Retarded equations on the sphere induced by linear equations

Using a Poincaré compactification, the linear homogeneous system of delay equations {x = Ax(t ? 1) (A is an n × n real matrix) induces a delay system π(A) on the sphere Sⁿ. The points at infinity belong to an invariant submanifold S^{n ? 1} of Sⁿ. For an open and dense set of 2 × 2 matrices A with distinct eigenvalues, the system π(A) has only hyperbolic critical points (including the critical points at infinity). For an open and dense set of 2 × 2matrices $\text{A}$ with complex eigenvalues, the nonwandering set at infinity is the union of an odd number of hyperbolic periodic orbits; if $\text{(}\text{det}\text{A}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{<}\text{3π}\text{2}$, the restriction of $\text{π(}\text{A}\text{)}$ to S¹ is Morse-Smale. For n = 1 there exist periodic orbits of period 4 provided that $\text{?A >}\text{π}\text{2}$ and Hopf bifurcation of a center occurs for ?A near $\text{(}\text{π}\text{2}\text{) + 2kπ, k ? Z}$.     

The estimation of relaxation times from out-of-phase detected EPR spectra

A method is described by which the saturation-transfer electron paramagnetic resonance technique may be employed to determine values of T₁ and T₂ from experimental spectra. The effect of higher harmonics of the modulation field on the calculated out-of-phase spectrum is computed. The results suggest that the inclusion of higher harmonics is important to ensure that well-characterized values of especially T₂ may be obtained.     

Angular studies of potential electron emission in the interaction of slow ions with Al surfaces

We report energy distributions of electrons emitted from Al surfaces under impact by 1 keV Ar+ and 1-5 keV Ne+ ions. The variation of the energy distributions with the angle of incidence is different for both ions and provides information on the mechanism responsible for electron emission. For Ar+ electron emission results mainly from Auger neutralization, while for Ne+ an important emission mechanism is the decay of plasmon excitations. We find a transition between surface and bulk plasmon excitations as the energy of the ion is increased.     

Nitrogen ion implantation in single wall carbon nanotubes

We report an X-ray photoemission and electron energy loss study on 3 keV ion implantation in single wall carbon nanotubes. Our results show that nitrogen atoms can bind to carbon in tetrahedral sp³, defects related pyridine-like, and triangular sp² configurations and such bondings are stable for annealing up to 650 K. Heating at higher temperatures results in preferential substitutional nitrogen doping. This technique opens a new channel for controlled doping in carbon nanotubes for device applications.     

Use of bacterial cellulose in the textile industry and the wettability challenge—a review

Bacterial cellulose (BC) has been studied as an alternative material in several segments of the food, pharmaceutical, materials and textile industries. The importance of BC is linked to sustainability goals, since it is an easily degradable biomaterial of low toxicity to the environment and is a renewable raw material. For use in the textile area, bacterial cellulose has attracted great interest from researchers, but it presents some challenges notably to its hydrophilic structure. This integrative review article brings together studies and methods related to minimizing the hydrophilicity of bacterial cellulose, in order to expand its applicability in the textile industry in its dry state. The databases consulted were Scopus, ScienceDirect, ProQuest and Web of Science, the documents investigated were scientific articles and the time period investigated was between 2015 and 2021. The results showed that although there are methods to make the BC membrane more hydrophobic, future studies in this regard and on other properties must continue so that bacterial cellulose can be commercially introduced in the textile sector.

     

Water perturbed by cellophane: comparison of its physicochemical properties with those of water perturbed with cotton wool or Nafion

We present experimental data on water repetitively brought in contact with cellophane. Although this hydrophilic polymer is insoluble in water, repetitively immersing it in water changes the liquid’s properties. We compare the physicochemical properties of the water left over after removing the cellophane to those of previously published data on water repetitively brought in contact with other in water insoluble polymers (cotton wool or Nafion). Some of the properties are similar. All the properties considerably differ from those of the Milli-Q^® water used. On lyophilizing these waters, solid residues remain. The residues are soluble in water. The chemical nature of the residues differs from that of the perturbing polymers.