Tunable spin injection and detection across a van der Waals interface.

Van der Waals heterostructures with two-dimensional magnets offer a magnetic junction with an atomically sharp and clean interface. This attribute ensures that the magnetic layers maintain their intrinsic spin-polarized electronic states and spin-flipping scattering processes at a minimum level, a trait that can expand spintronic device functionalities. Here, using a van der Waals assembly of ferromagnetic Fe3GeTe2 with non-magnetic hexagonal boron nitride and WSe2 layers, we demonstrate electrically tunable, highly transparent spin injection and detection across the van der Waals interfaces. By varying an electrical bias, the net spin polarization of the injected carriers can be modulated and reversed in polarity, which leads to sign changes of the tunnelling magnetoresistance. We attribute the spin polarization reversals to sizable contributions from high-energy localized spin states in the metallic ferromagnet, so far inaccessible in conventional magnetic junctions. Such tunability of the spin-valve operations opens a promising route for the electronic control of next-generation low-dimensional spintronic device applications.

Direct probing of phonon mode specific electron-phonon scatterings in two-dimensional semiconductor transition metal dichalcogenides.

Electron-phonon scatterings in solid-state systems are pivotal processes in determining many key physical quantities such as charge carrier mobilities and thermal conductivities. Here, we report direct probing of phonon mode specific electron-phonon scatterings in layered semiconducting transition metal dichalcogenides WSe2, MoSe2, WS2, and MoS2 through inelastic electron tunneling spectroscopy measurements, quantum transport simulations, and density functional calculation. We experimentally and theoretically characterize momentum-conserving single- and two-phonon electron-phonon scatterings involving up to as many as eight individual phonon modes in mono- and bilayer films, among which transverse, longitudinal acoustic and optical, and flexural optical phonons play significant roles in quantum charge flows. Moreover, the layer-number sensitive higher-order inelastic electron-phonon scatterings, which are confirmed to be generic in all four semiconducting layers, can be attributed to differing electronic structures, symmetry, and quantum interference effects during the scattering processes in the ultrathin semiconducting films.

Large Temperature-Independent Magnetoresistance without Gating Operation in Monolayer Graphene.

Temperature-independent magnetoresistance (TIMR) has been studied for applications in magnetic field sensors operating in wide temperature ranges. Graphene is considered as one of the best candidates for achieving nonsaturating and large TIMR through engineering disorders. Nevertheless, large TIMR has not been achieved in disordered graphene with intrinsic defects, such as chemical doping and atomic dislocations. In this work, by introducing extrinsic defects, we realize nonsaturating and large TIMR in monolayer graphene transferred on a BiFeO3 nanoisland array (G/BFO-NIA). Furthermore, the G/BFO-NIA device exhibits a significantly larger MR (∼250% under 9 T) than other materials without gating operation, demonstrating its application feasibility. It is shown that the large MR is a result of the coexistence of electrons and holes with almost the same density, and the observed TIMR originates from the temperature dependence of carrier transport in graphene and of the dielectric property of BFO-NIA.

The Effect of Mycophenolate Mofetil versus Cyclosporine as Combination Therapy with Low Dose Corticosteroids in High-risk Patients with Idiopathic Membranous Nephropathy: a Multicenter Randomized Trial.

BACKGROUND: Appropriate immunosuppressive therapy for patients with idiopathic membranous nephropathy (MN) remains controversial. The effect of mycophenolate mofetil (MMF) versus cyclosporine (CsA) combined with low-dose corticosteroids was evaluated in patients with idiopathic MN in a multi-center randomized trial (www.ClinicalTrials.gov NCT01282073). METHODS: A total of 39 biopsy-proven idiopathic MN patients with severe proteinuria were randomly assigned to receive MMF combined with low-dose corticosteroids (MMF group) versus CsA combined with low-dose corticosteroids (CsA group), respectively, and followed up for 48 weeks. Complete or partial remission rate of proteinuria and estimated glomerular filtration rate (eGFR) at 48 weeks were compared. RESULTS: The level of proteinuria at baseline and at 48 weeks was 8.9 ± 5.9 and 2.1 ± 3.1 g/day, respectively, in the MMF group compared to 8.4 ± 3.5 and 3.2 ± 5.7 g/day, respectively, in the CsA group. In total, 76.1% of the MMF group and 66.7% of the CsA group achieved remission at 48 weeks (95% confidence interval, -0.18 to 0.38). There was no difference in eGFR between the two groups. Anti-phospholipase A2 receptor Ab levels at baseline decreased at 48 weeks in the complete or partial remission group (P = 0.001), but were unchanged in the no-response group. There were no significant differences between the two groups in changes in the Gastrointestinal Symptom Rating Scale and Gastrointestinal Quality of Life Index scores from baseline to 48 weeks. CONCLUSION: In combination with low-dose corticosteroids, the effect of MMF may not be inferior to that of CsA in patients with idiopathic MN, with similar adverse effects including gastrointestinal symptoms. Trial registry at ClinicalTrials.gov (NCT01282073).

The Prevalence, Association, and Clinical Outcomes of Frailty in Maintenance Dialysis Patients.

