Melem

B27. Beutler, E., Westwood, B., Melemed, A., Borgo, P. D., and Margolis, D Three new exon 10 glucose-6-phosphate dehydrogenase mutations. Blood Cells Mol. Dis. 21,64-72 (1995). 

Melamine and its salts are widely used in formulations of fire retardant additives, particularly of the intumescent type (4-71. The role played by melamine structures in these additives is however not yet understood. The thermal behaviour is of paramount importance in studies of the fire retardance mechanism. It is known that melamine undergoes progressive condensation on heating with elimination of ammonia and formation of polymeric products named "melam", "melem", "melon" (8.91. The following schematic reaction is reported in the literature (10-121 ... 

The by-product ammonium bromide is shown to volatilise in similar conditions in TG. This is a different behaviour altogether from that of melamine in whose thermal condensation melam can be isolated with difficulty only in carefully controlled experimental conditions (11.17). Indeed melem is the condensation product most easily isolated and this led some authors to doubt that melam could be an intermediate product of the condensation of melamine to melem and melon (19.22). 

Melem (l834LA(10)lo), empirical formula CeHUNio, is probably 2,5,8-triamino-l,3,4,6,7,9-hexaaza[3.3.3]cyclazine (280), but no conclusive evidence concerning the structure has been presented. 

Recently, Leonard and coworkers (82JA5497) reported the synthesis and spectral and structural features of the hexaazacyclazine (29), the parent ring system of melem (see Section 2.20.3.8). 

The first command use opens on disk drive A the database file flame which contains the characteristics for the flame method. Then the element Tl and the concentration (0.02 micro g/ml) one wants to analyze are stored in two memory variables melem and mconc , respectively. 

Melemed, A.S., Winer, E. and Hudis, C. (2003) Phase II, randomized, doubleblind study of two dose levels of arzoxifene in patients with locally advanced or metastatic breast cancer. Journal of Clinical Oncology, 21, 1007-1014. 

McMeekin, D.S., Gordon, A., Fowler, J., Melemed, A., Buller, R., Burke,T., Bloss, J. and Sabbatini, P. (2003) A phase II trial of arzoxifene, a selective estrogen response modulator, in patients with recurrent or advanced endometrial cancer. Gynecologic Oncology, 90, 64—69. 

The fluidizing gas leavesthe reactortogetherwith gaseous melamine and the byproducts ammonia, carbon dioxide, isocyanic acid and traces of melem. The gas also contains entrained catalyst fines. Melem is separated by desublimation and is removed together with the catalyst fines in a gas filter. 

Albain KS, Nag SM, Calderillo-Ruiz G, Jordaan JP, Llombart AC, Pluzanska A, Rolski J, Melemed AS, Reyes-Vidal JM, Sekhon JS, Simms L, O Shaughnessy J. Gemcitabine plus paclitaxel versus pacli-taxel monotherapy in patients with metastatic breast cancer and prior anthracycline treatment. J Clin Oncol 2008 26(24) 3950-7. 

FIGURE 11.8 Crystal structure of a graphitic carbon nitride sheet constructed from melem units and electronic structure of the Kohn-Sham orbitals for the VB and CB of polymeric melon. Reprinted with permission from Ref. [37]. Nature Publishing Group. 

Melamine [108-78-1]. This inexpensive solid melts with vaporization at about 350°C and, if evaporation is constrained, decomposition also occurs to ammonia and nonvolatile condensation products— melam, melem, and eventually melone. It is occasionally used by itself as a flame retardant but more often used as a blowing agent and flame-retardant adjuvant in intumescent coatings, elastomers, and plastic formulations (138) as well as in flexible polyurethane foams (139,140). 

The combustion behavior of melamine pyrophosphate and dimelamine phosphate are different from those of melamine and the other melamine salts (Table 3.4.1). The former are ineffective at low concentrations (> 15%) and become effective at a loading of 20-30% because the intumescent char is formed on the surface of burning specimens. The mechanism of fire retardant action of both melamine pyrophosphate and dimelamine phosphate is similar to that of APP since, by analogy with ammonia melamine volatilizes, whereas the remaining phosphoric acids produce esters with nylon-6, which are precursors of the char [146]. Some part of the freed melamine condenses probably forming melem and melon [147]. 

Upon heating, to whatever extent it does not sublime away, melamine can undergo progressive condensation with evolution of ammonia and formation of thermally stable condensates, known as melam, melem, and melon. This reaction competes with melamine volatilization and is more pronounced if the volatilization of melamine is impeded for example, by trapping in the charred polymer. 

Hydrogen-bonded 2D networks were also observed for two triamines, melamine and melem. Here too, depending on the applied potential, either disorganized monolayers or highly ordered monolayers of differing surface density were observed (Figure 20.26). 

Uemura, S. Aono, M. Komatsu, T. Kunitake, M. 2011. Two-dimensional self-assembled structures of melamine and melem at the aqueous solution-Au(l 11) interface. Langmuir 27 1336-1340. 

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