A simplified,miniature TEA-CO2 laser using a semiconductive pre-ionization technique

Using a pre-ionization system based on a silicon carbide compound and a pulse-forming network using a vacuum relay, we have been able to significantly reduce TEA0-CO₂ laser complexity while maintaining high output energy densities. The design and construction are detailed along with the experimentally obtained laser characteristics.     

Novel applications of the “t-amino effect” in heterocyclic chemistry; synthesis of 1-alkylindoles

Thermal rearrangerment of 2-vinyl-1-(1-pyrrolidinyl)benzenes varies with the leaving group ability of substituents in the vinyl moiety; compound 3 having an OR group 9-(alkoxy-methyl)pyrrolo[1,2-a]indoles and compounds 6 (X = OAc, OTs or Cl) yield 1-alkylindoles.     

Existence,uniqueness and continuous dependence for hereditary systems

Summary An hereditary system is a system whose present state is determined in some way by its past history. We formulate a class of such systems which includes functional differential equations of retarded type and many equations of neulral type as well as Volterra integral equations. Theorems of existence, uniqueness, continuation and continuous dependence are proved. Preparation of this paper was sponsored in part by the Office of Naval Research under Contract NONR 233(76). Reproduction in whole or in part is permitted for any purpose of the United States Government. Entrata in Redazione il 22 gennaio 1969.     

A general substructure synthesis method for the dynamic simulation of complex structures

In this paper a general substructure synthesis method is developed for the dynamic analysis of complex flexible structures. The motion of each substructure is represented by a given number of substructure admissible functions. Substructure admissible functions are often low-order polynomials, and hence computationally easy to work with. The otherwise disjoint substructures are connected together to form a whole structure by imposing approximate geometric compatibility conditions by means of the method of weighted residuals. The behavior of the estimated eigenvalues obtained by the substructures synthesis method can be ascertained by means of a bracketing theorem. The estimated eigenvalues do converge to the actual eigenvalues of the original structure, although it is necessary to consider two limiting processes, one in which the number of substructure admissible functions is increased and the other in which the number of internal boundary weighting functions is increased.     

An example of bifurcation to homoclinic orbits

Consider the equation $\text{x}\text{?}\text{? x + x}{}^2\text{= ?λ}{}_1\text{x + λ}{}_2\text{?(t)}\text{where}\text{?(t + 1) = ?(t)}\text{and}\text{λ = (λ}{}_1\text{, λ}{}_2\text{)}$ is small. For λ = 0, there is a homoclinic orbit Γ through zero. For λ ≠ 0 and small, there can be “strange” attractors near Γ. The purpose of this paper is to determine the curves in λ-space of bifurcation to “strange” attractors and to relate this to hyperbolic subharmonic bifurcations.     

Enantioselective formal total synthesis of the antitumor macrolide bryostatin 7

A new enantioselective synthesis of Masamune's AB fragment (1) for bryostatin 7 is described. Key steps in the new route include a Meerwein-Ponndorf-Verley reduction to set the O(7) stereocenter and an alkylative union between the dithiane 6 and iodide 5 to construct the C(9)-C(10) bond. Because we have previously published a synthesis of Masamune's C-ring phenyl sulfone 2, our new route to 1 constitutes a formal total synthesis of bryostatin 7; it also corrects the previously reported spectral data for 1 in CDCl3.     

Changes in the Inter- and Intra- Fibrillar Structure of Lyocell (TENCEL®) Fibers after KOH Treatment

Lyocell fibers were treated with KOH up to 8 M which was demonstrated to distribute homogeneously at the outer zones of fiber cross section compared to NaOH which accesses more deeply but less homogenously. Both NaOH and KOH solutions can be used to lower significantly the fibrillation of lyocell fibers. However, due to intrafibrillar swelling together with deep penetration ability of alkali seen for NaOH treatments results in great fiber tensile strength loss which is not observed for KOH treatments due to its inability to penetrate the fiber completely. The porous structure of fibers was studied by inverse size exclusion chromatography (ISEC) to identify mean pore diameter, total pore area and accessible pore volume (APV). Mean pore diameter of fibers decreased after KOH treatments which did not change after NaOH treatments. Wide angle X-ray diffraction analyses (WAXD) were applied to identify the crystallinity index and crystallite size. In general, fiber properties such as water retention value, carboxyl content using methylene blue sorption method, depth of color measured after dyeing with C.I. Direct Red 81 and weight loss were distinctly different in the ranges up to 2 M, 2-5 M and 5 to 8 M KOH. KOH treatment suggests new possibilities for the pretreatment of lyocell fibers to lower fibrillation while slightly lowering elongation at break without a distinct loss in tensile strength and with less decrease in carboxyl content and weight loss without changing dyeing properties of fibers compared to NaOH treatment.