A New Cells‐Compatible Microfluidic Device for Single Channel Recordings

We report the fabrication of a microfluidic apparatus and the realization of a sensors based on PEDOT : PSS, a biocompatible semiconductor polymer used in substitution of standard electrodes for electrophysiological studies and for detection of nanopores in membrane. This gives the possibility to study the mechanisms of ions balance and molecular transport though cell membranes. In particular the apparatus is based on two chambers connected through an aperture in a PTFE sheet where lipid bilayer are formed using Montal‐Mueller method, and the pore‐forming proteins activity is detected by polymeric electrodes. This methodology could be applied to examine different membrane proteins for the purpose of biosensing, drug screening and nanopore technologies.     

On certain linear spaces of nilpotent matrices

In this note we describe explicitly those linear spaces of nilpotent matrices, which are stable under conjugation by diagonal matrices. As an application, we deduce a generalized version of a result of Valcher and Fornasini on pairs of nonnegative nilpotent matrices.     

Scattering of 1 and 2 MeV neutrons from oriented 165Ho

The “deformation effect” in the neutron-¹⁶⁵Ho differential scattering cross section, defined as the relative variation of the cross section induced by the orientation of the target, has been measured at 1 and 2 MeV incident neutron energy, in the scattering angular interval from 30° to 130°. A polycrystalline holmium target has been employed, oriented normally to the scattering plane, with a nuclear alignment parameter $\text{B}{}_2\text{B}{}_{\mathrm{<mtext>2\; </mtext><mtext>max</mtext>}}\text{= 0.24}$. The observed effect has an oscillating character as a function of the scattering angle with a maximum value of 0.12 ± 0.02 at 2 (emMeV). The effect has been theoretically calculated by an adiabatic coupled-channel calculation performed by using the optical model and deformation parameters deduced from the analysis of previous experiments. The agreement between the experimental and the theoretical results is good, particularly at 2 MeV energy where the compound nucleus contribution in the scattering is negligible.     

Dynamics of plasma blobs in a shear flow

The global dynamic of plasma blobs in a shear flow is investigated in a simple magnetized torus using the spatial Fourier harmonics (k-space) framework. Direct experimental evidence of a linear drift in k space of the density fluctuation energy synchronized with blob events is presented. During this drift, an increase of the fluctuation energy and a production of the kinetic energy associated with blobs are observed. The energy source of the blob is analyzed using an advection-dissipation-type equation that includes blob-flow exchange energy, linear drift in k space, nonlinear processes, and viscous dissipations. We show that blobs tap their energy from the dominant ExB vertical background flow during the linear drift stage. The exchange of energy is unidirectional as there is no evidence that blobs return energy to the flow.     

Efficient removal of DNA from proteomic samples prior to two-dimensional map analysis

Several methods have been described in the literature for removal of DNA from protein samples prior to proteome analysis. They in general involve protein precipitation techniques. In other protocols, DNAse treatment is suggested prior to precipitation of proteins in excess acetone. All these methods have been evaluated and found to perform poorly in DNA removal, as illustrated by two-dimensional (2D) maps where horizontal and vertical sample streaking are still substantial. Such removal is in general necessary in tissue lysates and especially when analysing sub-cellular organelles, such as nuclei, where the high DNA levels strongly interfere with proteome analysis. Another method is proposed here for efficient DNA removal: two-phase extraction of DNA in chloroform/phenol/isoamyl alcohol, a procedure commonly used to rid DNA samples of protein contaminants, but rarely applied to protein preparation. This extraction is not very efficient if performed at slightly acidic to neutral pH values, but it performs extremely well at pH values of 9.5 or higher. The 2D maps thus obtained of Escherichia coli lysates as well as extracts from purified nuclei of eukaryotic cells are not only devoid of any vertical or horizontal streaking, but exhibit many more spots, especially in the alkaline region of the 2D gels, suggesting that these basic proteins were in general lost to proteome analysis due to co-precipitation in tenacious protein–DNA complexes. It is hypothesized that the alkaline pH values adopted in the two-phase extraction help to fully disrupt any residual DNA–protein complexes, due to strong Coulombic repulsion.     

Ion cyclotron electrostatic waves in a low-temeprature low-density magnetized plasma

Summary The electrostatic dispersion relation for a low-temperature, low-density magnetized plasma has been studied in the range of the ion cyclotron frequency and its first harmonics. The presence of a forward wave and of an infinite number of backward waves has been shown. The characteristics of propagation of these modes and the possibility of conversion are analysed.

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Riassunto Viene studiata la relazione di dispersione elettrostatica relativa ad un plasma magnetizzato di bassa densità e di bassa temperatura nel campo della frequenza ciclotronica ionica e delle sue prime armoniche. Si mostra la presenza di un unico modo forward e di un insieme infinito di modi backward. Si analizzano le caratteristiche di propagazione di queste onde e la possibilità di conversioni tra di esse.

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Резюме Исследуется электростатическое дисперсионное соотношение для намагниченной плазмы с низкой температурой и низкой плотностью в области ионной циклотронной частоты и ее первой гармоники. Показывается наличие единственной моды в направлении вперед и бесконечного числа волн в обратном направлении. Анализируются характеристики распространения этих мод и возможность конверсии.