High Performance Electrocatalysts Based on Pt Nanoarchitecture for Fuel Cell Applications

Fuel cells, converting chemical energy from fuels into electricity directly without the need for combustion, are promising energy conversion devices for their potential applications as environmentally friendly, energy efficient power sources. However, to take fuel cell technology forward towards commercialization, we need to achieve further improvements in electrocatalyst technology, which can play an extremely important role in essentially determining cost-effectiveness, performance, and durability. In particular, platinum- (Pt-) based electrocatalyst approaches have been extensively investigated and actively pursued to meet those demands as an ideal fuel cell catalyst due to their most outstanding activity for both cathode oxygen reduction reactions and anode fuel oxidation reactions. In this review, we will address important issues and recent progress in the development of Pt-based catalysts, their synthesis, and characterization. We will also review snapshots of research that are focused on essential dynamics aspects of electrocatalytic reactions, such as the shape effects on the catalytic activity of Pt-based nanostructures, the relationships between structural morphology of Pt-based nanostructures and electrochemical reactions on both cathode and anode electrodes, and the effects of composition and electronic structure of Pt-based catalysts on electrochemical reaction properties of fuel cells.</jats:p

Hyoid bone position as an indicator of severe obstructive sleep apnea

Abstract Background The objective of this study was to evaluate the relationship between hyoid bone position and severity of obstructive sleep apnea (OSA), and to investigate its value as a complementary diagnostic method. Methods A total of 133 patients who were diagnosed as OSA with an apnea-hypopnea index ≥ 5 were included. Clinical examination, level I polysomnography (PSG) and lateral cephalographic analysis were done. Comprehensive PSG characteristics were compared according to hyoid bone position and the predictive power of the distance between the mandible and hyoid was assessed. Results The distance between the hyoid bone and mandibular plane was significantly longer in the severe OSA group (p = 0.013). The distance from hyoid bone to third vertebrae (C3) and hyoid bone to mentum were also longer in the severe OSA group but the difference did not reach statistical significance. The distance between hyoid bone and mandibular plane was effective in predicting severe OSA, with a cut-off value of 19.45mm (AUC = 0.623, p = 0.040). When grouped according to a distance cut-off value of 19.45mm, those with a longer distance between the hyoid bone and mandibular plane showed more respiratory disturbance, lower oxygen saturation levels, less deep slow wave sleep, and more fragmented sleep with arousals. Conclusions The distance between the hyoid bone and mandibular plane derived from cephalometric analysis can be a valuable diagnostic parameter that can be easily applied in differentiating severe OSA patients

Quenched Fe Moment in the Collapsed Tetragonal Phase of Ca1−x_{1-x}Prx_{x}Fe2_2As2_2

We report $^{75}$As NMR studies on single crystals of rare-earth doped iron pnictides superconductor Ca$_{1-x}$Pr$_{x}$Fe$_{2}$As$_{2}$ ($x$=0.075 and 0.15). The $^{75}$As spectra show a chemical pressure effect with doping and a first order structure transition to the collapsed tetragonal phase upon cooling. A sharp drop of the Knight shift is seen below the structural transition, whereas $1/T_1$ is strongly enhanced at low-temperatures. These evidences indicate quenching of Fe local magnetism and short-range ordering of Pr$^{3+}$ moment in the collapsed tetragonal phase. The quenched Fe moment through structure collapse suggests a strong interplay of structure and magnetism, which is important for understanding the nature of the collapsed tetragonal phase.Comment: 5 pages, 5 figure

Does physical activity level have an impact on long-term treatment response in temporomandibular disorders: protocol for a prospective study

