Flat-surface-assisted and self-regulated oxidation resistance of Cu(111).

Oxidation can deteriorate the properties of copper that are critical for its use, particularly in the semiconductor industry and electro-optics applications1-7. This has prompted numerous studies exploring copper oxidation and possible passivation strategies8. In situ observations have, for example, shown that oxidation involves stepped surfaces: Cu2O growth occurs on flat surfaces as a result of Cu adatoms detaching from steps and diffusing across terraces9-11. But even though this mechanism explains why single-crystalline copper is more resistant to oxidation than polycrystalline copper, the fact that flat copper surfaces can be free of oxidation has not been explored further. Here we report the fabrication of copper thin films that are semi-permanently oxidation resistant because they consist of flat surfaces with only occasional mono-atomic steps. First-principles calculations confirm that mono-atomic step edges are as impervious to oxygen as flat surfaces and that surface adsorption of O atoms is suppressed once an oxygen face-centred cubic (fcc) surface site coverage of 50% has been reached. These combined effects explain the exceptional oxidation resistance of ultraflat Cu surfaces.

Enhanced Perception for Autonomous Vehicles at Obstructed Intersections: An Implementation of Vehicle to Infrastructure (V2I) Collaboration.

In urban intersections, the sensory capabilities of autonomous vehicles (AVs) are often hindered by visual obstructions, posing significant challenges to their robust and safe operation. This paper presents an implementation study focused on enhancing the safety and robustness of Connected Automated Vehicles (CAVs) in scenarios with occluded visibility at urban intersections. A novel LiDAR Infrastructure System is established for roadside sensing, combined with Baidu Apollo's Automated Driving System (ADS) and Cohda Wireless V2X communication hardware, and an integrated platform is established for roadside perception enhancement in autonomous driving. The field tests were conducted at the Singapore CETRAN (Centre of Excellence for Testing & Research of Autonomous Vehicles-NTU) autonomous vehicle test track, with the communication protocol adhering to SAE J2735 V2X communication standards. Communication latency and packet delivery ratio were analyzed as the evaluation metrics. The test results showed that the system can help CAV detect obstacles in advance under urban occluded scenarios.

Influence of Nanosize Hole Defects and their Geometric Arrangements on the Superfluid Density in Atomically Thin Single Crystals of Indium Superconductor.

Using Indium sqrt[7]×sqrt[3] on Si(111) as an atomically thin superconductor platform, and by systematically controlling the density of nanohole defects (nanometer size voids), we reveal the impacts of defect density and defect geometric arrangements on superconductivity at macroscopic and microscopic length scales. When nanohole defects are uniformly dispersed in the atomic layer, the superfluid density monotonically decreases as a function of defect density (from 0.7% to 5% of the surface area) with minor change in the transition temperature T_{C}, measured both microscopically and macroscopically. With a slight increase in the defect density from 5% to 6%, these point defects are organized into defect chains that enclose individual two-dimensional patches. This new geometric arrangement of defects dramatically impacts the superconductivity, leading to the total disappearance of macroscopic superfluid density and the collapse of the microscopic superconducting gap. This study sheds new light on the understanding of how local defects and their geometric arrangements impact superconductivity in the two-dimensional limit.

Multiple charge density wave phases of monolayer VSe2manifested by graphene substrates.

A combined study of scanning tunneling microscopy (STM) and angle-resolved photoemission spectroscopy (ARPES) is conducted to understand the multiple charge density wave (CDW) phases of monolayer (ML) VSe2films manifested by graphene substrates. Submonolayer (∼0.8 ML) VSe2films are prepared on two different substrates of single-layer graphene (SLG) and bi-layer graphene (BLG) on a 6H-SiC(0001). We find that ML VSe2films are less coupled to the SLG substrate compared to that of ML VSe2/BLG. Then, ML VSe2grown on SLG and BLG substrates reveals a very different topography in STM. While ML VSe2/BLG shows one unidirectional modulation of √3 × 2 and √3 × âˆš7 CDW in topography, ML VSe2/SLG presents a clear modulation of 4 × 1 CDW interfering with √3 × 2 and √3 × âˆš7 CDW which has not been previously observed. We explicitly show that the reciprocal vector of 4 × 1 CDW fits perfectly into the long parallel sections of cigar-shaped Fermi surfaces near the M point in ML VSe2, satisfying Fermi surface nesting. Since bulk VSe2is also well-known for the 4 × 4 × 3 CDW formed by Fermi surface nesting, the 4 × 1 CDW in ML VSe2/SLG is attributed to the planar projection of 4 × 4 × 3 CDW in bulk. Our result clarifies the nature of the 4 × 1 CDW in ML VSe2system and is a good example demonstrating the essential role of substrates in two-dimensional transition metal dichalcogenides.

