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Spas D. Kolev - One of the best experts on this subject based on the ideXlab platform.
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A gas-Diffusion Flow injection method coupled with online solid-liquid extraction for the determination of ammonium in solid samples.
Talanta, 2015Co-Authors: Irina Timofeeva, Andrey Bulatov, Aleksey L. Moskvin, Spas D. KolevAbstract:Abstract A simple, rapid and reliable gas-Diffusion Flow injection (GD-FI) method for ammonium determination in building materials has been developed. It is based on leaching ammonium from a ground solid sample into an alkaline solution with subsequent ammonia gas generation. Ammonia is then transported in a nitrogen stream to the GD cell of the FI system where it is absorbed into its acceptor solution containing a mixture of the acid–base indicators cresol red and thymol blue. The maximum increase in the absorbance of the acceptor solution at 580 nm is related to the ammonium concentration in the solid sample. The proposed method is characterized by a linear concentration range of 0.1–5.0 mg NH 4 + kg−1, a limit of detection of 8 μg NH 4 + kg−1 and a sample throughput of 10 h−1. A successful application of this method for the determination of ammonium in building materials such as concrete, cement and sand is reported.
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Determination of acetaldehyde in saliva by gas-Diffusion Flow injection analysis.
Analytica chimica acta, 2013Co-Authors: Adlin N. Ramdzan, Patrick J Mornane, Michael Mccullough, Waldemar Mazurek, Spas D. KolevAbstract:The consumption of ethanol is known to increase the likelihood of oral cancer. In addition, there has been a growing concern about possible association between long term use of ethanol-containing mouthwashes and oral cancer. Acetaldehyde, known to be a carcinogen, is the first metabolite of ethanol and it can be produced in the oral cavity after consumption or exposure to ethanol. This paper reports on the development of a gas-Diffusion Flow injection method for the online determination of salivary acetaldehyde by its colour reaction with 3-methyl-2-benzothiazolinone hydrazone (MBTH) and ferric chloride. Acetaldehyde samples and standards (80 μL) were injected into the donor stream containing NaCl from which acetaldehyde diffused through the hydrophobic Teflon membrane of the gas-Diffusion cell into the acceptor stream containing the two reagents mentioned above. The resultant intense green coloured dye was monitored spectrophotometrically at 600 nm. Under the optimum working conditions the method is characterized by a sampling rate of 9h(-1), a linear calibration range of 0.5-15 mg L(-1) (absorbance=5.40×10(-2) [acetaldehyde, mg L(-1)], R(2)=0.998), a relative standard deviation (RSD) of 1.90% (n=10, acetaldehyde concentration of 2.5 mg L(-1)), and a limit of detection (LOD) of 12.3 μg L(-1). The LOD and sampling rate of the proposed method are superior to those of the conventional gas chromatographic (GC) method (LOD=93.0 μg L(-1) and sampling rate=4 h(-1)). The reliability of the proposed method was illustrated by the fact that spiked with acetaldehyde saliva samples yielded excellent recoveries (96.6-101.9%), comparable to those obtained by GC (96.4-102.3%) and there was no statistically significant difference at the 95% confidence level between the two methods when non-spiked saliva samples were analysed.
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Online ligand exchange in the determination of weak acid dissociable cyanide by gas Diffusion-Flow injection analysis
Microchemical Journal, 2013Co-Authors: Hermin Sulistyarti, Spas D. KolevAbstract:Abstract A novel ligand exchange method for on-line gas-Diffusion Flow injection (GD-FI) determination of weak acid dissociable (WAD) cyanide has been successfully developed using a binary ligand combination of 0.10% thiourea and 0.10% pentaethylenehexamine. Complete WAD cyanide recovery with insignificant contribution from the dissociation of stable metal cyanide complexes (non-WAD complexes) has been achieved in the concentration range from 3 μg L − 1 to 10 mg L − 1 cyanide. The proposed GD-FI method offers considerable advantages over the existing standard methods for determining WAD cyanide, as it provides an analysis rate of 60 samples h − 1 with a satisfactory reproducibility (average RSD = 1.0% at n = 3) and can be fully automated. A very good agreement between the proposed method and the standard distillation method has been observed when both methods have been applied to the determination of WAD cyanide in samples from the gold mining industry.
