Accordion

Figures 15 and 16 provide a summary of the compression cycles for rotary and single-punch tablet presses. The formation of the tablet compact in these two types of presses mainly differs in the compaction mechanism itself, as well as the much greater speeds achieved with rotary type presses. The single punch basically uses a hammering type of motion (i.e., the upper punch moves down while the lower punch remains stationary), while rotary presses make use of an accordion-type compression (i.e., both punches move toward each other). The former find their primary use as an R D tool, whereas the latter, having higher outputs, are used in most production operations.

In practical applications, it can be a factor that the above approach by virtue of the cycle over A values has a higher minimum number of scans per ti value than the standard experiment and its various accordion versions. For dilute samples, this does not matter but for concentrated samples the instrument time can be longer than required considering the inherent sensitivity. 

In 2000, Krishnamurthy et al. have presented the 2/,3/-HMBC experiment (Figure 20), that affords for the first time the means of unequivocally differentiating between 2/ch from 3Jch correlations.59 Their approach is based on a further derivative of the constant-time variable delay introduced in the IMPEACH-MBC experiment. The user-definable /-scaling factor of the CIGAR-HMBC is used in the new experiment, the 2J,3J-HMBC experiment, to differentiate between 2/CH from 3Jch correlations. This new pulse sequence element has been given the acronym STAR (Selectively Tailored Accordion F1 Refocused) operator. 

The response is entirely consistent with the physics of an accordion bellows. 

Figure 8.34 Left Gold focal conics of MHOBOW coexisting with accordion domains in 4-p.m SSFLC cell. Cell has not seen electric field. Right Same area after brief application of field above threshold for causing textural change of focal conics from gold SmA-like to bistable blue SmC -like. Transition from gold to bistable blue is still incomplete in this photomicrograph clear domain walls between two textures are easily seen.

GAUZE PETROLATUM STEP BACK ACCORDION WHITE 16X3" 12S 6510002020800 PG 8.54 ... 

The solid state structures of these materials suggest that the 2D GS network is more accurately described as an assembly of ID GS ribbons connected to each other via lateral (G)N-H—O(S) H-bonds that serve as flexible hinges. These hinges allow the GS sheet to pucker, like an accordion, without an appreciable change in the near-linear geometries, which are considered to be optimal, of the (G)N-H—O(S) H-bonds. With respect to crystal metrics, the range of repeat distances within the GS... 

To provide the means of sampling a wider range of potential long-range heteronuclear coupling constants, an alternative version of this heteronuclear shift correlation experiment is called the accordion-optimized HMBC, or ACCORD-HMBC [50]. Additional modifications of this experiment are also available [51]. 

Varmuza, K. Chemometrics The computer as a partner in chemical data interpretation. Lecture at German-Austrian Chemist s Meeting, 14 May 1986, music played by J. Jaklin on a diatonic accordion, Innsbruck, Austria, 1986. 

Figure 5.9 Comparison plots of the downfield region of (a) an 8-Hz optimized HMBC and (b) a 2-10-Hz accordion-optimized IMPEACH-MBC experiment. Both spectra were acquired using a 1.7-mm SMIDG NMR probe for identical times at 600-MHz.

Hadden, C.E., Martin, G.E., and Krishnamurthy, V.V., Improved performance accordion heteronuclear multiple-bond correlation spectroscopy — IMPEACH-MBC, J. Magn. Reson., 140, 274, 1999. 

Fig. 4. Modified X/Y IMPEACH-MBC pulse sequence used for 19F/15N shift correlation according to Ref. 27. The notation of 90° and 180° pulses is as before. The (d/2 — 180°(Y) — d/2) element represents a variable delay that is incremented concurrently with the decrementation of the accordion delay vd. Pulse phases are x, unless specified x = — x 2 = x, — x 3 = x, x, — x, — x = , — x, — x, x. The bipolar gradients Gs flanking the 180°(Y) pulse can be set to arbitrary power levels, and the relative strengths of the coherence selection gradients G and G2 are determined by G2/G1 =2 Yy/Tx-...

Fig. 5. 19F/15N IMPEACH MBC spectrum of a mixture of 2- and 3-fluoropyridine. The accordion optimisation range was varied from 4 to 50 Hz the Fx frequency domain was digitised using 64 increments of the evolution time, ti. The Fi doublet splitting for the 2-fluoropyridine correlation of 70bs = 728 Hz (see text) is clearly visible while the smaller one for the 3-fluoropyridine correlation is no longer resolved. Reproduced from Ref. 27 by permission of J. Wiley Sons.

The spectra contain a series of lines below 600 cm-1 with a spacing between the lines related to the chain length. These lines are due to the longitudinal acoustic "accordion mode . 

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