Western Medicine Versus Eastern Medicine: Do Both Have a Common Root, Scientific Background, and Worldwide Recognition?

This review is designed to initiate a discussion we believe is necessary for the biomedical community, because of some recent evidences for existing of a new body anatomical system, or the primo vascular system (PVS), which could be the missing link in the scientific explanation of the unknown mechanism of action of acupuncture. Some important questions for the medical society, (eg, "What is the main source of the mistrust of Western medicine toward traditional Oriental medicine and could it be overcome?" or "Is the PVS a real one and what is its distribution, formation, and function?" or "Are there scientific proofs for intimate relationships of the PVS with meridian system and whether the PVS would be the physical basis of meridians?") are deeply studied and appropriately answered. Various pieces of knowledge are now combined to achieve a better understanding and to provide an acceptable explanation about the functions of such new system and to explain the functional path used by traditional Eastern medicine to cure diseases. Some possibilities to use this PVS for development of some innovative therapies to treat some diseases are also discussed (eg, pharmacopuncture as a new innovative drug delivery method that combines acupuncture therapy with medication by injecting pharmacological substances into target acupoints).

Emergence of a Metal-Insulator Transition and High-Temperature Charge-Density Waves in VSe2 at the Monolayer Limit.

Emergent phenomena driven by electronic reconstructions in oxide heterostructures have been intensively discussed. However, the role of these phenomena in shaping the electronic properties in van der Waals heterointerfaces has hitherto not been established. By reducing the material thickness and forming a heterointerface, we find two types of charge-ordering transitions in monolayer VSe2 on graphene substrates. Angle-resolved photoemission spectroscopy (ARPES) uncovers that Fermi-surface nesting becomes perfect in ML VSe2. Renormalization-group analysis confirms that imperfect nesting in three dimensions universally flows into perfect nesting in two dimensions. As a result, the charge-density wave-transition temperature is dramatically enhanced to a value of 350 K compared to the 105 K in bulk VSe2. More interestingly, ARPES and scanning tunneling microscopy measurements confirm an unexpected metal-insulator transition at 135 K that is driven by lattice distortions. The heterointerface plays an important role in driving this novel metal-insulator transition in the family of monolayer transition-metal dichalcogenides.

Atomistic study of the alloying behavior of crystalline SnSe1-xSx.

Recently, layered chalcogenide alloys (LCAs) have been extensively investigated for use in various practical applications by selectively controlling the amount of foreign components. However, the alloying behavior of layered chalcogenides has been rarely explored at the atomistic level. Here, we study the microstructural evolution of SnSe1-xSx alloys on the atomic scale by combining scanning tunneling microscopy (STM) measurements with first-principles density functional theory (DFT) calculations. STM topographic images suggest that S atoms substituted in SnSe1-xSx are not randomly distributed, but tend to form local SnS clusters. The degree of S atom alloying was quantitatively estimated to be about 60% from STM images, indicating that homo-atoms (S-S) are a preferred arrangement over hetero-atoms (S-Se). Our DFT calculations further confirmed that the mixing energy of random SnSe1-xSx alloys showed positive behavior over the whole S composition range considered. This result suggests that SnSe1-xSx has a tendency toward local phase segregation into SnSe and SnS rather than random alloys. We expect our atomistic study on the alloying behavior to provide important insight for fabricating optimal SnSe1-xSx alloys with high thermoelectric properties.

