An experimentally based analytical model for the shear capacity of FRP-strengthened reinforced concrete beams

This paper deals with the shear strengthening of Reinforced Concrete (RC) flexural members with externally bonded Fiber-Reinforced Polymers (FRPs). The interaction between an external FRP and an internal transverse steel reinforcement is not considered in actual code recommendations, but it strongly influences the efficiency of the shear strengthening rehabilitation technique and, as a consequence, the computation of interacting contributions to the nominal shear strength of beams. This circumstance is also discussed on the basis of the results of an experimental investigation of rectangular RC beams strengthened in shear with “U-jacketed” carbon FRP sheets. Based on experimental results of the present and other investigations, a new analytical model for describing the shear capacity of RC beams strengthened according to the most common schemes (side-bonded and “U-jacketed”), taking into account the interaction between steel and FRP shear strength contributions, is proposed. Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 3, pp. 339–356, May–June, 2008.     

Chiral 1,3-oxathianes via stereoselective addition-cyclization of hydroxythiols to electron-poor acetylenes

A novel preparation of chiral 1,3-oxathianes via nucleophilic addition of hydroxy-thiols to electron-poor acetylenes, followed by iodine catalyzed photoinduced cyclization is reported. The stereochemical outcome of the reaction is determined with a conformational study based on n.O.e. ¹H-NMR differential spectroscopy experiments.     

Development of XUV lasers at the RAL Central Laser Facility

Recent progress in the development of XUV lasers by research teams using high-power and ultrashort-pulse Nd: glass and KrF laser facilities at the Rutherford Appleton Laboratory is reviewed. Injector-amplifier operation and prepulse enhanced output of the Ge XXIII collisional laser driven by a kilojoule glass laser, enhanced gain in CVI recombination with picosecond CPA drive pulses from a glass laser, and optical field ionization and XUV harmonic generation with a KrF CPA laser are described.     

Quadratic Interaction Functional for General Systems of Conservation Laws

For the Glimm scheme approximation \({u_\varepsilon}\) to the solution of the system of conservation laws in one space dimension

$$u_t + f(u)_x = 0, \qquad u(0, x) = u_0(x) \in \mathbb{R}^n,$$

with initial data u ₀ with small total variation, we prove a quadratic (w.r.t. Tot. Var. (u ₀)) interaction estimate, which has been used in the literature for stability and convergence results. No assumptions on the structure of the flux f are made (apart from smoothness), and this estimate is the natural extension of the Glimm type interaction estimate for genuinely nonlinear systems.

More precisely, we obtain the following results:

• a new analysis of the interaction estimates of simple waves;
• a Lagrangian representation of the derivative of the solution, i.e., a map \({\mathtt{x}(t, w)}\) which follows the trajectory of each wave w from its creation to its cancellation;
• the introduction of the characteristic interval and partition for couples of waves, representing the common history of the two waves;
• a new functional \({\mathfrak{Q}}\) controlling the variation in speed of the waves w.r.t. time.

This last functional is the natural extension of the Glimm functional for genuinely nonlinear systems.

The main result is that the distribution \({D_{t} \hat \sigma_k(t,w)}\) is a measure with total mass \({\leq \mathcal{O}(1) {\rm Tot. Var.} (u_0)^2}\) , where \({\hat{\sigma}_k(t, w)}\) is the speed given to the wave w by the Riemann problem at the grid point \({(i\varepsilon, \mathtt{x}(i\varepsilon, w)), t \in [i\varepsilon, (i + 1)\varepsilon)}\).     

Enantioselective Oxidation of Thioethers. An Improved Route to the Resolution of [1,1′-Binaphthalene]-2,2′-Dithiol

Abstract

(±)-[1,1′-Binaphthalene]-2,2′-bis-methylthioether (±)-1 was oxidized with high enantioselectivity by using our asymmetric reagent [Ti(IV) : (+)-DET : TBHP = 1 : 4 : 2]. An appropriate substrate/oxidant ratio afforded such a product distribution that allowed us to obtain, after chromatographic separation and chemical transformations, optically pure [1,1′-binaphthalene]-2,2′-dithiol in ca. 80% yield based on the racemic starting material.     

Properties of a new thermoplastic fluorinated polymer

The properties of a new thermoplastic polymer, tetrafluoroethylene-ethylene copolymer (TE) are reported. It is a crystalline thermoplastic melting around 275 and contains essentially alternating monomer units with minor amounts of additional perfluorinated units. The copolymer has excellent mechanical properties both at low and high temperature; it exhibits moderate stiffness, good toughness and good creep behaviour. Dielectric constant and loss factor are low; chemical, thermal and weather resistance are good. TE is particularly suited for extrusion applications, especially for electrical insulation purposes and for chemical applications.     

Evidence of a S N -2-set continuum in the oxidation of organic sulfides by peroxovanadium complexes

The oxidation of di-n-butyl sulfide and phenylmethyl sulfide by two vanadium (V) peroxocomplexes, e.g. VO(O₂)OCH₃, 1, and VO(O₂)(PIC)(H₂O)₂, 2, in methanol, was investigated. The kinetic analysis of the reactions revealed significant mechanistic differences between the two peroxometal oxidants. In particular, 1 behaves as an electrophilic oxidant so that the transition state of sulfide oxidations by 1 may be described as a S _N 2 displacement on the peroxide oxygen whereas 2 acts as a radical oxidant in a process which has a substantial SET character. The role of the picolinaoo ligand in determining the reactivtty of 2 is discussed in terms of a decrease of the electrophilicity of the peroxide oxygen compared with 1 and of a stabilization of the radical metal species.     

1,1-Bis(benzenesulfonyl)ethylene: A synthetic equivalent of ethylene 1,2-dipole

1,1-Bis(benzenesulfonyl)ethylene (1) acts as a synthetic equivalent of ethylene 1,2-dipole as it gives with olefins products derived from a postulated dipolar reaction mechanism that can be readily desulfonylated into the formal ethylene adducts.