Showing papers by "Utrecht University published in 2023"

A Comprehensive Sampling Study on SARS-CoV-2 Contamination of Air and Surfaces in a Large Meat Processing Plant Experiencing COVID-19 Clusters in June 2020

Abstract: de Rooij, Myrna M.T. PhD1,∗; Sikkema, Reina S. PhD2; Bouwknegt, Martijn PhD3; de Geus, Yvette MSc1; Stanoeva, Kamelia R. PhD4,5; Nieuwenweg, Sigrid BSc1; van Dam, Adriana S.G. MSc6; Raben, Ceder MSc1; Dohmen, Wietske PhD1; Heederik, Dick PhD1; Reusken, Chantal PhD4; Meijer, Adam PhD4; Koopmans, Marion P.G. PhD2; Franz, Eelco PhD4; Smit, Lidwien A.M. PhD1 Author Information

Imbalanced ensemble learning in determining Parkinson’s disease using Keystroke dynamics

Abstract: The main objective of this study is to propose a Keystroke dynamics (KD) based Parkinson’s disease (PD) indicator using both fixed-text and free-text typing habits on conventional keyboards and homogeneous ensemble learning with several fully balanced bootstrapped training sets for more accurate and robust eHealth applications. Furthermore, this study addresses the six key hypotheses related to our main objective of understanding the risks in this screening process that were previously unknown but important for further improvement. For a predetermined window length, the Colin Bannard and neuroQWERTY MIT-CSXPD datasets were used to extract a series of key hold times and the time gaps between two consecutive presses and releases as a feature set. A wide range of statistical tools were employed to create a machine learning-ready feature arrangement for continuously generated patterns. A homogeneous ensemble learning approach was then developed using bootstrapping and under-sampling while retaining any rare samples. This model was validated using fifteen fixed-text and free-text inputs obtained from early-stage PD patients, De-novo PD patients, and healthy controls. In the leave-one-user-out cross-validation (LOUOCV) evaluation, the maximum observed area under curve (AUC) is 85.99% ± 0.41 for fixed-text input. However, for free-text inputs, AUC is 78.3% ± 0.86, with a sensitivity/specificity of 74.46%/82.13%. The AUC for detecting De-novo patients is 79.83% ± 1.26, which is somewhat lower than the AUC for determining the early stage of the disease, which is 83.81% ± 0.83. The proposed model is more robust, usable (covert way of data acquisition), fast, and has ease of integration into conventional desktops/laptops suitable for real-life eHealth that could help for better diagnosis, early detection in a home environment, future reference, and treatment or therapy management. However, the subject size, severity levels of the disease, typing duration, feature composition, error in typing, and machine learning (ML) method selection influence the performance of this model. Therefore, careful attention is necessary while designing PD indicators using the proposed approach.

Transdisciplinary entrustable professional activities

Abstract: Healthcare has become highly specialized. Specialists, in medicine as well as in nursing, determine much of the high quality of current health care. But healthcare has also become increasingly fragmented, with professionals trained in separate postgraduate silos, with boundaries often difficult to cross. While a century ago, generalists dominated patient care provision, now specialists prevail and risk becoming alienated from each other, losing the ability to adapt to neighboring professional domains. Current health care requires a flexible workforce, ready to serve in multiple contexts, as the COVID-19 crisis has shown.The new concept of transdisciplinary entrustable professional activities, EPAs applicable in more than one specialty, was recently conceived to enhance collaboration and transfer between educational programs in postgraduate nursing in the Netherlands.In this paper, we reflect on our experiences so far, and on practical and conceptual issues concerning transdisciplinary EPAs, such as: who should define, train, assess, and register transdisciplinary EPAs? How can different prior education prepare for similar EPAs? And how do transdisciplinary EPAs affect professional identity?We believe that transdisciplinary EPAs can contribute to creating more flexible curricula and hence to a more coherent, collaborative healthcare workforce, less determined by the boundaries of traditional specialties.

