Selective flotation of fossil resin from Wasatch Plateau high-volatile bituminous coal

Journal ArticleCertain bituminous coals are known to contain appreciable quantities of natural fossil or subfossil resin. Such resinous coals are found in the western US, particularly the Wasatch Plateau coalfield of UT. Some of the seams in this field contain an average of 5% resin. This fossil resin has been recovered by gravity and/or flotation processes since 1929. Resin concentrates thus produced are of low quality and are usually refined by solvent extraction. The purified resins are of commercial importance in the adhesive, coating, rubber, and ink industries, etc. An improved flotation technique has been developed which involves ozone conditioning to selectively float resin from high-volatile bituminous coal. With this flotation process, a concentrate product which contains 95% resin at a recovery of 80% can be obtained in single-stage flotation. By comparison, conventional flotation at 80% recovery produces a concentrate having a resin content of 30 to 40%

Molybdenite flotation from copper/molybdenum concentrates by ozone conditioning

Journal ArticleTypically, rougher molybdenite flotation and recovery from bulk copper/molybdenum concentrates involves the use of alkalisulfides, Nokes reagents, cyanides, oxidants, and/or thermal treatment to depress copper sulfide minerals. The bulk copper/molybdenum feed generally varies from 0.2% Mo to 1.0% Mo, and with traditional reagents the single-stage rougher flotation recovery of molybdenite varies between 40% and 90% at a concentrate grade of 5% to 10% Mo. With ozone conditioning for copper depression, however, improved separations appear to be possible, as demonstrated by tests with Cu/Mo concentrates from both the Phelps Dodge Morenci Operations and the Kennecott Copperton Operations. Single-stage rougher flotation after ozone conditioning can provide a molybdenum concentrate at a recovery of more than 90% and a rougher concentrate grade higher than 20% Mo in some cases. Subsequent cleaner flotation with additional ozone conditioning results in relatively copper-free molybdenum concentrates containing as much as 52% Mo. Preliminary analysis indicates that, with a multistage ozone conditioning/flotation strategy, the process is technically and economically viable and should be suitable for industrial application

Fossil resin, a value-added product from western coal

Journal ArticleCertain bituminous coals of the western United States are known to contain appreciable quantities of macroscopic fossil resin (resinite). Such resinous coals are found in the states of Arizona, Colorado, New Mexico, Utah, Washington, Wyoming, etc. The Wasatch Plateau coal field in Utah (Figure 1) has a particularly high content of fossil resin. It has been reported that many seams in this field average as much as 5% resin

An examination of acute cross-over effects following unilateral low intensity concentric and eccentric exercise

We compared the effects of low intensity concentric (CON) and eccentric (ECC) exercise on the force and neural responses of the dominant (exercised) elbow flexors (EFs), and studied if these conditions could induce cross-over effects to the contralateral (non-exercised) EFs. Fifteen subjects (8 males) completed all conditions (CON and ECC: 6 sets of low intensity exercise to failure; control: rest) in separate visits with a randomized order. Maximal isometric force and electromyography (EMG) of the dominant and contralateral EFs were assessed at pre, immediate-, 24-, and 48-h-post. Two-factor (condition and time) linear mixed-model analyses were performed to examine the force and EMG responses. Immediately post CON, contralateral EFs force was significantly (p = 0.026) higher (12.41%) than control, but no cross-over effects regarding the neural responses were observed. Immediately post ECC, dominant EFs force was significantly lower in ECC, compared to CON (p = 0.003) and control (p \u3c 0.001). This force remained depressed at 24- and 48-h post ECC, when compared to CON (p \u3c 0.001) and control (p \u3c 0.001). Our data suggests that submaximal unilateral exercises are not likely to impair contralateral muscle strength performance. Instead, concentric exercises may acutely improve muscle strength for the contralateral limb. However, this effect is not explained by changes in muscle excitation

Sex comparisons of agonist and antagonist muscle electromyographic parameters during two different submaximal isometric fatiguing tasks

