Confirming the trilinear form of the optical magnetoelectric effect in the polar honeycomb antiferromagnet Co2Mo3O8

Magnetoelectric phenomena are intimately linked to relativistic effects and also require the material to break spatial inversion symmetry and time-reversal invariance. Magnetoelectric coupling can substantially affect light–matter interaction and lead to non-reciprocal light propagation. Here, we confirm on a fully experimental basis, without invoking either symmetry-based or material-specific assumptions, that the optical magnetoelectric effect in materials with non-parallel magnetization (M) and electric polarization (P) generates a trilinear term in the refractive index, δn ∝ k ⋅ (P × M), where k is the propagation vector of light. Its sharp magnetoelectric resonances in the terahertz regime, which are simultaneously electric and magnetic dipole active excitations, make Co2Mo3O8 an ideal compound to demonstrate this fundamental relation via independent variation of M, P, and k. Remarkably, the material shows almost perfect one-way transparency in moderate magnetic fields for one of these magnetoelectric resonances.

The Effect of Operating Parameters of Alkali Catalyzed Transesterification of Sunflower Oil With Methanol in the Presence of the Cosolvent Assisted by Hydrodynamic Cavitation on the Degree of Triglyceride Conversion

Method of independent variation of the value of one operating parameter has been used to investigate the effect of operating parameters on alkali-catalyzed transesterification of sunflower oil with methanol in presence of tetrahydrofuran (THF) as cosolvent, assisted by hydrodynamic cavitation (ACTC) on the value of the degree of triglyceride conversion (DTC). ACTC was performed by a venturi-type hydrodynamic cavitation reactor (VCR) of our construction. To determine the effect of ACTC on DTC following operating parameters were varied: reaction mixture inlet pressure (p1) from 202.3 kPa to 1013.2 kPa; methanol to oil molar ratio (M1) from M1=3 to M1=12; concentration of catalyst (Cc) from 0.3wt% to 1.5wt%; methanol to THF molar ratio (M2) from M2=1.25 to M2=2.0; temperature (T) from 20°C to 55°C, number of passes through the VCR (n) from n=1 to n=10. It was found, based on the obtained results, that: a) the values of DTC increase with the increase in p1, M1, Cc, and n, b) the values of the DTC decrease with the increase in T and c) maximum values of the DTC are obtained at Cc=1.0~1.1wt% and M2=1.5.

On the hybrid origin of the C2Salsola divaricata agg. (Amaranthaceae) from C3 and C4 parental lineages

C2 photosynthesis is characterized by recapturing photorespiratory CO2 by RuBisCO in Kranz-like cells and is therefore physiologically intermediate between C3 and C4 photosynthesis. C2 is either interpreted as an evolutionary precursor of C4 or as the result of hybridization between a C3 and C4 lineage. We compared the expression of photosynthetic traits among populations of the Salsola divaricata agg. (C2) from humid subtropical to arid habitats on the coasts of the Canary Islands and Morocco, and subjected them to salt and drought treatments. We screened for enhanced C4-like expression of traits related to habitat or treatment. We estimated species trees with a transcriptome dataset of Salsoleae and explored patterns of gene tree discordance. With phylogenetic networks and hybridization analyses we tested for hybrid origin of the Salsola divaricata agg. We observed independent variation of photosynthetic traits within and among populations and no clear evidence for selection towards C4-like trait expression in more stressful habitats or treatments. We found reticulation and gene tree incongruencies in the Salsoleae supporting a putative hybrid origin of the Salsola divaricata agg. C2 photosynthesis in the Salsola divaricata agg. combines traits inherited from its C3 and C4 parental lineages and seems well adapted to a wide climatic amplitude.

The Oxygen Reduction Reaction on Pt: Why Particle Size and Inter-particle Distance Matter

<p>Carbon supported Pt based nanoparticles are important electrocatalysts for energy conversion reactions such as the oxygen reduction reaction (ORR). Although this reaction has been extensively studied, the influence of factors such as the particle size and inter-particle distance of the nanoparticle-based or nano-sized electrocatalysts on the ORR activity and durability are not yet fully understood and often intertwined. This lack of understanding is mostly based on the limitation in the synthetic approaches of the electrocatalysts which usually do not allow an independent variation of particle size and inter-particle distance. In the presented work, we succeeded to disentangle both factors using a “colloidal toolbox” approach and have demonstrated an effect of the inter-particle distance on the electronic properties of the nanoparticle via <i>operando</i> electrochemical X-ray absorption spectroscopy (XAS). </p>

Independent Variation of Reynolds Number, Wall Shear Stress and Flow Velocity for Cleaning Experiments: A Geometrically Flexible Parallel Plate Flow Cell

For a long time, determining the factors influencing the cleaning of technical surfaces in the food and beverage industry has been of significant interest. In this study, an innovative test setup with a newly designed parallel plate flow cell was implemented to assess the cleaning of soluble molecular fouling materials, which allows for the independent variation of flow parameters, such as the Reynolds number, velocity, and wall shear stress. The test setup used fluorescence spectroscopy; it was found to produce reliable measurements of cleaning, and the results were confirmed with the help of another fluorescent tracer. A comparison of cleaning times for both equipment revealed that the cleaning times tend to have a geometrically independent power-law relationship with the wall shear stress and velocity, and they were used to directly correlate the cleaning times of the used soluble fouling material. However, the Reynolds number showed a geometric dependence on cleaning times. Nevertheless, on dividing the Reynolds number with respective channel characteristic lengths, geometric independence was observed, and, therefore, a correlation was obtained. We also suggest that complex fouling materials should still be investigated to elucidate their cleaning mechanisms better and test for parameter influences on complex cleaning mechanisms.

