Phase separation in carbon:transition metal nanocomposite thin films

The structural evolution of carbon:transition metal (C:TM) nanocomposite thin films is investigated in two regimes: (i) surface diffusion governed regime occurring during the film growth and (ii) bulk diffusion dominated regime occurring during the post-deposition thermal annealing. C:V, C:Co, and C:Cu nanocomposite films were grown by ion beam co-sputtering. The influence of the metal type, metal content (15-40 at.%), substrate temperature (RT-500°C), and annealing temperature (300-700°C) on the structure and morphology of the composite is studied by the means of elastic recoil detection analysis, X-ray diffraction, transmission electron microscopy, and Raman spectroscopy. Vanadium (copper) is in carbidic (metallic) state in the whole temperature range of the study. In contrast, cobalt is in carbidic state up to 300°C and becomes metallic at higher growth temperatures. The nanoparticles in C:V films exhibit a globular shape at RT-500°C, whereas in C:Co and C:Cu films a growth transition from globular to elongated nanoparticles occurs around 300°C. The comparison of the Raman spectroscopy results from carbon reference and C:TM thin films shows that the presence of the metal during growth significantly enhances the formation of sixfold ring carbon clusters at temperatures as low as RT. The enhancement occurs independently of the nanoparticle size, shape, and phase, and metal content, and is related to processes taking place on the nanoparticle surface of the growing film rather than in the bulk. The degree of enhancement depends on the TM type and content. Post-deposition annealing of C:Co and C:Cu films at 700°C causes the metal segregation at the film surface, while no changes upon annealing occur in C:V films. In addition, cobalt brings about the carbon graphitization by a dissolution-diffusion-precipitation mechanism, similar to the metal-mediated crystallization of amorphous silicon or germanium. No graphitization upon annealing occurs in C:V, C:Cu, and carbon reference films.Die Strukturentwicklung in Kohlenstoff-Übergangsmetall-Nanokompositschichten wird in zwei Bereichen untersucht: (i) im oberflächendiffusionsgesteuerten Bereich während des Schichtwachstums und (ii) im bulkdiffusionsdominierten Bereich während des nachträglichen Temperns. C:V, C:Co und C:Cu Nanokompositschichten wurden durch Ionenstrahl Co-Sputtern hergestellt. Der Einfluss des Metalltyps, des Metallgehalts (15-40 at.%), der Substrattemperatur (RT-500°C) und der Temperatur beim Tempern (300-700°C) auf die Struktur und Morphologie des Komposits wird mittels elastischer Rückstoßteilchen-Analyse, Röntgenbeugung, Transmissionselektronenmikroskopie und Ramanspektroskopie untersucht. Vanadium (Kupfer) ist im gesamten Temperaturbereich der Studie in karbidischem (metallischen) Zustand. Im Gegensatz dazu befindet sich Kobalt bis zu einer Temperatur von 300°C in karbidischem Zustand und wird bei höheren Abscheidetemperaturen metallisch. Die Nanopartikel in C:V Filmen besitzen eine runde Form im Temperaturbereich von RT bis 500°C wohingegen bei den C:Co und C:Cu Filmen ein Übergang von runden zu länglichen Partikeln bei etwa 300°C zu beobachten ist. Der Vergleich der Ramanspektroskopieresultate der Kohlenstoffreferenzproben und der Nanokompositschichten zeigt, dass die Anwesenheit des Metalls während des Schichtwachstums die Bildung von sechsatomigen Kohlenstoffringclustern bei Temperaturen so niedrig wie Raumtemperatur deutlich fördert. Die Erhöhung tritt unabhängig von der Partikelgröße, -form und phase und unabhängig vom Metallgehalt auf, und betrifft eher Prozesse, die auf der Oberfläche der Nanopartikel während des Schichtwachstums stattfinden als im Bulk. Der Grad der Erhöhung hängt vom Metalltyp und -gehalt ab. Nachträgliches Tempern der C:Co und C:Cu Filme bei 700°C führt zur Segregation des Metalls an der Schichtoberfläche während in den C:V Filmen keine Veränderungen durch das Tempern auftreten. Des weiteren kommt es in den C:Co Filmen zur Graphitisierung des Kohlenstoffs durch einen „Lösungs-Diffusions-Ablagerungs“ Mechanismus ähnlich der metallvermittelten Kristallisierung in amorphem Silizium und Germanium. In den C:V, C:Cu und Kohlenstoffreferenzfilmen findet keine Graphitisierung während des Temperns statt

