A general hybrid radiation transport scheme for star formation simulations on an adaptive grid

Radiation feedback plays a crucial role in the process of star formation. In order to simulate the thermodynamic evolution of disks, filaments, and the molecular gas surrounding clusters of young stars, we require an efficient and accurate method for solving the radiation transfer problem. We describe the implementation of a hybrid radiation transport scheme in the adaptive grid-based FLASH general magnetohydrodynamics code. The hybrid scheme splits the radiative transport problem into a raytracing step and a diffusion step. The raytracer captures the first absorption event, as stars irradiate their environments, while the evolution of the diffuse component of the radiation field is handled by a flux-limited diffusion (FLD) solver. We demonstrate the accuracy of our method through a variety of benchmark tests including the irradiation of a static disk, subcritical and supercritical radiative shocks, and thermal energy equilibration. We also demonstrate the capability of our method for casting shadows and calculating gas and dust temperatures in the presence of multiple stellar sources. Our method enables radiation-hydrodynamic studies of young stellar objects, protostellar disks, and clustered star formation in magnetized, filamentary environments.Comment: 16 pages, 15 figures, accepted to Ap

Mechanism of Electrospray Supercharging for Unfolded Proteins: Solvent-Mediated Stabilization of Protonated Sites During Chain Ejection.

Proteins that are unfolded in solution produce higher charge states during electrospray ionization (ESI) than their natively folded counterparts. Protein charge states can be further increased by the addition of supercharging agents (SCAs) such as sulfolane. The mechanism whereby these supercharged [M + zH] z+ ions are formed under unfolded conditions remains unclear. Here we employed a combination of mass spectrometry (MS), ion mobility spectrometry (IMS), and molecular dynamics (MD) simulations for probing the ESI mechanism under denatured supercharging conditions. ESI of acid-unfolded apo-myoglobin (aMb) in the presence of sulfolane produced charge states around 27+, all the way to fully protonated (33+) aMb. MD simulations of aMb 27+ to 33+ in Rayleigh-charged water/sulfolane droplets culminated in electrostatically driven protein expulsion, consistent with the chain ejection model (CEM). The electrostatically stretched conformations predicted by these simulations were in agreement with IMS experiments. The CEM involves partitioning of mobile H+ between the droplet and the departing protein. Our results imply that supercharging of unfolded proteins is caused by residual sulfolane that stabilizes protonated sites on the protruding chains, thereby promoting H+ retention on the protein. The stabilization of charged sites is due to charge-dipole interactions mediated by the large dipole moment and the low volatility of sulfolane. Support for this mechanism comes from the experimental observation of sulfolane adducts on the most highly charged ions, a phenomenon previously noted by Venter ( J. Am. Soc. Mass Spectrom. 2012, 23, 489-497). The CEM supercharging model proposed here for unfolded proteins is distinct from the charge trapping mechanism believed to be operative during native ESI supercharging

Fatigue phase-field damage modeling of rubber using viscous dissipation: Crack nucleation and propagation

By regularizing sharp cracks within a pure continuum setting, phase-damage models offer the ability to capture crack nucleation as well as crack propagation. Crack branching and coalescence can furthermore be described without any additional efforts, as geometrical descriptions of the cracks are not required. In this contribution, we extend our previous phase-field model for rate-dependent fracture of rubbers in a finite strain setting (Loew et al., 2019) to describe damage under cyclic loading. The model is derived from the balance of mechanical energy and introduces a fatigue damage source as a function of the accumulated viscous dissipation under cyclic loading. We use uniaxial cyclic tension to present the influence of the fatigue material parameters and to confirm the model’s energy balance. The parameters are subsequently identified using monotonic and cyclic experiments of a plane stress nature. Finally, the model is validated by separate experiments, which demonstrate that the model accurately predicts (fatigue) crack nucleation as well as propagation

No stain, no pain – A multidisciplinary review of factors underlying domestic laundering

