Suprathermal ion composition associated with corotating interaction regions (CIRs) exhibited a solar cycle variation during solar cycle 23 and the beginning of solar cycle 24. However, it is unclear ...if this variation would remain when considering all of solar cycle 24, or whether the variations in the CIR-associated suprathermal ion composition would change. Using 20 yr of Advanced Composition Explorer observations (1998-2018), we present a comparison of the suprathermal ion compositions for solar cycles 23 and 24. The energetic particle content for the two solar cycles is found to be remarkably similar. The observed solar cycle variations in 0.32-0.45 MeV/nuc Fe/O previously observed for solar cycle 23 was seen to be largely repeated in solar cycle 24, both in solar cycle phase and magnitude. A small enhancement in CIR-associated Fe/O during the declining phase was observed for both solar cycles. The CIR event-averaged intensities of Fe and O were also found to have a slight solar cycle dependence, with the Fe/O ratio being more closely bound to the intensity of Fe ions. Additionally, the elemental abundance versus O ratios compared to the Fe/C ratios were found to follow the same trends for both solar cycles, with high Fe/C ratio events occurring mostly during solar maximum.
Developing controlled platforms for plasmon-driven chemistry is of great importance in catalytic reactions at the nanoscale. We report anion radical formation for five bipyridyl complexes of varying ...degrees of electron affinity utilizing optically focused intraband (594 nm) and interband (532 nm) pump excitation of single gold nanoparticles. The surface-enhanced Raman scattering (SERS) of anion radicals for the five nonresonant adsorbed molecules, 2,2′-bipyridine (22BPY), 4,4′-bipyridine (44BPY), trans-1,2-bis(4-pyridyl)ethylene (BPE), 1,2-bis(4-pyridyl)acetylene (BPA), and 1,2-bis(4-pyridyl)ethane (BPEt), were detected using localized surface-plasmon resonance (LSPR) excitation with 785 nm. The electron affinity of the five bipyridyl complexes were determined using electrochemistry. Molecules with low electron affinity experienced higher instances of radical anion formation under a plasmon-coupled intraband electron transfer excitation (594 nm), whereas molecules with high electron affinity showed a preference for anion radical formation under direct interband electron transfer excitation (532 nm). The lowest unoccupied molecular orbital (LUMO) energy levels for low electron affinity surface-bound molecules (22BPY, BPEt) are on average ∼0.43 eV higher than high electron affinity surface-bound molecules (BPA, BPE, 44BPY), as calculated using time-dependent density functional theory, elucidating the importance of plasmon coupling to energy levels that facilitate charge transfer pathways. We also show the ability to “activate” high versus low electron affinity single nanoparticles with the choice of pump excitation wavelength. The findings show the complex interplay between molecular electron affinity, orbital overlap with the density of states of the plasmonic metal, and excitation energetics of the pump laser wavelength. Potential applications of this work include enhanced control over molecular scale catalysis, biosensor design, and solar energy capture.
Diabetic retinopathy (DR), a major microvascular complication of diabetes, leads to retinal vascular leakage, neuronal dysfunction, and apoptosis within the retina. In this study, we combined STZ ...with whole-body hypoxia (10% O
) for quicker induction of early-stage retinopathy in C57BL/6 mice. We also compared the effects of a high glucose condition combined with hypoxia (1% O
) to a low glucose condition by using retinal pigment epithelial (RPE) cells, which are a crucial component of the outer blood-retinal barrier and the damage is related to retinopathy. In the retina of DM/hypoxic C57BL/6 mice, abnormal a-wave and b-wave activity, yellowish-white spots, hyperfluorescence, and reduced retinal thickness were found using electroretinography (ERG), fundus photography (FP), fundus fluorescein angiography (FFA), and optical coherence tomography (OCT). Shikonin dose-dependently (0.5-50 mg/kg, per os) prevented DM/hypoxia-induced lesions. In eye tissue, administration of shikonin also attenuated DM/hypoxia-induced pre-apoptotic protein BAX expression as well as the production of inflammatory proteins cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS). We also demonstrated that shikonin administration rescues high glucose/hypoxia (1% O
)-induced inflammation, decreased junction protein expression, and permeability in RPE cells. These results indicate that shikonin treatment may prevent the loss of vision associated with DR.
