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[en] Using a lab-constructed laser-excited filter fluorimeter deliberately designed to exhibit linearly heteroscedastic, additive Gaussian noise, it has been shown that accurate estimates may be made of the true theoretical Currie decision levels (YC and XC) and true Currie detection limits (YD and XD) for the detection of rhodamine 6 G tetrafluoroborate in ethanol. The obtained experimental values, for 5% probability of false positives and 5% probability of false negatives, were YC = 56.1 mV, YD = 125. mV, XC = 0.132 μg/mL and XD = 0.294 μg/mL. For 5% probability of false positives and 1% probability of false negatives, the obtained detection limits were YD = 158. mV and XD = 0.372 μg/mL. These decision levels and corresponding detection limits were shown to pass the ultimate test: they resulted in observed probabilities of false positives and false negatives that were statistically equivalent to the a priori specified values.
[en] Highlights: • Phase behavior of [BPy]BF4 + Salt + H2O systems at different temperature was studied. • LLE of ATPS composed with [4-MBP][BF4] and different salts have been experimentally determined. • Good agreement has been obtained with several empirical expressions. • Salting-out ability can be related to Gibbs free energy of hydration of the constituent ions and EEV. • The effects of temperature and alkyl chain length of the ionic liquids have been discussed. -- Abstract: The binodal curves of 1-butylpyridinium tetrafluoroborate + sodium tartrate at T = (298.15, 308.15 and 328.15) K and 1-butyl-4-methylpyridinium tetrafluoroborate + sodium tartrate/ammonium citrate/trisodium citrate at T = 298.15 K were experimentally determined. Three empirical equations were used to correlate the binodal data. The tie-line data were successfully correlated using the Othmer–Tobias and Bancroft and two-parameter equations. Factors affecting the binodal curves, such as temperature and the nature of the ionic liquids, were also studied. The two-phase area expanded with a decrease in temperature, whereas the absolute value of the slope of the ties slightly decreased with an increase in temperature. With an increase in the alkyl chain length of the ionic liquids (ILs) in the investigated systems, the binodal curves shifted closer to the origin. Finally, the effective excluded volume (EEV) values obtained from the binodal model were determined, and the salting-out ability decreased in the following order: Na3C6H5O7 > Na2C4H4O6 > (NH4)3C6H5O7
[en] As a promising chemiresistor for gas sensing, the single-walled carbon nanotube (SWCNT) network has not yet been fully utilized for humidity detection. In this work, it is found that as humidity increases from 10% to 85%, the resistance of as-grown SWCNT networks first decreases and then increases. This non-monotonic resistive response to humidity limits their sensing capabilities. The competition between SWCNT resistance and inter-tube junction resistance changes is then found to be responsible for the non-monotonic resistive humidity responses. Moreover, creating sp"3 scattering centers on the SWCNT sidewall by monovalent functionalization of four-bromobenzene diazonium tetrafluoroborate is shown to be capable of eliminating the influence from the inter-tube junctions, resulting in a continuous resistance drop as humidity increases from 10% to 85%. Our results revealed the competing resistive humidity sensing process in as-grown SWCNT networks, which could also be helpful in designing and optimizing as-grown SWCNT networks for humidity sensors and other gas sensors. (paper)
[en] Highlights: • The CPE and (CPE)ijk data have been measured over entire composition range at four temperatures. • The observed data have been fitted to Redlich–Kister equation. • The observed data have been analyzed in terms of Graph theory. • The values determined by Graph theory compare well with experimental values. - Abstract: The excess heat capacities, CPE and (CPE)ijk (calculated from the measured molar heat capacities, Cp data) of binary 1-ethyl-3-methylimidazolium tetrafluoroborate (i) + pyrrolidin-2-one or 1-methylpyrrolidin-2-one or pyridine (j); pyrrolidin-2-one (i) + pyridine (j) and ternary 1-ethyl-3-methylimidazolium tetrafluoroborate (i) + pyrrolidin-2-one or 1-methylpyrrolidin-2-one (j) + pyridine (k) mixtures have been measured as a function of composition at T = (293.15, 298.15, 303.15 and 308.15) K and 0.1 MPa using micro differential scanning calorimeter. The (CPE)ijk values for the present ternary mixtures are positive over entire range of composition. The CPE and (CPE)ijk data have been fitted to Redlich–Kister equation to compute binary and ternary adjustable parameters along with their standard deviations. The topology of the constituent molecules (Graph theory) has been utilized to obtain the expressions that describe well the CPE and (CPE)ijk data of the present mixtures. It has been observed that Graph theory describes well the CPE and (CPE)ijk data of the binary as well as ternary mixtures
