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BackgroundFlexible vegetation is an important part of the riverine ecosystem, which can reduce flow velocity, change turbulence structure, and affect the processes of solute transport. Compared with the flow with rigid vegetation, which has been reported in many previous studies, bending of flexible vegetation increases the complexity of the flow–vegetation–solute interactions. In this study, laboratory experiments are carried out to investigate the influence of flexible vegetation on solute transport, and methods for estimating the lateral and longitudinal diffusion coefficients in the rigid vegetated flow are examined for their applications to the flow with flexible vegetation.ResultsThe experimental observations find that vegetation can significantly reduce flow velocity, and the Manning coefficient increases with increasing vegetation density and decreases with inflow discharge. Under all the cases, the vertical peak of the solute concentration moves towards the bottom bed along the flow, and the values of vertical peak concentration longitudinally decreases from the injection point. The lateral diffusion coefficients Dy increase with vegetation density, while the longitudinal diffusion coefficients DL are opposite. Both Dy and DL increase with the inflow discharge. To estimate the Dy and DL in the flow with flexible vegetation, an effective submerged vegetation height considering vegetation bending is incorporated in the methods proposed for flow with rigid vegetation (Lou et al. Environ Sci Eur 32:15, 2020). The modified approach can well predict the diffusion coefficients in the experiments with the relative errors in the range of 5%–12%.ConclusionsThe methods proposed in this study can be used to estimate the lateral and longitudinal diffusion coefficients in flows through both rigid and flexible vegetations using the effective submerged vegetation height.

Fluorescent probes are widely employed to label lipids for the investigation of structural and dynamic properties of model and cell membranes through optical microscopy techniques. Although the effect of tagging a lipid with an organic dye is generally assumed to be negligible, optically modified lipids can nonetheless affect the local lipid structure and, in turn, the lipid lateral mobility. To better assess this potential issue, all-atom (MD) molecular dynamics simulations have been performed to study structural and dynamic effects in a model DOPC membrane in the presence of a standard Rhodamine B-labeled DOPE lipid (RHB) as a function of temperature, i.e., 293 K, 303 K, and 320 K. As the temperature is increased, we observe similar changes in the structural properties of both pure DOPC and RHB-DOPC lipid bilayers: an increase of the area per lipid, a reduction of the membrane thickness and a decrease of lipid order parameters. The partial density profile of the RHB headgroups and their orientation within the lipid bilayer confirm the amphiphilic nature of the RHB fluorescent moiety, which mainly partitions in the DOPC glycerol backbone region at each temperature. Moreover, at all temperatures, our results on lipid lateral diffusion support a non-neutral role of the dye with respect to the unlabeled lipid mobility, thus suggesting important implications for optical microscopy studies of lipid membranes.

Theoretical formulae have shown significant advantages in describing the characteristic geometric scales of the pollutant mixing zone (PMZ) formed by offshore pollutant discharged by a single general form. They, however, fail to predict the influence of the lateral inhomogeneity of the river flow because constant flow velocity and the lateral diffusion coefficient are assumed during the derivation. The realistic flow velocity in a river is fitted by an exponential law in this study and the lateral diffusion coefficient is proposed to have the same form. Similar idea has been used in previous studies on the vertical dispersion of scalar in the lower atmosphere. Pollutant discharged from a steady onshore point source into a wide straight open channel is examined to characterize the concentration taking into consideration of these lateral variations. Theoretical formulae describing the maximum length, maximum width and its corresponding longitudinal position, as well as the area of the PMZ are derived. A non-dimensional standard curve equation for the isoconcentration boundary of PMZ is also obtained. The results show that the shape of the dimensionless standard curve of PMZ depends only on the exponential constants in the exponential laws. The exponential profiles that fit the near-shore velocity give good prediction, while the ones that match the entire lateral range up to the center of the river underpredict the PMZ significantly. These findings are of great importance for practitioners to characterize the geometry of the PMZ in rivers and for water quality modeling.

