O-diphenylmethylation of alcohols and carboxylic acids using diphenylmethyl diphenyl phosphate as alkylating agent

Diphenylmethyl diphenyl phosphate reacts quickly under mild conditions with various alcohols and carboxylic acids towards diphenylmethyl ethers and esters respectively while hydroxyacids can be selectively alkylated at the alcohol site.     

Analysis of photo-chemical degradation behaviour of polyethylene mulching film with pro-oxidants

It is generally accepted that polyolefins are bioinert. The last years, a new class of photodegradable polyethylene films with pro-oxidants has been developed, exhibiting optimised operational properties in terms of controlled UV and/or thermal ageing leading to an abrupt, predefined to some extent, rapid fragmentation into very small fragments. These photodegradable or fragmentable polyethylene films are promoted in the market for various commercial applications. In some cases, these materials are presented as, or are claimed to be, biodegradable materials. Such materials are already used in agriculture in the form of photodegradable mulching films which become fragmented into small remains after the end of their useful lifetime and are incorporated into the soil. However, it has not been verified yet beyond any doubt, that these remains do in fact biodegrade in natural soil, under what conditions, at which rate and what are their effects in agricultural production, the soil and the environment. An experimental investigation has been carried out focusing on the combined effects of critical factors on the controlled (predefined) photo-chemical degradation of photodegradable mulching LLDPE films with pro-oxidants and the behaviour of their remains in the soil. The analysis of the photo-chemical degradation behaviour presented in this paper was carried out through parallel experiments performed under real field and controlled laboratory conditions. The main factors investigated include materials, exposure time, temperature and UV radiation.     

Large-Eddy Simulations of Spray a Flames Using Explicit Coupling of the Energy Equation with the FGM Database

This paper provides a numerical study on n-dodecane flames using Large-Eddy Simulations (LES) along with the Flamelet Generated Manifold (FGM) method for combustion modeling. The computational setup follows the Engine Combustion Network Spray A operating condition, which consists of a single-hole spray injection into a constant volume vessel. Herein we propose a novel approach for the coupling of the energy equation with the FGM database for spray combustion simulations. Namely, the energy equation is solved in terms of the sensible enthalpy, while the heat of combustion is calculated from the FGM database. This approach decreases the computational cost of the simulation because it does not require a precise computation of the entire composition of the mixture. The flamelet database is generated by simulating a series of counterflow diffusion flames with two popular chemical kinetics mechanisms for n-dodecane. Further, the secondary breakup of the droplet is taken into account by a recently developed modified version of the Taylor Analogy Breakup model. The numerical results show that the proposed methodology captures accurately the main characteristics of the reacting spray, such as mixture formation, ignition delay time, and flame lift-off. Additionally, it captures the “cool flame" between the flame lift-off and the injection nozzle. Overall, the simulations show differences between the two kinetics mechanisms regarding the ignition characteristics, while similar flame structures are observed once the flame is stabilised at the lift-off distance.

     

The equilibrium limit of a constitutive model for two-phase granular mixtures and its numerical approximation

In this paper we analyze the equilibrium limit of the constitutive model for two-phase granular mixtures introduced in Papalexandris (2004) [13], and develop an algorithm for its numerical approximation. At, equilibrium, the constitutive model reduces to a strongly coupled, overdetermined system of quasilinear elliptic partial differential equations with respect to the pressure and the volume fraction of the solid granular phase. First we carry a perturbation analysis based on standard hydrostatic-type scaling arguments which reduces the complexity of the coupling of the equations. The perturbed system is then supplemented by an appropriate compatibility condition which arises from the properties of the gradient operator. Further, based on the Helmholtz decomposition and Ladyzhenskaya’s decomposition theorem, we develop a projection-type, Successive-Over-Relaxation numerical method. This method is general enough and can be applied to a variety of continuum models of complex mixtures and mixtures with micro-structure. We also prove that this method is both stable and consistent hence, under standard assumptions, convergent. The paper concludes with the presentation of representative numerical results.     

Multilayer metal/metal-oxide diffractive structure for photonic temperature sensing

We designed and fabricated multilayer metal/metal-oxide surface relief diffractive grating structures by growing alternating Pt and SnO(x) layers. Optical interrogation at 633 nm reveals the temperature dependence of their reflection and transmission diffractive effects. This function is explored here in the context of a remote, spatially localized, photonic temperature sensing operation, achieving sensitivity of 10% per °C for the zeroth-order in the transmission mode. The experimental demonstration is found to be in good agreement with the results of rigorous coupled wave analysis of the composite metal/metal-oxide element.     

