The Experts below are selected from a list of 225 Experts worldwide ranked by ideXlab platform
Manik Pradhan - One of the best experts on this subject based on the ideXlab platform.
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assessing atmospheric co2 entrapped in clay nanotubes using Residual Gas Analyzer
Analytical Chemistry, 2016Co-Authors: Abhijit Maity, Manik Pradhan, Subhra JanaAbstract:A Residual Gas Analyzer (RGA) coupled with a high-vacuum chamber has been explored to measure atmospheric CO2 entrapped in aminosilane-modified clay nanotubes. Ambient CO2 uptake efficacy together with stability of these novel adsorbents composed of both primary and/or secondary amine sites has been demonstrated at standard ambient temperature and pressure. The unprecedented sensitivity and accuracy of the RGA-based mass spectrometry technique toward atmospheric CO2 measurement has been substantiated with a laser-based optical cavity-enhanced integrated cavity output spectroscopy. The adsorption kinetics of atmospheric CO2 on amine-functionalized clay nanotubes followed the fractional-order kinetic model compared to that of the pseudo-first-order or pseudo-second-order rate equations. The efficiency along with stability of these novel adsorbents has also been demonstrated by their repetitive use for CO2 capture in the oxidative environment. Our findings thus point to a fundamental study on the atmospheric...
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non invasive 13c glucose breath test using Residual Gas Analyzer mass spectrometry a novel tool for screening individuals with pre diabetes and type 2 diabetes
Journal of Breath Research, 2014Co-Authors: Chiranjit Ghosh, Abhijit Maity, Gourab Dutta Banik, Shibendu Ghosh, Barnali Ghosh, Arpita Chakraborty, Chitra Selvan, Subhankar Chowdhury, Manik PradhanAbstract:We report, for the first time, the clinical feasibility of a novel Residual Gas Analyzer mass spectrometry (RGA-MS) method for accurate evaluation of the 13C-glucose breath test (13C-GBT) in the diagnosis of pre-diabetes (PD) and type 2 diabetes mellitus (T2D). In T2D or PD, glucose uptake is impaired and results in blunted isotope enriched 13CO2 production in exhaled breath samples. Using the Receiver operating characteristics (ROC) curve analysis, an optimal diagnostic cut-off point of the 13CO2/12CO2 isotope ratios expressed as the delta-over-baseline (DOB) value, was determined to be δDOB13C‰ = 28.81‰ for screening individuals with non-diabetes controls (NDC) and pre-diabetes (PD), corresponding to a sensitivity of 100% and specificity of 94.4%. We also determined another optimal diagnostic cut-off point of δDOB13C‰ = 19.88‰ between individuals with PD and T2D, which exhibited 100% sensitivity and 95.5% specificity. Our RGA-MS methodology for the 13C-GBT also manifested a typical diagnostic positive and negative predictive value of 96% and 100%, respectively. The diagnostic accuracy, precision and validity of the results were also confirmed by high-resolution optical cavity enhanced integrated cavity output spectroscopy (ICOS) measurements. The δDOB13C‰ values measured with RGA-MS method, correlated favourably (R2 = 0.979) with those determined by the laser based ICOS method. Moreover, we observed that the effects of endogenous CO2 production related to basal metabolic rates in individuals were statistically insignificant (p = 0.37 and 0.73) on the diagnostic accuracy. Our findings suggest that the RGA-MS is a valid and sufficiently robust method for the 13C-GBT which may serve as an alternative non-invasive point-of-care diagnostic tool for routine clinical practices as well as for large-scale diabetes screening purposes in real-time.
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Residual Gas Analyzer mass spectrometry for human breath analysis a new tool for the non invasive diagnosis of helicobacter pylori infection
Journal of Breath Research, 2014Co-Authors: Abhijit Maity, Gourab Dutta Banik, Chiranjit Ghosh, Sujit Chaudhuri, Sunil B Daschakraborty, Shibendu Ghosh, Barnali Ghosh, A K Raychaudhuri, Manik PradhanAbstract:A Residual Gas Analyzer (RGA) coupled with a high vacuum chamber is described for the non-invasive diagnosis of the Helicobacter pylori (H. pylori) infection through 13 C-urea breath analysis. The present RGA-based mass spectrometry (MS) method is capable of measuring high-precision 13 CO2 isotope enrichments in exhaled breath samples from individuals harboring the H. pylori infection. The system exhibited 100% diagnostic sensitivity, and 93% specificity alongside positive and negative predictive values of 95% and 100%, respectively, compared with invasive endoscopy-based biopsy tests. A statistically sound diagnostic cut-off value for the presence of H. pylori was determined to be 3.0‰ using a receiver operating characteristic curve analysis. The diagnostic accuracy and validity of the results are also supported by optical off-axis integrated cavity output spectroscopy measurements. The δ 13 DOBC‰ values of both methods correlated well (R 2 = 0.9973 at 30 min). The RGA-based instrumental setup described here is simple, robust, easy-to-use and more portable and cost-effective compared to all other currently available detection methods, thus making it a new point-of-care medical diagnostic tool for the purpose of large-scale screening of the H. pylori infection in real time. The RGA-MS technique should have broad applicability for 13 C-breath tests in a wide range of biomedical research and clinical diagnostics for
