Translating solid state organic synthesis from a mixer mill to a continuous twin screw extruder

YesA study on the translation of a solid-state synthetic reaction from a mechanochemical mixer-mill to a continuous twin-screw extruder is discussed herein. The study highlights some considerations to be made and parameters to be tested in the context of a model fluorination reaction, which is the first organic fluorination to be attempted using extrusion. Upon optimization, which features the first use of grinding auxiliary solids to enable effective synthetic extrusion, the difluorination reaction was successfully translated to the extruder, leading to a 100-fold improvement in Space Time Yield (STY); 29 kg m−3 day−1 in a mixer mill to 3395 kg m−3 day−1 in a twin screw extruder.D. L. B is grateful to the EPSRC for a First Grant (D. L. B. EP/P002951/1), CRD for a studentship award to J. L. H., Queen’s University Belfast for a Visiting Research Fellowship and the School of Chemistry at Cardiff University for generous support. S. L. J. is grateful to EPSRC for support (EP/L019655/1)

A two-armed bandit based scheme for accelerated decentralized learning

The two-armed bandit problem is a classical optimization problem where a decision maker sequentially pulls one of two arms attached to a gambling machine, with each pull resulting in a random reward. The reward distributions are unknown, and thus, one must balance between exploiting existing knowledge about the arms, and obtaining new information. Bandit problems are particularly fascinating because a large class of real world problems, including routing, QoS control, game playing, and resource allocation, can be solved in a decentralized manner when modeled as a system of interacting gambling machines. Although computationally intractable in many cases, Bayesian methods provide a standard for optimal decision making. This paper proposes a novel scheme for decentralized decision making based on the Goore Game in which each decision maker is inherently Bayesian in nature, yet avoids computational intractability by relying simply on updating the hyper parameters of sibling conjugate priors, and on random sampling from these posteriors. We further report theoretical results on the variance of the random rewards experienced by each individual decision maker. Based on these theoretical results, each decision maker is able to accelerate its own learning by taking advantage of the increasingly more reliable feedback that is obtained as exploration gradually turns into exploitation in bandit problem based learning. Extensive experiments demonstrate that the accelerated learning allows us to combine the benefits of conservative learning, which is high accuracy, with the benefits of hurried learning, which is fast convergence. In this manner, our scheme outperforms recently proposed Goore Game solution schemes, where one has to trade off accuracy with speed. We thus believe that our methodology opens avenues for improved performance in a number of applications of bandit based decentralized decision making

Greener dye synthesis: continuous, solvent-free synthesis of commodity perylene diimides by twin-screw extrusion

YesA continuous, scalable, and solvent‐free method for the synthesis of various naphthalic imides and perylene diimides (PDIs) using twin‐screw extrusion (TSE) is reported. Using TSE, naphthalic imides were obtained quantitatively without the need for excess amine reactant or product purification. With good functional‐group tolerance, alkyl and benzyl amine derived PDIs (incl. commercial dyes) were obtained in 50–99 % yield. Use of K2CO3, enabled synthesis of more difficult aniline‐derived PDIs. Furthermore, an automated continuous TSE process for Pigments Black 31 and 32 is demonstrated, with a throughput rate of about 1500 g day−1, corresponding to a space time yield of about 30×103 kg m−3 day−1, which is 1–2 orders of magnitude greater than for solvent‐based batch methods. These methods provide substantial waste reductions and improved efficiency compared to conventional solvent‐based methods.Engineering and Physical Sciences Research Council. Grant Numbers: EP/L019655/1, IAA1718-04-111

Dirichlet sigma models and mean curvature flow

The mean curvature flow describes the parabolic deformation of embedded branes in Riemannian geometry driven by their extrinsic mean curvature vector, which is typically associated to surface tension forces. It is the gradient flow of the area functional, and, as such, it is naturally identified with the boundary renormalization group equation of Dirichlet sigma models away from conformality, to lowest order in perturbation theory. D-branes appear as fixed points of this flow having conformally invariant boundary conditions. Simple running solutions include the paper-clip and the hair-pin (or grim-reaper) models on the plane, as well as scaling solutions associated to rational (p, q) closed curves and the decay of two intersecting lines. Stability analysis is performed in several cases while searching for transitions among different brane configurations. The combination of Ricci with the mean curvature flow is examined in detail together with several explicit examples of deforming curves on curved backgrounds. Some general aspects of the mean curvature flow in higher dimensional ambient spaces are also discussed and obtain consistent truncations to lower dimensional systems. Selected physical applications are mentioned in the text, including tachyon condensation in open string theory and the resistive diffusion of force-free fields in magneto-hydrodynamics.Comment: 77 pages, 21 figure

