Nitrate formation mechanisms causing high concentration of PM2.5 in a residential city with low anthropogenic emissions during cold season.

During the cold season in South Korea, NO3- concentrations are known to significantly increase, often causing PM2.5 to exceed air quality standards. This study investigated the formation mechanisms of NO3- in a suburban area with low anthropogenic emissions. The average PM2.5 was 25.3 µg m-3, with NO3- identified as the largest contributor. Ammonium-rich conditions prevailed throughout the study period, coupled with low atmospheric temperature facilitating the transfer of gaseous HNO3 into the particulate phase. This result indicates that the formation of HNO3 played a crucial role in determining particulate NO3- concentration. Nocturnal increases in NO3- were observed alongside increasing ozone (O3) and relative humidity (RH), emphasizing the significance of heterogeneous reactions involving N2O5. NO3- concentrations at the study site were notably higher than in Seoul, the upwind metropolitan area, during a high concentration episode. This difference could potentially attributed to lower local NO concentrations, which enhanced the reaction between O3 and NO2, to produce NO3 radicals. High concentrations of Cl- and dust were also identified as contributors to the elevated NO3- concentrations.

Cervical spine reconstruction after total vertebrectomy using customized three-dimensional-printed implants in dogs.

BACKGROUND: Sufficient surgical resection is necessary for effective tumor control, but is usually limited for vertebral tumors, especially in the cervical spine in small animal neurosurgery. OBJECTIVE: To evaluate the primary stability and safety of customized three-dimensional (3D)-printed implants for cervical spine reconstruction after total vertebrectomy. METHODS: Customized guides and implants were designed based on computed tomography (CT) imaging of five beagle cadavers and were 3D-printed. They were used to reconstruct C5 after total vertebrectomy. Postoperative CT images were obtained to evaluate the safety and accuracy of screw positioning. After harvesting 10 vertebral specimens (C3-C7) from intact (group A) and implanted spines (group B), implant stability was analyzed using a 4-point bending test comparing with groups A and C (reconstituted with plate and pins/polymethylmethacrylate after testing in Group A). RESULTS: All customized implants were applied without gross neurovascular damage. In addition, 90% of the screws were in a safe area, with 7.5% in grade 1 (< 1.3 mm) and 2.5% in grade 2 (> 1.3 mm). The mean entry point and angular deviations were 0.81 ± 0.43 mm and 6.50 ± 5.11°, respectively. Groups B and C significantly decreased the range of motion (ROM) in C3-C7 compared with intact spines (p = 0.033, and 0.018). Both groups reduced overall ROM and neutral zone in C4-C6, but only group B showed significance (p = 0.005, and 0.027). CONCLUSION: Customized 3D-printed implants could safely and accurately replace a cervical vertebra in dog cadavers while providing primary stability.

Three-dimensional-printed patient-specific guides for tibial deformity correction in small-breed dogs.

OBJECTIVE: To describe the use of patient-specific 3-D-printed osteotomy, reduction, and compression guides for tibial closing wedge osteotomy in small-breed dogs. ANIMALS: 6 dogs with unilateral tibial deformities. METHODS: Six small-breed dogs with 1 or a combination of tibial deformities, including excessive tibial plateau angle, valgus, and torsion, were scheduled to undergo tibial closing wedge osteotomy using patient-specific 3-D-printed osteotomy, reduction, and compression guides. The location and orientation of the wedge osteotomy were determined based on CT data using computer-aided design software. After the tibial deformities were corrected, postoperative CT or radiographs were obtained to compare the achieved tibial limb angles with the planned angles. Clinical evaluation and radiographic follow-up were performed on all dogs. RESULTS: Guides were successfully positioned at each specific location, and osteotomies were performed without radiation exposure or observer assistance in all dogs. Tibial deformities were corrected with angular errors of 1.8 ± 1.4°, 2.3 ± 2.1°, and 2.6 ± 1.3° in the sagittal, frontal, and transverse planes, respectively. Mild complications resolved within 1 month in 3 dogs, and revision surgery was not required. Five dogs improved to the normal gait (mean, 14.8 ± 6.6 weeks), and 1 dog recovered a satisfactory gait 24 weeks after surgery. All limbs healed 14 ± 4.7 weeks after surgery. CLINICAL RELEVANCE: Patient-specific 3-D-printed osteotomy, reduction, and compression guides can provide effective assistance allowing accurate correction of tibial deformities. Their use yields good clinical outcomes in small-breed dogs.

Optical Transitions of a Single Nodal Ring in SrAs_{3}: Radially and Axially Resolved Characterization.

