Convergent close-coupling method for positron scattering from noble gases

We present the convergent close-coupling formulation for positron scattering from noble gases (Ne, Ar, Kr and Xe) within the single-center approximation. Target functions are described in a model of six p-electrons above an inert Hartree–Fock core with only one-electron excitations from the outer p6 shell allowed. Target states have been obtained using a Sturmian (Laguerre) basis in order to model coupling to ionization and positronium (Ps) formation channels. Such an approach is unable to yield explicit Ps-formation cross sections, but is valid below this threshold and above the ionization threshold. The present calculations are found to show good agreement with recent measurements

TELAMON: Effelsberg Monitoring of AGN Jets with Very-High-Energy Astroparticle Emissions -- II. Polarization properties

We present recent results of the TELAMON program, which is using the Effelsberg 100-m telescope to monitor the radio spectra of active galactic nuclei (AGN) under scrutiny in astroparticle physics, namely TeV blazars and neutrino-associated AGN. Our sample includes all known Northern TeV-emitting blazars as well as blazars positionally coincident with IceCube neutrino alerts. Polarization can give additional insight into the source properties, as the polarized emission is often found to vary on different timescales and amplitudes than the total intensity emission. Here, we present an overview of the polarization properties of the TeV-emitting TELAMON sources at four frequencies in the 20 mm and 7 mm bands. While at 7 mm roughly $82\,\%$ of all observed sources are found to be significantly polarized, for 20 mm the percentage is $\sim58\,\%$. We find that most of the sources exhibit mean fractional polarizations of $<5\%$, matching the expectations of rather low polarization levels in these sources from previous studies at lower radio frequencies. Nevertheless, we demonstrate examples of how the polarized emission can provide additional information over the total intensity.Comment: 9 pages, 2 figures, Proceedings of the 38th International Cosmic Ray Conference (ICRC2023

Characterization and Use of Replication Competent HIV-1 Genomes Carrying Fluorescent Reporter Genes

HIV envelop genes specify which types of host cells the virus can infect. HIV clones carrying five different patient envelopes and two kinds of fluorescent reporter genes were constructed to develop tools for investigating viral tropisms. The data demonstrated that the new constructs showed the expected macrophage tropic or non-macrophage tropic phenotype and were detectable by FACS analysis. In future experiments, these clones will be extremely useful in evaluating whether highly macrophage-tropic envelopes confer a broader tropism among CD4-positive T-cell populations in blood lymphocyte cultures, and whether they out compete viral clones carrying non-macrophage tropic envelopes

An advanced test strategy for boosted modal survey testing of non-linear space structures

The dynamic qualification of today´s space structures is performed by means of driven base tests in order to simulate the dynamic loads during launch. This method is limited to structures which fit onto the shaker facility. For large and unwieldy structures an alternative approach can be utilized which applies modal forces for the qualification. This testing concept is called Modal Force Combination (MFC) technique and replaces the base acceleration by a set of forces acting directly in a selected number of structural points. Modal forces are patterns of single forces that are able to excite single resonances and which can be applied by movable electrodynamic shakers. An advanced test strategy for the MFC technique is presented in this article. The strategy applies narrow-banded swept sine excitation and considers structural non-linearities. In extension to MFC technique introduced up to now, a non-linear model which is identified from the narrow-banded swept sine runs on a low or intermediate level is used for the redefinition of the transients which are needed to achieve the next excitation level and finally the qualification of the structure. Since within the strategy single modes are used for the qualification the method is called boosted modal survey test on the flight model of the European Robotic Arm (ERA) are used to demonstrate the suitability of the concept. The pros and cons of the approach are discussed, recommendations concerning the application are given and the limitations are point out

Non-linear phenomena in ground vibration testing of large aircraft

Ground vibration tests (GVTs) on aircraft prototypes are mainly performed to identify experimentally the structural dynamic behaviour in terms of a modal model. This assumes linear dynamic behaviour of the structure. However, it is often observed in practice of ground vibration testing that structures do not behave in a perfectly linear manner. Non-linearities can be determined for example by free play junctions, hydraulic systems in control surfaces, or friction. The paper compiles measured typical non-linear phenomena from various GVTs on large aircraft. The standard procedure in GVTs is nowadays the application of the Harmonic Balance method which linearizes the dynamic behaviour in the level of excitation resulting in the dependendcy of modal parameters on the excitation level. This makes the experimental data compatible to all procedures of post-processing of the measured results, e.g. updating of the finite element model or flutter calculations. The procedure of the Harmonic Balance requires the harmonic excitation of the structure which is usually performed during phase resonance testing. The non-linear behaviour is investigated in terms of linearity plots in which the eigenfrequency of a mode is plotted as a function of the excitation level. This level can be measured by various means. Common measures are the amplitude of the structure at a selected point, in most cases the maximum displacement, and the input force. The paper shows measured linearity plots for some typical non-linear phenomena. The second part of the paper analytical linearity plots are investigated in order to characterise and identify the type of non-linearity from measured linearity plots. The analytical linearity plots are created using a single-degree-of-freedom (SDOF)system with different models of non-linearities. The analytical linearity plots are discussed and an assessment of the linearity plots with respect to the application boundaries is given. The analytical linearity plots are used to interpret the experimental linearity plots stemming from various GVTs on different aircraft prototypes. The observability of non-linear stiffness and non-linear damping characteristics is finally assessed

Non-linear phenomena in ground vibration testing of large aircraft

Ground vibration tests (GVTs) on aircraft prototypes are mainly performed to identify experimentally the structural dynamic behaviour in terms of a modal model. This assumes linear dynamic behaviour of the structure. However, it is often observed in practice of ground vibration testing that structures do not behave in a perfectly linear manner. Non-linearities can be determined for example by free play junctions, hydraulic systems in control surfaces, or friction. The paper compiles measured typical non-linear phenomena from various GVTs on large aircraft. The standard procedure in GVTs is nowadays the application of the Harmonic Balance method which linearizes the dynamic behaviour in the level of excitation resulting in the dependendcy of modal parameters on the excitation level. This makes the experimental data compatible to all procedures of post-processing of the measured results, e.g. updating of the finite element model or flutter calculations. The procedure of the Harmonic Balance requires the harmonic excitation of the structure which is usually performed during phase resonance testing. The non-linear behaviour is investigated in terms of linearity plots in which the eigenfrequency of a mode is plotted as a function of the excitation level. This level can be measured by various means. Common measures are the amplitude of the structure at a selected point, in most cases the maximum displacement, and the input force. The paper shows measured linearity plots for some typical non-linear phenomena. The second part of the paper analytical linearity plots are investigated in order to characterise and identify the type of non-linearity from measured linearity plots. The analytical linearity plots are created using a single-degree-of-freedom (SDOF)system with different models of non-linearities. The analytical linearity plots are discussed and an assessment of the linearity plots with respect to the application boundaries is given. The analytical linearity plots are used to interpret the experimental linearity plots stemming from various GVTs on different aircraft prototypes. The observability of non-linear stiffness and non-linear damping characteristics is finally assessed