Heating Based Model Analysis for Explosive Emission Intitiation at Metal Cathodes

This contribution presents a model analysis for the initiation of explosive emission; a phenomena that is observed at cathode surfaces under high current densities. Here, localized heating is quantitatively evaluated on ultrashort time scales as a potential mechanism that initiates explosive emission, based on a two-temperature, relaxation time model. Our calculations demonstrate a strong production of nonequilibrium phonons, ultimately leading to localized melting. Temperatures are predicted to reach the cathode melting point over nanosecond times within the first few monolayers of the protrusion. This result is in keeping with the temporal scales observed experimentally for the initiation of explosive emission

Doping dependence of spin and orbital correlations in layered manganites

We investigate the interplay between spin and orbital correlations in monolayer and bilayer manganites using an effective spin-orbital t-J model which treats explicitly the e_g orbital degrees of freedom coupled to classical t_{2g} spins. Using finite clusters with periodic boundary conditions, the orbital many-body problem is solved by exact diagonalization, either by optimizing spin configuration at zero temperature, or by using classical Monte-Carlo for the spin subsystem at finite temperature. In undoped two-dimensional clusters, a complementary behavior of orbital and spin correlations is found - the ferromagnetic spin order coexists with alternating orbital order, while the antiferromagnetic spin order, triggered by t_{2g} spin superexchange, coexists with ferro-orbital order. With finite crystal field term, we introduce a realistic model for La_{1-x}Sr_{1+x}MnO_4, describing a gradual change from predominantly out-of-plane 3z^2-r^2 to in-plane x^2-y^2 orbital occupation under increasing doping. The present electronic model is sufficient to explain the stability of the CE phase in monolayer manganites at doping x=0.5, and also yields the C-type antiferromagnetic phase found in Nd_{1-x}Sr_{1+x}MnO_4 at high doping. Also in bilayer manganites magnetic phases and the accompanying orbital order change with increasing doping. Here the model predicts C-AF and G-AF phases at high doping x>0.75, as found experimentally in La_{2-2x}Sr_{1+2x}Mn_2O_7.Comment: 23 pages, 21 figure

Treatment of Cardiac Fibrosis with Extracellular Vesicles: What Is Missing for Clinical Translation?

Heart failure is the leading cause of morbidity and mortality and currently affects more than 60 million people worldwide. A key feature in the pathogenesis of almost all forms of heart failure is cardiac fibrosis, which is characterized by excessive accumulation of extracellular matrix components in the heart. Although cardiac fibrosis is beneficial in the short term after acute myocardial injury to preserve the structural and functional integrity of the heart, persistent cardiac fibrosis contributes to pathological cardiac remodeling, leading to mechanical and electrical dysfunction of the heart. Despite its high prevalence, standard therapies specifically targeting cardiac fibrosis are not yet available. Cell-based approaches have been extensively studied as potential treatments for cardiac fibrosis, but several challenges have been identified during clinical translation. The observation that extracellular vesicles (EVs) derived from stem and progenitor cells exhibit some of the therapeutic effects of the parent cells has paved the way to overcome limitations associated with cell therapy. However, to make EV-based products a reality, standardized methods for EV production, isolation, characterization, and storage must be established, along with concrete evidence of their safety and efficacy in clinical trials. This article discusses EVs as novel therapeutics for cardiac fibrosis from a translational perspective

How Preussag became TUI : kissing too many toads can make you a toad

In the period 1997-2004, Preussag, a diversified German conglomerate of old economy businesses, changed itself into TUI, a company focused almost entirely on tourism and logistics. This paper analyzes how this strategy was executed and how it contributed to Preussag’s underperformance of the stock market. We collect 417 announcements of acquisitions, financial disclosures and other news and disentangle the impact of different parts of the company’s strategy. We find that only the divestitures created value, that the strategy to invest in tourism destroyed value, and that the acquisition premiums Preussag paid were mostly unjustified. Bad luck like the events of September 11, 2001 cannot account for the poor performance of the stock. Poor management resulted from poor governance, combining a state-owned bank as the largest shareholder, board interlocks, and insufficient managerial incentives. The case shows how divestiture programs increase the liquid resources available to management beyond free operating cash flows and casts doubt on the positive governance role of institutional blockholders

