key to automated operation (i.e., sample enrichment, fluorescence sample labeling, and mixing of sample with free capture antibody). Homogenous sample preparation and assay operation allows on-the-fly, integrated subtraction of one to multiple protein targets and reuse of each device. Optimization of the assay is detailed which allowed for ~95% subtraction of target with 20% non-specific extraction of large species at the optimal antibody-antigen ratio, providing conditions needed for selective target identification. We demonstrate the assay on putative markers of injury and inflammation in cerebrospinal fluid (CSF), an emerging area of diagnostics research, by rapidly reporting protein mobility and binding specificity within the sample matrix. We simultaneously detect S100B and C-reactive protein, suspected biomarkers for traumatic brain injury (TBI), in ~2 min. Lastly, we demonstrate S100B detection (65 nM) in raw human CSF with a lower limit of detection of ~3.25 nM, within the clinically relevant concentration range for detecting TBI in CSF. Beyond the novel CSF assay introduced here, a fully automated immunosubtraction assay would impact a spectrum of routine but labor

Improved detection limit for {sup 59}Ni using the technique of accelerator mass spectrometry

Energy Technology Data Exchange (ETDEWEB)

Persson, Per; Erlandsson, Bengt; Hellborg, Ragnar; Kiisk, Madis; Larsson, Ragnar; Skog, Goeran; Stenstroem, Kristina [Lund Univ. (Sweden). Dept. of Nuclear Physics

2002-11-01

59 Ni is produced by neutron activation in the stainless steel close to the core of a nuclear reactor. To be able to classify the different parts of the reactor with respect to their content of long-lived radionuclides before final storage it is important to measure the 59 Ni level. Accelerator mass spectrometry is an ultra-sensitive method for counting atoms, suitable for 59 Ni measurements. Improvements in the reduction of the background and in the chemical reduction of cobalt, the interfering isobar, have been made. This chemical purification is essential when using small tandem accelerators, <3 MV, combined with the detection of characteristic projectile X-rays. These improvements have lowered the detection limit for 59 Ni by a factor of twenty compared with the first value reported for the Lund AMS facility. Material from the Swedish nuclear industry has been analysed and examples of the results are presented.

One-pot preparation of conducting composite containing abundant amino groups on electrode surface for electrochemical detection of von willebrand factor

Science.gov (United States)

Wang, Wen; Ma, Chao; Li, Yi; Liu, Baihui; Tan, Liang

2018-03-01

A one-pot protocol based on cyclic voltammetric scan was employed to prepare new conducting composite that was abundant in amino groups. The scanning electron microscope, atomic force microscope, X-ray photoelectron spectroscopy and infrared spectrum characterization demonstrate that poly(azure A), gold nanoparticles, chitosan and cysteine were immobilized simultaneously on glassy carbon electrode surface. Von Willebrand factor (vWF) antibody (Ab) was subsequently assembled by using glutaraldehyde to construct the Ab/composite-modified electrode. The capture of vWF could inhibit the charge transfer between the ferri-/ferrocyanide probe and the electrode and exert the negative effect on the electrochemical response of the dye polymer in the conducting composite due to the strong steric hindrance effect. The DPV peak current change before and after the immunoreaction was found to be proportional to the logarithm of the vWF concentration from 0.001 to 100 μg mL-1 with a detection limit of 0.4 ng mL-1. The proposed label-free electrochemical method was employed in the investigation on the release of vWF by oxidation-injured vascular endothelial cells. The experimental results exhibit that the vWF content in growth medium was increased when the oxidation injury of the cells was intensified in the presence of H2O2.

PdNi- and Pd-coated electrodes prepared by electrodeposition from ionic liquid for nonenzymatic electrochemical determination of ethanol and glucose in alkaline media.

Science.gov (United States)

Huang, Hsin-Yi; Chen, Po-Yu

2010-12-15

Nonenzymatic electrochemical determination of ethanol and glucose was respectively achieved using PdNi- and Pd-coated electrodes prepared by electrodeposition from the novel metal-free ionic liquid (IL); N-butyl-N-methylpyrrolidinium dicyanamide (BMP-DCA). BMP-DCA provided an excellent environment and wide cathodic limit for electrodeposition of metals and alloys because many metal chlorides could dissolve in this IL where the reduction potentials of Pd(II) and Ni(II) indeed overlapped, leading to the convenience of potentiostatic codeposition. In aqueous solutions, the reduction potentials of Pd(II) and Ni(II) are considerably separated. The bimetallic PdNi coatings with atomic ratios of ∼ 80/20 showed the highest current for ethanol oxidation reaction (EOR). Ethanol was detected by either cyclic voltammetry (CV) or hydrodynamic amperometry (HA). Using CV, the dependence of EOR peak current on concentration was linear from 4.92 to 962 μM with a detection limit of 2.26 μM (σ=3), and a linearity was observed from 4.92 to 988 μM using HA (detection limit 0.83 μM (σ=3)). The Pd-coated electrodes prepared by electrodeposition from BMP-DCA showed electrocatalytic activity to glucose oxidation and CV, HA, and square-wave voltammetry (SWV) were employed to determine glucose. SWV showed the best sensitivity and linearity was observed from 2.86 μM to 107 μM, and from 2.99 mM to 10.88 mM with detection limits of 0.78 μM and 25.9 μM (σ=3), respectively. For glucose detection, the interference produced from ascorbic acid, uric acid, and acetaminophen was significantly suppressed, compared with a regular Pt disk electrode. Copyright © 2010 Elsevier B.V. All rights reserved.

Guidance document for preparing water sampling and analysis plans for UMTRA Project sites. Revision 1

International Nuclear Information System (INIS)

1995-09-01

A water sampling and analysis plan (WSAP) is prepared for each Uranium Mill Tailings Remedial Action (UMTRA) Project site to provide the rationale for routine ground water sampling at disposal sites and former processing sites. The WSAP identifies and justifies the sampling locations, analytical parameters, detection limits, and sampling frequency for the routine ground water monitoring stations at each site. This guidance document has been prepared by the Technical Assistance Contractor (TAC) for the US Department of Energy (DOE). Its purpose is to provide a consistent technical approach for sampling and monitoring activities performed under the WSAP and to provide a consistent format for the WSAP documents. It is designed for use by the TAC in preparing WSAPs and by the DOE, US Nuclear Regulatory Commission, state and tribal agencies, other regulatory agencies, and the public in evaluating the content of WSAPS

Highly porous nanocomposites based on TiO2-noble metal particles for sensitive detection of water pollutants by SERS

International Nuclear Information System (INIS)

Baia, M; Melinte, G; Iancu, V; Baia, L; Barbu-Tudoran, L; Diamandescu, L; Cosoveanu, V; Danciu, V

2011-01-01

Highly porous nanocomposites based on TiO2 aerogel and silver colloidal particles were prepared by different methods in order to study their capacity to detect pollutant species adsorbed on metallic nanoparticles surface from aqueous solution. The efficiency of the obtained composites to detect contaminants from water by means of SERS was evaluated using acrylamide and crystal violet as test molecules. It was found that the detection limits depend both on pollutant and composite type, and were determined to be in the range of 10 -1 -10 -4 M for acrylamide and around 10 -5 M for the dye molecule. These results prove the potential of the prepared porous composites for further use in the development of new SERS-based sensors devices.

Highly porous nanocomposites based on TiO2-noble metal particles for sensitive detection of water pollutants by SERS

Energy Technology Data Exchange (ETDEWEB)

Baia, M; Melinte, G; Iancu, V; Baia, L [Faculty of Physics, Babes-Bolyai University, 400084, Cluj-Napoca (Romania); Barbu-Tudoran, L [Faculty of Biology and Geology, Babes-Bolyai University, 400015, Cluj-Napoca (Romania); Diamandescu, L [National Institute of Materials Physics, PO Box MG-7, 77125, Bucharest-Magurele (Romania); Cosoveanu, V; Danciu, V, E-mail: lucian.baia@phys.ubbcluj.ro [Faculty of Chemistry and Chemical Engineering, Babes-Bolyai University, 400028, Cluj-Napoca (Romania)

2011-07-06

Highly porous nanocomposites based on TiO2 aerogel and silver colloidal particles were prepared by different methods in order to study their capacity to detect pollutant species adsorbed on metallic nanoparticles surface from aqueous solution. The efficiency of the obtained composites to detect contaminants from water by means of SERS was evaluated using acrylamide and crystal violet as test molecules. It was found that the detection limits depend both on pollutant and composite type, and were determined to be in the range of 10{sup -1}-10{sup -4} M for acrylamide and around 10{sup -5} M for the dye molecule. These results prove the potential of the prepared porous composites for further use in the development of new SERS-based sensors devices.

Preparation of a molecularly imprinted sensor based on quartz crystal microbalance for specific recognition of sialic acid in human urine.

Science.gov (United States)

Qiu, Xiuzhen; Xu, Xian-Yan; Chen, Xuncai; Wu, Yiyong; Guo, Huishi

2018-05-08

A novel molecularly imprinted quartz crystal microbalance (QCM) sensor was successfully prepared for selective determination of sialic acid (SA) in human urine samples. To obtain the QCM sensor, we first modified the gold surface of the QCM chip by self-assembling of allylmercaptane to introduce polymerizable double bonds on the chip surface. Then, SA molecularly imprinted polymer (MIP) nanofilm was attached to the modified QCM chip surface. For comparison, we have also characterized the nonmodified and improved surfaces of the QCM sensor by using atomic force microscopy (AFM) and Fourier transform infrared (FTIR) spectroscopy. We then tested the selectivity and detection limit of the imprinted QCM sensor via a series of adsorption experiments. The results show a linear response in the range of 0.025-0.50 μmol L -1 for sialic acid. Moreover, the limit of detection (LOD) of the prepared imprinted QCM sensor was found to be 1.0 nmol L -1 for sialic acid, and high recovery values range from 87.6 to 108.5% with RSD sensor was developed and used to detect sialic acid in human urine samples. Graphical abstract Specific recognition of sialic acid by the MIP-QCM sensor system.

Thermal background noise limitations

Science.gov (United States)

Gulkis, S.

1982-01-01

Modern detection systems are increasingly limited in sensitivity by the background thermal photons which enter the receiving system. Expressions for the fluctuations of detected thermal radiation are derived. Incoherent and heterodyne detection processes are considered. References to the subject of photon detection statistics are given.

Detection of Cucurbit chlorotic yellows virus from Bemisia tabaci captured on sticky traps using reverse transcription loop-mediated isothermal amplification (RT-LAMP) and simple template preparation.

Science.gov (United States)

Okuda, Mitsuru; Okuda, Shiori; Iwai, Hisashi

2015-09-01

Cucurbit chlorotic yellows virus (CCYV) of the genus Crinivirus within the family Closteroviridae is an emerging infectious agent of cucurbits leading to severe disease and significant economic losses. Effective detection and identification methods for this virus are urgently required. In this study, a reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay was developed to detect CCYV from its vector Bemisia tabaci. LAMP primer sets to detect CCYV were evaluated for their sensitivity and specificity, and a primer set designed from the HSP70h gene with corresponding loop primers were selected. The RT-LAMP assay was applied to detect CCYV from viruliferous B. tabaci trapped on sticky traps. A simple extraction procedure using RNAsecure™ was developed for template preparation. CCYV was detected in all of the B. tabaci 0, 1, 7 and 14 days after they were trapped. Although the rise of turbidity was delayed in reactions using RNA from B. tabaci trapped for 7 and 14 days compared with those from 0 and 1 day, the DNA amplification was sufficient to detect CCYV in all of the samples. These findings therefore present a simple template preparation method and an effective RT-LAMP assay, which can be easily and rapidly performed to monitor CCYV-viruliferous B. tabaci in the field. Copyright © 2015 Elsevier B.V. All rights reserved.

Complexation as an approach to entrap cationic drugs into cationic nanoparticles administered intranasally for Alzheimer's disease management: preparation and detection in rat brain.

Science.gov (United States)

Hanafy, Amira S; Farid, Ragwa M; ElGamal, Safaa S

2015-01-01

Complexation was investigated as an approach to enhance the entrapment of the cationic neurotherapeutic drug, galantamine hydrobromide (GH) into cationic chitosan nanoparticles (CS-NPs) for Alzheimer's disease management intranasally. Biodegradable CS-NPs were selected due to their low production cost and simple preparation. The effects of complexation on CS-NPs physicochemical properties and uptake in rat brain were examined. Placebo CS-NPs were prepared by ionic gelation, and the parameters affecting their physicochemical properties were screened. The complex formed between GH and chitosan was detected by the FT-IR study. GH/chitosan complex nanoparticles (GH-CX-NPs) were prepared by ionic gelation, and characterized in terms of particle size, zeta potential, entrapment efficiency, in vitro release and stability for 4 and 25 °C for 3 months. Both placebo CS-NPs and GH-CX-NPs were visualized by transmission electron microscopy. Rhodamine-labeled GH-CX-NPs were prepared, administered to male Wistar rats intranasally, and their delivery to different brain regions was detected 1 h after administration using fluorescence microscopy and software-aided image processing. Optimized placebo CS-NPs and GH-CX-NPs had a diameter 182 and 190 nm, and a zeta potential of +40.4 and +31.6 mV, respectively. GH encapsulation efficiency and loading capacity were 23.34 and 9.86%, respectively. GH/chitosan complexation prolonged GH release (58.07% ± 6.67 after 72 h), improved formulation stability at 4 °C in terms of drug leakage and particle size, and showed insignificant effects on the physicochemical properties of the optimized placebo CS-NPs (p > 0.05). Rhodamine-labeled GH-CX-NPs were detected in the olfactory bulb, hippocampus, orbitofrontal and parietal cortices. Complexation is a promising approach to enhance the entrapment of cationic GH into the CS-NPs. It has insignificant effect on the physicochemical properties of CS-NPs. GH-CX-NPs were successfully

Use of x-ray fluorescence for in-situ detection of metals

Science.gov (United States)

Elam, W. T. E.; Whitlock, Robert R.; Gilfrich, John V.

1995-01-01

X-ray fluorescence (XRF) is a well-established, non-destructive method of determining elemental concentrations at ppm levels in complex samples. It can operate in atmosphere with no sample preparation, and provides accuracies of 1% or better under optimum conditions. This report addresses two sets of issues concerning the use of x-ray fluorescence as a sensor technology for the cone penetrometer, for shipboard waste disposal, or for other in-situ, real- time environmental applications. The first issue concerns the applicability of XRF to these applications, and includes investigation of detection limits and matrix effects. We have evaluated the detection limits and quantitative accuracy of a sensor mock-up for metals in soils under conditions expected in the field. In addition, several novel ways of improving the lower limits of detection to reach the drinking water regulatory limits have been explored. The second issue is the engineering involved with constructing a spectrometer within the 1.75 inch diameter of the penetrometer pipe, which is the most rigorous physical constraint. Only small improvements over current state-of-the-art are required. Additional advantages of XRF are that no radioactive sources or hazardous materials are used in the sensor design, and no reagents or any possible sources of ignition are involved.

Detection limits in the chromatographic element trace analysis - quantitative TLC, HPLC and GC with the example of beryllium acetylacetonate

International Nuclear Information System (INIS)

Schwedt, G.

1981-01-01

Chromatographic analyses of beryllium acetylacetonate are carried out in synthetic solutions within the nano- and picogram range of beryllium. For thin-layer chromatography (TLC) normal and silanized silica gel is used, for high-performance liquid chromatography (HPLC) silica gel of 7 μm particles, for gas chromatography (GC) silicone SE-30 as stationary phase. Visual evaluation and remission measurements in TLC, UV-254 nm absorption measurements in HPLC and measurements with a FID in GC are employed for the determination of the calibration curves. A calibration curve through the origin and a detection limit of 150 pg Be determinable form are received by HPLC only. For trace analyses by GC a new definition of a detection limit for the evaluation of substance peaks on a solvent tailing is suggested. (orig.) [de

Estimation of the limit of detection in semiconductor gas sensors through linearized calibration models.

Science.gov (United States)

Burgués, Javier; Jiménez-Soto, Juan Manuel; Marco, Santiago

2018-07-12

The limit of detection (LOD) is a key figure of merit in chemical sensing. However, the estimation of this figure of merit is hindered by the non-linear calibration curve characteristic of semiconductor gas sensor technologies such as, metal oxide (MOX), gasFETs or thermoelectric sensors. Additionally, chemical sensors suffer from cross-sensitivities and temporal stability problems. The application of the International Union of Pure and Applied Chemistry (IUPAC) recommendations for univariate LOD estimation in non-linear semiconductor gas sensors is not straightforward due to the strong statistical requirements of the IUPAC methodology (linearity, homoscedasticity, normality). Here, we propose a methodological approach to LOD estimation through linearized calibration models. As an example, the methodology is applied to the detection of low concentrations of carbon monoxide using MOX gas sensors in a scenario where the main source of error is the presence of uncontrolled levels of humidity. Copyright © 2018 Elsevier B.V. All rights reserved.

Sample preparation method for the combined extraction of ethyl glucuronide and drugs of abuse in hair.

Science.gov (United States)

Meier, Ulf; Briellmann, Thomas; Scheurer, Eva; Dussy, Franz

2018-04-01

Often in hair analysis, a small hair sample is available while the analysis of a multitude of structurally diverse substances with different concentration ranges is demanded. The analysis of the different substances often requires different sample preparation methods, increasing the amount of required hair sample. When segmental hair analysis is necessary, the amount of hair sample needed is further increased. Therefore, the required sample amount for a full analysis can quickly exceed what is available. To combat this problem, a method for the combined hair sample preparation using a single extraction procedure for analysis of ethyl glucuronide with liquid chromatography-multistage fragmentation mass spectrometry/multiple reaction monitoring (LC-MS 3 /MRM) and common drugs of abuse with LC-MRM was developed. The combined sample preparation is achieved by separating ethyl glucuronide from the drugs of abuse into separate extracts by fractionation in the solid-phase extraction step during sample clean-up. A full validation for all substances for the parameters selectivity, linearity, limit of detection, limit of quantification, accuracy, precision, matrix effects, and recovery was successfully completed. The following drugs of abuse were included in the method: Amphetamine; methamphetamine; 3,4-methylenedioxy-N-methylamphetamine (MDMA); 3,4-methylenedioxyamphetamine (MDA); 3,4-methylenedioxy-N-ethylamphetamine (MDE); morphine; 6-monoacetylmorphine; codeine; acetylcodeine; cocaine; benzoylecgonine; norcocaine; cocaethylene; methadone; 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) and methylphenidate. In conclusion, as only 1 sample preparation is needed with 1 aliquot of hair, the presented sample preparation allows an optimal analysis of both ethyl glucuronide and of the drugs of abuse, even when the sample amount is a limiting factor. Copyright © 2017 John Wiley & Sons, Ltd.

Label-free electrochemical aptasensor constructed by layer-by-layer technology for sensitive and selective detection of cancer cells

International Nuclear Information System (INIS)

Wang, Tianshu; Liu, Jiyang; Gu, Xiaoxiao; Li, Dan; Wang, Jin; Wang, Erkang

2015-01-01

Highlights: • Fc-PAH was modified on the surface of graphene to prepare hybid nanocomposite (Fc-PAH-G). • A cytosensor was constructed with Fc-PAH-G, PSS and aptamer AS1411 by LBL technology. • The sensing interface introduced more redox probe and enhanced current signal on electrode. • The sensor showed a detection range of 10–10 6 cells/mL with a detection limit of 10 cells/mL. - Abstract: Here, a cytosensor was constructed with ferrocene-appended poly(allylamine hydrochloride) (Fc-PAH) functionalized graphene (Fc-PAH-G), poly(sodium-p-styrenesulfonate) (PSS) and aptamer (AS1411) by layer-by-layer assembly technology. The hybrid nanocomposite Fc-PAH-G not only brings probes on the electrode and also promotes electron transfer between the probes and the substrate electrode. Meanwhile, LBL technology provides more effective probes to enhance amplified signal for improving the sensitivity of the detection. While AS1411 forming G-quardruplex structure and binding cancer cells, the current response of the sensing electrode decreased due to the insulating properties of cellular membrane. Differential pulse voltammetry (DPV) was performed to investigate the electrochemical detection of HeLa cells attributing to its sensitivity of the current signal change. The as-prepared aptasensor showed a high sensitivity and good stability, a widely detection range from 10 to 10 6 cells/mL with a detection limit as low as 10 cells/mL for the detection of cancer cells

Label-free electrochemical aptasensor constructed by layer-by-layer technology for sensitive and selective detection of cancer cells

Energy Technology Data Exchange (ETDEWEB)

Wang, Tianshu [College of Physics, Jilin University, Changchun, Jilin 130012 (China); State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022 (China); Liu, Jiyang; Gu, Xiaoxiao; Li, Dan [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022 (China); Wang, Jin, E-mail: jin.wang.1@stonybrook.edu [College of Physics, Jilin University, Changchun, Jilin 130012 (China); State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022 (China); Department of Chemistry, Physics and Applied Mathematics, State University of New York at Stony Brook, Stony Brook, NY 11794-3400 (United States); Wang, Erkang, E-mail: ekwang@ciac.jl.cn [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022 (China)

2015-07-02

Highlights: • Fc-PAH was modified on the surface of graphene to prepare hybid nanocomposite (Fc-PAH-G). • A cytosensor was constructed with Fc-PAH-G, PSS and aptamer AS1411 by LBL technology. • The sensing interface introduced more redox probe and enhanced current signal on electrode. • The sensor showed a detection range of 10–10{sup 6} cells/mL with a detection limit of 10 cells/mL. - Abstract: Here, a cytosensor was constructed with ferrocene-appended poly(allylamine hydrochloride) (Fc-PAH) functionalized graphene (Fc-PAH-G), poly(sodium-p-styrenesulfonate) (PSS) and aptamer (AS1411) by layer-by-layer assembly technology. The hybrid nanocomposite Fc-PAH-G not only brings probes on the electrode and also promotes electron transfer between the probes and the substrate electrode. Meanwhile, LBL technology provides more effective probes to enhance amplified signal for improving the sensitivity of the detection. While AS1411 forming G-quardruplex structure and binding cancer cells, the current response of the sensing electrode decreased due to the insulating properties of cellular membrane. Differential pulse voltammetry (DPV) was performed to investigate the electrochemical detection of HeLa cells attributing to its sensitivity of the current signal change. The as-prepared aptasensor showed a high sensitivity and good stability, a widely detection range from 10 to 10{sup 6} cells/mL with a detection limit as low as 10 cells/mL for the detection of cancer cells.

Study on the preparation of antibody coated tubes for radioimmunoassay kit production

International Nuclear Information System (INIS)

Nguyen Thi Thu; Le Van So; Vo Thi Cam Hoa; Duong Van Dong; Mai Phuoc Tho

2003-01-01

The polystyrene tubes are coated with T3/ T4 antibodies by γ-globulin, second antibody and specific antibodies. They are immobilized on the solid at a suitably dilution and incubation for 24 h, pH 9.6. The variation of the binding capacity values (obtained for 10 consecutive preparations) was less than 10%. NSB <3%, Binding 30-50%. Using dried tubes coated either with anti-T3 or anti-T4 antibody according to the developed coating approach for the determination of total T3 and total T4 in human serum. The recovery of T3 was found to be between 85.5% and 104% while the recovery of T4 ranged between 90.9% and 119%. The cross-reactivity for T4 in the T3 assay was 0.22%. Both assays were sensitive, the detection limit of the RIA for total T3 assay was 0.15 ng/ml while the detection limit of the RIA for total T4 assay was 5 ng/ml. (author)

Utility of minimal preparation ct colonography in detecting colorectal cancer in elderly and frail patients.

