Inert strength measurement on silica soaked at 250°C in liquid water and water vapour

The effect of water soaking and heat-treatment in saturated water vapour at 250°C for 192 h on the strength of silica glass is studied. Bending strength meaurements in liquid nitrogen showed a clear increase of the inert strength for heat-treated specimens over that of the untreated material. The increase in strength is interpreted as the consequence of water diffusion into exposed surfaces of the test specimen, which results in swelling of the glass and shielding of cracks, present in the surface of the glass. Experimental results are compared with theoretical predictions

Breakdown of the few-level approximation in collective systems

The validity of the few-level approximation in dipole-dipole interacting collective systems is discussed. As example system, we study the archetype case of two dipole-dipole interacting atoms, each modelled by two complete sets of angular momentum multiplets. We establish the breakdown of the few-level approximation by first proving the intuitive result that the dipole-dipole induced energy shifts between collective two-atom states depend on the length of the vector connecting the atoms, but not on its orientation, if complete and degenerate multiplets are considered. A careful analysis of our findings reveals that the simplification of the atomic level scheme by artificially omitting Zeeman sublevels in a few-level approximation generally leads to incorrect predictions. We find that this breakdown can be traced back to the dipole-dipole coupling of transitions with orthogonal dipole moments. Our interpretation enables us to identify special geometries in which partial few-level approximations to two- or three-level systems are valid

Evaluation of crack-terminating angles in heat-treated silica DCDC-specimens

Cracks terminating at free surfaces are affected by local stresses in the surface region. Under residual compression, the crack front must retard and under residual tensile stresses advance, both compared with the crack contour in the absence of stresses. This effect can be used for an estimation of residual surface stresses in silica generated during the silica/water reaction and caused by volume swelling. A strong shielding stress intensity factor of about -2.5 MPa$\sqrt{m}$ was found for DCDC specimen heat-treated for 192h at 250°C in water. This result is a clear indication for compressive stresses developing in the water diffusion zone at the surface

Coherent control in a decoherence-free subspace of a collective multi-level system

Decoherence-free subspaces (DFS) in systems of dipole-dipole interacting multi-level atoms are investigated theoretically. It is shown that the collective state space of two dipole-dipole interacting four-level atoms contains a four-dimensional DFS. We describe a method that allows to populate the antisymmetric states of the DFS by means of a laser field, without the need of a field gradient between the two atoms. We identify these antisymmetric states as long-lived entangled states. Further, we show that any single-qubit operation between two states of the DFS can be induced by means of a microwave field. Typical operation times of these qubit rotations can be significantly shorter than for a nuclear spin system.Comment: 15 pages, 11 figure

An ultra-sensitive pulsed balanced homodyne detector: Application to time-domain quantum measurements

A pulsed balanced homodyne detector has been developed for precise measurements of electric field quadratures of pulsed optical quantum states. A high level of common mode suppression (> 85 dB) and low electronic noise (730 electrons per pulse) provide a signal to noise ratio of 14 dB for the measurement of the quantum noise of individual pulses. Measurements at repetition rates up to 1 MHz are possible. As a test, quantum tomography of the coherent state is performed and the Wigner function and the density matrix are reconstructed with a 99.5% fidelity. The detection system can also be used for ultrasensitive balanced detection in cw mode, e.g. for weak absorption measurements.Comment: 3 pages, submitted to Optics Letter

Peeling back the layers of crassulacean acid metabolism: functional differentiation between Kalanchoë fedtschenkoi epidermis and mesophyll proteomes

Crassulacean acid metabolism (CAM) is a specialized mode of photosynthesis that offers the potential to engineer improved water‐use efficiency (WUE) and drought resilience in C3 plants while sustaining productivity in the hotter and drier climates that are predicted for much of the world. CAM species show an inverted pattern of stomatal opening and closing across the diel cycle, which conserves water and provides a means of maintaining growth in hot, water‐limited environments. Recent genome sequencing of the constitutive model CAM species Kalanchoë fedtschenkoi provides a platform for elucidating the ensemble of proteins that link photosynthetic metabolism with stomatal movement, and that protect CAM plants from harsh environmental conditions. We describe a large‐scale proteomics analysis to characterize and compare proteins, as well as diel changes in their abundance in guard cell‐enriched epidermis and mesophyll cells from leaves of K. fedtschenkoi. Proteins implicated in processes that encompass respiration, the transport of water and CO2, stomatal regulation, and CAM biochemistry are highlighted and discussed. Diel rescheduling of guard cell starch turnover in K. fedtschenkoi compared with that observed in Arabidopsis is reported and tissue‐specific localization in the epidermis and mesophyll of isozymes implicated in starch and malate turnover are discussed in line with the contrasting roles for these metabolites within the CAM mesophyll and stomatal complex. These data reveal the proteins and the biological processes enriched in each layer and provide key information for studies aiming to adapt plants to hot and dry environments by modifying leaf physiology for improved plant sustainability

