Modeling of electrodynamic-mechanical coupling phenomena in smart magnetoelectroelastic materials

The coupling of electric, magnetic and mechanical phenomena may have various reasons. The famous Maxwell equations of electrodynamics describe the interaction of transient magnetic and electric fields. On the constitutive level of dielectric materials, coupling mechanisms are manyfold comprising piezoelectric, magnetostrictive or magnetoelectric effects. Electromagnetically induced specific forces acting at the boundary and within the domain of a dielectric body are, within a continuum mechanics framework, commonly denoted as Maxwell stresses. In transient electromagnetic fields, the Poynting vector gives another contribution to mechanical stresses. First, a system of transient partial differential equations is presented. Introducing scalar and vector potentials for the electromagnetic fields and representing the mechanical strain by displacement fields, seven coupled differential equations govern the boundary value problem, accounting for linear constitutive equations of magnetoelectroelasticity. To reduce the effort of numerical solution, the system of equations is partly decoupled applying generalized forms of Coulomb and Lorenz gauge transformations [1,2]. A weak formulation is given to establish a basis for a finite element solution. The influence of constitutive magnetoelectric coupling on electromagnetic wave propagation is finally demonstrated with a simple one-dimensional example. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Analysis of the vibrational spectra of chiral liquid crystalline thioesters

Vibrational spectra of (S)-(+)-4-(1-methylheptyloxy)biphenyl 4-pentylphenylthiobenzoate (MHOBS5) were calculated using the density functional theory method, with two different basis sets, the 6-31G* and the 6-31+G*. The force fields were scaled using the scaled quantum-mechanical force field (SQM) procedure. Various sets of scaling factors for the SQM procedure are discussed. Results of simulations were used to analyse the experimental data obtained from infrared and Raman experiments for MHOBS5 and the homologous MHOBS4.     

Reference point approximation method for the solution of bicriterial nonlinear optimization problems

This paper presents a reference point approximation algorithm which can be used for the interactive solution of bicriterial nonlinear optimization problems with inequality and equality constraints. The advantage of this method is that the decision maker may choose arbitrary reference points in the criteria space. Moreover, a special tunneling technique is given for the computation of global solutions of certain subproblems. Finally, the proposed method is applied to a mathematical example and a problem in mechanical engineering.     

Quantum control of the hyperfine spin of a Cs atom ensemble

We demonstrate quantum control of a large spin angular momentum associated with the F=3 hyperfine ground state of 133Cs. Time-dependent magnetic fields and a static tensor light shift are used to implement near-optimal controls and map a fiducial state to a broad range of target states, with yields in the range 0.8-0.9. Squeezed states are produced also by an adiabatic scheme that is more robust against errors. Universal control facilitates the encoding and manipulation of qubits and qudits in atomic ground states and may lead to the improvement of some precision measurements.     

Generation of a library of particles having controlled sizes and shapes via the mechanical elongation of master templates

Herein we describe a versatile and readily scalable approach for the fabrication of particles with a variety of shapes and sizes from a single master template by augmenting the particle replication in nonwetting templates (PRINT) method with mechanical elongation. Repetition of the elongation steps in one direction leads to the fabrication of linear particles with high aspect ratio (AR), over 40 times greater than in the original master, while a range of particle shapes can be obtained by repeating the elongation procedure while changing the stretching direction, generating diamond, rectangular, curved parallelogram particles from a single cubic master.     

Effect of aspect ratio and deformability on nanoparticle extravasation through nanopores

We describe the fabrication of filamentous hydrogel nanoparticles using a unique soft lithography based particle molding process referred to as PRINT (particle replication in nonwetting templates). The nanoparticles possess a constant width of 80 nm, and we varied their lengths ranging from 180 to 5000 nm. In addition to varying the aspect ratio of the particles, the deformability of the particles was tuned by varying the cross-link density within the particle matrix. Size characteristics such as hydrodynamic diameter and persistence length of the particles were analyzed using dynamic light scattering and electron microscopy techniques, respectively, while particle deformability was assessed by atomic force microscopy. Additionally, the ability of the particles to pass through membranes containing 0.2 μm pores was assessed by means of a simple filtration technique, and particle recovery was determined using fluorescence spectroscopy. The results show that particle recovery is mostly independent of aspect ratio at all cross-linker concentrations utilized, with the exception of 96 wt % PEG diacrylate 80 × 5000 nm particles, which showed the lowest percent recovery.     

Site-selective modification of proteins for the synthesis of structurally defined multivalent scaffolds

A combination of classical site-directed mutagenesis, genetic code engineering and bioorthogonal reactions delivered a chemically modified barstar protein with one or four carbohydrates installed at specific residues. These protein conjugates were employed in multivalent binding studies, which support the use of proteins as structurally defined scaffolds for the presentation of multivalent ligands.     

Biaxial order and a rotation of the minor director in the nematic phase of an organo-siloxane tetrapode by the electric field

Biaxiality in the nematic phase for a liquid crystalline tetrapode made up of organo-siloxanes mesogens is investigated using polarized infrared spectroscopy. An ordering of the minor director for the homeotropically aligned sample is found to depend on the amplitude of the in-plane electric field. On increasing the in-plane electric field, the minor director, lying initially along the rubbing direction, rotates to the direction of the applied field. The scalar order parameters of the second rank tensor are found to depend significantly on the strength of the electric field. A most significant increase is found in the nematic order parameter and in the parameter that characterizes the phase biaxiality.     

Estimation of trace elements in some medicinal plants used in anti‐cancer drugs by PIXE

A trace elemental analysis was carried out in various parts of 12 anticancer medicinal plants, using the PIXE (particle‐induced X‐ray emission) technique. A 3‐MeV proton beam was used to excite the samples, and spectra were recorded using a Si (Li) detector. Data analysis was done using the GUPIX software. The elements Cl, K, Ca, Ti, V, Mn, Fe, Ni, Cu, Zn, Br and Sr were identified, and their concentrations estimated. The results of the present study provide justification for the usage of these medicinal plants in the development of anticancer drugs. Copyright © 2012 John Wiley & Sons, Ltd.