Temporal Change of Alcian Blue-Stained Primo Vascular System in Lymph Vessels of Rats.

This study aims to investigate the temporal change of a vascular system now known as the primo vascular system (PVS). We used Alcian blue (AB) dye for imaging the distribution of the PVS in lymphatic vessels. The target lymph vessels were chosen as they are easily accessible from the skin, and long-term observation is possible with intact physiological conditions due to a minimal surgical procedure. AB solution was injected into the inguinal lymph node and the target lymph vessels were located along the superficial epigastric vessels. The imaging system allowed processing for extraction of images showing changes in the AB intensity of the visualized PVS components. This newly developed procedure can be used for further study on various dynamic processes of PVS in lymph vessels.

A measurement of the maximal forces in plasmonic tweezers.

Plasmonic tweezers that are designed to trap nanoscale objects create many new possibilities for single-molecule targeted studies. Numerous novel designs of plasmonic nanostructures are proposed in order to attain stronger forces and weaker laser intensity. Most experiments have consisted only of immobilization observations--that is, particles stick when the laser is turned on and fall away when the laser is turned off. Studies of the exertable forces were only theoretical. A few studies have experimentally measured trap stiffness. However, as far as we know, no studies have addressed maximal forces. In this paper, we present a new experimental design in which the motion of the trapped particle can be monitored in either parallel or orthogonal directions to the plasmonic structure's symmetric axis. We measured maximal trapping force through such monitoring. Although stiffness would be useful for force-calibration or immobilization purposes, for which most plasmonic tweezers are used, we believe that the maximal endurable force is significant and thus, this paper presents this aspect.

Discovery of a novel fibrous tissue in the spinal pia mater by polarized light microscopy.

Abstract It is very well known that spinal meninges are composed of three layers, dura, arachnoid and pia mater, and that the main components of pia mater are collagen and reticular fibers. However, the distribution of those fibers has not been extensively investigated but just described as a mesh of fibers. In this study, we detected novel structures, which are composed of unidirectionally arranged fibers, in a rat spinal pia mater by using a polarized light microscope. They were seen as three parallel lines, one of which ran along a posterior spinal vein and the rest two of which ran along a pair of posterior spinal arteries. Histological analysis including Masson's trichrome, picrosirius-red staining, Gordon & Sweet's staining and immunohistochemistry with anti-collagen type 1 and 3 antibodies uncovered that they are mainly composed of collagen fibers and some reticular fibers. In addition, a putative primo vessel was detected in the novel fibrous tissue, which was proven out to be different from a blood vessel. In conclusion, we report a newly detected fibrous structure in the spinal pia mater, which may contribute to provide tensile force to the spinal meninges and to harbor the primo vascular system inside.

Emergence of two distinct phase transitions in monolayer CoSe2 on graphene.

Dimensional modifications play a crucial role in various applications, especially in the context of device miniaturization, giving rise to novel quantum phenomena. The many-body dynamics induced by dimensional modifications, including electron-electron, electron-phonon, electron-magnon and electron-plasmon coupling, are known to significantly affect the atomic and electronic properties of the materials. By reducing the dimensionality of orthorhombic CoSe2 and forming heterostructure with bilayer graphene using molecular beam epitaxy, we unveil the emergence of two types of phase transitions through angle-resolved photoemission spectroscopy and scanning tunneling microscopy measurements. We disclose that the 2 × 1 superstructure is associated with charge density wave induced by Fermi surface nesting, characterized by a transition temperature of 340 K. Additionally, another phase transition at temperature of 160 K based on temperature dependent gap evolution are observed with renormalized electronic structure induced by electron-boson coupling. These discoveries of the electronic and atomic modifications, influenced by electron-electron and electron-boson interactions, underscore that many-body physics play significant roles in understanding low-dimensional properties of non-van der Waals Co-chalcogenides and related heterostructures.

Quantum size effects on the work function of metallic thin film nanostructures.