A note on Marchenko-linearised full waveform inversion for imaging

Abstract: SUMMARY Full waveform inversion and least-squares reverse time migration are the leading technologies for imaging with seismic waves. Both of them usually rely (in one way or another) on a single-scattering approximation, i.e. the Born approximation, to compute gradients and obtain an updated model. This approximation linearises the relation between modelled data and model by ignoring multiple scattering. We propose to use the Marchenko integral, an equation originating from inverse scattering theory, to obtain an alternative linear equation. Using the Marchenko method we can retrieve Green’s functions, including all orders of scattering, for virtual sources anywhere within the volume of interest – without prior knowledge of the high-wavelength model variations that induce scattering. Plugging these estimated Green’s functions into the Lippmann–Schwinger integral delivers a Marchenko-linearised relation between the full waveform data and the model. We present this new linearisation strategy and illustrate its advantages and disadvantages by comparing numerical results for different inversion kernels. Our new linearisation is exact, i.e. it does not exclude any orders of scattering, however, it relies on the quality of the Marchenko-derived Green’s functions. These Marchenko-based Green’s functions require an estimate of the first arrivals of the Green’s functions – commonly obtained by modelling in a background medium. Although these first arrival estimates strongly bias our results for inaccurate background models, we find the Marchenko-linearisation to deliver overall slightly better inverted models than the single-scattering approximation.

The Framework for Assessing Changes To Sea-level (FACTS) v1.0-rc: A platform for characterizing parametric and structural uncertainty in future global, relative, and extreme sea-level change

Abstract: Abstract. Future sea-level rise projections are characterized by both quantifiable uncertainty and unquantifiable, structural uncertainty. Thorough scientific assessment of sea-level rise projections requires analysis of both dimensions of uncertainty. Probabilistic sea-level rise projections evaluate the quantifiable dimension of uncertainty; comparison of alternative probabilistic methods provide an indication of structural uncertainty. Here we describe the Framework for Assessing Changes To Sea-level (FACTS), a modular platform for characterizing alternative probability distributions of global mean, regional, and extreme sea-level rise. We demonstrate its application by generating seven alternative probability distributions under multiple alternative emissions scenarios for both future global mean sea level and future relative and extreme sea level at New York City. These distributions, closely aligned with those presented in the Intergovernmental Panel on Climate Change Sixth Assessment Report, emphasize the role of the Antarctic and Greenland ice sheet as drivers of structural uncertainty in sea-level rise projections.

A systematic procedure for incorporating separable static heterogeneity into compartmental epidemic models

Abstract: In this paper, we show how to modify a compartmental epidemic model, without changing the dimension, such that separable static heterogeneity is taken into account. The derivation is based on the Kermack-McKendrick renewal equation.

Local moisture recycling across the globe

Abstract: Atmospheric moisture recycling describes how moisture evaporated from land precipitates over land. It explains how shifts in terrestrial evaporation due to land cover changes may affect precipitation and freshwater availability across scales. Recycling at regional and continental scales has been studied using different methods, such as offline and online moisture tracking models and bulk recycling models. Although recycling at regional and continental scales is relatively well understood, it has only recently become possible to study local moisture recycling across the globe. Recent developments in offline moisture tracking resulted in a dataset including a 10-year climatology (2008-2017) of atmospheric moisture connections from evaporation source to precipitation sink at a spatial scale of 0.5° (Tuinenburg et al., 2020). We used this data to calculate the local moisture recycling ratio, which we define as the fraction of evaporated moisture that precipitates within a distance of 0.5° (typically 50 km) from its source. Furthermore, we identify variables that correlate with the local moisture recycling ratio to assess its underlying processes. On average, 1.7% (st. dev. = 1.1%) of terrestrial evaporated moisture returns as local precipitation annually. However, there is large spatial and temporal variability with peak values over mountainous and wet regions and in summer. Wetness (i.e., precipitation and precipitation minus evaporation), orography, latitude, convective available potential energy, wind speed and total cloud cover have moderate to strong correlations with the local moisture recycling ratio. Interestingly, we find peaks in the local moisture recycling ratio at latitudes where air ascends due to the Hadley cell circulation (i.e., at 0° and 60°). These results suggest that wet regions characterized by ascending air and low wind speeds are favourable for high local moisture recycling ratios. This knowledge can be used to strategically recycle water using nature-based solutions or irrigation to minimize the usage of freshwater availability. For example, for the tropics and mountainous regions globally, and for the Mediterranean regions on the Northern Hemisphere, an increase in evaporation through for example, regreening has a relatively large contribution to local precipitation due to the relatively large local moisture recycling ratios here. These results suggest the potential to enhance freshwater availability with land cover changes, e.g., regreening. ReferencesTuinenburg, Obbe A., Jolanda J.E. Theeuwen, and Arie Staal. "High-resolution global atmospheric moisture connections from evaporation to precipitation." Earth System Science Data 12.4 (2020): 3177-3188.

