Symmetry Engineering in Twisted Bilayer WTe2

The fabrication of artificial structures using a twisted van der Waals assembly has been a key technique for recent advancements in the research of two-dimensional (2D) materials. To date, various exotic phenomena have been observed thanks to the modified electron correlation or moiré structure controlled by the twist angle. However, the twisted van der Waals assembly has further potential to modulate the physical properties by controlling the symmetry. In this study, we fabricated twisted bilayer WTe2 and demonstrated that the twist angle successfully controls the spatial inversion symmetry and hence the spin splitting in the band structure. Our results reveal the further potential of a twisted van der Waals assembly, suggesting the feasibility of pursuing new physical phenomena in 2D materials based on the control of symmetry.

Super-Ballistic Width Dependence of Thermal Conductivity in Graphite Nanoribbons and Microribbons

The super-ballistic temperature dependence of thermal conductivity, facilitated by collective phonons, has been widely studied. It has been claimed to be unambiguous evidence for hydrodynamic phonon transport in solids. Alternatively, hydrodynamic thermal conduction is predicted to be as strongly dependent on the width of the structure as is fluid flow, while its direct demonstration remains an unexplored challenge. In this work, we experimentally measured thermal conductivity in several graphite ribbon structures with different widths, from 300 nm to 1.2 µm, and studied its width dependence in a wide temperature range of 10-300 K. We observed enhanced width dependence of the thermal conductivity in the hydrodynamic window of 75 K compared to that in the ballistic limit, which provides indispensable evidence for phonon hydrodynamic transport from the perspective of peculiar width dependence. This will help to find the missing piece to complete the puzzle of phonon hydrodynamics, and guide future attempts at efficient heat dissipation in advanced electronic devices.

Observation of phonon Poiseuille flow in isotopically purified graphite ribbons

In recent times, the unique collective transport physics of phonon hydrodynamics motivates theoreticians and experimentalists to explore it in micro- and nanoscale and at elevated temperatures. Graphitic materials have been predicted to facilitate hydrodynamic heat transport with their intrinsically strong normal scattering. However, owing to the experimental difficulties and vague theoretical understanding, the observation of phonon Poiseuille flow in graphitic systems remains challenging. In this study, based on a microscale experimental platform and the pertinent occurrence criterion in anisotropic solids, we demonstrate the existence of the phonon Poiseuille flow in a 5.5 μm-wide, suspended and isotopically purified graphite ribbon up to a temperature of 90 K. Our observation is well supported by our theoretical model based on a kinetic theory with fully first-principles inputs. Thus, this study paves the way for deeper insight into phonon hydrodynamics and cutting-edge heat manipulating applications.

All-dry flip-over stacking of van der Waals junctions of 2D materials using polyvinyl chloride

We demonstrated an all-dry polymer-to-polymer transfer technique for two-dimensional (2D) crystal flakes using a polyvinyl chloride (PVC) layer deposited on a piece of polydimethylsiloxane (PDMS). Unexpectedly, the pickup/release temperatures were modified in wider temperature range simply by changing the thickness of the PVC layer than changing the plasticizer ratio. Utilizing the difference in the pickup/release temperatures depending on the PVC film thickness, 2D flakes were transferred from a thicker PVC film to a thinner one. This polymer-to-polymer transfer technique can be utilized to flip over van der Waals heterostructures. As a demonstration, we fabricated a mountain-like stacked structure of hexagonal boron nitride flakes using the flip-over stacking technique. Finally, we compared the results of thermomechanical analysis with the pickup/release temperatures of the PVC/PDMS stamp. The PVC was revealed to be at the glass transition and in the viscoelastic flow regimes when the 2D flakes were picked up and dry released, respectively. Our polymer-to-polymer transfer method facilitates flip-over van der Waals stacking in an all-dry manner, expanding the possibility of 2D materials device fabrications.

