Water is a limited resource and is likely to become even more restricted with climate change. The aim of this study was to evaluate the effect of humic acid (HA) applications on photosynthesis ...efficiency of rapeseed plants under different watering conditions. Water stress strongly increased electron transport flux, probability that trapped excitation can move an electron into the electron transport chain beyond Q
A
, and quantum yield of reduction of end electron acceptors at the PSI acceptor side. Application of HA decreased the values of these parameters to be similar to those of non-stress conditions. We found that, the application of HA improved plants net photosynthesis under water stress
via
increasing the rate of gas exchange and electron transport flux in plants.
In the present work, the interaction of hydrogen molecules with defective graphene structures doped by transition metal (TM) atoms is investigated by using first principles density functional theory ...(DFT). Defective graphene structures include Stone–Wales (SW), 585 and 555-777 and transition metals include early TMs, i.e. scandium (Sc), titanium (Ti) and vanadium (V). It is found that in comparison with the pristine graphene, presence of defects significantly enhances the metal binding. Among three defects, 585 divacancy leads to the strongest binding between graphene and metal. Hydrogen adsorption is then evaluated by sequential addition of hydrogen molecules to the system. The results reveal that in comparison with other structures, 555-777 defective structure doped by Sc has the maximum capacity for hydrogen molecules. Also it is indicated that none of hydrogen molecules were dissociated during relaxation, indicating that all hydrogen molecules are accessible for reversible storage. Moreover, it is found that binding energies for adsorption of hydrogen molecules over 555-777/ Sc system are in the favorable range of 0.2–0.4eV/H2.
•Interaction of H2 molecules with defective graphene doped TM atoms was studied.•585 divacancy-TM had the strongest binding energy compared to SW and 555-777.•555-777 structure doped by Sc had the maximum capacity for hydrogen molecules.•H2 binding energies on 555-777/Sc system were in the favorable range of 0.2–0.4eV.
► ZnO nanoparticles were synthesized at low temperature by a chemical method. ► The samples (ZnO nanoparticles) were annealed at different temperatures; 200, 400 and 600°C. ► The as synthesized ...sample has revealed a strong emission peak in visible region. ► The yellow emission intensity is strongly decreased, but the green emission is revealed by annealing. ► A slight red shift can be found in the Eg with increasing the annealing temperature.
ZnO nanoparticles were synthesized by a simple chemical precipitation method at 0°C and annealed in air at temperatures of 200, 400 and 600°C. Effect of annealing temperature on the optical properties were characterized by the UV–Vis and photoluminescence (PL) spectroscopy. The PL spectra of as prepared ZnO nanoparticles exhibits a narrow UV and a broad yellow emission peaks which are related to defect levels in the band gap. With the annealing temperature increasing, the intensity of yellow emission is strongly decreased, whereas the green emission is revealed. In addition, it was found that, there is a slight red shift in the UV absorption peak and a blue shift in the visible emission peak when the annealing temperature increases.
For effective treatment, induced pluripotent stem cell (iPSC)‐retinal pigment epithelium (RPE) must recapitulate the physiology of native human RPE cells. A set of physiologically relevant functional ...assays that assess the polarized functional activity and maturation state of the intact RPE monolayer is provided. The study data show that donor‐to‐donor variability exceeds the tissue‐to‐tissue variability for a given donor and provides, for the first time, criteria necessary to identify iPSC‐RPE cells most suitable for clinical application.
Acknowledgements
Induced pluripotent stem cells (iPSCs) can be efficiently differentiated into retinal pigment epithelium (RPE), offering the possibility of autologous cell replacement therapy for retinal degeneration stemming from RPE loss. The generation and maintenance of epithelial apical‐basolateral polarity is fundamental for iPSC‐derived RPE (iPSC‐RPE) to recapitulate native RPE structure and function. Presently, no criteria have been established to determine clonal or donor based heterogeneity in the polarization and maturation state of iPSC‐RPE. We provide an unbiased structural, molecular, and physiological evaluation of 15 iPSC‐RPE that have been derived from distinct tissues from several different donors. We assessed the intact RPE monolayer in terms of an ATP‐dependent signaling pathway that drives critical aspects of RPE function, including calcium and electrophysiological responses, as well as steady‐state fluid transport. These responses have key in vivo counterparts that together help determine the homeostasis of the distal retina. We characterized the donor and clonal variation and found that iPSC‐RPE function was more significantly affected by the genetic differences between different donors than the epigenetic differences associated with different starting tissues. This study provides a reference dataset to authenticate genetically diverse iPSC‐RPE derived for clinical applications.
The retinal pigment epithelium (RPE) is essential for maintaining visual function. RPE derived from human induced pluripotent stem cells (iPSC‐RPE) offer a promising cell‐based transplantation therapy for slowing or rescuing RPE‐induced visual function loss. For effective treatment, iPSC‐RPE must recapitulate the physiology of native human RPE. A set of physiologically relevant functional assays are provided that assess the polarized functional activity and maturation state of the intact RPE monolayer. The present data show that donor‐to‐donor variability exceeds the tissue‐to‐tissue variability for a given donor and provides, for the first time, criteria necessary to identify iPSC‐RPE most suitable for clinical application.