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Sensitive and ultra-fast determination of arsenic(III) by gas-Diffusion Flow injection analysis with chemiluminescence detection.
Analytica chimica acta, 2006Co-Authors: Cristina Lomonte, Ian D. Mckelvie, Matthew Currell, Richard J. S. Morrison, Spas D. KolevAbstract:Abstract A novel chemiluminescence gas-Diffusion Flow injection system for the determination of arsenic(III) in aqueous samples is described. The analytical procedure involves injection of arsenic(III) samples and standards into a 0.3 mol L−1 hydrochloric acid carrier stream which is merged with a reagent stream containing 0.2% (w/v) sodium borohydride and 0.015 mol L−1 sodium hydroxide. Arsine, generated in the combined carrier/reagent donor stream, diffuses across the hydrophobic Teflon membrane of the gas-Diffusion cell into an argon acceptor stream and then reacts with ozone in the Flow-through chemiluminescence measuring cell of the Flow system. Under optimal conditions, the method is characterized by a wide linear calibration range from 0.6 μg L−1 to 25 mg L−1, a detection limit of 0.6 μg L−1 and a sample throughput of 300 samples per hour at 25 mg L−1 and 450 samples per hour at 25 μg L−1.
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Gas-Diffusion Flow injection determination of Hg(II) with chemiluminescence detection
Analytica chimica acta, 2006Co-Authors: Nazanin Amini, Spas D. KolevAbstract:Abstract A gas-Diffusion Flow injection method for the chemiluminescence detection of Hg(II) based on the luminol–H 2 O 2 reaction was developed. The analytical procedure involved the injection of Hg(II) samples and standards into a 1.50 M H 2 SO 4 carrier stream, which was subsequently merged with a reagent stream of 0.60% (w/v) SnCl 2 in 1.50 M H 2 SO 4 to reduce Hg(II) to metallic Hg. The gas-Diffusion cell was thermostated at 85 °C to enhance the vaporisation of metallic Hg. Mercury vapour, transported across the Teflon membrane of the gas-Diffusion cell into the acceptor stream containing 1.00 × 10 −4 M KMnO 4 in 0.30 M H 2 SO 4 , was oxidised back to Hg(II). The acceptor stream was merged with a reagent stream containing 2.50 M H 2 O 2 in deionised water and then the combined stream was merged with another reagent stream containing 7.50 × 10 −3 M luminol in 3.00 M NaOH at a confluence point opposite to the photomultiplier tube of the detection system. The chemiluminescence intensity of the luminol–H 2 O 2 reaction was enhanced by the presence of Hg(II) in the acceptor stream. The corresponding increase was related to the original concentration of Hg(II) in the samples and standards. Under optimal conditions, the chemiluminescence gas-Diffusion Flow injection method was characterised by a linear calibration range between 1 μg L −1 and 100 μg L −1 , a detection limit of 0.8 μg L −1 and a sampling rate of 12 samples per hour. It was successfully applied to the determination of mercury in seawater and river samples.
Tateo Saito - One of the best experts on this subject based on the ideXlab platform.
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Modified Thermal Diffusion Flow Probe for the Continuous Monitoring of Cortical Blood Flow
Neurosurgery, 1991Co-Authors: Naoya Kuwayama, Akira Takaku, Jun Harada, Osamu Fukuda, Shunro Endo, Tateo SaitoAbstract:Abstract A small thermal Diffusion Flow probe has been developed to monitor the dynamic changes in cerebral blood Flow in small animals. Constantan wire was used as a heat source to make a miniature probe. The pair of thermocouples used to detect the heat gradient between two gold plates was elongated to avoid heat conduction between them, and this improvement allowed us to make quantitative measurements. After several basic experiments, local cerebral blood Flow was measured simultaneously, using both the modified thermal probe and the hydrogen clearance method in four rabbits. A close relationship was obtained between the local cerebral blood Flow values measured by hydrogen clearance (F, ml/100g/min) and the reciprocal of the thermocouple voltage (1/V;1/mV). The regression line was F = 29111(1/V- 1/226), (r = 0.92, P<0.001). We suggest that the modified thermal probe is a reliable and quantitative means of measuring Flow. In addition, another probe modified for clinical use was evaluated. Continuous monitoring of local cerebral blood Flow in postoperative patients was performed, and some illustrative cases are described.