CSPP1 stabilizes growing microtubule ends and damaged lattices from the luminal side

Abstract: Microtubules are dynamic cytoskeletal polymers, and their organization and stability are tightly regulated by numerous cellular factors. While regulatory proteins controlling the formation of interphase microtubule arrays and mitotic spindles have been extensively studied, the biochemical mechanisms responsible for generating stable microtubule cores of centrioles and cilia are poorly understood. Here, we used in vitro reconstitution assays to investigate microtubule-stabilizing properties of CSPP1, a centrosome and cilia-associated protein mutated in the neurodevelopmental ciliopathy Joubert syndrome. We found that CSPP1 preferentially binds to polymerizing microtubule ends that grow slowly or undergo growth perturbations and, in this way, resembles microtubule-stabilizing compounds such as taxanes. Fluorescence microscopy and cryo-electron tomography showed that CSPP1 is deposited in the microtubule lumen and inhibits microtubule growth and shortening through two separate domains. CSPP1 also specifically recognizes and stabilizes damaged microtubule lattices. These data help to explain how CSPP1 regulates the elongation and stability of ciliary axonemes and other microtubule-based structures.

Relating the prosody of infant-directed speech to children’s vocabulary size

Abstract: This study examines correlations between the prosody of infant-directed speech (IDS) and children's vocabulary size. We collected longitudinal speech data and vocabulary information from Dutch mother-child dyads with children aged 18 (N = 49) and 24 (N = 27) months old. We took speech context into consideration and distinguished between prosody when mothers introduce familiar vs. unfamiliar words to their children. The results show that IDS mean pitch predicts children's vocabulary growth between 18 and 24 months. In addition, the degree of prosodic modification when mothers introduce unfamiliar words to their children correlates with children's vocabulary growth during this period. These findings suggest that the prosody of IDS, especially in word-learning contexts, may serve linguistic purposes.

Tuning the Properties of Biobased PU Coatings via Selective Lignin Fractionation and Partial Depolymerization

Abstract: Polyurethane (PU) coatings with high lignin content and tunable properties were made using a combination of fractionation and partial catalytic depolymerization as a novel strategy to tailor lignin molar mass and hydroxyl group reactivity, the key parameters for use in PU coatings. Acetone organosolv lignin obtained from pilot-scale fractionation of beech wood chips was processed at the kilogram scale to produce lignin fractions with specific molar mass ranges (Mw 1000-6000 g/mol) and reduced polydispersity. Aliphatic hydroxyl groups were distributed relatively evenly over the lignin fractions, allowing detailed study of the correlation between lignin molar mass and hydroxyl group reactivity using an aliphatic polyisocyanate linker. As expected, the high molar mass fractions exhibited low cross-linking reactivity, yielding rigid coatings with a high glass transition temperature (Tg). The lower Mw fractions showed increased lignin reactivity, extent of cross-linking, and gave coatings with enhanced flexibility and lower Tg. Lignin properties could be further tailored by lignin partial depolymerization by reduction (PDR) of the beech wood lignin and its high molar mass fractions; excellent translation of the PDR process was observed from laboratory to the pilot scale necessary for coating applications in prospective industrial scenarios. Lignin depolymerization significantly improved lignin reactivity, and coatings produced from PDR lignin showed the lowest Tg values and highest coating flexibility. Overall, this study provides a powerful strategy for the production of PU coatings with tailored properties and high (>90%) biomass content, paving the path to the development of fully green and circular PU materials.