Dry pick-and-flip assembly of van der Waals heterostructures for microfocus angle-resolved photoemission spectroscopy

We present a dry pick-and-flip assembly technique for angle-resolved photoemission spectroscopy (ARPES) of van der Waals heterostructures. By combining Elvacite2552C acrylic resin and 1-ethyl-3-methylimidazolium ionic liquid, we prepared polymers with glass transition temperatures (T_g) ranging from 37 to 100 ℃. The adhesion of the polymer to the 2D crystals was enhanced at \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${T}_{\text{g}}$$\end{document}Tg. By utilizing the difference in \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${T}_{\text{g}}$$\end{document}Tg, a 2D heterostructure can be transferred from a high-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${T}_{\text{g}}$$\end{document}Tg polymer to a lower-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${T}_{\text{g}}$$\end{document}Tg polymer, which enables flipping its surface upside down. This process is suitable for assembling heterostructures for ARPES, where the top capping layer should be monolayer graphene. The laser-based micro-focused ARPES measurements of 5-layer WTe₂, 3-layer MoTe₂, 2-layer WTe₂/few-layer Cr₂Ge₂Te₆, and twisted double bilayer WTe₂ demonstrate that this process can be utilized as a versatile sample fabrication method for investigating the energy spectra of 2D heterostructures.

Resonant Tunneling between Quantized Subbands in van der Waals Double Quantum Well Structure Based on Few-Layer WSe2

We demonstrate van der Waals double quantum well (vDQW) devices based on few-layer WSe₂ quantum wells and a few-layer h-BN tunnel barrier. Due to the strong out-of-plane confinement, an exfoliated WSe₂ exhibits quantized subband states at the Γ point in its valence band. Here, we report resonant tunneling and negative differential resistance in vDQW at room temperature owing to momentum- and energy-conserved tunneling between the quantized subbands in each well. Compared to single quantum well (QW) devices with only one QW layer possessing quantized subbands, superior current peak-to-valley ratios were obtained for the DQWs. Our findings suggest a new direction for utilizing few-layer-thick transition metal dichalcogenides in subband QW devices, bridging the gap between two-dimensional materials and state-of-the-art semiconductor QW electronics.

Quasiparticle Nodal Plane in the Fulde-Ferrell-Larkin-Ovchinnikov State of FeSe

The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, characterized by Cooper pairs condensed at finite momentum, has been a long-sought state that remains unresolved in many classes of fermionic systems, including superconductors and ultracold atoms. A fascinating aspect of the FFLO state is the emergence of periodic nodal planes in real space, but its observation is still lacking. Here we investigate the superconducting order parameter at high magnetic fields H applied perpendicular to the ab plane in a high-purity single crystal of FeSe. The heat capacity and magnetic torque provide thermodynamic evidence for a distinct superconducting phase at the low-temperature/high-field corner of the phase diagram. Despite the bulk superconductivity, spectroscopic-imaging scanning tunneling microscopy performed on the same crystal demonstrates that the order parameter vanishes at the surface upon entering the high-field phase. These results provide the first demonstration of a pinned planar node perpendicular to H, which is consistent with a putative FFLO state.

Resonant Tunneling Due to van der Waals Quantum-Well States of Few-Layer WSe2 in WSe2/h-BN/p+-MoS2 Junction

Few-layer transition metal dichalcogenides (TMDs) exhibit out-of-plane wave function confinement with subband quantization. This phenomenon is totally absent in monolayer crystals and is regarded as resulting from a naturally existing van der Waals quantum-well state. Because the energy separation between the subbands corresponds to the infrared wavelength range, few-layer TMDs are attractive for their potential to facilitate the application of TMD semiconductors as infrared photodetectors and emitters. Here, we report a few-layer WSe₂/h-BN tunnel barrier/multilayer p⁺-MoS₂ tunnel junction to access the quantized subbands of few-layer WSe₂ via tunneling spectroscopy measurements. Resonant tunneling and a negative differential resistance were observed when the top of the valence band Γ-point of p⁺-MoS₂ was energetically aligned with one of the empty subbands at the Γ-point of few-layer WSe₂. These results demonstrate a critical step toward the utilization of subband quantization in few-layer TMD materials for infrared optoelectronics applications.

