Goniopolarimetry: Space-borne radio astronomy with imaging capabilities

The principles of space-based low-frequency radio astronomy (below 50 MHz) are briefly introduced. As the wavelength range considered does not allow the use of focusing systems, goniopolarimetric (or direction-finding) techniques have been developed. These inversion techniques provide the direction of the wave vector, the polarization state and the flux of the observed electromagnetic wave. In case of spatially extended sources, we can also infer an order of magnitude of the apparent source size. These techniques are presented, and their limitations are discussed. An example from a recent study illustrates the techniques and capabilities.     

Effect of epitaxial crystallization on packet-like space charge characteristics in low-density polyethylene under multi-field coupling conditions

In order to study the effect of epitaxial crystallization on charge transport in low-density polyethylene (LDPE) under multi-field coupling conditions, three typical epitaxial crystallizations, namely disorder (glass substrate), crossover (isotactic polypropylene substrate), and parallel (polytetrafluoroethylene substrate), were prepared and denoted as LD-G, LD-iPP, and LD-PT, respectively. Packet-like space charge through samples was analyzed by the pulsed electro-acoustic (PEA) method. It is shown that different microscopic surface morphologies appeared in the LDPE samples with different epitaxial crystallizations, which, however, do not change the crystalline structure of the bulk. Packet-like space charge phenomena were observed and the distortion field increased with the temperature which could be attributed to the larger amount of charge injection in a shorter period. The differences of the amount and injection rate of the space charge were explained and verified considering the typical chain alignment of epitaxial crystallization, which, in our opinions, contributes to the pass over of positive charge in LD-iPP samples.     

Extreme fluxes in solar energetic particle events: Methodological and physical limitations

In this study, all available data on the largest solar proton events (SPEs), or extreme solar energetic particle (SEP) events, for the period from 1561 up to now are analyzed. Under consideration are the observational, methodological and physical problems of energy-spectrum presentation for SEP fluxes (fluences) near the Earth's orbit. Special attention is paid to the study of the distribution function for extreme fluences of SEPs by their sizes. The authors present advances in at least three aspects: 1) a form of the distribution function that was previously obtained from the data for three cycles of solar activity has been completely confirmed by the data for 41 solar cycles; 2) early estimates of extremely large fluences in the past have been critically revised, and their values were found to be overestimated; and 3) extremely large SEP fluxes are shown to obey a probabilistic distribution, so the concept of an “upper limit flux” does not carry any strict physical sense although it serves as an important empirical restriction. SEP fluxes may only be characterized by the relative probabilities of their appearance, and there is a sharp break in the spectrum in the range of large fluences (or low probabilities). It is emphasized that modern observational data and methods of investigation do not allow, for the present, the precise resolution of the problem of the spectrum break or the estimation of the maximum potentialities of solar accelerator(s). This limitation considerably restricts the extrapolation of the obtained results to the past and future for application to the epochs with different levels of solar activity.     

Dispersion and localisation in structured Rayleigh beams

This paper brings a comparative analysis between dynamic models of couple-stress elastic materials and structured Rayleigh beams on a Winkler foundation. Although physical phenomena have different physical origins, the underlying equations appear to be similar, and hence mathematical models have a lot in common. In the present work, our main focus is on the analysis of dispersive waves, band-gaps and localised waveforms in structured Rayleigh beams. The Rayleigh beam theory includes the effects of rotational inertia which are neglected in the Euler–Bernoulli beam theory. This makes the approach applicable to higher frequency regimes. Special attention is given to waves in pre-stressed Rayleigh beams on elastic foundations.     

A new approach to pointwise heat kernel upper bounds on doubling metric measure spaces

On doubling metric measure spaces endowed with a strongly local regular Dirichlet form, we show some characterisations of pointwise upper bounds of the heat kernel in terms of global scale-invariant inequalities that correspond respectively to the Nash inequality and to a Gagliardo–Nirenberg type inequality when the volume growth is polynomial. This yields a new proof and a generalisation of the well-known equivalence between classical heat kernel upper bounds and relative Faber–Krahn inequalities or localised Sobolev or Nash inequalities. We are able to treat more general pointwise estimates, where the heat kernel rate of decay is not necessarily governed by the volume growth. A crucial role is played by the finite propagation speed property for the associated wave equation, and our main result holds for an abstract semigroup of operators satisfying the Davies–Gaffney estimates.     

