The Role of Bilayer Tilt Difference in Equilibrium Membrane Shapes

Lipid bilayer membranes below their main transition have two tilt order parameters, corresponding to the two monolayers. These two tilts may be strongly coupled to membrane shape but only weakly coupled to each other. We discuss some implications of this observation for rippled and saddle phases, bilayer tubules, and bicontinuous phases. Tilt difference introduces a length scale into the elastic theory of tilted fluid membranes. It can drive an instability of the flat phase; it also provides a simple mechanism for the spontaneous breaking of inversion symmetry seen in some recent experiments.Comment: Latex file; .ps available at http://dept.physics.upenn.edu/~nelson/saddle.p

Stages of Concern: Vorerfahrungen, Interessen und Einstellungen von Lehrkräften in Bezug auf Lehr-Lernplattform-gestütztem Unterricht in den Naturwissenschaften

The pandemic-related measures highlighted the value of digitalization as a major issue in the education sector. Digital teaching units on teaching-learning platforms can make a decisive contribution in this field. In this study, data collected in summer 2019 on the affective-cognitive processes of examinations of science education using digitally formatted units, implemented on teaching-learning platforms and the particular usage of teaching-learning platforms themselves are re-analysed (N = 83). The study relies on the Stages of Concern (SoC) as a standardized instrument. A cluster analysis helps to identify three specific SoC-profiles in terms of the specific approach to and handling with the digital teaching-learning platforms. Common to all these profiles is that they concentrate on the impact on teaching and the students’ activities. In addition, the analysis shows a traditional use of the platforms in school (subgroup, N = 44 for teachers with access to teaching-learning platforms in school). Furthermore, correlation analyses show that there is no correlation between the type of use and the SoC-Profiles, but there is a correlation between the frequency of use and the SoC-profilesDie pandemiebedingten Maßnahmen haben den Wert der Digitalisierung im Bildungssektor deutlich gemacht. Digitale Unterrichtseinheiten auf Lehr-Lernplattformen können dazu einen entscheidenden Beitrag leisten. In der hier vorgelegten Studie werden Daten aus dem Sommer 2019 zu der affektiv-kognitiven Auseinandersetzung von naturwissenschaftlichen Lehrkräften mit digitalen Unterrichtseinheiten auf Lehr-Lernplattformen sowie deren Nutzung und Fortbildungswünsche neu analysiert (N = 83). Die Erhebung der affektiv-kognitiven Auseinandersetzung erfolgte mit dem standardisierten Instrument Stages of Concern (SoC). Mithilfe einer Clusteranalyse werden drei spezifische SoC-Profile in Bezug auf den Einsatz digitaler Unterrichtseinheiten auf einer Lehr-Lernplattform identifiziert. Dabei wird deutlich, dass allen Profilen die Beschäftigung mit der Auswirkung auf den Unterricht und auf die Schülerinnen und Schüler gemein ist. Zudem wird gezeigt, dass der Einsatz von Lehr-Lernplattformen vor der Pandemie eher traditionell geprägt war (Subgruppe, N = 44 für Lehrkräfte mit Zugang in der Schule zu einer Lehr-Lernplattform). Zusammenhangsanalysen zeigen des Weiteren, dass zwischen der Nutzungsart und den SoC-Profilen kein Zusammenhang festzustellen ist, ein solcher aber zwischen der Nutzungshäufigkeit und den SoC-Profilen besteh

Ultra-bright and efficient single photon generation based on N-V centres in nanodiamonds on a solid immersion lens

Single photons are fundamental elements for quantum information technologies such as quantum cryptography, quantum information storage and optical quantum computing. Colour centres in diamond have proven to be stable single photon sources and thus essential components for reliable and integrated quantum information technology. A key requirement for such applications is a large photon flux and a high efficiency. Paying tribute to various attempts to maximise the single photon flux we show that collection efficiencies of photons from colour centres can be increased with a rather simple experimental setup. To do so we spin-coated nanodiamonds containing single nitrogen-vacancy colour centres on the flat surface of a ZrO2 solid immersion lens. We found stable single photon count rates of up to 853 kcts/s at saturation under continuous wave excitation while having excess to more than 100 defect centres with count rates from 400 kcts/s to 500 kcts/s. For a blinking defect centre we found count rates up to 2.4 Mcts/s for time intervals of several ten seconds. It seems to be a general feature that very high rates are accompanied by a blinking behaviour. The overall collection efficiency of our setup of up to 4.2% is the highest yet reported for N-V defect centres in diamond. Under pulsed excitation of a stable emitter of 10 MHz, 2.2% of all pulses caused a click on the detector adding to 221 kcts/s thus opening the way towards diamond based on-demand single photon sources for quantum applications

