Objective and subjective evaluations of the multi-channel auralization technique as applied to solo instruments

Auralizations are commonly used today by architectural acousticians as a tool to model acoustically sensitive spaces. This paper presents investigations employing an auralization methodology known as multi-channel auralizations, to determine the benefits of using an increasing number of channels in such auralizations. First an objective evaluation was conducted to examine how acoustic parameters, such as reverberation time, vary when using “quadrant” (one fourth of a spherical source) or “thirteenth” sources to create the binaural room impulse responses. Large differences in the values were found between the different sections of the sphere, on the order of several just noticeable differences. Two subjective studies were then pursued, first to determine if auralizations made with an increasing number of channels sound more realistic and have an increased perceived source size, using solo musical instruments of varying directivity indices as the sources. Overall, subjects perceived the auralizations made with an increasing number of channels as more realistic, whereas results for perceived source size are less clear. The second subjective study assessed the ease with which subjects could identify the source orientation from the auralizations as a function of number of channels. Results indicate that more channels made it easier for subjects to differentiate between source orientations.     

Millimeter and submillimeter wave spectroscopic investigations into the rotation-tunneling spectrum of gGg ethylene glycol, HOCH2CH2OH

The rotation-tunneling spectrum of the second most stable gGg^′ conformer of ethylene glycol (1,2-ethanediol) in its ground vibrational state has been studied in selected regions between 77 and 579 GHz. Compared to the study of the more stable aGg^′ conformer, a much larger frequency range was studied, resulting in a much extended frequency list covering similar quantum numbers, J?55 and K_a?19. While the input data were reproduced within experimental uncertainties up to moderately high values of J and K_a larger residuals remain at higher quantum numbers. The severe mixing of the states caused by the Coriolis interaction between the two tunneling substates is suggested to provide a considerable part of the explanation. In addition, a Coriolis interaction of the gGg^′ ground vibrational state with an excited state of the aGg^′ conformer may also contribute. Relative intensities of closely spaced lines have been investigated to determine the signs of the Coriolis constants between the two tunneling substates relative to the dipole moment components and to estimate the magnitudes of the dipole moment components and the energy difference between the gGg^′ and the aGg^′ conformers. Results of ab initio calculations on the total dipole moment and the vibrational spectrum were needed for these estimates. The current analysis is limited to transitions with quantum numbers J?40 and K_a?6 plus those having J?22 and K_a?17 which could be reproduced within experimental uncertainties. The results are aimed at aiding radioastronomers to search for gGg^′ ethylene glycol in comets and in interstellar space.     

Quantitative high-resolution on-line NMR spectroscopy in reaction and process monitoring

On-line nuclear magnetic resonance spectroscopy (on-line NMR) is a powerful technique for reaction and process monitoring. Different set-ups for direct coupling of reaction and separation equipment with on-line NMR spectroscopy are described. NMR spectroscopy can be used to obtain both qualitative and quantitative information from complex reacting multicomponent mixtures for equilibrium or reaction kinetic studies. Commercial NMR probes can be used at pressures up to 35 MPa and temperatures up to 400 K. Applications are presented for studies of equilibria and kinetics of complex formaldehyde-containing mixtures as well as homogeneously and heterogeneously catalyzed esterification kinetics. Direct coupling of a thin-film evaporator is described as an example for the benefits of on-line NMR spectroscopy in process monitoring.     

Detecting exposure-dependent changes of liver detoxification capacity of children in a formerly high-loaded industrial area with a 15N-labelled diagnostic tool

The effect of remediation activities in formerly high-loaded industrial areas is measured conventionally in terms of decreased toxic loads. It is more difficult to investigate the effect on physiological parameters of the people living there. A non-invasive 15N-based organ function test, the [15N]methacetin urine test, was adapted to environmental-medical purposes for the detection of small deviations from the norm-range hepatic detoxification capacity. Parallel to the measurement of region-specific external exposure (especially by tri- and tetrachloro ethylene) and of the corresponding internal load (urinary trichloro acetic acid), the hepatic mono oxygenation capacity was determined. The study cohort consisted of 35 kindergarten children who were 3.3+/-0.5 years old at the beginning of the study. They lived in a high-polluted industrial village (n = 23) and in a non-polluted control village close by (n = 12), respectively. Children living in the polluted area were exposed a 2.3 times higher load and showed detoxification capacities 6% lower than the children in the control area. Improvement of the environmental situation led to exposure data decreasing by 70%, which is also reflected in smaller internal load and improved liver detoxification of the children in the polluted area. Then, between loaded and control area the mean hepatic detoxification was no longer significantly different (0.6%). The study shows that chronic low-dose exposure can disturb a hepatic function and that thereafter the capacity is recovered quickly in children. The stable isotope-based test is suited to characterize a health effect of multicomponent exposure by bioeffect monitoring within the framework of screening and testing the remediation efficiency.     