Automatic Analysis of Human Body Representations in Western Art

Abstract: The way the human body is depicted in classical and modern paintings is relevant for art historical analyses. Each artist has certain themes and concerns, resulting in different poses being used more heavily than others. In this paper, we propose a computer vision pipeline to analyse human pose and representations in paintings, which can be used for specific artists or periods. Specifically, we combine two pose estimation approaches (OpenPose and DensePose, respectively) and introduce methods to deal with occlusion and perspective issues. For normalisation, we map the detected poses and contours to Leonardo da Vinci’s Vitruvian Man, the classical depiction of body proportions. We propose a visualisation approach for illustrating the articulation of joints in a set of paintings. Combined with a hierarchical clustering of poses, our approach reveals common and uncommon poses used by artists. Our approach improves over purely skeleton based analyses of human body in paintings.

The Agricultural Data Imaginary

Abstract: Big Data come with the promise of a better future. In the agricultural discourse on smart technologies and data-based applications in farming, so-called “precision farming” is envisioned as a “revolution” of traditional agricultural mass production of crops and livestock. Big Data are imagined as making the agrifood industry more efficient, more profitable, and more sustainable. Drawing on David Beer’s concept of the “data imaginary” (2019), this chapter examines discourses on precision farming in corporate advertisements, lobbyist agricultural journals, and review articles in academic journals in the field of agriculture and computing. It argues that data-based agrifood production is seen as the next technological fix of the broken system of traditional industrial farming, while it in fact reinforces the devastating environmental and social damages that traditional industrial farming has caused.

Fine microplastics and nanoplastics in particulate matter samples from a high alpine environment

Abstract: The steady high demand for plastics and the degradation of discarded materials have led to microplastics and nanoplastics becoming important pollutants in various environmental compartments. While the situation, e.g. in the marine environment, is frequently described in the literature, a focused research on ambient air and especially different size classes of airborne particulate matter is scarce. Still, airborne particles are of special importance, as they have high mobility and can be transported and distributed rapidly.We analysed particulate matter samples of two size classes, PM1 and PM10 (particles with aerodynamic diameters up to 1 or 10 µm, respectively), using thermal desorption-proton transfer reaction-mass spectrometry (TD-PTR-MS) and determined and quantified different polymer types from the spectra using a previously described method [1]. Particulate matter was collected at the remote high alpine Global Atmosphere Watch station Sonnblick Observatory, Austria, at more than 3100 m above sea level on quartz-fibre filters. Sampling time was one week. The samples covered a summer period (June 2021 to September 2021) and a winter period (December 2021 to April 2022). The periods were selected to include samples with and without mineral dust occurrence to allow a comparison. For the 23 samples of PM1 and PM10, analysis was done in triplicates. Field blanks were also available. Several lab and field tests were performed to check possible influences during the storage of samples (use of different containers including plastics and aluminium foil) and sample preparation (addition of hydrogen peroxide).Our evaluations include the determination of six common types of plastics (PET, PE, PP/PPC, PS, PVC, tire wear) in both fractions and seasonal differences in their relative contributions. The most abundant plastic types were PET, PE and PP/PPC. Overall polymer concentrations reached up to 125 ng/m³. Field blanks showed comparably low presence of PET. We further compare the relative contributions of the summer and winter periods depending on the occurrence of mineral dust. [1] Materić, D. et al., Micro- and Nanoplastics in Alpine Snow: A New Method for Chemical Identification and (Semi)Quantification in the Nanogram Range. Environmental science & technology 2020, 54(4), 2353-2359.

