Estimating the effects on the dose distribution through the Bragg Peak degradation of lung tissue in proton therapy of thoracic tumors

Particle therapy offers to be a promising therapeutic option for tumors in the lung like Non-small cell lung cancer (NSCLC). However, the irradiation of NSCLCs with protons or carbon ions poses different challenges. The movement of the tumor, the heart and the entire thorax through breathing and the heartbeat requires a motion mitigated radiation application. In addition, the microscopic structure of the lung tissue holds further uncertainties of the calculation of the optimized dose distribution. In clinical CTs, on which treatment planning and dose calculation is based, the micrometer-sized air-filled alveoli of the lungs are not fully resolved, but are mapped through a medium density. As each particle of the beam passes a slightly different composition of air and tissue which leads to a slightly different range of the particles, the Bragg peak is degraded when irradiating such a heterogeneous tissue as lung. If this degradation of the Bragg peak is not taken into account into treatment planning, it can potentially lead to an underdose in the target volume and thus to a loss in tumor control. Additionally, the degradation can also lead to a higher dose in the organs at risk and normal tissue, endangering the success of the therapy by a higher toxicity of the treatment. In this dissertation, the effects of the Bragg Peak degradation on the dose distribution are calculated and analyzed so that an assessment of the effects for the clinical routine is available. For this purpose, CT images are manipulated with the help of a density modulation function, which modulates the density of the macroscopic lung voxel to reproduce the microscopic effect. Thus, a direct comparison between the dose distributions with and without the degrading effect is possible. Various dependencies like the tumor size, position and shape are systematically examined and the results of the degradation on clinical plans are presented for five patients. Hence, the clinical relevance can be estimated and assessed. In addition, measurements are presented which show the introduced material property of the "modulation power" of lung tissue. On the basis of this data, the uncertainties of the presented calculation and analysis can be reduced and estimated better. In addition, a mathematical model is presented which allows to estimate the modulation power on the basis of a clinical CT histogram analysis. Together, the works presented offer a basis for the patient-specific translation of the Bragg peak degradation of lung tissue into the clinical treatment planning procedure

TECHNOLOGY CLUSTERS AMONG FINTECHS: EXPLORING THE SIGNALING OF TECHNOLOGY SCOPE AND THE ROLE OF REGULATION

Financial technology ventures (FinTechs) use the latest technologies and act in a highly regulated industry. Yet, the technological scope of FinTechs and how this scope affects funding from investors remains unclear. Accordingly, research calls to examine the influence of technologies on the funding amount of FinTechs, especially in the context of different levels of regulatory freedom. We answer these questions by conducting an explorative cluster and regression analysis of 1,821 FinTechs and find three dominant clusters of FinTechs: technology newcomers, selective adopters, and full technology applicators. Technology newcomers have the lowest adoption rate of new technologies while full technology applicators combine several new technologies. Based on signaling theory and generalized linear models, we find that clusters significantly differ regarding their funding amount. However, we find that higher regulatory freedom decreases the differences between these clusters regarding the funding

Pyrolysis/methylation of soil fulvic acids: benzenecarboxyllc acids revisited

4 páginas, 1 figura, 3 tablas, 20 referencias.Fulvic acid (FA) is, perhaps, the most complex fraction of soil humic substances due to its extremely variable composition depending on the nature of the environment (1) and the isolation method (2). Practically all available techniques and methods have been applied to FAs (3), in order to understand their chemical structure, but in spite of extensive studies, their nature is still a matter of debate. Chemical degradations have been widely used to characterize FAs in terms of structural units. However, they provide only partial information on the molecular constituents. For instance, acid hydrolysis reveals the presence of sugars and some phenols, while oxidations yield alkanes, fatty acids, phenolic acids, and benzenecarboxylic acids (4). Benzenecarboxylic acids were considered the building blocks of the humic molecule in the 19709, and on the basis of permanganate oxidations and other analyses, Schnitzer and Khan (4) proposed a model made up of phenolic and benzenecarboxylic acids held together by hydrogen bonds, which were suggested to account for a significant part of the FA structure.Peer reviewe