W. Buehler - One of the best experts on this subject based on the ideXlab platform.
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Novel method for cleaning a vacuum chamber from hydrocarbon contamination
Journal of Vacuum Science & Technology A: Vacuum Surfaces and Films, 2010Co-Authors: H. D. Wanzenboeck, P. Roediger, Gernot Hochleitner, Emmerich Bertagnolli, W. BuehlerAbstract:A novel method for cleaning a high vacuum chamber is presented. This method is based on concurrent in situ high-energetic UV light activation of contaminants located in the Residual Gas and at the vacuum chamber surfaces as well as the in situ generation of highly reactive ozone. Ozone oxidizes the contaminants to volatile species. Investigations by energy-dispersive x-ray analysis of Residual Gas depositions and mass-spectroscopy measurements of the Residual Gas in the vacuum chamber identify the contaminant species as hydrocarbons. After a cleaning period of 8 h, a decrease in measured chamber contamination by about 90% could be achieved according to atomic force microscope analysis. Mass spectroscopy measurements using a Residual Gas Analyzer indicate the creation of volatile, carbonaceous species during the cleaning process.
Uwe Burghaus - One of the best experts on this subject based on the ideXlab platform.
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Benzene adsorption on Ru(0 0 0 1) and graphene/Ru(0 0 0 1)—How to synthesize epitaxial graphene without STM or LEED?
Chemical Physics Letters, 2013Co-Authors: A. Chakradhar, K. Trettel, Uwe BurghausAbstract:Abstract A simple synthesis and characterization procedure for graphene growth on Ru(0 0 0 1) is demonstrated. Only a sample heating setup and mass spectrometer (or Residual Gas Analyzer) are required. In addition, sample stability at ambient conditions (in air) was tested. Furthermore, benzene adsorption on graphene/Ru(0 0 0 1) was characterized by thermal desorption spectroscopy and compared with earlier experiments and theory on carbon nanotubes and highly-oriented pyrolytic graphite (HOPG). In addition, Auger and X-ray photoelectron spectroscopy were used.
Abhijit Maity - One of the best experts on this subject based on the ideXlab platform.
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assessing atmospheric co2 entrapped in clay nanotubes using Residual Gas Analyzer
Analytical Chemistry, 2016Co-Authors: Abhijit Maity, Manik Pradhan, Subhra JanaAbstract:A Residual Gas Analyzer (RGA) coupled with a high-vacuum chamber has been explored to measure atmospheric CO2 entrapped in aminosilane-modified clay nanotubes. Ambient CO2 uptake efficacy together with stability of these novel adsorbents composed of both primary and/or secondary amine sites has been demonstrated at standard ambient temperature and pressure. The unprecedented sensitivity and accuracy of the RGA-based mass spectrometry technique toward atmospheric CO2 measurement has been substantiated with a laser-based optical cavity-enhanced integrated cavity output spectroscopy. The adsorption kinetics of atmospheric CO2 on amine-functionalized clay nanotubes followed the fractional-order kinetic model compared to that of the pseudo-first-order or pseudo-second-order rate equations. The efficiency along with stability of these novel adsorbents has also been demonstrated by their repetitive use for CO2 capture in the oxidative environment. Our findings thus point to a fundamental study on the atmospheric...
