A general model of fluency effects in judgment and decision making

Processing or cognitive fluency is the experienced ease of ongoing mental processes. This experience infl uences a wide range of judgments and decisions. We present a general model for these fluency effects. Based on Brunswik’s lens-model, we conceptualize fluency as a meta-cognitive cue. For the cue to impact judgments, we propose three process steps: people must experience fluency; the experience must be attributed to a judgment-relevant source; and it must be interpreted within the judgment context. This interpretation is either based on available theories about the experience’s meaning or on the learned validity of the cue in the given context. With these steps the model explains most fl uency effects and allows for new and testable predictions

Optimization of spatiotemporally fractionated radiotherapy treatments with bounds on the achievable benefit

Spatiotemporal fractionation schemes, that is, treatments delivering different dose distributions in different fractions, may lower treatment side effects without compromising tumor control. This is achieved by hypofractionating parts of the tumor while delivering approximately uniformly fractionated doses to the healthy tissue. Optimization of such treatments is based on biologically effective dose (BED), which leads to computationally challenging nonconvex optimization problems. Current optimization methods yield only locally optimal plans, and it has been unclear whether these are close to the global optimum. We present an optimization model to compute rigorous bounds on the normal tissue BED reduction achievable by such plans. The approach is demonstrated on liver tumors, where the primary goal is to reduce mean liver BED without compromising other treatment objectives. First a uniformly fractionated reference plan is computed using convex optimization. Then a nonconvex quadratically constrained quadratic programming model is solved to local optimality to compute a spatiotemporally fractionated plan that minimizes mean liver BED subject to the constraints that the plan is no worse than the reference plan with respect to all other planning goals. Finally, we derive a convex relaxation of the second model in the form of a semidefinite programming problem, which provides a lower bound on the lowest achievable mean liver BED. The method is presented on 5 cases with distinct geometries. The computed spatiotemporal plans achieve 12-35% mean liver BED reduction over the reference plans, which corresponds to 79-97% of the gap between the reference mean liver BEDs and our lower bounds. This indicates that spatiotemporal treatments can achieve substantial reduction in normal tissue BED, and that local optimization provides plans that are close to realizing the maximum potential benefit

Studies on vegetation-, fire-, climate- and human history in the mid- to late Holocene - a contribution to protection and management of the forest-steppe-biome in the Mongolian Altai

In this thesis, several sedimentological archives from Altai Tavan Bogd National Park are studied to reconstruct the vegetation-, fire-, climate- and human history of the forest-steppe biome in the Mongolian Altai. The research is carried out to improve the understanding of the dynamics and variability of this sensitive ecosystem and its unique biodiversity. Previous palynological or palaeoecological work from the Mongolian Altai is sparse, yet important for an implementation of sustainable land use as well as protection and management of the species-rich vegetation in the Altai region. The main goals of this research are to reconstruct past vegetation and to investigate the role and extent of climate, fire and anthropogenic impact on environmental change. A multi-site approach of five environmental archives (lacustrine and peat) from different locations and elevations within the forest-steppe biome (below, within and above the forest belt) is applied to obtain as much information as possible. Multi-proxy analyses including palynological and sedimentological proxies (pollen, NPPs, charcoal, diatoms and XRF-scanning) were used on the radiocarbon dated sediment archives. During the mid- and the beginning of the late Holocene (4,300 to 1,000 (2,000) cal yr BP) the vegetation in the area was characterized by open coniferous forest and high-mountain steppe indicating rather warm and humid conditions. In the further course of the late Holocene, steppe communities expanded noticeably favoring a colder and more arid climate. During the last approx. 70 years an increase in tree and shrub vegetation indicates a warming climate and a higher availability of water due to permafrost and glacier degradation in the high mountains. Regarding the human history in the Mongolian Altai, the period from 2,000 to 1,000 cal yr BP represents a transition phase from hunters and gatherers to a nomadic herding lifestyle. Coprophilous fungi reconstructions show that grazing intensified around 1,000 cal yr BP, possibly also favoring the expansion of steppe. High-resolution data show that changes in human occupation due to political shifts and changing Mongolian settlements had an impact on the vegetation in the area, especially during Mongol Empire (744 to 582 cal yr BP). Regardless of specific settlement periods, short-term changes in climatic conditions favored shifts in grazing activities. In the Mongolian Altai, fires play a tangential role. However, at around 1,000 cal yr BP the fire frequency increased in accord with growing anthropogenic impact and climate aridity. An episode of low fire activity persists since around 150 cal yr BP. Major local variances occurred regarding the time frame and extent of steppe expansion and grazing activities in the soil archive within the forest belt and with respect to the fire frequency in the peat archive above the upper forest line. The applied multi-proxy approach highlights the value of the reconstruction of several independent proxies to examine various aspects of an ecosystem in the same archive, despite of that the interpretation of results is challenging. Additionally, the multi-site study offers the best possibility to distinguish between local environmental signals and regional trends

Looking Competent Does Not Appeal to All Voters Equally: The Role of Social Class and Politicians’ Facial Appearance for Voting Likelihood

Voters generally value competence in politicians. Four studies, all conducted in Germany, show that this is especially pronounced in people of higher compared with lower social class. The first study, with a representative sample (N1 = 2239), found that the reported importance of competence in politicians increased with increasing socioeconomic status (SES). This was mediated by self-perceived competence which was higher in participants of higher SES. In three further studies (two preregistered, N2a&2b = 396, N3 = 400) participants merely saw pictures of politicians’ faces. Perceived competence based on facial appearance increased the likelihood of voting for a politician. Again, this effect was stronger among participants of higher compared with lower SES. This moderation persisted after controlling for participants’ political orientation and politicians’ perceived warmth and dominance. We discuss implications for future research on the psychological underpinnings of social class as well as appearance effects in the political context