Lokale und nicht-lokale Modellierung und Simulation thermomechanischer Lokalisierung mit Schädigung für metallische Werkstoffe unter Hochgeschwindigkeitsbeanspruchungen

Hochgeschwindigkeitsbeanspruchungen metallischer Bauteile sind bei einer Vielzahl ingenieurtechnischer Anwendungsbereiche, beispielsweise bei Crash- oder Falltests, bei Umform- oder Spanprozessen mit hohen Belastungsgeschwindigkeiten oder bei Aufprallproblemen von Komponenten schnell rotierender Bauteile auf das umgebende Gehäuse, z. B. bei Flugzeugturbinen, relevant. Dabei treten in dem beanspruchten Bauteil typischerweise Zonen mit großen, lokalisierten Deformationen auf, die auf die Entfestigung des Werkstoffs durch die Entwicklung von Schädigung und durch die Temperaturerhöhung infolge plastischer Dissipation zurückzuführen sind. Die Ausbildung von Scherbändern stellt dabei eine typische Form der Deformationslokalisierung dar. Die kontinuumsmechanische Modellierung solcher Vorgänge erfordert im Allgemeinen die Berücksichtigung einer Vielzahl von Faktoren und Effekten, wie beispielsweise dehnratenabh ängiges Materialverhalten, mit adiabatischer Erhitzung einhergehende thermische Entfestigung, Reibung und Kontakt sowie Schädigung. Darüber hinaus sind die genannten Effekte in dem Rahmen der Theorie großer Deformationen zu betrachten. Dehnratenabhängige "lokale" Modelle resultieren dabei nicht zwangsläufig in einer physikalisch sinnvollen Scherbandabbildung, d. h. in einer endlichen Scherbandbreite. Die innere Länge, die eine Begrenzung des Lokalisierungsvolumens darstellt, strebt für verschiedene im Rahmen der Simulation von Hochgeschwindigkeitsbelastungen eingesetzte, nichtlinear dehnratenabhängige Modelle, wie z.B. Potenzgesetz-Modelle oder dem Modell nach JOHNSON & COOK, mit infolge von Entfestigung abnehmender Spannung sowie zunehmender plastischer Dehnrate sehr stark gegen null. Dadurch tritt ein Verlust der lokalisierungsbegrenzenden Wirkung dieser ratenabh ängigen Modelle ein, so dass insbesondere jedes, auf diesen Modellen aufbauende Finite-Element Verfahren eine pathologische Netzabhängigkeit der Ergebnisse aufweist. "Nicht-lokale" Gradientenmodelle der Plastizität sind dazu geeignet, die beschriebenen Nachteile zu vermeiden. Die innere Länge dieser Modelle weist eine im Vergleich zu lokalen Modellen deutlich reduzierte Abhängigkeit von dem vorherrschenden Spannungszustand sowie der plastischen Dehnrate auf und wird darüber hinaus wesentlich durch den Wert des nichtlokalen Modellparameters beeinflusst. Die Größenordnung der inneren Länge bleibt dabei selbst für kleine Werte dieses Parameters auch mit Einsetzen von Lokalisierungseffekten zunächst erhalten. Infolge der numerischen Umsetzung nicht-lokaler Modelle mittels der Methode der Finiten-Elemente zeigt sich, dass im Gegensatz zu den auf lokalen Modellen basierenden Verfahren das Volumen der Lokalisierungszone bei stetiger Netzverfeinerung gegen einen endlichen Wert konvergiert. Damit gelingt es durch die Verwendung nicht-lokaler Modelle, die Ausbildung endlicher Scherbanddicken diskretisierungsunabhängig zu simulieren und im Rahmen der Kontinuumsmechanik eine sinnvolle Lösung des zugrunde liegenden physikalischen Problems zu gewährleisten.High-speed loading of metals is encountered in several engineering applications, for example in crash and drop tests as well as in high-speed cutting or forming processes. Likewise, the impact of rapidly rotating structural components on their surrounding containment, encountered for instance in aircraft turbines, reveals significant, high loading velocities. Typically, this type of loading results in zones with highly localized deformation within the stressed component, as a consequence of softening according to damage evolution and heating due to plastic dissipation. In this context, the formation of shear-bands represents a typical form of thermomechanical localization. In general, the continuum mechanical description and modelling of such events involves a variety of processes and effects such as high strain-rates, hardening behaviour, thermal softening as a result of adiabatic heating, friction and contact as well as damage. Further, these effects need to be considered in the framework of large deformation theory. Rate-dependent "local" models do not generally result in a physical shear-band development, e.g., involving a finite, non-vanishing shear-band thickness. In general, the intrinsic length incorporated by the rate-dependency of the models acts as a localization limiter. However, for various nonlinearly rate-dependent models, such as power-law models or the model according to JOHNSON & COOK, which are frequently used for the simulation of high-speed loading applications, this intrinsic length tends to zero owing to both increasing strain-rates and stress-drop due to softening behaviour. Thus, a loss of the localization limiting property of these rate-dependent models is encountered, incorporating that each finite-element method based upon these models yields a pathological mesh-dependence of the results. "Non-local" gradient-plasticity models based on a corresponding extension of the rate-dependence of the material behaviour are appropriate to avoid these disadvantages. In contrast to local models, the intrinsic length of these non-local models reveals a significantly reduced dependence on both the prevailing stress state and the plastic strain-rate but is dominantly influenced by the non-local material parameter. According to the numerical simulation of localization phenomena using finite-element techniques, the domain of the localization zone does converge to a finite volume for subsequent mesh-refinement. Thus, using non-local models it is possible to simulate the development of finite shear-band widths and to ensure a physically reasonable solution of the governing problem within the framework of continuum mechanics

