Modeling approaches and performance for estimating personal exposure to household air pollution: A case study in Kenya

This study assessed the performance of modeling approaches to estimate personal exposure in Kenyan homes where cooking fuel combustion contributes substantially to household air pollution (HAP). We measured emissions (PM_2.5, black carbon, CO); household air pollution (PM_2.5, CO); personal exposure (PM_2.5, CO); stove use; and behavioral, socioeconomic, and household environmental characteristics (eg, ventilation and kitchen volume). We then applied various modeling approaches: a single-zone model; indirect exposure models, which combine person-location and area-level measurements; and predictive statistical models, including standard linear regression and ensemble machine learning approaches based on a set of predictors such as fuel type, room volume, and others. The single-zone model was reasonably well-correlated with measured kitchen concentrations of PM_2.5 (R² = 0.45) and CO (R² = 0.45), but lacked precision. The best performing regression model used a combination of survey-based data and physical measurements (R² = 0.76) and a root mean-squared error of 85 µg/m³, and the survey-only-based regression model was able to predict PM2.5 exposures with an R² of 0.51. Of the machine learning algorithms evaluated, extreme gradient boosting performed best, with an R² of 0.57 and RMSE of 98 µg/m³.     

Histone Deacetylase 2 (HDAC2) Inhibitors Containing Boron

Histone deacetylase enzymes (HDACs) are responsible for the global silencing of tumour-suppressor genes. Treatment with a histone deacetylase inhibitor (HDACi) can reverse this process and restore normal cell function. Herein, we report a small series of boron-based (boronic acid, boronate ester and closo-1,2-carborane) HDAC2 inhibitors with IC₅₀ values in the nanomolar range. The boronate ester 4 b was the most potent compound assessed in this study (IC₅₀=40.6±1.5 nM), followed closely by the 1,2-closo-carborane (IC₅₀=42.9±1.5 nM). Compound 4 b exceeds the potency of the related gold-standard HDAC pan-inhibitor vorinostat ( 1 ) toward this particular HDAC isoform.     

Chemical warfare and survival strategies in bacterial range expansions

Dispersal of species is a fundamental ecological process in the evolution and maintenance of biodiversity. Limited control over ecological parameters has hindered progress in understanding of what enables species to colonize new areas, as well as the importance of interspecies interactions. Such control is necessary to construct reliable mathematical models of ecosystems. In our work, we studied dispersal in the context of bacterial range expansions and identified the major determinants of species coexistence for a bacterial model system of three Escherichia coli strains (toxin-producing, sensitive and resistant). Genetic engineering allowed us to tune strain growth rates and to design different ecological scenarios (cyclic and hierarchical). We found that coexistence of all strains depended on three strongly interdependent factors: composition of inoculum, relative strain growth rates and effective toxin range. Robust agreement between our experiments and a thoroughly calibrated computational model enabled us to extrapolate these intricate interdependencies in terms of phenomenological biodiversity laws. Our mathematical analysis also suggested that cyclic dominance between strains is not a prerequisite for coexistence in competitive range expansions. Instead, robust three-strain coexistence required a balance between growth rates and either a reduced initial ratio of the toxin-producing strain, or a sufficiently short toxin range.     

Self-assembled microstructured polymeric and ceramic surfaces

Self-assembled microstructures were manufactured by dip coating of substrates with unfilled and filler-loaded preceramic polymer mixtures in the presence of a solvent and a non-solvent. The nature of the polymers was characterized by their solubility parameters. Variation of the polymer/polymer ratio and the volume fraction of the solvent and/or non-solvent led to different surface structures. Studies of the structure formation mechanism indicate that demixing processes of the polymers are responsible for self-assembly in filler-free mixtures. In filler-loaded mixtures the structure formation process, however, is more complex. The micro-structured polymeric coatings obtained from filler loaded systems were converted into polymer derived ceramic coatings under shape retention. High specific surface areas were measured after thermal conversion.     

