Electrons moving through a spatially periodic lattice potential develop a quantized energy spectrum consisting of discrete Bloch bands. In two dimensions, electrons moving through a magnetic field ...also develop a quantized energy spectrum, consisting of highly degenerate Landau energy levels. When subject to both a magnetic field and a periodic electrostatic potential, two-dimensional systems of electrons exhibit a self-similar recursive energy spectrum. Known as Hofstadter's butterfly, this complex spectrum results from an interplay between the characteristic lengths associated with the two quantizing fields, and is one of the first quantum fractals discovered in physics. In the decades since its prediction, experimental attempts to study this effect have been limited by difficulties in reconciling the two length scales. Typical atomic lattices (with periodicities of less than one nanometre) require unfeasibly large magnetic fields to reach the commensurability condition, and in artificially engineered structures (with periodicities greater than about 100 nanometres) the corresponding fields are too small to overcome disorder completely. Here we demonstrate that moiré superlattices arising in bilayer graphene coupled to hexagonal boron nitride provide a periodic modulation with ideal length scales of the order of ten nanometres, enabling unprecedented experimental access to the fractal spectrum. We confirm that quantum Hall features associated with the fractal gaps are described by two integer topological quantum numbers, and report evidence of their recursive structure. Observation of a Hofstadter spectrum in bilayer graphene means that it is possible to investigate emergent behaviour within a fractal energy landscape in a system with tunable internal degrees of freedom.
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DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Since the initial demonstration of the ability to experimentally isolate a single graphene sheet, a great deal of theoretical work has focused on explaining graphene's unusual ...carrier-density-dependent conductivity σ(n), and its minimum value (σmin) of nearly twice the quantum unit of conductance (4e2/h) (refs 1, 2, 3, 4, 5, 6). Potential explanations for such behaviour include short-range disorder, 'ripples' in graphene's atomic structure and the presence of charged impurities. Here, we conduct a systematic study of the last of these mechanisms, by monitoring changes in electronic characteristics of initially clean graphene as the density of charged impurities (nimp) is increased by depositing potassium atoms onto its surface in ultrahigh vacuum. At non-zero carrier density, charged-impurity scattering produces the widely observed linear dependence of σ(n). More significantly, we find that σmin occurs not at the carrier density that neutralizes nimp, but rather the carrier density at which the average impurity potential is zero. As nimp increases, σmin initially falls to a minimum value near 4e2/h. This indicates that σmin in the present experimental samples is governed not by the physics of the Dirac point singularity, but rather by carrier-density inhomogeneities induced by the potential of charged impurities.
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IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Printed Graphene Circuits Chen, J.-H.; Ishigami, M.; Jang, C. ...
Advanced materials (Weinheim),
11/2007, Volume:
19, Issue:
21
Journal Article
Peer reviewed
Open access
Flexible and transparent electronic devices with extremely high mobilities are fabricated from a graphene sheet, a single atomic layer of graphite, by using the transfer printing method. “Printed” ...graphene circuits achieve field effect mobilities of up to 10000 cm2/Vs at room temperature. Our printing technique is scaleable and a more chemically‐gentle process for fabricating high quality graphene, and nanoscale devices in general.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Aspartate transaminase–to–platelet ratio index (APRI) and fibrosis-4 (FIB-4) are well known as representative indirect serum biomarkers related to liver fibrosis. The usefulness of these markers for ...the diagnosis of liver fibrosis after liver transplantation (LT) in hepatitis C virus (HCV)–infected patients and the influence of splenectomy were investigated.
From June 2003 to May 2014, 31 HCV-infected patients who underwent LT and postoperative follow-up liver biopsies were included in this study. The association between liver fibrosis and serum biomarkers and the influence of splenectomy on APRI and FIB-4 were also investigated.
A total of 195 biopsy specimens were collected, and liver fibrosis was identified as: F0, 59.7%; F1, 34.1%; and F2, 6.3%. Both APRI and FIB-4 were significantly higher in patients who showed F1 and F2 in liver biopsy specimen than F0 (P values, .009 and .022, respectively); sensitivity and specificity of APRI were, respectively, 63.4% and 66.7%, and those of FIB-4 were 57.7% and 69.6%. In 11 patients (35.5%) who underwent splenectomy at the time of LT, the cutoff values for APRI and FIB-4 were 0.61 and 1.41, which were significantly lower than the corresponding values (1.00 and 3.64) of patients without splenectomy.
APRI and FIB-4 could effectively estimate liver fibrosis after LT for HCV-related liver disease. For LT patients with splenectomy, APRI and FIB-4 were also useful to estimate liver fibrosis, but the standard values should be adjusted lower than those for patients without splenectomy.
•We investigated the usefulness of the aspartate transaminase–to–platelet ratio index (APRI) and fibrosis-4 (FIB-4) for the diagnosis of liver fibrosis after liver transplantation (LT) in hepatitis C virus (HCV)–infected patients and the influence of splenectomy.•APRI and FIB-4 could effectively estimate liver fibrosis after LT for HCV-related liver disease.•For LT patients with splenectomy also, APRI and FIB-4 were useful to estimate liver fibrosis, but the standard values should be adjusted lower than those for patients without splenectomy.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Summary
Background
Acoustic radiation force impulse (ARFI) elastography is a non‐invasive method for measuring liver stiffness. However, there are no reports evaluating the value of ARFI elastography ...for liver fibrosis in chronic hepatitis C patients with a sustained virological response (SVR).
