Poly resonance frequency

In our tip-enhanced near-field CARS microscopy, two mode-locked pulsed lasers (pulse duration 5ps, spectral width 4cm ) were used for excitation of CARS polarization [21]. The sample was a DNA network nanostructure of poly(dA-dT)-poly(dA-dT) [24]. The frequency difference of the two excitation lasers (cOi — CO2) was set at 1337 cm, corresponding to the ring stretching mode of diazole. After the on-resonant imaging, CO2 was changed such that the frequency difference corresponded to none of the Raman-active vibration of the sample ( off-resonant ). The CARS images at the on- and off- resonant frequencies are illustrated in Figure 2.8a and b, respectively. 

The polymer is a commercial sample of poly-methylmethacrylate, PMMA. The Rheovibron data from 3.5, 11, 35, and 110 Hz are superposed on the nomograph along with the resonant frequency DMA data using a To value of 175°C for this sample of PMMA. 

The nucleic acid sensor was prepared by first derivatizing the quartz surface with a 3 1 styrene-acrylic acid copolymer. Poly (A) was then covalently immobilized onto pendant carboxylic acid groups by amide bond formation with the amino groups on the adenine base. Hybridization occurred during incubation with poly(U). Following each of the three steps, the sensor was rinsed and dried and the resonant frequency of oscillation was measured. Prior to any treatment, the quartz crystals exhibited a resonant frequency of 9 MHz. Because each step in the surface treatment involved the addition of mass to the crystal surface, a frequency decrease was expected after each step. Figure 7.9 shows the actual frequency changes measured for a sensor prepared as described above, as well as for a sensor prepared with no poly(A) included in the second step (i.e., a control sensor). 

While this sensor employed only a model nucleic acid probe (poly(A)), it demonstrates the principle of detection of the complementary sequence, the analyte poly(U). Figure 7.9(a) shows that a frequency decrease of 600 Hz was observed following the hybridization step, Step 3, and that this decrease was not observed with a control sensor that did not possess surface-bound poly(A). The sensor exhibits a relatively small frequency change that is superimposed on a large initial resonance frequency (9 MHz), and so S/N is low in addition, difficulties associated with ex situ measurements at constant humidity preclude the use of this device for practical DNA or RNA detection. 

Fig. 16. Experimental C direct excitation spectra of an aqueous dispersion of poly-u-butylcyanoacrylate nanocapsules (top) and of reference samples of liquid and dissolved constituents (a aqueous solution of the block-copolymer surfactant Pluronic F68 b the liquid oil component Miglyol 812 used as capsule content c the liquid monomer u-butylcyanoacry-late). " All spectra are measured at a resonance frequency of wc 100MHz under full proton decoupling. In the spectrum of the dispersion, no narrow signals occur at the positions of the n-butylcyanoacrylate resonances (vertical arrows), indicating the complete absence of the monomer after the formation of the capsules. For the capsule dispersion, a slight increase in line width is observed for the characteristic resonances of the liquid components.

Fig. 26. Experimental ( H)- C cross-polarization spectra of an aqueous dispersion of poly-n-butylcyanoacrylate nanocapsules at different mixing periods tc. The spectra are measured at a resonance frequency of Wc 100 MHz after contact times of cp O.l, 0.25 and 0.5 ms under full proton decoupling. The wide lines derive from the polymer forming the capsule membrane while the narrow lines are assigned to the triglyceride oil. At cp = 0.25 ms, the broad signals of the polymer have almost developed to their full intensity, whereas the signals of the oil still gain amplitude. ...

Figure 7.23 shows the dependence of nTi on the reciprocal of temperature for CH and CH2 of bulk poly(vinyl methyl ether) [31]. (Data are collected by the inversion recovery method under proton noise decoupling, not by CPMAS.) Measurements are carried out at two resonance frequencies, 25.15 and 62.5 MHz for nuclei. As seen from the figure, the nTi minimum is... 

