Precise Gas Research Articles

The low-cost and precise piston gas pressure regulator

The present paper discusses the concept and functioning of an innovative instrument for precise stabilization of gas pressure. The piston gas pressure regulator was constructed at the Strata Mechanics Research Institute of the Polish Academy of Sciences. The tests to which the instrument was subjected involved observing the values of stabilized pressure at the level of 10 bar and 3 bar, for various gas flow rates at the outlet of the instrument. The piston gas pressure regulator operates within the range of 0–10 bar and the gas flow range of 0–240 cm3 min−1. The precision of the process of stabilizing the initial pressure is ±0.005 bar, regardless of the gas pressure value and the flow rate observed at the outlet of the instrument. Although the pressure transducer’s accuracy is 0.25% of the full range, the conducted tests of the regulator demonstrated that the obtained changeability of the stabilized pressure is at least two times lower. Unlike some other gas pressure regulators available on the market, the instrument constructed by the authors of the present paper is highly precise when it comes to the process of stabilization, and inexpensive to build.

Enantiomeric Separation of S-Epichlorohydrin and R-Epichlorohydrin by Capillary Gas Chromatography with FID Detector

The aim of this study was to develop a simple and derivatization free method for the Quantification of S-Epichlorohydrin in R-Epichlorohydrin by using a gas chromatography coupled with flame ionization detector (FID). Enantiopure epichlorohydrin was a valuable epoxide key starting material for preparing optically active Rivaroxaban. The enantiomeric separations of S-Epichlorohydrin and R-Epichlorohydrin were achieved on Gamaa-Dex-225 (30 meters × 0.25 mm I.D, 0.25 μm) column with a total run time of 30 min. Nitrogen was used as a carrier gas with constant pressure 25.0 psi. The critical experimental parameters such as, column selection, flow rate, injection volume and diluent were studied and optimized. Excellent correlation coeffient between peak responses and concentrations was >0.9998. The recoveries of S-Epichlorohydrin spiked in R-Epichlorohydrin were in the range from 98.2% to 102.8%. Limit of quantitation for S-Epichlorohydrin was sufficiently lower than limits specified by ICH. The method has validated as per International Conference on Harmonization (ICH) guidelines. A precise, accurate, linear and robust Gas Chromatography method was developed for the quantification of S-Epichlorohydrin in R-Epichlorohydrin for Rivaroxaban.

Development of a Tubular Solid Oxide Cell for Co-Electrolysis of H2O and CO2 for Syngas Production

A tubular Ni-8YSZ/SSZ/GDC/SSC (Strontium-doped Samarium Cobaltite) cell was prepared for high temperature co-electrolysis of H2O and CO2. This cell enhanced a current density at 750ºC by two-fold compared to a previous type of our cell. Measurements of voltage-current density (V-J) curves revealed that 0.55 A/cm2 was attained at 750ºC and a thermoneutral voltage (1.33 V). The V-J curves were not influenced by change of H2/C (= 2-4) or flow-rate ratio (= 1-4) of positive electrode to negative one. In addition, V-J curve measurement at constant 80% utilization of H2O and CO2 clarified that 0.41 A/cm2 was achieved at the thermoneutral voltage and 750ºC. It was observed by precise gas analyses that gas composition changed in proportion to J and utilization of H2O and CO2. Simultaneously, cross gas-leakages were detected from one electrode to the other.

