Giant suppression of the Drude conductivity due to quantum interference in disordered two-dimensional systems

Temperature and magnetic field dependences of the conductivity in heavily doped, strongly disordered two-dimensional quantum well structures GaAs/In$_x$Ga$_{1-x}$As/GaAs are investigated within wide conductivity and temperature ranges. Role of the interference in the electron transport is studied in the regimes when the phase breaking length $L_\phi$ crosses over the localization length $\xi\sim l\exp{(\pi k_Fl/2)}$ with lowering temperature, where $k_F$ and $l$ are the Fermi quasimomentum and mean free path, respectively. It has been shown that all the experimental data can be understood within framework of simple model of the conductivity over delocalized states. This model differs from the conventional model of the weak localization developed for $k_Fl\gg 1$ and $L_\phi\ll\xi$ by one point: the value of the quantum interference contribution to the conductivity is restricted not only by the phase breaking length $L_\phi$ but by the localization length $\xi$ as well. We show that just the quantity $(\tau_\phi^\ast)^{-1}=\tau_\phi^{-1}+\tau_\xi^{-1}$ rather than $\tau_\phi^{-1}$, where $\tau_\phi\propto T^{-1}$ is the dephasing time and $\tau_\xi\sim\tau\exp(\pi k_F l)$, is responsible for the temperature and magnetic field dependences of the conductivity over the wide range of temperature and disorder strength down to the conductivity of order $10^{-2} e^2/h$.Comment: 11 pages, 15 figure

Samen werken aan samenwerking

Op het gebied van horizontale samenwerking is er veel mogelijk qua vorm, intensiteit, werkterrein en juridische constructie, zowel in de agrosector als in het mkb. De vele mogelijkheden bieden veel aangrijpingspunten om privé- en bedrijfsdoelen beter te kunnen bereiken, onder andere door meer denk- en slagkracht, ook financieel, en sociale voordelen als steun en meer vrije tijd. Samenwerking vraagt echter ook veel van de ondernemers en hun competenties. In dit onderzoek is vooral gekeken naar horizontale samenwerking: tussen soortgelijke ondernemers onderlin

Localized energy for wave equations with degenerate trapping

Localized energy estimates have become a fundamental tool when studying wave equations in the presence of asymptotically at background geometry. Trapped rays necessitate a loss when compared to the estimate on Minkowski space. A loss of regularity is a common way to incorporate such. When trapping is sufficiently weak, a logarithmic loss of regularity suffices. Here, by studying a warped product manifold introduced by Christianson and Wunsch, we encounter the first explicit example of a situation where an estimate with an algebraic loss of regularity exists and this loss is sharp. Due to the global-in-time nature of the estimate for the wave equation, the situation is more complicated than for the Schr\"{o}dinger equation. An initial estimate with sub-optimal loss is first obtained, where extra care is required due to the low frequency contributions. An improved estimate is then established using energy functionals that are inspired by WKB analysis. Finally, it is shown that the loss cannot be improved by any power by saturating the estimate with a quasimode.Comment: 18 page

The syncytial Drosophila embryo as a mechanically excitable medium

Mitosis in the early syncytial Drosophila embryo is highly correlated in space and time, as manifested in mitotic wavefronts that propagate across the embryo. In this paper we investigate the idea that the embryo can be considered a mechanically-excitable medium, and that mitotic wavefronts can be understood as nonlinear wavefronts that propagate through this medium. We study the wavefronts via both image analysis of confocal microscopy videos and theoretical models. We find that the mitotic waves travel across the embryo at a well-defined speed that decreases with replication cycle. We find two markers of the wavefront in each cycle, corresponding to the onsets of metaphase and anaphase. Each of these onsets is followed by displacements of the nuclei that obey the same wavefront pattern. To understand the mitotic wavefronts theoretically we analyze wavefront propagation in excitable media. We study two classes of models, one with biochemical signaling and one with mechanical signaling. We find that the dependence of wavefront speed on cycle number is most naturally explained by mechanical signaling, and that the entire process suggests a scenario in which biochemical and mechanical signaling are coupled

Prioritising nurses' and doctors' health at work:a scoping review of monitoring instruments