Disorder, inhomogeneity and spin dynamics in f-electron non-Fermi liquid systems

Muon spin rotation and relaxation ($\mu$SR) experiments have yielded evidence that structural disorder is an important factor in many f-electron-based non-Fermi-liquid (NFL) systems. Disorder-driven mechanisms for NFL behaviour are suggested by the observed broad and strongly temperature-dependent $\mu$SR (and NMR) linewidths in several NFL compounds and alloys. Local disorder-driven theories (Kondo disorder, Griffiths-McCoy singularity) are, however, not capable of describing the time-field scaling seen in muon spin relaxation experiments, which suggest cooperative and critical spin fluctuations rather than a distribution of local fluctuation rates. A strong empirical correlation is established between electronic disorder and slow spin fluctuations in NFL materialsComment: 24 pages, 15 figures, submitted to J. Phys.: Condens. Matte

Scale-Invariant Gravity: Geometrodynamics

We present a scale-invariant theory, conformal gravity, which closely resembles the geometrodynamical formulation of general relativity (GR). While previous attempts to create scale-invariant theories of gravity have been based on Weyl's idea of a compensating field, our direct approach dispenses with this and is built by extension of the method of best matching w.r.t scaling developed in the parallel particle dynamics paper by one of the authors. In spatially-compact GR, there is an infinity of degrees of freedom that describe the shape of 3-space which interact with a single volume degree of freedom. In conformal gravity, the shape degrees of freedom remain, but the volume is no longer a dynamical variable. Further theories and formulations related to GR and conformal gravity are presented. Conformal gravity is successfully coupled to scalars and the gauge fields of nature. It should describe the solar system observations as well as GR does, but its cosmology and quantization will be completely different.Comment: 33 pages. Published version (has very minor style changes due to changes in companion paper

Multicentric validation of proteomic biomarkers in urine specific for diabetic nephropathy

Background: Urine proteome analysis is rapidly emerging as a tool for diagnosis and prognosis in disease states. For diagnosis of diabetic nephropathy (DN), urinary proteome analysis was successfully applied in a pilot study. The validity of the previously established proteomic biomarkers with respect to the diagnostic and prognostic potential was assessed on a separate set of patients recruited at three different European centers. In this case-control study of 148 Caucasian patients with diabetes mellitus type 2 and duration >= 5 years, cases of DN were defined as albuminuria >300 mg/d and diabetic retinopathy (n = 66). Controls were matched for gender and diabetes duration (n = 82). Methodology/Principal Findings: Proteome analysis was performed blinded using high-resolution capillary electrophoresis coupled with mass spectrometry (CE-MS). Data were evaluated employing the previously developed model for DN. Upon unblinding, the model for DN showed 93.8% sensitivity and 91.4% specificity, with an AUC of 0.948 (95% CI 0.898-0.978). Of 65 previously identified peptides, 60 were significantly different between cases and controls of this study. In <10% of cases and controls classification by proteome analysis not entirely resulted in the expected clinical outcome. Analysis of patient's subsequent clinical course revealed later progression to DN in some of the false positive classified DN control patients. Conclusions: These data provide the first independent confirmation that profiling of the urinary proteome by CE-MS can adequately identify subjects with DN, supporting the generalizability of this approach. The data further establish urinary collagen fragments as biomarkers for diabetes-induced renal damage that may serve as earlier and more specific biomarkers than the currently used urinary albumin

Accretion of Planetary Material onto Host Stars

Accretion of planetary material onto host stars may occur throughout a star's life. Especially prone to accretion, extrasolar planets in short-period orbits, while relatively rare, constitute a significant fraction of the known population, and these planets are subject to dynamical and atmospheric influences that can drive significant mass loss. Theoretical models frame expectations regarding the rates and extent of this planetary accretion. For instance, tidal interactions between planets and stars may drive complete orbital decay during the main sequence. Many planets that survive their stars' main sequence lifetime will still be engulfed when the host stars become red giant stars. There is some observational evidence supporting these predictions, such as a dearth of close-in planets around fast stellar rotators, which is consistent with tidal spin-up and planet accretion. There remains no clear chemical evidence for pollution of the atmospheres of main sequence or red giant stars by planetary materials, but a wealth of evidence points to active accretion by white dwarfs. In this article, we review the current understanding of accretion of planetary material, from the pre- to the post-main sequence and beyond. The review begins with the astrophysical framework for that process and then considers accretion during various phases of a host star's life, during which the details of accretion vary, and the observational evidence for accretion during these phases.Comment: 18 pages, 5 figures (with some redacted), invited revie