© 2019 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society. To examine the task failure time of the force- and position-based submaximal elbow flexion fatiguing tasks for both sexes, twelve men and eight women visited the laboratory for two separate experimental occasions. During the experiment, they pulled against a rigid restraint for the force task and maintained a constant elbow joint angle to support an equivalent inertial load for the position task. For both fatiguing tasks (50% of the isometric strength at the elbow joint angle of 135 degree), the task failure time, along with the surface electromyographic (EMG) amplitude and mean frequency (MNF) were measured. The average failure time was longer for the force task than that for the position task (sexes combined: 39.6 ± 16.6 sec vs. 33.9 ± 14.9 sec, P = 0.033). In addition, men were overall less fatigable than women (tasks combined: 42.0 ± 14.7 sec vs. 28.7 ± 10.3 sec, P = 0.020). The multiple regression analyses showed that the task failure time in women was solely predicted by the rate of change of the triceps EMG MNF. Thus, more fatigability of women in this study was likely due to the quicker fatiguing rate of the antagonist triceps brachii muscle. Different from most previous studies that have used 90-degree elbow joint angle, the current 135-degree joint angle setup might have created a situation where greater muscle activity from the related muscles (e.g., the antagonist) were required for women than for men to stabilize the joint, thereby resulting in a shorter task failure time

Superintegrability on the two dimensional hyperboloid II

This work is devoted to the investigation of the quantum mechanical systems on the two dimensional hyperboloid which admit separation of variables in at least two coordinate systems. Here we consider two potentials introduced in a paper of C.P.Boyer, E.G.Kalnins and P.Winternitz, which haven't yet been studied. We give an example of an interbasis expansion and work out the structure of the quadratic algebra generated by the integrals of motion.Comment: 18 pages, LaTex; 1 figure (eps

Winning Strategies for Generalized Zeckendorf Game

Zeckendorf proved that every positive integer $n$ can be written uniquely as the sum of non-adjacent Fibonacci numbers; a similar result holds for other positive linear recurrence sequences. These legal decompositions can be used to construct a game that starts with a fixed integer $n$, and players take turns using moves relating to a given recurrence relation. The game eventually terminates in a unique legal decomposition, and the player who makes the final move wins. For the Fibonacci game, Player $2$ has the winning strategy for all $n>2$. We give a non-constructive proof that for the two-player $(c, k)$-nacci game, for all $k$ and sufficiently large $n$, Player $1$ has a winning strategy when $c$ is even and Player $2$ has a winning strategy when $c$ is odd. Interestingly, the player with the winning strategy can make a mistake as early as the $c + 1$ turn, in which case the other player gains the winning strategy. Furthermore, we proved that for the $(c, k)$-nacci game with players $p \ge c + 2$, no player has a winning strategy for any $n \ge 3c^2 + 6c + 3$. We find a stricter lower boundary, $n \ge 7$, in the case of the three-player $(1, 2)$-nacci game. Then we extend the result from the multiplayer game to multialliance games, showing which alliance has a winning strategy or when no winning strategy exists for some special cases of multialliance games.Comment: 24 pages, 8 figure

A comparison of motor unit control strategies between two different isometric tasks

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. Background: This study examined the motor unit (MU) control strategies for non-fatiguing isometric elbow flexion tasks at 40% and 70% maximal voluntary isometric contraction. Methods: Nineteen healthy individuals performed two submaximal tasks with similar torque levels: contracting against an immovable object (force task), and maintaining the elbow joint angle against an external load (position task). Surface electromyographic (EMG) signals were collected from the agonist and antagonist muscles. The signals from the agonist were decomposed into individual action potential trains. The linear regression analysis was used to examine the MU recruitment threshold (RT) versus mean firing rates (MFR), and RT versus derecruitment threshold (DT) relationships. Results: Both agonist and antagonist muscles’ EMG amplitudes did not differ between two tasks. The linear slopes of the MU RT versus MFR and RT versus DT relationships during the position task were more negative (p = 0.010) and more positive (p = 0.023), respectively, when compared to the force task. Conclusions: To produce a similar force output, the position task may rely less on the recruitment of relatively high-threshold MUs. Additionally, as the force output decreases, MUs tend to derecruit at a higher force level during the position task