Social Welfare and Collective Goods Coercion in Public Economics

This paper develops an expanded framework for social planning in which coercion stemming from the provision of public goods is explicitly acknowledged. Key issues concern the precise definition of coercion, its difference from redistribution, and its incorporation into social welfare optimization. The paper examines the implications for optimal policy, showing how the Samuelson condition, rules for optimal linear income taxation and commodity taxation, and for the marginal cost of public funds must be modified. In addition, the trade-off between social welfare and coercion is mapped under specific conditions and the implications of this trade-off for normative policy choice are considered

Cryogenic platform for coupling color centers in diamond membranes to a fiber-based microcavity

We operate a fiber-based cavity with an inserted diamond membrane containing ensembles of silicon vacancy centers (SiV−) at cryogenic temperatures ≥4 K. The setup, sample fabrication and spectroscopic characterization are described, together with a demonstration of the cavity influence by the Purcell effect. This paves the way towards solid-state qubits coupled to optical interfaces as long-lived quantum memories

Spatial-temporally resolved high-frequency surface acoustic waves on silicon investigated by femtosecond spectroscopy

Various types of surface acoustic waves are generated by femtosecond pulses on bulk silicon with aluminium stripe transducers. Rayleigh and leaky longitudinal surface acoustic wave modes are detected in the time domain for various propagation distances. The modes are identified by measuring on various pitches and comparing the spectra with finite element calculations. The lifetimes of the modes are determined quantitatively by spatially separating pump and probe beam, showing a significant difference in the lifetimes of both modes. We were able to excite and measure Rayleigh modes with frequencies of up to 90 GHz using a 100 nm period grating.Fil: Schubert, Martin . University of Konstanz. Department of Physics and Center for Applied Photonics; AlemaniaFil: Grossmann, Martin . University of Konstanz. Department of Physics and Center for Applied Photonics; AlemaniaFil: Ristow, Oliver . University of Konstanz. Department of Physics and Center for Applied Photonics; AlemaniaFil: Hettich, Mike . University of Konstanz. Department of Physics and Center for Applied Photonics; AlemaniaFil: Bruchhausen, Axel Emerico. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Energía Nuclear. Instituto Balseiro; ArgentinaFil: Barretto, Elaine C. S. . University of Konstanz. Department of Physics and Center for Applied Photonics; AlemaniaFil: Scheer, Elke . University of Konstanz. Department of Physics and Center for Applied Photonics; AlemaniaFil: Gusev, Vitalyi . Université du Maine; Francia. Centre National de la Recherche Scientifique; FranciaFil: Dekorsy, Thomas . University of Konstanz. Department of Physics and Center for Applied Photonics; Alemani

The burdens of poverty during the COVID-19 pandemic

Background: Individuals living at-risk-of-poverty have an increased risk of poor mental health. The pandemic and its societal impacts might have negative effects especially on this group widening the gap between rich and poor and also exacerbate gender gaps, which in turn might impact social cohesion. Aim: The objective of this longitudinal study was to determine if people living at-risk-of-poverty were more vulnerable to economic and psychosocial impacts of the pandemic and showed poorer mental health. Moreover, gender differences were analyzed. Method: We drew data from a sample of N = 10,250 respondents of two time points (T1 starting from October 2020, T2 starting from March 2021) of the Gutenberg COVID-19 Study. We tested for differences between people living at-risk-of-poverty and more affluent respondents regarding economic impacts, psychosocial stressors, as well as depressiveness, anxiety and loneliness, by comparing mean and distributional differences. To test for significant discrepancy, we opted for chi-square- and t-tests. Results: The analysis sample compromised N = 8,100 individuals of which 4,2% could be classified as living at-risk-of-poverty. 23% of respondents living at-risk-of-poverty had a decrease in income since the beginning of the pandemic–twice as many as those not living at-risk-of-poverty, who reported more often an increase in income. Less affluent individuals reported a decrease in working hours, while more affluent people reported an increase. Between our survey time points, we found a significant decrease in these economic impacts. Gender differences for economic changes were only found for more affluent women who worked more hours with no change in income. Less affluent respondents were more impacted by psychosocial stressors, depressiveness, anxiety, and loneliness. Gender differences were found particularly with regard to care responsibilities. Discussion: Our results indicate a widening in the gap between the rich and the poor at the beginning of the pandemic. Gender differences concerning economic changes affect more affluent women, but women in both income groups are more burdened by care responsibilities, which might indicate a heightened resurgence of gender role in times of crisis. This increase in inequality might have impacted social cohesion