In this paper, we present the direct observation of quantum size effects (QSE) on the work function in ultrathin Pb films. By using scanning tunneling microscopy and spectroscopy, we show that the very existence of quantum well states (QWS) in these ultrathin films profoundly affects the measured tunneling decay constant kappa, resulting in a very rich phenomenon of "quantum oscillations" in kappa as a function of thickness, L, and bias voltage, V(s). More specifically, we find that the phase of the quantum oscillations in kappa vs. L depends sensitively upon the bias voltage, which often results in a total phase reversal at different biases. On the other hand, at very low sample bias (|V(s)| < 0.03 V) the measurement of kappa vs. L accurately reflects the quantum size effect on the work function. In particular, the minima in the quantum oscillations of kappa vs. L occur at the locations where QWS cross the Fermi energy, thus directly unraveling the QSE on the work function in ultrathin films, which was predicted more than three decades ago. This further clarifies several contradictions regarding the relationship between the QWS locations and the work function.

Direct characterization of intrinsic defects in monolayer ReSe2 on graphene.

Understanding the characteristics of intrinsic defects in crystals is of great interest in many fields, from fundamental physics to applied materials science. Combined investigations of scanning tunneling microscopy/spectroscopy (STM/S) and density functional theory (DFT) are conducted to understand the nature of Se vacancy defects in monolayer (ML) ReSe2 grown on a graphene substrate. Among four possible Se vacancy sites, we identify the Se4 vacancy close to the Re layer by registry between STM topography and DFT simulated images. The Se4 vacancy is also thermodynamically favored in formation energy calculations, supporting its common observation via STM. dI/dV spectroscopy shows that the Se4 vacancy has a defect state at around -1.0 V, near the valence band maximum (EVBM). DOS calculations done for all four Se vacancies indicate that only the Se4 vacancy presents such a defect state near EVBM, confirming experimental observations. Our work provides valuable insights into the behavior of ML ReSe2/graphene heterojunctions containing naturally occurring Se vacancies, which may have strong implications in electronic device applications.

Controlling Spin-Orbit Coupling to Tailor Type-II Dirac Bands.

NiTe2, a type-II Dirac semimetal with a strongly tilted Dirac band, has been explored extensively to understand its intriguing topological properties. Here, using density functional theory calculations, we report that the strength of the spin-orbit coupling (SOC) in NiTe2 can be tuned by Se substitution. This results in negative shifts of the bulk Dirac point (BDP) while preserving the type-II Dirac band. Indeed, combined studies using scanning tunneling spectroscopy and angle-resolved photoemission spectroscopy confirm that the BDP in the NiTe2-xSex alloy moves from +0.1 eV (NiTe2) to -0.3 eV (NiTeSe) depending on the Se concentrations, indicating the effective tunability of type-II Dirac Fermions. Our results demonstrate an approach to tailor the type-II Dirac band in NiTe2 by controlling the SOC strength via chalcogen substitution. This approach can be applicable to different types of topological materials.

Interlayer Coupling and Ultrafast Hot Electron Transfer Dynamics in Metallic VSe2/Graphene van der Waals Heterostructures.

Atomically thin vanadium diselenide (VSe2) is a two-dimensional transition metal dichalcogenide exhibiting attractive properties due to its metallic 1T phase. With the recent development of methods to manufacture high-quality monolayer VSe2 on van der Waals materials, the outstanding properties of VSe2-based heterostructures have been widely studied for diverse applications. Dimensional reduction and interlayer coupling with a van der Waals substrate lead to its distinguishable characteristics from its bulk counterparts. However, only a few fundamental studies have investigated the interlayer coupling effects and hot electron transfer dynamics in VSe2 heterostructures. In this work, we reveal ultrafast and efficient interlayer hot electron transfer and interlayer coupling effects in VSe2/graphene heterostructures. Femtosecond time-resolved reflectivity measurements showed that hot electrons in VSe2 were transferred to graphene within a 100 fs time scale with high efficiency. Besides, coherent acoustic phonon dynamics indicated interlayer coupling in VSe2/graphene heterostructures and efficient thermal energy transfer to three-dimensional substrates. Our results provide valuable insights into the intriguing properties of metallic transition metal dichalcogenide heterostructures and motivate designing optoelectronic and photonic devices with tailored properties.