Detection and Quantification of Micro(nano)plastics Release from Photolysis of Surgical Masks

Abstract: Since the Covid-19 pandemic, 129 billion masks have been consumed each month worldwide. Fate of masks not only include waste disposal sites and natural environments, but masks made from synthetic fibers may release micro(nano)plastics (MNPLs) that may reach respiratory tracts. However, degradation rate of MNPLs generated from masks have been unknown.Here, we simulated the photolysis of surgical masks made from polypropylene equivalent to 900 days. Size-fractionated MNPL formation was quantified using vibrational spectroscopic imaging, and mask deformation and morphology were characterized with correlative microscopy. Three layers of masks did not exhibit signs of degradation from hydroxyl and carbonyl groups, however, the outer layer exhibited a linear increase in crystallinity calculated from the peak height of two characteristic bands, indicating that degradation started from amorphous regions. However, for microplastics > 10 &#956;m, both groups were observed, and mass concentration was 10 mg/item calculated from FTIR imaging data. Fine microplastics <10 &#956;m were imaged and fitted as ellipses, and the most abundant aspect ratio was 2. Nanoplastics (<1 &#956;m) with an average size of 149 (59) nm were detected by SEM/STEM and Raman spectroscopy. Cluster analyses on spectra categorized three groups, suggesting different additives (e.g., dyes) were added. This study detected nanoplastics from degraded masks, which have major implications for their environmental fate and human health effects.

Feedback between Water Availability and Crop Growth using a Coupled Hydrological – Crop Production Model

Abstract: Climate change and increases in extremes, such as heatwaves and droughts, threaten crop production and food security in various regions worldwide. Irrigation is increasingly used to secure stable yields, increasing the competition for available water resources with other sectors. To assess the vulnerability of crop production under present and future drought and heatwave events, the two-sided interactions between crop growth and hydrology should be represented by a coupled model system, combining the strength of both a crop model and a global water resource model.Our main objective, therefore, is to quantify the mutual feedback between crop production and hydrology under climate extremes (i.e., droughts and heatwaves) in various regions globally over the historical period 1990-2019. To this end, we have developed a coupled hydrological-crop model framework, coupling the PCR-GLOBWB2 water resources model to the WOFOST crop model. The coupled model framework operates on high spatiotemporal resolution (daily time step up to 5 arc minutes) to assess the two-way interaction between hydrology and crop production (maize, wheat, rice, and soybean) for irrigated and rainfed agriculture.&#160;We first established a one-way coupling to evaluate the effect of the simulated water availability in terms of soil moisture of PCR-GLOBWB2 on crop production in WOFOST. Next, we established a two-way coupling in which the vegetation dynamics of WOFOST determine the evapotranspiration, which is fed back into PCR-GLOBWB2 and affects the soil moisture status. The individual WOFOST and PCR-GLOBWB2 runs and the coupled one-way and two-way model runs were compared in terms of crop production, dynamic vegetation growth, and hydrological response. The results of our simulations will be corroborated with reported yield statistics, observed discharge data, soil moisture, evaporation data obtained from satellite remote sensing, and reported annual irrigation withdrawals to assess their validity. In addition, we will evaluate the additional variance that can be explained by the more complete process description in the coupled hydrological &#8211; crop production model framework. For example, we hypothesize that the one-way coupling overestimates the crop yields under drought-heatwave events.

Reviews and syntheses: Remotely sensed optical time series for monitoring vegetation productivity