Science.gov (United States)

Meiklejohn, D J; Ridley, L J; Ngu, M C; Cowlishaw, J L; Duller, A; Ridley, W

2018-06-11

Colorectal cancers result in substantial morbidity and mortality to Australian society each year. The usual investigation for bowel malignancyis optical colonoscopy (OC), withcomputed tomographic colonography (CTC) used as an alternative investigation. The catharsis and colon insufflation associated with these investigations pose a higher risk in the elderly and frail. Risks include perforation, serum electrolyte disturbance, and anaesthesia/sedation risks.Minimal preparation computed tomographic colonography (MPCTC) eliminates these risks. This paper audits a 6-year period ofMPCTC in an Australian tertiary referral hospital. 145 patients underwent MPCTC during the study period. There were 7 true positives, 2 false positives and 2 false negatives. Analysis of this population indicates a sensitivity of 0.78 (95% CI 0.51 - 1.05), specificity of 0.99 (95% CI 0.97 - 1.01), positive predictive value (PPV) of 0.78 (95% CI 0.51 - 1.05) and negative predictive value (NPV) of 0.99 (95% CI 0.97 - 1.01). These findings are concordant with other published studies. The auditconfirmsthatminimal preparation CT colonography is a reasonable alternative to OC and CTC in detecting colorectal cancer in symptomatic elderly and frail patients, without the procedural risks inherent inmore invasive investigations. For most patients MPCTC ruled out significant colorectal carcinoma with a high negative predictive value. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Protein-templated gold nanoclusters based sensor for off-on detection of ciprofloxacin with a high selectivity.

Science.gov (United States)

Chen, Zhanguang; Qian, Sihua; Chen, Junhui; Cai, Jie; Wu, Shuyan; Cai, Ziping

2012-05-30

In this contribution, bovine serum albumin stabilized gold nanoclusters as novel fluorescent probes were successfully utilized for the detection of ciprofloxacin for the first time. Our prepared gold nanoclusters exhibited strong emission with peak maximum at 635 nm. Cu(2+) was employed to quench the strong fluorescence of the gold nanoclusters, whereas the addition of ciprofloxacin caused the fluorescence intensity restoration of the Cu(2+)-gold nanoclusters system. The increase in fluorescence intensity of Cu(2+)-gold nanoclusters system caused by ciprofloxacin allows the sensitive detection of ciprofloxacin in the range of 0.4 ng mL(-1) to 50 ng mL(-1). The detection limit for ciprofloxacin is 0.3 ng mL(-1) at a signal-to-noise ratio of 3. The present sensor for ciprofloxacin detection possesses a low detection limit and wide linear range. In addition, the real samples were analyzed with satisfactory results. Copyright © 2012 Elsevier B.V. All rights reserved.

A label-free photoelectrochemical biosensor for urokinase-type plasminogen activator detection based on a g-C3N4/CdS nanocomposite.

Science.gov (United States)

Liu, Xing-Pei; Chen, Jing-Shuai; Mao, Chang-Jie; Niu, He-Lin; Song, Ji-Ming; Jin, Bao-Kang

2018-09-26

Herein, we established a novel ultrasensitive photoelectrochemical biosensor for detecting urokinase-type plasminogen activator (u-PA), based on a g-C 3 N 4 /CdS nanocomposite. The prepared nanocomposite was characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible absorption spectroscopy, and Fourier transform infrared spectroscopy, thus indicating that the nanocomposite was prepared successfully. In the typical process, the prepared nanocomposite was deposited on the surface of a bare FTO electrode. After being air-dried, the g-C 3 N 4 /CdS nanocomposite modified electrode was successively incubated with antibody against urokinase-type plasminogen activator and the blocking agent BSA to produce a photoelectrochemical biosensor for u-PA. In the presence of target u-PA antigen, the photocurrent response of the prepared biosensor electrode decreased significantly. The proposed novel photoelectrochemical biosensor exhibited good sensitivity, specificity, and reproducibility for u-PA detection, and a low detection limit of 33 fg mL -1 , ranging from 1 μg mL -1 -0.1 pg mL -1 . The proposed strategy should provide a promising method for detection of other biomarkers. Copyright © 2018 Elsevier B.V. All rights reserved.

Installation of high-resolution ERDA in UTTAC at the University of Tsukuba: Determination of the energy resolution and the detection limit for hydrogen

Energy Technology Data Exchange (ETDEWEB)

Sekiba, D., E-mail: sekiba@tac.tsukuba.ac.jp [Institute of Applied Physics, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-8573 (Japan); University of Tsukuba, Tandem Accelerator Complex (UTTAC), Tennodai 1-1-1, Tsukuba, Ibaraki 305-8577 (Japan); Chito, K.; Harayama, I. [Institute of Applied Physics, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-8573 (Japan); Watahiki, Y.; Ishii, S. [University of Tsukuba, Tandem Accelerator Complex (UTTAC), Tennodai 1-1-1, Tsukuba, Ibaraki 305-8577 (Japan); Ozeki, K. [Department of Mechanical Engineering, Ibaraki University, Nakanarusawa 4-12-1, Hitachi, Ibaraki 316-8511 (Japan)

2017-06-15

A newly developed high-resolution elastic recoil detection analysis (HERDA) system installed at the 1 MV Tandetron in UTTAC at the University of Tsukuba is introduced. The effective solid angle of detector, energy resolution and detection limit for hydrogen are, for the first time, determined quantitatively by the measurements on an a-C:H (and D) film deposited on a Si substrate. In the case of a 500 keV {sup 16}O{sup +} as the incident beam, an energy resolution of ∼0.45 keV and a detection limit of ∼3.8 × 10{sup 20} atoms/cm{sup 3} (∼0.18 at.%) with a data acquisition time of ∼310 s are derived.

Ebolavirus diagnosis made simple, comparable and faster than molecular detection methods: preparing for the future.

Science.gov (United States)

James, Ameh S; Todd, Shawn; Pollak, Nina M; Marsh, Glenn A; Macdonald, Joanne

2018-04-23

The 2014/2015 Ebolavirus outbreak resulted in more than 28,000 cases and 11,323 reported deaths, as of March 2016. Domestic transmission of the Guinea strain associated with the outbreak occurred mainly in six African countries, and international transmission was reported in four countries. Outbreak management was limited by the inability to rapidly diagnose infected cases. A further fifteen countries in Africa are predicted to be at risk of Ebolavirus outbreaks in the future as a consequence of climate change and urbanization. Early detection of cases and reduction of transmission rates is critical to prevent and manage future severe outbreaks. We designed a rapid assay for detection of Ebolavirus using recombinase polymerase amplification, a rapid isothermal amplification technology that can be combined with portable lateral flow detection technology. The developed rapid assay operates in 30 min and was comparable with real-time TaqMan™ PCR. Designed, screened, selected and optimized oligonucleotides using the NP coding region from Ebola Zaire virus (Guinea strain). We determined the analytical sensitivity of our Ebola rapid molecular test by testing selected primers and probe with tenfold serial dilutions (1.34 × 10 10-  1.34 × 10 1 copies/μL) of cloned NP gene from Mayinga strain of Zaire ebolavirus in pCAGGS vector, and serially diluted cultured Ebolavirus as established by real-time TaqMan™ PCR that was performed using ABI7500 in Fast Mode. We tested extracted and reverse transcribed RNA from cultured Zaire ebolavirus strains - Mayinga, Gueckedou C05, Gueckedou C07, Makona, Kissidougou and Kiwit. We determined the analytical specificity of our assay with related viruses: Marburg, Ebola Reston and Ebola Sudan. We further tested for Dengue virus 1-4, Plasmodium falciparum and West Nile Virus (Kunjin strain). The assay had a detection limit of 134 copies per μL of plasmid containing the NP gene of Ebolavirus Mayinga, and cultured Ebolavirus

Current limitations and challenges in nanowaste detection, characterisation and monitoring

Energy Technology Data Exchange (ETDEWEB)

Part, Florian; Zecha, Gudrun [Department of Water-Atmosphere-Environment, University of Natural Resources and Life Sciences, Institute of Waste Management, Muthgasse 107, 1190 Vienna (Austria); Causon, Tim [Department of Chemistry, Division of Analytical Chemistry, University of Natural Resources and Life Sciences, Muthgasse 18, 1190 Vienna (Austria); Sinner, Eva-Kathrin [Department of Nanobiotechnology, Institute for Synthetic Bioarchitectures, University of Natural Resources and Life Sciences, Muthgasse 11/II, 1190 Vienna (Austria); Huber-Humer, Marion, E-mail: marion.huber-humer@boku.ac.at [Department of Water-Atmosphere-Environment, University of Natural Resources and Life Sciences, Institute of Waste Management, Muthgasse 107, 1190 Vienna (Austria)

2015-09-15

Highlights: • First review on detection of nanomaterials in complex waste samples. • Focus on nanoparticles in solid, liquid and gaseous waste samples. • Summary of current applicable methods for nanowaste detection and characterisation. • Limitations and challenges of characterisation of nanoparticles in waste. - Abstract: Engineered nanomaterials (ENMs) are already extensively used in diverse consumer products. Along the life cycle of a nano-enabled product, ENMs can be released and subsequently accumulate in the environment. Material flow models also indicate that a variety of ENMs may accumulate in waste streams. Therefore, a new type of waste, so-called nanowaste, is generated when end-of-life ENMs and nano-enabled products are disposed of. In terms of the precautionary principle, environmental monitoring of end-of-life ENMs is crucial to allow assessment of the potential impact of nanowaste on our ecosystem. Trace analysis and quantification of nanoparticulate species is very challenging because of the variety of ENM types that are used in products and low concentrations of nanowaste expected in complex environmental media. In the framework of this paper, challenges in nanowaste characterisation and appropriate analytical techniques which can be applied to nanowaste analysis are summarised. Recent case studies focussing on the characterisation of ENMs in waste streams are discussed. Most studies aim to investigate the fate of nanowaste during incineration, particularly considering aerosol measurements; whereas, detailed studies focusing on the potential release of nanowaste during waste recycling processes are currently not available. In terms of suitable analytical methods, separation techniques coupled to spectrometry-based methods are promising tools to detect nanowaste and determine particle size distribution in liquid waste samples. Standardised leaching protocols can be applied to generate soluble fractions stemming from solid wastes, while

Detection of Salmonella enterica in Meat in Less than 5 Hours by a Low-Cost and Noncomplex Sample Preparation Method.

Science.gov (United States)

Fachmann, M S R; Löfström, C; Hoorfar, J; Hansen, F; Christensen, J; Mansdal, S; Josefsen, M H

2017-03-01

Salmonella is recognized as one of the most important foodborne bacteria and has wide health and socioeconomic impacts worldwide. Fresh pork meat is one of the main sources of Salmonella , and efficient and fast methods for detection are therefore necessary. Current methods for Salmonella detection in fresh meat usually include >16 h of culture enrichment, in a few cases IMPORTANCE While the cost of analysis and hands-on time of the presented rapid method were comparable to those of reference culture methods, the fast product release by this method can provide the meat industry with a competitive advantage. Not only will the abattoirs save costs for work hours and cold storage, but consumers and retailers will also benefit from fresher meat with a longer shelf life. Furthermore, the presented sample preparation might be adjusted for application in the detection of other pathogenic bacteria in different sample types. Copyright © 2017 American Society for Microbiology.

Bioequivalence of three florfenicol preparations in broilers

Directory of Open Access Journals (Sweden)

Husamettin Ekici

2014-12-01

Full Text Available This study was aimed to determine the bioequivalence of three different preparations of florfenicol using non-drugged broiler chickens. A total of 28 broiler chickens aging 30-day were divided into four equal groups; these were Group I, II, III, and IV. The birds of Group I (for effective substance were given intravenous (i.v. administration of florfenicol dosed at 40 mg/kg body weight (b.wt.. The birds of Group II (for reference drug, Group III (for test-1 drug, and Group IV (for test-2 drug received florfenicol preparations with water (dosed at 40 mg/kg b.wt. through intracrop administration. Blood samples were collected periodically from the birds of all four groups, and blood plasma was separated. Levels of florfenicol and its metabolite (florfenicol amine in the plasma were measured by High Performance Liquid Chromatography (HPLC. In this study, the limit of detection (LOD for florfenicol and florfenicol amine were recorded as 0.017 and 0.78 µg/mL, respectively. On the other hand, the recovery of florfenicol and florfenicol amine were 83.4-84.6 and 82.2-83.8%, respectively. Based on the values of area under the curve (AUC, maximum concentration (Cmax, and time to maximum concentration (Tmax, test-1 drug was found to be acceptable, whereas test-2 drug was remained below the acceptable limits (80-125% of AUC and Cmax. Thus, it was concluded that test-1 drug was bioequivalent as compared to the reference drug.

Intrinsic spatial resolution limitations due to differences between positron emission position and annihilation detection localization

International Nuclear Information System (INIS)

Perez, Pedro; Malano, Francisco; Valente, Mauro

2012-01-01

Since its successful implementation for clinical diagnostic, positron emission tomography (PET) represents the most promising medical imaging technique. The recent major growth of PET imaging is mainly due to its ability to trace the biologic pathways of different compounds in the patient's body, assuming the patient can be labeled with some PET isotope. Regardless of the type of isotope, the PET imaging method is based on the detection of two 511-keV gamma photons being emitted in opposite directions, with almost 180 deg between them, as a consequence of electron-positron annihilation. Therefore, this imaging method is intrinsically limited by random uncertainties in spatial resolutions, related with differences between the actual position of positron emission and the location of the detected annihilation. This study presents an approach with the Monte Carlo method to analyze the influence of this effect on different isotopes of potential implementation in PET. (author)

Simple fluorimetric liquid chromatographic method for the analysis of undecylenic acid and zinc undecylenate in pharmaceutical preparations.

Science.gov (United States)

Lin, Ming-Chun; Wu, Hsin-Lung; Kou, Hwang-Shang; Wu, Shou-Mei

2006-06-30

A simple and selective liquid chromatographic method is described for the analysis of undecylenic acid (UA) and zinc undecylenate (ZnUA) in pharmaceutical preparations. The method is based on the derivatization of the analytes extracted from various samples with 2-(2-naphthoxy)ethyl 2-(piperidino)ethanesulfonate. The resulting derivative was analyzed by liquid chromatography with fluorimetric detection. The quantitation of the method is in the range of 3.0-50.0 microM UA with a detection limit of about 0.3 microM (S/N = 3 with 10 microl injection). We found that acetonitrile is a selective solvent for differentially dissolving UA from coexisted ZnUA in compound formulation. This results in the specific analysis of UA in the presence of ZnUA and simply analyzing the coexisted ZnUA by the value of total UA (UA+ZnUA) minus that of UA. Application of the method to the analysis of undecylenic acid and zinc undecylenate in ointment, powder and solution preparations proved feasible.

Breath Analysis Using Laser Spectroscopic Techniques: Breath Biomarkers, Spectral Fingerprints, and Detection Limits

Directory of Open Access Journals (Sweden)

Peeyush Sahay

2009-10-01

Full Text Available Breath analysis, a promising new field of medicine and medical instrumentation, potentially offers noninvasive, real-time, and point-of-care (POC disease diagnostics and metabolic status monitoring. Numerous breath biomarkers have been detected and quantified so far by using the GC-MS technique. Recent advances in laser spectroscopic techniques and laser sources have driven breath analysis to new heights, moving from laboratory research to commercial reality. Laser spectroscopic detection techniques not only have high-sensitivity and high-selectivity, as equivalently offered by the MS-based techniques, but also have the advantageous features of near real-time response, low instrument costs, and POC function. Of the approximately 35 established breath biomarkers, such as acetone, ammonia, carbon dioxide, ethane, methane, and nitric oxide, 14 species in exhaled human breath have been analyzed by high-sensitivity laser spectroscopic techniques, namely, tunable diode laser absorption spectroscopy (TDLAS, cavity ringdown spectroscopy (CRDS, integrated cavity output spectroscopy (ICOS, cavity enhanced absorption spectroscopy (CEAS, cavity leak-out spectroscopy (CALOS, photoacoustic spectroscopy (PAS, quartz-enhanced photoacoustic spectroscopy (QEPAS, and optical frequency comb cavity-enhanced absorption spectroscopy (OFC-CEAS. Spectral fingerprints of the measured biomarkers span from the UV to the mid-IR spectral regions and the detection limits achieved by the laser techniques range from parts per million to parts per billion levels. Sensors using the laser spectroscopic techniques for a few breath biomarkers, e.g., carbon dioxide, nitric oxide, etc. are commercially available. This review presents an update on the latest developments in laser-based breath analysis.

Optimizing Taq polymerase concentration for improved signal-to-noise in the broad range detection of low abundance bacteria.

Directory of Open Access Journals (Sweden)

Rudolph Spangler

Full Text Available BACKGROUND: PCR in principle can detect a single target molecule in a reaction mixture. Contaminating bacterial DNA in reagents creates a practical limit on the use of PCR to detect dilute bacterial DNA in environmental or public health samples. The most pernicious source of contamination is microbial DNA in DNA polymerase preparations. Importantly, all commercial Taq polymerase preparations inevitably contain contaminating microbial DNA. Removal of DNA from an enzyme preparation is problematical. METHODOLOGY/PRINCIPAL FINDINGS: This report demonstrates that the background of contaminating DNA detected by quantitative PCR with broad host range primers can be decreased greater than 10-fold through the simple expedient of Taq enzyme dilution, without altering detection of target microbes in samples. The general method is: For any thermostable polymerase used for high-sensitivity detection, do a dilution series of the polymerase crossed with a dilution series of DNA or bacteria that work well with the test primers. For further work use the concentration of polymerase that gave the least signal in its negative control (H(2O while also not changing the threshold cycle for dilutions of spiked DNA or bacteria compared to higher concentrations of Taq polymerase. CONCLUSIONS/SIGNIFICANCE: It is clear from the studies shown in this report that a straightforward procedure of optimizing the Taq polymerase concentration achieved "treatment-free" attenuation of interference by contaminating bacterial DNA in Taq polymerase preparations. This procedure should facilitate detection and quantification with broad host range primers of a small number of bona fide bacteria (as few as one in a sample.

Comparison of DNA extraction kits for detection of Burkholderia pseudomallei in spiked human whole blood using real-time PCR.

Directory of Open Access Journals (Sweden)

Nicole L Podnecky

Full Text Available Burkholderia pseudomallei, the etiologic agent of melioidosis, is endemic in northern Australia and Southeast Asia and can cause severe septicemia that may lead to death in 20% to 50% of cases. Rapid detection of B. pseudomallei infection is crucial for timely treatment of septic patients. This study evaluated seven commercially available DNA extraction kits to determine the relative recovery of B. pseudomallei DNA from spiked EDTA-containing human whole blood. The evaluation included three manual kits: the QIAamp DNA Mini kit, the QIAamp DNA Blood Mini kit, and the High Pure PCR Template Preparation kit; and four automated systems: the MagNAPure LC using the DNA Isolation Kit I, the MagNAPure Compact using the Nucleic Acid Isolation Kit I, and the QIAcube using the QIAamp DNA Mini kit and the QIAamp DNA Blood Mini kit. Detection of B. pseudomallei DNA extracted by each kit was performed using the B. pseudomallei specific type III secretion real-time PCR (TTS1 assay. Crossing threshold (C T values were used to compare the limit of detection and reproducibility of each kit. This study also compared the DNA concentrations and DNA purity yielded for each kit. The following kits consistently yielded DNA that produced a detectable signal from blood spiked with 5.5×10(4 colony forming units per mL: the High Pure PCR Template Preparation, QIAamp DNA Mini, MagNA Pure Compact, and the QIAcube running the QIAamp DNA Mini and QIAamp DNA Blood Mini kits. The High Pure PCR Template Preparation kit yielded the lowest limit of detection with spiked blood, but when this kit was used with blood from patients with confirmed cases of melioidosis, the bacteria was not reliably detected indicating blood may not be an optimal specimen.

Communication Games Reveal Preparation Contextuality

Science.gov (United States)

Hameedi, Alley; Tavakoli, Armin; Marques, Breno; Bourennane, Mohamed

2017-12-01

A communication game consists of distributed parties attempting to jointly complete a task with restricted communication. Such games are useful tools for studying limitations of physical theories. A theory exhibits preparation contextuality whenever its predictions cannot be explained by a preparation noncontextual model. Here, we show that communication games performed in operational theories reveal the preparation contextuality of that theory. For statistics obtained in a particular family of communication games, we show a direct correspondence with correlations in spacelike separated events obeying the no-signaling principle. Using this, we prove that all mixed quantum states of any finite dimension are preparation contextual. We report on an experimental realization of a communication game involving three-level quantum systems from which we observe a strong violation of the constraints of preparation noncontextuality.

Impact of patient education on quality of bowel preparation in outpatient colonoscopies.

Science.gov (United States)

Modi, Chintan; Depasquale, Joseph R; Digiacomo, W Scott; Malinowski, Judith E; Engelhardt, Kristen; Shaikh, Sohail N; Kothari, Shivangi T; Kottam, Raghu; Shakov, Rada; Maksoud, Charbel; Baddoura, Walid J; Spira, Robert S

2009-01-01

High-quality bowel preparation is essential for successful outpatient colonoscopy. Currently, the rate of adequate bowel preparation for outpatient colonoscopy in the USA is low. Patients often fail to adhere to recommended preparation instructions. Limited literature exists on evaluating educational intervention as a means of improving the quality of bowel preparation prior to outpatient colonoscopy. Our objective was to determine the effect of an educational intervention on the quality of outpatient colonoscopy preparation. The secondary objective was to determine whether the quality of bowel preparation improves overall colonoscopy outcomes as measured by rate of polyp detection and caecal intubation time. A single-blinded, prospective, randomised, controlled trial was conducted in two inner-city gastroenterology clinics in the USA. One hundred and sixty-four subjects were enrolled and randomly assigned to one of two groups. The control group subjects received verbal and written instructions for colonoscopy. The intervention group subjects received the same instructions and were then asked to answer a questionnaire. The subjects' responses were reviewed and an additional explanation of the preparation process provided. An attending gastroenterologist determined the quality of each bowel preparation at the time of colonoscopy using the Universal Preparation Assessment Scale. The educational intervention had no impact on the overall quality of bowel preparation (P=0.12). However, the type of food (liquid vs solid) consumed during the 24 hours prior to the procedure (P=0.04) and the time since the last solid meal (P=0.03) did have an impact on preparation quality. Other significant factors included elapsed time to first bowel movement from the initiation of bowel preparation (P=0.05) and age younger than 55 (P=0.02). Adequate bowel preparation was associated with shorter total procedure (P=0.001) and caecal intubation (P=0.01) times. Our study failed to demonstrate

Comparison of sensitivities and detection limits between direct excitation and secondary excitation modes in energy dispersive x-ray fluorescence analysis

International Nuclear Information System (INIS)

Artz, B.E.; Short, M.A.