BackgroundAquatic vegetation has major influence on the local water environment, affecting flow velocities and solute mixing. Extensive research has been conducted on the flow characteristics of vegetated areas, but little is known about solute transport. In this study, Laboratory experiments were carried out to investigate how solute transport is affected by emergent and submerged rigid vegetation.ResultsVegetation greatly reduces the mean velocity, especially within the vegetated region. Near the bottom, the solute concentration is greater in the dense vegetation than in the sparse vegetation. The vertical distribution of the solute concentration decreases rapidly with the relative water depth. Generally, the longitudinal and lateral diffusion coefficients are less affected by denser vegetation, but both coefficients are strongly influenced by the relative water depth (submerged vegetation height).ConclusionsA modified function to estimate the longitudinal diffusion coefficients is proposed under both emergent and submerged vegetation conditions, including cases of variable vegetation height. The key parameters (a’ and b’) for the assessment of the lateral diffusion coefficients are improved considering vegetation height. Results in the present paper can be used as efficient and convenient methods to estimate the longitudinal and lateral diffusion coefficients in flow with rigid vegetation.

Recoverin is a protein involved in the phototransduction cascade by regulating the activity of rhodopsin kinase through a calcium-dependent binding process at the surface of rod outer segment disk membranes. We have investigated the interaction of recoverin with zwitterionic phosphatidylcholine bilayers, the major lipid component of the rod outer segment disk membranes, using both 31P and 19F solid-state nuclear magnetic resonance (NMR) and infrared spectroscopy. In particular, several novel approaches have been used, such as the centerband-only detection of exchange (CODEX) technique to investigate lipid lateral diffusion and 19F NMR to probe the environment of the recoverin myristoyl group. The results reveal that the lipid bilayer organization is not disturbed by recoverin. Non-myristoylated recoverin induces a small increase in lipid hydration that appears to be correlated with an increased lipid lateral diffusion. The thermal stability of recoverin remains similar in the absence or presence of lipids and Ca2+. Fluorine atoms have been strategically introduced at positions 4 or 12 on the myristoyl moiety of recoverin to, respectively, probe its behavior in the interfacial and more hydrophobic regions of the membrane. 19F NMR results allow the observation of the calcium–myristoyl switch, the myristoyl group experiencing two different environments in the absence of Ca2+ and the immobilization of the recoverin myristoyl moiety in phosphatidylcholine membranes in the presence of Ca2+.

Plants achieve mineral ion homeostasis by means of a hydrophobic barrier on endodermal cells called the Casparian strip, which restricts lateral diffusion of ions between the root vascular bundles and the soil. We identified a family of sulfated peptides required for contiguous Casparian strip formation in Arabidopsis roots. These peptide hormones, which we named Casparian strip integrity factor 1 (CIF1) and CIF2, are expressed in the root stele and specifically bind the endodermis-expressed leucine-rich repeat receptor kinase GASSHO1 (GSO1)/SCHENGEN3 and its homolog, GSO2. A mutant devoid of CIF peptides is defective in ion homeostasis in the xylem. CIF genes are environmentally responsive. Casparian strip regulation is not merely a passive process driven by root developmental cues; it also serves as an active strategy to cope with adverse soil conditions.

Artificial water channels are synthetic molecules that aim to mimic the structural and functional features of biological water channels (aquaporins). Here we report on a cluster-forming organic nanoarchitecture, peptide-appended hybrid[4]arene (PAH[4]), as a new class of artificial water channels. Fluorescence experiments and simulations demonstrated that PAH[4]s can form, through lateral diffusion, clusters in lipid membranes that provide synergistic membrane-spanning paths for a rapid and selective water permeation through water-wire networks. Quantitative transport studies revealed that PAH[4]s can transport >109 water molecules per second per molecule, which is comparable to aquaporin water channels. The performance of these channels exceeds the upper bound limit of current desalination membranes by a factor of ~104, as illustrated by the water/NaCl permeability–selectivity trade-off curve. PAH[4]’s unique properties of a high water/solute permselectivity via cooperative water-wire formation could usher in an alternative design paradigm for permeable membrane materials in separations, energy production and barrier applications.Cooperative water wires formed by clustering of artificial water channels enhance membrane permselectivity.

InGaN-based micro-light-emitting diodes have a strong potential as a crucial building block for next-generation displays. However, small-size pixels suffer from efficiency degradations, which increase the power consumption of the display. We demonstrate strategies for epitaxial structure engineering carefully considering the quantum barrier layer and electron blocking layer to alleviate efficiency degradations in low current injection regime by reducing the lateral diffusion of injected carriers via reducing the tunneling rate of electrons through the barrier layer and balanced carrier injection. As a result, the fabricated micro-light-emitting diodes show a high external quantum efficiency of 3.00% at 0.1 A/cm 2 for the pixel size of 10 × 10 μm 2 and a negligible J max EQE shift during size reduction, which is challenging due to the non-radiative recombination at the sidewall. Furthermore, we verify that our epitaxy strategies can result in the relaxation of self-heating of the micro-light-emitting diodes, where the average pixel temperature was effectively reduced. The size-dependent efficiency degradation issues of micro-light-emitting diodes are obstacles for efficient microdisplays development. Here, Baek et al. demonstrate an epitaxial engineering strategy to alleviate the efficiency degradations and achieve low operating temperature of pixels.