Diffusive and localization behavior of electromagnetic waves in a two-dimensional random medium

In this paper, we discuss the transport phenomena of electromagnetic waves in a two-dimensional random system which is composed of arrays of electrical dipoles, following the model presented earlier by Erdogan, et al. (J. Opt. Soc. Am. B {\bf 10}, 391 (1993)). A set of self-consistent equations is presented, accounting for the multiple scattering in the system, and is then solved numerically. A strong localization regime is discovered in the frequency domain. The transport properties within, near the edge of and nearly outside the localization regime are investigated for different parameters such as filling factor and system size. The results show that within the localization regime, waves are trapped near the transmitting source. Meanwhile, the diffusive waves follow an intuitive but expected picture. That is, they increase with travelling path as more and more random scattering incurs, followed by a saturation, then start to decay exponentially when the travelling path is large enough, signifying the localization effect. For the cases that the frequencies are near the boundary of or outside the localization regime, the results of diffusive waves are compared with the diffusion approximation, showing less encouraging agreement as in other systems (Asatryan, et al., Phys. Rev. E {\bf 67}, 036605 (2003).)Comment: 8 pages 9 figure

Crystal structure, electronic, and magnetic properties of the bilayered rhodium oxide Sr3Rh2O7

The bilayered rhodium oxide Sr3Rh2O7 was synthesized by high-pressure and high-temperature heating techniques. The single-phase polycrystalline sample of Sr3Rh2O7 was characterized by measurements of magnetic susceptibility, electrical resistivity, specific heat, and thermopower. The structural characteristics were investigated by powder neutron diffraction study. The rhodium oxide Sr3Rh2O7 [Bbcb, a = 5.4744(8) A, b = 5.4716(9) A, c = 20.875(2) A] is isostructural to the metamagnetic metal Sr3Ru2O7, with five 4d electrons per Rh, which is electronically equivalent to the hypothetic bilayered ruthenium oxide, where one electron per Ru is doped into the Ru-327 unit. The present data show the rhodium oxide Sr3Rh2O7 to be metallic with enhanced paramagnetism, similar to Sr3Ru2O7. However, neither manifest contributions from spin fluctuations nor any traces of a metamagnetic transition were found within the studied range from 2 K to 390 K below 70 kOe.Comment: To be published in PR

Tri-meson-mixing of π\pi-η\eta-η′\eta' and ρ\rho-ω\omega-ϕ\phi in the light-cone quark model

The radiative transition form factors of the pseudoscalar mesons {$\pi$, $\eta$, $\eta'$} and the vector mesons {$\rho$, $\omega$, $\phi$} are restudied with $\pi$-$\eta$-$\eta'$ and $\rho$-$\omega$-$\phi$ in tri-meson-mixing pattern, which is described by tri-mixing matrices in the light-cone constituent quark model. The experimental transition decay widths are better reproduced with tri-meson-mixing than previous results in a two-mixing-angle scenario of only two-meson $\eta$-$\eta'$ mixing and $\omega$-$\phi$ mixing.Comment: 8 pages, 6 figures, final version to appear in EPJ

Electroweak Radiative Corrections to Associated WH and ZH Production at Hadron Colliders

Higgs-boson production in association with W or Z bosons, p pbar -> WH/ZH + X, is the most promising discovery channel for a light Standard Model Higgs particle at the Fermilab Tevatron. We present the calculation of the electroweak O(alpha) corrections to these processes. The corrections decrease the theoretical prediction by up to 5-10%, depending in detail on the Higgs-boson mass and the input-parameter scheme. We update the cross-section prediction for associated WH and ZH production at the Tevatron and at the LHC, including the next-to-leading order electroweak and QCD corrections, and study the theoretical uncertainties induced by factorization and renormalization scale dependences and by the parton distribution functions.Comment: 32 pages, LaTeX, 21 figures. Uses axodraw.sty and feynarts.sty. Added reference