Contribution a l'etude des groupements superficiels des noirs de carbone a l'aide de reactifs gazeux: Evolution de l'acidité superficielle du sphéron 6 au cours de traitements thermiques

The Spheron 6 surface acidity has been investigated by adsorption of ammonia at 70°C and microcalorimetry. The carbon samples are degassed at temperatures up to 950°C. The effects of degassing temperature on the adsorption isotherms of ammonia are shown in Fig. 2. Up to 350°C, the isotherms are characterized by a very slight decrease in the total amount adsorbed. On the contrary, these amounts considerably decrease for higher degassing temperatures. The differential heats of adsorption (Fig. 3), which are initially close to 100 kJ/mole, are shown to decrease with the amount of adsorbed ammonia: the higher the degassing temperature, the greater the decrease. By desorption, the adsorption of ammonia is found partly irreversible. By readsorption it is possible to measure the differential heat of the reversible adsorption and to deduce from it the differential heat of the irreversible adsorption (Fig. 4) as well as the amount irreversibly adsorbed, i.e. chemisorbed.The amounts of chemisorbed ammonia are found to be respectively 0.36 ± 0.01 × 10^?6 mole m² at 150°C and 0.29 ± 0.01 × 10^?6 mole m^?2 at 350°C. With the surface covering the differential heat of chemisorption of ammonia slightly decreases from 105 to 88 kJ. mole^?1.These values suggest that carboxyl groups are responsible for irreversible adsorption of ammonia. This assumption has been checked by various experiments: the irreversible uptake of ammonia lies in the same range as the number of carboxyl surface groups determined by chemical analysis of functional groups (Table 1); the evolving of H₂O during the decomposition of the ammonium salt formed by reacting with ammonia has been observed and is probably correlated with the irreversible uptake of ammonia (Fig. 8); moreover it must be pointed out that irreversible adsorption of ammonia disappears after methylation of sample by diazomethane (Figs. 5 and 6). Then, the amounts of carboxyl groups can be determined by measuring the irreversibly adsorbed ammonia.This method has been applied to the study of the thermal stability of functional groups. Carboxyl groups are shown to be quickly decomposed by heat treatment above 500–600°C (Fig. 8).It appears from our experiments that the oxidation at constant temperature followed by a cooling under nitrogen is unable to regenerate functional groups on the surface of carbon after their removal at 950°C. On the contrary, by an oxidation at decreasing temperature it is possible to regenerate functional groups because they are stabilized by the oxidising atmosphere.The groups thus created behave like those initially present on Spheron 6: particularly the graph of the thermal elimination of carbon dioxide presents two peaks (Table 2, Fig. 12). The amount of regenerated carboxyl groups is found to be 0.25 × 10^?6 instead of 0.36 × 10^?6mole m^?2 on untreated Spheron 6.     

Permuteins of interleukin 1{beta}--a simplified approach for the construction of permutated proteins having new termini

A technique for the rapid and simple generation of permutatedversions of the interleukin-1ß (IL-1ß) geneis described. In this method, the human IL-1ß cDNAis twice amplified by the polymerase chain reaction (PCR) andthe resulting DNA fragments are ligated in tandem. Between thetwo genes, the DNA sequence encodes a short four amino acidloop to link the native N- and C-terminal ends of the IL-1ßprotein. By using PCR amplification from this starting template,a new version of the IL-1ß cDNA was obtained thatencodes a permutated form of the IL-1ß protein wherethe new N- and C-terminal amino acids correspond to residues65 and 64 of the native IL-1ß sequence, respectively.The name ‘permutein’ is proposed to describe proteinsgenerated by this technology. The molecular profile (IL-1 receptorbinding, biologic activity and solution properties) of the IL-1permutein produced by this technology, permutein 65/64, is shownto be identical to that of native IL-1ß The approachshould be useful to define further the structural features ofthis protein that are important for its function.     

Holistic Analysis of the Tribological Interfaces of an Axial Piston Pump – Focusing on the Pump Efficiency

Research work performed on an axial piston pump is shown in a holistic manner, analyzing each lubricating interface by linking their gap height and temperature behavior to the overall pump efficiency. The temperature field and dynamic fluid film height were measured in two of the three lubricating interfaces. This is the first time that the temperature fields and gap heights were simultaneously measured in two of the main three interfaces of an axial piston machine. For a deeper analysis of the measurement data, all gaps were simulated with a numerical tool which takes solid body deformation due to temperature and pressure loads into account. This unique combination of both extensive measurement data and sophisticated simulation resulted in novel trends that clarify the complex phenomena occurring in these hydrostatic fluid films.     

