Videotelephony-assisted medical direction to improve emergency medical service.

INTRODUCTION: In South Korea, on-line medical direction using voice calls has been implemented to improve the quality of the emergency medical system. However, in the same, short time span, video will be able to convey more information than by voice. The purpose of this study is to find out if videotelephony-assisted medical direction (VAMD) can change the intervention of the emergency medical technician compared to using conventional voice calls. METHODS: We conducted a prospective study of 312 patients with online medical direction from November 2017 to November 2018. We assisted patients with direct medical direction using conventional voice calls from October to November 2017, and then VAMD was implemented from October to November 2018. RESULTS: From the total number of conventional voice calls, 131 were used for this study, and of the total number of VAMD interventions, 181 were included. There were differences between conventional voice call and VAMD interventions in such types of medical direction as hospital selection (7.6% vs. 36.6%), ECG interpretation (0% vs. 3.4%), and advice on medical techniques (0% vs. 25.1%). The effectiveness of VAMD by survey is greater compared to conventional direct medical direction using voice calls (median value, 3.0 vs. 1.5). CONCLUSIONS: The number of instances of medical direction for some interventions, such as interpretation of ECG and advice on medical techniques that did not perform well in conventional voice calls, increased in VAMD. VAMD may play an important role in the prehospital emergency care.

Unsaturated Drift Velocity of Monolayer Graphene.

We observe that carriers in graphene can be accelerated to the Fermi velocity without heating the lattice. At large Fermi energy | EF| > 110 meV, electrons excited by a high-power terahertz pulse ETHz relax by emitting optical phonons, resulting in heating of the graphene lattice and optical-phonon generation. This is owing to enhanced electron-phonon scattering at large Fermi energy, at which the large phase space is available for hot electrons. The emitted optical phonons cause carrier scattering, reducing the drift velocity or carrier mobility. However, for | EF| ≤ 110 meV, electron-phonon scattering rate is suppressed owing to the diminishing density of states near the Dirac point. Therefore, ETHz continues to accelerate carriers without them losing energy to optical phonons, allowing the carriers to travel at the Fermi velocity. The exotic carrier dynamics does not result from the massless nature, but the electron-optical-phonon scattering rate depends on Fermi level in the graphene. Our observations provide insight into the application of graphene for high-speed electronics without degrading carrier mobility.

Highly Sensitive Detection of 4-Methylimidazole Using a Terahertz Metamaterial.

In this study, we demonstrated a highly sensitive detection method of 4-methylimidazole (4-MeI), a carcinogenic material, by using a terahertz (THz) metamaterial at a THz region. The THz metamaterials were fabricated with a metal array, using an electric-field-coupled inductor-capacitor (ELC) resonator structure, and a finite-difference time-domain (FDTD) simulation showed good agreement with the experimental results. We measured the THz spectra of the metamaterials to detect the 4-MeI concentrations of 0, 1, 2, 5, 10, 15, and 20 mg/L. The resonance frequency of the metamaterial was shifted by, approximately, 8 GHz and transmittance at the resonance frequency increased to 2 × 10-3, as the concentration was increased, up to 20 mg/L. Our study provides new insight into the application of metamaterials in detecting carcinogens, using a THz technique.

Compartment syndrome in the forearm related to carbon monoxide intoxication: case report.

INTRODUCTION: Carbon monoxide (CO) poisoning is one of the most common forms of intoxication around the world. One of the complications associated with CO exposure is direct toxicity to the skeletal muscles. Though compartment syndrome induced by CO intoxication is rare, it is a well-known complication. In this study, we present a case of CO poisoning in a patient who developed compartment syndrome in his forearm. CASE REPORT: A 22-year-old man was found unconscious in a motel where a briquette had burned. He was later diagnosed with rhabdomyolysis associated with CO poisoning. After he regained consciousness, he experienced difficulty in moving his left arm, with sensory impairment in the same arm. He was diagnosed with compartment syndrome, and an emergency fasciotomy was performed. One month later, electromyography was performed which revealed left median, ulnar, radial, and musculocutaneous nerve palsy. DISCUSSION: Compartment syndrome induced by CO intoxication is rare but is a well-known complication. Compartment syndrome is a limb-threatening and life-threatening condition. If untreated, the pressure in the muscle may rise, which can lead to tissue necrosis. Generally, nerve paralysis does not occur in CO poisoning. In our case, it occurred as median, ulnar, radial and musculocutaneous nerve palsy. CONCLUSION: Side effects of CO poisoning can be extant, especially for those who are unconscious since they cannot express pain, numbness, and motor weakness. It is important to not overlook compartment syndrome, to double-check whether there is swelling, change in skin color, or skin firmness in extremities, and to observe the patient closely.

Invisible Security Printing on Photoresist Polymer Readable by Terahertz Spectroscopy.

We experimentally modulate the refractive index and the absorption coefficient of an SU-8 dry film in the terahertz region by UV light (362 nm) exposure with time dependency. Consequently, the refractive index of SU-8 film is increased by approximately 6% after UV light exposure. Moreover, the absorption coefficient also changes significantly. Using the reflective terahertz imaging technique, in addition, we can read security information printed by UV treatment on an SU-8 film that is transparent in the visible spectrum. From these results, we successfully demonstrate security printing and reading by using photoresist materials and the terahertz technique. This investigation would provide a new insight into anti-counterfeiting applications in fields that need security.