Fano resonances in plasmonic aluminum nanoparticle clusters for precise gas detection: Ultra-sensitivity to the minor environmental refractive index perturbations

In this study, a compositional molecular cluster of aluminum (Al) nanoparticles (NPs) has been proposed and examined numerically to design efficient and applicable nanoscale plasmonic sensors. Considering the scattering spectral profile of Al/Al2O3 NPs in a decamer orientation that are deposited on a SiO2 substrate with the determined geometrical dimensions, we detected pronounced Fano resonance dip in the UV spectrum. The position and narrowness of the Fano minima in the declared wavelength region have been evaluated for various structural sizes with different oxide layer thicknesses to enhance its quality. Finding the appropriate nanocluster dimensions, we exposed the structure to the presence of various gases with extremely minor differences in refractive indices. The position of Fano minima in the UV spectrum and its depth yields an ability to extremely precise localized surface plasmon resonance (LSPR) sensing in the mentioned spectrum for the subtle environmental variations. Measuring the accuracy of the compositional Al-based decamer, we quantified the corresponding figure of merit (FoM) as 15.24, while the refractive index of the surrounding medium was a variant factor. Ultimately, we proved that the examined structure has a strong potential to exploit in designing precise, CMOS-compatible, and efficient plasmonic subwavelength sensors that are able to detect extremely small perturbations of the ambient. Finite-difference time-domain (FDTD) method is utilized as a numerical method to extract the optical properties of the examined plasmonic subwavelength cluster.

Microfluidic device for analysis of gas-evoked neuronal sensing in C. elegans

It is a challenging task to realize gaseous stimulations on Caenorhabibditis elegans for in vivo neuronal analysis of chemo-sensing, due to the difficulties in gas control and worm manipulation. Here, we demonstrated an integrated microfluidic system that could accurately deliver the gaseous stimuli to the worms’ noses and track the in vivo neuronal activities simultaneously. The microfluidic chip consisted of a comb-shaped micro-valve for worm immobilization and a T-junction structure for precise gas delivery. Neuronal responses of C. elegans to polar and non-polar gases were both investigated. The microfluidic device clearly demonstrated that oxygen with increasing levels of 0–10% and 0–21% induced URX neuronal responses. BAG neuronal activities were inhibited by carbon dioxide, showing the symptom of anesthesia. The vapor of polar odorant 1-octonal evoked significant calcium transients in ASH neurons in the wild-type animals but weak signals in tph-1 and Ce-grk-2 mutants. These results indicated that the developed device could be useful to identify various odor-evoked neuronal activities.

Fuzzy Modeling and Experimental Investigation of Minimum Miscible Pressure in Gas Injection Process

Knowledge about miscibility of injected gas in reservoir oils has a vital importance in gas injection process in petroleum reservoirs for enhanced oil recovery (EOR) goals. In other words, miscibility of the injected gas is highly depends on injection pressure and restriction of injection facilities. Thanks to these facts, minimum value of miscibility pressure should be specified accurately. To pass successfully the aforementioned issue, fuzzy logic method was utilized to specify minimum miscible pressure (MMP) of injected gas and reservoir oil. Moreover, different type of membership functions have been implemented such as curve shaped, triangular and trapezoidal shape. A large data banks which reported in open literature have been used in order to specify performance, deviations and precision of the developed fuzzy logic approaches. Furthermore, slim tube experiments have done on four different crude oil samples to determine their MMP values in contact with gas. Also, experimental results of this research have been matched accurately with corresponding outcomes of fuzzy logic approaches in comparison with conventional methods. According to the results gained from this research on the basis of statistical parameters, curve-shape membership function has higher superiority than other executed types of membership function. Outcomes of present work could be utilized for designing more precise, accurate and assured gas injection process by means of miscible displacement.

A rugged, high precision capacitance diaphragm low pressure gauge for cryogenic use

In order to carry out precise laboratory measurements of infrared absorption intensities, line profiles of molecules and organic volatile compounds for atmospheric chemistry in planetary and upper earth atmospheric layers, precise gas pressure measurement between 10(-3) and a few mbars in the 77-300 K temperature range is necessary. A prototype, rugged, precision capacitive pressure gauge for cryogenic use has been designed, built at SOLEIL and tested down to 77 K. The design includes corrosion-resistant materials and has been tailored to operate on a differential measurement scheme based on a simple, precision capacitance-to-digital converter chip, instead of high precision floating capacitive bridges, as are used in other designs. The designs conception and performance specifications are presented here, illustrated by a precision of better than 1% in the 0.2-40 mbar range, with a resolution of 2 × 10(-3) mbar. The gauge is tunable and can be adjusted for higher precision and a better resolution, at the expense of the maximum high-pressure range.