1976-01-01

A comparison was made between the direct tube excitation mode and the secondary target excitation mode using a Kevex 0810 energy dispersive x-ray fluorescence system. Relative sensitivities and detection limits were determined with two system configurations. The first configuration used a standard, high power, x-ray fluorescence tube to directly excite the specimen. Several x-ray tubes, including chromium, molybdenum, and tungsten, both filtered and not filtered, were employed. The second configuration consisted of using the x-ray tube to excite a secondary target which in turn excited the specimen. Appropriate targets were compared to the direct excitation results. Relative sensitivities and detection limits were determined for K-series lines for elements from magnesium to barium contained in a low atomic number matrix and in a high atomic number matrix

Scheme for efficient extraction of low-frequency signal beyond the quantum limit by frequency-shift detection.

Science.gov (United States)

Yang, R G; Zhang, J; Zhai, Z H; Zhai, S Q; Liu, K; Gao, J R

2015-08-10

Low-frequency (Hz~kHz) squeezing is very important in many schemes of quantum precision measurement. But it is more difficult than that at megahertz-frequency because of the introduction of laser low-frequency technical noise. In this paper, we propose a scheme to obtain a low-frequency signal beyond the quantum limit from the frequency comb in a non-degenerate frequency and degenerate polarization optical parametric amplifier (NOPA) operating below threshold with type I phase matching by frequency-shift detection. Low-frequency squeezing immune to laser technical noise is obtained by a detection system with a local beam of two-frequency intense laser. Furthermore, the low-frequency squeezing can be used for phase measurement in Mach-Zehnder interferometer, and the signal-to-noise ratio (SNR) can be enhanced greatly.

Experimental study to optimize time resolution and detection limit of online 222Rn-in-water measurements

International Nuclear Information System (INIS)

Just, G.; Freyer, K.; Treutler, H.C.; Philipsborn, H. von

2001-01-01

The possibility to detect short-term variations of the activity concentration of 222 Rn in water by online monitoring with temporal resolutions of a few minutes and a lower limit of detection of about 1 Bq/l enhances the applicability of such measurements. New applications would be possible in the field of hydro-geology in which Rn is used as tracer gas, the monitoring of pumping procedures, for the study of exchange processes during groundwater sampling and for various applications with geophysical effects. A suitable, simple method is the measuring principle proposed by Surbeck (Fribourg) some years ago which is based on the separation of air and water by a diffusion membrane. Process parameters enhancing the time resolution of the method as well as the efficiency of different radon detectors have been studied. (orig.) [de

Evaluation of Pentachlorophenol Residues in Some Hygienic Papers Prepared from Virgin and Secondary Pulp by Electron Capture Gas Chromatographic Method

Directory of Open Access Journals (Sweden)

Behrouz Akbari-adergani

2016-01-01

Full Text Available In this study, residual amount of pentachlorophenol (PCP as the most important paper preservative, which is extremely hazardous pollutant, was determined in some tissue papers and napkins. Twenty-five samples of two producing hygienic paper factories prepared from virgin and secondary pulp were analyzed for the presence of trace amount of PCP. The analytical procedure involved direct extraction of PCP from hygienic paper and its determination by gas chromatography with electron capture detection. The statistical results for the analysis of all samples revealed that there were significant differences between mean of PCP in hygienic papers prepared from virgin and secondary pulp (P<0.05. This method gave recoveries of 86-98% for hygienic paper made from virgin pulp and 79-92% for hygienic paper made from secondary pulp. The limit of detection (LOD and limit of quantification (LOQ for PCP were 6.3 and 21.0 mg/kg, respectively. The analytical method has the requisite sensitivity, accuracy, precision and specificity to assay PCP in hygienic papers. This study demonstrates a concern with exposition to PCP considering that hygienic paper is largely consumed in the society.

Flexible and Compressible PEDOT:PSS@Melamine Conductive Sponge Prepared via One-Step Dip Coating as Piezoresistive Pressure Sensor for Human Motion Detection.

Science.gov (United States)

Ding, Yichun; Yang, Jack; Tolle, Charles R; Zhu, Zhengtao

2018-05-09

Flexible and wearable pressure sensor may offer convenient, timely, and portable solutions to human motion detection, yet it is a challenge to develop cost-effective materials for pressure sensor with high compressibility and sensitivity. Herein, a cost-efficient and scalable approach is reported to prepare a highly flexible and compressible conductive sponge for piezoresistive pressure sensor. The conductive sponge, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)@melamine sponge (MS), is prepared by one-step dip coating the commercial melamine sponge (MS) in an aqueous dispersion of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). Due to the interconnected porous structure of MS, the conductive PEDOT:PSS@MS has a high compressibility and a stable piezoresistive response at the compressive strain up to 80%, as well as good reproducibility over 1000 cycles. Thereafter, versatile pressure sensors fabricated using the conductive PEDOT:PSS@MS sponges are attached to the different parts of human body; the capabilities of these devices to detect a variety of human motions including speaking, finger bending, elbow bending, and walking are evaluated. Furthermore, prototype tactile sensory array based on these pressure sensors is demonstrated.

Effect of sample matrix composition on INAA sample weights, measurement precisions, limits of detection, and optimum conditions

International Nuclear Information System (INIS)

Guinn, V.P.; Nakazawa, L.; Leslie, J.

1984-01-01

The instrumental neutron activation analysis (INAA) Advance Prediction Computer Program (APCP) is extremely useful in guiding one to optimum subsequent experimental analyses of samples of all types of matrices. By taking into account the contributions to the cumulative Compton-continuum levels from all significant induced gamma-emitting radionuclides, it provides good INAA advance estimates of detectable photopeaks, measurement precisions, concentration lower limits of detection (LOD's) and optimum irradiation/decay/counting conditions - as well as of the very important maximum allowable sample size for each set of conditions calculated. The usefulness and importance of the four output parameters cited in the title are discussed using the INAA APCP outputs for NBS SRM-1632 Coal as the example

Preparation of magnetic ODS-PAN thin-films for microextraction of quetiapine and clozapine in plasma and urine samples followed by HPLC-UV detection.

Science.gov (United States)

Li, Dan; Zou, Juan; Cai, Pei-Shan; Xiong, Chao-Mei; Ruan, Jin-Lan

2016-06-05

In this study, conventional thin-film microextraction (TFME) was endowed with magnetic by introducing superparamagnetic SiO2@Fe3O4 nanoparticles in thin-films. Novel magnetic octadecylsilane (ODS)-polyacrylonitrile (PAN) thin-films were prepared by spraying, and used for the microextraction of quetiapine and clozapine in plasma and urine samples, followed by the detection of HPLC-UV. The influencing factors on the extraction efficiency of magnetic ODS-PAN TFME, including pH, extraction time, desorption solvent, desorption time, and ion strength were investigated systematically. Under the optimal conditions, both analytes showed good linearity over ranges of 0.070-9.000μgmL(-1) and 0.012-9.000μgmL(-1) in plasma and urine samples, respectively, with correlation coefficients (R(2)) above 0.9990. Limits of detection (LODs) for quetiapine in plasma and urine samples were 0.013 and 0.003μgmL(-1), respectively. LODs for clozapine in plasma and urine samples were 0.015 and 0.003μgmL(-1), respectively. The relative standard deviations (RSDs) for quetiapine and clozapine were less than 9.23%. After the validation, the protocol was successfully applied for the determination of quetiapine and clozapine in patients' plasma and urine samples with satisfactory recoveries between 99-110%. The proposed magnetic ODS-PAN TFME was very simple, fast and easy to handle. It showed high potential as a powerful pretreatment technology for routine therapeutic drug monitoring (TDM) in plasma and urine samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Recent advances in metal-organic frameworks and covalent organic frameworks for sample preparation and chromatographic analysis.

Science.gov (United States)

Wang, Xuan; Ye, Nengsheng

2017-12-01

In the field of analytical chemistry, sample preparation and chromatographic separation are two core procedures. The means by which to improve the sensitivity, selectivity and detection limit of a method have become a topic of great interest. Recently, porous organic frameworks, such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), have been widely used in this research area because of their special features, and different methods have been developed. This review summarizes the applications of MOFs and COFs in sample preparation and chromatographic stationary phases. The MOF- or COF-based solid-phase extraction (SPE), solid-phase microextraction (SPME), gas chromatography (GC), high-performance liquid chromatography (HPLC) and capillary electrochromatography (CEC) methods are described. The excellent properties of MOFs and COFs have resulted in intense interest in exploring their performance and mechanisms for sample preparation and chromatographic separation. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Improved detection limit in rapid detection of human enterovirus 71 and coxsackievirus A16 by a novel reverse transcription-isothermal multiple-self-matching-initiated amplification assay.

Science.gov (United States)

Ding, Xiong; Nie, Kai; Shi, Lei; Zhang, Yong; Guan, Li; Zhang, Dan; Qi, Shunxiang; Ma, Xuejun

2014-06-01

Rapid detection of human enterovirus 71 (EV71) and coxsackievirus A16 (CVA16) is important in the early phase of hand-foot-and-mouth disease (HFMD). In this study, we developed and evaluated a novel reverse transcription-isothermal multiple-self-matching-initiated amplification (RT-IMSA) assay for the rapid detection of EV71 and CVA16 by use of reverse transcriptase, together with a strand displacement DNA polymerase. Real-time RT-IMSA assays using a turbidimeter and visual RT-IMSA assays to detect EV71 and CVA16 were established and completed in 1 h, and the reported corresponding real-time reverse transcription-loop-mediated isothermal amplification (RT-LAMP) assays targeting the same regions of the VP1 gene were adopted as parallel tests. Through testing VP1 RNAs transcribed in vitro, the real-time RT-IMSA assays exhibited better linearity of quantification, with R(2) values of 0.952 (for EV71) and 0.967 (for CVA16), than the real-time RT-LAMP assays, which had R(2) values of 0.803 (for EV71) and 0.904 (for CVA16). Additionally, the detection limits of the real-time RT-IMSA assays (approximately 937 for EV71 and 67 for CVA16 copies/reaction) were higher than those of real-time RT-LAMP assays (approximately 3,266 for EV71 and 430 for CVA16 copies/reaction), and similar results were observed in the visual RT-IMSA assays. The new approaches also possess high specificities for the corresponding targets, with no cross-reactivity observed. In clinical assessment, compared to commercial reverse transcription-quantitative PCR (qRT-PCR) kits, the diagnostic sensitivities of the real-time RT-IMSA assays (96.4% for EV71 and 94.6% for CVA16) were higher than those of the real-time RT-LAMP assays (91.1% for EV71 and 90.8% for CVA16). The visual RT-IMSA assays also exhibited the same results. In conclusion, this proof-of-concept study suggests that the novel RT-IMSA assay is superior to the RT-LAMP assay in terms of detection limit and has the potential to rapidly detect EV71

Left ventricular time volume curve analysis in the detection of limited ischaemic heart disease

International Nuclear Information System (INIS)

Liechtenstein, M.; Blanchett, W.; Andrews, J.; Hunt, D.

1982-01-01

The aim of the study was to determine whether limited coronary artery disease (CAD) could be accurately detected using the Cardiac Gated Blood Pool (CGBP) scan with exercise. Regional left ventricular time volume curves (RLTVD) were generated from 52 studies (46 patients: 22 normals, 24 abnormals). The parameters assessed both globally and regionally and at rest (R) and exercise (Ex) were: (1) the ejection fraction (EF) (2) the change in ejection fraction from R to Ex (δEF) (3) an early contraction index (ECI) (4) a maximal emptying index (DR) and (5) a maximal refilling index (AR). After careful analysis of these parameters it was decided that our diagnostic criteria would rely on the following: (1) the EF at R and Ex (2) the δ EF (3) the ECI at Ex (4) the AR at Ex This study showed that both the sensitivity and the specificity of the CGBP scan can be improved considerably with the inclusion of RLTVC from the levels obtained when the EF parameters alone are considered. It is possible with this technique to accurately diagnose limited CAD. (Author)

Improved detection limits for phthalates by selective solid-phase micro-extraction

KAUST Repository

Zia, Asif I.

2016-03-30

Presented research reports on an improved method and enhanced limits of detection for phthalates; a hazardous additive used in the production of plastics by solid-phase micro-extraction (SPME) polymer in comparison to molecularly imprinted solid-phase extraction (MISPE) polymer. The polymers were functionalized on an interdigital capacitive sensor for selective binding of phthalate molecules from a complex mixture of chemicals. Both polymers owned predetermined selectivity by formation of valuable molecular recognition sites for Bis (2-ethylhexyl) phthalate (DEHP). Polymers were immobilized on planar electrochemical sensor fabricated on a single crystal silicon substrate with 500 nm sputtered gold electrodes fabricated using MEMS fabrication techniques. Impedance spectra were obtained using electrochemical impedance spectroscopy (EIS) to determine sample conductance for evaluation of phthalate concentration in the spiked sample solutions with various phthalate concentrations. Experimental results revealed that the ability of SPME polymer to adsorb target molecules on the sensing surface is better than that of MISPE polymer for phthalates in the sensing system. Testing the extracted samples using high performance liquid chromatography with photodiode array detectors validated the results.

Functional graphene-gold nano-composite fabricated electrochemical biosensor for direct and rapid detection of bisphenol A.

Science.gov (United States)

Pan, Daodong; Gu, Yuanyuan; Lan, Hangzhen; Sun, Yangying; Gao, Huiju

2015-01-01

In this research, the graphene with excellent dispersity is prepared successfully by introducing gold nanoparticle to separate the individual sheets. Various techniques are adopted to characterize the prepared graphene and graphene-gold nanoparticle composite materials. This fabricated new composite material is used as the support material to construct a novel tyrosinase based biosensor for detection of bisphenol A (BPA). The electrochemical performances of the proposed new enzyme biosensor were investigated by differential pulse voltammetry (DPV) method. The proposed biosensor exhibited excellent performance for BPA determination with a wide linear range (2.5×10(-3)-3.0 μM), a highly reproducible response (RSD of 2.7%), low interferences and long-term stability. And more importantly, the calculated detection limit of the proposed biosensor was as low as 1 nM. Compared with other detection methods, this graphene-gold nanoparticle composite based tyrosinase biosensor is proved to be a promising and reliable tool for rapid detection of BPA for on-site analysis of emergency BPA related pollution affairs. Copyright © 2014 Elsevier B.V. All rights reserved.

40 CFR Appendix C to Part 425 - Definition and Procedure for the Determination of the Method Detection Limit 1

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 29 2010-07-01 2010-07-01 false Definition and Procedure for the Determination of the Method Detection Limit 1 C Appendix C to Part 425 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS LEATHER TANNING AND FINISHING POINT SOURCE...

Automated Purification and Suspension Array Detection of 16S rRNA from Soil and Sediment Extracts by Using Tunable Surface Microparticles

OpenAIRE

Chandler, Darrell P.; Jarrell, Ann E.

2004-01-01

Autonomous, field-deployable molecular detection systems require seamless integration of complex biochemical solutions and physical or mechanical processing steps. In an attempt to simplify the fluidic requirements for integrated biodetection systems, we used tunable surface microparticles both as an rRNA affinity purification resin in a renewable microcolumn sample preparation system and as the sensor surface in a flow cytometer detector. The tunable surface detection limits in both low- and...

Confocal laser-induced fluorescence detector for narrow capillary system with yoctomole limit of detection.

Science.gov (United States)

Weaver, Mitchell T; Lynch, Kyle B; Zhu, Zaifang; Chen, Huang; Lu, Joann J; Pu, Qiaosheng; Liu, Shaorong

2017-04-01

Laser-induced fluorescence (LIF) detectors for low-micrometer and sub-micrometer capillary on-column detection are not commercially available. In this paper, we describe in details how to construct a confocal LIF detector to address this issue. We characterize the detector by determining its limit of detection (LOD), linear dynamic range (LDR) and background signal drift; a very low LOD (~70 fluorescein molecules or 12 yoctomole fluorescein), a wide LDR (greater than 3 orders of magnitude) and a small background signal drift (~1.2-fold of the root mean square noise) are obtained. For detecting analytes inside a low-micrometer and sub-micrometer capillary, proper alignment is essential. We present a simple protocol to align the capillary with the optical system and use the position-lock capability of a translation stage to fix the capillary in position during the experiment. To demonstrate the feasibility of using this detector for narrow capillary systems, we build a 2-μm-i.d. capillary flow injection analysis (FIA) system using the newly developed LIF prototype as a detector and obtain an FIA LOD of 14 zeptomole fluorescein. We also separate a DNA ladder sample by bare narrow capillary - hydrodynamic chromatography and use the LIF prototype to monitor the resolved DNA fragments. We obtain not only well-resolved peaks but also the quantitative information of all DNA fragments. Copyright © 2016 Elsevier B.V. All rights reserved.

New potentiometric and spectrophotometric methods for the determination of dextromethorphan in pharmaceutical preparations.

Science.gov (United States)

Elmosallamy, Mohamed A F; Amin, Alaa S

2014-01-01

New, simple and convenient potentiometric and spectrophotometric methods are described for the determination of dextromethorphan hydrobromide (DXM) in pharmaceutical preparations. The potentiometric technique is based on developing a potentiometric sensor incorporating the dextromethorphan tetrakis(p-chlorophenyl)borate ion-pair complex as an electroactive species in a plasticized PVC matrix membrane with o-nitophenyl octyl ether or dioctyl phthalate. The sensor shows a rapid near Nernstian response of over 1 × 10(-5) - 1 × 10(-2) mol L(-1) dextromethorphan in the pH range of 3.0 - 9.0. The detection limit is 2 × 10(-6) mol L(-1) DXM and the response time is instantaneous (2 s). The proposed spectrophotometric technique involves the reaction of DXM with eriochrom black T (EBT) to form an ion-associate complex. Solvent extraction is used to improve the selectivity of the method. The optimal extraction and reaction conditions have been studied, and the analytical characteristics of the method have been obtained. Linearity is obeyed in the range of 7.37 - 73.7 × 10(-5) mol L(-1) DXM, and the detection limit of the method is 1.29 × 10(-5) mol L(-1). The relative standard deviation (RSD) and relative error for six replicate measurements of 3.685 × 10(-4) mol L(-1) are 0.672 and 0.855%, respectively. The interference effect of some excepients has also been tested. The drug contents in pharmaceutical preparations were successfully determined by the proposed methods by applying the standard-addition technique.

Synthesis of CdS quantum dots decorated graphene nanosheets and non-enzymatic photoelectrochemical detection of glucose

International Nuclear Information System (INIS)

Zhang, Xuyan; Xu, Fang; Zhao, Bingqing; Ji, Xin; Yao, Yanwen; Wu, Dapeng; Gao, Zhiyong; Jiang, Kai

2014-01-01

Graphical abstract: - Highlights: • Graphene-CdS hybrid materials were prepared via one-step hydrothermal method. • Graphene-CdS was used as non-enzymatic photoelectrochemical sensor to detect glucose. • Glucose in real sample was detected and showed good specificity and sensitivity. - ABSTRACT: Graphene-CdS quantum dots (QDs) hybrid materials were successfully prepared via one-step hydrothermal method. CdS QDs with average size of ∼6 nm were dispersed on graphene sheets with high coverage through non-covalent bonding. Photocurrent and electrochemical impedance spectroscopy (EIS) results suggested that the best dosage of graphene oxide for graphene-CdS hybrid materials is 0.5% (G0.5-CdS). When G0.5-CdS QDs was used as photoanode materials in non-enzymatic sensor, and the sensor was used to detect glucose and displayed satisfactory analytical performance with good linear range from 0.1∼4 mmol dm −3 with a detection limit of 7 μmol dm −3 at a signal-to-noise ratio of 3. The sensor also possessed high selectivity and durability in trace detection of glucose

Limited magnetic resonance imaging of the lumbar spine has high sensitivity for detection of acute fractures, infection, and malignancy

International Nuclear Information System (INIS)

Wang, Benjamin; Fintelmann, Florian J.; Kamath, Ravi S.; Kattapuram, Susan V.; Rosenthal, Daniel I.

2016-01-01

The objective of this study is to determine how a limited protocol MR examination compares to a full conventional MR examination for the detection of non-degenerative pathology such as acute fracture, infection, and malignancy. A sample of 349 non-contrast MR exams was selected retrospectively containing a 3:1:1:1 distribution of negative/degenerative change only, acute fracture, infection, and malignancy. This resulted in an even distribution of pathology and non-pathology. A limited protocol MR exam was simulated by extracting T1-weighted sagittal and T2-weighted fat-saturated (or STIR) sagittal sequences from each exam and submitting them for blinded review by two experienced musculoskeletal radiologists. The exams were evaluated for the presence or absence of non-degenerative pathology. Interpretation of the limited exam was compared to the original report of the full examination. If either reader disagreed with the original report, the case was submitted for an unblinded adjudication process with the participation of a third musculoskeletal radiologist to establish a consensus diagnosis. There were five false negatives for a sensitivity of 96.9 % for the limited protocol MR exam. Infection in the psoas, paraspinal muscles, and sacroiliac joint, as well as acute fractures in transverse processes and sacrum were missed by one or more readers. No cases of malignancy were missed. Overall diagnostic accuracy was 96.0 % (335/349). MR imaging of the lumbar spine limited to sagittal T1-weighted and sagittal T2 fat-saturated (or STIR) sequences has high sensitivity for the detection of acute fracture, infection, or malignancy compared to a conventional MR examination. (orig.)

Limited magnetic resonance imaging of the lumbar spine has high sensitivity for detection of acute fractures, infection, and malignancy

Energy Technology Data Exchange (ETDEWEB)

Wang, Benjamin; Fintelmann, Florian J.; Kamath, Ravi S.; Kattapuram, Susan V.; Rosenthal, Daniel I. [Massachusetts General Hospital, Department of Radiology, Boston, MA (United States)

2016-12-15

The objective of this study is to determine how a limited protocol MR examination compares to a full conventional MR examination for the detection of non-degenerative pathology such as acute fracture, infection, and malignancy. A sample of 349 non-contrast MR exams was selected retrospectively containing a 3:1:1:1 distribution of negative/degenerative change only, acute fracture, infection, and malignancy. This resulted in an even distribution of pathology and non-pathology. A limited protocol MR exam was simulated by extracting T1-weighted sagittal and T2-weighted fat-saturated (or STIR) sagittal sequences from each exam and submitting them for blinded review by two experienced musculoskeletal radiologists. The exams were evaluated for the presence or absence of non-degenerative pathology. Interpretation of the limited exam was compared to the original report of the full examination. If either reader disagreed with the original report, the case was submitted for an unblinded adjudication process with the participation of a third musculoskeletal radiologist to establish a consensus diagnosis. There were five false negatives for a sensitivity of 96.9 % for the limited protocol MR exam. Infection in the psoas, paraspinal muscles, and sacroiliac joint, as well as acute fractures in transverse processes and sacrum were missed by one or more readers. No cases of malignancy were missed. Overall diagnostic accuracy was 96.0 % (335/349). MR imaging of the lumbar spine limited to sagittal T1-weighted and sagittal T2 fat-saturated (or STIR) sequences has high sensitivity for the detection of acute fracture, infection, or malignancy compared to a conventional MR examination. (orig.)

