Applications of spectral analysis in medical ultrasonography.

Spectral analysis of ultrasonic reflections from biological tissues can be used to determine basic tissue parameters for use in differential diagnosis. This paper describes the use of the technique under circumstances encountered in several types of clinical examinations. The applications are illustrated with results obtained from laboratory measurements with a system now being employed in a clinical evaluation programme. The test objects studied simulate tissues with planar boundaries, tissues with heterogeneous interior structure, and tissues causing acoustic 'shadowing' of posterior regions.     

Stability and collapse of localized solutions of the controlled three-dimensional Gross-Pitaevskii equation

On the basis of recent investigations, a newly developed analytical procedure is used for constructing a wide class of localized solutions of the controlled three-dimensional (3D) Gross-Pitaevskii equation (GPE) that governs the dynamics of Bose-Einstein condensates (BECs) in the presence of a spatio-temporally varying external potential. The controlled 3D GPE is decomposed into a two-dimensional (2D) linear Schr?dinger equation (called the `transverse equation’) and a one-dimensional (1D) nonlinear Schr?dinger equation (called the `longitudinal equation’), constrained by a variational condition for the controlling potential. The latter corresponds to the requirement for the minimization of the control operation in the transverse plane. Then, the above class of localized solutions are constructed as the product of the solutions of the transverse and longitudinal equations. A consistency condition between the transverse and longitudinal solutions yields a relationship between the transverse and longitudinal restoring forces produced by the external trapping potential well through a `controlling parameter’ (i.e. the average, with respect to the transverse profile, of the nonlinear inter-atomic interaction term of the GPE). It is found that the longitudinal profile supports localized solutions in the form of bright, dark or grey solitons with time-dependent amplitudes, widths and centroids. The related longitudinal phase is varying in space and time with time-dependent curvature radius and wavenumber. In turn, all the above parameters (i.e. amplitudes, widths, centroids, curvature radius and wavenumbers) can be easily expressed in terms of the controlling parameter. It is also found that the transverse profile has the form of Hermite-Gauss functions (depending on the transverse coordinates), and the explicit spatio-temporal dependence of the controlling potential is self-consistently determined. On the basis of these exact 3D analytical solutions, a stability analysis is carried out, focusing our attention on the physical conditions for having collapsing or non-collapsing solutions.     

Comprehensive analysis of glycated human serum albumin tryptic peptides by off-line liquid chromatography followed by MALDI analysis on a time-of-flight/curved field reflectron tandem mass spectrometer

Glycated peptides arising from in vivo digestion of glycated proteins, usually called advanced glycation end (AGE) product peptides, are biologically relevant compounds due to their reactivity towards circulating and tissue proteins. To investigate their structures, in vitro glycation of human serum albumin (HSA) has been performed and followed by enzymatic digestion. Using different MALDI based approaches the digestion products obtained have been compared with those arising from enzymatic digestion of the protein. Results obtained using 2,5-dihydroxybenzoic acid (DHB) indicate this as the most effective matrix, leading to an increase in the coverage of the glycated protein. Off-line microbore liquid chromatography prior to MALDI analysis reveals that 63% of the free amino groups amenable to glycation are modified. In addition, the same approach shows the co-presence of underivatised peptides. This indicates that, regardless of the high glucose concentration employed for HSA incubation, glycation does not go to completion. Tandem mass spectrometric data suggest that the collision induced dissociation of singly charged glycated peptides leads to specific fragmentation pathways related to the condensed glucose molecule. The specific neutral losses derived from the activated glycated peptides can be used as signature for establishing the occurrence of glycation processes.     

Positrons and electrons in primary cosmic rays as measured in the PAMELA experiment

The PAMELA experiment is being carried out on board the Russian satellite Resurs DK1 placed in the near-earth near-polar orbit on June 15, 2006. The apparatus comprising a silicon-strip magnetic spectrometer and an electromagnetic calorimeter allows measurement of electron and positron fluxes in cosmic rays in a wide energy interval from ～100 MeV to hundreds of GeV. The high-energy electron and positron separation technique is discussed and the data on positron-to-electron ratio in primary cosmic rays up to E ≈ 10 GeV from the 2006–2007 measurements are reported in this work.     

Solvation effects on the stability of silver(I) complexes with pyridine-containing ligands studied by thermodynamic and DFT methods

The formation of Ag(I) complexes with 2,2'-bipyridine (bipy), 2,2'6',2' '-terpyridine (terpy), 2-(aminomethyl)pyridine (amp), and bis((2-pyridyl)methyl)amine (dpa) is studied in dimethyl sulfoxide (dmso) by means of potentiometric and calorimetric measurements. Enthalpy-stabilized mononuclear MLj complexes are formed, whereas entropy changes counteract complex formation. Additionally, a comparison with analog Ag-polyamine species is made to evidence the significant different coordination behavior of these classes of ligands. The results are discussed in terms of different basicity and steric requirements of the ligands and solvation effects. The dpa ligand, with an unprecedented coordination pattern, forms also a bimetallic complex [Ag2(dpa)2]2+ that has been structurally characterized in the solid state by X-ray diffraction. The influence of solvent, water and dmso, on the binding energy of the monodentate pyridine to Ag(I) has also been assessed by means of density functional theory (DFT) calculations. This study has been extended also in vacuum to the reaction of Ag(I) with the simple monoamine methylamine (mea). These results are correlated with the experimental evidence and used to interpret the different affinities of pyridine for the Ag(I) ion in the two media.     

Modulation instability of lower hybrid waves leading to cusp solitons in electron–positron(hole)–ion Thomas Fermi plasma

Following the idea of three‐wave resonant interactions of lower hybrid waves, it is shown that quantum‐modified lower hybrid (QLH) wave in electron–positron–ion plasma with spatial dispersion can decay into another QLH wave (where electron and positrons are activated, whereas ions remain in the background) and another ultra‐low frequency quantum‐modified ultra‐low frequency Lower Hybrid (QULH) (where ions are mobile). Quantum effects like Bohm potential and Fermi pressure on the lower hybrid wave significantly reshaped the dispersion properties of these waves. Later, a set of non‐linear Zakharov equations were derived to consider the formation of QLH wave solitons, with the non‐linear contribution from the QLH waves. Furthermore, modulational instability of the lower hybrid wave solitons is investigated, and consequently, its growth rates are examined for different limiting cases. As the growth rate associated with the three‐wave resonant interaction is generally smaller than the growth associated with the modulational instability, only the latter have been investigated. Soliton solutions from the set of coupled Zakharov and NLS equations in the quasi‐stationary regime have been studied. Ordinary solitons are an attribute of non‐linearity, whereas a cusp soliton solution featured by nonlocal nonlinearity has also been studied. Such an approach to lower hybrid waves and cusp solitons study in Fermi gas comprising electron positron and ions is new and important. The general results obtained in this quantum plasma theory will have widespread applicability, particularly for processes in high‐energy plasma–laser interactions set for laboratory astrophysics and solid‐state plasmas.