MEMS based normally closed silicon microregulator for gas and water

This paper presents the design, fabrication and performance evaluation of a normally closed piezoelectrically actuated silicon microregulator. The microregulator is realized using two wafers process and is designed for the maximum operating pressure 5bar and it is found to be leak proof (1×10−4sccm of helium gas).This paper also reports the development of precision fixturing, assembling and testing of the valve. One of the potential areas for application of microregulators is in satellite propulsion using ion thrusters. Ion thrusters require feed systems with very precise propellant gas flow rate and it makes microregulator a suitable candidate. Another application of the microregulator is liquid propellant flow control in micropropulsion. The water flow measurement of the same microregulator is discussed here. The hysteresis measurement of the silicon membrane using inductive probe and the cyclic test of the microregulator are also described here.

Standards and Traceability for Air Quality Measurements: Flow Rates and Gaseous Pollutants

Accurate and precise flow rate and gas concentration measurement standards are needed for comparable air quality measurements. Transfer standards are most often used for calibration, performance testing, and auditing of field monitors. These must be traceable to primary standards that are in turn derived from fundamental units of length, mass, temperature, and time. Flow rates and volumes are measured by devices based on positive displacement, pressure differences, and temperature increases or decreases. Stable gas concentrations are prepared in non-reactive pressurized containers by gravimetric and dilution methods. Reactive gases are generated from photochemistry and permeation devices. These standards are used to determine the accuracy, precision, and validity of air quality measurements, and these attributes should be reported with the measurement values.

Assessment of a multi-species in situ FTIR for precise atmospheric greenhouse gas observations

Abstract. We thoroughly evaluate the performance of a multi-species, in situ Fourier transform infrared (FTIR) analyser with respect to high-accuracy needs for greenhouse gas monitoring networks. The in situ FTIR analyser is shown to measure CO2, CO, CH4 and N2O mole fractions continuously, all with better reproducibility than the inter-laboratory compatibility (ILC) goals, requested by the World Meteorological Organization (WMO) for the Global Atmosphere Watch (GAW) programme. Simultaneously determined δ13CO2 reaches reproducibility as good as 0.03‰. Second-order dependencies between the measured components and the thermodynamic properties of the sample, (temperature, pressure and flow rate) and the cross sensitivities among the sample constituents are investigated and quantified. We describe an improved sample delivery and control system that minimises the pressure and flow rate variations, making post-processing corrections for those quantities non-essential. Temperature disequilibrium effects resulting from the evacuation of the sample cell are quantified and improved by the usage of a faster temperature sensor. The instrument has proven to be linear for all measured components in the ambient concentration range. The temporal stability of the instrument is characterised on different time scales. Instrument drifts on a weekly time scale are only observed for CH4 (0.04 nmol mol−1 day−1) and δ13CO2 (0.02‰ day−1). Based on 10 months of continuously collected quality control measures, the long-term reproducibility of the instrument is estimated to ±0.016 μmol mol−1 CO2, ±0.03‰ δ13CO2, ±0.14 nmol mol−1 CH4, ±0.1 nmol mol−1 CO and ±0.04 nmol mol−1 N2O. We propose a calibration and quality control scheme with weekly calibrations of the instrument that is sufficient to reach WMO-GAW inter-laboratory compatibility goals.