The Oxygen Reduction Reaction on Pt: Why Particle Size and Inter-particle Distance Matter

<p>Carbon supported Pt based nanoparticles are important electrocatalysts for energy conversion reactions such as the oxygen reduction reaction (ORR). Although this reaction has been extensively studied, the influence of factors such as the particle size and inter-particle distance of the nanoparticle-based or nano-sized electrocatalysts on the ORR activity and durability are not yet fully understood and often intertwined. This lack of understanding is mostly based on the limitation in the synthetic approaches of the electrocatalysts which usually do not allow an independent variation of particle size and inter-particle distance. In the presented work, we succeeded to disentangle both factors using a “colloidal toolbox” approach and have demonstrated an effect of the inter-particle distance on the electronic properties of the nanoparticle via <i>operando</i> electrochemical X-ray absorption spectroscopy (XAS). </p>

The Oxygen Reduction Reaction on Pt: Why Particle Size and Inter-particle Distance Matter

<p>Carbon supported Pt based nanoparticles are important electrocatalysts for energy conversion reactions such as the oxygen reduction reaction (ORR). Although this reaction has been extensively studied, the influence of factors such as the particle size and inter-particle distance of the nanoparticle-based or nano-sized electrocatalysts on the ORR activity and durability are not yet fully understood and often intertwined. This lack of understanding is mostly based on the limitation in the synthetic approaches of the electrocatalysts which usually do not allow an independent variation of particle size and inter-particle distance. In the presented work, we succeeded to disentangle both factors using a “colloidal toolbox” approach and have demonstrated an effect of the inter-particle distance on the electronic properties of the nanoparticle via <i>operando</i> electrochemical X-ray absorption spectroscopy (XAS). </p>

Modeling pulsed evolution and time-independent variation improves the confidence level of ancestral and hidden state predictions in continuous traits

Ancestral state reconstruction is a fundamental tool for studying trait evolution. It is also very useful for predicting the unknown trait values (hidden states) of extant species. A well-known problem in ancestral and hidden state predictions is that the uncertainty associated with predictions can be so large that predictions themselves are of little use. Therefore, for meaningful interpretation of predicted traits and hypothesis testing, it is prudent to accurately assess the uncertainty of the predictions. Commonly used Brownian motion (BM) model fails to capture the complexity of tempo and mode of trait evolution in nature, making predictions under the BM model vulnerable to lack-of-fit errors from model misspecification. Using simulations and empirical data (bacterial genomic traits and vertebrate body size), we show that the presence of pulsed evolution and time-independent variation significantly undermines the confidence level of continuous traits predicted under the BM model. The residual Z-scores are neither homoscedastic nor normally distributed. Consequently, the 95% confidence intervals of predicted traits are so unreliable that the actual coverage probability ranges from 29% (strongly permissive) to 100% (strongly conservative). To remedy the model misspecification problem, we develop RasperGade that accounts for both pulsed evolution and time-independent variation. When applied to simulated and empirical data, RasperGade outperforms commonly used tools such as ape. It restores the normality and homoscedasticity of the Z-score distributions. Accordingly, RasperGade greatly improves the reliability of confidence intervals of predictions and reduces the deviation of their actual coverage probabilities from the 95% expectation by as much as 99%.

An idealized physical model for the severe convective storm environmental sounding

This work develops a theoretical model for steady thermodynamic and kinematic profiles for severe convective storm environments, building off of the two-layer static energy framework developed in Agard and Emanuel (2017). The model is phrased in terms of static energy, and it allows for independent variation of the boundary layer and free troposphere separated by a capping inversion. An algorithm is presented to apply the model to generate a sounding for numerical simulations of severe convective storms, and the model is compared and contrasted with that of Weisman and Klemp. The model is then fit to a case-study sounding associated with the 3 May 1999 tornado outbreak, and its potential utility is demonstrated via idealized numerical simulation experiments. A long-lived supercell is successfully simulated with the historical sounding but not the analogous theoretical sounding. Two types of example experiments are then performed that do simulate a long-lived supercell: 1) a semi-theoretical experiment in which a portion of the theoretical sounding is modified to match the real sounding (low-level moisture); 2) a fully-theoretical experiment in which a model physical parameter is modified (free-tropospheric relative humidity). Overall, the construction of this minimal model is flexible and amenable to additional modifications as needed. The model offers a novel framework that may be useful for testing how severe convective storms depend on the vertical structure of the hydrostatic environment, as well as for linking variability in these environments to the physical processes that produce them within the climate system.