Risk diversification and tax competition: The influence of risk correlations and tax provisions on tax competition

From standard-portfolio-models the authors derive demand elasticities for risky assets, and combine the results with a simple non-cooperative model of tax competition between capital importing countries. They find that tax rates resulting from tax competition depend heavily on the correlations of capital market indices. If investment alternatives are not correlated, the outcome of both tax competition and a cooperative solution of tax harmonization are identical. The results suggest regional cooperation among capital importing countries. Compared to the exemption method provisions like tax sparing aggravates the harms of tax competition.Die Autoren leiten aus dem Standard-Portfolio-Modell Nachfrageelastizitäten nach riskanten Anlagealternativen her und bringen diese in ein einfaches nicht-kooperatives spieltheoretisches Modell zum Steuerwettbewerb zwischen kapitalimportierenden Ländern ein. Wie sich zeigt, hängen die vom Steuerwettbewerb hervorgebrachten Steuersätze stark von den Korrelationen der Marktindices ab. Sind diese nicht korreliert, bringt der Steuerwettbewerb das gleiche Ergebnis hervor wie die kooperative Lösung einer Steuerharmonisierung. Die Ergebnisse liefern ferner Argumente für die regionale Kooperation kapitalimportierender Länder. Zudem wird gezeigt, dass die fiktive Anrechnung ausländischer Quellensteuern den Steuerwettbewerb verschärft

Bundling as a strategy for a commodity service brand introduction. The impact of bundle partner image on quality and risk perception and the role of complementarity

Increasing the quality perception and reducing the perceived risk of purchase improves the chances of success for new service introductions. This research investigated whether, for a new service brand introduction into the German residential electricity market, bundling with a stronger service brand enhances the perceived quality and reduces the perceived risk more than bundling with a weaker brand. In the goods category, it has been scientifically shown prior to this research that bundling with a stronger brand achieves this effect if the products are complementary. An academic knowledge gap in this area existed because this enhancement effect was yet to be evaluated empirically for services. This research applied price bundling to a new electricity service brand introduction via a survey experiment with potential customers rating electricity bundle offers. The research design was a 2*2 (brand image of bundle partner; complementarity) factorial design with analysis of variance (ANOVA) to test the research hypotheses. The results narrow the knowledge gap and contribute to professional practice by establishing that bundling with a stronger brand enhances the perceived quality and reduces the perceived risk also for services. The research furthermore demonstrated that complementarity is, independent of the bundle partner brand image, a factor to improve quality perception and to reduce the perceived risk of a new service brand

Using natural language processing to support peer‐feedback in the age of artificial intelligence: a cross‐disciplinary framework and a research agenda

Advancements in artificial intelligence are rapidly increasing. The new-generation large language models, such as ChatGPT and GPT-4, bear the potential to transform educational approaches, such as peer-feedback. To investigate peer-feedback at the intersection of natural language processing (NLP) and educational research, this paper suggests a cross-disciplinary framework that aims to facilitate the development of NLP-based adaptive measures for supporting peer-feedback processes in digital learning environments. To conceptualize this process, we introduce a peer-feedback process model, which describes learners' activities and textual products. Further, we introduce a terminological and procedural scheme that facilitates systematically deriving measures to foster the peer-feedback process and how NLP may enhance the adaptivity of such learning support. Building on prior research on education and NLP, we apply this scheme to all learner activities of the peer-feedback process model to exemplify a range of NLP-based adaptive support measures. We also discuss the current challenges and suggest directions for future cross-disciplinary research on the effectiveness and other dimensions of NLP-based adaptive support for peer-feedback. Building on our suggested framework, future research and collaborations at the intersection of education and NLP can innovate peer-feedback in digital learning environments

Using natural language processing to support peer‐feedback in the age of artificial intelligence: A cross‐disciplinary framework and a research agenda

Advancements in artificial intelligence are rapidly increasing. The new-generation large language models, such as ChatGPT and GPT-4, bear the potential to transform educational approaches, such as peer-feedback. To investigate peer-feedback at the intersection of natural language processing (NLP) and educational research, this paper suggests a cross-disciplinary framework that aims to facilitate the development of NLP-based adaptive measures for supporting peer-feedback processes in digital learning environments. To conceptualize this process, we introduce a peer-feedback process model, which describes learners' activities and textual products. Further, we introduce a terminological and procedural scheme that facilitates systematically deriving measures to foster the peer-feedback process and how NLP may enhance the adaptivity of such learning support. Building on prior research on education and NLP, we apply this scheme to all learner activities of the peer-feedback process model to exemplify a range of NLP-based adaptive support measures. We also discuss the current challenges and suggest directions for future cross-disciplinary research on the effectiveness and other dimensions of NLP-based adaptive support for peer-feedback. Building on our suggested framework, future research and collaborations at the intersection of education and NLP can innovate peer-feedback in digital learning environments