High accuracy measurements of dry mole fractions of carbon dioxide and methane in humid air

Abstract. Traditional techniques for measuring the mole fractions of greenhouse gases in the well-mixed atmosphere have required dry sample gas streams (dew point < −25 °C) to achieve the inter-laboratory compatibility goals set forth by the Global Atmosphere Watch programme of the World Meteorological Organisation (WMO/GAW) for carbon dioxide (±0.1 ppm in the Northern Hemisphere and ±0.05 ppm in the Southern Hemisphere) and methane (±2 ppb). Drying the sample gas to low levels of water vapour can be expensive, time-consuming, and/or problematic, especially at remote sites where access is difficult. Recent advances in optical measurement techniques, in particular cavity ring down spectroscopy, have led to the development of greenhouse gas analysers capable of simultaneous measurements of carbon dioxide, methane and water vapour. Unlike many older technologies, which can suffer from significant uncorrected interference from water vapour, these instruments permit accurate and precise greenhouse gas measurements that can meet the WMO/GAW inter-laboratory compatibility goals (WMO, 2011a) without drying the sample gas. In this paper, we present laboratory methodology for empirically deriving the water vapour correction factors, and we summarise a series of in-situ validation experiments comparing the measurements in humid gas streams to well-characterised dry-gas measurements. By using the manufacturer-supplied correction factors, the dry-mole fraction measurements have been demonstrated to be well within the GAW compatibility goals up to a water vapour concentration of at least 1%. By determining the correction factors for individual instruments once at the start of life, this water vapour concentration range can be extended to at least 2% over the life of the instrument, and if the correction factors are determined periodically over time, the evidence suggests that this range can be extended up to and even above 4% water vapour concentrations.

Technical Note: A simple method for air–sea gas exchange measurements in mesocosms and its application in carbon budgeting

Abstract. Mesocosms as large experimental units provide the opportunity to perform elemental mass balance calculations, e.g. to derive net biological turnover rates. However, the system is in most cases not closed at the water surface and gases exchange with the atmosphere. Previous attempts to budget carbon pools in mesocosms relied on educated guesses concerning the exchange of CO2 with the atmosphere. Here, we present a simple method for precise determination of air–sea gas exchange in mesocosms using N2O as a deliberate tracer. Beside the application for carbon budgeting, transfer velocities can be used to calculate exchange rates of any gas of known concentration, e.g. to calculate aquatic production rates of climate relevant trace gases. Using an arctic KOSMOS (Kiel Off Shore Mesocosms for future Ocean Simulation) experiment as an exemplary dataset, it is shown that the presented method improves accuracy of carbon budget estimates substantially. Methodology of manipulation, measurement, data processing and conversion to CO2 fluxes are explained. A theoretical discussion of prerequisites for precise gas exchange measurements provides a guideline for the applicability of the method under various experimental conditions.

In-Line Calibration of Raman Systems for Analysis of Gas Mixtures of Hydrogen Isotopologues with Sub-Percent Accuracy

Highly accurate, in-line, and real-time composition measurements of gases are mandatory in many processing applications. The quantitative analysis of mixtures of hydrogen isotopologues (H2, D2, T2, HD, HT, and DT) is of high importance in such fields as DT fusion, neutrino mass measurements using tritium β-decay or photonuclear experiments where HD targets are used. Raman spectroscopy is a favorable method for these tasks. In this publication we present a method for the in-line calibration of Raman systems for the nonradioactive hydrogen isotopologues. It is based on precise volumetric gas mixing of the homonuclear species H2/D2 and a controlled catalytic production of the heteronuclear species HD. Systematic effects like spurious exchange reactions with wall materials and others are considered with care during the procedure. A detailed discussion of statistical and systematic uncertainties is presented which finally yields a calibration accuracy of better than 0.4%.