SrAs_{3} is a unique nodal-line semimetal that contains only a single nodal ring in the Brillouin zone, uninterrupted by any trivial bands near the Fermi energy. We performed axis-resolved optical reflection measurements on SrAs_{3} and observed that the optical conductivity exhibits flat absorption up to 129 meV in both the radial and axial directions, confirming the robustness of the universal power-law behavior of the nodal ring. The axis-resolved optical conductivity, in combination with theoretical calculations, further reveals fundamental properties beyond the flat absorption, including the overlap energy of the topological bands, the spin-orbit coupling gap along the nodal ring, and the geometric properties of the nodal ring such as the average ring radius, ring ellipticity, and velocity anisotropy. In addition, our temperature-dependent measurements revealed a spectral weight transfer between intraband and interband transitions, indicating a possible violation of the optical sum rule within the measured energy range.

An Eye Tracking Based Framework for Safety Improvement of Offshore Operations.

Offshore drilling operations consist of complex and high-risk processes. Lack of situational awareness in drilling operations has become an important human factor issue that causes safety accidents. Prolonged work shifts and fatigue are some of the crucial issues that impact performance. Eye tracking technology can be used to distinguish the degree of awareness or alertness of participants that might be related to fatigue or onsite distractions. Oculomotor activity can be used to obtain visual cues that can quantify the drilling operators' situational awareness that might enable us to develop warning alarms to alert the driller. Such systems can help reduce accidents and save non-productive time. In this paper, eye movement char-acteristics were investigated to differentiate the situational awareness between a representa-tive expert and a group of novices using a scenario-based Virtual Reality Drilling Simulator. Significant visual oculomotor activity differences were identified between the expert and the novices that indicate an eye-tracking based system can detect the distraction and alert-ness exhibited by the workers. Results show promise on developing a framework which implements a real-time eye tracking technology in various drilling operations at drilling rigs and Real Time Operation Centers to improve process safety.

The Protective Effects of Human Embryonic Stem Cell-Derived Mesenchymal Stem Cells in Noise-Induced Hearing Loss of Rats.

A few prior animal studies have suggested the transplantation or protective effects of mesenchymal stem cells (MSCs) in noise-induced hearing loss. This study intended to evaluate the fates of administered MSCs in the inner ears and the otoprotective effects of MSCs in the noise-induced hearing loss of rats. Human embryonic stem cell-derived MSCs (ES-MSCs) were systematically administered via the tail vein in adult rats. Eight-week-old Sprague-Dawley rats were randomly allocated to the control (n = 8), ES-MSC (n = 4), noise (n = 8), and ES-MSC+noise (n = 10) groups. In ES-MSC and ES-MSC+noise rats, 5 × 105 ES-MSCs were injected via the tail vein. In noise and ES-MSC+noise rats, broadband noise with 115 dB SPL was exposed for 3 h daily for 5 days. The hearing levels were measured using auditory brainstem response (ABR) at 4, 8, 16, and 32 kHz. Cochlear histology was examined using H&E staining and cochlear whole mount immunofluorescence. The presence of human DNA was examined using Sry PCR, and the presence of human cytoplasmic protein was examined using STEM121 immunofluorescence staining. The protein expression levels of heat shock protein 70 (HSP70), apoptosis-inducing factor (AIF), poly (ADP-ribose) (PAR), PAR polymerase (PARP), caspase 3, and cleaved caspase 3 were estimated. The ES-MSC rats did not show changes in ABR thresholds following the administration of ES-MSCs. The ES-MSC+ noise rats demonstrated lower ABR thresholds at 4, 8, and 16 kHz than the noise rats. Cochlear spiral ganglial cells and outer hair cells were more preserved in the ES-MSC+ noise rats than in the noise rats. The Sry PCR bands were highly detected in lung tissue and less in cochlear tissue of ES-MSC+noise rats. Only a few STEM121-positivities were observed in the spiral ganglial cell area of ES-MSC and ES-MSC+noise rats. The protein levels of AIF, PAR, PARP, caspase 3, and cleaved caspase 3 were lower in the ES-MSC+noise rats than in the noise rats. The systemic injection of ES-MSCs preserved hearing levels and attenuated parthanatos and apoptosis in rats with noise-induced hearing loss. In addition, a tiny number of transplanted ES-MSCs were observed in the spiral ganglial areas.

Differential Expression of miRNAs and Their Predicted Target Pathways in Cochlear Nucleus Following Chronic Noise Exposure in Rats.