To determine diagnostic value of diffusion tensor imaging (DTI) in amyotrophic lateral sclerosis (ALS) patients and investigate the association between DTI and neurofilaments (NFs), including serum and cerebrospinal fluid (CSF) levels of neurofilament light chain (NFL) and phosphorylated neurofilament heavy chain (pNFH). Forty-three clinically diagnosed ALS patients and 32 control subjects without neurological disorders underwent routine MRI (magnetic resonance imaging) and DTI scans. DTI parameters (mean diffusivity [MD] and fractional anisotropy [FA]) at axial levels of internal capsules and cerebral peduncles along the corticospinal tract (CST) were measured. The study compared the differences of DTI parameters between ALS patients and controls using the Mann-Whitney U test. Diagnostic efficacy of each DTI metric was evaluated using the receiver operating characteristic (ROC) curve. NFs (NFL and pNFH levels in serum and CSF) were measured by enzyme-linked immunosorbent assay. Correlation analyses were conducted between DTI parameters and NFs. Capsule-MD and Peduncle-MD in ALS patients were higher than those in controls; whereas Capsule-FA and Peduncle-FA in ALS patients were lower than those in controls (all, p  < 0.05). The area under curve (AUC) was 0.730 for Capsule-FA, 0.828 for Capsule-MD, 0.890 for Peduncle-FA, and 0.896 for Peduncle-MD. Capsule-FA was negatively correlated with CSF-NFL ( r = − 0.813, p  < 0.001), Serum-NFL ( r = − 0.493, p  = 0.001), CSF-pNFH ( r = − 0.637, p  < 0.001), and Serum-pNFH ( r = − 0.672, p  < 0.001); Peduncle-FA negatively with CSF-NFL ( r = − 0.562, p  < 0.001), CSF-pNFH ( r = − 0.506, p  = 0.001), and Serum-pNFH ( r = − 0.488, p  = 0.001); Peduncle-MD positively with CSF-NFL ( r  = 0.516, p  < 0.001), CSF-pNFH ( r  = 0.494, p  = 0.001). DTI had superior performance in identifying ALS patients and could serve as a reliable predictor. DTI parameters related to neurofilament markers, and Capsule-FA may become a robust surrogate biomarker indicating disease severity and progression rate for ALS patients.

Background and Purpose To date, no previous studies have used multishell diffusion MRI to identify striatal microstructural damage in vivo in amyotrophic lateral sclerosis (ALS) patients. Thus, in the present study, we aimed to comprehensively explore connectivity‐based selective striatal subregion microstructural damage in sporadic ALS patients and its associations with motor disability, cognitive deficits, and serum biomarkers. Methods In this retrospective study, 79 ALS patients and 53 healthy controls (HCs) who underwent clinical assessment, serum neurofilament light (NfL) measurement, genetic testing, and multishell diffusion MRI scanning were included. Using a probabilistic tractography approach, the striatum was segmented into six subregions based on their corticostriatal connectivity. Three neurite orientation dispersion and density imaging (NODDI) parameters, the neurite density index (NDI), orientation dispersion index (ODI), and isotropic volume fraction (ISO), of the connectivity‐based striatal subregions were measured. Results Compared with HCs, ALS patients had a significantly lower NDI in the bilateral motor and right frontal subregions, a significantly lower ODI in the right motor and frontal subregions, and a significantly higher ISO in the bilateral motor and frontal subregions of the striatum after familywise error (p < 0.05). Moreover, striatal subregion microstructural damage was significantly correlated with motor disabilities, cognitive deficits, and serum NfL levels in ALS patients (p = 0.020–0.002). Conclusions Our study provides clear evidence demonstrating that connectivity‐based selective striatal subregion microstructural damage is a definite feature of sporadic ALS patients and suggesting that striatal damage may play an important role in motor disability and cognitive deficits in ALS patients.