Aim
To investigate the diagnostic performance of ARFI elastography for the assessment of liver fibrosis in hepatitis C virus (HCV) infected patients with an SVR.
Methods
In this prospective study, we enrolled 336 patients: 121 HCV patients with an SVR (44.6% women) and 215 patients with HCV (47.9% women). ARFI elastography measurements of all patients were performed on the same day of liver biopsy.
Results
The diagnostic accuracies, expressed as areas under the receiver operating characteristic curves for ARFI elastography, in HCV patients with an SVR and those in patients with HCV were 0.818 and 0.875 for the diagnosis of significant fibrosis (≥F2), 0.909 and 0.888 for the diagnosis of severe fibrosis (≥F3), and 0.981 and 0.890 for the diagnosis of liver cirrhosis (F4), respectively. The optimum cut‐off values for ARFI elastography were 1.26 m/s for ≥F2, 1.31 m/s for ≥F3 and 1.49 m/s for F4 in HCV patients with an SVR. The liver stiffness values were lower in patients with SVR compared with those in patients with HCV at the same stage of fibrosis. The liver stiffness values were affected by the necroinflammatory activity and the time after SVR.
Conclusion
Acoustic radiation force impulse elastography is an acceptable method for predicting the severity of fibrosis in patients with hepatitis C virus and a sustained viral response.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
In order to test recently predicted ballistic nanofriction (ultra-low drag and enhanced lubricity) of gold nanocrystals on graphite at high surface speeds, we use the quartz microbalance technique to ...measure the impact of deposition of gold nanocrystals on graphene. We analyze our measurements of changes in frequency and dissipation induced by nanocrystals using a framework developed for friction of adatoms on various surfaces. We find the lubricity of gold nanocrystals on graphene to be even higher than that predicted for the ballistic nanofriction, confirming the enhanced lubricity predicted at high surface speeds. Our complementary molecular dynamics simulations indicate that such high lubricity is due to the interaction strength between gold nanocrystals and graphene being lower than previously assumed for gold nanocrystals and graphite.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The mammalian Hippo pathway is composed of mammalian Ste20-like (MST) kinases and large tumour suppressor (LATS) kinases. Upon the activation of the pathway, MST kinases phosphorylate and activate ...LATS kinases, which in turn phosphorylate transcriptional co-activators, yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ), recruit them to the cytosol from the nucleus and turn off cell cycle-promoting and anti-apoptotic gene transcriptions. Thus, the pathway restricts cell overgrowth and prevents tumourigenesis. Although a high cell density and stress signallings are known to activate the pathway, no specific stimulators are so far reported. As the dysfunction of the pathway is frequent in human cancers and correlates with poor prognosis, it is important to find out reagents that stimulate the pathway for not only basic research but also clinical medicine. We here developed a cell-based method of screening reagents that induce the recruitment of YAP to the cytosol. Using this method, we found that dobutamine inhibits the YAP-dependent gene transcription. Contrary to our expectations, the effect of dobutamine is independent of the Hippo pathway but our method opens the possibility to discover Hippo pathway stimulators or Hippo-independent YAP inhibitors.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
A simplified arc-method is presented which allows for the
continuous synthesis of multi-walled carbon nanotubes. In its basic form, the method requires only a dc power supply, a graphite electrode, ...and a container of liquid nitrogen with no need for pumps, seals, water-cooled vacuum chambers, or purge-gas handling systems. High-quality nanotubes are produced in high yield. The system is easily adaptable to produce large quantities of nanotubes continuously without interruptions for electrode replacement, chamber cleaning, or gas purging.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
9.
Diffusive charge transport in graphene on SiO2 CHEN, J.-H; JANG, C; ISHIGAMI, M ...
Solid state communications,
07/2009, Volume:
149, Issue:
27-28
Conference Proceeding, Journal Article
Peer reviewed
Open access
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Abstract Background To understand the impact of psychologic variables on donor quality of life, we studied long-term data on postoperative psychiatric complications in living liver donors. This study ...is a focused psychological investigation of diagnoses, treatments, and long-term clinical courses of living liver donors with psychiatric complications. Methods Of the 142 donors who underwent live-donor liver transplantation at Nagoya University Hospital between April 2004 and July 2014, we investigated those without a history of mental illness who had developed such illness after transplantation and required psychiatric treatment. Results A total of 6 (4.2%) donors developed the following psychiatric complications after transplantation: major depressive disorder (n = 2), panic disorder (n = 2), conversion disorder (n = 1), and substance use disorder (n = 1). Concerning psychiatric treatment, all donors received antianxiety drugs, 3 took antidepressants, and supportive psychiatric therapy was concomitantly provided to all subjects. The average treatment period was 53.3 months. Regarding subject outcomes, 3 donors achieved remission, and the other 3 continued treatment. All subjects showed improvement in Global Assessment of Functioning Scale. Conclusion It is important to accurately diagnose postoperative psychiatric complications and provide long-term treatment in close coordination with transplant surgeons.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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