Spin-orbital excitation continuum and anomalous electron-phonon interaction in the Mott insulator LaTiO3_3

Raman scattering experiments on stoichiometric, Mott-insulating LaTiO$_3$ over a wide range of excitation energies reveal a broad electronic continuum which is featureless in the paramagnetic state, but develops a gap of $\sim 800$ cm$^{-1}$ upon cooling below the N\'eel temperature $T_N = 146$ K. In the antiferromagnetic state, the spectral weight below the gap is transferred to well-defined spectral features due to spin and orbital excitations. Low-energy phonons exhibit pronounced Fano anomalies indicative of strong interaction with the electron system for $T > T_N$, but become sharp and symmetric for $T < T_N$. The electronic continuum and the marked renormalization of the phonon lifetime by the onset of magnetic order are highly unusual for Mott insulators and indicate liquid-like correlations between spins and orbitals.Comment: to appear in Phys. Rev. Let

Biomechanics of DNA structures visualized by 4D electron microscopy

We present a technique for in situ visualization of the biomechanics of DNA structural networks using 4D electron microscopy. Vibrational oscillations of the DNA structure are excited mechanically through a short burst of substrate vibrations triggered by a laser pulse. Subsequently, the motion is probed with electron pulses to observe the impulse response of the specimen in space and time. From the frequency and amplitude of the observed oscillations, we determine the normal modes and eigenfrequencies of the structures involved. Moreover, by selective “nano-cutting” at a given point in the network, it was possible to obtain Young’s modulus, and hence the stiffness, of the DNA filament at that position. This experimental approach enables nanoscale mechanics studies of macromolecules and should find applications in other domains of biological networks such as origamis

Spectroscopy of Cold, Biomolecular Ions:Instrumentation and Application

In recent years, spectroscopic investigations of cold, biomolecular ions have started to provide new, detailed information about the structures of biomolecules in the gas phase. The present work comprises three major parts that describe the development of instrumentation for the preparation and manipulation of cold ions as well as its application to the spectroscopic study of a protonated amino acid dimer. The first part describes the development of a tandem quadrupole mass spectrometer with a 22-pole ion trap, designed for the spectroscopic investigation of cold, biomolecular ions. Several new features improve the performance of the instrument in comparison with the previous generation of the setup. The instrument is characterized in detail, and a vibrational temperature of the ions of about 10 K is demonstrated. In the second part, a novel multipole ion trap time-of-flight mass spectrometer is described, a hybrid instrument that uses a planar multipole trap as the extraction region of a reflectron. Its development is originally motivated in the context of the first part of the present work, as a tool to obtain a time-of-flight spectrum of the ions stored in the 22-pole. However, it may offer advantages for a range of different applications. The evolution of the mechanical design and the electronics are described, as well as the different setups that were used to test the instrument. Aided by numerical simulations, the characterization experiments shed light onto several subtleties of the principle of operation. The third and last part describes the infrared (IR) and ultraviolet (UV) spectroscopic investigation of the protonated phenylalanine/serine dimer, using the instrument detailed in the first part. The isomer-specific IR spectra demonstrate that this small and apparently simple system is more complex than could have been anticipated from previous investigations of related systems. In particular, isotopic labeling experiments provide evidence for different protonation sites in different isomers. Using a UV-pump/IR-probe scheme, it is demonstrated how the lifetimes and the IR spectra of several excited state species can be obtained

Compliance with recommended immunizations in adolescents

Introduction: Little is known about the completeness and timely administration of recommended standard immunizations in Germany. The goal of this study was to determine compliance with official standard immunization recommendations in adolescents attending secondary schools in the city of Erlangen, Germany. Methods: Adolescents who were attending 5th grade (at approximately 11years of age), 8th grade (14years), or 10th and 11th grade (16-17years) classes at any of the 13 of 14 schools that had agreed to participate were eligible to be enrolled. Results: While coverage for the primary series of diphtheria, tetanus and poliomyelitis immunizations was satisfactory (98%), coverage for measles-mumps-rubella immunizations (dose 1: 89-96%; dose 2: 60-76%) and hepatitis B (doses 1-3: 61%) was suboptimal. Of note, 39% of students had not received any immunization against pertussis. Completion of immunization series generally was significantly delayed. Furthermore, rates for recommended booster doses in adolescence were disappointingly low with 21% for tetanus component vaccines and <10% for the fifth dose of pertussis. Conclusions: Significant immunization gaps for all recommended standard immunizations in adolescents were detected. This puts individuals at risk for serious vaccine-preventable diseases, contributes to suboptimal herd immunity in the population under study leaving the potential for future epidemics, and impedes national and international targets of disease reduction or eliminatio

Effects of test mode and medium on elementary school students’ test experience

The use of digital media in education can bring great benefits and its use in schooling is steadily increasing. Administrating paper- versus computer-based as well as fixed-item versus adaptive tests could create differences in test experience, which can threaten the comparability of test results. This study investigated how the pen-and-paper, computer-based, and computer-adaptive test formats of a standardized reading comprehension test affect test anxiety and motivation among German fourth-grade students. A within-class randomized field trial with 387 fourth graders (aged: 9–10 years; 46.3% female) was conducted. Repeated-measures analysis of covariance (ANCOVA) revealed no differences in state test anxiety between the test formats when controlling for trait test anxiety and pre-test state anxiety, but state reading motivation was initially higher when reading on a screen, controlling for trait reading motivation. However, this difference diminishes over the course of the test. Implications for using digital media in elementary school test situations are discussed

Skalierbare Videocodierung mittels Teilbandzerlegung

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High refractive index films of polymer nanocomposites

Solutions of PbS particles and gelatin were used for the preparation of nanocomposites by a spin-coating process. This allows for the preparation of nanocomposite films with controlled thickness, e.g., between 40 nm and 2 μm for a film containing 45 wt.% PbS. Surface roughness and film thickness were investigated by surface profilometry and scanning electron microscopy (SEM). The refractive index at 632.8 nm can be expressed by a linear function of the volume fraction of PbS in the range of 0 to 55 vol. % PbS. In this range, the refractive index increases from 1.5 to 2.5 with increasing PbS ratio and belongs, therefore, to the highest refractive indices known for polymeric composite material