Hot electron transport in suspended multilayer graphene

We study hot electron transport in short-channel suspended multilayer graphene devices created by a distinct experimental approach. For devices with semi-transparent contact barriers, a dip of differential conductance (dI/dV) has been observed at source drain bias Vd = 0, along with anomalies at higher Vd likely induced by optical phonon scattering. For devices with low contact barriers, only the dI/dV dip at Vd = 0 is observed, and we find a well-fit logarithmic dependence of dI/dV on both the bias Vd and the temperature T. The logarithmic Vd dependence is explained with the hot electron effect and the logarithmic T dependence could be attributed to the weak-localization in two-dimensions

Performance Validation of a Planar Hall Resistance Biosensor through Beta-Amyloid Biomarker

Magnetic sensors have great potential for biomedical applications, particularly, detection of magnetically-labeled biomolecules and cells. On the basis of the advantage of the planar Hall effect sensor, which consists of improved thermal stability as compared with other magnetic sensors, we have designed a portable biosensor platform that can detect magnetic labels without applying any external magnetic field. The trilayer sensor, with a composition of Ta (5 nm)/NiFe (10 nm)/Cu (x = 0 nm~1.2 nm)/IrMn (10 nm)/Ta (5 nm), was deposited on a silicon wafer using photolithography and a sputtering system, where the optimized sensor sensitivity was 6 μV/(Oe∙mA). The detection of the magnetic label was done by comparing the signals obtained in first harmonic AC mode (1f mode) using an external magnetic field and in the second harmonic AC mode (2f mode) with a self-field generated by current passing through the sensor. In addition, a technique for the β-amyloid biomarker-based antibody-antigen sandwich model was demonstrated for the detection of a series of concentrations of magnetic labels using the self-field mode method, where the signal-to-noise ratio (SNR) was high. The generated self-field was enough to detect an immobilized magnetic tag without an additional external magnetic field. Hence, it could be possible to reduce the device size to use the point-of-care testing using a portable circuit system.1

Probing phonon emission via hot carrier transport in suspended graphitic multilayers

We study hot carrier transport under magnetic fields up to 15 T in suspended graphitic multilayers through differential conductance (dI/dV) spectroscopy. Distinct high-energy dI/dV anomalies have been observed and shown to be related to intrinsic phonon-emission processes in graphite. The evolution of such dI/dV anomalies under magnetic fields is further understood as a consequence of inter-Landau level cyclotron-phonon resonance scattering. The observed magneto-phonon effects not only shed light on the physical mechanisms responsible for high-current transport in graphitic systems, but also offer new perspectives for optimizing performance in graphitic nano-electronic devices.Comment: 19 pages, 5 figures, plus supplementary materials (3 pages

Comparing the neurologic outcomes of patients with out-of-hospital cardiac arrest according to prehospital advanced airway management method and transport time interval

Objective The incidences of prehospital advanced airway management by emergency medical technicians in South Korea are increasing; however, whether this procedure improves the survival outcomes of patients experiencing out-of-hospital cardiac arrest remains unclear. The present study aimed to investigate the association between prehospital advanced airway management and neurologic outcomes according to a transport time interval (TTI) using the Korean Cardiac Arrest Research Consortium database. Methods We retrospectively analyzed the favorable database entries that were prospectively collected between October 2015 and December 2016. Patients aged 18 years or older who experienced cardiac arrest that was presumed to be of a medical etiology and that occurred prior to the arrival of emergency medical service personnel were included. The exposure variable was the type of prehospital airway management provided by emergency medical technicians. The primary endpoint was a favorable neurologic outcome. Results Of 1,871 patients who experienced out-of-hospital cardiac arrest, 785 (42.0%), 121 (6.5%), and 965 (51.6%) were managed with bag-valve-mask ventilation, endotracheal intubation (ETI), and supraglottic airway (SGA) devices, respectively. SGAs and ETI provided no advantage in terms of favorable neurologic outcome in patients with TTIs ≥12 minutes (odds ratio [OR], 1.37; confidence interval [CI], 0.65–2.87 for SGAs; OR, 1.31; CI, 0.30–5.81 for ETI) or in patients with TTI <12 minutes (OR, 0.57; CI, 0.31–1.07 for SGAs; OR, 0.63; CI, 0.12–3.26 for ETI). Conclusion Neither the prehospital use of SGA nor administration of ETI was associated with superior neurologic outcomes compared with bag-valve-mask ventilation

Electrically-driven phase transition in magnetite nanostructures

Magnetite (Fe$_{3}$O$_{4}$), an archetypal transition metal oxide, has been used for thousands of years, from lodestones in primitive compasses[1] to a candidate material for magnetoelectronic devices.[2] In 1939 Verwey[3] found that bulk magnetite undergoes a transition at T$_{V}$ $\approx$ 120 K from a high temperature "bad metal" conducting phase to a low-temperature insulating phase. He suggested[4] that high temperature conduction is via the fluctuating and correlated valences of the octahedral iron atoms, and that the transition is the onset of charge ordering upon cooling. The Verwey transition mechanism and the question of charge ordering remain highly controversial.[5-11] Here we show that magnetite nanocrystals and single-crystal thin films exhibit an electrically driven phase transition below the Verwey temperature. The signature of this transition is the onset of sharp conductance switching in high electric fields, hysteretic in voltage. We demonstrate that this transition is not due to local heating, but instead is due to the breakdown of the correlated insulating state when driven out of equilibrium by electrical bias. We anticipate that further studies of this newly observed transition and its low-temperature conducting phase will shed light on how charge ordering and vibrational degrees of freedom determine the ground state of this important compound.Comment: 17 pages, 4 figure

Descending necrotizing mediastinitis after a trigger point injection

Descending necrotizing mediastinitis (DNM) is a rare form of mediastinal infection. Most cases are associated with esophageal rupture. DNM after a trigger point injection in the upper trapezius has not been described previously. We present a case of DNM after a trigger point injection in the upper trapezius. A 70-year-old man visited the emergency department with chest discomfort and fever after a trigger point injection in the left upper trapezius. Chest computed tomography showed evidence of DNM, and antibiotic therapy was immediately administered intravenously. Because of the risk of sudden death, poor prognosis due to underlying disease, and his age, he declined surgical treatment and died of septic shock. Although trigger point injections are generally considered safe, caution should be used in patients with an underlying disease or in the elderly. Early diagnosis, broad-spectrum antibiotics, and aggressive surgical management are essential to improve the prognosis

Capacitive NO₂ Detection Using CVD Graphene-Based Device

A graphene-based capacitive NO2 sensing device was developed by utilizing the quantum capacitance effect. We have used a graphene field-effect transistor (G-FET) device whose geometrical capacitance is enhanced by incorporating an aluminum back-gate electrode with a naturally oxidized aluminum surface as an insulating layer. When the graphene, the top-side of the device, is exposed to NO2, the quantum capacitance of graphene and, thus, the measured capacitance of the device, changed in accordance with NO2 concentrations ranging from 1–100 parts per million (ppm). The operational principle of the proposed system is also explained with the changes in gate voltage-dependent capacitance of the G-FET exposed to various concentrations of NO2. Further analyses regarding carrier density changes and potential variances under various concentrations of NO2 are also presented to strengthen the argument. The results demonstrate the feasibility of capacitive NO2 sensing using graphene and the operational principle of capacitive NO2 sensing