Preparation of MS2 phage-like particles and their use as potential process control viruses for detection and quantification of enteric RNA viruses in different matrices

Directory of Open Access Journals (Sweden)

Pavel Mikel

2016-12-01

Full Text Available The detection and quantification of enteric RNA viruses is based on isolation of viral RNA from the sample followed by quantitative reverse transcription polymerase chain reaction (RT-qPCR. To control the whole process of analysis and in order to guarantee the validity and reliability of results, process control viruses (PCV are used. The present article describes the process of preparation and use of such PCV– MS2 phage-like particles (MS2 PLP – in RT-qPCR detection and quantification of enteric RNA viruses. The MS2 PLP were derived from bacteriophage MS2 carrying a unique and specific de novo-constructed RNA target sequence originating from the DNA of two extinct species. The amount of prepared MS2 particles was quantified using four independent methods - UV spectrophotometry, fluorimetry, transmission electron microscopy (TEM and a specifically developed duplex RT-qPCR. To evaluate the usefulness of MS2 PLP in routine diagnostics different matrices known to harbor enteric RNA viruses (swab samples, liver tissue, serum, feces, and vegetables were artificially contaminated with specific amounts of MS2 PLP. The extraction efficiencies were calculated for each individual matrix. The prepared particles fulfill all requirements for PCV – they are very stable, non-infectious, and are genetically distinct from the target RNA viruses. Due to these properties they represent a good morphological and physiochemical model. The use of MS2 PLP as a PCV in detection and quantification of enteric RNA viruses was evaluated in different types of matrices.

Potential and limits of Raman spectroscopy for carotenoid detection in microorganisms: implications for astrobiology

Science.gov (United States)

Jehlička, Jan; Edwards, Howell G. M.; Osterrothová, Kateřina; Novotná, Julie; Nedbalová, Linda; Kopecký, Jiří; Němec, Ivan; Oren, Aharon

2014-01-01

In this paper, it is demonstrated how Raman spectroscopy can be used to detect different carotenoids as possible biomarkers in various groups of microorganisms. The question which arose from previous studies concerns the level of unambiguity of discriminating carotenoids using common Raman microspectrometers. A series of laboratory-grown microorganisms of different taxonomic affiliation was investigated, such as halophilic heterotrophic bacteria, cyanobacteria, the anoxygenic phototrophs, the non-halophilic heterotrophs as well as eukaryotes (Ochrophyta, Rhodophyta and Chlorophyta). The data presented show that Raman spectroscopy is a suitable tool to assess the presence of carotenoids of these organisms in cultures. Comparison is made with the high-performance liquid chromatography approach of analysing pigments in extracts. Direct measurements on cultures provide fast and reliable identification of the pigments. Some of the carotenoids studied are proposed as tracers for halophiles, in contrast with others which can be considered as biomarkers of other genera. The limits of application of Raman spectroscopy are discussed for a few cases where the current Raman spectroscopic approach does not allow discriminating structurally very similar carotenoids. The database reported can be used for applications in geobiology and exobiology for the detection of pigment signals in natural settings. PMID:25368348

Preparation of MIP grafts for quercetin by tandem aryl diazonium surface chemistry and photopolymerization

International Nuclear Information System (INIS)

Salmi, Zakaria; Benmehdi, Houcine; Lamouri, Aazdine; Decorse, Philippe; Jouini, Mohamed; Chehimi, Mohamed M.; Yagci, Yusuf

2013-01-01

The food antioxidant quercetin was used as a template in an ultrathin molecularly imprinted polymer (MIP) film prepared by photopolymerization. Indium tin oxide (ITO) plates were electrografted with aryl layers via a diazonium salt precursor bearing two terminal hydroxyethyl groups. The latter act as hydrogen donors for the photosensitizer isopropylthioxanthone and enabled the preparation of MIP grafts through radical photopolymerization of methacrylic acid (the functional monomer) and ethylene glycol dimethacrylate (the crosslinker) in the presence of quercetin (the template) on the ITO. The template was extracted, and the remaining ITO electrode used for the amperometric determination of quercetin at a working potential of 0.26 V (vs. SCE). The analytical range is from 5.10 −8 to 10 −4 mol L −1 , and the detection limit is 5.10 −8 mol L −1 . (author)

Composite Estimation for Single-Index Models with Responses Subject to Detection Limits

KAUST Repository

Tang, Yanlin; Wang, Huixia Judy; Liang, Hua

2017-01-01

We propose a semiparametric estimator for single-index models with censored responses due to detection limits. In the presence of left censoring, the mean function cannot be identified without any parametric distributional assumptions, but the quantile function is still identifiable at upper quantile levels. To avoid parametric distributional assumption, we propose to fit censored quantile regression and combine information across quantile levels to estimate the unknown smooth link function and the index parameter. Under some regularity conditions, we show that the estimated link function achieves the non-parametric optimal convergence rate, and the estimated index parameter is asymptotically normal. The simulation study shows that the proposed estimator is competitive with the omniscient least squares estimator based on the latent uncensored responses for data with normal errors but much more efficient for heavy-tailed data under light and moderate censoring. The practical value of the proposed method is demonstrated through the analysis of a human immunodeficiency virus antibody data set.

Composite Estimation for Single-Index Models with Responses Subject to Detection Limits

KAUST Repository

Tang, Yanlin

2017-11-03

We propose a semiparametric estimator for single-index models with censored responses due to detection limits. In the presence of left censoring, the mean function cannot be identified without any parametric distributional assumptions, but the quantile function is still identifiable at upper quantile levels. To avoid parametric distributional assumption, we propose to fit censored quantile regression and combine information across quantile levels to estimate the unknown smooth link function and the index parameter. Under some regularity conditions, we show that the estimated link function achieves the non-parametric optimal convergence rate, and the estimated index parameter is asymptotically normal. The simulation study shows that the proposed estimator is competitive with the omniscient least squares estimator based on the latent uncensored responses for data with normal errors but much more efficient for heavy-tailed data under light and moderate censoring. The practical value of the proposed method is demonstrated through the analysis of a human immunodeficiency virus antibody data set.

Molecularly imprinted fluorescent probe based on FRET for selective and sensitive detection of doxorubicin

Energy Technology Data Exchange (ETDEWEB)

Xu, Zhifeng, E-mail: 897061147@qq.com [College of Chemistry and Materials Science, Hengyang Normal University, Key Laboratory of Functional Organometallic Materials of Hunan Province University, Hengyang 421008 (China); Deng, Peihong; Li, Junhua [College of Chemistry and Materials Science, Hengyang Normal University, Key Laboratory of Functional Organometallic Materials of Hunan Province University, Hengyang 421008 (China); Xu, Li [Department of Applied Chemistry, College of Materials and Energy, South China Agricultural University, Guangzhou 510642 (China); Tang, Siping [College of Chemistry and Materials Science, Hengyang Normal University, Key Laboratory of Functional Organometallic Materials of Hunan Province University, Hengyang 421008 (China)

2017-04-15

Highlights: • FRET-based molecularly imprinted probe for detection of doxorubicin was prepared. • The detection limit of the probe was 13.8 nM for doxorubicin. • The FRET-based probe had a higher selectivity for the template than ordinary MIMs. - Abstract: In this work, a new type of fluorescent probe for detection of doxorubicin has been constructed by the combined use of fluorescence resonance energy transfer (FRET) technology and molecular imprinting technique (MIT). Using doxorubicin as the template, the molecularly imprinted polymer thin layer was fabricated on the surfaces of carbon dot (CD) modified silica by sol-gel polymerization. The excitation energy of the fluorescent donor (CDs) could be transferred to the fluorescent acceptor (doxorubicin). The FRET based fluorescent probe demonstrated high sensitivity and selectivity for doxorubicin. The detection limit was 13.8 nM. The fluorescent probe was successfully applied for detecting doxorubicin in doxorubicin-spiked plasmas with a recovery of 96.8–103.8%, a relative standard deviation (RSD) of 1.3–2.8%. The strategy for construction of FRET-based molecularly imprinted materials developed in this work is very promising for analytical applications.

Detection limits for radioanalytical counting techniques

International Nuclear Information System (INIS)

Hartwell, J.K.

1975-06-01

In low-level radioanalysis it is usually necessary to test the sample net counts against some ''Critical Level'' in order to determine if a given result indicates detection. This is an interpretive review of the work by Nicholson (1963), Currie (1968) and Gilbert (1974). Nicholson's evaluation of three different computational formulas for estimation of the ''Critical Level'' is discussed. The details of Nicholson's evaluation are presented along with a basic discussion of the testing procedures used. Recommendations are presented for calculation of confidence intervals, for reporting of analytical results, and for extension of the derived formula to more complex cases such as multiple background counts, multiple use of a single background count, and gamma spectrometric analysis

Trace detection of tetrahydrocannabinol (THC) with a SERS-based capillary platform prepared by the in situ microwave synthesis of AgNPs.

Science.gov (United States)

Yüksel, Sezin; Schwenke, Almut M; Soliveri, Guido; Ardizzone, Silvia; Weber, Karina; Cialla-May, Dana; Hoeppener, Stephanie; Schubert, Ulrich S; Popp, Jürgen

2016-10-05

In the present study, an ultra-sensitive and highly reproducible novel SERS-based capillary platform was developed and utilized for the trace detection of tetrahydrocannabinol (THC). The approach combines the advantages of microwave-assisted nanoparticle synthesis, plasmonics and capillary forces. By employing a microwave-assisted preparation method, glass capillaries were reproducibly coated with silver nanoparticles in a batch fabrication process that required a processing time of 3 min without needing to use any pre-surface modifications or add surfactants. The coated capillaries exhibited an excellent SERS activity with a high reproducibility and enabled the detection of low concentrations of target molecules. At the same time, only a small amount of analyte and a short and simple incubation process was required. The developed platform was applied to the spectroscopic characterization of tetrahydrocannabinol (THC) and its identification at concentration levels down to 1 nM. Thus, a highly efficient detection system for practical applications, e.g., in drug monitoring/detection, is introduced, which can be fabricated at low cost by using microwave-assisted batch synthesis techniques. Copyright © 2016 Elsevier B.V. All rights reserved.

A portable cell-based optical detection device for rapid detection of Listeria and Bacillus toxins

Science.gov (United States)

Banerjee, Pratik; Banada, Padmapriya P.; Rickus, Jenna L.; Morgan, Mark T.; Bhunia, Arun K.

2005-11-01

A mammalian cell-based optical biosensor was built to detect pathogenic Listeria and Bacillus species. This sensor measures the ability of the pathogens to infect and induce cytotoxicity on hybrid lymphocyte cell line (Ped-2E9) resulting in the release of alkaline phosphatase (ALP) that can be detected optically using a portable spectrophotometer. The Ped-2E9 cells were encapsulated in collagen gel matrices and grown in 48-well plates or in specially designed filtration tube units. Toxin preparations or bacterial cells were introduced and ALP release was assayed after 3-5 h. Pathogenic L. monocytogenes strains or the listeriolysin toxins preparation showed cytotoxicity ranging from 55% - 92%. Toxin preparations (~20 μg/ml) from B. cereus strains showed 24 - 98% cytotoxicity. In contrast, a non-pathogenic L. innocua (F4247) and a B. substilis induced only 2% and 8% cytotoxicity, respectively. This cell-based detection device demonstrates its ability to detect the presence of pathogenic Listeria and Bacillus species and can potentially be used onsite for food safety or in biosecurity application.

Assessment of detection limits of fiber-optic distributed temperature sensing for detection of illicit connections

NARCIS (Netherlands)

Nienhuis, J.; De Haan, C.; Langeveld, J.G.; Klootwijk, M.; Clemens, F.H.L.R.

2012-01-01

Distributed Temperature Sensing (DTS) with fiber-optic cables is a powerful tool to detect illicit connections in storm sewer systems. High frequency temperature measurements along the in-sewer cable create a detailed representation of temperature anomalies due to illicit discharges. The detection

Media-fill simulation tests in manual and robotic aseptic preparation of injection solutions in syringes.

Science.gov (United States)

Krämer, Irene; Federici, Matteo; Kaiser, Vanessa; Thiesen, Judith

2016-04-01

-amber solutions. In addition, the reliability of the nutrient medium and the process was demonstrated by positive growth promotion tests with S. epidermidis. During automated preparation the recommended limits manual preparation, the number of cfus detected on settle/contact plates inside the workbenches lay far below the limits. The number of cfus detected on fingertips succeeded several times the limit during manual preparation but not during automated preparation. There was no difference in the microbial contamination rate depending on the extent of cleaning and disinfection of the robot. Extensive media-fill tests simulating manual and automated preparation of ready-to-use cytotoxic injection solutions revealed the same level of sterility for both procedures. The results of supplemental environmental controls confirmed that the aseptic procedures are well controlled. As there was no difference in the microbial contamination rates of the media preparations depending on the extent of cleaning and disinfection of the robot, the results were used to adapt the respective standard operating procedures. © The Author(s) 2014.

PREPARATIVE ISOLATION AND PURIFICATION OF THREE GLYCINE-CONJUGATED CHOLIC ACIDS FROM PULVIS FELLIS SUIS BY HIGH-SPEED COUNTERCURRENT CHROMATOGRAPHY COUPLED WITH ELSD DETECTION

OpenAIRE

He, Jiao; Li, Jing; Sun, Wenji; Zhang, Tianyou; Ito, Yoichiro

2012-01-01

Coupled with evaporative light scattering detection, a high-speed counter-current chromatography (HSCCC) method was developed for preparative isolation and purification of three glycine-conjugated cholic acids, glycochenodeoxycholic acid (GCDCA), glycohyodeoxycholic acid (GHDCA) and glycohyocholic acid (GHCA) from Pulvis Fellis Suis (Pig gallbladder bile) for the first time. The separation was performed with a two-phase solvent system consisted of chloroform-methanol-water-acetic acid (65:30:...

DNA isolation protocols affect the detection limit of PCR approaches of bacteria in samples from the human gastrointestinal tract

NARCIS (Netherlands)

Zoetendal, E.G.; Ben-Amor, K.; Akkermans, A.D.L.; Abee, T.; Vos, de W.M.

2001-01-01

A major concern in molecular ecological studies is the lysis efficiency of different bacteria in a complex ecosystem. We used a PCR-based 16S rDNA approach to determine the effect of two DNA isolation protocols (i.e. the bead beating and Triton-X100 method) on the detection limit of seven

New spectrofluorimetric method for the determination of nizatidine in bulk form and in pharmaceutical preparations

Science.gov (United States)

Karasakal, Ayça; Ulu, Sevgi Tatar

2013-08-01

A simple, accurate and highly sensitive spectrofluorimetric method has been developed for determination of nizatidine in pure form and in pharmaceutical dosage forms. The method is based on the reaction between nizatidine and 1-dimethylaminonaphthalene-5-sulphonyl chloride in carbonate buffer, pH 10.5, to yield a highly fluorescent derivative peaking at 513 nm after excitation at 367 nm. Various factors affecting the fluorescence intensity of nizatidin-dansyl derivative were studied and conditions were optimized. The method was validated as per ICH guidelines. The fluorescence concentration plot was rectilinear over the range of 25-300 ng/mL. Limit of detection and limit of quantification were calculated as 11.71 and 35.73 ng/mL, respectively. The proposed method was successfully applied to pharmaceutical preparations.

A practicable detection system for genetically modified rice by SERS-barcoded nanosensors.

Science.gov (United States)

Chen, Kun; Han, Heyou; Luo, Zhihui; Wang, Yanjun; Wang, Xiuping

2012-04-15

Since the global cultivation of genetically modified crops constantly expands, it remains a high demand to establish different ways to sort food and feed that consist or contain genetically modified organisms. Surface-enhanced Raman scattering (SERS) spectroscopy is a flexible tool for biological analysis due to its excellent properties for detecting wide varieties of target biomolecules including nucleic acids. In the present study, a SERS-barcoded nanosensor was developed to detect Bacillus thuringiensis (Bt) gene-transformed rice expressing insecticidal proteins. The barcoded sensor was designed by encapsulation of gold nanoparticles with silica and conjugation of oligonucleotide strands for targeting DNA strands. The transition between the cry1A(b) and cry1A(c) fusion gene sequence was used to construct a specific SERS-based detection method with a detection limit of 0.1 pg/mL. In order to build the determination models to screen transgene, a series mixture of Bt rice and normal rice were prepared for SERS assay, and the limit of detection was 0.1% (w/w) transgenic Bt rice relative to normal rice. The sensitivity and accuracy of the SERS-based assay was comparable with real-time PCR. The SERS-barcoded analytical method would provide precise detection of transgenic rice varieties but also informative supplement to avoid false positive outcomes. Crown Copyright © 2012. Published by Elsevier B.V. All rights reserved.

ON COMPUTING UPPER LIMITS TO SOURCE INTENSITIES

International Nuclear Information System (INIS)

Kashyap, Vinay L.; Siemiginowska, Aneta; Van Dyk, David A.; Xu Jin; Connors, Alanna; Freeman, Peter E.; Zezas, Andreas

2010-01-01

A common problem in astrophysics is determining how bright a source could be and still not be detected in an observation. Despite the simplicity with which the problem can be stated, the solution involves complicated statistical issues that require careful analysis. In contrast to the more familiar confidence bound, this concept has never been formally analyzed, leading to a great variety of often ad hoc solutions. Here we formulate and describe the problem in a self-consistent manner. Detection significance is usually defined by the acceptable proportion of false positives (background fluctuations that are claimed as detections, or Type I error), and we invoke the complementary concept of false negatives (real sources that go undetected, or Type II error), based on the statistical power of a test, to compute an upper limit to the detectable source intensity. To determine the minimum intensity that a source must have for it to be detected, we first define a detection threshold and then compute the probabilities of detecting sources of various intensities at the given threshold. The intensity that corresponds to the specified Type II error probability defines that minimum intensity and is identified as the upper limit. Thus, an upper limit is a characteristic of the detection procedure rather than the strength of any particular source. It should not be confused with confidence intervals or other estimates of source intensity. This is particularly important given the large number of catalogs that are being generated from increasingly sensitive surveys. We discuss, with examples, the differences between these upper limits and confidence bounds. Both measures are useful quantities that should be reported in order to extract the most science from catalogs, though they answer different statistical questions: an upper bound describes an inference range on the source intensity, while an upper limit calibrates the detection process. We provide a recipe for computing upper

Determination of carbohydrates using pulsed amperometric detection combined with anion exchange separations

Energy Technology Data Exchange (ETDEWEB)

Edwards, W.T.; Pohl, C.A.; Rubin, R.

1987-06-01

Carbohydrates, including the monosaccharides commonly found in wood and wood pulp hydrolyzates, are separated by anion exchange chromatography using hydroxide and acetate eluants and are determined using pulsed amperometric detection. The detection method is based on oxidizing the sugars in a flow-through electrochemical cell equipped with a gold working electrode. A repeating cycle of three potentials is used: the first to oxidize the carbohydrates and measure the current generated, and two subsequent pulses to clean the electrode surface of oxidation products. The method is fast, sensitive, and requires no pre-column derivatization. It is applied to a sample of hydrolyzed wood pulp, which can be analyzed after minimal sample preparation. Detection limits are of the order of 1 mg/kg for monosaccharides in a 50 micro L injection. (Refs. 8).

Blue emitting copper nanoclusters as colorimetric and fluorescent probe for the selective detection of bilirubin

Science.gov (United States)

R. S., Aparna; J. S., Anjali Devi; John, Nebu; Abha, K.; S. S., Syamchand; George, Sony

2018-06-01

Hurdles to develop point of care diagnostic methods restrict the translation of progress in the health care sector from bench side to bedside. In this article a simple, cost effective fluorescent as well as colorimetric nanosensor was developed for the early and easy detection of hyperbilirubinemia. A stable, water soluble bovine serum albumin stabilised copper nanocluster (BSA CuNC) was used as the fluorescent probe which exhibited strong blue emission (404 nm) upon 330 nm excitation. The fluorescence of the BSA CuNC can be effectively quenched by the addition of bilirubin by the formation of copper-bilirubin complex. Meanwhile the copper-bilirubin complex resulted in an observable colour change from pale violet to green facilitating colorimetric detection. The prepared sensor displayed good selectivity and sensitivity over other co-existing molecules, and can be used for quantifying bilirubin with a detection limit down to 257 fM. Additionally, the as-prepared probe was coated on a paper strip to develop a portable paper strip sensor of bilirubin. Moreover, the method was successfully applied in real sample analysis and obtained promising result.

CA 19-9 Pancreatic Tumor Marker Fluorescence Immunosensing Detection via Immobilized Carbon Quantum Dots Conjugated Gold Nanocomposite.

Science.gov (United States)

Alarfaj, Nawal Ahmad; El-Tohamy, Maha Farouk; Oraby, Hesham Farouk

2018-04-11

The clinical detection of carbohydrate antigen 19-9 (CA 19-9), a tumor marker in biological samples, improves and facilitates the rapid screening and diagnosis of pancreatic cancer. A simple, low cost, fast, and green synthesis method to prepare a viable carbon quantum dots/gold (CQDs/Au) nanocomposite fluorescence immunosensing solution for the detection of CA 19-9 was reported. The present method is conducted by preparing glucose-derived CQDs using a microwave-assisted method. CQDs were employed as reducing and stabilizing agents for the preparation of a CQDs/Au nanocomposite. The immobilized anti-CA 19-9-labeled horseradish peroxidase enzyme (Ab-HRP) was anchored to the surface of a CQDs/Au nanocomposite by a peptide interaction between the carboxylic and amine active groups. The CA 19-9 antigen was trapped by another monoclonal antibody that was coated on the surface of microtiter wells. The formed sandwich capping antibody-antigen-antibody enzyme complex had tunable fluorescence properties that were detected under excitation and emission wavelengths of 420 and 530 nm. The increase in fluorescence intensities of the immunoassay sensing solution was proportional to the CA 19-9 antigen concentration in the linear range of 0.01-350 U mL -1 and had a lower detection limit of 0.007 U mL -1 . The proposed CQDs/Au nanocomposite immunoassay method provides a promising tool for detecting CA 19-9 in human serum.

Design of Amperometric Biosensors for the Detection of Glucose Prepared by Immobilization of Glucose Oxidase on Conducting (PolyThiophene Films

Directory of Open Access Journals (Sweden)

Maria Pilo

2018-01-01

Full Text Available Enzyme-based sensors have emerged as important analytical tools with application in diverse fields, and biosensors for the detection of glucose using the enzyme glucose oxidase have been widely investigated. In this work, the preparation of biosensors by electrochemical polymerization of (polythiophenes, namely 2,2′-bithiophene (2,2′-BT and 4,4′-bis(2-methyl-3-butyn-2-ol-2,2′-bithiophene (4,4′-bBT, followed by immobilization of glucose oxidase on the films, is described. N-cyclohexyl-N′-(2-morpholinoethylcarbodiimide metho-p-toluenesulfonate (CMC was used as a condensing agent, and p-benzoquinone (BQ was used as a redox mediator in solution. The glucose oxidase electrodes with films of 2,2′-BT and 4,4′-bBT were then tested for their ability in detecting glucose from synthetic and real samples (pear, apricot, and peach fruit juices.

[Prokaryotic expression of vp3 gene of Muscovy duck parvovirus, and its antiserum preparation for detection of virus multiplication].

Science.gov (United States)

Huang, Yu; Zhu, Yumin; Dong, Shijuan; Yu, Ruisong; Zhang, Yuanshu; Li, Zhen

2015-01-01

New epidemic broke out in recent year which was suspected to be caused by variant Muscovy duck parvovirus (MDPV). For this reason, new MDPV detection methods are needed for the new virus strains. In this study, a pair of primers were designed according to the full-length genome of MDPV strain SAAS-SHNH, which were identified in 2012, and were used to amplify the vp3 gene of MDPV by polymerase chain reaction. After being sequenced, the vp3 gene was subcloned into the prokaryotic expression vector PET28a. The recombinant plasmid was transformed into E. coli BL21 and induced with IPTG. SDS-PAGE and Western blotting analysis showed the MDPV vp3 gene was successfully expressed. After being purified by Ni2+ affinity chromatography system, the recombinant protein was used as antigen to immunize rabbits to obtain antiserum. Western blotting analysis showed that the acquired antiserum could react specifically with VP3 protein of J3D6 strain and MDPV vaccine strain. The antiserum could also be used for detection of cultured MDPV from primary duck embryo fibroblasts by immune fluorescence assay (IFA). It could be concluded that the VP3 protein and its antibody prepared in the research could be used for detection of VP3 antiserum and antigen respectively.