OBJECTIVE: Nurses' and doctors' health at work is crucial for their overall performance and the quality of care they provide. The Jobs Demands Resources (JD-R) model offers a framework for health at work, encompassing 'job demands', 'job resources', 'personal resources', 'leadership', 'well-being' and 'outcomes'. While various instruments exist to measure health, an overview of instruments specifically designed for assessing nurses and doctors health is currently missing. This study provides a comprehensive overview of available health instruments specifically developed and validated for healthcare professionals in hospital care. DESIGN: Scoping review. DATA SOURCES: MEDLINE, Embase and CINAHL. ELIGIBILITY CRITERIA: Studies assessing the health of nurses and/or doctors in hospitals using or evaluating instruments based on the JD-R model, published between January 2011 and January 2024, excluding student-exclusive samples. DATA EXTRACTION AND SYNTHESIS: We extracted data on study and sample characteristics, as well as details of the measurement instruments, including main and subconstructs. Instruments were categorised based on the JD-R model domains. Descriptive analysis and data visualisation were performed using Excel and Python. RESULTS: We included 1204 studies, reporting 986 unique instruments. We identified 32 comprehensive instruments suitable for broad health screening, measuring four or more of the JD-R model domains. Additionally, we identified instruments focusing on specific domains for targeted screening needs. Furthermore, we present frequently reported instruments assumed to be extensively evaluated, user-friendly, accessible and available in multiple languages. CONCLUSIONS: Health at work cannot be determined by a single instrument alone, underscoring the multidimensional nature of workplace health. Alternatively, organisations should select instruments based on domains most relevant and applicable to their context. This approach ensures a more comprehensive assessment of health at work.</p

Increased expression of matrix metalloproteinase 3 can be attenuated by inhibition of microRNA-155 in cultured human astrocytes

Background: Temporal lobe epilepsy (TLE) is a chronic neurological disease, in which about 30% of patients cannot be treated adequately with anti-epileptic drugs. Brain inflammation and remodeling of the extracellular matrix (ECM) seem to play a major role in TLE. Matrix metalloproteinases (MMPs) are proteolytic enzymes largely responsible for the remodeling of the ECM. The inhibition of MMPs has been suggested as a novel therapy for epilepsy; however, available MMP inhibitors lack specificity and cause serious side effects. We studied whether MMPs could be modulated via microRNAs (miRNAs). Several miRNAs mediate inflammatory responses in the brain, which are known to control MMP expression. The aim of this study was to investigate whether an increased expression of MMPs after interleukin-1β (IL-1β) stimulation can be attenuated by inhibition of the inflammation-associated miR-155.Methods: We investigated the expression of MMP2, MMP3, MMP9, and MMP14 in cultured human fetal astrocytes after stimulation with the pro-inflammatory cytokine IL-1β. The cells were transfected with miR-155 antagomiR, and the effect on MMP3 expression was investigated using real-time quantitative PCR and Western blotting. Furthermore, we characterized MMP3 and miR-155 expression in brain tissue of TLE patients with hippocampal sclerosis (TLE-HS) and during epileptogenesis in a rat TLE model.Results: Inhibition of miR-155 by the antagomiR attenuated MMP3 overexpression after IL-1β stimulation in astrocytes. Increased expression of MMP3 and miR-155 was also evident in the hippocampus of TLE-HS patients and throughout epileptogenesis in the rat TLE model.Conclusions: Our experiments showed that MMP3 is dynamically regulated by seizures as shown by increased expression in TLE tissue and during different phases of epileptogenesis in the rat TLE model. MMP3 can be induced by the pro-inflammatory cytokine IL-1β and is regulated by miR-155, suggesting a possible strategy to prevent epilepsy via reduction of inflammation

An Efficient UV-C Disinfection Approach and Biological Assessment Strategy for Microphones

Featured Application Disinfection of microphones by using UV-C to be applied in the entertainment industry to prevent infections as a consequence of microphone sharing between individuals. Hygiene is a basic necessity to prevent infections, and though it is regarded as vital in general, its importance has been stressed again during the pandemic. Microbes may spread through touch and aerosols and thereby find their way from host to host. Cleaning and disinfection of possibly contaminated surfaces prevents microbial spread, thus reducing potential illnesses. One item that is used by several people in a way that promotes close contact by touch and aerosol formation is the microphone. A microphone is a complex piece of equipment with respect to shape and various materials used to fabricate it and, hence, its disinfection is challenging. A new device has been developed to efficiently sterilize microphones by using UV-C and a biological assessment has been done to identify its efficacy and translatability. For this investigation, a contamination procedure was developed by using M13 bacteriophage as a model to illustrate the effectiveness of the disinfection. The susceptibility to UV-C irradiation of M13 in solution was compared to that of the PR8 H1N1 influenza virus, which has a similar UV-C susceptibility as SARS-CoV-2. It was found that 10 min of UV-C treatment reduced the percentage of infectious M13 by 99.3% based on whole microphone inoculation and disinfection. UV-C susceptibility of M13 and influenza in suspension were found to be very similar, indicating that the microphone sterilization method and device function are highly useful and broadly applicable