Several recent preclinical studies have reported that dynamic changes in miRNA expression contribute to hearing function. This study aims to investigate miRNA expression changes in the cochlear nuclei (CN) of rats following chronic noise exposure. Eight-week-old rats (n = 14) were exposed to noise for 4 weeks. The control rats (n = 14) were raised under identical conditions without noise. Two months after noise exposure, the auditory brainstem response (ABR) was examined, and the cochlea and CN were harvested. In the CN, the expression levels of arc, neurocan, and brevican were measured (n = 6 per group). Furthermore, the expression levels of miRNAs and their predicted target genes were measured in the CN (n = 8 per group). ABR thresholds were elevated after 4 weeks of noise exposure, which were maintained for 3 months. In CN, the protein expression of arc and brevican was higher in the noise-exposed group than in the control group (0.95 [standard deviation (SD) = 0.53] vs. 3.19 [SD = 1.00], p < 0.001 for arc and 1.02 [SD = 0.10] vs. 1.66 [SD = 0.24], p < 0.001 for brevican). The noise-exposed rats exhibited lower expression levels of miR-758-5p, miR-15b-5p, miR-212-3p, miR-199a-5p, and miR-134-3p than the control rats (all p < 0.001). The AMPK signaling pathway was predicted to be regulated by these miRNAs. The predicted target genes AKT3, SIRT1, and PRKAA1 were highly expressed in noise-exposed rats. In CN of noise-exposed rats, the miRNAs of miR-758-5p, miR-15b-5p, miR-212-3p, miR-199a-5p, and miR-134-3p were reduced and related to AMPK signaling including AKT3 and SIRT1 expression. These modulation of signaling pathways could mediate the increased expression of brevican in the CN of noise-exposed rats.

In Situ Supramolecular Polymerization of Micellar Nanoobjects Induced by Polymerization.

Supramolecular polymerization offers a fascinating opportunity to develop dynamic soft materials by associating monomeric building blocks via noncovalent interactions. We report that polymerization can spontaneously drive the supramolecular polymerization of nanoscale micellar objects. We constructed the patchy micelles via two-step polymerization-induced self-assembly. A horizontal association between the patches results in a 1D supermicellar chain in situ by minimizing the enthalpic penalty of exposing the growing chains to solvent. Its length grows with increasing degree of polymerization, confirming that the supramolecular polymerization was triggered and controlled by polymerization. Our results highlight the observation that (1) the entire self-assembly process of forming, compartmentalizing, and associating the micelles can be driven by polymerization in a concerted manner and that (2) polymerization-induced self-assembly now can use compartmentalized nanoobjects as substrates beyond block copolymer chains. Polymerization-induced supramolecular polymerization could be useful for the autonomous preparation of hierarchical nanostructures.

Pravastatin Administration Alleviates Kanamycin-Induced Cochlear Injury and Hearing Loss.

The effect of statins on aminoglycoside-induced ototoxicity is controversial. This study aimed to explore the role of pravastatin (PV) in kanamycin-induced hearing loss in rats. Adult rats were intraperitoneally treated with 20 mg/kg/day of kanamycin (KM) for 10 days. In the PV- and PV + KM-treated rats, 25 mg/kg/day of PV was intraperitoneally administered for 5 days. The auditory brainstem response (ABR) thresholds were measured before and after drug treatment using a smartEP system at 4, 8, 16, and 32 kHz. Cochlear changes in poly ADP-ribose (PAR) polymerase (PARP), PAR, and caspase 3 were estimated using Western blotting. PV administration did not increase the ABR thresholds. The KM-treated rats showed elevated ABR thresholds at 4, 8, 16, and 32 kHz. The PV + KM-treated rats demonstrated lower ABR thresholds than the KM-treated rats at 4, 8, and 16 kHz. The cochlear outer hair cells and spiral ganglion cells were relatively preserved in the PV + KM-treated rats when compared with that in the KM-treated rats. The cochlear expression levels of PARP, PAR, and caspase 3 were higher in the KM-treated rats. The PV + KM-treated rats showed lower levels of PARP, PAR, and caspase 3 than the KM-treated rats. PV protected cochleae from KM-induced hearing loss in rats. The regulation of autophagy and apoptosis mediated the otoprotective effects of PV.

Chirality control of self-assembled achiral nanofibers using amines in their solid state.

