44,413 research outputs found
A Unified Gravity-Electroweak Model Based on a Generalized Yang-Mills Framework
Gravitational and electroweak interactions can be unified in analogy with the
unification in the Weinberg-Salam theory. The Yang-Mills framework is
generalized to include space-time translational group T(4), whose generators
T_{\mu}(=\p/\p x^{\mu}) do not have constant matrix representations. By
gauging in flat space-time, we have a new
tensor field which universally couples to all particles and
anti-particles with the same constant , which has the dimension of length.
In this unified model, the T(4) gauge symmetry dictates that all wave equations
of fermions, massive bosons and the photon in flat space-time reduce to a
Hamilton-Jacobi equation with the same `effective Riemann metric tensor' in the
geometric-optics limit. Consequently, the results are consistent with
experiments. We demonstrated that the T(4) gravitational gauge field can be
quantized in inertial frames.Comment: 12 pages. To be published in "Modern Physics Letters A
Trimerization of aromatic nitriles
Triazine compounds and cross-linked polymer compositions were made by heating aromatic nitriles to a temperature in the range of about 100 C to about 700 C, in the presence of a catalyst or mixture of catalysts. Aromatic nitrile-modified (terminated and/or appended) imide, benzimidazole, imidazopyrrolone, quinoxaline, and other condensation type prepolymers or their precopolymers were made which were trimerized with or without a filler by the aforementioned catalytic trimerization process
New methods for preparing N,N-dialkyltrifluoroacetamides
The customary preparative methods for N,N-dialkyltrifluoroacetamides involve the acylation of an amine by trifluoroacetic acid or its derivatives. The synthesis of N,N-dialkyltrifluoroacetamides by reacting trifluoroacetic anhydride or acid with disubstituted formamides and acetamides is discussed. These reactions were interpreted with the aid of gas chromatographic analysis. Different reaction mechanisms are proposed for the reactions of formamides and acetamides with trifluoroacetic anhydride or acid. The use of the proposed reaction mechanisms for the synthesis of other fluorinated compounds is discussed
Electrochemical fluorination of trichloroethylene and N, N-dimethyltrifluoroacetamide
Fluorination of trichloroethylene and N, N-dimethyltrifluoroacetamide was carried out on a laboratory scale in an advanced Simons type electrochemical apparatus which could be operated automatically from ambient to 50 psi pressure. A variety of fluorine-substituted products are formed, depending upon electrolysis conditions and concentrations of reactant relative to the NaF, KF, HF electrolyte. A new reaction mechanism of electrochemical fluorination of trichloroethylene is proposed. The solvency-to-fluorine content relationship of fluorinated N, N-dimethyltrifluoroacetamide is described
Catalytic trimerization of aromatic nitriles for synthesis of polyimide matrix resins
Aromatic nitriles may be trimerized at moderate temperature and pressure with p-toluenesulfonic acid as catalyst. Studies were conducted to establish the effect of the reaction temperature, pressure, time, and catalyst concentration on yield of the trimerized product. Trimerization studies were also conducted to establish the effect of substituting electron donating or withdrawing groups on benzonitrile. Preliminary results of using the catalytic trimerization approach to prepare s-triazine cross-linked polyimide/graphite fiber composites are presented
Synthesis of ultrahigh molecular-weight poly/ethylene terrephthalate/
Solid state polymerization technology for synthesis of ultrahigh molecular weight polyethylene terephthalat
Post-Apocalyptic Geographies and Structural Appropriation
Excerpt from Routledge Companion to Transnational American Studies, edited by Nina Morgan, Alfred Hornung, and Takayuki Tatsum
Internal coating of air-cooled gas turbine blades
Four modified aluminide coatings were developed for IN-792 + Hf alloy using a powder pack method applicable to internal surfaces of air-cooled blades. The coating compositions are Ni-19Al-1Cb, Ni-19Al-3Cb, Ni-17Al-20Cr, and Ni-12Al-20Cr. Cyclic burner rig hot corrosion (900 C) and oxidation (1050 C) tests indicated that Ni-Al-Cb coatings provided better overall resistance than Ni-Al-Cr coatings. Tensile properties of Ni-19Al-1Cb and Ni-12Al-20Cr coated test bars were fully retained at room temperature and 649 C. Stress rupture results exhibited wide scatter around uncoated IN-792 baseline, especially at high stress levels. High cycle fatigue lives of Ni-19Al-1Cb and Ni-12Al-20Cr coated bars (as well as RT-22B coated IN-792) suffered approximately 30 percent decrease at 649 C. Since all test bars were fully heat treated after coating, the effects of coating/processing on IN-792 alloy were not recoverable. Internally coated Ni-19Al-1Cb, Ni-19Al-3Cb, and Ni-12Al-20Cr blades were included in 500-hour endurance engine test and the results were similar to those obtained in burner rig oxidation testing
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