How to Obtain the Maximum Properties Flexibility of 3D Printed Ketoprofen Tablets Using Only One Drug-Loaded Filament?

The flexibility of dose and dosage forms makes 3D printing a very interesting tool for personalized medicine, with fused deposition modeling being the most promising and intensively developed method. In our research, we analyzed how various types of disintegrants and drug loading in poly(vinyl alcohol)-based filaments affect their mechanical properties and printability. We also assessed the effect of drug dosage and tablet spatial structure on the dissolution profiles. Given that the development of a method that allows the production of dosage forms with different properties from a single drug-loaded filament is desirable, we developed a method of printing ketoprofen tablets with different dose and dissolution profiles from a single feedstock filament. We optimized the filament preparation by hot-melt extrusion and characterized them. Then, we printed single, bi-, and tri-layer tablets varying with dose, infill density, internal structure, and composition. We analyzed the reproducibility of a spatial structure, phase, and degree of molecular order of ketoprofen in the tablets, and the dissolution profiles. We have printed tablets with immediate- and sustained-release characteristics using one drug-loaded filament, which demonstrates that a single filament can serve as a versatile source for the manufacturing of tablets exhibiting various release characteristics.     

Comparative analysis of CR-39 sensitivity for different sets of measurable track parameters

In the present paper the sensitivity V of plastic nuclear track detectors CR-39 to the space radiation, accelerated heavy ions in wide LET range and α-particles is studied. Different approaches for V evaluation are considered and compared. Main attention is given to the method that is appropriate for the measurement of short range heavy secondaries of space radiation. Finally, the experimental verification of the designed V function is carried out via simulation of the secondaries with low energy α-particles in the vicinity of the Bragg peak.     

Tailoring the polarity of polymer shell on BaTiO_3 nanoparticle surface for improved energy storage performance of dielectric polymer nanocomposites

Nanocomposites comprising flexible polymers and high dielectric constant inorganic nanoparticles are considered to be one of the promising candidates for electrostatic capacitor dielectrics.However,the effect of interfacial property on electrical ene rgy storage of dielectric polymer nanocomposites is still not clear.Herein,the role of the polarity of the interfacial region is investigated.For this purpose,three polymers with different polarity,polymethyl methacrylate(PMMA),polyglycidyl methacrylate,and polymethylsulfonyl ethyl methacrylate(PMSEMA) are attached onto BaTi03(BT) na noparticle surface via surface-initiated reversible addition-fragmentation chain transfer polymerization.It is found that the polarity of shell polymers shows an apparent effect on the dielectric and energy storage of dielectric polymer nanocomposites.For example,PMSEMA@BT(shell polymer possesses the highest polarity)increases dielectric loss and decreases the breakdown strength of the nanocomposites,leading to lower ene rgy storage capability.However,PMMA@BT(shell polymer possesses the lowest polarity) can induce higher breakdown strength of the nanocomposites.As a result,the PMMA@BT nanocomposite exhibits the highest electrical energy sto rage capability among the three nanocomposites.This re search provides new insight into the design of core-shell nanofillers for dielectric energy storage applications.     

A new characterization of the Berger sphere in complex projective space

We give a complete classification of Lagrangian immersions of homogeneous 3-manifolds (the Berger spheres, the Heisenberg group ${\text{Nil}}_3$, the universal covering of the Lie group $\text{PSL}(2,\mathbb{R})$ and the Lie group ${\text{Sol}}_3$) in 3-dimensional complex space forms. As a corollary, we get a new characterization of the Berger sphere in complex projective space.     

Non-contact in-situ pulsed electro acoustic method for the analysis of charge transport in irradiated space-used polymers

The characterization of dielectric materials in space environment requires to understand and predict their electric behaviour, taking into account ionisation, and ageing effect (through electron or UV radiation, thermal cycling, …)For this purpose, new methods have been developed for the characterisation and qualification of space materials and satellite structure. These studies led initially to the development of dedicated facilities for the simulation of representative irradiation conditions. This work is focused on a new non-disturbing technique for the measurement of charge distribution within space irradiated polymers. This technique named PEA (Pulsed Electro-Acoustic) has been implemented in the irradiation facility for in-situ and real time measurement during irradiation and relaxation of polymer materials. Implementation and validation of this technique are presented and discussed in this paper.