4D Visualization of a Nonthermal Coherent Magnon in a Laser Heated Lattice by an X-ray Free Electron Laser.

Ultrafast optical manipulation of magnetic phenomena is an exciting achievement of mankind, expanding one's horizon of knowledge toward the functional nonequilibrium states. The dynamics acting on an extremely short timescale push the detection limits that reveal fascinating light-matter interactions for nonthermal creation of effective magnetic fields. While some cases are benchmarked by emergent transient behaviors, otherwise identifying the nonthermal effects remains challenging. Here, a femtosecond time-resolved resonant magnetic X-ray diffraction experiment is introduced, which uses an X-ray free-electron laser (XFEL) to distinguish between the effective field and the photoinduced thermal effect. It is observed that a multiferroic Y-type hexaferrite exhibits magnetic Bragg peak intensity oscillations manifesting entangled antiferromagnetic (AFM) and ferromagnetic (FM) Fourier components of a coherent AFM magnon. The magnon trajectory constructed in 3D space and time domains is decisive to evince ultrafast field formation preceding the lattice thermalization. A remarkable impact of photoexcitation across the electronic bandgap is directly unraveled, amplifying the photomagnetic coupling that is one of the highest among AFM dielectrics. Leveraging the above-bandgap photoexcitation, this energy-efficient optical process further suggests a novel photomagnetic control of ferroelectricity in multiferroics.

Ultrafast Auger process in few-layer PtSe2.

Enhanced many-body interactions due to strong Coulomb interactions and quantum confinement are one of the most prominent features of two-dimensional systems. The Auger process is a representative many-body interaction typically observed in two-dimensional semiconductors, determining important physical properties of materials, such as carrier lifetime, photoconductivity, and emission quantum yield. Recently, platinum dichalcogenides, represented by PtSe2 and PtS2, have attracted great attention due to their superior air stability, thickness-dependent semimetal-to-semiconductor transition, and exotic magnetic characteristics. However, the Auger process in platinum dichalcogenides has not been investigated to date. Here, we utilized ultrafast optical-pump terahertz-probe spectroscopy to explore carrier dynamics in few-layer semiconducting PtSe2. Most of the excited carriers are trapped by defects within ∼10 ps after excitation due to high defect density. We overcome this challenge by raising the excitation intensity to saturate trap sites with carriers, and observed a many-body process involving the carriers that survived the rapid trapping. This process is not band-to-band Auger recombination, but rather defect-assisted Auger recombination in which free carriers interact with trapped carriers at defects. Theoretical simulations show that this three-body Auger process can be approximated as bimolecular recombination at the rate of ∼3.3 × 10-3 cm2 s-1. This work provides insights into the interplay between ultrafast many-body processes and defects in two-dimensional semiconductors.

Universal field-tunable terahertz emission by ultrafast photoinduced demagnetization in Fe, Ni, and Co ferromagnetic films.

We report a universal terahertz (THz) emission behavior from simple Ni, Fe, and Co metallic ferromagnetic films, triggered by the femtosecond laser pulse and subsequent photoinduced demagnetization on an ultrafast time scale. THz emission behavior in ferromagnetic films is found to be consistent with initial magnetization states controlled by external fields, where the hysteresis of the maximal THz emission signal is observed to be well-matched with the magnetic hysteresis curve. It is experimentally demonstrated that the ultrafast THz emission by the photoinduced demagnetization is controllable in a simple way by external fields as well as pump fluences.

Qualitative identification of food materials by complex refractive index mapping in the terahertz range.

We investigated the feasibility of qualitative food analysis using complex refractive index mapping of food materials in the terahertz (THz) frequency range. We studied optical properties such as the refractive index and absorption coefficient of food materials, including insects as foreign substances, from 0.2 to 1.3 THz. Although some food materials had a complex composition, their refractive indices were approximated with effective medium values, and therefore, they could be discriminated on the complex refractive index map. To demonstrate food quality inspection with THz imaging, we obtained THz reflective images and time-of-flight imaging of hidden defects in a sugar and milk powder matrix by using time domain THz pulses. Our results indicate that foreign substances can be clearly classified and detected according to the optical parameters of the foods and insects by using THz pulses.

Transient Carrier Cooling Enhanced by Grain Boundaries in Graphene Monolayer.

Using a high terahertz (THz) electric field (ETHz), the carrier scattering in graphene was studied with an electric field of up to 282 kV/cm. When the grain size of graphene monolayers varies from small (5 µm) and medium (70 µm) to large grains (500 µm), the dominant carrier scattering source in large- and small-grained graphene differs at high THz field, i.e., there is optical phonon scattering for large grains and defect scattering for small grains. Although the electron-optical phonon coupling strength is the same for all grain sizes in our study, the enhanced optical phonon scattering in the high THz field from the large-grained graphene is caused by a higher optical phonon temperature, originating from the slow relaxation of accelerated electrons. Unlike the large-grained graphene, lower electron and optical phonon temperatures are found in the small-grained graphene monolayer, resulting from the effective carrier cooling through the defects, called supercollisions. Our results indicate that the carrier mobility in the high-crystalline graphene is easily vulnerable to scattering by the optical phonons. Thus, controlling the population of defect sites, as a means for carrier cooling, can enhance the carrier mobility at high electric fields in graphene electronics by suppressing the heating of optical phonons.