Polarity enhancement

IRRAS Infrared reflection- Grazing-incidence polarized Enhanced sensitivity... 

The transition states are composed of loose ion pairs in so far as they involve a charge-delocalized anion, thereby enhancing polarity compared with the ground states (in which the ion pairs are tighter), because of an increase in anionic dissociation as the more bulky product anion is formed. As a consequence, specific micro-wave effects, directly connected to polarity enhancement, should depend on the structure of reactive ion pairs in the GS ... 

From the mean crystalline diameter of ca 4 pm and the diameter of a C.00 molecule (ca 1 nm), one can estimate that only a fraction of ca 0.0015 of the (Y>o molecules is located at the surface of the particles. Assuming that effective polarization transfer only occurs for C60 molecules located at the surface, one concludes that the observed signal enhancement of 15 5% corresponds to a polarization enhancement factor of ca 100 30. However, it should be noted that this simple estimation neglects the influence of spin diffusion which can lead to a transport of spin polarization into the bulk, resulting in a lower surface enhancement factor. 

V.T. Mikhaltsevitch and A.V. Beliakov, Polarization enhancement of NQR signals for explosive detection , Sohd State Commun. 138 (2006) 409—411. 

Figure 4.11 Si SSNMR spectra (MAS+CPMAS) for two samples, showing selective cross polarization enhancement of the 2-connected SiMe2 groups in the embedded sample [spectra (a) and (b)] and 1-connected SIMe2 groups in the surface sample [(c) and (d)].

A permeation enhancer can be defined as a compound that alters the skin barrier function so that a desired drug can permeate at a faster rate. Dozens of enhancers are patented each year, and several books have been written summarizing the work and proposing mechanisms of enhancement.70-72 The permeation enhancers may be classified simply as polar and nonpolar ones. They can be used individually or in combination, such as binary mixtures. For several drugs, the flux across skin was observed to be linear with that of the most widely used enhancer, ethanol.73-75 Another polar enhancer, isopropanol, facilitated ion association of charged molecules and enhanced the transport of both neutral and ionic species across the stratum corneum.76 77 While polar enhancers traverse the skin, nonpolar enhancers are largely retained in the stratum corneum both aspects make the combination a superior enhancer to the individual enhancers.78... 

Mawell-Wagner polarization enhanced by fabric arrangement... 

Appropriate modifications of the ESR spectrometer and generation of free radicals by flash photolysis allow time-resolved (TR) ESR spectroscopy [71]. Spectra observed under these conditions are remarkable for their signal directions and intensities. They may be enhanced as much as one hundredfold and may appear in absorption, emission, or in a combination of both modes. These spectra indicate the intermediacy of radicals with substantial deviations from equilibrium populations. Significantly, the splitting pattern characteristic for the spin density distribution of the intermediate remains unaffected thus, the CIDEP (chemically induced dynamic electron polarization) enhancement facilitates the detection of short-lived radicals at low concentrations. 

The initial relaxation results on PP over a temperature range from 24°C to -195°C are summarized in Figure 13. The T3 data were collected using a pulse sequence developed by Torchia (44) which allows cross-polarization enhancement of the signals. The T] p data were determined at 58 kHz using Tj p methodology of Schaefer et al. (1). As indicated in the figure, each of the carbons display individual relaxation rates in both types of experiments. The CH and CH2 carbons have a T minimum at ca. -110°C, nearly the same temperature as that reported by McBrierty et al.(45) for the proton Ti minimum in isotactic PP. 

S. Han, E. R. McCarney, B. D. Armstrong and M. D. Lingwood, Dynamic nuclear polarization-enhanced magnetic resonance analysis at X-band using amplified 1H water signal, in Magnetic Resonance Microscopy, S. L. Codd and J. D. Seymour (eds.),. Wiley-VCH, Weinheim, 2009. 

Recently a new pulse sequence PENDANT (Polarization Enhancement Nurtured During Attached Nucleus resting) was suggested126-128 ... 

Lee HN, Christen HM, Chisholm ME, Rouleau CM, Lowndes DH (2005) Strong polarization enhancement in asymmetric three-component ferroelectric superlattices. Nature 433 395... 

Neaton JB, Rabe KM (2003) Theory of polarization enhancement in epitaxial BaTiOa/ SrTiOs superlattices. Appl Phys Lett 82 1586... 

Nakhmanson SM, Rabe KM, Vanderbilt D (2006) Predicting polarization enhancement in multicomponent ferroelectric superlattices. Phys Rev B 73 060101(R)... 

Carbamates Methyl carbamates Thiocarbamates 5xl02- 2 5x10-50 Highly polar enhanced solubility reduced adsorption compared with organochlorines... 

The temperature dependence of the dynamic nuclear polarization enhancement (A ) of the protons in tetrathiafulvalinium tetracyanoquinodi-methane (TTF-TCNQ) and potassium TCNQ (K.TCNQ) is reported. Theoretical expression of A is given experimental results are discussed and allow us to... 

Polarization Enhancement of NQR Signals 4. Multi-pulse Sequences Under Conditions of Magneto-acoustic 168... 

Key Words NQR, Nitrogen, Multi-pulse sequence. Explosive detection. Magneto-acoustic ringing. Polarization enhancement. 

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