On the applicability of Stokes’ hypothesis to low-Mach-number flows

Continuum Mechanics and Thermodynamics - Stokes’ hypothesis states that the bulk viscosity of a Newtonian fluid can be set to zero. Although not valid for many fluids, it is common practice...     

Design and evaluation of polymer matrices for the encapsulation of CdSe/ZnS quantum dots in photonic nanocomposite thin films

A systematic approach and a new scheme for the evaluation of the as–is encapsulation of CdSe/ZnS core/shell quantum dots into polymer matrices is proposed, aiming to the implementation of thin film photonic integrated structures. Work focuses on quantum dots capped by hexadecylamine and trioctylphosphine oxide with no ligand exchange or other intermediate processing steps involved. The polymers studied include poly(methyl–methacrylate) (PMMA), polystyrene and acrylic polymers incorporating long alkyl chains, which are expected to promote the compatibility of the quantum dot ligands to that of the polymer chains. In this approach, the variation of photoluminescence properties of the nanocomposite thin films is measured versus increased concentration of the quantum dots, so as to evaluate the suitability of each polymer structure as an efficient host. Furthermore, the refractive index of the quantum dots/polymer nanocomposite thin films are also estimated using white light reflectance spectroscopy data, as appropriate for the integration of photonic devices. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 552–560     

Use of ethyl oxamate for syntheses of oxamato(-1) and novel μ-oxamato(-2) complexes

Summary The use of ethyl oxamate for the synthesis of inorganic oxamato complexes is reported. A reaction system leading to the preparation of the novel polymeric -oxamato(-2) complexes [M(oxm)(H₂O)₂] _x (M=Cu, Zn, Cd), [Co(oxm)(H₂O)₂] _x ·0.5xH₂O and [Ni(oxm)(H₂O)₂] _x ·xH₂O is described (H₂ oxm = oxamic acid). Ethyl oxamate can also be used for the preparation of monomeric oxamato(-1) complexes.

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Der Einsatz von Ethyloxamat für die Synthese von Oxamato(-1) und neuen -Oxamato(-2)-Komplexen (Kurze Mitt.)

Zusammenfassung Es wird der Einsatz von Ethyloxamat für die Synthese von anorganischen Oxamato-Komplexen beschrieben. Ein Reaktions-System für die Herstellung von neuen -Oxamato(-2)-Komplexpolymeren: [M(oxm)(H₂O)₂] _x ; (M = Cu, Zn, Cd), [Co(oxm)(H₂O)₂] _x ·0.5xH₂O und [Ni(oxm)(H₂O)₂] _x ·xH₂O, wird vorgestellt. Ethyloxamat kann auch für die Herstellung von monomeren Oxamato(-1)-Komplexen verwendet werden.

     

Contact Transcleral Ciliary Body Photodynamic Therapy with Verteporfin in Pigmented Rabbits: Effect of Repeated Treatments

We studied the effect on the intraocular pressure (IOP) and the ciliary body (CB) morphology after four consecutive contact transcleral photodynamic treatments of the ciliary body (CB-PDT) with verteporfin in pigmented rabbits. Twenty-two pigmented rabbits underwent CB-PDT (study group), performed once (six rabbits) or repeated for up to four times (16 rabbits). Six additional rabbits received only laser treatment without photosensitizer administration (control group). CB-PDT was performed in one eye in rabbits of the study group, with the fellow eye serving as internal control. Verteporfin dosage was 1 mg kg ⁻¹ as bolus injection and laser settings were 40 mW (600 μm core optical fiber) for 1.5 min per spot, for 10 spots. In repeated CB-PDT, treatments were performed in 4-day intervals. Daily IOP measurements were recorded. Histological studies were performed at selected time points. An IOP reduction, more sustained following repeated treatments, was detected in all treated eyes but not in fellow eyes or in the control group. On the average, the IOP was restored to pretreatment levels 4 days after the last treatment. No serious adverse events were observed and the CB architecture was intact at the end of the experiment. Repeated CB-PDT is safe and results in a short-term reduction of IOP. Induced CB alterations are reversible.     

Structural characteristics of detonation expansion from a small channel to a larger one

We report on numerical simulations of the evolution of two-dimensional detonation waves that are expanded from a small channel to a larger one. In accordance with experimental data, the simulations predict three different types of evolution, namely, supercritical, critical and subcritical detonations. In a supercritical detonation, the reaction zone remains always attached to the precursor shock, whereas in a critical one it temporarily detaches and then re-attaches to the front. In the subcritical type, the extinction is permanent, i.e., the detonation quenches. The effects of the fuel’s activation energy and the channel-width ratio are studied via a parametric study. It is found that sufficiently large values of these two parameters can result to flows of the critical and even the subcritical type. Finally, three-dimensional simulations have also been performed and are briefly discussed herein.