Hoffman process

Hoffman (Urea) Process. The overall reaction for the Hoffman process is ... 

S.E. George, and D.C. Hoffman, Process for preparing copolyesters, US Patent 5378796, assigned to Eastman Chem. Co., January 3,1995. 

Hoechst slurry process Hoeppler viscometer Hoffman degradation Hoffman eliminations Hofmann degradation... 

To this point, we have emphasized that the cycle of mobilization, transport, and redeposition involves changes in the physical state and chemical form of the elements, and that the ultimate distribution of an element among different chemical species can be described by thermochemical equilibrium data. Equilibrium calculations describe the potential for change between two end states, and only in certain cases can they provide information about rates (Hoffman, 1981). In analyzing and modeling a geochemical system, a decision must be made as to whether an equilibrium or non-equilibrium model is appropriate. The choice depends on the time scales involved, and specifically on the ratio of the rate of the relevant chemical transition to the rate of the dominant physical process within the physical-chemical system. 

Hoffman AS. A review of the use of radiation plus chemical and biochemical processing treatments to prepare novel biomaterials. Radiat Phys Chem, 1981, 18, 323-342. 

Ammonia has always been the starting material for the synthesis of aliphatic amines. Thus, processes have been developed for the condensation of NH3 with alkyl halides (Hoffman reaction) or with alcohols in the presence of various catalysts. The latter reachon, first discovered by Sabatier in 1909 [8, 9] is nowadays the main method of industrial production of light amines (e.g. methylamines 600 000 t/yr) [5]. 

Hoffman, W., Kiesner, C., Clawin-Radecker, I., Martin, D., Etnhoff, K., Lorenzen, P. C., Meisel, H., Hammer, P., Suhren, G., and Teufel, P. (2006). Processing of extended shelf-life milk using microfiltration. Int. ]. Dairy Technol. 59, 229-235. 

Cereijido M, CA Robbins, DD Sabatini. (1987). Polarized epithelial membranes produced in vitro. In JF Hoffman, ed. Membrane Transport Processes. New York Raven Press, pp 443-456. 

The significant difference in H between FCSCs and ECSCs indicates that the M dependence of V can not be controlled by the self-diffusion process within the melt (the first stage) as proposed by Hoffman et al. [40], but it should be controlled by the surface diffusion process (the second stage) as shown in Fig. 27. 

It should be noted that the critical nucleation process does not depend on M. This can be explained by our model of surface diffusion (Fig. 27). In the model a nucleus will be formed from the absorbed chains. We can estimate the number of repeating units within a critical nucleus (N ) using parameters a, ae, and Ah given in [14]. N is the order of 102-103 for the range of AT in our experiment, which is much smaller than the number of repeating units within a molecule (103-104). This indicates that a critical nucleus should be formed by a part of a molecular chain. Therefore, the nucleation process of the critical nucleus will not depend on M. Thus, it is a natural result that B does not depend on M in this study. This is consistent with the discussion by Hoffman et al. [28] on FCC. They showed that the nucleation process of an FCC does not depend on Mn in the case of Mn > 104. On the contrary they showed that it depends on Mn for Mn < 104, because ae depends on Mn due to the effect of chain ends on the end surface of the critical nucleus. 

According to Hoffman s crystallization theory, a drop in the heat of fusion corresponds to an exponential decrease in nucleation and crystal growth rates [63]. Implicitly, the rate of crystallization is severely retarded by the presence of 3HV comonomer [64, 69, 72]. These low crystallization rates can hamper the melt processing of these copolymers since they necessitate longer processing cycle times. 

Dalton, R. F., Price, R., Ermana, H., and Hoffman, B., in Separation Processes in Hydrometallurgy, Davies, G. A., Ellis Horwood, Chichester, England, 1987, 466. 

Hoffman A process for making hydrazine by reacting urea and sodium hypochlorite in water ... 

Mass spectral studies, including low voltage techniques and accurate mass measurements, have been reported by Hoffman (40) on tetracycline and eight related compounds. As a result of good spectral correlations among these compounds, the major fragmentation processes are discussed in terms of two compounds in the series 5a,6-anhydrotetracycline and... 

The experiments were continued by Hoffman and Whittam, who concluded that a protein, an ATPase, in the membrane was necessary for active transport and was vectorially organized, with ATP and Na+ being required internally and K+ externally where ouabain was inhibitory. The ATPase was finally identified as the sodium pump by Skou (1957) it vectorially translocated Na+ and K+ across the membrane, and was phosphorylated transiently in the process. 

Hoffman, E. J. Azeotropic and Extractive Distillation (Interscience Publishers, Inc., New York, 1964). Holland, C. D. Fundamentals of Multicomponent Distillation (McGraw-Hill Book Co., New York, 1981). King, C. J. Separation Processes, 2nd edn. (McGraw-Hill Book Co., New York, 1981). 

Hoffman advises, Relying solely on a process-specific assay is ill advised and can result in failure to detect atypical process contaminants. In cases with a defined, persistent, and problematic host cell protein impurity, a down-stream process-specific assay may be justified. It is critical that the immunoassay be capable of detecting every possible host cell protein contaminant. 13... 

Rauscher T, Heger A, Hoffman RD, Woosley SE (2002) Nucleosynthesis in massive stars with improved nuclear and stellar physics. Astrophys J 576 323-348 Rayet M (1995) The p-process in type II supemovae. Astron Astrophys 298 517-532 Rayet M, Prantzos N, Amould M (1990) The p-process revisited. Astron Astrophys 227 271-281 Reedy RC, Arnold JR, Lai D (1983) Cosmic-ray record in solar system matter. Science 219 127-135 Rehkamper M, Halliday AN (1999) The precise measurement of T1 isotopic compositions by MC-ICPMS application to the analysis of geological materials and meteorites. Geochim Cosmochim Acta 63 935-944... 

Residua are the dark-colored nearly solid or solid products of petroleum refining that are produced by atmospheric and vacuum distillation (Figure 11.1 Chapter 3). Asphalt is usually produced from a residuum and is a dark brown to black cementitious material obtained from petroleum processing that contains very high-molecular-weight molecular polar species called asphaltenes that are soluble in carbon disulfide, pyridine, aromatic hydrocarbons, and chlorinated hydrocarbons (Chapter 3) (Gruse and Stevens, 1960 Guthrie, 1967 Broome and Wadelin, 1973 Weissermel and Arpe, 1978 Hoffman, 1983 Austin, 1984 Chenier, 1992 Hoffman and McKetta, 1993). 

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