Emergence of Two-Dimensional Massless Dirac Fermions, Chiral Pseudospins, and Berry's Phase in Potassium Doped Few-Layer Black Phosphorus

Thin flakes of black phosphorus (BP) are a two-dimensional (2D) semiconductor whose energy gap is predicted being sensitive to the number of layers and external perturbations. Very recently, it was found that a simple method of potassium (K) doping on the surface of BP closes its band gap completely, producing a Dirac semimetal state with a linear band dispersion in the armchair direction and a quadratic one in the zigzag direction. Here, based on first-principles density functional calculations, we predict that, beyond the critical K density of the gap closure, 2D massless Dirac Fermions (i.e., Dirac cones) emerge in K-doped few-layer BP, with linear band dispersions in all momentum directions, and the electronic states around Dirac points have chiral pseudospins and Berry's phase. These features are robust with respect to the spin-orbit interaction and may lead to graphene-like electronic transport properties with greater flexibility for potential device applications

Hydroxyapatite Humidifier Vibrator Housing Fabrication and Characteristics

The humidifier vibrator housing is difficult to clean and prone to contamination due to its metallic material. To overcome these shortcomings, the humidifier vibrator housing was manufactured using Hydroxyapatite as a raw material. Although hydroxyapatite has excellent antibacterial properties and biocompatibility, it is difficult to manufacture a sintered body due to its weak fracture toughness. Therefore, hydroxyapatite sintered compacts were prepared according to the amount of plasticizer added and their physical properties were compared. The average compressive strength was 395.1 N·mm-2 at 8 % of the amount of added plasticizer, and the average bending strength was 61.8 N·mm-2 at 6 % of the amount of added plasticizer. The hydroxyapatite sintered compact showed the effect of inhibiting the production of bacteria regardless of the amount of plasticizer added. As a result of this physical property study, it was possible to develop a humidifier vibrator housing with excellent antibacterial properties and maintaining mechanical strength

STIFFNESS OF 3D COLLAGEN MATRICES REGULATES CDC42 ACTIVITY OF ENDOTHELIAL COLONY FORMING CELLS DURING EARLY VACUOLE

poster abstractRecent preclinical reports have provided evidence that endothelial colony forming cells (ECFCs), a subset of endothelial progenitor cells, significantly improve vessel formation, largely due to their robust vasculogenic potential. While it has been known that the Rho family GTPase Cdc42 is involved in this ECFC-driven vessel formation process, the effect of extracellular matrix (ECM) stiffness on its activity during vessel formation is largely unknown. Using a fluorescence resonance energy transfer (FRET)-based Cdc42 biosen-sor, we examined the spatio-temporal activity of Cdc42 of ECFCs in three-dimensional (3D) collagen matrices with varying stiffness. The result re-vealed that ECFCs exhibited an increase in Cdc42 activity in a soft (150 Pa) matrix, while they were much less responsive in a stiff (1000 Pa) matrix. In both soft and stiff matrices, Cdc42 was highly activated near vacuoles; how-ever, its activity is higher in a soft matrix than that in a stiff matrix. The ob-served Cdc42 activity was closely associated with vacuole area. Soft matri-ces induced higher Cdc42 activity, faster vacuole formation, and larger vac-uole area than stiff matrices. Time courses of Cdc42 activity and vacuole formation data revealed that Cdc42 activity proceeds vacuole formation. Collectively, these results suggest that matrix stiffness is critical in regulat-ing Cdc42 activity in ECFCs and its activation is an important step in early vacuole formation

The Effect of Cyclosporine and Dexamethasone on Suppression of Medial Thickening after Arterial Injury in Rats

Vascular proliferative lesion is one of the most important causes of stenosis and late thrombosis in arterial reconstructions. We studied the effect of cyclosporine and dexamethasone on decreasing the hyperplastic response after experimental arterial injury in rats. Ninety female rats were assigned to one of four groups, each receiving daily subcutaneous injections of either (1) saline (control), or (2) cyclosporine(CYA) 5mg/Kg/D, or (3) dexamethasone (DEXA) O. 1 mg/Kg/D, or (4) CYA 5mg/kg/D and DEXA O. Img/kg/D. Injections were started 1 day before the intimal injury and continued daily for 6 weeks. Arterial injury was created in 90 rats by rotating a Imm coronary dilator in the right common iliac artery. The vessels were harvested 1,4,6 weeks after injury and the thickness of the tunica media was measured. In the control group the injured iliac artery had significant medial thickening when compared to the noninjured (P(O. 0001) 1 week after injury. Injured arteries treated with CYA or DEXA or CYA and DEXA showed significantly less medial thickening when compared to that of control (P(O. 001) but no significant difference was noted among drug treated groups for 1 and 4 weeks of treatment. At 6 weeks, however, medial thickness in the CYA and DEXA group was significantly less than that of the CYA or DEXA group(P( O. 05). These data suggest that CYA and DEXA are effective in suppressing the hyperplatic myointimal reaction to an intimal injury. In addition, these data also provide the evidence that immunological mechanisms may modulate vascular proliferative lesions

A Reconfigurable Readout Integrated Circuit for Heterogeneous Display-Based Multi-Sensor Systems

This paper presents a reconfigurable multi-sensor interface and its readout integrated circuit (ROIC) for display-based multi-sensor systems, which builds up multi-sensor functions by utilizing touch screen panels. In addition to inherent touch detection, physiological and environmental sensor interfaces are incorporated. The reconfigurable feature is effectively implemented by proposing two basis readout topologies of amplifier-based and oscillator-based circuits. For noise-immune design against various noises from inherent human-touch operations, an alternate-sampling error-correction scheme is proposed and integrated inside the ROIC, achieving a 12-bit resolution of successive approximation register (SAR) of analog-to-digital conversion without additional calibrations. A ROIC prototype that includes the whole proposed functions and data converters was fabricated in a 0.18 ??m complementary metal oxide semiconductor (CMOS) process, and its feasibility was experimentally verified to support multiple heterogeneous sensing functions of touch, electrocardiogram, body impedance, and environmental sensors.ope

Two-Dimensional Dirac Fermions Protected by Space-Time Inversion Symmetry in Black Phosphorus

We report the realization of novel symmetry-protected Dirac fermions in a surface-doped two-dimensional (2D) semiconductor, black phosphorus. The widely tunable band gap of black phosphorus by the surface Stark effect is employed to achieve a surprisingly large band inversion up to ~0.6 eV. High-resolution angle-resolved photoemission spectra directly reveal the pair creation of Dirac points and their moving along the axis of the glide-mirror symmetry. Unlike graphene, the Dirac point of black phosphorus is stable, as protected by spacetime inversion symmetry, even in the presence of spin-orbit coupling. Our results establish black phosphorus in the inverted regime as a simple model system of 2D symmetry-protected (topological) Dirac semimetals, offering an unprecedented opportunity for the discovery of 2D Weyl semimetals