Incorporating organic semiconducting spacer cations into layered lead halide perovskite structures provides a powerful approach to mitigate the typical strong dielectric and quantum confinement ...effects by inducing charge-transfer between the organic and inorganic layers. Herein we report the synthesis and characterization of thin films of novel DJ-phase organic-inorganic layered perovskite semiconductors using a naphthalene diimide (NDI) based divalent spacer cation, which is shown to accept photogenerated electrons from the inorganic layer. With alkyl chain lengths of 6 carbons, an NDI-based thin film exhibited electron mobility (based on space charge-limited current for quasi-layered 〈
n
〉 = 5 material) was found to be as high as 0.03 cm
2
V
−1
s
−1
with no observable trap-filling region suggesting trap passivation by the NDI spacer cation.
An electron-accepting spacer di-cation based on naphthalene diimide is incorporated into layered and quasi-layered perovskite structure, and the effect of the resulting type II heterostructure on the optoelectronic structure is investigated.
Owing to human activities, a large number of organic chemicals, including petroleum products, industrial solvents, pesticides, herbicides (including atrazine ATR), and pharmaceuticals, contaminate ...soil and aquatic environments. Remediation of these pollutants by conventional approaches is both technically and economically challenging.
endospores are highly resistant to most physical assaults and are capable of long-term persistence in soil. Spores can be engineered to express, on their surface, important enzymes for bioremediation purposes. We have developed a
spore platform system that can display a high density of proteins on the spore surface. The spore surface-tethered enzymes exhibit enhanced activity and stability relative to free enzymes in soil and water environments. In this study, we evaluated a
spore display platform as a bioremediation tool against ATR. The
sp. strain ADP
determinant, an ATR chlorohydrolase important to the detoxification of ATR, was expressed as a fusion protein linked to the attachment domain of the BclA spore surface nap layer protein and expressed in
Spores from this strain are decorated with AtzA N-terminally linked on the surface of the spores. The recombinant spores were assayed for ATR detoxification in liquid and soil environments, and enzyme kinetics and stability were assessed. We successfully demonstrated the utility of this spore-based enzyme display system to detoxify ATR in water and laboratory soil samples.
Atrazine is one of the most widely applied herbicides in the U.S. midwestern states. The long environmental half-life of atrazine has contributed to the contamination of surface water and groundwater by atrazine and its chlorinated metabolites. The toxic properties of ATR have raised public health and ecological concerns. However, remediation of ATR by conventional approaches has proven to be costly and inefficient. We developed a novel
spore platform system that is capable of long-term persistence in soil and can be engineered to surface express a high density of enzymes useful for bioremediation purposes. The enzymes are stably attached to the surface of the spore exosporium layer. The spore-based system will likely prove useful for remediation of other environmental pollutants as well.
Vision is critical for children's development. However, prevalence of visual impairment (VI) is high in students with special educational needs (SEN). Other than VI, SEN students are prone to having ...functional deficits. Whether visual problems relate to these functional deficits is unclear. This study aimed to assess the impact of vision on visual processing functions and balance in SEN students through a community service.
Visual acuity (VA) and contrast sensitivity were measured in a total of 104 (aged 14.3±4.3) SEN students as the visual outcomes, followed by retinoscopy. Visual processing function assessment included facial expression recognition by card matching examiner's facial expression matching, and visual orientation recognition. Dynamic balance, by Timed Up and Go test, and static standing balance (postural sway in double-legged standing with feet-together and tandem-stance for open-eye and closed-eye conditions) were assessed. Static balance was presented in terms of the maximal medial-lateral and antero-posterior sways.
Of the 104 students, 62 (59.6%) were classified as visually impaired according to WHO classification of visual impairment based on presenting distance acuity. Ocular problems (e.g. optic nerve anomaly, uncorrected/ under-corrected refractive errors) and neurological anomalies were the major causes of vision loss. VA was positively associated with visual processing functions (all p ≤ 0.01), as SEN students with better vision tended to perform better in visual orientation and facial expression recognition tasks, as well as dynamic balance function (p = 0.04). For the static balance, postural sway and VA showed a positive relationship under open-eye and tandem stance conditions. However, the relationship between postural sway and VA became negative under closed-eye and tandem stance conditions.
This study found a high prevalence of SEN students with visual impairment, in which many of them were undetected. Optometric examination is important to improve their visual function to minimize the effect of vision on functional performance. Vision is critical in visual processing as well as playing an important role in maintaining balance in SEN students.
