Search results for "Mass fraction"
showing 10 items of 37 documents
Optimization of sample preparation conditions for detecting trace amounts of β-tegafur in α- and β-tegafur mixture.
2012
We report a semiquantitative method for determining trace amounts (<1%) of thermodynamically stable forms in polymorphic mixtures, focusing on sample preparation ef- fects on solid phase transitions. Tegafur (5-fluoro-1-(oxolan-2-yl)-1,2,3,4-tetrahydropyrimidine- 2,4-dione) was used as a model material in this study. The amounts of the thermodynamically stable $ tegafur were increased to levels detectable by powder X-ray diffractometry by grind- ing the samples in a ball mill in the presence of water. The limit of detection for this method was as low as 0.0005% of $ tegafur in " and $ tegafur mixtures. The amount of $ tegafur after sample preparation was found to be proportional to the init…
Major and Trace Element Geochemistry of the European Kupferschiefer – An Evaluation of Analytical Techniques
2018
Simple and rapid techniques are needed for routine quantitative chemical bulk-rock analyses of Kupferschiefer, a black shale containing variable amounts of silicates, base metal sulphides, carbonates and an organic content of up to 30 weight percent. In this study, WD-XRF, TXRF, and ICP-OES of acid- as well as peroxide-digested samples were tested as potential techniques based on their availability and adaptability to analyse major (Si, Ti, Al, Mg, Ca, Fe, K, but also Cu, Zn, Pb) and selected trace (Ag, As, Ba, Co, Mo, Ni, V) element concentrations. Because of the absence of a suitable reference material, a comparative study was undertaken using instrumental neutron activation analysis to a…
A phenomenological model for the quantitative interpretation of partial suspension conditions in stirred vessels
2000
Publisher Summary Many important chemical engineering operations involve the suspension of solid particles in a liquid phase inside stirred tanks. Relevant examples include adsorption, crystallization, dissolution, leaching, precipitation, ion exchange and catalytic multiphase processes. This chapter describes a phenomenological model for the quantitative determination of the suspended solids mass fraction in stirred tanks operated at partial suspension conditions. Experimental data on fractional suspension, obtained by the “Pressure Gauge Technique” in vessels stirred by a downward-pumping pitched-blade-turbine, are presented. Furthermore, model predicted trends are compared with experimen…
Global simulation of semivolatile organic compounds – development and evaluation of the MESSy submodel SVOC (v1.0)
2019
Abstract. The new submodel SVOC for the Modular Earth Submodel System (MESSy) was developed and applied within the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model to simulate the atmospheric cycling and air–surface exchange processes of semivolatile organic pollutants. Our focus is on four polycyclic aromatic hydrocarbons (PAHs) of largely varying properties. Some new features in input and physics parameterizations of tracers were tested: emission seasonality, the size discretization of particulate-phase tracers, the application of poly-parameter linear free-energy relationships in gas–particle partitioning, and re-volatilization from land and sea surfaces. The results indicate that the pre…
Influence of muscle strength and total work on exercise-induced plasma growth hormone isoforms in women
2003
The purpose of this investigation was to determine the influence of physical strength and the ability to do more total work on human growth hormone (GH) variants to a heavy resistance exercise protocol in untrained women. From a distribution of 100 healthy, untrained women, the strongest 10 women (S) and the weakest 10 women (W) were compared for GH responses pre- and post an acute heavy resistance exercise test (AHRET, 6 sets of 10 RM squats, 2 minutes rest between sets). Blood samples were obtained pre-exercise and immediately post-exercise and subsequently analysed in total as well as fractionated by Sephacryl S-100R column chromatography into three molecular weight size classes: fractio…
Water structure in water/AOT/n-heptane microemulsions by FT-IR spectroscopy
1992
Abstract FT-IR spectra in the OH stretching region of water/sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/n-heptane microemulsions as a function of the water/AOT molar ratio (R) and of the weight fraction (φ) of the micellar phase have been recorded at 25°C. After elimination of the unwanted CH contribution and correction for the water concentration, the shape of the normalized OH bands has been found to be dependent on R and practically independent of φ. The analysis of these bands in terms of “bound” and “bulk” water (representing, as a first approximation, the two water domains within the water pool) allowed the evaluation of the fraction (α) of the “bound” water as a function of R. A…
Partitioning of Aerosol Particles in Mixed-phase Clouds at a High Alpine Site
2007
6 German Aerospace Centre, D-82234, Wessling, Germany * Now at Institute for Atmospheric and Climate Science, ETH Zurich, 8092 Zurich, Switzerland Abstract The partitioning of aerosol particles between the cloud and the interstitial phase (i.e., unactivated aerosol) has been investigated during several Cloud and Aerosol Characterization Experiments (CLACE) conducted in winter and summer 2004 and winter 2005 at the high alpine research station Jungfraujoch (3,580 m altitude, Switzerland). Ambient air was sampled using different inlets in order to determine the scavenged fraction of aerosol particles, F Scav , and of black carbon, F Scav,BC . They denote the fraction of the aerosol volume con…
A mathematical model for the prediction of the injected mass diagram of a S.I. engine gas injector
2013
A mathematical model of gaseous fuel solenoid injector for spark ignition engine has been realized and validated through experimental data. The gas injector was studied with particular reference to the complex needle motion during the opening and closing phases, which strongly affects the amount of fuel injected. As is known, in fact, when the injector nozzle is widely open, the mass flow depends only on the fluid pressure and temperature upstream the injector: this allows one to control the injected fuel mass acting on the “injection time” (the period during which the injector solenoid is energized). This makes the correlation between the injected fuel mass and the injection time linear, e…
Thermal Decomposition and Combustion of Microwave Pre-Treated Biomass Pellets
2021
The objective of the study was to investigate a more effective use of commercially available biomass pellets (wheat straw, wood, peat) using microwave pretreatment to improve heat production. Pellets were pretreated using the originally designed microwave torrefaction device. The effects of microwave (mw) pretreatment were quantified, providing measurements of the weight loss and elemental composition of pellets and estimating the effect of mw pretreatment on their porosity, surface area and calorific values at pretreatment temperatures of T = 448–553 K. Obtained results show that the highest structural variations and elemental composition during mw pretreatment were obtained for wheat stra…
Raman spectroscopic method for determining the crystallinity of polyethylene
1978
The Raman spectrum of partially crystalline polyethylene can be described as a superposition of three components, which originate from the orthorhombic crystalline phase, a meltlike amorphous phase, and a disordered phase of anisotropic nature, where chains are stretched but have lost their lateral order. The mass fractions involved in the three phases can be derived directly from the integral intensities of characteristic bands without an additional calibration procedure. A comparison of the results obtained for a variety of samples shows agreement with the crystallinities derived from the density, and the small-angle and wide-angle x-ray diagrams. Data indicate that the disordered anisotr…