Novel polymorphic phase of two-dimensional VSe2: the 1T' structure and its lattice dynamics.

Polymorphisms allowing multiple structural phases are among the most fascinating properties of transition metal dichalcogenides (TMDs). Herein, the polymorphic 1T' phase and its lattice dynamics for bilayer VSe2 grown on epitaxial bilayer graphene are investigated via low temperature scanning tunneling microscopy (STM). The 1T' structure, mostly observed in group-6 TMDs, is unexpected in VSe2, which is a group-5 TMD. Emergence of the 1T' structure in bilayer VSe2 suggests the important roles of interface and layer configurations, providing new possibilities regarding the polymorphism of TMDs. Detailed topographical analysis elucidates the microscopic nature of the 1T' structure, confirming that Se-like and V-like surfaces can be resolved depending on the polarity of the sample bias. In addition, bilayer VSe2 can transit from a static state of the 1T' phase to a dynamic state consisting of lattice vibrations, triggered by tunneling current from the STM tip. Topography also shows hysteretic behavior during the static-dynamic transition, which is attributed to latent energy existing between the two states. The observed lattice dynamics involve vibrational motion of the Se atoms and the middle V atoms. Our observations will provide important information to establish in-depth understanding of the microscopic nature of 1T' structures and the polymorphism of two-dimensional TMDs.

Enhancement of ultraweak photon emission with 3 MHz ultrasonic irradiation on transplanted tumor tissues of mice.

We investigated photon emissions of various bio-samples which were induced by ultrasonic stimulation. It has been reported that ultrasonic stimulations induced the thermal excitation of the bio-tissues. After ultrasonic stimulation, any measurement of photon radiation in the visible spectral range has not been carried out yet. The instruments consisted of electronic devices for an ultrasonic generator of the frequency 3 MHz and a photomultiplier tube (PMT) system counting photons from bio-tissues. The transplanted tumor tissues of mice were prepared for the experiments and their liver and spleen tissues were also used for the controls. It was found that the continuous ultrasonic stimulations with the electrical power 2300 mW induced ultraweak photon emissions from the tumor tissues. The number of induced photon was dependent of the type of the tissues and the stimulation time intervals. The level of photon emission was increased from the mouse tumor exposed to the ultrasonic stimulations, and the changes were discriminated from those of the spleens and livers.

Analysis of H(c2)(θ,T) for Mg(B(1-x)C(x))(2) single crystals by using the dirty two-gap model.

To understand the effect of carbon doping on the superconductivity in MgB(2), we obtained the angle- and temperature-dependent upper critical fields [H(c2)(θ) and H(c2)(T)] for Mg(B(1-x)C(x))(2) single crystals (x = 0.06 and 0.1) from resistivity measurements while varying the temperature, the field, and the direction of the field. The detailed values of the diffusivity for two different directions for each σ-band and π-band were obtained to explain both the temperature- and the angle-dependent H(c2) by using the dirty-limit two-gap model. The induced impurity scattering of the σ-band and the π-band for both the ab-plane and the c-direction is studied.

Plasmonic Trapping and Release of Nanoparticles in a Monitoring Environment.

Plasmonic tweezers use surface plasmon polaritons to confine polarizable nanoscale objects. Among the various designs of plasmonic tweezers, only a few can observe immobilized particles. Moreover, a limited number of studies have experimentally measured the exertable forces on the particles. The designs can be classified as the protruding nanodisk type or the suppressed nanohole type. For the latter, microscopic observation is extremely challenging. In this paper, a new plasmonic tweezer system is introduced to monitor particles, both in directions parallel and orthogonal to the symmetric axis of a plasmonic nanohole structure. This feature enables us to observe the movement of each particle near the rim of the nanohole. Furthermore, we can quantitatively estimate the maximal trapping forces using a new fluidic channel.