[Intraoperative detection of the sentinel lymph nodes in lung cancer].

Science.gov (United States)

Akopov, A L; Papayan, G V; Chistyakov, I V

2015-01-01

An analysis of the scientific data was made. It was used the literature devoted to the intraoperative visualization of the sentinel lymph nodes in patients with lung cancer. Correct detection of such lymph nodes with following pathologic investigation allowed limiting the volume of lympho-dissection in a number of patients. There is the possibility of maximal in-depth study of the sentinel lymph nodes by purposeful application of most sensible pathologic and molecular methods for detection their micrometastatic lesions. At the same time the treatment strategy and prognosis could be determined. The authors present the results of an application of dye techniques, radioactive preparation and fluorescence imaging for sentinel lymph node detection. Advantages and disadvantages of the methods are shown in the article. There are validated the prospects of technical development, study of information value of new applications and the most perspective method of fluorescence indocyanine green visualization by lymph outflow.

Positive detection of exfoliated colon cancer cells on linear stapler cartridges was associated with depth of tumor invasion and preoperative bowel preparation in colon cancer.

Science.gov (United States)

Ikehara, Kishiko; Endo, Shungo; Kumamoto, Kensuke; Hidaka, Eiji; Ishida, Fumio; Tanaka, Jun-Ichi; Kudo, Shin-Ei

2016-08-31

The aim of this study was to investigate exfoliated cancer cells (ECCs) on linear stapler cartridges used for anastomotic sites in colon cancer. We prospectively analyzed ECCs on linear stapler cartridges used for anastomosis in 100 colon cancer patients who underwent colectomy. Having completed the functional end-to-end anastomosis, the linear stapler cartridges were irrigated with saline, which was collected for cytological examination and cytological diagnoses were made by board-certified pathologists based on Papanicolaou staining. The detection rate of ECCs on the linear stapler cartridges was 20 %. Positive detection of ECCs was significantly associated with depth of tumor invasion (p = 0.012) and preoperative bowel preparation (p = 0.003). There were no marked differences between ECC-positive and ECC-negative groups in terms of the operation methods, tumor location, histopathological classification, and surgical margins. Since ECCs were identified on the cartridge of the linear stapler used for anastomosis, preoperative mechanical bowel preparation using polyethylene glycol solution and cleansing at anastomotic sites using tumoricidal agents before anastomosis may be necessary to decrease ECCs in advanced colon cancer.

Nanobody medicated immunoassay for ultrasensitive detection of cancer biomarker alpha-fetoprotein.

Science.gov (United States)

Chen, Jing; He, Qing-hua; Xu, Yang; Fu, Jin-heng; Li, Yan-ping; Tu, Zhui; Wang, Dan; Shu, Mei; Qiu, Yu-lou; Yang, Hong-wei; Liu, Yuan-yuan

2016-01-15

Immunoassay for cancer biomarkers plays an important role in cancer prevention and early diagnosis. To the development of immunoassay, the quality and stability of applied antibody is one of the key points to obtain reliability and high sensitivity for immunoassay. The main purpose of this study was to develop a novel immunoassay for ultrasensitive detection of cancer biomarker alpha-fetoprotein (AFP) based on nanobody against AFP. Two nanobodies which bind to AFP were selected from a phage display nanobody library by biopanning strategy. The prepared nanobodies are clonable, thermally stable and applied in both sandwich enzyme linked immunoassay (ELISA) and immuno-PCR assay for ultrasensitive detection of AFP. The limit detection of sandwich ELISA setup with optimized nanobodies was 0.48ng mL(-1), and the half of saturation concentration (SC50) value was 6.68±0.56ng mL(-1). These nanobodies were also used to develop an immuno-PCR assay for ultrasensitive detection of AFP, its limit detection values was 0.005ng mL(-1), and the linear range was 0.01-10,000ng mL(-1). These established immunoassays based on nanobodies were highly specific to AFP and with negligible cross reactivity with other tested caner biomarkers. Furthermore, this novel concept of nanobodies mediated immunoassay may provide potential applications in a general method for the ultrasensitive detection of various cancer biomarkers. Copyright © 2015 Elsevier B.V. All rights reserved.

Photoinduced triplet-state electron transfer of platinum porphyrin: a one-step direct method for sensing iodide with an unprecedented detection limit

KAUST Repository

Masih, Dilshad; Aly, Shawkat Mohammede; Alarousu, Erkki; Mohammed, Omar F.

2015-01-01

previously unattained detection limit of 1 × 10−12 M) and economical method for the determination of iodide. To fully understand the reaction mechanism responsible for the phosphorescence quenching process, we have employed cutting-edge time-resolved laser

Polymeric ionic liquid-based portable tip microextraction device for on-site sample preparation of water samples.

Science.gov (United States)

Chen, Lei; Pei, Junxian; Huang, Xiaojia; Lu, Min

2018-06-05

On-site sample preparation is highly desired because it avoids the transportation of large-volume samples and ensures the accuracy of the analytical results. In this work, a portable prototype of tip microextraction device (TMD) was designed and developed for on-site sample pretreatment. The assembly procedure of TMD is quite simple. Firstly, polymeric ionic liquid (PIL)-based adsorbent was in-situ prepared in a pipette tip. After that, the tip was connected with a syringe which was driven by a bidirectional motor. The flow rates in adsorption and desorption steps were controlled accurately by the motor. To evaluate the practicability of the developed device, the TMD was used to on-site sample preparation of waters and combined with high-performance liquid chromatography with diode array detection to measure trace estrogens in water samples. Under the most favorable conditions, the limits of detection (LODs, S/N = 3) for the target analytes were in the range of 4.9-22 ng/L, with good coefficients of determination. Confirmatory study well evidences that the extraction performance of TMD is comparable to that of the traditional laboratory solid-phase extraction process, but the proposed TMD is more simple and convenient. At the same time, the TMD avoids complicated sampling and transferring steps of large-volume water samples. Copyright © 2018 Elsevier B.V. All rights reserved.

[Sample preparation and bioanalysis in mass spectrometry].

Science.gov (United States)

Bourgogne, Emmanuel; Wagner, Michel

2015-01-01

The quantitative analysis of compounds of clinical interest of low molecular weight (sample preparation. Sample preparation is a crucial part of chemical/biological analysis and in a sense is considered the bottleneck of the whole analytical process. The main objectives of sample preparation are the removal of potential interferences, analyte preconcentration, and converting (if needed) the analyte into a more suitable form for detection or separation. Without chromatographic separation, endogenous compounds, co-eluted products may affect a quantitative method in mass spectrometry performance. This work focuses on three distinct parts. First, quantitative bioanalysis will be defined, different matrices and sample preparation techniques currently used in bioanalysis by mass spectrometry of/for small molecules of clinical interest in biological fluids. In a second step the goals of sample preparation will be described. Finally, in a third step, sample preparation strategies will be made either directly ("dilute and shoot") or after precipitation.

Detection of trace tetracycline in fish via synchronous fluorescence quenching with carbon quantum dots coated with molecularly imprinted silica

Science.gov (United States)

Yang, Ji; Lin, Zheng-Zhong; Nur, A.-Zha; Lu, Yan; Wu, Ming-Hui; Zeng, Jun; Chen, Xiao-Mei; Huang, Zhi-Yong

2018-02-01

A novel fluorescence-based sensor combining synchronous fluorescence spectroscopy (SFS) with molecularly imprinted polymers (MIPs) was fabricated with reverse microemulsion method. Tetracycline (TC), (3-aminopropyl) triethoxysilane (APTES), tetraethyl orthosilicate (TEOS) and carbon quantum dots (CDs) were used as template, functional monomer, cross-linker and signal sources respectively in the probe preparation. A synchronous fluorescence emission (λem) at 355 nm was observed for the prepared MIP-coated CDs (MIP@CDs) particles when the wavelength interval (Δλ) was set as 70 nm, and the synchronous fluorescence intensity could be rapidly and efficiently quenched by TC based on inner filter effect (IFE). The quenching efficiencies of synchronous fluorescence intensity was linearly fitted with tetracycline (TC) concentrations ranging from 0.1 to 50 μmol L- 1 with a detection limit (DL) of 9 nmol L- 1 (3σ, n = 9). The MIP@CDs was used as a probe to detect TC in fish samples with the recoveries ranging from 98.4% to 103.1% and the relative standard deviation less than 6.0%. The results illustrated that the as-prepared MIP@CDs could be applied to the detection of trace TC in fish samples with rapidity, high sensitivity and accuracy.

Detection limits of intraoperative near infrared imaging for tumor resection.

Science.gov (United States)

Thurber, Greg M; Figueiredo, Jose-Luiz; Weissleder, Ralph

2010-12-01

The application of fluorescent molecular imaging to surgical oncology is a developing field with the potential to reduce morbidity and mortality. However, the detection thresholds and other requirements for successful intervention remain poorly understood. Here we modeled and experimentally validated depth and size of detection of tumor deposits, trade-offs in coverage and resolution of areas of interest, and required pharmacokinetics of probes based on differing levels of tumor target presentation. Three orthotopic tumor models were imaged by widefield epifluorescence and confocal microscopes, and the experimental results were compared with pharmacokinetic models and light scattering simulations to determine detection thresholds. Widefield epifluorescence imaging can provide sufficient contrast to visualize tumor margins and detect tumor deposits 3-5  mm deep based on labeled monoclonal antibodies at low objective magnification. At higher magnification, surface tumor deposits at cellular resolution are detectable at TBR ratios achieved with highly expressed antigens. A widefield illumination system with the capability for macroscopic surveying and microscopic imaging provides the greatest utility for varying surgical goals. These results have implications for system and agent designs, which ultimately should aid complete resection in most surgical beds and provide real-time feedback to obtain clean margins. © 2010 Wiley-Liss, Inc.

Simple, rapid and sensitive detection of Orientia tsutsugamushi by loop-isothermal DNA amplification.

Science.gov (United States)

Paris, Daniel H; Blacksell, Stuart D; Newton, Paul N; Day, Nicholas P J

2008-12-01

We present a loop-mediated isothermal PCR assay (LAMP) targeting the groEL gene, which encodes the 60kDa heat shock protein of Orientia tsutsugamushi. Evaluation included testing of 63 samples of contemporary in vitro isolates, buffy coats and whole blood samples from patients with fever. Detection limits for LAMP were assessed by serial dilutions and quantitation by real-time PCR assay based on the same target gene: three copies/microl for linearized plasmids, 26 copies/microl for VERO cell culture isolates, 14 copies/microl for full blood samples and 41 copies/microl for clinical buffy coats. Based on a limited sample number, the LAMP assay is comparable in sensitivity with conventional nested PCR (56kDa gene), with limits of detection well below the range of known admission bacterial loads of patients with scrub typhus. This inexpensive method requires no sophisticated equipment or sample preparation, and may prove useful as a diagnostic assay in financially poor settings; however, it requires further prospective validation in the field setting.

[THE INFLUENCE OF THE PREPARATION PRETREATMENT ON IN SITU DETECTION OF 5-METHYLCYTOSINE IN METAPHASE CHROMOSOMES AND IN INTERPHASE NUCLEI].

Science.gov (United States)

Grudinina, N A; Sasina, L K; Noniashvili, E M; Neronova, E G; Pavlinova, L I; Suchkova, I O; Sofronov, G A; Patkin, E L

2015-01-01

Qualitative and quantitate analysis of DNA methylation in situ at the level of cells, chromosomes and chromosomal domains is extremely important for the diagnosis and treatment of various diseases, the study of ageing and the consequences of environmental impacts. An important question arises, whether the revealed in situ methylation pattern reflects DNA methylation per se and (or) availability of the DNA for antibodies, which in turn depends on the peculiarities of chromatin structure and chromosome condensation. These events can lead to an incorrect evaluation of the actual pattern of DNA methylation. To avoid this shortcoming as far as possible, we have modified the most widely used method of revealing 5-methylcytosine in situ with monoclonal antibodies. Here we have shown that the detection of DNA methylation staining of chromosomes including C-heterochromatin, chromosomal arms and sister chromatids is drastically dependent on pretreatment of chromosomal preparations for immunocytochemical study using fluorescent antibodies. Using undifferentiated stem cells of mouse embryonal carcinoma line F9, it has been found that change in preparations storage results in a sharp fluorescence decrease up to complete disappearance of the signal in centromeric heterochromatin. With the help of the method described in the work, we have first revealed the asymmetry of sister chromatids methylation in metaphase chromosomes of F9 cell and lymphocytes of human periphery blood. This may lead to asymmetry of transcriptional signature of daughter cells after division. The proposed here modification of 5-methylcytosine detection in situ provides a more complete characterization of methylation of chromosomes and chromosomal domains, compared to previously published methods.

Detection of Salmonella enterica in meat in less than 5 hours by a low-cost and non-complex sample preparation method

DEFF Research Database (Denmark)

Fachmann, Mette Sofie Rousing; Löfström, Charlotta; Hoorfar, Jeffrey

2017-01-01

peptone water, and a real-time PCR compatible sample preparation method, based on filtration, centrifugation, and enzymatic digestion, followed by fast cycling real-time PCR detection. The method was validated in an un-paired, comparative study against the Nordic Committee on Food Analysis (NMKL......, and help contribute to improved food safety. While the cost of analysis and hands-on time of the presented rapid method were comparable to reference culture methods, the fast product release by this method can provide the meat industry with a competitive advantage. Not only will the abattoirs save costs......Salmonella is recognised as one of the most important foodborne bacteria, and has a wide health and socioeconomical impact worldwide. Fresh pork meat is one of the main sources of Salmonella and efficient and fast methods for detection are therefore necessary. Current methods for Salmonella...

10 CFR 51.49 - Environmental report-limited work authorization.

Science.gov (United States)

2010-01-01

... reduce environmental impacts. (b) Phased application for limited work authorization and construction... where an environmental impact statement was prepared, but the facility construction was not completed... Commission has previously prepared an environmental impact statement for the construction and operation of a...

Gas chromatography with flame photometric detection of 31 organophosphorus pesticide residues in Alpinia oxyphylla dried fruits.

Science.gov (United States)

Zhao, Xiangsheng; Kong, Weijun; Wei, Jianhe; Yang, Meihua

2014-11-01

A simple, rapid and effective gas chromatography-flame photometric detection method was established for simultaneous multi-component determination of 31 organophosphorus pesticides (OPPs) residues in Alpinia oxyphylla, which is widely consumed as a traditional medicine and food in China. Sample preparation was completed in a single step without any clean-up procedure. All pesticides expressed good linear relationships between 0.004 and 1.0 μg/mL with correlation coefficients higher than 0.9973. The method gave satisfactory recoveries for most pesticides. The limits of detection varied from 1 to 10 ng/mL, and the limits of quantification (LOQs) were between 4 and 30 ng/mL. The proposed method was successfully applied to 55 commercial samples purchased from five different areas. Five pesticide residues were detected in four (7.27%) samples. The positive samples were confirmed by gas chromatography with tandem mass spectrometry (GC-MS/MS). Copyright © 2014 Elsevier Ltd. All rights reserved.

Sensitivities and detection limits of X-ray fluorescence analysis with a 10 mCi241Am source

International Nuclear Information System (INIS)

Wundt, K.; Janghorbani, M.; Starke, K.

1976-01-01

Seven trace elements ranging from chromium to barium were preconcentrated on Amberlite IR-120 cation exchange paper and determined in an energy dispersive X-ray fluorescence system using a 10 mCi 241 Am source. Sensitivities were experimentally determined and checked with theoretically calculated values. The detection limits are compared with elemental levels present in typical surface waters and those allowed in drinking water. Appropriate conclusions as to feasibility of such a system for environmental monitoring are drawn. (orig.) [de

The Use and Abuse of Limits of Detection in Environmental Analytical Chemistry

Directory of Open Access Journals (Sweden)

Richard J. C. Brown

2008-01-01

Full Text Available The limit of detection (LoD serves as an important method performance measure that is useful for the comparison of measurement techniques and the assessment of likely signal to noise performance, especially in environmental analytical chemistry. However, the LoD is only truly related to the precision characteristics of the analytical instrument employed for the analysis and the content of analyte in the blank sample. This article discusses how other criteria, such as sampling volume, can serve to distort the quoted LoD artificially and make comparison between various analytical methods inequitable. In order to compare LoDs between methods properly, it is necessary to state clearly all of the input parameters relating to the measurements that have been used in the calculation of the LoD. Additionally, the article discusses that the use of LoDs in contexts other than the comparison of the attributes of analytical methods, in particular when reporting analytical results, may be confusing, less informative than quoting the actual result with an accompanying statement of uncertainty, and may act to bias descriptive statistics.

Variation in the limit-of-detection of the ProSpecT Campylobacter microplate enzyme immunoassay in stools spiked with emerging Campylobacter species.

Science.gov (United States)

Bojanić, Krunoslav; Midwinter, Anne Camilla; Marshall, Jonathan Craig; Rogers, Lynn Elizabeth; Biggs, Patrick Jon; Acke, Els

2016-08-01

Campylobacter enteritis in humans is primarily associated with C. jejuni/coli infection. The impact of other Campylobacter spp. is likely to be underestimated due to the bias of culture methods towards Campylobacter jejuni/coli diagnosis. Stool antigen tests are becoming increasingly popular and appear generally less species-specific. A review of independent studies of the ProSpecT® Campylobacter Microplate enzyme immunoassay (EIA) developed for C. jejuni/coli showed comparable diagnostic results to culture methods but the examination of non-jejuni/coli Campylobacter spp. was limited and the limit-of-detection (LOD), where reported, varied between studies. This study investigated LOD of EIA for Campylobacter upsaliensis, Campylobacter hyointestinalis and Campylobacter helveticus spiked in human stools. Multiple stools and Campylobacter isolates were used in three different concentrations (10(4)-10(9)CFU/ml) to reflect sample heterogeneity. All Campylobacter species evaluated were detectable by EIA. Multivariate analysis showed LOD varied between Campylobacter spp. and faecal consistency as fixed effects and individual faecal samples as random effects. EIA showed excellent performance in replicate testing for both within and between batches of reagents, in agreement between visual and spectrophotometric reading of results, and returned no discordance between the bacterial concentrations within independent dilution test runs (positive results with lower but not higher concentrations). This study shows how limitations in experimental procedures lead to an overestimation of consistency and uniformity of LOD for EIA that may not hold under routine use in diagnostic laboratories. Benefits and limitations for clinical practice and the influence on estimates of performance characteristics from detection of multiple Campylobacter spp. by EIA are discussed. Copyright © 2016 Elsevier B.V. All rights reserved.

Electrochemical Detecting Lung Cancer-Associated Antigen Based on Graphene-Gold Nanocomposite

Directory of Open Access Journals (Sweden)

Zheng Wei

2017-03-01

Full Text Available Using a Au nanoparticle/reduced graphene oxide composite (AuNP-RGO, a signal-enhanced electrochemical immunosensor without label was created to detect neuron-specific enolase (NSE. Furthermore, an environmentally-friendly method was developed to prepare AuNP-RGO by employing chitosan (CS, which served as reducing and stabilizing agent. We showed that the sensitivity of the immunosensor designed in this report was remarkably enhanced because of the numerous active sites in the sensor provided by the AuNP-RGO nanostructure. For the quantification of NSE, the immunosensor exhibited a positive linear relationship with the concentration in the range of 0.1 to 2000 ng/mL, where the limit of the detection was 0.05 ng/mL.

Use of an Electronic Tongue to Detect Geosmin in Distilled Water

Science.gov (United States)

Braga, Guilherme S.; Paterno, Leonardo G.; Fonseca, Fernando J.

2011-11-01

An electronic tongue (ET) system consisting of conducting polymer sensors was employed to detect geosmin (GSM) in distilled water. GSM is a tainting compound and known to cause undesirable tastes and odors in water and aquaculture farming. Diluted solutions of GSM were prepared in distilled water at different concentrations. The electrical response (capacitance) of the sensors was analyzed using principal analysis component (PCA). The data obtained were separated into different clusters indicating a good sensibility of the ET system to this compound in distilled water. The ET showed signal saturation for concentrations higher than 300 ng.L-1. So far, the detection limit of our system is 25 ng.L-1. Nevertheless, close grouping between repeated tests indicated that the ET system response is reproducible.

Nafion covered core–shell structured Fe{sub 3}O{sub 4}@graphene nanospheres modified electrode for highly selective detection of dopamine

Energy Technology Data Exchange (ETDEWEB)

Zhang, Wuxiang; Zheng, Jianzhong; Shi, Jiangu; Lin, Zhongqiu; Huang, Qitong; Zhang, Hanqiang; Wei, Chan [College of Chemistry and Environment, Minnan Normal University, Zhangzhou 363000 (China); Chen, Jianhua [College of Chemistry and Environment, Minnan Normal University, Zhangzhou 363000 (China); Fujian Province University Key Laboratory of Analytical Science, Minnan Normal University, Zhangzhou 363000 (China); Hu, Shirong, E-mail: Hushirong6666@163.com [College of Chemistry and Environment, Minnan Normal University, Zhangzhou 363000 (China); Fujian Province University Key Laboratory of Analytical Science, Minnan Normal University, Zhangzhou 363000 (China); School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); Hao, Aiyou [School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China)

2015-01-01

Graphical abstract: Schematic illustration of the reaction mechanism of Fe{sub 3}O{sub 4}@GNs/Nafion with DA. - Highlights: • The sensor based on Fe{sub 3}O{sub 4}@graphene nanospheres was prepared for the first time. • The biosensor shows a wide linear range and a lower detection limit of 0.007 μM. • This method was successfully applied to detection of DA in real samples. - Abstract: Nafion covered core–shell structured Fe{sub 3}O{sub 4}@graphene nanospheres (GNs) modified glassy carbon electrode (GCE) was successfully prepared and used for selective detection dopamine. Firstly, the characterizations of hydro-thermal synthesized Fe{sub 3}O{sub 4}@GNs were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. Then Fe{sub 3}O{sub 4}@GNs/Nafion modified electrode exhibited excellent electrocatalytic activity toward the oxidations of dopamine (DA). The interference test showed that the coexisted ascorbic acid (AA) and uric acid (UA) had no electrochemical interference toward DA. Under the optimum conditions, the broad linear relationship was obtained in the experimental concentration from 0.020 μM to 130.0 μM with the detection limit (S/N = 3) of 0.007 μM. Furthermore, the core–shell structured Fe{sub 3}O{sub 4}@GNs/Nafion/GCE was applied to the determination of DA in real samples and satisfactory results were got, which could provide a promising platform to develop excellent biosensor for detecting DA.