Although the QCM has been used to quantitate the mechanisms of enzymatic reactions in some instances, more often it has been used to determine the overall rates and characteristics of products formed in these reactions. For example, multistep processes have been studied that are involved in the enzymatic degradation of polymeric films formed from poly(L-lactide) [61] and poly(3-hydroxybutyrate) [60]. In QCM studies at a high resonance frequency, 27 MHz, DNA polymerase was studied using immobilized DNA to obtain rate constants for three individual steps in the mechanism of this enzymatic reaction ( [65] Chap. 10 in this volume). 

As pointed out above, the most accurate and reliable information obtained by ENDOR is the resonance frequency that directly gives the hyperfine coupling con.stant. In this respect, the firequency-derivative ENDOR spectra obtained by cw-ENDOR detection by employing the frequency modulation scheme, are particularly important because of high-frequency resolution. Combined with ENDOR-induced ESR, the maximum ENDOR frequency, important in identifying the peak value of the spin density distribution, can be determined very accurately [7]. Specific examples are discussed in the cases of solitons in polyacetylene and polarons in poly(paraphenylene vinylene) in Sections 3.2 and 3.3. 

An example of an ICP is poly(-3,4-ethylenedioxythiophene) with the short name PEDOT. The polymer can be prepared in acetonitrile or in aqueous electrolytes. The polymer films formed have quite different oxidation-reduction properties. For the film prepared in dry acetonitrile, the change of the half width of the quartz resonance frequency in the oxidation-reduction cycle is negligible (Figure 11.12). ... 

Figure 11.12 Half width of the resonance frequency Aw as function of the potential of a poly (-3,4-ethylenedioxythiophene) film grown in dry acetonitrile or water, respectively containing 0.1 mol-dm 3,4-ethylenedioxythiophene and 0.1 mol dm" LiC104.

Fig. 21 Changes in resonant frequency (panel A) and resonant resistance (panel B) for a poly(vinylferrocene-co-/ /-isopropylacrylamide) film (VF NIPAA = 1 13 dry film thickness ca. 5 pm) as a function of temperature, with the film maintained in the reduced state ( = 0.0 V dashed line) and in the oxidized state (E = 0.5 V full line). Electrode Pt (area = 0.2 cm ) on 9-MHz AT-cut quartz crystal. Solution 0.1 moldm NaCl04. Temperature scanned from 35 to 10 °C over the course of ca. 1 h. (Reproduced from Ref [137] with permission from the American Chemical Society.)...

In Sect. 2.7.2.1.2, the phenomenon of film resonance was discussed. In this special situation, the film thickness corresponds to one quarter of the acoustic wavelength, that is, the acoustic phase shift defined by Eq. (11) has the numerical value = 7t/2. For a film of given shear modulus, progressive increase in thickness will eventually result in this condition being satisfied. This phenomenon is illustrated in Fig. 27 [41] for a poly(3-hexylthiophene) film as a function of the polymerization charge during deposition. As can be seen, the resonant frequency transiently moves sharply upwards and the peak amplitude... 

Homopolymers.—Vinyl Monomers and Derivatives. Robinson et al. have described an exhaustive study of the measurement of poly(vinyl chloride) tacticity by H n.m.r. It was found that different solutions of the same polymer were less reproducible than repeat runs on the same solution i.e. sampling errors were greater than instrumental factors. Overall, one must use several samples for maximum precision, and combine results from both CH and CHj signals. The sensitivity of C resonance frequencies to small structural changes is illustrated by reports of the resolution of configurational pentads in polymers of... 

Polyamide is a hydrophilic polymer and has three relaxations between 1(X)°C and — 180°C that are strongly affected by sorbed water. Figure 23 represents the damping and resonant frequency for four poly(hexamethylene adipamide) measured by Woodward et al. using a transverse beam apparatus [21], showing that the resonant frequency is related to the dynamic modulus. The dry sample (0% H2O) has an a-relaxation at 370°K, and the damping peak shifted to lower temperatures as the water content in the polymer was increased. When the polymer absorbs water, the / -relaxation appears at... 

Fig. 23 Effect of water on the damping and resonant frequency as a function of temperature for poly(hexamethylene adipamide). (From Ref. 21.)...

Fig. 3. The variation of rate of change of resonant frequency with time at reed position 1 (699 mm fiem top of settling zone) for poly-disperse 55-100 pm glass ballotini spheres settling in water 17 C at various initial suspended solids volume concentrations, < .

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