Temporal analysis of tissue displacement induced by a transient ultrasound radiation force

One of the stress sources that can be used in dynamic elastography imaging methods is the acoustic radiation force. However, displacements of the medium induced by this stress field are generally not fully understood in terms of spatial distribution and temporal evolution. A model has been developed based on the elastodynamic Green's function describing the different acoustic waves generated by focused ultrasound. The function is composed of three terms: two far-field terms, which correspond to a purely longitudinal compression wave and a purely transverse shear wave, and a coupling near-field term which has a longitudinal component and a transverse component. For propagation distances in the shear wavelength range, the predominant term is the near field term. The displacement duration corresponds to the propagation duration of the shear wave between the farthest source point and the observation point. This time therefore depends on the source size and the local shear modulus of the tissue. Evolution of the displacement/time curve profile, which is directly linked to spatial and temporal source profiles, is computed at different radial distances, for different durations of force applications and different shear elastic coefficients. Experimental results performed with an optical interferometric method in a homogeneous tissue-mimicking phantom agreed with the theoretical profiles.     

Über N-(α-Aminoacyl)-sulfonamide, 3. Mitt.

Zusammenfassung dl-3,4-Dibenzyloxy--methyl-phenylalanin wurde aus 3,4-Dibenzyloxy-benzaldehyd nach Standardmethoden hergestellt. Sein N-Carboxy-Anhydrid wurde inDMSO mit den Natriumsalzen von p-Toluolsulfonamid und Methansulfonamid zu den N-Acyl-sulfonamiden umgesetzt, die durch katalytische Hydrierung in die vom Aldomet sich ableitenden N-Acyl-Sulfonamide übergeführt wurden.

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dl-3.4-Dibenzyloxy--methyl-phenylalanine was prepared from 3.4-Dibenzyloxybenzaldehyde by standard methods. Reaction of its N-carboxy anhydride inDMSO with sodium p-toluenesulfonamide and sodium methanesulfonamide yielded the corresponding N-acyl sulfonamides, and subsequent catalytic hydrogenation the N-acyl sulfonamides derived from aldomet.

     

Molecular vibrations and lattice dynamics of ortho-terphenyl

Infrared and Raman spectra of crystalline, melted and solvated ortho-terphenyl and its perdeuterated isotopomer, D₁₄-ortho-tephenyl, have been recorded. Optimized geometries and vibrational frequencies were calculated by the semiempirical RHF/AM1 method and by DFT using the B3LYP functional and 6–31G(d) basis set. In both cases the lowest energy conformation is of C₂ symmetry. With the scaled AM1 and B3LYP/6-31G(d) force fields the average error in reproducing the experimental molecular vibrational frequencies is 13cm^?1 and 5cm^?1, respectively. The AM1 potential energy surface for phenyl torsions was mapped on a 15° grid. The barrier to concerted internal rotation is estimated to lie between 3 kJ mol^?1 and 6kJ mol^?1. The calculations of the lattice dynamics at k = 0 in the low temperature fully ordered crystal phase of parent and deuterated ortho-terphenyl were performed with inclusion of six low lying intramolecular vibrations. The conformational change of the ortho-terphenyl molecule induced by crystal packing forces was taken into account by re-defining the unperturbed molecular vibrational state. Although an accurate assignment of lattice vibrations was not possible, the calculated spectra give quite a reasonable picture of the low frequency dynamics in crystalline ortho-terphenyl. The relevance of the results obtained to the glass forming property of ortho-terphenyl is discussed.     

A technique for measuring Lagrangian and Eulerian particle statistics in a turbulent flow

An experimental technique is described which has been developed to study particle dispersion in a round turbulent jet. Droplets are injected on the jet axis, and a laser sheet and position sensitive photomultiplier tube are used to track their radial displacement. Data processing is greatly simplified compared to video or photo imaging techniques which provide similar measurements. Statistically large samples are used to calculate dispersion and axial velocity as a function of axial downstream distance or particle time-of-flight. Dispersion and velocity statistics can be computed which are Lagrangian or Eulerian in nature. The technique has been demonstrated with 69 m droplets of hexadecane in a jet of air with a Reynolds number of 15,000; in principle it could be used to study the motion of very small, quasi-fluid particles.     

Über N-(α-Aminoacyl)-sulfonamide, 1. Mitt.