Collaborating with Generative AI: Exploring Algorithm Appreciation in Creative Writing

Generative AI (GenAI) has recently attracted a tremendous amount of public attention showcasing the transformational capacity that AI-based systems have on society. By generating creative outputs in multimodal formats like texts and images, GenAI is entering domains formerly seen exclusive to human ingenuity. This raises concerns about how working with AI-based systems will affect employees. Existing research on human-AI collaboration is focusing on objective decision-making settings. We contribute to the growing IS research stream that considers AI collaboration on creative tasks. In particular, we conduct an online experiment to see whether employees appreciate GenAI-generated creative texts and how personality traits affect this interaction. We find that getting input from GenAI rather than a colleague relates to fewer modifications performed to the draft. This relationship is moderated by conscientiousness suggesting that conscientious employees are less inclined to accept suggestions and hence may not gain as much from GenAI tools

Room-temperature exciton-polaritons with two-dimensional WS2

Two-dimensional transition metal dichalcogenides exhibit strong optical transitions with significant potential for optoelectronic devices. In particular they are suited for cavity quantum electrodynamics in which strong coupling leads to polariton formation as a root to realisation of inversionless lasing, polariton condensationand superfluidity. Demonstrations of such strongly correlated phenomena to date have often relied on cryogenic temperatures, high excitation densities and were frequently impaired by strong material disorder. At room-temperature, experiments approaching the strong coupling regime with transition metal dichalcogenides have been reported, but well resolved exciton-polaritons have yet to be achieved. Here we report a study of monolayer WS$_2$ coupled to an open Fabry-Perot cavity at room-temperature, in which polariton eigenstates are unambiguously displayed. In-situ tunability of the cavity length results in a maximal Rabi splitting of $\hbar \Omega_{\rm{Rabi}} = 70$ meV, exceeding the exciton linewidth. Our data are well described by a transfer matrix model appropriate for the large linewidth regime. This work provides a platform towards observing strongly correlated polariton phenomena in compact photonic devices for ambient temperature applications.Comment: 12 pages, 6 figure

Strong exciton-photon coupling with colloidal nanoplatelets in an open microcavity