Lower limits of spin detection efficiency for two-parameter two-qubit (TPTQ) states with non-ideal ferromagnetic detectors

Science.gov (United States)

Majd, Nayereh; Ghasemi, Zahra

2016-10-01

We have investigated a TPTQ state as an input state of a non-ideal ferromagnetic detectors. Minimal spin polarization required to demonstrate spin entanglement according to entanglement witness and CHSH inequality with respect to (w.r.t.) their two free parameters have been found, and we have numerically shown that the entanglement witness is less stringent than the direct tests of Bell's inequality in the form of CHSH in the entangled limits of its free parameters. In addition, the lower limits of spin detection efficiency fulfilling secure cryptographic key against eavesdropping have been derived. Finally, we have considered TPTQ state as an output of spin decoherence channel and the region of ballistic transmission time w.r.t. spin relaxation time and spin dephasing time has been found.

Potentiometric chemical sensors for the detection of paralytic shellfish toxins.

Science.gov (United States)

Ferreira, Nádia S; Cruz, Marco G N; Gomes, Maria Teresa S R; Rudnitskaya, Alisa

2018-05-01

Potentiometric chemical sensors for the detection of paralytic shellfish toxins have been developed. Four toxins typically encountered in Portuguese waters, namely saxitoxin, decarbamoyl saxitoxin, gonyautoxin GTX5 and C1&C2, were selected for the study. A series of miniaturized sensors with solid inner contact and plasticized polyvinylchloride membranes containing ionophores, nine compositions in total, were prepared and their characteristics evaluated. Sensors displayed cross-sensitivity to four studied toxins, i.e. response to several toxins together with low selectivity. High selectivity towards paralytic shellfish toxins was observed in the presence of inorganic cations with selectivity coefficients ranging from 0.04 to 0.001 for Na + and K + and 3.6*10 -4 to 3.4*10 -5 for Ca 2+ . Detection limits were in the range from 0.25 to 0.9 μmolL -1 for saxitoxin and decarbamoyl saxitoxin, and from 0.08 to 1.8 μmolL -1 for GTX5 and C1&C2, which allows toxin detection at the concentration levels corresponding to the legal limits. Characteristics of the developed sensors allow their use in the electronic tongue multisensor system for simultaneous quantification of paralytic shellfish toxins. Copyright © 2018 Elsevier B.V. All rights reserved.

Comparison of Laboratory-Developed and Commercial Monoclonal Antibody-Based Sandwich Enzyme-Linked Immunosorbent Assays for Almond (Prunus dulcis) Detection and Quantification.

Science.gov (United States)

Liu, Changqi; Chhabra, Guneet S; Zhao, Jing; Zaffran, Valerie D; Gupta, Sahil; Roux, Kenneth H; Gradziel, Thomas M; Sathe, Shridhar K

2017-10-01

A commercially available monoclonal antibody (mAb)-based direct sandwich enzyme-linked immunosorbent assay (ELISA) kit (BioFront Technologies, Tallahassee, Fla., U.S.A.) was compared with an in-house developed mAb 4C10-based ELISA for almond detection. The assays were comparable in sensitivity (limit of detection almond, limit of quantification almond), specificity (no cross-reactivity with 156 tested foods at a concentration of 100000 ppm whole sample), and reproducibility (intra- and interassay variability almond seeds subjected to autoclaving, blanching, frying, microwaving, and dry roasting. The almond recovery ranges for spiked food matrices were 84.3% to 124.6% for 4C10 ELISA and 81.2% to 127.4% for MonoTrace ELISA. The almond recovery ranges for commercial and laboratory prepared foods with declared/known almond amount were 30.9% to 161.2% for 4C10 ELISA and 38.1% to 207.6% for MonoTrace ELISA. Neither assay registered any false-positive or negative results among the tested commercial and laboratory prepared samples. Ability to detect and quantify trace amounts of almonds is important for improving safety of almond sensitive consumers. Two monoclonal antibody-based ELISAs were compared for almond detection. The information is useful to food industry, regulatory agencies, scientific community, and almond consumers. © 2017 Institute of Food Technologists®.

Microbial viability in preparations packaged for single use.

Science.gov (United States)

Obayashi, Akiko; Oie, Shigeharu; Kamiya, Akira

2003-05-01

We evaluated microbial viability in preparations packaged for single use only which mandate that residual solution be discarded such as albumin and globulin preparations as blood products, preparations containing albumin (such as urokinase and interferon), fat emulsions, and a preparation containing fat emulsions (propofol). In most preparations, Serratia marcescens and Burkholderia cepacia proliferated rapidly at 30 degrees C. However, in globulin preparations containing 1-2.25% glycine to prevent protein degradation (Gamma-Venin P, Venilon-I, Globulin Injection, and Ahlbulin), no growth of S. marcescens and B. cepacia was detected over 24 h at 30 degrees C. For globulin preparations containing 1-2.25% glycine, the injunction to "Discard residual solution after the package has been used" in the package inserts can be revised to "It is possible to use residual solution within 24 h after the package has been used with storage in a cool place."

Indigenous development of automated metallographic sample preparation system

International Nuclear Information System (INIS)

Kulkarni, A.P.; Pandit, K.M.; Deshmukh, A.G.; Sahoo, K.C.

2005-01-01

Surface preparation of specimens for Metallographic studies on irradiated material involves a lot of remote handling of radioactive material by skilled manpower. These are laborious and man-rem intensive activities and put limitations on number of samples that can be prepared for the metallographic studies. To overcome these limitations, automated systems have been developed for surface preparation of specimens in PIE division. The system includes (i) Grinding and polishing stations (ii) Water jet cleaning station (iii) Ultrasonic cleaning stations (iv) Drying station (v) Sample loading and unloading station (vi) Dispenser for slurries and diluents and (vii) Automated head for movement of the sample holder disc from one station to other. System facilities the operator for programming/changing sequence of the sample preparations including remote changing of grinding/polishing discs from the stations. Two such systems have been installed and commissioned in Hot Cell for PIE Division. These are being used for preparation of irradiated samples from nuclear fuels and structural components. This development has increased the throughput of metallography work and savings in terms of (man-severts) radiation exposure to operators. This presentation will provide details of the challenges in undertaking this developmental work. (author)

Mesoporous structured MIPs@CDs fluorescence sensor for highly sensitive detection of TNT.

Science.gov (United States)

Xu, Shoufang; Lu, Hongzhi

2016-11-15

A facile strategy was developed to prepare mesoporous structured molecularly imprinted polymers capped carbon dots (M-MIPs@CDs) fluorescence sensor for highly sensitive and selective determination of TNT. The strategy using amino-CDs directly as "functional monomer" for imprinting simplify the imprinting process and provide well recognition sites accessibility. The as-prepared M-MIPs@CDs sensor, using periodic mesoporous silica as imprinting matrix, and amino-CDs directly as "functional monomer", exhibited excellent selectivity and sensitivity toward TNT with detection limit of 17nM. The recycling process was sustainable for 10 times without obvious efficiency decrease. The feasibility of the developed method in real samples was successfully evaluated through the analysis of TNT in soil and water samples with satisfactory recoveries of 88.6-95.7%. The method proposed in this work was proved to be a convenient and practical way to prepare high sensitive and selective fluorescence MIPs@CDs sensors. Copyright © 2016 Elsevier B.V. All rights reserved.

Determination of limits for smallest detectable and largest subcritical leakage cracks in piping systems

International Nuclear Information System (INIS)

Bieselt, R.; Wolf, M.

1995-01-01

Nuclear power plant piping systems - those still in their original as-built condition as well as upgraded designs - are subject to safety analysis. In order to limit the consequences of postulated piping failures, the basic safety concept incorporating rupture preclusion criteria is applied to specific high-energy piping systems. Leak-before-break analyses are also conducted within the framework of this concept. These analyses serve to determine the potential consequences of jet and reaction forces due to maximum subcritical leakage cracks while also establishing the minimum crack sizes that would be reliably detectable by the leakage rates resulting from these cracks. The boundary conditions for these analyses are not clearly defined. Using various examples as a basis, this paper presents and discusses how the leak-before-break concept can be applied. (orig.)

STRUCTURAL ANALYSIS OF CONDITIONAL PREPARATION IN JUDO

Directory of Open Access Journals (Sweden)

Slavko Obadov

2006-06-01

Full Text Available Conditional preparation is a constituent part of overall sports preparation. Conditional training might be defined as a process of improvement of a sportsman’s functional and motor abilities, morphological characteristics, health, as well as the required motor knowledge. Conditional preparation can be might be classified as: general, basic and situational conditional preparation. Programs of the conditional training might be classified as: developing, resuming, recovering, preventive and recovering ones. High level of the general physical preparation enables maximum demonstration of the physical abilities of a sportsman during the stage of improvement of the specific motor abilities. Good general preparation of a sportsman enables him to push beyond his functional limits in order to cope with heavy loads easier, which subsequently enables him to achieve top performance level. Basic conditional preparation assumes the development of the most important judo abilities. Specific conditional preparation is related directly to the execution of different structural elements under the conditional requirements. Situational conditional preparation enables integration of the tactical and conditional training.

Development of colloidal gold immunochromatographic strips for detection of Riemerella anatipestifer.

Directory of Open Access Journals (Sweden)

Wanwan Hou

Full Text Available Riemerella anatipestifer is one of the most important bacterial pathogen of ducks and causes a contagious septicemia. R. anatipestifer infection causes serositis syndromes similar to other bacterial infections in ducks, including infection by Escherichia coli, Salmonella enterica and Pasteurella multocida. Clinically differentiating R. anatipestifer infections from other bacterial pathogen infections is usually difficult. In this study, MAb 1G2F10, a monoclonal antibody against R. anatipestifer GroEL, was used to develop a colloidal gold immunochromatographic strip. Colloidal gold particles were prepared by chemical synthesis to an average diameter of 20 ± 5.26 nm by transmission electron microscope imaging. MAb 1G2F10 was conjugated to colloidal gold particles and the formation of antibody-colloidal gold conjugates was monitored by UV/Vis spectroscopy. Immunochromatographic strips were assembled in regular sequence through different accessories sticked on PVC plate. Strips specifically detected R. anatipestifer within 10 min, but did not detect E. coli, S. enterica and P. multocida. The detection limit for R. anatipestifer was 1 × 10(6 colony forming units, which was 500 times higher than a conventional agglutination test. Accuracy was 100% match to multiplex PCR. Assay stability and reproducibility were excellent after storage at 4°C for 6 months. The immunochromatographic strips prepared in this study offer a specific, sensitive, and rapid detection method for R. anatipestifer, which is of great importance for the prevention and control of R. anatipestifer infections.

Quantum Limits of Space-to-Ground Optical Communications

Science.gov (United States)

Hemmati, H.; Dolinar, S.

2012-01-01

For a pure loss channel, the ultimate capacity can be achieved with classical coherent states (i.e., ideal laser light): (1) Capacity-achieving receiver (measurement) is yet to be determined. (2) Heterodyne detection approaches the ultimate capacity at high mean photon numbers. (3) Photon-counting approaches the ultimate capacity at low mean photon numbers. A number of current technology limits drive the achievable performance of free-space communication links. Approaching fundamental limits in the bandwidth-limited regime: (1) Heterodyne detection with high-order coherent-state modulation approaches ultimate limits. SOA improvements to laser phase noise, adaptive optics systems for atmospheric transmission would help. (2) High-order intensity modulation and photon-counting can approach heterodyne detection within approximately a factor of 2. This may have advantages over coherent detection in the presence of turbulence. Approaching fundamental limits in the photon-limited regime (1) Low-duty cycle binary coherent-state modulation (OOK, PPM) approaches ultimate limits. SOA improvements to laser extinction ratio, receiver dark noise, jitter, and blocking would help. (2) In some link geometries (near field links) number-state transmission could improve over coherent-state transmission

Trace elements detection in whole food samples by Neutron Activation Analysis, k0-method

International Nuclear Information System (INIS)

Sathler, Márcia Maia; Menezes, Maria Ângela de Barros Correia; Salles, Paula Maria Borges de

2017-01-01

Inorganic elements, from natural and anthropogenic sources are present in foods in different concentrations. With the increase in anthropogenic activities, there was also a considerable increase in the emission of these elements in the environment, leading to the need of monitoring the elemental composition of foods available for consumption. Numerous techniques have been used to detect inorganic elements in biological and environmental matrices, always aiming at reaching lower detection limits in order to evaluate the trace element content in the sample. Neutron activation analysis (INAA), applying the k 0 -method, produces accurate and precise results without the need of chemical preparation of the samples – that could cause their contamination. This study evaluated the presence of inorganic elements in whole foods samples, mainly elements on trace levels. For this purpose, seven samples of different types of whole foods were irradiated in the TRIGA MARK I IPR-R1 research reactor - located at CDTN/CNEN, in Belo Horizonte, MG. It was possible to detect twenty two elements above the limit of detection in, at least, one of the samples analyzed. This study reaffirms the INAA, k 0 - method, as a safe and efficient technique for detecting trace elements in food samples. (author)

Coincidence detection of single-photon responses in the inner retina at the sensitivity limit of vision.

Science.gov (United States)

Ala-Laurila, Petri; Rieke, Fred

2014-12-15

Vision in starlight relies on our ability to detect single absorbed photons. Indeed, the sensitivity of dark-adapted vision approaches limits set by the quantal nature of light. This sensitivity requires neural mechanisms that selectively transmit quantal responses and suppress noise. Such mechanisms face an inevitable tradeoff because signal and noise cannot be perfectly separated, and rejecting noise also means rejecting signal. We report measurements of single-photon responses in the output signals of the primate retina. We find that visual signals arising from a few absorbed photons are read out fundamentally differently by primate On and Off parasol ganglion cells, key retinal output neurons. Off parasol cells respond linearly to near-threshold flashes, retaining sensitivity to each absorbed photon but maintaining a high level of noise. On parasol cells respond nonlinearly due to thresholding of their excitatory synaptic inputs. This nonlinearity reduces neural noise but also limits information about single-photon absorptions. The long-standing idea that information about each photon absorption is available for behavior at the sensitivity limit of vision is not universally true across retinal outputs. More generally, our work shows how a neural circuit balances the competing needs for sensitivity and noise rejection. Copyright © 2014 Elsevier Ltd. All rights reserved.

100 nm scale low-noise sensors based on aligned carbon nanotube networks: overcoming the fundamental limitation of network-based sensors

Science.gov (United States)

Lee, Minbaek; Lee, Joohyung; Kim, Tae Hyun; Lee, Hyungwoo; Lee, Byung Yang; Park, June; Jhon, Young Min; Seong, Maeng-Je; Hong, Seunghun

2010-02-01

Nanoscale sensors based on single-walled carbon nanotube (SWNT) networks have been considered impractical due to several fundamental limitations such as a poor sensitivity and small signal-to-noise ratio. Herein, we present a strategy to overcome these fundamental problems and build highly-sensitive low-noise nanoscale sensors simply by controlling the structure of the SWNT networks. In this strategy, we prepared nanoscale width channels based on aligned SWNT networks using a directed assembly strategy. Significantly, the aligned network-based sensors with narrower channels exhibited even better signal-to-noise ratio than those with wider channels, which is opposite to conventional random network-based sensors. As a proof of concept, we demonstrated 100 nm scale low-noise sensors to detect mercury ions with the detection limit of ~1 pM, which is superior to any state-of-the-art portable detection system and is below the allowable limit of mercury ions in drinking water set by most government environmental protection agencies. This is the first demonstration of 100 nm scale low-noise sensors based on SWNT networks. Considering the increased interests in high-density sensor arrays for healthcare and environmental protection, our strategy should have a significant impact on various industrial applications.

100 nm scale low-noise sensors based on aligned carbon nanotube networks: overcoming the fundamental limitation of network-based sensors

Energy Technology Data Exchange (ETDEWEB)

Lee, Minbaek; Lee, Joohyung; Kim, Tae Hyun; Lee, Hyungwoo; Lee, Byung Yang; Hong, Seunghun [Department of Physics and Astronomy, Seoul National University, Shilim-Dong, Kwanak-Gu, Seoul 151-742 (Korea, Republic of); Park, June; Seong, Maeng-Je [Department of Physics, Chung-Ang University, Heukseok-Dong, Dongjak-Gu, Seoul 156-756 (Korea, Republic of); Jhon, Young Min, E-mail: mseong@cau.ac.kr, E-mail: shong@phya.snu.ac.kr [Korea Institute of Science and Technology, Hawolgok-Dong, Seongbuk-Gu, Seoul 136-791 (Korea, Republic of)

2010-02-05

Nanoscale sensors based on single-walled carbon nanotube (SWNT) networks have been considered impractical due to several fundamental limitations such as a poor sensitivity and small signal-to-noise ratio. Herein, we present a strategy to overcome these fundamental problems and build highly-sensitive low-noise nanoscale sensors simply by controlling the structure of the SWNT networks. In this strategy, we prepared nanoscale width channels based on aligned SWNT networks using a directed assembly strategy. Significantly, the aligned network-based sensors with narrower channels exhibited even better signal-to-noise ratio than those with wider channels, which is opposite to conventional random network-based sensors. As a proof of concept, we demonstrated 100 nm scale low-noise sensors to detect mercury ions with the detection limit of {approx}1 pM, which is superior to any state-of-the-art portable detection system and is below the allowable limit of mercury ions in drinking water set by most government environmental protection agencies. This is the first demonstration of 100 nm scale low-noise sensors based on SWNT networks. Considering the increased interests in high-density sensor arrays for healthcare and environmental protection, our strategy should have a significant impact on various industrial applications.

100 nm scale low-noise sensors based on aligned carbon nanotube networks: overcoming the fundamental limitation of network-based sensors

International Nuclear Information System (INIS)

Lee, Minbaek; Lee, Joohyung; Kim, Tae Hyun; Lee, Hyungwoo; Lee, Byung Yang; Hong, Seunghun; Park, June; Seong, Maeng-Je; Jhon, Young Min

2010-01-01

Nanoscale sensors based on single-walled carbon nanotube (SWNT) networks have been considered impractical due to several fundamental limitations such as a poor sensitivity and small signal-to-noise ratio. Herein, we present a strategy to overcome these fundamental problems and build highly-sensitive low-noise nanoscale sensors simply by controlling the structure of the SWNT networks. In this strategy, we prepared nanoscale width channels based on aligned SWNT networks using a directed assembly strategy. Significantly, the aligned network-based sensors with narrower channels exhibited even better signal-to-noise ratio than those with wider channels, which is opposite to conventional random network-based sensors. As a proof of concept, we demonstrated 100 nm scale low-noise sensors to detect mercury ions with the detection limit of ∼1 pM, which is superior to any state-of-the-art portable detection system and is below the allowable limit of mercury ions in drinking water set by most government environmental protection agencies. This is the first demonstration of 100 nm scale low-noise sensors based on SWNT networks. Considering the increased interests in high-density sensor arrays for healthcare and environmental protection, our strategy should have a significant impact on various industrial applications.

Preparation of Au Nanoclusters-Modified Polylactic Acid Fiber with Bright Red Fluorescence and its Use as Sensing Probe.

Science.gov (United States)

Zhu, Wenli; Li, Huili; Wan, Ajun; Liu, Lanbo

2017-01-01

In present work, the Au nanoclusters-modified polylactic acid fiber (PLA-Au NCs) with bright red fluorescence were fabricated by the encapsulation of Au nanoclusters (Au NCs) in the PLA fiber treated with H 2 O 2 . The Au 25 nanoclusters stabilized by bovine serum albumin (BSA-Au NCs) were prepared via an improved "green" synthetic routine. With pretreatment of the PLA fiber in H 2 O 2 concentration of 12 and 18 %, the as-prepared PLA-Au NCs exhibited brighter red emission with a strong peak centered at ~640 nm than BSA-Au NCs. The fluorescence can be quenched by nitric oxide (NO). A good linear relationship between the relative fluorescence quenching intensity of the as-prepared PLA-Au NCs and the concentration of NO can be obtained in the range of 0.0732 to 0.7320 mM, and the detection limit was 0.0070 mM.

Gold nanorods-silicone hybrid material films and their optical limiting property

Science.gov (United States)

Li, Chunfang; Qi, Yanhai; Hao, Xiongwen; Peng, Xue; Li, Dongxiang

2015-10-01

As a kind of new optical limiting materials, gold nanoparticles have optical limiting property owing to their optical nonlinearities induced by surface plasmon resonance (SPR). Gold nanorods (GNRs) possess transversal SPR absorption and tunable longitudinal SPR absorption in the visible and near-infrared region, so they can be used as potential optical limiting materials against tunable laser pulses. In this letter, GNRs were prepared using seed-mediated growth method and surface-modified by silica coating to obtain good dispersion in polydimethylsiloxane prepolymers. Then the silicone rubber films doped with GNRs were prepared after vulcanization, whose optical limiting property and optical nonlinearity were investigated. The silicone rubber samples doped with more GNRs were found to exhibit better optical limiting performance.

Biosensor-based microRNA detection: techniques, design, performance, and challenges.

Science.gov (United States)

Johnson, Blake N; Mutharasan, Raj

2014-04-07

The current state of biosensor-based techniques for amplification-free microRNA (miRNA) detection is critically reviewed. Comparison with non-sensor and amplification-based molecular techniques (MTs), such as polymerase-based methods, is made in terms of transduction mechanism, associated protocol, and sensitivity. Challenges associated with miRNA hybridization thermodynamics which affect assay selectivity and amplification bias are briefly discussed. Electrochemical, electromechanical, and optical classes of miRNA biosensors are reviewed in terms of transduction mechanism, limit of detection (LOD), time-to-results (TTR), multiplexing potential, and measurement robustness. Current trends suggest that biosensor-based techniques (BTs) for miRNA assay will complement MTs due to the advantages of amplification-free detection, LOD being femtomolar (fM)-attomolar (aM), short TTR, multiplexing capability, and minimal sample preparation requirement. Areas of future importance in miRNA BT development are presented which include focus on achieving high measurement confidence and multiplexing capabilities.

LAMP-based group specific detection of aflatoxin producers within Aspergillus section Flavi in food raw materials, spices, and dried fruit using neutral red for visible-light signal detection.

Science.gov (United States)

Niessen, Ludwig; Bechtner, Julia; Fodil, Sihem; Taniwaki, Marta H; Vogel, Rudi F

2018-02-02

Aflatoxins can be produced by 21 species within sections Flavi (16 species), Ochraceorosei (2), and Nidulantes (3) of the fungal genus Aspergillus. They pose risks to human and animal health due to high toxicity and carcinogenicity. Detecting aflatoxin producers can help to assess toxicological risks associated with contaminated commodities. Species specific molecular assays (PCR and LAMP) are available for detection of major producers, but fail to detect species of minor importance. To enable rapid and sensitive detection of several aflatoxin producing species in a single analysis, a nor1 gene-specific LAMP assay was developed. Specificity testing showed that among 128 fungal species from 28 genera, 15 aflatoxigenic species in section Flavi were detected, including synonyms of A. flavus and A. parasiticus. No cross reactions were found with other tested species. The detection limit of the assay was 9.03pg of A. parasiticus genomic DNA per reaction. Visual detection of positive LAMP reactions under daylight conditions was facilitated using neutral red to allow unambiguous distinction between positive and negative assay results. Application of the assay to the detection of A. parasiticus conidia revealed a detection limit of 211 conidia per reaction after minimal sample preparation. The usefulness of the assay was demonstrated in the analysis of aflatoxinogenic species in samples of rice, nuts, raisins, dried figs, as well as powdered spices. Comparison of LAMP results with presence/absence of aflatoxins and aflatoxin producing fungi in 50 rice samples showed good correlation between these parameters. Our study suggests that the developed LAMP assay is a rapid, sensitive and user-friendly tool for surveillance and quality control in our food industry. Copyright © 2017 Elsevier B.V. All rights reserved.