Abstract Background Temporomandibular disorders (TMD) is a disease characterized by pain and dysfunction of the masticatory muscles and temporomandibular joint. Many factors have been found to be related to the disease however, the underlying mechanism is yet to be fully elucidated. Physical activity is widely known to modulate pain intensity in various pain disorders. However, literature suggesting the association between physical activity and signs and symptoms of TMD are limited. Methods and design The Physical Activity in TMD (PAT) is a prospective study on TMD patients that aims to determine how daily physical activity and sleep duration affect long-term TMD prognosis following conventional treatment. To analyze such effects, objective data on daily physical activity levels will be collected along with clinical indices including mouth opening ranges and masticatory muscle palpation responses from adult Koreans diagnosed with TMD following standardized diagnostic procedures. Well-known comorbidities of TMD will be extensively evaluated based on validated structured questionnaires on sleep quality, fatigue level, widespread pain, psychological status including depression and anxiety, autonomic symptoms, and health-related quality of life. The collected data will be analyzed according to TMD pain severity and physical activity level, and correlations among physical activity indices and long-term TMD prognosis will be investigated. Discussion In this longitudinal prospective study of adult Koreans diagnosed with TMD following standardized diagnostic procedures, primary outcomes include physical activity levels and long-term TMD clinical outcomes and secondary outcomes include disability from pain and related comorbidity levels. Results and analysis are ongoing. The results of this study will provide reliable data for future research and establish clinical guidelines that will allow cause-related, patient-tailored personalized medicine for TMD. Trial registration: Clinical Research Information Service (Registration number: KCT0007107). Registered March 22 2022 https://cris.nih.go.kr/cris/search/detailSearch.do?search_lang=E&focus=reset_12&search_page=M&pageSize=10&page=undefined&seq=21420&status=5&seq_group=21420

High frequency plant regeneration from mature seedderived callus of Italian ryegrass (Lolium multiflorum) cultivars

In the present study, we have developed a high-frequency plant regeneration system for Italian ryegrass via callus culture using mature seeds as explants. Optimal embryogenic callus induction was found to occur in MS medium containing 5 mg l-1 2,4-D, 0.5 mg l-1 BA, 500 mg l-1 L-proline, 1 g l-1 casein hydrolysate, 30 g l-1 sucrose, 7 mg l-1 AgNO3, 2 mg l-1 CuSO4 and solidified with 3 g l-1 Gelrite. The highest regeneration rate was obtained in MS medium containing 1 mg l-1 2,4-D, 5 mg l-1 BA, 500 mg l-1 L-proline, 1 g l-1 casein hydrolysate, 1 mg l-1 thiamine-HCl, 30 g l-1 sucrose, 7 mg l-1 AgNO3, 2 mg l-1 CuSO4 and solidified with 3 g l-1 Gelrite. By using the most effective treatment determined for each parameter, the highest rates of embryogenic callus formation (48.9%) and regeneration (47.6%) were obtained with the Hwasan 101 cultivar. The overall plant regeneration rates of the examined cultivars ranged from 7.5 to 23.2%. Thus, optimization of regeneration frequency using mature seeds as explant material may offer a simple and efficient protocol for Italian ryegrass that may improve molecular breeding of this species

Transport spin polarisation in SrRuO3 measured through Point Contact Andreev reflection

We report a study in which Andreev reflection using a Nb point contact is used to measure the transport spin polarisation of the 4d itinerant ferromagnet SrRuO3. By performing the study in high quality thin films with residual resistivities less than 7micro-ohm-cm, we ensure that the study is done in the ballistic limit, a regime which is difficult to reach in oxide ferromagnets. The degree of transport spin polarisation that we find is comparable to that of the hole doped rare-earth manganites. We conclude that the large transport spin polarisation results mainly from a difference in the Fermi velocities between the majority and minority spin channels in this material.Comment: Text and 2 Figure

Galactic 511 keV line from MeV millicharged dark matter

We present a possible explanation of the recently observed 511 keV $\gamma$-ray anomaly with a new ``millicharged'' fermion. The new fermion is light (${\cal O}({\rm MeV})$) but has never been observed by any collider experiments mainly because of its tiny electromagnetic charge $\epsilon e$. We show that constraints from its relic density in the Universe and collider experiments allow a parameter range such that the 511 keV cosmic $\gamma$-ray emission from the galactic bulge may be due to positron production from this millicharged fermion.Comment: 14 pages, 3 figures; To appear in Phys. Rev.