Although there are numerous examples of helical and spiral conformations in nature, including plant tendrils, snail shells, and even collagen, the occurrence of supramolecular systems that are able to reversibly undergo solid-to-solid helical transformation based on environmental chiral triggers is rare. In this work, we present a supramolecular, non-helical nanofiber which shows a distinct helical rearrangement in the presence of specific diamines and monoamines, such as cyclohexanediamines, alanine, lysine, and phenylalanine, depending on the molecular chirality of the surrounding analytes. A detailed investigation on the structural organization of the nanofibers using SEM and CD spectra analysis confirmed the repeatable and reversible nature of this amplification of chiral information. Further preparation of an electrospun nanofiber film was demonstrated for distinguishing chiral diamines and monoamines in solution by film immersion and CD analysis, which is the first example of amplification of chiral information in the solid-state using electrospun nanofiber films. With this system, we could demonstrate a reusable means for detecting the molecular chirality, which also provided a unique example of reversible control of solid state rearrangement in supramolecular helicity.

Reversibly tunable helix inversion in supramolecular gels trigged by Co(2+).

Terpyridine-based ligands form octahedral complexes with Co(2+) at low cation concentrations to form helical assemblies which provide a supramolecular gel framework. Increasing the Co(2+) concentration above 0.6 equiv. reveals a second, co-existing square pyramidal complex derived assembly, having a distinct helicity. While this geometry dominates at 1 equiv. of Co(2+), we find this unique form of helical inversion to be fully reversible and controllable.

Inhibited phase behavior of gas hydrates in graphene oxide: influences of surface and geometric constraints.

Porous materials have provided us unprecedented opportunities to develop emerging technologies such as molecular storage systems and separation mechanisms. Pores have also been used as supports to contain gas hydrates for the application in gas treatments. Necessarily, an exact understanding of the properties of gas hydrates in confining pores is important. Here, we investigated the formation of CO2, CH4 and N2 hydrates in non-interlamellar voids in graphene oxide (GO), and their thermodynamic behaviors. For that, low temperature XRD and P-T traces were conducted to analyze the water structure and confirm hydrate formation, respectively, in GO after its exposure to gaseous molecules. Confinement and strong interaction of water with the hydrophilic surface of graphene oxide reduce water activity, which leads to the inhibited phase behavior of gas hydrates.

Dye-sensitized MoS2 photodetector with enhanced spectral photoresponse.

We fabricated dye-sensitized MoS2 photodetectors that utilized a single-layer MoS2 treated with rhodamine 6G (R6G) organic dye molecules (with an optical band gap of 2.38 eV or 521 nm). The proposed photodetector showed an enhanced performance with a broad spectral photoresponse and a high photoresponsivity compared with the properties of the pristine MoS2 photodetectors. The R6G dye molecules deposited onto the MoS2 layer increased the photocurrent by an order of magnitude due to charge transfer of the photoexcited electrons from the R6G molecules to the MoS2 layer. Importantly, the photodetection response extended to the infrared (λ < 980 nm, which corresponded to about half the energy band gap of MoS2), thereby distinguishing the device performance from that of a pristine MoS2 device, in which detection was only possible at wavelengths shorter than the band gap of MoS2, i.e., λ < 681 nm. The resulting device exhibited a maximum photoresponsivity of 1.17 AW(­1), a photodetectivity of 1.5 × 10(7) Jones, and a total effective quantum efficiency (EQE) of 280% at 520 nm. The device design described here presents a significant step toward high-performance 2D nanomaterial-based photodetector.

Chiral arrangement of achiral Au nanoparticles by supramolecular assembly of helical nanofiber templates.

Chiral materials composed of organized nanoparticle superstructures have promising applications to photonics and sensing. Reliable customization of the chiroptical properties of these materials remains an important goal; hence, we report a customizable scheme making use of modular gelator components for controlling the helicity and formation of nanofibers over long length scales resulting in hydrogel templates. Controlled growth of gold nanoparticles at spatially arranged locations along the nanofiber is achieved by UV reduction of Au(I) ions on the supramolecular templates. The resulting materials were found to have significant interparticle interactions and well-defined helicity to provide high quality, chiroptically active materials. With this novel approach, the tailored assembly of nanoparticle superstructures with predictable chiroptical properties can be realized in high yield, which we expect to allow rapid advancement of chiral nanomaterials research.

Rapid Dye Regeneration Mechanism of Dye-Sensitized Solar Cells.

During the light-harvesting process of dye-sensitized solar cells (DSSCs), the hole localized on the dye after the charge separation yields an oxidized dye, D(+). The fast regeneration of D(+) using the redox pair (typically the I(-)/I3(-) couple) is critical for the efficient DSSCs. However, the kinetic processes of dye regeneration remain uncertain, still promoting vigorous debates. Here, we use molecular dynamics simulations to determine that the inner-sphere electron-transfer pathway provides a rapid dye regeneration route of ∼4 ps, where penetration of I(-) next to D(+) enables an immediate electron transfer, forming a kinetic barrier. This explains the recently reported ultrafast dye regeneration rate of a few picoseconds determined experimentally. We expect that our MD based comprehensive understanding of the dye regeneration mechanism will provide a helpful guideline in designing TiO2-dye-electrolyte interfacial systems for better performing DSSCs.