Abstract: Abstract. Vegetation productivity is a critical indicator of global ecosystem health and is impacted by human activities and climate change. A wide range of optical sensing platforms, from ground-based to airborne and satellite, provide spatially continuous information on terrestrial vegetation status and functioning. As optical Earth observation (EO) data are usually routinely acquired, vegetation can be monitored repeatedly over time; reflecting seasonal vegetation patterns and trends in vegetation productivity metrics. Such metrics include e.g., gross primary productivity, net primary productivity, biomass or yield. To summarize current knowledge, in this paper, we systematically reviewed time series (TS) literature for assessing state-of-the-art vegetation productivity monitoring approaches for different ecosystems based on optical remote sensing (RS) data. As the integration of solar-induced fluorescence (SIF) data in vegetation productivity processing chains has emerged as a promising source, we also include this relatively recent sensor modality. We define three methodological categories to derive productivity metrics from remotely sensed TS of vegetation indices or quantitative traits: (i) trend analysis and anomaly detection, (ii) land surface phenology, and (iii) integration and assimilation of TS-derived metrics into statistical and process-based dynamic vegetation models (DVM). Although the majority of used TS data streams originate from data acquired from satellite platforms, TS data from aircraft and unoccupied aerial vehicles have found their way into productivity monitoring studies. To facilitate processing, we provide a list of common toolboxes for inferring productivity metrics and information from TS data. We further discuss validation strategies of the RS-data derived productivity metrics: (1) using in situ measured data, such as yield, (2) sensor networks of distinct sensors, including spectroradiometers, flux towers, or phenological cameras, and (3) inter-comparison of different productivity products or modelled estimates. Finally, we address current challenges and propose a conceptual framework for productivity metrics derivation, including fully-integrated DVMs and radiative transfer models here labelled as "Digital Twin". This novel framework meets the requirements of multiple ecosystems and enables both an improved understanding of vegetation temporal dynamics in response to climate and environmental drivers and also enhances the accuracy of vegetation productivity monitoring.

Cool, but Different: Climate Response to Solar Geo-Engineering Mediated by the AMOC

Abstract: Stratospheric Aerosol Injection (SAI) is a contentious geo-engineering proposal to lessen the impacts of global heating via an artificial shade of aerosols. While model results suggest that Earth&#8217;s global mean surface temperature (GMST) can indeed be stabilised via SAI, the same does not apply to other parts of the climate system. Especially the fate of a weakening Atlantic Meridional Overturning Circulation (AMOC) under SAI remains unclear.We simulate two SAI deployment scenarios in the Community Earth System Model 2 (CESM2) to study whether a weakened AMOC can be stabilised or recovered. To obtain a strong AMOC response, both scenarios follow a high GHG emission pathway. At the same time, proportionally chosen aerosol injections stabilise the GMST at 1.5K above pre-industrial conditions. The scenarios only differ in their deployment times: aerosol injections start either early (SAI 2020) or late century (SAI 2080).Both SAI scenarios reach the target GMST. However, we find that SAI only mitigates rather than decisively reverses AMOC decline. This relatively mild oceanic response stands in contrast to efficient surface cooling. As a result, both deployment scenarios lead to drastically different climate states. In particular, late-century deployment (SAI 2080) creates a striking temperature gradient from a cold northern to a warm southern hemisphere. This phenomenon potentially stems from impaired meridional heat transport of a much weaker AMOC in SAI 2080 compared to SAI 2020.Our findings mirror recent results on fast negative emission scenarios displaying a similar inter-hemispheric gradient likely connected to slow AMOC recovery. This affirms the need for carefully tailoring SAI deployment strategies should the technology ever be considered as part of the climate action portfolio.

Understanding the seasonal and spatial variation of water balance in the Karnali basin in Nepal

Abstract: The hydrology of large mountainous basins is sensitive to climate and land use change and impacts downstream availability in a diverse way. Our knowledge of the spatial and temporal variation of the water balance for large-scale mountainous basins like the Karnali (40,000 km2) is very limited.&#160; Studies focus either on small alpine catchments or on major river basins of near continental scale. Studies focusing on the intermediate scale, where mountain water supply is directly linked to people and ecosystems downstream are scarce, but needed. In this study, we provide insight into the seasonal and spatial differences in meltwater contribution to streamflow, rain runoff, evapotranspiration and groundwater baseflow, with a particular focus on upstream-downstream dependencies. We use a high-resolution SPHY model, which we calibrate step-wise using satellite data of glacier mass balance and snow covers and observed river flow data. We explore the hydrological variability at the sub-basin scale, discuss the seasonal and spatial heterogeneity of the water balance components, and seek to understand the major drivers. Our results provide a baseline against which impacts of climate and land use changes will be assessed in a subsequent study.