Molecular design and physical properties of highly functionalized configurationally locked polyenes – an experimental and theoretical study

This paper reports for the first time the molecular design, synthesis and a correlation study on the structure and physical properties of highly functionalized configurationally locked polyenes considered as broadband THz materials ∈ 0.3–30 THz, thus extending the ability of THz-spectroscopy to identify materials for the mid-IR region. The effects of the seven types of substituents replacing the malononitrile residue on theoretical first and second hyperpolarizabilities are discussed. The promising candidates among the 140 model designed molecules showed hyperpolarizabilities (βtot) with magnitudes 4 to 11.5 times higher than the values of 2-(3-(4-hydroxystyryl)-5,5-dimethylcyclohex-2-enylidene)malononitrile (OH1), described as a standard organic THz-material which has already been applied in THz-spectrometers. The 70 derivatives are successfully isolated, 21 of which at yields ∈ 17.4–99.7% (1–21) suitable for further experimental efforts towards their single crystal growth and related physical measurements. 48 other dyes are characterized with synthetic yields ∈ 1.7–16.2%, respectively. Therefore, the search for new strategies to optimize the synthesis procedure is of high importance. The isolated derivatives are characterized by electronic absorption and fluorescence spectroscopy, and an evaluation of the theoretical and experimental hyperpolarizabilities caused by the charge transfer effect (βCT) is performed. A primary focus of the discussion at this stage of the presented promising data is on mass spectrometry, due to: (i) its instrumental flexibility, ultra high resolution and ability for accurate and precise gas- and condensed phase analysis within a wide temperature range, and the various ionization methods, making mass spectrometry an irreplaceable physical method in synthetic organic chemistry; (ii) the variety of sampling techniques for structural analysis of liquid and semiliquid homogeneous and heterogeneous systems, 1D–3D crystals, powders, solid thin films, and polymers; and (iii) imaging studies.

A Conserved UDP-Glucose Dehydrogenase Encoded outside the hasABC Operon Contributes to Capsule Biogenesis in Group A Streptococcus

Group A Streptococcus (GAS) is a human-specific bacterial pathogen responsible for serious morbidity and mortality worldwide. The hyaluronic acid (HA) capsule of GAS is a major virulence factor, contributing to bloodstream survival through resistance to neutrophil and antimicrobial peptide killing and to in vivo pathogenicity. Capsule biosynthesis has been exclusively attributed to the ubiquitous hasABC hyaluronan synthase operon, which is highly conserved across GAS serotypes. Previous reports indicate that hasA, encoding hyaluronan synthase, and hasB, encoding UDP-glucose 6-dehydrogenase, are essential for capsule production in GAS. Here, we report that precise allelic exchange mutagenesis of hasB in GAS strain 5448, a representative of the globally disseminated M1T1 serotype, did not abolish HA capsule synthesis. In silico whole-genome screening identified a putative HasB paralog, designated HasB2, with 45% amino acid identity to HasB at a distant location in the GAS chromosome. In vitro enzymatic assays demonstrated that recombinant HasB2 is a functional UDP-glucose 6-dehydrogenase enzyme. Mutagenesis of hasB2 alone slightly decreased capsule abundance; however, a ΔhasB ΔhasB2 double mutant became completely acapsular. We conclude that HasB is not essential for M1T1 GAS capsule biogenesis due to the presence of a newly identified HasB paralog, HasB2, which most likely resulted from gene duplication. The identification of redundant UDP-glucose 6-dehydrogenases underscores the importance of HA capsule expression for M1T1 GAS pathogenicity and survival in the human host.

DATA ACQUISITION SYSTEM FOR ARC-DRIVEN HF/DF CHEMICAL LASERS

The article focuses on the development of a data acquisition system (DAS) working in a noisy and hostile environment for an arc-operated hydrogen fluoride/deuterium fluoride (HF/DF) chemical laser. PC-based DAS has been configured using Advantech plug and play modules with fiber link connectivity. This article also focuses on implementation of an orifice-based precise gas flow control system. The plasma arc discharge in an arc heater/generator is essentially employed for inducing thermal dissociation of sulfur hexafluoride SF6 for production of fluorine atoms, and DAS has been used for performance optimization of the composition of the lasing mixture by independently varying the flow rate, pressure, and temperature of its constituents. Since arc load is complex with high voltage transients and electromagnetic noise, an optical fiber link has been implemented for data transmission. This article also discusses digital output interface circuitry for various electro-pneumatic actuators/solenoid valves. The developed DAS has been used for monitoring and performance evaluation of parameters for 50 kW arc tunnel.