Several series of large dipolarization events are documented from magnetic field observations in Mercury's magnetotail made by the MESSENGER spacecraft. The dipolarizations are identified by a rapid ...(∼1 s) increase in the northward component of the magnetic field, followed by a slower return (∼10 s) to pre‐onset values. The changes in field strength during an event frequently reach 40 nT or higher, equivalent to an increase in the total magnetic field magnitude by a factor of ∼4 or more. The presence of spatially constrained dipolarizations at Mercury provides a key to understanding the magnetic substorm process in a new parameter regime: the dipolarization timescale, which is shorter than at Earth, is suspected to lead to efficient non‐adiabatic heating of the plasma sheet proton population, and the high recurrence rate of the structures is similar to that frequently observed for flux ropes and traveling compression regions in Mercury's magnetotail. The relatively short lifetime of the events is attributed to the lack of steady field‐aligned current systems at Mercury.
Key Points
Dipolarizations signatures are observed in Mercury's magnetotail
The dipolarization regions are determined to be of limited cross‐tail scale size
The implications for field‐aligned currents and particle heating are discussed
Black walnut (
L.) is one of the most economically valuable hardwood species and a high value tree for edible nut production in the United States. Although consumption of black walnut has been linked ...to multiple health-promoting effects (e.g., antioxidant, antimicrobial, anti-inflammatory), the bioactive compounds have not been systematically characterized. In addition, the associations between different black walnut cultivars and their health-promoting compounds have not been well established. In this study, the kernels of twenty-two black walnut cultivars selected for nut production by the University of Missouri Center for Agroforestry (Columbia, MO, USA) were evaluated for their antibacterial activities using agar-well diffusion assay. Among the selected cultivars, four black walnut cultivars (i.e., Mystry, Surprise, D.34, and A.36) exhibited antibacterial activity against a Gram-positive bacterium (
), whereas other cultivars showed no effect on the inhibition of this bacterium. The antibacterial compounds showing the strongest activity were isolated with bioassay-guided purification and identified using a metabolomics approach. Six antibacterial bioactive compounds responsible for antimicrobial activity were successfully identified. Glansreginin A, azelaic acid, quercetin, and eriodictyol-7-
-glucoside are novel antibacterial compounds identified in the kernels of black walnuts. The metabolomics approach provides a simple and cost-effective tool for bioactive compound identification.
Understanding the Surfaces of Nanodiamonds Paci, Jeffrey T; Man, Han B; Saha, Biswajit ...
Journal of physical chemistry. C,
08/2013, Letnik:
117, Številka:
33
Journal Article
Recenzirano
Functional groups and their associated charges are responsible for the binding and release of molecules from the surfaces of particles in nanodiamond colloids. In this work, we describe a combined ...set of experimental and computational techniques that are used to characterize these functional groups quantitatively. The surfaces of the particles examined during this study are amphoteric, as one would expect for surfaces made of carbon, with high concentrations of phenols, pyrones, and sulfonic acid groups; the average 50-nm-diameter nanodiamond aggregate has approximately 22000 phenols, 7000 pyrones, and 9000 sulfonic acids. The aggregates also have at least 2000 fixed positive charges, stabilized within pyrones and/or chromenes. No evidence for a significant concentration of carboxylic acid groups was found, although some are probably present. Hydroxyl and epoxide groups are present on some areas of the surfaces. The surfaces are graphitized, so the presence of phenols and pyrones is not surprising because such groups are common on graphitic surfaces. The sulfonic acid is due to the sulfuric acid treatment used to remove amorphous carbon and graphite during particle cleaning. The fixed charges are also due to the cleaning procedure that includes the use of KMnO4 with the sulfuric acid. Based on titration and zeta potential experiments, elemental and particle size analyses, and modeling using semiempirical quantum mechanics, a model is proposed for the types and concentrations of surface groups. The modeling shows how functional groups form during the bead milling and cleaning used in the preparation of the colloid. It also shows that the pK a associated with the phenols and pyrones that are formed (pK a = 7.6–10.0) is consistent with that predicted using titration experiments (pK a ≥ 7.3). The positive surface potential means that the latter pK a value is significantly larger than a Henderson–Hasselbalch-based estimate. The model is shown to be useful in explaining a number of recent experiments in which nanodiamonds were used to bind and release therapeutic drug and polymer molecules.
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