Technical note: Optimal allocation of limited proton therapy resources using model-based patient selection

PURPOSE We consider the following scenario: A radiotherapy clinic has a limited number of proton therapy slots available each day to treat cancer patients of a given tumor site. The clinic's goal is to minimize the expected number of complications in the cohort of all patients of that tumor site treated at the clinic, and thereby maximize the benefit of its limited proton resources. METHODS To address this problem, we extend the normal tissue complication probability (NTCP) model-based approach to proton therapy patient selection to the situation of limited resources at a given institution. We assume that, on each day, a newly diagnosed patient is scheduled for treatment at the clinic with some probability and with some benefit from protons over photons, which is drawn from a probability distribution. When a new patient is scheduled for treatment, a decision for protons or photons must be made, and a patient may wait only for a limited amount of time for a proton slot becoming available. The goal is to determine the thresholds for selecting a patient for proton therapy, which optimally balance the competing goals of making use of all available slots while not blocking slots with patients with low benefit. This problem can be formulated as a Markov decision process (MDP) and the optimal thresholds can be determined via a value-policy iteration method. RESULTS The optimal thresholds depend on the number of available proton slots, the average number of patients under treatment, and the distribution of values. In addition, the optimal thresholds depend on the current utilization of the facility. For example, if one proton slot is available and a second frees up shortly, the optimal threshold is lower compared to a situation where all but one slot remain blocked for longer. CONCLUSIONS MDP methodology can be used to augment current NTCP model-based patient selection methods to the situation that, on any given day, the number of proton slots is limited. The optimal threshold then depends on the current utilization of the proton facility. Although, the optimal policy yields only a small nominal benefit over a constant threshold, it is more robust against variations in patient load

Spatiotemporal fractionation schemes for stereotactic radiosurgery of multiple brain metastases

BACKGROUND Stereotactic radiosurgery (SRS) is an established treatment for patients with brain metastases (BMs). However, damage to the healthy brain may limit the tumor dose for patients with multiple lesions. PURPOSE In this study, we investigate the potential of spatiotemporal fractionation schemes to reduce the biological dose received by the healthy brain in SRS of multiple BMs, and also demonstrate a novel concept of spatiotemporal fractionation for polymetastatic cancer patients that faces less hurdles for clinical implementation. METHODS Spatiotemporal fractionation (STF) schemes aim at partial hypofractionation in the metastases along with more uniform fractionation in the healthy brain. This is achieved by delivering distinct dose distributions in different fractions, which are designed based on their cumulative biologically effective dose ( ) such that each fraction contributes with high doses to complementary parts of the target volume, while similar dose baths are delivered to the normal tissue. For patients with multiple brain metastases, a novel constrained approach to spatiotemporal fractionation (cSTF) is proposed, which is more robust against setup and biological uncertainties. The approach aims at irradiating entire metastases with possibly different doses, but spatially similar dose distributions in every fraction, where the optimal dose contribution of every fraction to each metastasis is determined using a new planning objective to be added to the BED-based treatment plan optimization problem. The benefits of spatiotemporal fractionation schemes are evaluated for three patients, each with >25 BMs. RESULTS For the same tumor BED$_{10}$ and the same brain volume exposed to high doses in all plans, the mean brain BED$_{2}$ can be reduced compared to uniformly fractionated plans by 9%-12% with the cSTF plans and by 13%-19% with the STF plans. In contrast to the STF plans, the cSTF plans avoid partial irradiation of the individual metastases and are less sensitive to misalignments of the fractional dose distributions when setup errors occur. CONCLUSION Spatiotemporal fractionation schemes represent an approach to lower the biological dose to the healthy brain in SRS-based treatments of multiple BMs. Although cSTF cannot achieve the full BED reduction of STF, it improves on uniform fractionation and is more robust against both setup errors and biological uncertainties related to partial tumor irradiation

Radiotherapy planning for glioblastoma based on a tumor growth model: Improving target volume delineation

Glioblastoma are known to infiltrate the brain parenchyma instead of forming a solid tumor mass with a defined boundary. Only the part of the tumor with high tumor cell density can be localized through imaging directly. In contrast, brain tissue infiltrated by tumor cells at low density appears normal on current imaging modalities. In clinical practice, a uniform margin is applied to account for microscopic spread of disease. The current treatment planning procedure can potentially be improved by accounting for the anisotropy of tumor growth: Anatomical barriers such as the falx cerebri represent boundaries for migrating tumor cells. In addition, tumor cells primarily spread in white matter and infiltrate gray matter at lower rate. We investigate the use of a phenomenological tumor growth model for treatment planning. The model is based on the Fisher-Kolmogorov equation, which formalizes these growth characteristics and estimates the spatial distribution of tumor cells in normal appearing regions of the brain. The target volume for radiotherapy planning can be defined as an isoline of the simulated tumor cell density. A retrospective study involving 10 glioblastoma patients has been performed. To illustrate the main findings of the study, a detailed case study is presented for a glioblastoma located close to the falx. In this situation, the falx represents a boundary for migrating tumor cells, whereas the corpus callosum provides a route for the tumor to spread to the contralateral hemisphere. We further discuss the sensitivity of the model with respect to the input parameters. Correct segmentation of the brain appears to be the most crucial model input. We conclude that the tumor growth model provides a method to account for anisotropic growth patterns of glioblastoma, and may therefore provide a tool to make target delineation more objective and automated