Asynchronous

Modem board and interface SW a bidirectional modem is used to connect the host system, located in the plant, with a remote PC. It is asynchronous, with a throughput of 28000 b/s. The remote PC must match the characteristics of the in-plant PC of the AEBIL system. 

Modem a bidirectional modem connection (asynchronous, 28000 b/s) between the PC of the on-site AEBIL system and a laboratory PC has enabled transfer of data files and monitor presentations from the peripheral station to the central one, strongly enhancing initial assistance in data interpretation at drastically reduced costs. 

The second task is then analysing the results of the scan. The results can be displayed live on a display screen, or stored and presented all at once or after further scaling and analysis. This playback feature of sample data will be the subject of the remainder of the paper, for as we will see the playback need not be immediate nor on site, but could take place synchronously or asynchronously over the Internet. 

The instrument/display (client/server) paradigm allows for synchronous and asynchronous analysis, locally or remotely via the Internet or in-house Intranet network. 

Sakamoto A, Okamoto H and Tasumi M 1998 Observation of picosecond transient Raman spectra by asynchronous Fourier transform Raman spectroscopy 1998 Appl. Spectrosc. 52 76-81... 

If the masses are displaced in an arbiPary way or arbiPary initial velocities are given to them, the motion is asynchronous, a complex mixture of synchronous and antisynchronous motion. But the point here is that even this complex motion can be broken down into two normal modes. In this example, the synchronous mode of motion has a lower frequency than the antisynchronous mode. This is generally Pue in systems with many modes of motion, the mode of motion with the highest symmePy has the lowest frequency. 

The regioselectivity benefits from the increased polarisation of the alkene moiety, reflected in the increased difference in the orbital coefficients on carbon 1 and 2. The increase in endo-exo selectivity is a result of an increased secondary orbital interaction that can be attributed to the increased orbital coefficient on the carbonyl carbon ". Also increased dipolar interactions, as a result of an increased polarisation, will contribute. Interestingly, Yamamoto has demonstrated that by usirg a very bulky catalyst the endo-pathway can be blocked and an excess of exo product can be obtained The increased di as tereo facial selectivity has been attributed to a more compact transition state for the catalysed reaction as a result of more efficient primary and secondary orbital interactions as well as conformational changes in the complexed dienophile" . Calculations show that, with the polarisation of the dienophile, the extent of asynchronicity in the activated complex increases . Some authors even report a zwitteriorric character of the activated complex of the Lewis-acid catalysed reaction " . Currently, Lewis-acid catalysis of Diels-Alder reactions is everyday practice in synthetic organic chemistry. 

Using a Terminal. Dial-up terminals may also be used to access a vendor s databases however, the terminal, personal computer, word processor, or microcomputer must all be compatible with specific functionaHties. Eor example in order to access the DIALOG service these must all be TTY compatible have ASCII coding and be compatible for asynchronous transmission in full-duplex mode for communication through DIALNET,... 

The activation energies were computed to 3.0 (toward 183), 0.3 (toward 182), and 21.8 kcal/mol (toward 184) at the B3-LYP/6-31G level, and thus the mechanism leading to 182 is the preferred one. The transition states of all three reactions belong to concerted but asynchronous reaction paths. The transacetalization of 177 with acylium cations results in the formation of the thermodynamically stabilized 187 (Scheme 121) [97JCS(P2)2105]. 186 is less stable than 187, and 185 is destabilized by 32.5 kcal/mol. Moreover, transacetalization of 177 with sulfinyl cations is not a general reaction. Further computational studies on dioxanes cover electrophilic additions to methylenedioxanes [98JCS(P2)1129] and the influence... 

Nitrones are a rather polarized 1,3-dipoles so that the transition structure of their cydoaddition reactions to alkenes activated by an electron-withdrawing substituent would involve some asynchronous nature with respect to the newly forming bonds, especially so in the Lewis acid-catalyzed reactions. Therefore, the transition structures for the catalyzed nitrone cydoaddition reactions were estimated on the basis of ab-initio calculations using the 3-21G basis set. A model reaction indudes the interaction between CH2=NH(0) and acrolein in the presence or absence of BH3 as an acid catalyst (Scheme 7.30). Both the catalyzed and uncatalyzed reactions have only one transition state in each case, indicating that the reactions are both concerted. However, the synchronous nature between the newly forming 01-C5 and C3-C4 bonds in the transition structure TS-J of the catalyzed reaction is rather different from that in the uncatalyzed reaction TS-K. For example, the bond lengths and bond orders in the uncatalyzed reaction are 1.93 A and 0.37 for the 01-C5 bond and 2.47 A and 0.19 for the C3-C4 bond, while those in... 

Honk et al. concluded that this FMO model imply increased asynchronicity in the bond-making processes, and if first-order effects (electrostatic interactions) were also considered, a two-step mechanisms, with cationic intermediates become possible in some cases. It was stated that the model proposed here shows that the phenomena generally observed on catalysis can be explained by the concerted mechanism, and allows predictions of the effect of Lewis acid on the rates, regioselectivity, and stereoselectivity of all concerted cycloadditions, including those of ketenes, 1,3-dipoles, and Diels-Alder reactions with inverse electron-demand [2],... 