Emergence of orbital angular moment at van Hove singularity in graphene/h-BN moiré superlattice

Bloch electrons lacking inversion symmetry exhibit orbital magnetic moments owing to the rotation around their center of mass; this moment induces a valley splitting in a magnetic field. For the graphene/h-BN moiré superlattice, inversion symmetry is broken by the h-BN. The superlattice potential generates a series of Dirac points (DPs) and van Hove singularities (vHSs) within an experimentally accessible low energy state, providing a platform to study orbital moments with respect to band structure. In this work, theoretical calculations and magnetothermoelectric measurements are combined to reveal the emergence of an orbital magnetic moment at vHSs in graphene/h-BN moiré superlattices. The thermoelectric signal for the vHS at the low energy side of the hole-side secondary DP exhibited significant magnetic field-induced valley splitting with an effective g-factor of approximately 130; splitting for other vHSs was negligible. This was attributed to the emergence of an orbital magnetic moment at the second vHS at the hole-side.

Cyclotron Resonance Study of Monolayer Graphene under Double Moiré Potentials

We report the first cyclotron resonance study of monolayer graphene under double-moiré potentials in which the crystal axis of graphene is nearly aligned to those of both the top and bottom hexagonal boron nitride (h-BN) layers. Under mid-infrared light irradiation, we observe cyclotron resonance absorption with the following unique features: (1) cyclotron resonance magnetic field B_CR is entirely different from that of nonaligned monolayer graphene, (2) B_CR exhibits strong electron-hole asymmetry, and (3) splitting of B_CR is observed for |ν| < 1, with the split maximum at |ν| = 1, resulting in eyeglass-shaped trajectories. These features are well explained by considering the large bandgap induced by the double moiré potentials, the electron-hole asymmetry in the Fermi velocity, and the Fermi-level-dependent enhancement of spin gaps, which suggests a large electron-electron correlation contribution in this system.

3D Manipulation of 2D Materials Using Microdome Polymer

We demonstrate 3D mechanical manipulations, such as sliding, rotating, folding, flipping, and exfoliating, of 2D materials using a microdome polymer (MDP) via in situ real-time observation with an optical microscope. A dimethylpolysiloxane (PDMS)-based MDP is covered with a poly(vinyl chloride) (PVC) adhesion layer. This PVC-MDP structure enables us to achieve small and adjustable contact areas between the PVC-MDP and a 2D-material flake, which is typically between ∼10 and ∼100 μm in diameter. The adhesion between the PVC polymer and 2D materials is fully tunable with temperature: Strong adhesion at ∼70 °C allows pick-up of the 2D material, and release occurs at ∼130 °C when the adhesion is weak. Thus the PVC-MDP functions as a point-of-contact manipulator for 2D materials, permitting the 3D manipulation of 2D-material flakes. Our method could facilitate the expansion of van der Waals heterostructure fabrication technology and the development of preparation techniques for more complex 3D structures.

Scalable Majorana vortex modes in iron-based superconductors

The iron-based superconductor FeTe x Se1-x is one of the material candidates hosting Majorana vortex modes residing in the vortex cores. It has been observed by recent scanning tunneling spectroscopy measurement that the fraction of vortex cores having zero-bias peaks decreases with increasing magnetic field on the surface of FeTe x Se1-x . The hybridization of two Majorana vortex modes cannot simply explain this phenomenon. We construct a three-dimensional tight-binding model simulating the physics of over a hundred Majorana vortex modes in FeTe x Se1-x . Our simulation shows that the Majorana hybridization and disordered vortex distribution can explain the decreasing fraction of the zero-bias peaks observed in the experiment; the statistics of the energy peaks off zero energy in our Majorana simulation are in agreement with the experiment. These agreements lead to an important indication of scalable Majorana vortex modes in FeTe x Se1-x . Thus, FeTe x Se1-x can be one promising platform having scalable Majorana qubits for quantum computing.