Inner-sphere electron-transfer single iodide mechanism for dye regeneration in dye-sensitized solar cells.

During the regeneration of the oxidized dye in dye-sensitized solar cells, the redox couple of I(-)/I(3)(-) reduces the photo-oxidized dye. The simplest mechanism would be a direct charge-transfer mechanism from I(-) to D(+) [D(+) + I(-) → D(0) + I], called the single iodide process (SIP). However, this is an unfavorable equilibrium because the redox potential of I(•)/I(-) is 1.224 V vs SHE, which is 0.13 V higher than that of the dye. This led to the postulation of the two iodide process (TIP) [(D(+)···I(-)) + I(-) → (D···I(2)(-)) → D(0) + I(2)(-))] for a sufficiently high reducing power, but TIP is not consistent with either the recent experimental data suggesting the first-order kinetics or recent time-resolved spectroscopic measurements. To resolve this conundrum, we used quantum mechanics including Poisson-Boltzmann solvation to examine the electron-transfer process between I(-) and D(+) for the Ru(dcb)(2)NCS(2) or N3 dye. We find that I(-) is attracted to the oxidized dye, positioning I(-) next to the NCS. At this equilibrium position, the I(-) electron is already 40% transferred to the NCS, showing that the redox potential of I(-) is well matched with the dye. This matching of the redox potential occurs because I(-) is partially desolvated as it positions itself for the inner-sphere electron transfer (ISET). The previous analyses all assumed an outer-sphere electron-transfer process. Thus our ISET-SIP model is consistent with the known redox potentials and with recent experimental reports. With the ISET-SIP mechanism, one can start to consider how to enhance the dye regeneration kinetics by redesigning ligands to maximize the interaction with iodide.

The Role of Confined Water in Ionic Liquid Electrolytes for Dye-Sensitized Solar Cells.

Ionic liquids (ILs) provide an attractive medium for various chemical and redox reactions, where they are generally regarded as hydrophobic. However, Seddon et al. discovered that 4-10 wt % water absorbs into ILs that contain bulky anions, and Cammarata et al. found that the molecular state of water in ILs is dramatically different from that of bulk liquid water or that of water vapor. To determine the microstructure of water incorporated into ILs and the impact on properties, we carried out first-principles-based molecular dynamics simulations. We find water in three distinct phases depending on water content, and that the transport properties depend on the nature of the water phases. These results suggest that the optimal water content is ∼10% mole fraction of water molecules (∼1.1 wt %) for applications such as nonvolatile electrolytes for dye-sensitized solar cells (DSSCs). This suggests a strategy for improving the performance of IL DSSC by replacing water with additives that would play the same role as water (since too much water can deteriorate performance at the anode-dye interface).

Antitumor activity of ZD6474 in a metastatic orthotopic brain tumor model.

The objective of this study was to examine the antitumor effect of ZD6474, an orally available inhibitor of the vascular endothelial growth factor receptor-2 (VEGFR-2) and the epidermal growth factor receptor (EGFR), on tumor growth in an orthotopic metastatic brain tumor model. In order to determine the antitumor mechanism of ZD6474 treatment, in vitro and in vivo studies were performed. Human breast carcinoma cells (MDA-MB-435) were injected using direct intracranial (IC) inoculation (5x105 cells/100 µl) and internal carotid artery (ICA) injection (5x104 cells/100 µl) in Balb/c-nu female mice. Daily oral treatment with ZD6474 (50 mg/kg) was initiated on day 14 after the establishment of micrometastasis. Mice (n=12 per group) were sacrificed on day 28. Western blot analysis revealed that the autophosphorylation of EGFR and Akt was increasingly decreased with ZD6474 treatment in lung and brain endothelial cells and the MDA-MB-435 cell line. MTT assay also showed that the in vitro antitumor activity of ZD6474 was dependent on EGFR tyrosine kinase inhibition at a higher dose. Daily oral treatment with ZD6474 led to marked inhibition of metastatic tumor growth in the ICA injection and the direct IC inoculation models (median size 3.5 mm3, range 1.6-13.9 mm3) as compared to the control group (median size 62.4 mm3, range 11.5-206.9 mm3). These results suggest that simultaneous inhibition of both the EGFR and VEGFR-2 signaling pathways has a valuable therapeutic effect through its inhibition of the growth of metastatic brain tumors.