Effects of tissue-preparation-induced callose synthesis on estimates of plasmodesma size exclusion limits.

Science.gov (United States)

Radford, J E; White, R G

2001-01-01

Plasmodesmata are often characterised by their size exclusion limit (SEL), which is the molecular weight of the largest dye, introduced by microinjection, that will move from cell to cell. In this study, we investigated whether commonly used techniques for isolation and manipulation of tissues, and microinjection of fluorescent dyes, affected the SEL, and whether any such effects could be ameliorated by inhibiting callose deposition. We examined young root epidermal cells of Arabidopsis thaliana and staminal hair cells of Tradescantia virginiana, two tissues often used in experiments on symplastic transport. Transport in root tips dissected from the main plant body and in stamen hairs removed from the base of the stamen filament was compared with transport in undissected roots and stamen hairs attached to the base of the filament, respectively. Tissues were microinjected with fluorescent dyes (457 Da to > 3 kDa) with or without prior incubation in the callose deposition inhibitors 2-deoxy-D-glucose or aniline blue fluorochrome. In both tissues, dissection reduced the SEL, which was largely prevented by prior incubation in 2-deoxy-D-glucose but not by incubation in aniline blue fluorochrome. Thus, standard methods for tissue preparation can cause sufficient callose deposition to reduce cell-to-cell transport, and this needs to be considered in studies employing microinjection. Introduction of the dyes by pressure injection rather than iontophoresis decreased the SEL in A. thaliana but increased it in T. virginiana, showing that these two injection techniques do not necessarily give identical results and that plasmodesmata in different tissues may respond differently to similar experimental procedures.

Real-time prostate-specific antigen detection with prostate-specific antigen imprinted capacitive biosensors

Energy Technology Data Exchange (ETDEWEB)

Ertürk, Gizem [Department of Biotechnology, Lund University, Lund (Sweden); Department of Biology, Hacettepe University, Ankara (Turkey); Hedström, Martin [Department of Biotechnology, Lund University, Lund (Sweden); CapSenze HB, Medicon Village, SE-223 63 Lund (Sweden); Tümer, M. Aşkın [Department of Biology, Hacettepe University, Ankara (Turkey); Denizli, Adil [Department of Chemistry, Hacettepe University, Ankara (Turkey); Mattiasson, Bo, E-mail: Bo.Mattiasson@biotek.lu.se [Department of Biotechnology, Lund University, Lund (Sweden); CapSenze HB, Medicon Village, SE-223 63 Lund (Sweden)

2015-09-03

Prostate specific antigen (PSA) is a valuable biomarker for early detection of prostate cancer, the third most common cancer in men. Ultrasensitive detection of PSA is crucial to screen the prostate cancer in an early stage and to detect the recurrence of the disease after treatment. In this report, microcontact-PSA imprinted (PSA-MIP) capacitive biosensor chip was developed for real-time, highly sensitive and selective detection of PSA. PSA-MIP electrodes were prepared in the presence of methacrylic acid (MAA) as the functional monomer and ethylene glycol dimethacrylate (EGDMA) as the cross-linker via UV polymerization. Immobilized Anti-PSA antibodies on electrodes (Anti-PSA) for capacitance measurements were also prepared to compare the detection performances of both methods. The electrodes were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM) and cyclic voltammetry (CV) and real-time PSA detection was performed with standard PSA solutions in the concentration range of 10 fg mL{sup −1}–100 ng mL{sup −1}. The detection limits were found as 8.0 × 10{sup −5} ng mL{sup −1} (16 × 10{sup −17} M) and 6.0 × 10{sup −4} ng mL{sup −1} (12 × 10{sup −16} M) for PSA-MIP and Anti-PSA electrodes, respectively. Selectivity studies were performed against HSA and IgG and selectivity coefficients were calculated. PSA detection was also carried out from diluted human serum samples and finally, reproducibility of the electrodes was tested. The results are promising and show that when the sensitivity of the capacitive system is combined with the selectivity and reproducibility of the microcontact-imprinting procedure, the resulting system might be used successfully for real-time detection of various analytes even in very low concentrations. - Highlights: • Microcontact imprinting method was used for preparing the sensor chip for capacitive biosensing. • High sensitivity was obtained. • Good selectivity was

Real-time prostate-specific antigen detection with prostate-specific antigen imprinted capacitive biosensors

International Nuclear Information System (INIS)

Ertürk, Gizem; Hedström, Martin; Tümer, M. Aşkın; Denizli, Adil; Mattiasson, Bo

2015-01-01

Prostate specific antigen (PSA) is a valuable biomarker for early detection of prostate cancer, the third most common cancer in men. Ultrasensitive detection of PSA is crucial to screen the prostate cancer in an early stage and to detect the recurrence of the disease after treatment. In this report, microcontact-PSA imprinted (PSA-MIP) capacitive biosensor chip was developed for real-time, highly sensitive and selective detection of PSA. PSA-MIP electrodes were prepared in the presence of methacrylic acid (MAA) as the functional monomer and ethylene glycol dimethacrylate (EGDMA) as the cross-linker via UV polymerization. Immobilized Anti-PSA antibodies on electrodes (Anti-PSA) for capacitance measurements were also prepared to compare the detection performances of both methods. The electrodes were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM) and cyclic voltammetry (CV) and real-time PSA detection was performed with standard PSA solutions in the concentration range of 10 fg mL"−"1–100 ng mL"−"1. The detection limits were found as 8.0 × 10"−"5 ng mL"−"1 (16 × 10"−"1"7 M) and 6.0 × 10"−"4 ng mL"−"1 (12 × 10"−"1"6 M) for PSA-MIP and Anti-PSA electrodes, respectively. Selectivity studies were performed against HSA and IgG and selectivity coefficients were calculated. PSA detection was also carried out from diluted human serum samples and finally, reproducibility of the electrodes was tested. The results are promising and show that when the sensitivity of the capacitive system is combined with the selectivity and reproducibility of the microcontact-imprinting procedure, the resulting system might be used successfully for real-time detection of various analytes even in very low concentrations. - Highlights: • Microcontact imprinting method was used for preparing the sensor chip for capacitive biosensing. • High sensitivity was obtained. • Good selectivity was demonstrated. • Stability of

An Entropy-Based Network Anomaly Detection Method

Directory of Open Access Journals (Sweden)

Przemysław Bereziński

2015-04-01

Full Text Available Data mining is an interdisciplinary subfield of computer science involving methods at the intersection of artificial intelligence, machine learning and statistics. One of the data mining tasks is anomaly detection which is the analysis of large quantities of data to identify items, events or observations which do not conform to an expected pattern. Anomaly detection is applicable in a variety of domains, e.g., fraud detection, fault detection, system health monitoring but this article focuses on application of anomaly detection in the field of network intrusion detection.The main goal of the article is to prove that an entropy-based approach is suitable to detect modern botnet-like malware based on anomalous patterns in network. This aim is achieved by realization of the following points: (i preparation of a concept of original entropy-based network anomaly detection method, (ii implementation of the method, (iii preparation of original dataset, (iv evaluation of the method.

Characteristics of right-sided colonic neoplasia and colonoscopy barriers limiting their early detection and prognosis: a review of the literature.

Science.gov (United States)

Fischbach, Wolfgang; Elsome, Rory; Amlani, Bharat

2018-06-05

Colonoscopy provides less protection from colorectal cancer in the right colon than the left. Areas covered: This review examines patient outcomes and colonoscopy success rates to identify factors that limit the protective effect of colonoscopy in the right colon. The MEDLINE and Embase databases were searched for literature from 2000 onwards, on the long-term outcomes and differences in screening practice between the right and left colon. In total, 12 systematic reviews (including nine meta-analyses) and 44 primary data records were included. Differences in patient outcomes and colonoscopy practice were identified between the right and left colon, suggesting that several factors, many of which disproportionally affect the right colon, impact lesion detection rates. Shorter withdrawal times reduce detection rates, while longer times significantly increase detection; mostly of adenomas in the right colon. Colonoscope attachments often only show a significant improvement in detection rates in the right colon, suggesting detection is more challenging due to visibility of the right colonic mucosa. Higher bowel cleansing grades significantly improve detection rates in the right colon compared to the left. Expert commentary: These findings confirm the need for continued improvement of colonoscopy effectiveness, and obligatory quality assessment, overall and especially in the right colon.

Sample preparation and fractionation for proteome analysis and cancer biomarker discovery by mass spectrometry.

Science.gov (United States)

Ahmed, Farid E

2009-03-01

Sample preparation and fractionation technologies are one of the most crucial processes in proteomic analysis and biomarker discovery in solubilized samples. Chromatographic or electrophoretic proteomic technologies are also available for separation of cellular protein components. There are, however, considerable limitations in currently available proteomic technologies as none of them allows for the analysis of the entire proteome in a simple step because of the large number of peptides, and because of the wide concentration dynamic range of the proteome in clinical blood samples. The results of any undertaken experiment depend on the condition of the starting material. Therefore, proper experimental design and pertinent sample preparation is essential to obtain meaningful results, particularly in comparative clinical proteomics in which one is looking for minor differences between experimental (diseased) and control (nondiseased) samples. This review discusses problems associated with general and specialized strategies of sample preparation and fractionation, dealing with samples that are solution or suspension, in a frozen tissue state, or formalin-preserved tissue archival samples, and illustrates how sample processing might influence detection with mass spectrometric techniques. Strategies that dramatically improve the potential for cancer biomarker discovery in minimally invasive, blood-collected human samples are also presented.

Development and Validation of Spectrophotometric Methods for the Determination of Rasagiline in Pharmaceutical Preparations

Directory of Open Access Journals (Sweden)

Serife Evrim Kepekci Tekkeli

2013-01-01

Full Text Available This study presents three simple, rapid, and accurate spectrophotometric methods for the determination of Rasagiline (RSG in pharmaceutical preparations. The determination procedures depend on the reaction of RSG with chloranilic acid for method A, tetrachloro-1,4-benzoquinone for method B, and 7,7,8,8-tetracyanoquinodimethane for method C. The colored products were quantitated spectrophotometrically at 524, 535, and 843 nm for methods A, B, and C, respectively. Different variables affecting the reaction were optimized. Linearity ranges of the methods with good correlation coefficients (0.9988–0.9996 were observed as 25–300 µg mL−1, 25–350 µg mL−1, and 50–500 µg mL−1 for methods A, B, and C, respectively. The formation of products takes place through different mechanisms. The sites of interaction were confirmed by elemental analysis using IR and 1H-NMR spectroscopy. The validation of the methods was carried out in terms of specificity, linearity, accuracy, precision, robustness, limit of detection, and limit of quantitation. No interference was observed from concomitants usually present in dosage forms. The methods were applied successfully to the determination of RSG in pharmaceutical preparations.

Heat transfer calculations for the High Flux Isotope Reactor (HFIR). Technical specifications: bases for safety limits and limiting safety system settings

International Nuclear Information System (INIS)

Sims, T.M.; Swanks, J.H.

1977-09-01

Heat transfer analyses, in support of the preparation of the HFIR technical specifications, were made to establish the bases for the safety limits and limiting safety system settings applicable to the HFIR. The results of these analyses, along with the detailed bases, are presented

Detecting position using ARKit II: generating position-time graphs in real-time and further information on limitations of ARKit

Science.gov (United States)

Dilek, Ufuk; Erol, Mustafa

2018-05-01

ARKit is a framework which allows developers to create augmented reality apps for the iPhone and iPad. In a previous study, we had shown that it could be used to detect position in educational physics experiments and emphasized that the ability to provide position data in real-time was one of the prominent features of this newly emerging technology. In this study, we demonstrate an example of how real-time data acquisition can be employed in educational settings, report some of the limitations of ARKit and how we have overcome these limitations. By means of ARKit or a similar framework, ordinary mobile devices can be adapted for use in microcomputer-based lab activities.

Limited utility of preoperative studies in preparation for colostomy closure.

Science.gov (United States)

Pokorny, R M; Heniford, T; Allen, J W; Tuckson, W B; Galandiuk, S

1999-04-01

Numerous diagnostic and therapeutic practices are used in an attempt to reduce the morbidity of colostomy closures. Our principal aim was to evaluate the role of preoperative studies, specifically barium enemas and endoscopic examinations, performed before colostomy closures. Additionally, we wished to identify other practices involved in the perioperative management of patients undergoing colostomy closure that influenced morbidity. The records of 100 consecutive patients who underwent elective colostomy closure at University of Louisville Hospital between January 1989 and July 1995 were reviewed. Wound infection was the most common complication (12%). Various bowel preparations were equivalent in efficacy and did not influence the complication rate. Intermittent wound irrigation with antibiotics for 3 days postoperatively, via subcutaneous drains, was associated with a low incidence of incision infection. Preoperative barium enema or sigmoidoscopy were often performed but rarely useful. Performing these examinations merely increased hospital cost without a corresponding decline in morbidity.

Comparison of approximate formulas for decision levels and detection limits for paired counting with the exact results

International Nuclear Information System (INIS)

Potter, W.E.

2005-01-01

The exact probability density function for paired counting can be expressed in terms of modified Bessel functions of integral order when the expected blank count is known. Exact decision levels and detection limits can be computed in a straightforward manner. For many applications perturbing half-integer corrections to Gaussian distributions yields satisfactory results for decision levels. When there is concern about the uncertainty for the expected value of the blank count, a way to bound the errors of both types using confidence intervals for the expected blank count is discussed. (author)

A lab-on-a-chip system with integrated sample preparation and loop-mediated isothermal amplification for rapid and quantitative detection of Salmonella spp. in food samples

DEFF Research Database (Denmark)

Sun, Yi; Than Linh, Quyen; Hung, Tran Quang

2015-01-01

was capable to detect Salmonella at concentration of 50 cells per test within 40 min. The simple design, together with high level of integration, isothermal amplification, and quantitative analysis of multiple samples in short time will greatly enhance the practical applicability of the LOC system for rapid...... amplification (LAMP) for rapid and quantitative detection of Salmonella spp. in food samples. The whole diagnostic procedures including DNA isolation, isothermal amplification, and real-time detection were accomplished in a single chamber. Up to eight samples could be handled simultaneously and the system...... and usually take a few hours to days to complete. In response to the demand for rapid on line or at site detection of pathogens, in this study, we describe for the first time an eight-chamber lab-on-a-chip (LOC) system with integrated magnetic beads-based sample preparation and loop-mediated isothermal...

The limitations in clinical teaching, learning and practice of ...

African Journals Online (AJOL)

The “extension for prevention” dogma by G.V Black had been jettisoned while the modern concept of conservatism or minimal cavity preparation has been well embraced by dental practitioners. However, there are some limitations in clinical teaching of conservative amalgam cavity preparation which include late patient ...

Current limiter circuit system

Science.gov (United States)

Witcher, Joseph Brandon; Bredemann, Michael V.

2017-09-05

An apparatus comprising a steady state sensing circuit, a switching circuit, and a detection circuit. The steady state sensing circuit is connected to a first, a second and a third node. The first node is connected to a first device, the second node is connected to a second device, and the steady state sensing circuit causes a scaled current to flow at the third node. The scaled current is proportional to a voltage difference between the first and second node. The switching circuit limits an amount of current that flows between the first and second device. The detection circuit is connected to the third node and the switching circuit. The detection circuit monitors the scaled current at the third node and controls the switching circuit to limit the amount of the current that flows between the first and second device when the scaled current is greater than a desired level.

Characterization of naturally occurring airborne diacetyl concentrations associated with the preparation and consumption of unflavored coffee.

Science.gov (United States)

Pierce, Jennifer S; Abelmann, Anders; Lotter, Jason T; Comerford, Chris; Keeton, Kara; Finley, Brent L

2015-01-01

Diacetyl, a suspected cause of respiratory disorders in some food and flavorings manufacturing workers, is also a natural component of roasted coffee. We characterized diacetyl exposures that would plausibly occur in a small coffee shop during the preparation and consumption of unflavored coffee. Personal (long- and short-term) and area (long-term) samples were collected while a barista ground whole coffee beans, and brewed and poured coffee into cups. Simultaneously, long-term personal samples were collected as two participants, the customers, drank one cup of coffee each per h. Air sampling and analyses were conducted in accordance with OSHA Method 1012. Diacetyl was detected in all long-term samples. The long-term concentrations for the barista and area samples were similar, and ranged from 0.013⿿0.016 ppm; long-term concentrations for the customers were slightly lower and ranged from 0.010⿿0.014 ppm. Short-term concentrations ranged from below the limit of detection (barista ranged from 0.007⿿0.013 ppm; these values exceed recommended 8 h TWA occupational exposure limits (OELs) for diacetyl and are comparable to long-term personal measurements collected in various food and beverage production facilities. The concentrations measured based on area sampling were comparable to those measured in the breathing zone of the barista, thus exceedances of the recommended OELs may also occur for coffee shop workers who do not personally prepare coffee (e.g., cashier, sanitation/maintenance). These findings suggest that the practicality and scientific basis of the recommended OELs for diacetyl merit further consideration.

Trace elements detection in whole food samples by Neutron Activation Analysis, k{sub 0}-method

Energy Technology Data Exchange (ETDEWEB)

Sathler, Márcia Maia; Menezes, Maria Ângela de Barros Correia, E-mail: maia.sathler@gmail.com, E-mail: menezes@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Salles, Paula Maria Borges de, E-mail: pauladesalles@yahoo.com.br [Universidade Federal de Minas Gerais (DEN/UFMG), Belo Horizonte, MG (Brazil). Departamento de Engenharia Nuclear

2017-07-01

Inorganic elements, from natural and anthropogenic sources are present in foods in different concentrations. With the increase in anthropogenic activities, there was also a considerable increase in the emission of these elements in the environment, leading to the need of monitoring the elemental composition of foods available for consumption. Numerous techniques have been used to detect inorganic elements in biological and environmental matrices, always aiming at reaching lower detection limits in order to evaluate the trace element content in the sample. Neutron activation analysis (INAA), applying the k{sub 0}-method, produces accurate and precise results without the need of chemical preparation of the samples – that could cause their contamination. This study evaluated the presence of inorganic elements in whole foods samples, mainly elements on trace levels. For this purpose, seven samples of different types of whole foods were irradiated in the TRIGA MARK I IPR-R1 research reactor - located at CDTN/CNEN, in Belo Horizonte, MG. It was possible to detect twenty two elements above the limit of detection in, at least, one of the samples analyzed. This study reaffirms the INAA, k{sub 0} - method, as a safe and efficient technique for detecting trace elements in food samples. (author)

Detection of nanoplastics in food by asymmetric flow field-flow fractionation coupled to multi-angle light scattering: possibilities, challenges and analytical limitations

DEFF Research Database (Denmark)

Correia, Manuel; Löschner, Katrin

2018-01-01

We tested the suitability of asymmetric flow field-flow fractionation (AF4) coupled to multi-angle light scattering (MALS) for detection of nanoplastics in fish. A homogenized fish sample was spiked with 100 nm polystyrene nanoparticles (PSNPs) (1.3 mg/g fish). Two sample preparation strategies...... were tested: acid digestion and enzymatic digestion with proteinase K. Both procedures were found suitable for degradation of the organic matrix. However, acid digestion resulted in large PSNPs aggregates/agglomerates (> 1 μm). The presence of large particulates was not observed after enzymatic...

Physics of detecting torsion and placing limits on its effects

International Nuclear Information System (INIS)

Stoeger, W.R.

1985-01-01

The essential principles of torsion-detection physics are presented, and an evaluation is conducted of several conceivable types of experiments and observations for actually detecting torsion fields, reemphasizing also the evident impossibility of successfully searching for its manifestations among cosmological relics. In particular, a polarized body, with net intrinsic (fundamental-particle) spin, is essential for detecting a torsion field. One which possesses only orbital angular momentum - rotation - or an unpolarized intrinsic spin density will not feel torsion. The fundamental problem in searching for such fields is the extremely small basic unit of the coupling or interaction energy between the torsion field and spin. The best way of maximizing the total interaction energy is to increase the spin density of the source sigma-s and at the same time the spin number SD of the detector. 15 references

Detection Limit of Smectite by Chemin IV Laboratory Instrument: Preliminary Implications for Chemin on the Mars Science Laboratory Mission

Science.gov (United States)

Archilles, Cherie; Ming, D. W.; Morris, R. V.; Blake, D. F.

2011-01-01

The CheMin instrument on the Mars Science Laboratory (MSL) is an miniature X-ray diffraction (XRD) and X-ray fluorescence (XRF) instrument capable of detecting the mineralogical and elemental compositions of rocks, outcrops and soils on the surface of Mars. CheMin uses a microfocus-source Co X-ray tube, a transmission sample cell, and an energy-discriminating X-ray sensitive CCD to produce simultaneous 2-D XRD patterns and energy-dispersive X-ray histograms from powdered samples. CRISM and OMEGA have identified the presence of phyllosilicates at several locations on Mars including the four candidate MSL landing sites. The objective of this study was to conduct preliminary studies to determine the CheMin detection limit of smectite in a smectite/olivine mixed mineral system.

The use of a European coinage alloy to compare the detection limits of mobile XRF systems. A feasibility study

Energy Technology Data Exchange (ETDEWEB)

Cesareo, R. [Struttura Dipartimentale di Matematica e Fisica, Universita di Sassari, Sassari (Italy); Ferretti, M. [CNR-Istituto per le Tecnologie Applicate ai Beni Culturali, Rome (Italy); Gigante, G.E. [Dipartimento di Fisica, Universita di Roma ' La Sapienza' , Rome (Italy); Guida, G. [Laboratorio di Chimica, Istituto Centrale per il Restauro, Rome (Italy); Moioli, P. [Unita Tecnico-Scientifica Materiali e Nuove Tecnologie, ENEA, Rome (Italy); Ridolfi, S. [Ars Mensurae, Rome (Italy); Roldan Garcia, C. [Unidad de Arqueometria, Instituto de Ciencia de Materiales, Universidad de Valencia, Valencia (Spain)

2007-05-15

The investigation of archaeological and historical materials makes use of techniques that, though borrowed from other fields of research and industrial production, frequently have to be 're-invented' because of peculiar characteristics of the analysed objects. Artistic relevance, limited movability, compositional and structural heterogeneity radically change the experimental approach and often require ad hoc designed equipment. These considerations also apply to x-ray fluorescence, especially regarding mobile systems. The extensive development and use of mobile spectrometers has produced an extremely diversified context and created the need for common criteria to evaluate their performances as well as the advisability of a survey on the existing equipment. This paper shows the feasibility of such an idea through a demonstrative survey that was carried out among users of different mobile x-ray fluorescence spectrometry (XRF) systems in the areas of Rome, Italy and Valencia, Spain. The experimental protocol was based on measuring spectrometer detection limits with the single standard method. The standard was the 50 Euro-cent coin, whose alloy is made of 89% Cu, 5% Al, 5% Zn, 1% Sn; the large spread of the European currency guarantees maximum availability. The experimental data show that the use of different x-ray tubes and detectors results in detection limits that may differ from each other by a factor of 6 for Zn and almost 100 for Sn; despite the large number of variables that in principle affect the performance, it was observed that the high voltage of the x-ray tube is the most important parameter. (authors)

A quantitative method for determining a representative detection limit of the forensic luminol test for latent bloodstains.