Palladium-Catalyzed Arylation Reactions: A Mechanistic Perspective

After being restricted for the intramolecular formation of C–C bonds, the palladium catalyzed arylation reaction has been extended for the intermolecular synthesis of biaryls systems. Many of these reactions have been demonstrated to proceed by mechanisms that involve a concerted metalation–deprotonation, in which the base plays an important role in the proton abstraction. Other mechanisms based on electrophilic aromatic substitution and on Pd^II/Pd^IV or Pd^II/Pd^III catalytic cycles have also been proposed. This review summarizes the most important recent advancements on the mechanistic understanding of the different types of palladium-catalyzed arylations reactions.     

Interaction of hIAPP with Model Raft Membranes and Pancreatic β‐Cells: Cytotoxicity of hIAPP Oligomers

Type II diabetes mellitus (T2DM) is associated with β‐cell failure, which correlates with the formation of pancreatic islet amyloid deposits. The human islet amyloid polypeptide (hIAPP) is the major component of islet amyloid and undergoes structural changes followed by self‐association and pathological tissue deposition during aggregation in T2DM. There is clear evidence that the aggregation process is accelerated in the presence of particular lipid membranes. Whereas hIAPP aggregation has been extensively studied in homogeneous model membrane systems, especially negatively charged lipid bilayers, information on the interaction of hIAPP with heterogeneous model raft membranes has been missing until now. In the present study, we focus on the principles of aggregation and amyloid formation of hIAPP in the presence of model raft membranes. Time‐lapse tapping mode AFM and confocal fluorescence microscopy experiments followed membrane permeabilization and localization of hIAPP in the raft membrane. Together with the ThT and WST‐1 assay, the data revealed elevated cytotoxicity of hIAPP oligomers on INS‐1E cells.     

Structure and formation of ant transportation networks

Many biological systems use extensive networks for the transport of resources and information. Ants are no exception. How do biological systems achieve efficient transportation networks in the absence of centralized control and without global knowledge of the environment? Here, we address this question by studying the formation and properties of inter-nest transportation networks in the Argentine ant (Linepithema humile). We find that the formation of inter-nest networks depends on the number of ants involved in the construction process. When the number of ants is sufficient and networks do form, they tend to have short total length but a low level of robustness. These networks are topologically similar to either minimum spanning trees or Steiner networks. The process of network formation involves an initial construction of multiple links followed by a pruning process that reduces the number of trails. Our study thus illuminates the conditions under and the process by which minimal biological transport networks can be constructed.     

Porous protein-based scaffolds prepared through freezing as potential scaffolds for tissue engineering

Successful tissue engineering with the aid of a polymer scaffold offers the possibility to produce a larger construct and to mould the shape after the defect. We investigated the use of cryogelation to form protein-based scaffolds through different types of formation mechanisms; enzymatic crosslinking, chemical crosslinking, and non-covalent interactions. Casein was found to best suited for enzymatic crosslinking, gelatin for chemical crosslinking, and ovalbumin for non-covalent interactions. Fibroblasts and myoblasts were used to evaluate the cryogels for tissue engineering purposes. The stability of the cryogels over time in culture differed depending on formation mechanism. Casein cryogels showed best potential to be used in skeletal tissue engineering, whereas gelatin cryogels would be more suitable for compliable soft tissues even though it also seemed to support a myogenic phenotype. Ovalbumin cryogels would be better suited for elastic tissues with faster regeneration properties due to its faster degradation time. Overall, the cryogelation technique offers a fast, cheap and reproducible way of creating porous scaffolds from proteins without the use of toxic compounds.     

Mixed crystalline films of co-evaporated hydrogen- and fluorine-terminated phthalocyanines and their application in photovoltaic devices

Blends of organic electron and hole conductive materials are widely used for ambipolar charge carrier transport and photovoltaic cells. An obvious choice for donor–acceptor blends are organic semiconducting materials in their hydrogenated and fluorinated form, since they combine potentially suitable electronic properties with structural compatibility of the two constituents. This study focuses on the structural, optical, and electrical properties of blends using hydrogenated copper-phthalocyanine (H₁₆CuPc) in combination with its per-fluorinated version (F₁₆CuPc). Using X-ray scattering, scanning force microscopy and optical absorption measurements we show that mixed crystalline films are obtained by co-evaporation of the two materials. Electrical transport measurements reveal a profound reduction of the current for bipolar charge injection in mixed films. We discuss the formation of self-trapped charge transfer excitons as possible explanation for this unexpected behaviour, which impedes the usability of this system in photovoltaic cells.