Dual functionality of surface plasmon resonance and barrier layer on the photosensing and optical nonlinearity of ZnO nanorod arrays

The dual functionality of plasmonic light harvesting and barrier spacing between Au nanoparticles (NPs) and ZnO nanorod arrays (NRsA) are spotlighted to investigate their impact on the photoconversion and optical nonlinearity in the present study. The passivating Al₂O₃ barrier layer permits high-energy hot electron tunneling and injection from Au to the ZnO NRsA. The structural, vibrational, morphological/elemental, and optical properties of ZnO NRsA/a-Al₂O₃/Au were characterized by X-ray diffraction (XRD), Raman scattering, field emission scanning electron microscopy/energy dispersive X-ray spectroscopy (FE-SEM/EDX), and ultraviolet-visible-near IR (UV-Vis-near IR) absorption, respectively. The optoelectronic and nonlinear optical properties were analyzed by current-voltage measurement and z-scan tests under red laser (655 nm) irradiation, respectively. To highlight the effect of surface plasmon charge transport-based photosensing and photo-harvesting, the irradiated light source is selected to have a photon energy lower than the ZnO bandgap energy and detuning from LSPR. The transfer of photo-induced hot electrons from the Au NPs localized surface plasmon resonance (LSPR) to the ZnO NRsA translates into photocurrent generation in photosensing performance. The reverse saturable absorption process is changed to saturable absorption after intercalating the Al₂O₃ spacing layer into the ZnO NRsA/Au interface. The typical values of the nonlinear refraction index and absorption coefficient are calculated as n₂ = +2.38 × 10^-5 cm² W^-1 and β = -0.17 cm W^-1 for the sandwiched ZnO NRsA/Al₂O₃/Au heterostructure, respectively. The sandwiched ZnO NRsA/amorphous Al₂O₃/Au heterostructure exhibits strong nonresonant optical nonlinearity, which has an excellent figure of merit for optical switching.

Parker Solar Probe Observations of Solar Wind Energetic Proton Beams Produced by Magnetic Reconnection in the Near-Sun Heliospheric Current Sheet

We report observations of reconnection exhausts in the Heliospheric Current Sheet (HCS) during Parker Solar Probe Encounters 08 and 07, at 16 R _s and 20 R _s , respectively. Heliospheric current sheet (HCS) reconnection accelerated protons to almost twice the solar wind speed and increased the proton core energy by a factor of ∼3, due to the Alfvén speed being comparable to the solar wind flow speed at these near-Sun distances. Furthermore, protons were energized to super-thermal energies. During E08, energized protons were found to have leaked out of the exhaust along separatrix field lines, appearing as field-aligned energetic proton beams in a broad region outside the HCS. Concurrent dropouts of strahl electrons, indicating disconnection from the Sun, provide further evidence for the HCS being the source of the beams. Around the HCS in E07, there were also proton beams but without electron strahl dropouts, indicating that their origin was not the local HCS reconnection exhaust.

Psychological consequences of firefighters' working conditions: A Qualitative Study

Introduction: A high-risk job, firefighting involves a wide range of tasks. Given the difficult nature of the job with all the responsibilities included, and in addition to the impending physical injuries, firefighters undergo several emergencies which can endanger their psychological health. Therefore, the present study was conducted to investigate the psychological consequences of firefighters' work conditions. Materials and Methods: The research method was qualitative and phenomenological. Using the purposeful sampling method, 16 firefighters were selected from fire stations across the city of Kerman, Iran; saturation criteria were used in the selection of participants. Data were collected using semi-structured interviews and analyzed using Colaizzi’s seven-step method. In this way, first, the interviews were coded, and then based on the similarity of codes, 4 main categories were extracted.  Results: results showed that persistent stress (caused by the sound of fire alarms and announcement of fire emergencies, trying to make it to the scene on time, worrying about not being on time, and not finding the address of the incidents, complications, and uncertainties of the incidents), sleep problems (these include sleep disturbances, insomnia, difficulty maintaining sleep, startled waking up, somniloquy), negative emotions reminiscent of painful events, and difficulty in establishing good relationships with family members, are the most important psychological consequences that firefighters faced due to their working conditions. Conclusion: Considering the important role of firefighters in providing services in emergencies, the psychological consequences of this job are risk factors that harm the health and the performance of firefighters. Therefore, appropriate measures and planning need to be taken to manage and reduce ongoing stress and improve the quality of firefighters' sleep. To manage and reduce negative emotions and their family problems, appropriate training should be provided.

Comparative effects of Er:YAG laser, and EDTA, MTAD, and QMix irrigants on adhesion of stem cells from the apical papilla to dentin: A scanning electron microscopic study

Background

Dentin conditioning can affect the adhesion of stem cells in endodontic regenerative treatments. This study aimed to assess the effects of the most commonly used endodontic irrigants, namely, ethylenediaminetetraacetic acid (EDTA), MTAD, and QMix in comparison with Er:YAG laser (as a novel modality for root canal disinfection) on the adhesion of stem cells from the apical papilla (SCAPs) to dentin.

Material and Methods

Forty dentin specimens were prepared and subjected to different treatments in 5 groups (n=8) of control, irrigation with EDTA for 1 minute, irrigation with MTAD for 5 minutes, irrigation with QMix for 5 minutes, and Er:YAG laser irradiation. SCAPs were isolated from third molar tooth buds that two-thirds of their roots had formed. The cells were cultured on dentin specimens for 3 days and were counted using scanning electron microscopy (SEM).

Results

MTAD resulted in significantly lower adhesion of cells to dentin compared with other groups (P<0.05). All other modalities induced cell adhesion with no significant difference with each other (P>0.05).