[en] The luminescence properties of Ce3+ ions in magnesium fluoroborates, Mg3BO3F3 and Mg2BO3F, upon X-ray and synchrotron radiation excitation are reported and discussed. VUV excitation spectra of Mg3BO3F3 : Ce3+ can be reasonably explained by taking into account several factors, such as the electronic structure of Mg3BO3F3 and energy loss mechanisms. It is suggested that the luminescence behavior of Ce3+ is influenced by the presence of F- vacancies in the lattice
[en] Highlights: • Targets of this research are ILs mixtures. • Densities and viscosities were measured for three ILs mixtures. • Excess molar properties were deduced from the experiments. • Viscosities were discussed by the ideal Grunberg and Nissan mixing law. - Abstract: Densities and viscosities of binary ionic liquids mixtures, 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate ([eOHmim][BF4]) + 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate ([eOHmim][BF4]) + N-butylpyridinium tetrafluoroborate ([bpy][BF4]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) + N-butylpyridinium tetrafluoroborate ([bpy][BF4]) were measured over the entire mole fraction from T = (298.15 to 343.15) K. The excess molar volumes were calculated and correlated by Redlich–Kiser polynomial expansions. The viscosities for pure ionic liquids were analyzed by means of the Vogel–Tammann–Fulcher equation and ideal mixing rules were applied for the ILs mixtures
[en] This document outlines the program planned for the MSRE in fiscal years 1968 and 1969. It includes a bar diagram of the program, a critical-path type diagram of the operations, and a brief description of each task. In addition to the work at the reactor site, the outline also covers activities elsewhere at ORNL and by the AEC that directly affect the reactor schedule. The amount of detail and the accuracy with which we can estimate times varies considerably among the different items on the schedule. Some items, such as annual checkouts and core sample replacement, have been done before and our time estimates do not include any contingency, In the case of such tasks as planning, reviewing, and preparing for experiments or operations, we have set target dates that appear reasonable and we fully expect to meet these. Processing the salt is a different matter. If there are no unforeseen difficulties we should finish easily in the time shown, but the operation is in part a shakedown, so delays would not be too surprising, The time for modifying the system and adding fluoroborate is, of course, uncertain because the requirements are not yet known. As the requirements develop in more detail the estimate will be updated, but we do not foresee any major dislocation in the schedule, The scheduled time for preparation of enriching salt is becoming tight because of delays in facility construction. Should there be further delays in this key item, the entire schedule would have to be reconsidered.
[en] Structural and luminescence behaviour of the Sm3+ doped lead fluoroborate glasses with the composition (55-x)B2O3+20PbO+15PbF2+10Bi20+xSm2O3 (where x=0.05, 0.1, 0.5, 1.0 and 2.0 in wt%) have been studied using FTIR, Raman, optical absorption and luminescence spectroscopic techniques. The bonding parameter, oscillator strengths and J-O parameters have been calculated and reported. The various radiative properties of the prepared glasses have been calculated using JO theory. Intense reddish-orange luminescence was observed in the prepared glass at 604 nm. Lifetime of the 4G5/2 level is found to decrease with increasing concentration of Sm3+ ions and the results were discussed and presented. (author)
[en] Considering its ready availability and low cost, L-proline would be the first choice catalyst for preparing aldol adducts with high diastereo- and enantioselectivity. However, proline presents some major drawbacks, including poor performance in direct aldol reactions with aromatic aldehydes, limited solubility, and reactivity in nonpolar organic solvents, and side reactions that make using high catalyst loadings necessary to reach satisfactory conversions. Therefore, numerous proline-modified organo catalysts such as prolinamides, proline thioamides, sulfonamides, chiral amines, and organic salts have been designed for direct aldol reactions. An alternative is to add a readily available additive to the reactions containing proline. This last approach is clearly advantageous in avoiding tedious chemical syntheses of organo catalysts and would ultimately allow the construction of libraries of catalyst protocols by simply changing the additive. Acid additives can influence the outcome of enamine mediated reactions; however, only a few screening studies of acid additions to thiourea organo catalysts are available in the literature. The reaction between cyclohexanone and 4-nitrobenzaldehyde was selected as a standard model reaction for screening of more effective acid additives to thiourea
[en] This paper briefly reports the mechanism of non-radiative energy transfer process from Tb3+ → Eu3+ in sodium fluoroborate glass by measuring the emission intensity of Tb3+ with varying Eu3+ concentration at room temperature. From the fluorescence spectra, a decrease of terbium fluorescence intensity have been observed as a result of energy transfer from terbium ions to europium ions. Quantum efficiencies and energy transfer probabilities have been calculated. (author)