Nutrient dynamics in fen peat in relation to water level management: a mesocosm experiment

Abstract: Peatlands are valuable ecosystems that hold a high biodiversity and provide many ecosystem services such as carbon sequestration, water storage and water purification. However, a large part of the peatlands are drained, often for agricultural purposes, resulting in CO2 emissions, soil subsidence and biodiversity loss. To combat these negative effects, various rewetting measures are being installed which can be combined with varying land-uses such as intensive dairy farming, extensive agriculture, semi-natural grasslands, paludiculture (farming on moist/wet soils) and nature restoration. This broad applicability implies that the extent by which the groundwater level is raised can be fine-tuned to the intended land use. In our study, we conducted a mesocosm experiment in which we exposed intact fen peat cores (80cm, 20cm &#216;) to five different water levels (0, 20, 40, 60 cm and variable - surface), two nutrient application levels and two water qualities. For an eight-month period, monthly samples from each peat core were taken at two depths and chemically analyzed. Further, the vegetation in the cores was cut five times throughout the growing season. Above-ground biomass was measured as well as nutrient concentrations in the vegetation. Our results show increased phosphate and ammonium availability upon fully rewetting (0 cm &#8211; surface), in contrast to partially rewetted circumstances (20cm &#8211; surface) where nutrient availability was lowest. Above-ground biomass was strongly affected by nutrient application and, except for early spring growth, less by water levels. Nitrogen concentrations in the vegetation decreased with increasing water levels indicating stronger nitrogen limitation. This is likely the result of increased denitrification rates under wet circumstances. We conclude that in order to achieve nature restoration under fully rewetted conditions, additional steps must be taken to remove nutrients, particularly phosphorus, from the system. Further, we conclude that partial rewetting can be a solution to slow down the adverse effects of drainage, although agricultural production will decrease.&#160;

A song of ice and friction: the impact of basal friction and proglacial lakes on Pleistocene glacial cycles

Abstract: During the Mid Pleistocene Transition (MPT; 1.2-0.7 Ma) the periodicity of glacial cycles changed from 40 ka to ~100 ka, without a coinciding change in orbital forcing. The MPT therefore results from feedback and changes in the climate system and ice dynamics triggered by the changes in radiative forcing. However, it remains unclear which physical processes are critical for the transition.Here we explore the role of basal sliding and glacial isostatic adjustment (GIA) in the MPT. Basal sliding is thought to have changed across the MPT due to the erosive action of the ice sheets gradually removing the regolith cover and exposing the underlying bedrock, therefore increasing the friction at the base. GIA modulates this effect by enabling the formation of large proglacial lakes, changing the ice margin from a land-based to a marine environment. We simulate the evolution of the Northern Hemisphere ice sheets during the past 1.5 million years, using an ice-sheet model forced by a climate matrix method.We show that changing the basal friction has an effect on glacial terminations and consequentially glacial cycle periodicity. Larger friction leads to thicker ice sheets that are more likely to survive a climatic optimum. However,&#160;we show that using an unchanging friction coefficient through the Pleistocene, our model still produces change from&#160;40 ka to 100 ka periodicities signifying the MPT. This suggest that the regolith&#160;hypothesis&#160;is not necessary to explain the MPT.In addition, we show that the formation of proglacial lakes is required for achieving a full deglaciation of the large Late Pleistocene ice sheets. Ice that floats on water experiences no friction at the base, resulting in high ice velocities. This results in more ice in lower regions and enhances the melt of ice. Here, we find a strong modulating role of GIA. When neglecting bedrock adjustment, thus preventing the formation of large proglacial lakes, we fail to simulate a full deglaciation.

1. Introducing the Philosophy of Limitarianism

Abstract: This chapter starts by describing the basic intuition of limitarianism, namely that there can be situations in which a person has accumulated too many material resources. It then gives some brief comments on the recent emergence of this literature, as well as its development. Next, it moves to describing the three aims of the volume: to provide an overview of the literature, to advance novel arguments, and to bring the debates on economic limitarianism and ecological limitarianism more into conversation. The chapter closes by discussing some areas of future work.