Colloidal semiconductor nanoplatelets exhibit quantum size effects due to their thickness of only few monolayers, together with strong optical band-edge transitions facilitated by large lateral extensions. In this article we demonstrate room temperature strong coupling of the light and heavy hole exciton transitions of CdSe nanoplatelets with the photonic modes of an open planar microcavity. Vacuum Rabi splittings of $66 \pm 1$ meV and $58 \pm 1$ meV are observed for the heavy and light hole excitons respectively, together with a polariton-mediated hybridisation of both transitions. By measuring the concentration of platelets in the film we compute the transition dipole moment of a nanoplatelet exciton to be $\mu = (575 \pm 110)$ D. The large oscillator strength and fluorescence quantum yield of semiconductor nanoplatelets provide a perspective towards novel photonic devices, combining polaritonic and spinoptronic effects.Comment: 9 pages, 4 figure

The use of small helicopters for commercial thinning in steep, mountainous terrain

A great deal of research has taken place in an effort to find more economically efficient yarding systems for commercial thinnings. Almost all of this research has centered on tractors or small yarders with limited capabilities in terms of long yarding distances. The purpose of this study is to determine whether using helicopters can be an economical alternative for commercial thinning in steep, mountainous terrain. The study area consists of a second-growth stand of Douglas-fir and mixed true fir species. The stand was thinned using a Lama SA- 315B helicopter (external lifting capacity of 2500 lbs.) to yard a total of 383 mbf (800.5 cunits) over a period of 3 weeks. Average yarding distance was approximately 2500 feet and the average slope was 40%. The diameter of the trees removed averaged 15 inches and the average piece size was approximately 87 board feet (.182 cunits). Gross production data were kept by the project manager for the logging company. This information is used to compare costs actually experienced during the operation with costs that might have occurred had the stand been cable yarded. The stand had originally been planned for uphill cable yarding using intermediate supports. A Thunderbird TNY 50 yarder is used as the hypothetical comparison operation. A detailed time study was conducted and the results are used to evaluate the effects of turn weights and yarding distance on the helicopter operation. Regression equations were developed and used to predict hook time, haul time, and total turn time for specific conditions. A damage survey was conducted after yarding to assess the condition of the residual stand. Results of this survey are compared with the amount of damage predicted for a cable system using a regression formula developed by Caccavano (1982) The results of the study indicate that using the Lama helicopter can be an economically feasible alternative for commercial thinning. An average yarding cost per thousand board feet of $179.21 was estimated for the helicopter operation; the cablesystem would have cost an estimated$159.73 per mbf for yarding, with an additional $55.21 per mbf for necessary road and landing construction. The helicopter yarding resulted in no damage to the residual stand. An estiniated 44.6 sq. ft. of scar area per acre would have resulted had the stand been cable yarded

EFFECTS OF MECHANICALLY GENERATED SLASH PARTICLE SIZE ON PRESCRIBED FIRE BEHAVIOR AND SUBSEQUENT VEGETATION EFFECTS

Forest managers have begun to restore ecosystem structure and function in fire-prone ecosystems that have experienced fire exclusion, commodity based resource extraction, and extensive grazing during much of the 20th century. Mechanical thinning and prescribed burning are the primary tools for thinning dense stands and restoring pre-settlement forest structure, reducing the likelihood of devastating crown fires. Mechanical thinning can be costly when trees are nonmerchantable and prescribed burning can be risky unless fuel loadings are first reduced. Furthermore, stands that remain dense after commercial thinning can produce undesirable wildland fire- or even prescribed fire- effects on vegetation and soils. Land managers are interested in using mastication equipment (Fig. 1) for thinning nonmerchantable trees as a means of restoring structure and function to dry forest ecosystems. However, it is unknown how the addition of mechanically derived slash influences potential fire behavior and fire effects. The objectives of this project were to test the effectiveness of mastication effort (defined as time needed to break fuels into smaller pieces) to 1) thin dense stands of dry coniferous forest within historically frequent, low-severity fire regimes (Fig. 1) and 2) create surface fuel beds that produce prescribed fire behavior with positive effects on residual trees, understory vegetation, and soils. Specifically, we asked the following questions: (1) How does slash particle size and fuel bed depth affect fire intensity and severity? (2) How do different mastication efforts and subsequent prescribed fire affect overstory vegetation? (3) Does soil heating change from burning different types of masticated slash? and (4) What are the differences in production costs among levels of mastication effort