Hexagonal Boron Nitride Synthesized at Atmospheric Pressure Using Metal Alloy Solvents: Evaluation as a Substrate for 2D Materials

Hexagonal boron nitride (h-BN) synthesized under high pressure and high temperature (HPHT) has been used worldwide in two-dimensional (2D) materials research as an essential material for constructing van der Waals heterostructures. Here, we study h-BN synthesized with another method, i.e., via synthesis at atmospheric pressure and high temperature (APHT) using a metal alloy solvent. First, we examine the APHT h-BN in a bulk crystal form using cathodoluminescence and find that it does not have carbon-rich domains that inevitably exist in a core region of all the HPHT h-BN crystals. Next, we statistically compare the size of the crystal flakes exfoliated on a SiO₂/Si substrate from APHT and HPHT h-BN crystals by employing our automated 2D material searching system. Finally, we provide direct evidence that APHT h-BN can serve as a high-quality substrate for 2D materials by demonstrating high carrier mobility, ballistic transport, and Hofstadter butterfly in graphene and photoluminescence in WS₂.

Electrical Control of Cyclotron Resonance in Dual-Gated Trilayer Graphene

Landau levels (LLs) of ABA-stacked trilayer graphene (TLG) are described as the combination of monolayer graphene-like LLs and bilayer graphene-like LLs. They are extremely sensitive to the applied perpendicular electric displacement field D. Here, we demonstrate the electrical control of cyclotron resonance (CR) in a dual-gated ABA-stacked TLG. Under the irradiation of mid-infrared light, we observed the photovoltage induced by the CR absorption through the photothermoelectric effect. The resonant magnetic field in CR is changed by applying D while keeping the carrier density constant. Numerical simulations based on the tight-binding model complement the experimental observations. We believe that the present study provides a boost to graphene-based photodetectors and photoemitters with an electrically tunable wavelength in mid-infrared to terahertz spectral ranges.

Carbon-Rich Domain in Hexagonal Boron Nitride: Carrier Mobility Degradation and Anomalous Bending of the Landau Fan Diagram in Adjacent Graphene

Hexagonal boron nitride (h-BN) crystals grown under ultrahigh pressures and ultrahigh temperatures exhibit a high crystallinity and are used throughout the world as ideal substrates and insulating layers in van der Waals heterostructures. However, in their central region, these crystals have domains which contain a significant density of carbon impurities. In this study, we utilized cathodoluminescence and far-ultraviolet photoluminescence to reveal that the carbon (C)-rich domain can exist even after exfoliation. Then, we studied the carrier transport of graphene in h-BN/graphene/h-BN van der Waals heterostructures, precisely arranging the graphene to straddle the border of the C-rich domain in h-BN. We found that the carrier mobility of graphene on the C-rich h-BN domain was significantly suppressed. In addition, characteristic bending of the Landau fan diagram was observed on the electron-doped side. These results suggest that the C-rich domain in h-BN forms an impurity level and induces extrinsic carrier scattering into adjacent graphene.

Zero-energy vortex bound state in the superconducting topological surface state of Fe(Se,Te)

Majorana quasiparticles in condensed matter are important for topological quantum computing^1-3, but remain elusive. Vortex cores of topological superconductors may accommodate Majorana quasiparticles that appear as the Majorana bound state (MBS) at zero energy^4,5. The iron-based superconductor Fe(Se,Te) possesses a superconducting topological surface state^6-9 that was investigated by scanning tunnelling microscopy (STM) studies, which suggest such a zero-energy vortex bound state (ZVBS)^10,11. Here we present ultrahigh energy-resolution spectroscopic imaging (SI)-STM to clarify the nature of the vortex bound states in Fe(Se,Te). We found the ZVBS at 0 ± 20 μeV, which constrained its MBS origin, and showed that some vortices host the ZVBS but others do not. We show that the fraction of vortices hosting the ZVBS decreases with increasing magnetic field and that local quenched disorders are not related to the ZVBS. Our observations elucidate the necessary conditions to realize the ZVBS, which paves the way towards controllable Majorana quasiparticles.