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Modified thermal Diffusion Flow probe for the continuous monitoring of cortical blood Flow.
Neurosurgery, 1991Co-Authors: Naoya Kuwayama, Akira Takaku, Jun Harada, Osamu Fukuda, Shunro Endo, Tateo SaitoAbstract:A small thermal Diffusion Flow probe has been developed to monitor the dynamic changes in cerebral blood Flow in small animals. Constantan wire was used as a heat source to make a miniature probe. The pair of thermocouples used to detect the heat gradient between two gold plates was elongated to avoid heat conduction between them, and this improvement allowed us to make quantitative measurements. After several basic experiments, local cerebral blood Flow was measured simultaneously, using both the modified thermal probe and the hydrogen clearance method in four rabbits. A close relationship was obtained between the local cerebral blood Flow values measured by hydrogen clearance (F, ml/100g/min) and the reciprocal of the thermocouple voltage (1/V;1/mV). The regression line was F = 29111(1/V - 1/226), (r = 0.92, P less than 0.001). We suggest that the modified thermal probe is a reliable and quantitative means of measuring Flow. In addition, another probe modified for clinical use was evaluated. Continuous monitoring of local cerebral blood Flow in postoperative patients was performed, and some illustrative cases are described.
Massimiliano Morini - One of the best experts on this subject based on the ideXlab platform.
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The Surface Diffusion Flow with Elasticity in Three Dimensions
Archive for Rational Mechanics and Analysis, 2020Co-Authors: Nicola Fusco, Vesa Julin, Massimiliano MoriniAbstract:We establish the short-time existence of a smooth solution to the surface Diffusion equation with an elastic term and without an additional curvature regularization in three space dimensions. We also prove the asymptotic stability of strictly stable stationary sets.
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The surface Diffusion Flow with elasticity in three dimensions
arXiv: Analysis of PDEs, 2018Co-Authors: Nicola Fusco, Vesa Julin, Massimiliano MoriniAbstract:We establish short-time existence of a smooth solution to the surface Diffusion equation with an elastic term and without an additional curvature regularization in three space dimensions. We also prove the asymptotic stability of strictly stable stationary sets.
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The Surface Diffusion Flow with Elasticity in the Plane
Communications in Mathematical Physics, 2018Co-Authors: Nicola Fusco, Vesa Julin, Massimiliano MoriniAbstract:In this paper we prove short-time existence of a smooth solution in the plane to the surface Diffusion equation with an elastic term and without an additional curvature regularization. We also prove the asymptotic stability of strictly stable stationary sets.
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Nonlinear stability results for the modified Mullins-Sekerka and the surface Diffusion Flow
arXiv: Analysis of PDEs, 2016Co-Authors: Emilio Acerbi, Nicola Fusco, Vesa Julin, Massimiliano MoriniAbstract:It is shown that any three-dimensional periodic configuration that is strictly stable for the area functional is exponentially stable for the surface Diffusion Flow and for the Mullins-Sekerka or Hele-Shaw Flow. The same result holds for three-dimensional periodic configurations that are strictly stable with respect to the sharp-interface Ohta-Kawaski energy. In this case, they are exponentially stable for the so-called modified Mullins-Sekerka Flow.
Naoya Kuwayama - One of the best experts on this subject based on the ideXlab platform.
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Modified Thermal Diffusion Flow Probe for the Continuous Monitoring of Cortical Blood Flow
Neurosurgery, 1991Co-Authors: Naoya Kuwayama, Akira Takaku, Jun Harada, Osamu Fukuda, Shunro Endo, Tateo SaitoAbstract:Abstract A small thermal Diffusion Flow probe has been developed to monitor the dynamic changes in cerebral blood Flow in small animals. Constantan wire was used as a heat source to make a miniature probe. The pair of thermocouples used to detect the heat gradient between two gold plates was elongated to avoid heat conduction between them, and this improvement allowed us to make quantitative measurements. After several basic experiments, local cerebral blood Flow was measured simultaneously, using both the modified thermal probe and the hydrogen clearance method in four rabbits. A close relationship was obtained between the local cerebral blood Flow values measured by hydrogen clearance (F, ml/100g/min) and the reciprocal of the thermocouple voltage (1/V;1/mV). The regression line was F = 29111(1/V- 1/226), (r = 0.92, P<0.001). We suggest that the modified thermal probe is a reliable and quantitative means of measuring Flow. In addition, another probe modified for clinical use was evaluated. Continuous monitoring of local cerebral blood Flow in postoperative patients was performed, and some illustrative cases are described.