Effect of formulation and processing conditions on light shielding efficiency of thermotropic systems with fixed domains based on UV curing acrylate resins

Within this study relationships between material formulation and processing parameters and the morphology (vacuole formation) of thermotropic systems with fixed domains (TSFD) for overheating protection purposes were investigated. Main aim was on improving light shielding efficiency of TSFD based on UV curable acrylate resins by optimization of selected key parameters including photo‐initiator type and content, type of reactive diluent, radiation intensity/dose, and thermal treatment of layers during manufacturing. Variations of type of reactive diluent and thermal treatment had a minor effect on overheating protection performance. Utilization of photo‐bleaching photo‐initiator of acylphospine oxide type instead of a blend of conventional Type I (α‐hydroxy ketone type) and Type II (benzophenone) photo‐initiators enabled reduction of radiation dose to achieve properly cured layers. The results revealed that a significant reduction of radiation intensity/dose prevented formation of vacuoles. Consequently, light shielding efficiency of TSFD was enhanced significantly. Nevertheless, obtained scattering domain size was inappropriate for optimum light shielding efficiency and requires further optimization strategies. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3299–3310, 2013     

A Particle-into-Liquid Collector for Rapid Measurement of Aerosol Bulk Chemical Composition

We report on a new instrument developed for rapid automated on-line and continuous measurement of ambient aerosol bulk com- position.The general approach is based on earlier devices (Khlystov et al. 1995; Simon and Dasgupta 1995) in which ambient particles are mixed with saturated water vapor to produce droplets easily collected by inertial techniques. The resulting liquid stream is analyzed with an ion chromatograph to quantitatively measure the bulk aerosol ionic components. In this instrument, a modified ver- sion of a particle size magnifier (Okuyama et al. 1984) is employed to activate and grow particles comprising the fine aerosol mass. A single jet inertial impactor is used to collect the droplets onto a vertical glass plate that is continually washed with a constant water diluent flow of nominally 0.10 ml min^-1     

Field evaluation of a Portable Fine Particle Concentrator (PFPC) for ice nucleating particle measurements

The custom-built Portable Fine Particle Concentrator (PFPC) is evaluated for the measurement of ice nucleating particles (INPs) in the atmosphere. The concentrations of INPs in remote regions of the atmosphere are very low, often close to instrumental detection limits. The PFPC is a dual slit-nozzle virtual impactor where particles are concentrated from an input flow of 250 LPM (litres per minute) into an output flow of 10 LPM. The enrichment factors (EFs) for ambient particles with diameters between 0.4 and 2.5?µm were found to be 21?±?5 at sea level and 18?±?2 at a field station 3580 meters above sea level for the PFPC operated in horizontal configuration. Similar enhancement factors (16?±?5) in the concentrations of INPs measured by the Horizontal Ice Nucleation Chamber at the high-altitude station were observed when the air mass was characterized by high numbers of particles larger than 0.5?µm. When the number size distribution was dominated by particles smaller than 0.5?µm, the INP EF was considerably lower. Corroborating short-term measurements were provided by additional INP-measuring instruments, the Fast Ice Nucleus CHamber and the Frankfurt Ice Deposition Freezing Experiment. Results from two aerosol mass spectrometers also indicate significant particle enhancement using the PFPC. These results indicate that the PFPC can be usefully deployed to improve the detection efficiency of ambient INP measurements.

Copyright © 2019 American Association for Aerosol Research     

Polyamide solid state polymerization: Evaluation of pertinent kinetic models

Nylon 6,6 resins, in the form of pellets, were solid state polymerized in the temperature range of 160–200°C in a fixed‐bed reactor under flowing nitrogen for times of 0–4 h. The kinetics of the solid state polymerization (SSP) of nylon 6,6 were examined by the evaluation of pertinent rate expressions and the selection of the most suitable one for describing the apparent overall process. The Flory‐theory‐based kinetic models were the most effective both for this study's data and for data previously published on SSP of different polyamides. Accordingly, SSP rate constants and activation energies were derived, and process parameters, such as the temperature and time, were investigated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 671–681, 2005     

Role of water states on water uptake and proton transport in Nafion using molecular simulations and bimodal network

Using molecular simulations and a bimodal-domain network, the role of water state on Nafion water uptake and water and proton transport is investigated. Although the smaller domains provide moderate transport pathways, their effectiveness remains low due to strong, resistive water molecules/domain surface interactions. The water occupancy of the larger domains yields bulk-like water, and causes the observed transition in the water uptake and significant increases in transport properties.     

Viscosity‐molecular weight relationship for cellulose solutions in either NMMO monohydrate or cuen

The intrinsic viscosities, [η], of nine cellulose samples, with molar masses from 50 × 10³ to 1 390 × 10³ were determined in the solvents NMMO*H₂O (N‐methyl morpholin N‐oxide hydrate) at 80°C and in cuen (copper II‐ethlenediamine) at 25°C. The evaluation of these results with respect to the Kuhn–Mark–Houwink relations shows that the data for NMMO*H₂O fall on the usual straight line in the double logarithmic plots only for M ≤ 158 10³; the corresponding [η]/M relation reads log ([η]/mL g⁻¹) = –1.465 + 0.735 log M. Beyond that molar mass [η] remains almost constant up to M ≈ 10⁶ and increases again thereafter. In contrast to NMMO*H₂O the cellulose solutions in cuen behave normal and the Kuhn–Mark–Houwink relation reads log ([η]/mL g⁻¹) = −1.185 + 0.735 log M. Possible reasons for the dissimilarities of the behavior of cellulose in these two solvents are being discussed. The comparison of three different methods for the determination of [η] from viscosity measurements at different polymer concentrations, c, demonstrates the advantages of plotting the natural logarithm of the relative viscosities as a function of c. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011