Spinal radiosurgery - efficacy and safety after prior conventional radiotherapy

<p>Abstract</p> <p>Background</p> <p>Conventional external beam radiotherapy is a standard procedure for treatment of spinal metastases. In case of progression spinal cord tolerance limits further radiotherapy in pre-irradiated areas. Spinal stereotactic radiotherapy is a non-invasive option to re-treat pre-irradiated patients. Nevertheless, spinal radiosurgery results in relevant dose deposition within the myelon with potential toxicity. Aim of the study was to retrospectively analyse the efficacy and feasibility for salvage radiosurgery of spinal metastases.</p> <p>Methods</p> <p>During a period of 4 years (2005-2009) 70 lesions in 54 patients were treated in 60 radiosurgery sessions and retrospectively analysed. Clinical (pain, sensory and motor deficit) and radiological (CT/MRI) follow-up data were collected prospectively after radiosurgery. Pain - as main symptom - was classified by the Visual Analogue Scale (VAS) score. Every patient received single session radiosurgery after having been treated first-line with conventionally fractionated radiotherapy. Kaplan-Meier method and life tables were used to analyse freedom from local failure and overall survival.</p> <p>Results</p> <p>At a median follow-up of 14.5 months the actuarial rates of freedom from local failure at 6/12/18 months were 93%, 88% and 85%, respectively. The median radiosurgery dose was 1 × 18 Gy (range 10-28 Gy) to the median 70% isodose. The VAS score of patients with pain (median 6) dropped significantly (median 4, p = 0.002). In 6 out of 7 patients worse sensory or motor deficit after SRS was caused by local or distant failures (diagnosed by CT/MRI). One patient with metastatic renal cell carcinoma developed a progressive complete paraparesis one year after the last treatment at lumbar level L3. Due to multiple surgery and radiosurgery treatments at the lumbar region and further local progression, the exact reason remained unclear. Apart from that, no CTC grade III or higher toxicity has been observed.</p> <p>Conclusions</p> <p>By applying spinal radiosurgery relevant radiation doses can be limited to small parts of the myelon. This prevents myelopathic side effects and makes it an effective and safe treatment option for well-suited patients. Especially for previously irradiated patients with local failure or pain salvage SRS represents a valuable treatment option with high local control rates, low toxicity and significant pain reduction.</p

Potassium uptake in the unicellular cyanobacterium Synechocystis sp. strain PCC 6803 mainly depends on a Ktr-like system encoded by slr1509 (ntpJ)

AbstractThe molecular basis of potassium uptake in cyanobacteria has not been elucidated. However, genes known from other bacteria to encode potassium transporters can be identified in the genome of Synechocystis sp. strain PCC 6803. Mutants defective in kdpA and ntpJ were generated and characterized to address the role of the Kdp and KtrAB systems in this strain. KtrAB is crucial for K+ uptake, as the ΔntpJ mutant shows slowed growth, slowed potassium uptake kinetics, and increased salt sensitivity. The ΔkdpA mutant has the same phenotype as the wild type even at limiting potassium, but a ΔkdpAΔntpJ double mutant is not viable, indicating a role of Kdp for potassium uptake when the Ktr system is not functioning

Vacuum Polarization and the Electric Charge of the Positron

We show that higher-order vacuum polarization would contribute a measureable net charge to atoms, if the charges of electrons and positrons do not balance precisely. We obtain the limit $|Q_e+Q_{\bar e}| < 10^{-18} e$ for the sum of the charges of electron and positron. This also constitutes a new bound on certain violations of PCT invariance.Comment: 9 pages, 1 figure attached as PostScript file, DUKE-TH-92-38. Revised versio

Empirical Studies on Foster Care: Review and Assessment

This is a selected review and critique of twenty articles which investigate psychosocial characteristics of children in foster care. Each article represents an effort to describe the foster care population and/or to test hypotheses about issues in foster care. Articles were selected within the time frame of 1974 to 1989. Data are presented in summary tabular form. Discussion focuses upon behavioral characteristics and emotional/health problems of the children. A general methodological critique of research is provided. Policy recommendations incorporate those variables/factors most frequently studied and suggest direction for further research