Zusammenfassung Es wird über die Synthese von N-Phenylalanyl-p-toluolsulfonamid und N-Phenylalanyl-methansulfonamid berichtet, die durch Reaktion verschiedener carboxyl-aktivierter Derivate des rac. N-t-Butoxycarbonyl-phenylalanins mit p-Toluolsulfonamidnatrium und Methansulfonamid-natrium durchgeführt wird.

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Carboxyl activated derivatives of rac. N-t-butoxycarbonyl phenylalanine react with Na p-toluenesulfonamide and Na methanesulfonamide to give the corresponding N-phenylalanyl sulfonamides.

     

Bellman Systems with Mean Field Dependent Dynamics

The authors deal with nonlinear elliptic and parabolic systems that are the Bellman like systems associated to stochastic differential games with mean field dependent dynamics. The key novelty of the paper is that they allow heavily mean field dependent dynamics. This in particular leads to a system of PDE’s with critical growth, for which it is rare to have an existence and/or regularity result. In the paper, they introduce a structural assumptions that cover many cases in stochastic differential games with mean field dependent dynamics for which they are able to establish the existence of a weak solution. In addition, the authors present here a completely new method for obtaining the maximum/minimum principles for systems with critical growths, which is a starting point for further existence and also qualitative analysis.     

Photo‐ and Electrocatalytic H2 Production by New First‐Row Transition‐Metal Complexes Based on an Aminopyridine Pentadentate Ligand

The synthesis and characterisation of the pentadentate ligand 1,4‐di(picolyl)‐7‐(p‐toluenesulfonyl)‐1,4,7‐triazacyclononane (Py₂^Tstacn) and their metal complexes of general formula [M(CF₃SO₃)(Py₂^Tstacn)][CF₃SO₃], (M=Fe ( 1_Fe ), Co ( 1_Co ) and Ni ( 1_Ni )) are reported. Complex 1_Co presents excellent H₂ photoproduction catalytic activity when using [Ir(ppy)₂(bpy)]PF₆ ( PS_Ir ) as photosensitiser (PS) and Et₃N as electron donor, but 1_Ni and 1_Fe result in a low activity and a complete lack of it, respectively. On the other hand, all three complexes have excellent electrocatalytic proton reduction activity in acetonitrile, when using trifluoroacetic acid (TFA) as a proton source with moderate overpotentials for 1_Co (0.59 V vs. SCE) and 1_Ni (0.56 V vs. SCE) and higher for 1_Fe (0.87 V vs. SCE). Under conditions of CH₃CN/H₂O/Et₃N (3:7:0.2), 1_Co (5 μM ), with PS_Ir (100 μM ) and irradiating at 447 nm gives a turnover number (TON) of 690 (n/n) and initial turnover frequency (TOF) (TON×t^?1) of 703 h^?1 for H₂ production. It should be noted that 1_Co retains 25 % of the catalytic activity for photoproduction of H₂ in the presence of O₂. The inexistence of a lag time for H₂ evolution and the absence of nanoparticles during the first 30 min of the reaction suggest that the main catalytic activity observed is derived from a molecular system. Kinetic studies show that the reaction is ?0.7 order in catalyst, and time‐dependent diffraction light scattering (DLS) experiments indicate formation of metal aggregates and then nanoparticles, leading to catalyst deactivation. By a combination of experimental and computational studies we found that the lack of activity in photochemical water reduction by 1_Fe can be attributed to the 1_Fe ^II/I redox couple, which is significantly lower than the PS_Ir ^III/II , while for 1_Ni the pK_a value (?0.4) is too small in comparison with the pH (11.9) imposed by the use of Et₃N as electron donor.     

Critical properties of non-spherical molecule fluids from the virial expansion

Critical constants of pure fluids (as important reference data in constructing vapour-liquid phase diagrams and basic input of various estimation methods) were determined for systems of non-spherical Kihara molecules; values of the critical temperature, density, compression factor and pressure of fluids composed of prolate and oblate molecules were evaluated from the fourth-order virial expansion. The second and third virial coefficients of the Kihara molecules were determined by applying the recently proposed method in which the effect of molecular core geometry and functional dependence of a pair interaction on the surface-surface distance are factorized and the former contribution determined from a formula for the corresponding hard convex body virial coefficient. The virial expansion for non-spherical Kihara molecules is applied to determine the critical constants of n-alkanes (methane to octane) and cyclic hydrocarbons (cyclopentane, cyclohexane, benzene and naphthalene); a fair agreement with experimental data was found.