The majority of neurons in the neuronal systems of the brain have a complex structure of the morphology, which diversifies the dynamics of neurons. In the granule layer of the cerebellum, there exists a unique cell type, unipolar brush cell (UBC), serving as an important relay cell to transfer information from outside mossy fibers to downstream granule cells. The distinguishing feature of UBC is that it has a simple morphology with only one short dendritic brush connected its soma. Based on experimental evidence showing that UBCs exhibit a variety of dynamic behaviors, here we develop two simple models, one with a few detailed ion channels for simulation, and the other one as a two-variable dynamical system for theoretical analysis, to characterize the intrinsic dynamics of UBCs. The reasonable values of the key channel parameters of the models can be determined by analysis of the stability of the resting membrane potential and the rebound firing properties of UBCs. Together with a large variety of synaptic dynamics installed on UBCs, we show the simple structured UBCs, as relay cells, can extend the range of dynamics and information from input mossy fibers to granular cells with low-frequency resonance, and transfer the stereotyped input to diverse amplitudes and phases of the output for downstream granule cells. These results suggest that neuronal computation, embedded with intrinsic ion channels and diverse synaptic properties on single neurons without sophisticated morphology, can shape a large variety of dynamic behaviors to enhance the computational ability of local neuronal circuits.
Researchers have used different measures to examine participants’ second-language (L2) proficiency, yet it remains unclear how these different measures influence research results on the effect of L2 proficiency on the target variable. The present research explored the modulation effect of four different measures of L2 Chinese proficiency on Chinese phonological awareness (PA). Eighty-four L2 learners of Chinese who spoke English or Arabic as their first language completed four different measures of Chinese proficiency: a self-report measure of years of instruction in Chinese, a simplified Hanyu Shuiping Kaoshi (HSK; a standardized Chinese language proficiency test), a reading comprehension test, and a Chinese character recognition test. The overall results of t tests and multiple regression analysis revealed that different measures of L2 proficiency led to various findings on the effect of L2 proficiency on Chinese PA. Compared with the other three measures, the HSK, a comprehensive examination of L2 Chinese proficiency, yielded the most consistent and reliable results with the largest effect size. Our findings contribute to the current understanding of L2 proficiency measures and to future efforts for the improvement of L2 proficiency tests for research purposes.
We theoretically investigate strong-filed electron vortices in time-delayed circularly polarized laser pulses by a generalized quantum-trajectory Monte Carlo (GQTMC) model. Vortex interference patterns in photoelectron momentum distributions (PMDs) with various laser parameters can be well reproduced by the semiclassical simulation. The phase difference responsible for the interference structures is analytically identified through trajectory-based analysis and simple-man theory, which reveal the underlying mechanism of electron vortex phenomena for both co-rotating and counter-rotating component. This semiclassical analysis can also demonstrate the influences of laser intensity and wavelength on the number of arms of vortices. Furthermore, we show the influence of the Coulomb effect on the PMDs. Finally, the controlling of the ionization time intervals in the tens to hundreds of attosecond magnitude is qualitatively discussed.
Ferrihydrite (Fh) is a major Fe(III)-(oxyhydr)oxide nanomineral distinguished by its poor crystallinity and thermodynamic metastability. While it is well known that in suboxic conditions aqueous Fe(II) rapidly catalyzes Fh transformation to more stable crystalline Fe(III) phases such as lepidocrocite (Lp) and goethite (Gt), because of the low solubility of Fe(III) the mass transfer pathways enabling these rapid transformations have remained unclear for decades. Here, using a selective extractant, we isolated and quantified a critical labile Fe(III) species, one that is more reactive than Fe(III) in Fh, formed by the oxidation of aqueous Fe(II) on the Fh surface. Experiments that compared time-dependent concentrations of solid-associated Fe(II) and this labile Fe(III) against the kinetics of phase transformation showed that its accumulation is directly related to Lp/Gt formation in a manner consistent with the classical nucleation theory. 57Fe isotope tracer experiments confirm the oxidized Fe(II) origin of labile Fe(III). The transformation pathway as well as the accelerating effect of Fe(II) can now all be explained on a unified basis of the kinetics of Fe(III) olation and oxolation reactions necessary to nucleate and sustain growth of Lp/Gt products, rates of which are greatly accelerated by labile Fe(III).
espite successful modeling of graphene as a 0.34-nm-thick optical film synthesized by exfoliation or chemical vapor deposition (CVD), graphene-induced shift of surface-plasmon resonance (SPR) of gold films has remained controversial. Here we report the resolution of this controversy by developing a clean CVD graphene transfer method and extending Maxwell-Garnett effective-medium theory (EMT) to two-dimensional (2D) materials. A SPR shift of 0.24° is obtained and it agrees well with 2D EMT in which wrinkled graphene is treated as a 3-nm graphene/air layered composite, in agreement with the average roughness measured by atomic force microscopy. Because the anisotropic built-in boundary condition of 2D EMT is compatible with graphene's optical anisotropy, graphene can be modeled as a film thicker than 0.34 nm without changing its optical property; however, its actual roughness, i.e., effective thickness, will significantly alter its response to strong out-of-plane fields, leading to a larger SPR shift.
Abstract A key challenge in ecology is to understand the relationships between organismal traits and ecosystem processes. Here, with a novel dataset of leaf length and width for 10 480 woody dicots in China and 2374 in North America, we show that the variation in community mean leaf size is highly correlated with the variation in climate and ecosystem primary productivity, independent of plant life form. These relationships likely reflect how natural selection modifies leaf size across varying climates in conjunction with how climate influences canopy total leaf area. We find that the leaf size‒primary productivity functions based on the Chinese dataset can predict productivity in North America and vice-versa. In addition to advancing understanding of the relationship between a climate-driven trait and ecosystem functioning, our findings suggest that leaf size can also be a promising tool in palaeoecology for scaling from fossil leaves to palaeo-primary productivity of woody ecosystems.
Microbial carbon has recently been highlighted to play a key role in the formation and persistence of soil organic carbon, bearing significant implications for regulating ecosystem carbon stocks under global changes. However, microbial carbon distribution and the link between biomass and necromass components are poorly understood in natural soils, especially at depth. Here, we employ various microbial biomarkers, including phospholipid fatty acids (PLFAs), amino sugars and glycerol dialkyl glycerol tetraethers (GDGTs), to investigate the spatial distribution patterns of microbial biomass and necromass components in the top- (0–10 cm) versus subsoils (30–50 cm) across Chinese temperate grasslands along an aridity gradient. We find that bacterial necromass components are better preserved relative to bacterial biomass in the sub- than topsoil, possibly due to a stronger association of microbial necromass with calcium and/or lower nitrogen competition between plants and microbes at depth in these neutral-to-alkaline soils. As a result, there is a stronger link between bacterial necromass components (especially for core lipid branched GDGTs and muramic acid) and their producers (reflected by intact polar lipid-derived branched GDGTs) in the sub- than topsoil, while such a trend is not observed for fungi- or archaea-derived components. Furthermore, using linear mixed effect model analyses, we find that aridity index best explains the concentration variance of most microbial biomarkers in the topsoil, whereas edaphic properties (i.e., pH and macronutrients) also contribute significantly to their variance in the subsoil. These findings highlight different links between microbial necromass and biomass components and distinct preservation mechanisms for microbial carbon at different soil depths, which is crucial for improved understanding of microbial carbon sequestration potentials at different depths in a changing environment.