A scanning tunneling microscope for spectroscopic imaging below 90 mK in magnetic fields up to 17.5 T

We describe the development and performance of an ultra-high vacuum scanning tunneling microscope working under combined extreme conditions of ultra-low temperatures and high magnetic fields. We combined a top-loading dilution refrigerator and a standard bucket dewar with a bottom-loading superconducting magnet to achieve 4.5 days operating time, which is long enough to perform various spectroscopic-imaging measurements. To bring the effective electron temperature closer to the mixing-chamber temperature, we paid particular attention to filtering out radio-frequency noise, as well as enhancing the thermal link between the microscope unit and the mixing chamber. We estimated the lowest effective electron temperature to be below 90 mK by measuring the superconducting-gap spectrum of aluminum. We confirmed the long-term stability of the spectroscopic-imaging measurement by visualizing superconducting vortices in the cuprate superconductor Bi₂Sr₂CaCu₂O_8+δ .

Autonomous robotic searching and assembly of two-dimensional crystals to build van der Waals superlattices

Van der Waals heterostructures are comprised of stacked atomically thin two-dimensional crystals and serve as novel materials providing unprecedented properties. However, the random natures in positions and shapes of exfoliated two-dimensional crystals have required the repetitive manual tasks of optical microscopy-based searching and mechanical transferring, thereby severely limiting the complexity of heterostructures. To solve the problem, here we develop a robotic system that searches exfoliated two-dimensional crystals and assembles them into superlattices inside the glovebox. The system can autonomously detect 400 monolayer graphene flakes per hour with a small error rate (<7%) and stack four cycles of the designated two-dimensional crystals per hour with few minutes of human intervention for each stack cycle. The system enabled fabrication of the superlattice consisting of 29 alternating layers of the graphene and the hexagonal boron nitride. This capacity provides a scalable approach for prototyping a variety of van der Waals superlattices.

Basic Studies of Various 99mTc-Labelled Renal Agents and Clinical Application of 99mTc-Malate

Various renal imaging agents that were reported in the past and a new agent, 99mTc-malate as well as 99mTc-cystein acetazolamide complex were prepared using electrolysis and electrochemical methods. These were studied for their labelling efficiency. After animal experiments with selected 99mTc-com- pounds, 99mTc-rnalate proved to be sufficient for renal imaging with adequate concentration. 99mTcmalate differs from other renal imaging agents in the utilization of endogeneous metabolic product.

The first half time of 99mTc-malate in humans is 17 minutes, on the average, and the urinary excretion rate of 99mTc-malate is 36±6.05% in 1 hour after intravenous administration, 44 ± 3.41% in 2 hours and 50 + 5.62% in 3 hours.

In our 40 clinical experiences of 99m-Tc-rnalate, most cases demonstrated quite clear renal images in the serial scintiphotos except cases whose serum creatinines were over 4.5 mg/dl.

Intersubband Landau Level Couplings Induced by In-Plane Magnetic Fields in Trilayer Graphene

We observed broken-symmetry quantum Hall effects and level crossings between spin- and valley- resolved Landau levels (LLs) in Bernal stacked trilayer graphene. When the magnetic field was tilted with respect to the sample normal from 0° to 66°, the LL crossings formed at intersections of zeroth and second LLs from monolayer-graphene-like and bilayer-graphene-like subbands, respectively, exhibited a sequence of transitions. The results indicate the LLs from different subbands are coupled by in-plane magnetic fields (B_{∥}), which was explained by developing the tight-binding model Hamiltonian of trilayer graphene under B_{∥}.

Full-gap superconductivity in spin-polarised surface states of topological semimetal β-PdBi2

A bulk superconductor possessing a topological surface state at the Fermi level is a promising system to realise long-sought topological superconductivity. Although several candidate materials have been proposed, experimental demonstrations concurrently exploring spin textures and superconductivity at the surface have remained elusive. Here we perform spectroscopic-imaging scanning tunnelling microscopy on the centrosymmetric superconductor β-PdBi2 that hosts a topological surface state. By combining first-principles electronic-structure calculations and quasiparticle interference experiments, we determine the spin textures at the surface, and show not only the topological surface state but also all other surface bands exhibit spin polarisations parallel to the surface. We find that the superconducting gap fully opens in all the spin-polarised surface states. This behaviour is consistent with a possible spin-triplet order parameter expected for such in-plane spin textures, but the observed superconducting gap amplitude is comparable to that of the bulk, suggesting that the spin-singlet component is predominant in β-PdBi2.Although several materials have been proposed as topological superconductors, spin textures and superconductivity at the surface remain elusive. Here, Iwaya et al. determine the spin textures at the surface of a superconductor β-PdBi2 and find the superconducting gap opening in all spin-polarised surface states.