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non invasive 13c glucose breath test using Residual Gas Analyzer mass spectrometry a novel tool for screening individuals with pre diabetes and type 2 diabetes
Journal of Breath Research, 2014Co-Authors: Chiranjit Ghosh, Abhijit Maity, Gourab Dutta Banik, Shibendu Ghosh, Barnali Ghosh, Arpita Chakraborty, Chitra Selvan, Subhankar Chowdhury, Manik PradhanAbstract:We report, for the first time, the clinical feasibility of a novel Residual Gas Analyzer mass spectrometry (RGA-MS) method for accurate evaluation of the 13C-glucose breath test (13C-GBT) in the diagnosis of pre-diabetes (PD) and type 2 diabetes mellitus (T2D). In T2D or PD, glucose uptake is impaired and results in blunted isotope enriched 13CO2 production in exhaled breath samples. Using the Receiver operating characteristics (ROC) curve analysis, an optimal diagnostic cut-off point of the 13CO2/12CO2 isotope ratios expressed as the delta-over-baseline (DOB) value, was determined to be δDOB13C‰ = 28.81‰ for screening individuals with non-diabetes controls (NDC) and pre-diabetes (PD), corresponding to a sensitivity of 100% and specificity of 94.4%. We also determined another optimal diagnostic cut-off point of δDOB13C‰ = 19.88‰ between individuals with PD and T2D, which exhibited 100% sensitivity and 95.5% specificity. Our RGA-MS methodology for the 13C-GBT also manifested a typical diagnostic positive and negative predictive value of 96% and 100%, respectively. The diagnostic accuracy, precision and validity of the results were also confirmed by high-resolution optical cavity enhanced integrated cavity output spectroscopy (ICOS) measurements. The δDOB13C‰ values measured with RGA-MS method, correlated favourably (R2 = 0.979) with those determined by the laser based ICOS method. Moreover, we observed that the effects of endogenous CO2 production related to basal metabolic rates in individuals were statistically insignificant (p = 0.37 and 0.73) on the diagnostic accuracy. Our findings suggest that the RGA-MS is a valid and sufficiently robust method for the 13C-GBT which may serve as an alternative non-invasive point-of-care diagnostic tool for routine clinical practices as well as for large-scale diabetes screening purposes in real-time.
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Residual Gas Analyzer mass spectrometry for human breath analysis a new tool for the non invasive diagnosis of helicobacter pylori infection
Journal of Breath Research, 2014Co-Authors: Abhijit Maity, Gourab Dutta Banik, Chiranjit Ghosh, Sujit Chaudhuri, Sunil B Daschakraborty, Shibendu Ghosh, Barnali Ghosh, A K Raychaudhuri, Manik PradhanAbstract:A Residual Gas Analyzer (RGA) coupled with a high vacuum chamber is described for the non-invasive diagnosis of the Helicobacter pylori (H. pylori) infection through 13 C-urea breath analysis. The present RGA-based mass spectrometry (MS) method is capable of measuring high-precision 13 CO2 isotope enrichments in exhaled breath samples from individuals harboring the H. pylori infection. The system exhibited 100% diagnostic sensitivity, and 93% specificity alongside positive and negative predictive values of 95% and 100%, respectively, compared with invasive endoscopy-based biopsy tests. A statistically sound diagnostic cut-off value for the presence of H. pylori was determined to be 3.0‰ using a receiver operating characteristic curve analysis. The diagnostic accuracy and validity of the results are also supported by optical off-axis integrated cavity output spectroscopy measurements. The δ 13 DOBC‰ values of both methods correlated well (R 2 = 0.9973 at 30 min). The RGA-based instrumental setup described here is simple, robust, easy-to-use and more portable and cost-effective compared to all other currently available detection methods, thus making it a new point-of-care medical diagnostic tool for the purpose of large-scale screening of the H. pylori infection in real time. The RGA-MS technique should have broad applicability for 13 C-breath tests in a wide range of biomedical research and clinical diagnostics for
Fumio Watanabe - One of the best experts on this subject based on the ideXlab platform.
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new measurement method of outGassing speed with a sealed off Residual Gas Analyzer
Journal of The Vacuum Society of Japan, 2008Co-Authors: Fumio WatanabeAbstract:The new measurement method of outGassing speed with a sealed off quadrupole Residual Gas Analyzer (RGA) has been proposed. The unique feature of this method is that the high vacuum can be maintained by the self-pumping effect of the ultra low outGassing RGA. The newly-developed mass Analyzer combined with BA-gauge is the key for this method. The pressure of chamber can be maintained below 2~5×10-7 Pa for a year without any pumping system. The majority of Residual Gases in the chamber were found to be hydrogen, methane and carbon-monoxide. In order to measure the outGassing speed of the RGA, the pumping speeds were measured by the self-pumping effect of RGA for hydrogen, deuterium, methane, nitrogen, carbon-monoxide, carbon-dioxide, oxygen and argon. When the pumping speed of RGA is balanced for outGassing from the RGA itself, we can calculate its value from the partial pressure in the spectrum. Then, we obtain the outGassing speeds for hydrogen=8.8×10-13 Pa m3/s, methane=1.2×10-13 Pa m3/s, carbon-monoxide=1.0×10-13 Pa m3/s.
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investigation and reduction of spurious peaks caused by electron stimulated desorption and outGassing by means of a grid heating method in a hot cathode quadrupole Residual Gas Analyzer
Journal of Vacuum Science and Technology, 2002Co-Authors: Fumio WatanabeAbstract:In the year 2001, two issues remain for extreme high vacuum (XHV) pressure measurements with hot-cathode ionization gauges: measurement limits caused by electron-stimulated desorption (ESD) and outGassing. The limit caused by ESD is significantly clarified and at least partially solved by means of a grid heating method in a Residual Gas Analyzer. After system bakeout and at 10−9 Pa, when the surface of a platinum alloy grid remains contaminated with F and Cl atoms and CO molecules, the mass spectrum is dominated by spurious peaks (which set the measurement limit for a total pressure gauge) caused by ESD species of F, Cl, and O, with a yield of 10−11 (species/electron, with neutral/ion ≅0.3) and by CO molecule ESD, with a yield of 10−11 (species/electron, with CO neutral/O ion ≅18). In this condition, a spurious H peak caused by hydrogen ESD is still low. However, once the grid surface is thoroughly cleaned at over 900 °C by ohmic heating or electron bombardment, the major ESD species observed for both neu...
