Enhanced para-xylene selectivity in the toluene alkylation reaction at ultralow contact time

Dramatic improvements in the para-xylene selectivity of the toluene alkylation reaction can be effected by operating the catalytic reaction at ultralow contact time. Unexpectedly, the rate of alkylation is sustained, while unwanted side reactions are suppressed. By demonstrating that contact time directly influences the fate of para-xylene, which is known to form and diffuse preferentially within the zeolite catalyst, we conclude that external mass transfer is a key parameter in controlling selectivity. Even non-optimized catalysts can be made to achieve near-perfect selectivity, without sacrificing conversion.     

Heat conduction in laminates with a weak transversal inhomogeneity

The purpose of this contribution is to formulate a tolerance model, [1], for periodically laminated media with a weak transversal inhomogeneity. Laminates in which layers are of the same material but one of them is reinforced by thin fibers in parallel to the interfaces are this kind of media. Taking into account the weak transversal inhomogeneity makes possible to separate model equations for the averaged temperature and temperature fluctuations. To analyse and solve these equations we apply asymptotic expansions. Using the proposed model selected initial-boundary value problems were solved. Results were verified by direct numerical solutions obtained in the framework of the Fourier model. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optimization of the dynamic blanking process

In this paper an optimization of the dynamic blanking process with using E-PLANNER, ANSYS and MATLAB programmes was presented. The main aim of this work was to obtain the high quality of the cut surface in function of: the size of clearance between punch and die, value of fillet radius of the punch edge and the speed of blanking. Numerical analyses were conducted in Ansys LS-Dyna programme, with use of the explicit method and the experiment plan had been done before. Five levels rotary plan, was used. Unknown coefficients in mathematical model in the shape of quadratic equation with interactions were obtained. Obtained regression function was optimized in MATLAB programme, and determined optimal conditions of the process parameters. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Water-window microscopy using a compact, laser-plasma SXR source based on a double-stream gas-puff target

We report on a compact, desktop size, laboratory type microscopy setup, based on a short wavelength gas puff target soft X-ray source, which emits incoherent radiation in “water-window” spectral range. The microscope employs a Wolter type I reflective objective and allows capturing magnified images of objects with ~1-μm spatial resolution and exposure time as low as 5 s. A detailed characterization and optimization of both the source and the microscope setups are presented and discussed.     

Hydrogen chemisorption on carbon structure with mixed sp2–sp3 hybridization: empirical potential studies

Hydrogen storage is a key technology for the advancement of hydrogen and fuel cell power technologies in transportation, stationary, and portable applications. The currents state of art shows that there is no existing material which could be used as efficient storage medium. In this paper we present a new concept of a non-conventional engineering storage solution. It is based on the recent theoretical and experimental discoveries which show existence of a new meta-stable phase of graphite with mixed sp²–sp³ hybridization called diaphite. By means of the molecular dynamics calculations with adaptive intermolecular reactive empirical bond order potential empirical potential we show that the increase of the hydrogen-carbon binding energy on diaphite is related to the transformation of local bonds geometry from sp² hybridization to sp³. We propose and discuss a scenario of fully reversible photo-stimulated process of adsorption/desorption of hydrogen on/of diaphite.     

First order strong approximations of scalar SDEs defined in a domain

We are interested in strong approximations of one-dimensional SDEs which have non-Lipschitz coefficients and which take values in a domain. Under a set of general assumptions we derive an implicit scheme that preserves the domain of the SDEs and is strongly convergent with rate one. Moreover, we show that this general result can be applied to many SDEs we encounter in mathematical finance and bio-mathematics. We will demonstrate flexibility of our approach by analyzing classical examples of SDEs with sublinear coefficients (CIR, CEV models and Wright–Fisher diffusion) and also with superlinear coefficients (3/2-volatility, Aït-Sahalia model). Our goal is to justify an efficient Multilevel Monte Carlo method for a rich family of SDEs, which relies on good strong convergence properties.     

Atomic-scale friction on stepped surfaces of ionic crystals

We report on high-resolution friction force microscopy on a stepped NaCl(001) surface in ultrahigh vacuum. The measurements were performed on single cleavage step edges. When blunt tips are used, friction is found to increase while scanning both up and down a step edge. With atomically sharp tips, friction still increases upwards, but it decreases and even changes sign downwards. Our observations extend previous results obtained without resolving atomic features and are associated with the competition between the Schw?bel barrier and the asymmetric potential well accompanying the step edges.     

Enhanced CO2 binding affinity of a high-uptake rht-type metal-organic framework decorated with acylamide groups

An rht-type metal-organic framework (MOF) prepared from M(2)(carboxylate)(4) (M = Cu, Co) paddlewheel clusters and a flexible C(3)-symmetric hexacarboxylate ligand with acylamide groups exhibits larger CO(2) uptake, an enhanced heat of adsorption, and higher selectivity toward CO(2)/N(2) in comparison with what was previously observed for an analogous MOF with alkyne groups.     

A Corrole‐Based Covalent Organic Framework Featuring Desymmetrized Topology

Herein, for the first time, we present the successful synthesis of a novel two‐dimensional corrole‐based covalent organic framework (COF) by reacting the unusual approximately T‐shaped 5,10,15‐tris(p‐aminophenyl)corrole H₃TPAPC with terephthalaldehyde, which adopts desymmetrized hcb topology and consists of a staggered AB stacking structure with elliptical pores. The resultant corrole‐based COF, TPAPC‐COF , exhibits high crystallinity and excellent chemical stability. The combination of extended π‐conjugated backbone and interlayer noncovalent π–π interactions endows TPAPC‐COF with excellent absorption capability in the entire visible‐light and even near‐infrared regions. Moreover, this work suggests the promise of TPAPC‐COF as a new class of photoactive material for efficient singlet‐oxygen generation with potential photodynamic therapy application as demonstrated by in vitro anticancer studies.