The mechanism of the carbo-Diels-Alder reaction has been a subject of controversy with respect to synchronicity or asynchronicity. With acrolein as the dieno-phile complexed to a Lewis acid, one would not expect a synchronous reaction. The C1-C6 and C4—C5 bond lengths in the NC-transition-state structure for the BF3-catalyzed reaction of acrolein with butadiene are calculated to be 2.96 A and 1.932 A, respectively [6]. The asynchronicity of the BF3-catalyzed carbo-Diels-Alder reaction is also apparent from the pyramidalization of the reacting centers C4 and C5 of NC (the short C-C bond) is pyramidalized by 11°, while Cl and C6 (the long C-C bond) are nearly planar. The lowest energy transition-state structure (NC) has the most pronounced asynchronicity, while the highest energy transition-state structure (XT) is more synchronous. 

In an investigation by Yamabe et al. [9] of the fine tuning of the [4-1-2] and [2-1-4] cycloaddition reaction of acrolein with butadiene catalyzed by BF3 and AICI3 using a larger basis set and more sophisticated calculations, the different reaction paths were also studied. The activation energy for the uncatalyzed reaction were calculated to be 17.52 and 16.80 kcal mol for the exo and endo transition states, respectively, and is close to the experimental values for s-trans-acrolein. For the BF3-catalyzed reaction the transition-state energies were calculated to be 10.87 and 6.09 kcal mol , for the exo- and endo-reaction paths, respectively [9]. The calculated transition-state structures for this reaction are very asynchronous and similar to those obtained by Houk et al. The endo-reaction path for the BF3-catalyzed reaction indicates that an inverse electron-demand C3-0 bond formation (2.635 A... 

The influence of alkyl substituents on the asynchronous transition-state structure of the BF3-catalyzed carbo-Diels-Alder reaction of a,/ -unsaturated aldehydes with 1,1-dimethyl-l,3-butadiene derivatives has been investigated by Dai et al. [13]. 

In a combined experimental and theoretical investigation it was found that the / -alkyl group in the dienophile gave a steric interaction in the transition-state structure which supported the asynchronous transition-state structure for the Lewis acid-catalyzed carbo- and hetero-Diels-Alder reactions. The calculated transition-state energies were of similar magnitude as obtained in other studies of these BF3-catalyzed carbo-Diels-Alder reactions. 

The reaction of methyl vinyl ketone with furan catalyzed by BF3 was studied by Babiano et al. [22]. The transition states predicted were also relatively concerted and highly asynchronous for all the reaction paths studied. 

The transition-state structures were also found to be more asynchronous in the presence of BF3 Lewis acid compared with the uncatalyzed reactions. 

The influence of the Lewis acid catalyst can be understood from the FMO diagram to the right in Fig. 8.17. The Lewis acid catalyst enhances significantly the asynchronicity of the bond-forming process for the more favorable ortho transition state as the 0-C distance in the BH3-catalyzed reaction is 2.478 A compared to 2.284 A in the uncatalyzed reaction. For the use of AlMe3 as the catalyst the 0-C distance is calculated to be 2.581 A in the transition state. 

The theoretical investigations of Lewis acid-catalyzed 1,3-dipolar cycloaddition reactions are also very limited and only papers dealing with cycloaddition reactions of nitrones with alkenes have been investigated. The Influence of the Lewis acid catalyst on these reactions are very similar to what has been calculated for the carbo- and hetero-Diels-Alder reactions. The FMOs are perturbed by the coordination of the substrate to the Lewis acid giving a more favorable reaction with a lower transition-state energy. Furthermore, a more asynchronous transition-structure for the cycloaddition step, compared to the uncatalyzed reaction, has also been found for this class of reactions. 

Sstig, a. branched, branchy knotted, gnarled. Astronom, m. astronomer. astroDomisch, a. astronomical, astrophysikalisch, a. astrophysical. asymmetrisch, a. asymmetric, asymmetrical, asymptotisch, a. asymptotic, asynchron, a. asynchronous, aszendent, a. (Mtn.) primary. 

A more serious limit to this implementation is due to the volume of the recycling pump and associated equipment such as flowmeters and pressure sensors. As the pump moves with respect to the zones, its volume leads to a dead volume dissymmetry, which can lead to a decrease extract and raffinate purities. This decrease can be significant for SMB with short columns and/or compounds with low retention. However, it can be easily overcome by using a shorter column or asynchronous shift of the inlets/outlets [54, 55]. This last solution is extremely efficient and does not induce extra costs because it is a purely software solution. 

Asynchronous CA. CA rules are typically defined so that all lattice sites update their values simultaneously throughout the lattice on each time step. A natural generalization is to lift this restriction by allowing asynchronous updates [inger84]. 

In equation 10.7, the neuronal site variables Si(t) can be updated either synchronously, where each neuron is simultaneously updated throughout the net, or asynchronously, where at each time step only one randomly chosen neuron is updated. While the first choice has the virtue of more closely resembling a conventional CA dynamical updating scheme, the second choice is more physically realistic insofar as the brain does not have an internal clock to synchronize the dynamics of its neurons. In practice, while the two updating schemes produce slightly different behavior, the general behavioral characteristics of the net are the same. 

To show that f is a Lyapunov function, we assume that the net evolves asynchronously and calculate the explicit change in that is induced by a change in the neuron ... 

The energies of several intermediates that could arise from the reaction of diazoazoles with alkenes have been estimated [90JCS(P2)1943] by means of the MNDO, AMI SCF-MO, and ab initio methods. The calculations suggest a 1,4-dipole behavior (also viewed as a 1,7-dipole) for most diazoazoles when reacting with electron-rich alkenes it is believed that the approach between 438 and alkenes is asynchronous. On the basis of that study, some errors have been corrected (Scheme 95). 

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