Today\u27s washing appliances are much more efficient than those of a decade ago, but the environmental benefits of this efficiency are counteracted by shifts in consumer behavior. Initiatives to reverse these shifts have often proven futile, indicating a basic lack of clarity on why we clean our clothes. This article is an explorative review with the aim of identifying dominant factors that shape how we do our laundry. The results can be used both as an introduction to laundry research in general, as well as a baseline for future interdisciplinary research. Three guiding principles are presented that describe the most influential factors underlying laundering: (1) technology changes conventions, while social context dictates technology acceptance; (2) technological solutions are often suggested to influence consumers, but individual concerns seem to override the effect of such interventions; (3) consumers are guided by social conventions, rooted in underlying psychological dynamics (e.g. moral dimensions of cleanliness). Looking at these principles it is understandable why interventions for sustainability are failing. Many interventions address only a part of a principle while disregarding other parts. For example, consumers are often informed of the importance of sustainability (e.g. “washing at lower temperature is good for the environment”), while questions of social belonging are left out (e.g. “many of your neighbors and friends wash at lower temperature”). To increase the possibility of a lasting change, it would be beneficial if instead all of the three principles could be addressed given the specific consumer group of interest

Mind the (reporting) gap—a scoping study comparing measured laundry decisions with self-reported laundry behaviour

Purpose: Many environmental assessments of consumer products and household services rely on self-reported data. Life cycle assessments of domestic laundering are no exception. However, potential discrepancies between self-reported behaviour and actual everyday decisions are seldom investigated due to practical challenges in collecting relevant data. This means that environmental impacts relying on such self-reported data are much more uncertain than previously acknowledged. Method: Laundering data was collected at the Chalmers’ HSB Living lab (CHSBLL), a combined multi-family house and research facility in Gothenburg. The collection was both done passively (through the washing machines) as well as actively (through surveys to the tenants). RFID-readers were also installed in the machines and a number of clothing items tagged, allowing for identification. The site-specific data was later supplemented with a large statistical representative study for domestic laundering of Swedish households. This unique data quality allowed the comparison of passively collected data with survey data from tenants in a real-life setup, while validating the results from a national perspective. Result and conclusions: The results suggest that consumers have trouble remembering personal choices regarding domestic laundering, meaning that self-reported data are more uncertain than previously thought. In general, the participants overestimated the amount of laundry they washed and underestimated their frequency of washing. Additionally, many participants showed an interest in changing to alternative wash programs although this change failed to materialize when they were presented with this option in real-life. The findings have potential consequences for environmental assessments and implicate those previous estimations underestimate emissions per kg laundry washed

Gekoppelte Substitutionen im Melilith- und Sodalith-Strukturtyp

Since its formulation 50 years ago, Loewenstein’s rule has become a standard argument in the crystal chemistry of, notably, layer and framework silicates and zeolites. The validity of the rule is usually taken for granted, and it is used rather schematically. The rule is normally used as an argument to account for two experimental observations: i) In alumosilicates, AlO4-tetrahedra tend to avoid each other, leading to alternating AlO4- and SiO4-tetrahedra for a Si : Al ratio of 1:1; ii) Except in rare cases, alumosilicates have an Al : Si ratio smaller than or equal to 1. While observation i) could be rationalized theoretically, observation ii) is not easily explained, in fact, it does not seem that fully convincing arguments have been put forward for its explanation. We have prepared series of compounds where Loewenstein’s rule is breached systematically, and continuously. These belong either to the melilite, or to the sodalite structure type. Crystallographic, structural, chemical and physical features and properties have been determined and are reported

Charging and supercharging of proteins for mass spectrometry: recent insights into the mechanisms of electrospray ionization.

Electrospray ionization (ESI) is an essential technique for transferring proteins from solution into the gas phase for mass spectrometry and ion mobility spectrometry. The mechanisms whereby [M + zH]z+ protein ions are released from charged nanodroplets during ESI have been controversial for many years. Here we discuss recent computational and experimental studies that have shed light on many of the mysteries in this area. Four types of protein ESI experiments can be distinguished, each of which appears to be associated with a specific mechanism. (i) Native ESI proceeds according to the charged residue model (CRM) that entails droplet evaporation to dryness, generating compact protein ions in low charge states. (ii) Native ESI supercharging is also a CRM process, but the dried-out proteins accumulate additional charge because supercharging agents such as sulfolane interfere with the ejection of small ions (Na+, NH4+, etc.) from the shrinking droplets. (iii) Denaturing ESI follows the chain ejection model (CEM), where protein ions are gradually expelled from the droplet surface. H+ equilibration between the droplets and the protruding chains culminates in highly charged gaseous proteins, analogous to the collision-induced dissociation of multi-protein complexes. (iv) Denatured ESI supercharging also generates protein ions via the CEM. Supercharging agents stabilize protonated sites on the protein tail via charge-dipole interactions, causing the chain to acquire additional charge. There will likely be scenarios that fall outside of these four models, but it appears that the framework outlined here covers most of the experimentally relevant conditions