Conclusions

Despite many favorable properties, MTAD cannot serve as an optimal irrigant in endodontic regenerative procedures since it inhibits the adhesion of SCAPs to dentin and impairs an important step in tissue engineering.

Key words:Endodontic Regeneration, Er-YAG laser, MTAD, QMix, EDTA, SCAP, stem cell adhesion.

Parker Solar Probe Enters the Magnetically Dominated Solar Corona

The high temperatures and strong magnetic fields of the solar corona form streams of solar wind that expand through the Solar System into interstellar space. At 09:33 UT on 28 April 2021 Parker Solar Probe entered the magnetized atmosphere of the Sun 13 million km above the photosphere, crossing below the Alfvén critical surface for five hours into plasma in casual contact with the Sun with an Alfvén Mach number of 0.79 and magnetic pressure dominating both ion and electron pressure. The spectrum of turbulence below the Alfvén critical surface is reported. Magnetic mapping suggests the region was a steady flow emerging on rapidly expanding coronal magnetic field lines lying above a pseudostreamer. The sub-Alfvénic nature of the flow may be due to suppressed magnetic reconnection at the base of the pseudostreamer, as evidenced by unusually low densities in this region and the magnetic mapping.

Shear-thinning and self-healing nanohybrid alginate-graphene oxide hydrogel based on guest-host assembly

The study aims to develop a novel nanohybrid shear-thinning hydrogel with fast gelation, and variable mechanical and biological properties. This nanohybrid hydrogel was developed via self-assembly guest-host interaction between β-cyclodextrin modified alginate (host macromere, Alg-CD) and adamantine modified graphene oxide (guest macromere, Ad-GO) and subsequent ionic crosslinking process. We found that the rheological and mechanical properties of hydrogels were controlled via macromere concentration and the host: guest macromere ratio, due to the modulation of crosslinking density and network structure. Noticeably, 12%(1:2) dual-crosslinked hydrogel (2DC12) significantly improved the strength (1.3-folds) and toughness compared to 10%(1:4) dual-crosslinked hydrogel (4DC10). Furthermore, the hydrogel erosion and cytocompatibility relied on the designed parameters. Remarkably, 2DC12 showed less than 20% weight loss after 20 days of incubation in physiological solution and more than 200% cell survival after five days. In conclusion, the nanohybrid Alg-GO hydrogel could be used as an injectable hydrogel for soft tissue engineering applications.

MAVEN observations of the response of Mars to an interplanetary coronal mass ejection

Coupling between the lower and upper atmosphere, combined with loss of gas from the upper atmosphere to space, likely contributed to the thin, cold, dry atmosphere of modern Mars. To help understand ongoing ion loss to space, the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft made comprehensive measurements of the Mars upper atmosphere, ionosphere, and interactions with the Sun and solar wind during an interplanetary coronal mass ejection impact in March 2015. Responses include changes in the bow shock and magnetosheath, formation of widespread diffuse aurora, and enhancement of pick-up ions. Observations and models both show an enhancement in escape rate of ions to space during the event. Ion loss during solar events early in Mars history may have been a major contributor to the long-term evolution of the Mars atmosphere.

Early MAVEN Deep Dip campaign reveals thermosphere and ionosphere variability

The Mars Atmosphere and Volatile Evolution (MAVEN) mission, during the second of its Deep Dip campaigns, made comprehensive measurements of martian thermosphere and ionosphere composition, structure, and variability at altitudes down to ~130 kilometers in the subsolar region. This altitude range contains the diffusively separated upper atmosphere just above the well-mixed atmosphere, the layer of peak extreme ultraviolet heating and primary reservoir for atmospheric escape. In situ measurements of the upper atmosphere reveal previously unmeasured populations of neutral and charged particles, the homopause altitude at approximately 130 kilometers, and an unexpected level of variability both on an orbit-to-orbit basis and within individual orbits. These observations help constrain volatile escape processes controlled by thermosphere and ionosphere structure and variability.

Freeman-Sheldon syndrome: a case report

Freeman-Sheldon syndrome is a rare hereditary disorder characterised by three basic abnormalities, namely microstomia, camptodactyly with ulnar deviation of the fingers, and clubfoot. The majority of these patients have microstomia and dental crowding, making oral hygiene difficult and increasing the risk of caries. Treatment of these patients requires a coordinated effort by a team of specialists, including a paediatrician, an anaesthesiologist, a plastic surgeon, a paediatric dentist, and an orthodontist. Herein, we describe dental problems of a child with Freeman-Sheldon syndrome and the treatment procedures performed.

Subtyping of Clostridium difficile polymerase chain reaction (PCR) ribotype 001 by repetitive extragenic palindromic PCR genomic fingerprinting

Fifty isolates of the most common UK strain of Clostridium difficile [polymerase chain reaction (PCR) ribotype 001] were analysed by three PCR-based typing methods in order to determine genomic diversity within this strain that may form the basis of a subtyping method. The three methods used were repetitive extragenic palindromic elements (REP), conserved repetitive DNA elements (BOX), and enterobacterial repetitive PCR intergenic consensus sequences (ERIC). The performance of each typing method was assessed by comparing powers of discrimination, typeability and reproducibility. All methods had satisfactory levels of typeability and reproducibility as determined by blind-coded repeats, but REP-PCR typing proved to be the most discriminatory method, yielding seven distinct amplicon profiles consisting of up to eight major bands. BOX-PCR generated between two and five major amplicons with four distinct BOX profiles. ERIC-PCR primers, however, could not discriminate between isolates. These results suggest that PCR ribotype 001 is not clonal in nature at present, and that REP-PCR subtyping methods offer promise to further our understanding of the epidemiology of C. difficile PCR ribotype 001 disease in UK hospitals.