Evaluation of Current Efficiency of SOEC Using Precise On-Line Gas Analysis

not Available.

Advances in Embryo Culture Systems

The growth of mammalian embryos in the laboratory has progressed nicely over the last 60 to 70 years. This has been important for basic studies of preimplantation embryo regulation of growth, development, and differentiation. It has also been critical for the establishment of assisted reproductive technologies in the clinical setting to treat infertility. During the first 40 to 50 years, the primary focus was on defining soluble media components, which fortunately has yielded improved success in the culture of embryos. More recently, attention has shifted to other aspects of culture beyond media composition. In this review we discuss recent advances in preimplantation embryo culture that deal with modifying the insoluble culture environment, producing culture environments that are dynamic and not static, systems that allow more precise gas phase and/or media pH regulation/monitoring, and platforms that integrate with culture systems to allow analysis of embryos and thus assist in selection of the embryos with the greatest implantation potential.

Quantifying in-situ gas hydrates at active seep sites in the eastern Black Sea using pressure coring technique

Abstract. In the eastern Black Sea, we determined methane (CH4) concentrations, gas hydrate volumes, and their vertical distribution from combined gas and chloride (Cl−) measurements within pressurized sediment cores. The total gas volume collected from the cores corresponded to concentrations of 1.2–1.4 mol CH4 kg−1 porewater at in-situ pressure, which is equivalent to a gas hydrate saturation of 15–18% of pore volume and amongst the highest values detected in shallow seep sediments. At the central seep site, a high-resolution Cl− profile resolved the upper boundary of gas hydrate occurrence and a continuous layer of hydrates in a sediment column of 120 cm thickness. Including this information, a more precise gas hydrate saturation of 22–24% pore volume could be calculated. This volume was higher in comparison to a saturation calculated from the Cl− profile alone, resulting in only 14.4%. The likely explanation is an active gas hydrate formation from CH4 gas ebullition. The hydrocarbons at Batumi Seep are of shallow biogenic origin (CH4 > 99.6%), at Pechori Mound they originate from deeper thermocatalytic processes as indicated by the lower ratios of C1 to C2–C3 and the presence of C5.

Determination of Tramadol by Capillary GC-FID and a study of postmortem distribution in rats

A rapid, precise and accurate capillary gas chromatographic assay with flame ionization detection (GC-FID) was developed for the determination of tramadol (TMD) in biological samples. It is comprised of liquid extraction procedure with mixture (2:3, V dichloromethane /V ether ) at pH 11.15 and gas chromatography with SHIMADZU GC-14C. The recoveries of TMD and SKF 525A (internal standard) were in the range of 98.5-106.2% and at an average of 103.8%. Calibration graphs were linear over the concentration range of 5.0-400.0 μg/mL and 5.0-400.0 μg/g with coefficient of variation as (0.9-3.1% (within-day) and 1.4-5.5% (between-days)). The limits of detection were 0.01 μg/mL in plasma and urine and 0.01 μg/g in liver based on signal- to-noise ratio of 3. We also investigated the distribution of TMD in acute poisoned rats after oral administration at 1140 mg/kg of TMD (5×LD 50 ), and determined the average concentration in heart blood, peripheral blood, urine, vitreous humor, heart, lung, liver, spleen, kidney and brain, respectively. We concluded that the concentration of TMD in heart blood and liver is much higher compared to other body fluids and organs. Thus, blood and urine are suitable samples for forensic toxicological analysis. This developing analysis method and postmortem-distribution study can be potentially useful in forensic drug testing.