Amines, C=n, and N=o Compounds

Colthup, Norman B.; Daly, Lawrence H.; Wiberley, Stephen E.

doi:10.1016/b978-0-12-182552-2.50014-0

Cited by 222 publications

(162 citation statements)

References 45 publications

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“…Such enhancements could be useful for various applications, including fluorescent and Raman sensing [77], high-power low-coherence light sources [78], and sources with tunable coherence [79]. Moreover, by extending the current linear theory to account for EPs in nonlinear systems, our approach could be applied to study the properties of lasers at EPs-a topic that has recently drawn great attention in the optics community [20][21][22]80].…”

Section: Discussionmentioning

confidence: 99%

General theory of spontaneous emission near exceptional points

Pick¹,

Zhen²,

et al. 2017

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Abstract:We present a general theory of spontaneous emission at exceptional points (EPs)-exotic degeneracies in non-Hermitian systems. Our theory extends beyond spontaneous emission to any light-matter interaction described by the local density of states (e.g., absorption, thermal emission, and nonlinear frequency conversion). Whereas traditional spontaneous-emission theories imply infinite enhancement factors at EPs, we derive finite bounds on the enhancement, proving maximum enhancement of 4 in passive systems with second-order EPs and significantly larger enhancements (exceeding 400×) in gain-aided and higher-order EP systems. In contrast to non-degenerate resonances, which are typically associated with Lorentzian emission curves in systems with low losses, EPs are associated with non-Lorentzian lineshapes, leading to enhancements that scale nonlinearly with the resonance quality factor. Our theory can be applied to dispersive media, with proper normalization of the resonant modes. References and links1. E. M. Purcell, "Spontaneous emission probabilities at radio frequencies," Phys. Rev. 69, 681--681 (1946). (CRC Press, 1995, vol. X). 3. S. V. Gaponenko, Introduction to Nanophotonics (Cambridge University, 2010 H. Yokoyama and K. Ujihara, Spontaneous Emission and Laser Oscillation in Microcavities

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Section: Discussionmentioning

confidence: 99%

General theory of spontaneous emission near exceptional points

Pick¹,

Zhen²,

et al. 2017

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“…Bands at 990 and 909 cm-' are observed in the unbrominated single crystal and arise from C-H wagging vibrations of terminal vinyl groups. 6 The vinyl unsaturation disappears early in the reaction since the bands a t 990 and 909 cm-' are essentially absent in the spectra of the brominated single crystals. From the intensity of the 909 cm-' band it has been estimated that a t least 98?6 of the vinyl end groups react with bromine and therefore are thought to be external to the crystal l a t t i~e .~ This is compared to spherulitic polyethylene where about 10% of the vinyl end groups do not react with bromine and are assumed to be present within the lattice as defect^.^…”

Section: Resultsmentioning

confidence: 99%

Infrared analysis of brominated polyethylene single crystals

Eguiluz

Ishida

Hiltner

1979

J. Polym. Sci. Polym. Phys. Ed.

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. Studies of polyethylene single crystals have yielded considerable information on the nature of the fold surface; however, interpretation of the results for this deceptively simple polymer is still a matter of debate. Selective chemical modification of the surface represents a powerful structural probe which has received little practical attention. The ability to selectively degrade the surface while leaving the crystalline core intact has been used to estimate the length and uniformity of chain segments traversing the Nondestructive halogenation reactions have also been shown to selectively modify the surface," but have not been exploited for surface characterization. In a previous paper, conditions for the suspension bromination of polyethylene were identified and the selectivity of the attack for noncrystalline regions of the polymer was ~o n f i r m e d .~The present investigation concerns the infrared analysis of polyethylene single crystals selectively modified by the nondestructive bromination reaction. Extensive infrared analysis of polyethylene crystals has shown the spectrum to be sensitive to morphological features of the crystalline structure, and the recent advent of Fourier transform infrared instruments wit,h a dedicated minicomputer provides a previously unavailable degree of resolution and capability to digitally manipulate data.

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“…3 The presence of this group is indicative of the existence of hexamine. The peak at the region of 1500-1520 cm-' is due to a phenolic ring substituted in ortho and para po~itions.~ The intensity decreases with increasing hexamine and indicates that the depletion of mono-and disubstituted phenolic rings is brought about by crosslinking.…”

Section: Curing Behaviormentioning

confidence: 98%

Optimal compositions of molded phenolic resins and its properties

Chiang¹,

Yang²

1989

J of Applied Polymer Sci

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SynopsisPhenolic resins [commercial (CP), pure (PP), and woodflour-filled (WP)] corrtaining different levels of hexamine, were evaluated in terms of curing behavior as well as thermal, electrical, and mechanical Properties. The degree and rate of curing increase markedly with the rise of the hexamine content; however, the dielectric constant, dielectric loss, and dissipation factor decrease gradually. Dielectrical values decrease with the increase of the applied frequency. When the ratios of hexamine to phenolics are increased, samples become harder and experience increased molding shrinkage. With the increase of molding time or temperature, the surface hardness and molding shrinkage improve. The optimal hexamine contents of WP and PP are determined with respect to the above properties. INTRODUCTIONPhenolic resins were the first completely synthetic polymeric materials and have been widely used as engineering plastics because of their good moldability, mechanical and electrical properties, and economical merit. They are generally produced by compounding novolac resins with hexamethylenetetramine (hexamine), woodflour, lubricants, and pigments through a hot roll-milling process. During the production, their flow and curing characteristics, which are thought to dominate moldablility and performance, are largely influenced by heating conditions in the roll-milling process. Phenolic resin performance is usually characterized by curing behavior, thermal analysis, and electrical and mechanical properties, which are dependent on curing time, molding pressure, molding temperature, and heat treatment.An undercured molding, with a low degree of crosslinking, lacks optimal mechanical strength as well as heat and chemical resistance; however, overcured molding leads to embrittlement. Therefore, it is important to obtain the necessary information on conditions which will produce the proper degree of crosslinking.Many test methods have been proposed for judging the degree of crosslinking.' They include water absorption at the boiling point, solvent extraction, recompression molding, electrical resistance, physical properties such as flexural strength and hardness at elevated temperature,and heat distortion temperature. Each method has its advantages and disadvantages; as a result, they are often used in combination depending on the resin type and molding shape.The most popular method is solvent extraction, in which acetone and tetrahydrofuran (THF) are generally used for phenolics. The principle is based on the fact that the amount of extractable resin diminishes with curing.Journal of Applied Polymer Science, Vol. 37, 499-512 (1989) CHIANG AND YANGHowever, this method has the disadvantage of being time consuming, not only in the extraction operation, but also in preparing a pulverized sample for molding. Methods of measuring flow/curing characteristics may be roughly classified into three categories2 (a) tests using a molding press, which may include ASTM cup mold and JIS disk flow test; (b) orifice flow tests, which may ...

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Amines, C=n, and N=o Compounds

Cited by 222 publications

References 45 publications

General theory of spontaneous emission near exceptional points

General theory of spontaneous emission near exceptional points

Infrared analysis of brominated polyethylene single crystals

Optimal compositions of molded phenolic resins and its properties

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