Top-down assessment of the Asian carbon budget since the mid 1990s

Increasing atmospheric carbon dioxide (CO₂) is the principal driver of anthropogenic climate change. Asia is an important region for the global carbon budget, with 4 of the world's 10 largest national emitters of CO₂. Using an ensemble of seven atmospheric inverse systems, we estimated land biosphere fluxes (natural, land-use change and fires) based on atmospheric observations of CO₂ concentration. The Asian land biosphere was a net sink of −0.46 (−0.70–0.24) PgC per year (median and range) for 1996–2012 and was mostly located in East Asia, while in South and Southeast Asia the land biosphere was close to carbon neutral. In East Asia, the annual CO₂ sink increased between 1996–2001 and 2008–2012 by 0.56 (0.30–0.81) PgC, accounting for ∼35% of the increase in the global land biosphere sink. Uncertainty in the fossil fuel emissions contributes significantly (32%) to the uncertainty in land biosphere sink change.

Land biosphere uptake of carbon is important in mitigating the anthropogenic increase in atmospheric CO₂ and its climate forcing. Here, the authors show that land biosphere uptake of carbon in Asia has increased substantially since the mid 1990s, likely owing to reforestation and regional climate change.

Supercurrent in van der Waals Josephson junction

Supercurrent flow between two superconductors with different order parameters, a phenomenon known as the Josephson effect, can be achieved by inserting a non-superconducting material between two superconductors to decouple their wavefunctions. These Josephson junctions have been employed in fields ranging from digital to quantum electronics, yet their functionality is limited by the interface quality and use of non-superconducting material. Here we show that by exfoliating a layered dichalcogenide (NbSe₂) superconductor, the van der Waals (vdW) contact between the cleaved surfaces can instead be used to construct a Josephson junction. This is made possible by recent advances in vdW heterostructure technology, with an atomically flat vdW interface free of oxidation and inter-diffusion achieved by eliminating all heat treatment during junction preparation. Here we demonstrate that this artificially created vdW interface provides sufficient decoupling of the wavefunctions of the two NbSe₂ crystals, with the vdW Josephson junction exhibiting a high supercurrent transparency.

Van der Waals heterostructures, made of stacked two-dimensional materials, hold promise for modern electronics. Here, the authors build van der Waals junction between superconducting two-dimensional materials and reveal that the junction works as Josephson junction.

Cubic Rashba spin-orbit interaction of a two-dimensional hole gas in a strained-Ge/SiGe quantum well

The spin-orbit interaction (SOI) of a two-dimensional hole gas in the inversion symmetric semiconductor Ge is studied in a strained-Ge/SiGe quantum well structure. We observe weak antilocalization (WAL) in the magnetoconductivity measurement, revealing that the WAL feature can be fully described by the k-cubic Rashba SOI theory. Furthermore, we demonstrate electric field control of the Rashba SOI. Our findings reveal that the heavy hole (HH) in strained Ge is a purely cubic Rashba system, which is consistent with the spin angular momentum m(j) = ± 3/2 nature of the HH wave function.