Science.gov (United States)

Cassidy, Brianna M; Lu, Zhenyu; Martin, Jennifer P; Tazik, Shawna K; Kellogg, Katie W; DeJong, Stephanie A; Belliveau, Elle O; Kilgore, Katherine E; Ervin, Samantha M; Meece-Rayle, Mackenzie; Abraham, Alyssa M; Myrick, Michael L; Morgan, Stephen L

2017-09-01

The luminol test has been used for over 60 years by forensic investigators for presumptive identification of blood and visualization of blood splatter patterns. Multiple studies have estimated the limit of detection (LD) for bloodstains when luminol is employed, with results ranging from 100× to 5,000,000× dilute. However, these studies typically have not identified and controlled important experimental variables which may affect the luminol LD for bloodstains. Without control of experimental parameters in the laboratory, variables which affect the potential of presumptive bloodstain test methods remain largely unknown, and comparisons required to establish new, more powerful detection methods are simply impossible. We have developed a quantitative method to determine the relationship between the amount of blood present and its reaction with luminol by measuring, under controlled conditions, the resulting chemiluminescent intensity with a video camera, combined with processing of the digital intensity data. The method resulted in an estimated LD for bloodstains on cotton fabric at ∼200,000× diluted blood with a specific luminol formulation. Although luminol is the focus of this study, the experimental protocol used could be modified to study effects of variables using other blood detection reagents. Copyright © 2017 Elsevier B.V. All rights reserved.

Preparation and characterization of gadolinium-loaded PLGA particles surface modified with RGDS for the detection of thrombus

Directory of Open Access Journals (Sweden)

Zhang Y

2013-10-01

Full Text Available Yu Zhang,1 Jun Zhou,1 Dajing Guo,1 Meng Ao,2 Yuanyi Zheng,2 Zhigang Wang21Department of Radiology, the Second Affiliated Hospital of Chongqing Medical University, Chongqing, People’s Republic of China; 2Institute of Ultrasound Imaging, Department of Ultrasound, the Second Affiliated Hospital of Chongqing Medical University, Chongqing, People’s Republic of ChinaAbstract: Thrombotic disease is a leading cause of death and disability worldwide. The development of magnetic resonance molecular imaging provides potential promise for early disease diagnosis. In this study, we explore the preparation and characterization of gadolinium (Gd-loaded poly (lactic-co-glycolic acid (PLGA particles surface modified with the Arg-Gly-Asp-Ser (RGDS peptide for the detection of thrombus. PLGA was employed as the carrier-delivery system, and a double emulsion solvent-evaporation method (water in oil in water was used to prepare PLGA particles encapsulating the magnetic resonance contrast agent Gd diethylenetriaminepentaacetic acid (DTPA. To synthesize the Gd-PLGA/chitosan (CS-RGDS particles, carbodiimide-mediated amide bond formation was used to graft the RGDS peptide to CS to form a CS-RGDS film that coated the surface of the PLGA particles. Blank PLGA, Gd-PLGA, and Gd-PLGA/CS particles were fabricated using the same water in oil in water method. Our results indicated that the RGDS peptide successfully coated the surface of the Gd-PLGA/CS-RGDS particles. The particles had a regular shape, smooth surface, relatively uniform size, and did not aggregate. The high electron density of the Gd-loaded particles and a translucent film around the particles coated with the CS and CS-RGDS films could be observed by transmission electron microscopy. In vitro experiments demonstrated that the Gd-PLGA/CS-RGDS particles could target thrombi and could be imaged using a clinical magnetic resonance scanner. Compared with the Gd-DTPA solution, the longitudinal relaxation time of

Low-Fiber Diet in Limited Bowel Preparation for CT Colonography: Influence on Image Quality and Patient Acceptance

NARCIS (Netherlands)

Liedenbaum, Marjolein H.; Denters, Maaike J.; de Vries, Ayso H.; van Ravesteijn, Vincent F.; Bipat, Shandra; Vos, Frans M.; Dekker, Evelien; Stoker, Jaap

2010-01-01

OBJECTIVE. The purpose of this study was to determine whether a low-fiber diet is necessary for optimal tagging-only bowel preparation for CT colonography. SUBJECTS AND METHODS. Fifty consecutively enrolled patients received an iodine bowel preparation: 25 patients used a low-fiber diet and 25 used

The detection and stabilisation of limit cycle for deterministic finite automata

Science.gov (United States)

Han, Xiaoguang; Chen, Zengqiang; Liu, Zhongxin; Zhang, Qing

2018-04-01

In this paper, the topological structure properties of deterministic finite automata (DFA), under the framework of the semi-tensor product of matrices, are investigated. First, the dynamics of DFA are converted into a new algebraic form as a discrete-time linear system by means of Boolean algebra. Using this algebraic description, the approach of calculating the limit cycles of different lengths is given. Second, we present two fundamental concepts, namely, domain of attraction of limit cycle and prereachability set. Based on the prereachability set, an explicit solution of calculating domain of attraction of a limit cycle is completely characterised. Third, we define the globally attractive limit cycle, and then the necessary and sufficient condition for verifying whether all state trajectories of a DFA enter a given limit cycle in a finite number of transitions is given. Fourth, the problem of whether a DFA can be stabilised to a limit cycle by the state feedback controller is discussed. Criteria for limit cycle-stabilisation are established. All state feedback controllers which implement the minimal length trajectories from each state to the limit cycle are obtained by using the proposed algorithm. Finally, an illustrative example is presented to show the theoretical results.

Shot-Noise Limited Time-Encoded Raman Spectroscopy

Directory of Open Access Journals (Sweden)

Sebastian Karpf

2017-01-01

Full Text Available Raman scattering, an inelastic scattering mechanism, provides information about molecular excitation energies and can be used to identify chemical compounds. Albeit being a powerful analysis tool, especially for label-free biomedical imaging with molecular contrast, it suffers from inherently low signal levels. This practical limitation can be overcome by nonlinear enhancement techniques like stimulated Raman scattering (SRS. In SRS, an additional light source stimulates the Raman scattering process. This can lead to orders of magnitude increase in signal levels and hence faster acquisition in biomedical imaging. However, achieving a broad spectral coverage in SRS is technically challenging and the signal is no longer background-free, as either stimulated Raman gain (SRG or loss (SRL is measured, turning a sensitivity limit into a dynamic range limit. Thus, the signal has to be isolated from the laser background light, requiring elaborate methods for minimizing detection noise. Here, we analyze the detection sensitivity of a shot-noise limited broadband stimulated time-encoded Raman (TICO-Raman system in detail. In time-encoded Raman, a wavelength-swept Fourier domain mode locking (FDML laser covers a broad range of Raman transition energies while allowing a dual-balanced detection for lowering the detection noise to the fundamental shot-noise limit.

DETECTING ALIEN LIMIT CYCLES NEAR A HAMILTONIAN 2-SADDLE CYCLE

OpenAIRE

LUCA, Stijn; DUMORTIER, Freddy; Caubergh, M.; Roussarie, R.

2009-01-01

This paper aims at providing and example of a cubic Hamiltonian 2-saddle cycle that after bifurcation can give rise to an alien limit cycle; this is a limit cycle that is not controlled by a zero of the related Abelian integral. To guarantee the existence of an alien limit cycle one can verify generic conditions on the Abelian integral and on the transition map associated to the connections of the 2-saddle cycle. In this paper, a general method is developed to compute the first and second der...

Green synthesis of carbon quantum dots from lignite coal and the application in Fe3+ detection

Science.gov (United States)

Liu, Xuexia; Hao, Juanyuan; Liu, Jianhui; Tao, Hongcai

2018-02-01

Carbon quantum dots (CQDs) had attracted much attention due to their unique structures and excellent properties. Their green preparation was one of the research frontiers. However, most of the CQDs were prepared by strong acid oxidation, the way of which was not friendly to the environment. In this study, CQDs were prepared by green ozone oxidation of lignite coal, which is abundant and inexpensive. The CQDs were well dispersed, the size distribution of the obtained CQDs centralized from 2 to 4 nm with the average diameter of about 2.8 nm. In addition, the as-prepared CQDs containing rich oxygen functional groups exhibited good water-solubility and optical properties with yield reached 35%. The CQDs showed a highly sensitive and selective quenching effect to Fe3+ with desirable anti-interference performance. Moreover, the fluorescence intensity of CQDs had a good linear response to the Fe3+ concentration ranging from 10 to 150 µmol/L with the detection limit of 0.26 µmol/L. This green and facile synthesis method had the prospect of large-scale preparation of CQDs.

Does parallel item content on WOMAC's Pain and Function Subscales limit its ability to detect change in functional status?

Directory of Open Access Journals (Sweden)

Kennedy Deborah M

2004-06-01

Full Text Available Abstract Background Although the Western Ontario and McMaster University Osteoarthritis Index (WOMAC is considered the leading outcome measure for patients with osteoarthritis of the lower extremity, recent work has challenged its factorial validity and the physical function subscale's ability to detect valid change when pain and function display different profiles of change. This study examined the etiology of the WOMAC's physical function subscale's limited ability to detect change in the presence of discordant changes for pain and function. We hypothesized that the duplication of some items on the WOMAC's pain and function subscales contributed to this shortcoming. Methods Two eight-item physical function scales were abstracted from the WOMAC's 17-item physical function subscale: one contained activities and themes that were duplicated on the pain subscale (SIMILAR-8; the other version avoided overlapping activities (DISSIMILAR-8. Factorial validity of the shortened measures was assessed on 310 patients awaiting hip or knee arthroplasty. The shortened measures' abilities to detect change were examined on a sample of 104 patients following primary hip or knee arthroplasty. The WOMAC and three performance measures that included activity specific pain assessments – 40 m walk test, stair test, and timed-up-and-go test – were administered preoperatively, within 16 days of hip or knee arthroplasty, and at an interval of greater than 20 days following the first post-surgical assessment. Standardized response means were used to quantify change. Results The SIMILAR-8 did not demonstrate factorial validity; however, the factorial structure of the DISSIMILAR-8 was supported. The time to complete the performance measures more than doubled between the preoperative and first postoperative assessments supporting the theory that lower extremity functional status diminished over this interval. The DISSIMILAR-8 detected this deterioration in functional

Food preparation supplies predict children's family meal and home-prepared dinner consumption in low-income households.

Science.gov (United States)

Appelhans, Bradley M; Waring, Molly E; Schneider, Kristin L; Pagoto, Sherry L

2014-05-01

Frequent family meals and home food preparation are considered important for children's nutritional health and weight maintenance. This cross-sectional study tested whether these parent-driven behaviors are related to the availability of food preparation supplies in low-income urban households. Caregivers of children ages 6-13 provided information on family meal frequency, child consumption of home-prepared dinners, household food insecurity, and attitudes towards cooking. Researchers used a newly developed Food Preparation Checklist (FPC) to assess the availability of 41 food preparation supplies during a physical audit of the home environment. Caregivers and children provided anthropometric measurements and jointly reported on child dietary intake. In ordinal logistic regression models, greater home availability of food preparation supplies was associated with more frequent family meals and child consumption of home-prepared dinners. Associations were independent of household financial strain, food insecurity, caregiver attitudes toward cooking, and sociodemographic characteristics. Fewer food preparation supplies were available in households characterized by greater food insecurity, lower income, and negative caregiver attitudes towards cooking, but did not differ by child or caregiver weight status. As in prior studies, more frequent family meals and consumption of home-prepared dinners were associated with healthier child dietary intake in several areas. We conclude that food preparation supplies are often limited in the most socioeconomically disadvantaged households, and their availability is related to the frequency with which children consume family meals and home-prepared dinners. The potential role of food preparation supplies as contributors to socioeconomic disparities in child nutritional health and obesity deserves further study. Copyright © 2014 Elsevier Ltd. All rights reserved.

Limit of detection of a fiber optics gyroscope using a super luminescent radiation source; Limite de deteccion de un giroscopio de fibra optica usando una fuente de radiacion superluminiscente

Energy Technology Data Exchange (ETDEWEB)

Sandoval R, G.E. [Laboratorio de Optica Aplicada, Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-186, 04510 Mexico D.F. (Mexico); Nikolaev, V.A. [Departamento de Optica y Radiofisica Cuantica, Universidad Estatal de Telecomunicaciones de San Petersburgo, M.A. Bonch-Bruyevich, Kanal Moika 61, Saint Petersburg 191186, (Russian Federation)

2003-07-01

The main objective of this work is to establish the dependence of characteristics of the fiber optics gyroscope (FOG) with respect to the parameters of the super luminescent emission source based on doped optical fiber with rare earth elements (Super luminescent Fiber Source, SFS), argument the pumping rate election of the SFS to obtain characteristics limits of the FOG sensibility. By using this type of emission source in the FOG is recommend to use the rate when the direction of the pumping signal coincide with the super luminescent signal. The most results are the proposition and argumentation of the SFS election as emission source to be use in the FOG of the phase type. Such a decision allow to increase the characteristics of the FOG sensibility in comparison with the use of luminescent source of semiconductors emission which are extensively used in the present time. The use of emission source of the SFS type allow to come closer to the threshold of the obtained sensibility limit (detection limit) which is determined with the shot noise. (Author)

Analysis of soil and sewage sludge by ICP-OES and the German standard DIN 38414 sample preparation technique (P3)

International Nuclear Information System (INIS)

Edlund, M.; Heitland, P.; Visser, H.

2002-01-01

Full text: The elemental analyses of soil and sewage sludge has developed to become one of the main applications for ICP optical emission spectrometry (ICP-OES) and is described in many official procedures. These methods include different acid mixtures and digestion techniques. Even though the German standard DIN 38414 part 7 and the Dutch NEN 6465 do not guarantee complete recoveries for all elements, they are widely accepted in Europe. This paper describes sample preparation, line selection and investigates precision, accuracy and Limits of detection. The SPECTRO CIROSCCD EOP with axial plasma observation and the SPECTRO CIROSCCD SOP with radial observation were compared and evaluated for the analyses of soil and sewage sludge. Accuracy was investigated using the certified reference materials CRM-141 R, CRM-143 R and GSD 11. Both instruments show excellent performance in terms of speed, precision, accuracy and detection limits for the determination of trace metals in soil and sewage sludge. (author)

Carboxymethylguargum-silver nanocomposite: green synthesis, characterization and an optical sensor for ammonia detection

International Nuclear Information System (INIS)

Gupta, Anek Pal; Verma, Devendra Kumar

2014-01-01

This work describes the preparation of new carboxymethyl guar gum-silver nanocomposite (CMGG/Ag NC) by green synthesis method. For this carboxymethyl guar gum was used as a reducing agent as well as stabilizer. The silver nanoparticles obtained were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), UV–vis spectroscopy, Fourier transform infrared (FTIR) and energy dispersive x-ray analysis (EDX). The average size of the silver nanoparticles was found of ∼6 nm. Thus, the obtained CMGG/AgNPs NC was examined for optical sensing property for detection of ammonia in aqueous medium. The response time and the detection limit of ammonia in aqueous solution were detected at room temperature. It was concluded that in the future, at this room temperature optical ammonia sensor may be used for medical diagnosis and clinically for detecting low ammonia level (up to 1 ppm) in biological samples for various biomedical applications. (paper)

Coacervative extraction as a green technique for sample preparation for the analysis of organic compounds.

Science.gov (United States)

Melnyk, A; Wolska, L; Namieśnik, J

2014-04-25

One of the present trends in analytical chemistry is miniaturization, which is one of the methods of green analytical chemistry application. A particular emphasis is placed on the elimination of the use of large amounts of organic solvents which are toxic and harmful to the environment, maintaining high efficiency of the extraction process, high recovery values and low values of quantification (LOQ) and detection (LOD) limits. These requirements are fulfilled by coacervative extraction (CAE) technique. In this review, theoretical aspects of the coacervation process are presented along with environmental and bioanalytical applications of this technique, its advantages, limitations and competitiveness with other techniques. Due to its simplicity and rapidity, CAE is an excellent alternative for currently practiced procedures of sample preparation for the analysis of organic compounds. Copyright © 2014 Elsevier B.V. All rights reserved.

Preparation of a zeolite-modified polymer monolith for identification of synthetic colorants in lipsticks

Energy Technology Data Exchange (ETDEWEB)

Wang, Huiqi; Li, Zheng [College of Chemistry, Jilin University, Changchun 130012 (China); Niu, Qian [Jilin Entry-Exit Inspection and Quarantine Bureau, Changchun 130062 (China); Ma, Jiutong [College of Chemistry, Jilin University, Changchun 130012 (China); Jia, Qiong, E-mail: jiaqiong@jlu.edu.cn [College of Chemistry, Jilin University, Changchun 130012 (China)

2015-10-30

Graphical abstract: Poly(methacrylic acid-ethylene dimethacrylate) monolithic column embedded with zeolites was prepared and employed for the polymer monolith microextraction of colorants combined with HPLC. - Highlights: • Zeolite, as a kind of mesoporous material, was firstly combined with PMME. • Zeolite@poly(MAA-EDMA) monolith columns were prepared for the enrichment of colorants. • Zeolite@poly(MAA-EDMA) monolith columns demonstrated relatively high extraction capacity. - Abstract: A novel zeolite-modified poly(methacrylic acid-ethylenedimethacrylate) (zeolite@poly(MAA-EDMA)) monolithic column was prepared with the in situ polymerization method and employed in polymer monolith microextraction for the separation and preconcentration of synthetic colorants combined with high performance liquid chromatography. The polymer was characterized by scanning electronmicroscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermo-gravimetric analysis. Various parameters affecting the extraction efficiency were investigated and optimized. Under the optimum experimental conditions, we obtained acceptable linearities, low limits of detection, and good intra-day/inter-day relative standard deviations. The method was applied to the determination of synthetic colorants in lipsticks with recoveries ranged from 70.7% to 109.7%. Compared with conventional methacrylic acid-based monoliths, the developed monolith exhibited high enrichment capacity because of the introduction of zeolites into the preparation process. The extraction efficiency followed the order: zeolite@poly(MAA-EDMA) > poly(MAA-EDMA) > direct HPLC analysis.

Detection of Human Ig G Using Photoluminescent Porous Silicon Interferometer.

Science.gov (United States)

Cho, Bomin; Kim, Seongwoong; Woo, Hee-Gweon; Kim, Sungsoo; Sohn, Honglae

2015-02-01

Photoluminescent porous silicon (PSi) interferometers having dual optical properties, both Fabry-Pérot fringe and photolumincence (PL), have been developed and used as biosensors for detection of Human Immunoglobin G (Ig G). PSi samples were prepared by electrochemical etching of p-type silicon under white light exposure. The surface of PSi was characterized using a cold field emission scanning electron microscope. The sensor system studied consisted of a single layer of porous silicon modified with Protein A. The system was probed with various fragments of aqueous human immunoglobin G (Ig G) analyte. Both reflectivity and PL were simultaneously measured under the exposure of human Ig G. An increase of optical thickness and decrease of PL were obtained under the exposure of human Ig G. Detection limit of 500 fM was observed for the human Ig G.

Detection and identification of "new" beta-agonists in black-market preparations

NARCIS (Netherlands)

van Ginkel LA; Stephany RW; van Rossum HJ; Visser T; den Engelsman T; de Jong APJM; Jacquemijns M; Zomer G

1992-01-01

In several "black-market" used for growth promotion preparations new compounds were found belonging to the group of N-phenylethanolamines with structures very similar to compounds known to be used for veal calf and cattle production, the so called beta-agonists. The two most important

Matrix removal in state of the art sample preparation methods for serum by charged aerosol detection and metabolomics-based LC-MS.

Science.gov (United States)

Schimek, Denise; Francesconi, Kevin A; Mautner, Anton; Libiseller, Gunnar; Raml, Reingard; Magnes, Christoph

2016-04-07

Investigations into sample preparation procedures usually focus on analyte recovery with no information provided about the fate of other components of the sample (matrix). For many analyses, however, and particularly those using liquid chromatography-mass spectrometry (LC-MS), quantitative measurements are greatly influenced by sample matrix. Using the example of the drug amitriptyline and three of its metabolites in serum, we performed a comprehensive investigation of nine commonly used sample clean-up procedures in terms of their suitability for preparing serum samples. We were monitoring the undesired matrix compounds using a combination of charged aerosol detection (CAD), LC-CAD, and a metabolomics-based LC-MS/MS approach. In this way, we compared analyte recovery of protein precipitation-, liquid-liquid-, solid-phase- and hybrid solid-phase extraction methods. Although all methods provided acceptable recoveries, the highest recovery was obtained by protein precipitation with acetonitrile/formic acid (amitriptyline 113%, nortriptyline 92%, 10-hydroxyamitriptyline 89%, and amitriptyline N-oxide 96%). The quantification of matrix removal by LC-CAD showed that the solid phase extraction method (SPE) provided the lowest remaining matrix load (48-123 μg mL(-1)), which is a 10-40 fold better matrix clean-up than the precipitation- or hybrid solid phase extraction methods. The metabolomics profiles of eleven compound classes, comprising 70 matrix compounds showed the trends of compound class removal for each sample preparation strategy. The collective data set of analyte recovery, matrix removal and matrix compound profile was used to assess the effectiveness of each sample preparation method. The best performance in matrix clean-up and practical handling of small sample volumes was showed by the SPE techniques, particularly HLB SPE. CAD proved to be an effective tool for revealing the considerable differences between the sample preparation methods. This detector can

Limited irrigation research and infrared thermometry for detecting water stress

Science.gov (United States)

The USDA-ARS Limited Irrigation Research Farm, located outside of Greeley Colorado, is an experiment evaluating management perspectives of limited irrigation water. An overview of the farm systems is shown, including drip irrigation systems, water budgeting, and experimental design, as well as preli...

Preparation of targets by ion implantation

International Nuclear Information System (INIS)

Santry, D.C.

1976-01-01

Various factors are described which are involved in target preparation by direct ion implantation and the limitations and pitfalls of the method are emphasized. Examples are given of experiments for which ion implanted targets are well suited. (author)

A fluorescent immunochromatographic strip test using Quantum Dots for fumonisins detection.

Science.gov (United States)

Di Nardo, F; Anfossi, L; Giovannoli, C; Passini, C; Goftman, V V; Goryacheva, I Y; Baggiani, C

2016-04-01

A fluorescent immunochromatographic strip test (ICST) based on the use of Quantum Dots (QD) was developed and applied to detect fumonisins in maize samples. A limit of detection for fumonisin B1 of 2.8 µg L(-1) was achieved, with an analytical working range of 3-350 µg L(-1), corresponding to 30-3500 µg kg(-1) in maize flour samples, according with the extraction procedure. The time required to perform the analysis was 22 min, including sample preparation. Recovery values in the range from 91.4% to 105.4% with coefficients of variation not exceeding 5% were obtained for fortified and naturally contaminated maize flour samples. To evaluate the possible improvements due to the use of QD for ICST technology, we performed a direct comparison of the proposed QD-ICST to a gold nanoparticles- and a chemiluminescent-ICST previously developed for fumonisins detection, in which the same immunoreagents were employed. Copyright © 2015 Elsevier B.V. All rights reserved.

A Rapid, Onsite, Ultrasensitive Melamine Quantitation Method for Protein Beverages Using Time-Resolved Fluorescence Detection Paper.

Science.gov (United States)

Li, Guanghua; Wang, Du; Zhou, Aijun; Sun, Yimin; Zhang, Qi; Poapolathep, Amnart; Zhang, Li; Fan, Zhiyong; Zhang, Zhaowei; Li, Peiwu