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Modified thermal Diffusion Flow probe for the continuous monitoring of cortical blood Flow.
Neurosurgery, 1991Co-Authors: Naoya Kuwayama, Akira Takaku, Jun Harada, Osamu Fukuda, Shunro Endo, Tateo SaitoAbstract:A small thermal Diffusion Flow probe has been developed to monitor the dynamic changes in cerebral blood Flow in small animals. Constantan wire was used as a heat source to make a miniature probe. The pair of thermocouples used to detect the heat gradient between two gold plates was elongated to avoid heat conduction between them, and this improvement allowed us to make quantitative measurements. After several basic experiments, local cerebral blood Flow was measured simultaneously, using both the modified thermal probe and the hydrogen clearance method in four rabbits. A close relationship was obtained between the local cerebral blood Flow values measured by hydrogen clearance (F, ml/100g/min) and the reciprocal of the thermocouple voltage (1/V;1/mV). The regression line was F = 29111(1/V - 1/226), (r = 0.92, P less than 0.001). We suggest that the modified thermal probe is a reliable and quantitative means of measuring Flow. In addition, another probe modified for clinical use was evaluated. Continuous monitoring of local cerebral blood Flow in postoperative patients was performed, and some illustrative cases are described.
Avat Arman Taherpour - One of the best experts on this subject based on the ideXlab platform.
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Theoretical study of Diffusion Flow of anticancer medicines through single-wall armchair (10, 10) carbon nanotube
2019Co-Authors: Avat Arman Taherpour, Azar Hassani Daramroudi, Rojin KariminyaAbstract:Cancer is one of the most challenging diseases for the reason that its therapy involves distinguishing normal healthy cells from affected cells. Carbon nanotubes (CNTs) play an important role in cancer therapy because of their unique properties. This study theoretically illustrates Diffusion Flow of anticancer medicines through single-wall armchair (10, 10) CNTs to investigate the possibility of using them in drug delivery. To investigate the movement of polyatomic molecular species through CNTs, the Diffusion Flow of anticancer medicines (Carmustine, Lomustine, Ifosfamide, Azathioprine, Gemcitabine, Procarbazine, Methotrexate) were modeled through single-wall armchair(10,10) CNTs. The selected method was Semi-empirical/PM6 to optimize the anticancer medicines and molecular mechanics (MMFF94 method) to optimize the selected CNT in this modeling. The different aspects were considered and discussed.
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Theoretical Study of Diffusion Flow of Neurotransmitters Through Single-Wall Armchair(10,10) and Zigzag(18,0) Carbon Nanotubes
Iranian Journal of Science and Technology Transactions A: Science, 2016Co-Authors: Avat Arman Taherpour, Fatemeh JahanianAbstract:Neurotransmitters are the compounds which allow the transmission of signals from one neuron to the next across synapses. They are brain chemicals that communicate information throughout brain and body. Theoretically, the Diffusion Flow of neurotransmitters through the Armchair(10,10) and Zigzag(18,0) carbon nanotubes facilitate the possibility of neurotransmitters sampling from the neuron synapses (in neurochemistry) to determine the changes of these important compounds in diseases. Theoretically, considering the dimensions of the selected single-wall carbon nanotubes (SWCNT), it is possible to use SWCNT for neurotransmitters sampling in neuron synapses appropriate positions. To investigate the movement of polyatomic molecular species through carbon nanotubes, the Diffusion Flow of neurotransmitters (epinephrine, acetylcholine, norepinephrine, serotonin and dopamine) molecules were modeled through single-walled carbon nanotubes [Armchair(10,10) and Zigzag(18,0)] while in this modeling, the study of the dynamic Flow is done with the nanometer-scale analogue of macroscopic scale fluid Flow through pipes. The selected method was B3LYP/6-31G* to optimize the neurotransmitters (epinephrine, acetylcholine, norepinephrine, serotonin, and dopamine 1–5) and MMFF94 method (molecular mechanics) included the same diameters and lengths of nanotubes and helical structures in this modeling. Different aspects were considered and discussed.