Quantitative Antibiotic Use in Hospitals: Comparison of Measurements, Literature Review, and Recommendations for a Standard of Reporting

Abstract : Background: : Reports on antibiotic use often lack complete definitions of the units of measurement, hampering the comparison of data between hospitals or hospital units. Patients and Methods: : To compare methods of measures of in-hospital antimicrobial use, we determined aggregate in-hospital consumption data at a tertiary care university hospital using variations of nominators and denominators. Means of defined daily doses (DDD) of individual antimicrobials per 100 bed-days and per 100 admissions at each hospital and intensive care unit (ICU) were calculated. Furthermore, a literature review was performed for benchmarking purposes. Results: : Antibiotic use in different hospital units ranged from 0.105 to 323.37 DDD/100 bed-days and from 4.23 to 6737.92 DDD/100 admissions, respectively. Including the day of discharge in the denominator ‘bed-days' underestimated antibiotic use in various hospital wards by up to 27.7 DDD/100 bed-days (26.0%). Equating ‘numbers of patients admitted to the hospital' and ‘numbers of admissions' on a hospital level resulted in a difference of 192.6 DDD/100 admissions (64%) because patients transferred between hospital units accounted for multiple admissions. Likewise, reporting antimicrobial (Anatomical Therapeutic Chemical [ATC] group ‘J') instead of antibiotic (ATC group ‘J01') use led to a difference of 16.5 DDD/100 bed-days (19.3%). The literature review revealed underreporting of complete definitions of antibiotic use measurements. Conclusions: : Data on in-hospital antimicrobial use vary widely not only due to different antibiotic policies at different institutions but also due to different methods of measures. Adherence to the standard of reporting the methods of measurement is warranted for benchmarking and promotion of rational antimicrobial us

Determining and modelling a complete time-temperature-transformation diagram for a Pt-based metallic glass former through combination of conventional and fast scanning calorimetry

State of the art fast differential scanning calorimetry (FDSC) is used to complement conventional differential scanning calorimetry (DSC) studies about the isothermal time-temperature-transformation (TTT) diagram of the bulk metallic glass forming liquid Pt42.5Cu27Ni9.5P21 to allow a comprehensive study of the crystallization kinetics of this system over a broad temperature range. FDSC and DSC data align well in the low-temperature region of the crystallization nose but show distinct discrepancies in the high-temperature region as the FDSC studies reveal faster crystallization times. The results are mathematically described and discussed based on the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. Thereby, either homogeneous or heterogeneous nucleation is assumed, depending on the respective experimental conditions in FDSC and DSC studies. With this approach, the complete TTT diagram can be modelled as superposition of two sequential JMAK fits

Photoemission spectra of many-polaron systems

The cross over from low to high carrier densities in a many-polaron system is studied in the framework of the one-dimensional spinless Holstein model, using unbiased numerical methods. Combining a novel quantum Monte Carlo approach and exact diagonalization, accurate results for the single-particle spectrum and the electronic kinetic energy on fairly large systems are obtained. A detailed investigation of the quality of the Monte Carlo data is presented. In the physically most important adiabatic intermediate electron-phonon coupling regime, for which no analytical results are available, we observe a dissociation of polarons with increasing band filling, leading to normal metallic behavior, while for parameters favoring small polarons, no such density-driven changes occur. The present work points towards the inadequacy of single-polaron theories for a number of polaronic materials such as the manganites.Comment: 15 pages, 13 figures; final version, accepted for publication in Phys. Rev.

Two-path self-interference in PTCDA active waveguides maps the dispersion and refraction of a single waveguide mode

Bound waveguide modes propagating along nanostructures are of high importance since they offer low-loss energy-/signal-transport for future integrated photonic circuits. Particularly, the dispersion relation of these modes is of fundamental interest for the understanding of light propagation in waveguides as well as of light-matter interactions. However, for a bound waveguide mode, it is experimentally very challenging to determine the dispersion relation. Here, we apply a two-path interference experiment on microstructured single-mode active organic waveguides that is able to directly visualize the dispersion of the waveguide mode in energy-momentum space. Furthermore, we are able to observe the refraction of this mode at a structure edge by detecting directional interference patterns in the back-focal plane