We report the use of silver (Ag)-modified carbon and Ag ultramicroelectrodes (UMEs) for electrochemical detection of nitrate. We investigated several methods for electrodeposition of Ag; our results ...show that the addition of a complexation agent (ammonium sulfate) in the Ag deposition solution is necessary for electrodeposition of nanostructured Ag that adheres well to the electrode. The electrodeposited Ag on both types of electrodes has branch-like structures that are well-suited for electrocatalytic reduction of nitrate. The use of UMEs is advantageous; the sigmoidal-shaped cyclic voltammogram allows for sensitive detection of nitrate by reducing the capacitive current, as well as enabling easy quantification of the nitrate reduction current. Both cyclic voltammetry and chronoamperometry were used to characterize the electrodes; and independent of the electrochemical interrogation technique, both UMEs were found to have a wide linear dynamic range (4–1000 μM) and a low limit of detection (3.2–5.1 μM). More importantly, they are reusable up to ∼100 interrogation cycles and are selective enough to be used for direct detection of nitrate in a synthetic aquifer sample without any sample pretreatment and/or pH adjustment.
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•Ag-modified carbon and Ag UMEs are suitable for electrocatalytic nitrate reduction.•Addition of (NH4)2SO4 in the plating solution is needed for optimal Ag deposition.•Both Ag-modified UMEs have a similar linear dynamic range and limit of detection.•Both Ag-modified UMEs are reusable up to ∼100 interrogation cycles.•Both Ag-modified UMEs can be used to detect nitrate in a synthetic aquifer sample.
ZnO:Mn nanoparticles with various Mn concentrations (1-7%) were synthesized by a simple chemical method at low temperature. Structural and optical properties of as synthesized samples were ...investigated by X-ray diffraction (XRD), UV-vis absorbance, and photoluminescence (PL) spectrophotometers, respectively. XRD patterns of the ZnO:Mn nanocrystals indicate that in low Mn concentrations (1 and 3%), the ZnMn
2
O
4
nanoparticles are formed, whereas in high Mn concentrations (5 and 7%), more Mn atoms replace Zn atoms in crystalline lattice, so that Mn
3
O
4
is formed. It is also found that the size of the ZnO:Mn nanocrystals increases from 7.82 to 76.07 nm with increasing Mn concentration from 1 to 7%. Band gap energy of the samples, calculated by extrapolation of (αhν)
2
versus hν curves, shows a decrease in band gap with increasing the Mn concentration from 1 to 7%. The size of nanoparticles calculated by effective mass approximation model is nearly in accordance with the one calculated by Scherrer formula. The PL spectra of low Mn concentration ZnO:Mn nanoparticles indicate a weak green emission which vanishes in highly Mn concentrated ZnO:Mn samples.
We report the design of an electrochemical sensor capable of detecting levofloxacin (LEVX) in complex biological samples. This detection strategy is simple, fast, and does not require sample ...pretreatment or electrode modification. Unlike previously developed electrochemical LEVX sensors that require direct oxidation of LEVX, the sensing mechanism is based on the complexation reactions between LEVX and iron(III), resulting in a concentration‐dependent decrease in the iron(III) reduction peak current and a shift in the peak potential. These changes are presumably attributed to the decrease in the concentration of uncomplexed Fe(III) in the solution. The concentration‐dependent change in both the current and potential can be used for quantification of LEVX in various samples, including 50 % synthetic urine and 25 % synthetic human saliva. The limit of detection was estimated to be in the range of 1.5 to 2.3 μM, concentrations that are much lower than the concentration of LEVX found in urine and saliva samples of patients administered this drug for conditions such as urinary tract infection. With further optimization, this sensing strategy could find applications in clinical pharmacokinetic studies.
α-tocopherol is a vitamin E isoform with potent antioxidant activity, while the γ-tocopherol isoform of vitamin E exerts more pro-inflammatory effects. In maternal–fetal environments, increased ...plasma α-tocopherol concentrations are associated with positive birth outcomes, while higher γ-tocopherol concentrations are linked with negative pregnancy outcomes. However, little is known about tocopherol concentrations in placental tissue and their role in modulating placental oxidative stress, a process that is implicated in many complications of pregnancy. The objectives of this research are to evaluate the concentrations of α- and γ-tocopherol in placental tissue and assess relationships with maternal and umbilical cord plasma concentrations. A total of 82 mother–infant dyads were enrolled at the time of delivery, and maternal and umbilical cord blood samples and placenta samples were collected. α- and γ-tocopherol concentrations in these samples were analyzed by high-performance liquid chromatography (HPLC). γ-tocopherol concentrations demonstrated significant, positive correlations among all sample types (p-values < 0.001). Placental tissue had a significantly lower ratio of α:γ-tocopherol concentrations when compared to maternal plasma and umbilical cord plasma (2.9 vs. 9.9 vs. 13.2, respectively; p < 0.001). Additional research should explore possible mechanisms for tocopherol storage and transfer in placental tissue and assess relationships between placental tocopherol concentrations and measures of maternal–fetal oxidative stress and clinical outcomes of pregnancy.
We report the design and fabrication of a DNA-based electrochemical sensor for detection of glutathione. Sensor signaling relies on glutathione's ability to chelate mercury Hg(II), displacing it from ...the thymine-Hg(II)-thymine complex formed between the surface-immobilized DNA probes. Our results show that this sensor is sensitive and selective enough to be employed in saliva.
In this research, the convective heat transfer coefficients of water-based FMWNT nanofluid have been measured under both laminar and turbulent regimes flowing through a uniformly heated horizontal ...tube in entrance region. For the first time, we have compared effective parameters to measure the convective heat transfer coefficients for functionalized MWNT suspensions such as Re, mass fraction and temperature, altogether in entrance region. The experimental results indicate that the convective heat transfer coefficient of these nanofluids increases by up to 33–40% at a concentration of 0.25
wt.% compared with that of pure water in laminar and turbulent flows respectively and 20
°C.
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