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low outGassing Residual Gas Analyzer with a beryllium copper alloy flanged ion source
Journal of Vacuum Science and Technology, 1995Co-Authors: Fumio Watanabe, Akinari KasaiAbstract:By using a newly developed beryllium–copper (BeCu)‐alloy ConFlat flange to house the hot‐cathode ion source, a remarkable decrease in the outGassing from a quadrupole Residual Gas Analyzer (RGA) has been achieved. The reduction in outGassing between the new BeCu‐flanged RGA and an ordinary stainless‐steel RGA of otherwise similar design was a factor of 60 or more in the 10−9 Pa total pressure range. From these results, the possibility of high accuracy Residual Gas analysis below 10−9 Pa is introduced.
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Low outGassing Residual Gas Analyzer with a beryllium–copper‐alloy‐flanged ion source
Journal of Vacuum Science and Technology, 1995Co-Authors: Fumio Watanabe, Akinari KasaiAbstract:By using a newly developed beryllium–copper (BeCu)‐alloy ConFlat flange to house the hot‐cathode ion source, a remarkable decrease in the outGassing from a quadrupole Residual Gas Analyzer (RGA) has been achieved. The reduction in outGassing between the new BeCu‐flanged RGA and an ordinary stainless‐steel RGA of otherwise similar design was a factor of 60 or more in the 10−9 Pa total pressure range. From these results, the possibility of high accuracy Residual Gas analysis below 10−9 Pa is introduced.
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Low outGassing Residual Gas Analyzer with a beryllium–copperalloyflanged ion source Low outGassing Residual Gas Analyzer with a beryllium–copper-alloy- flanged ion source
Journal of Vacuum Science & Technology A J. Vac. Sci. Technol. A, 1995Co-Authors: Fumio Watanabe, Akinari KasaiAbstract:Articles you may be interested in The energy loss straggling of low Z ions in solids and Gases AIP Conf. Proc. 1525, 259 (2013); 10.1063/1.4802331 Neutron source images and spectra to guide neutron diagnostics specifications for the National Ignition Facility Rev. Sci. Instrum. 77, 10E722 (2006); 10.1063/1.2351885 Low-frequency phonons in the point-contact spectrum of Mg B 2 Low Temp. Phys. 31, 842 (2005); 10.1063/1.2126943 Recent developments of the ISOLDE laser ion source Rev. Sci. Instrum. 69, 761 (1998); 10.1063/1.1148978 Verylow outGassing rate, separable, aluminumflanged, hotcathode ion source for a Residual Gas Analyzer By using a newly developed beryllium–copper ͑BeCu͒-alloy ConFlat flange to house the hot-cathode ion source, a remarkable decrease in the outGassing from a quadrupole Residual Gas Analyzer ͑RGA͒ has been achieved. The reduction in outGassing between the new BeCu-flanged RGA and an ordinary stainless-steel RGA of otherwise similar design was a factor of 60 or more in the 10 Ϫ9 Pa total pressure range. From these results, the possibility of high accuracy Residual Gas analysis below 10 Ϫ9 Pa is introduced. Today, a quadrupole mass filter with a hot-cathode ion source is most commonly used for Residual Gas Analyzers ͑RGA͒ in ultrahigh vacuum ͑UHV͒ or extreme high vacuum ͑XHV͒ environments. However, the greatest defect of the RGA with a hot-cathode ion source is the very high outGas-sing from the RGA itself. In order to address this problem, an aluminum-alloy-flanged ion source 1 was developed in 1990. The concept was that the lower emissivity of the aluminum wall surrounding the ion source not only absorbed less radia-tion from the hot filament but also decreased the power nec-essary to heat the filament to the prescribed temperature. This was because a large amount of the radiation is reflected back to the filament and hence the filament heating current could be reduced considerably to obtain the necessary emis-sion current, and the high thermal conductivity of aluminum quickly diffused what little heat was absorbed from the fila-ment to the outside of the wall. Moreover, the separable me-chanical construction of the flanged ion source from other parts such as the quadrupole mass filter electrode or the channel electron multiplier ͑CEM͒ reduced heat conduction to these other parts. As a result, very low outGassing for a RGA with a hot-filament ion source was demonstrated.