Anti-aging Effects of Co-enzyme Q10 on Periodontal Tissues

Oxidative stress is associated with age-related reactions. The anti-oxidative effects of a reduced form of co-enzyme Q10 (rCoQ10) suppress oxidative stress, which may contribute to the prevention of age-related inflammatory reactions. We examined the effects of topically applied rCoQ10 on periodontal inflammatory reactions in a rat aging model. Male Fischer 344 rats, 2 (n = 6) and 4 mos (n = 18) of age, were used. All of the two-month-old rats and 6 of the four-month-old rats were sacrificed and 12 remaining four-month-old rats received topically applied ointment with or without 1% rCoQ10 on the gingival surface until they reached 6 mos of age. The rats showed an age-dependent increase in circulating oxidative stress. RCoQ10 decreased oxidative DNA damage and tartrate-resistant acid-phosphatase-positive osteoclasts in the periodontal tissue at 6 mos of age as compared with the control. The same conditions lowered gene expression of caspase-1 and interleukin-1β in the periodontal tissue. Furthermore, Nod-like receptor protein 3 inflammasomes were less activated in periodontal tissues from rCoQ10-treated rats as compared with the control rats. Our results suggest that rCoQ10 suppresses age-related inflammatory reactions and osteoclast differentiation by inhibiting oxidative stress.

Distribution of pituitary adenylate cyclase-activating polypeptide (PACAP) in the human testis and in testicular germ cell tumors

Pituitary adenylate cyclase-activating peptide (PACAP) is a neuropeptide expressed in the central nervous system and peripheral organs. Previous studies revealed the role and distribution of PACAP in the rodent testis, however, its presence in the human testis and in testicular germ cell tumors is not known. We used RT-PCR and immunohistological observations to investigate whether human testicular tissue and testicular germ cell tumors contain PACAP. The mRNAs for PACAP and its receptors were detected in total RNA extracted from human testes. PACAP immunoreactivity was observed in spermatogonia and spermatids from normal testes. In contrast, diffuse PACAP immunopositivity was observed in seminoma tumor cells, while only faint immunoreactivity was observed in embryonal carcinoma cells. Our data suggest that PACAP may play a role in human spermatogenesis and in testicular germ cell tumor development.

Boundary scattering in ballistic graphene

We report magnetotransport measurements in ballistic graphene mesoscopic wires where the charge carrier mean free path is comparable to the wire width W. Magnetoresistance curves show characteristic peak structures where the peak field scales with the ratio of cyclotron radius R(c) and wire width W as W/R(c)=0.9±0.1, due to diffusive boundary scattering. The obtained proportionality constant between R(c) and W differs from that of a classical semiconductor two-dimensional electron system in which W/R(c)=0.55.

Rapamycin causes upregulation of autophagy and impairs islets function both in vitro and in vivo

Autophagy is a lysosomal degradation process of redundant or faulty cell components in normal cells. However, certain diseases are associated with dysfunctional autophagy. Rapamycin, a major immunosuppressant used in islet transplantation, is an inhibitor of mammalian target of rapamycin and is known to cause induction of autophagy. The objective of this study was to evaluate the in vitro and in vivo effects of rapamycin on pancreatic β cells. Rapamycin induced upregulation of autophagy in both cultured isolated islets and pancreatic β cells of green fluorescent protein-microtubule-associated protein 1 light chain 3 transgenic mice. Rapamycin reduced the viability of isolated β cells and down-regulated their insulin function, both in vitro and in vivo. In addition, rapamycin increased the percentages of apoptotic β cells and dead cells in both isolated and in vivo intact islets. Treatment with 3-methyladenine, an inhibitor of autophagy, abrogated the effects of rapamycin and restored β-cell function in both in vitro experiments and animal experiments. We conclude that rapamycin-induced islet dysfunction is mediated through upregulation of autophagy, with associated downregulation of insulin production and apoptosis of β cells. The results also showed that the use of an autophagy inhibitor abrogated these effects and promoted islet function and survival. The study findings suggest that targeting the autophagy pathway could be beneficial in promoting islet graft survival after transplantation.

Atomic force microscopy based tunable local anodic oxidation of graphene

We have fabricated graphene/graphene oxide/graphene (G/GO/G) junctions by local anodic oxidation lithography using atomic force microscopy (AFM). The conductance of the G/GO/G junction decreased with the bias voltage applied to the AFM cantilever V(tip). For G/GO/G junctions fabricated with large and small |V(tip)|. GO was semi-insulating and semiconducting, respectively. AFM-based LAO lithography can be used to locally oxidize graphene with various oxidation levels and achieve tunability from semiconducting to semi-insulating GO.