Dynamically assisted Schwinger mechanism

We study electron-positron pair creation from the Dirac vacuum induced by a strong and slowly varying electric field (Schwinger effect) which is superimposed by a weak and rapidly changing electromagnetic field (dynamical pair creation). In the subcritical regime where both mechanisms separately are strongly suppressed, their combined impact yields a pair creation rate which is dramatically enhanced. Intuitively speaking, the strong electric field lowers the threshold for dynamical particle creation--or, alternatively, the fast electromagnetic field generates additional seeds for the Schwinger mechanism. These findings could be relevant for planned ultrahigh intensity lasers.     

Role of NMDA receptor subtypes in different forms of NMDA-dependent synaptic plasticity

Background  

The involvement of different NMDA receptor (NMDAR) subunits has been implicated in several forms of synaptic plasticity. However, it is still controversial to what extent the involvement is specific, and little is known about the role of NMDAR subunits in certain "non-conventional" forms of plasticity. In this study we used subunit-specific blockers to test the roles of NR2A- and NR2B-containing NMDARs in a type of chemical long-term depression (LTD) induced by brief bath application of the NMDAR agonist NMDA to hippocampal slices from 12–18 days old rats. For comparison, we also examined other forms of plasticity, including a "slow LTD" induced by 0.1 Hz stimulation under low Mg²⁺ conditions as well as long-term potentiation (LTP).     

Electron gas induced in SrTiO<Subscript>3</Subscript>

This mini-review is dedicated to the 85th birthday of Prof. L.V. Keldysh, from whom we have learned so much. In this paper, we study the potential and electron density depth profiles in surface accumulation layers in crystals with a large and nonlinear dielectric response such as SrTiO₃ (STO) in the cases of planar, spherical, and cylindrical geometries. The electron gas can be created by applying an induction D₀ to the STO surface. We describe the lattice dielectric response of STO using the Landau–Ginzburg free energy expansion and employ the Thomas–Fermi (TF) approximation for the electron gas. For the planar geometry, we arrive at the electron density profile n(x) ∝ (x + d)^–12/7, where d ∝ D₀^–12/7. We extend our results to overlapping electron gases in GTO/STO/GTO heterojunctions and electron gases created by spill-out from NSTO (heavily n-type doped STO) layers into STO. Generalization of our approach to a spherical donor cluster creating a big TF atom with electrons in STO brings us to the problem of supercharged nuclei. It is known that for an atom with a nuclear charge Ze where Z > 170, electrons collapse onto the nucleus, resulting in a net charge Zn < Z. Here, instead of relativistic physics, the collapse is caused by the nonlinear dielectric response. Electrons collapse into the charged spherical donor cluster with radius R when its total charge number Z exceeds the critical value Z_c ≈ R/a, where a is the lattice constant. The net charge eZ_n grows with Z until Z exceeds Z* ≈ (R/a)^9/7. After this point, the charge number of the compact core Z_n remains ≈ Z*, with the rest Z* electrons forming a sparse TF atom with it. We extend our studies of collapse to the case of long cylindrical clusters as well.     

Microswimmers – From Single Particle Motion to Collective Behavior

Locomotion of autonomous microswimmers is a fascinating field at the cutting edge of science. It combines the biophysics of self-propulsion via motor proteins, artificial propulsion mechanisms, swimming strategies at low Reynolds numbers, the hydrodynamic interaction of swimmers, and the collective motion and synchronisation of large numbers of agents. The articles of this Special Issue are based on the lecture notes of an international summer school, which was organized by the DFG Priority Programme 1726 “Microswimmers – From Single Particle Motion to Collective Behaviour” in the fall of 2015. The minireviews provide a broad overview of the field, covering both elementary and advanced material, as well as selected areas from current research.