OBJECTIVE: To investigate the clinical implications of frailty in chronic kidney disease patients undergoing maintenance hemodialysis and chronic peritoneal dialysis. DESIGN: In this prospective study, all of the participants completed the Short Form of the Kidney Disease Quality of Life questionnaire, Korean version, to determine their frailty phenotype. We also obtained blood chemistry and demographic data at enrollment. Data regarding the history of hospitalization and death were collected during the follow-up period. SUBJECTS: We recruited 1,658 patients (1,255 maintenance hemodialysis and 403 chronic peritoneal dialysis) from multidialysis units (n = 27). We excluded patients who had been hospitalized in the previous 3 months. MAIN OUTCOME MEASURES: Hospitalization and survival rate during study period. RESULTS: The participants' mean age was 55.2 ± 11.9 years old, and 55.2% were male. Among the participants, 34.8% were rated as frail and 45.7% as prefrail. Multivariate analysis demonstrated significant associations of frailty with age, comorbidity, disability, unemployment, higher body mass index, and a lower educational level. During the follow-up period (median 17.1 months), 608 patients (79 not frail, 250 prefrail, and 279 frail) were hospitalized, and 87 patients (10 not frail, 24 prefrail, and 53 frail) died (P < .001). Frailty was associated with hospitalization (adjusted hazard ratio, 1.80; 95% confidence interval: 1.38-2.36) and mortality (hazard ratio, 2.37, 95% confidence interval: 1.11-5.02). CONCLUSION: The frailty phenotype was common even in, prevalent end-stage renal disease patients on dialysis, and was significantly associated with higher rates of hospitalization and mortality.

Selector-free resistive switching memory cell based on BiFeO3 nano-island showing high resistance ratio and nonlinearity factor.

Highly nonlinear bistable current-voltage (I-V) characteristics are necessary in order to realize high density resistive random access memory (ReRAM) devices that are compatible with cross-point stack structures. Up to now, such I-V characteristics have been achieved by introducing complex device structures consisting of selection elements (selectors) and memory elements which are connected in series. In this study, we report bipolar resistive switching (RS) behaviours of nano-crystalline BiFeO3 (BFO) nano-islands grown on Nb-doped SrTiO3 substrates, with large ON/OFF ratio of 4,420. In addition, the BFO nano-islands exhibit asymmetric I-V characteristics with high nonlinearity factor of 1,100 in a low resistance state. Such selector-free RS behaviours are enabled by the mosaic structures and pinned downward ferroelectric polarization in the BFO nano-islands. The high resistance ratio and nonlinearity factor suggest that our BFO nano-islands can be extended to an N × N array of N = 3,740 corresponding to ~10(7) bits. Therefore, our BFO nano-island showing both high resistance ratio and nonlinearity factor offers a simple and promising building block of high density ReRAM.

Graphene/Pentacene Barristor with Ion-Gel Gate Dielectric: Flexible Ambipolar Transistor with High Mobility and On/Off Ratio.

High-quality channel layer is required for next-generation flexible electronic devices. Graphene is a good candidate due to its high carrier mobility and unique ambipolar transport characteristics but typically shows a low on/off ratio caused by gapless band structure. Popularly investigated organic semiconductors, such as pentacene, suffer from poor carrier mobility. Here, we propose a graphene/pentacene channel layer with high-k ion-gel gate dielectric. The graphene/pentacene device shows both high on/off ratio and carrier mobility as well as excellent mechanical flexibility. Most importantly, it reveals ambipolar behaviors and related negative differential resistance, which are controlled by external bias. Therefore, our graphene/pentacene barristor with ion-gel gate dielectric can offer various flexible device applications with high performances.

Detection of gamma-irradiation effect on DNA and protein using magnetic sensor and cyclic voltammetry.

In this study, a magnetic sensor utilizing Planar Hall Resistance (PHR) and cyclic Voltammetry (CV) for detecting the radiation effect was fabricated. Specifically, we applied in parallel a PHR sensor and CV device to monitor the irradiation effect on DNA and protein respectively. Through parallel measurements, we demonstrated that the PHR sensor and CV are sensitive enough to measure irradiation effect. The PHR voltage decreased by magnetic nanobead labeled DNA was slightly recovered after gamma ray irradiation. The behavior of cdk inhibitor protein p21 having a sandwich structure of Au/protein G/Ab/Ag/Ab was checked by monitoring the cyclic Voltammetry signal in analyzing the gamma ray irradiation effect.

Facile characterization of ripple domains on exfoliated graphene.

Ripples in graphene monolayers deposited on SiO(2)/Si wafer substrates were recently shown to give rise to friction anisotropy. High friction appears when the AFM tip slides in a direction perpendicular to the ripple crests and low friction when parallel. The direction of the ripple crest is, however, hard to determine as it is not visible in topographic images and requires elaborate measurements of friction as a function of angle. Here we report a simple method to characterize ripple crests by measuring the cantilever torsion signal while scanning in the non-conventional longitudinal direction (i.e., along the cantilever axis, as opposed to the usual friction measurement). The longitudinal torsion signal provides a much clearer ripple domain contrast than the conventional friction signal, while both signals show respective rotation angle dependences that can be explained using the torsion component of the normal reaction force exerted by the graphene ripples. We can also determine the ripple direction by comparing the contrast in torsion images obtained in longitudinal and lateral scans without sample rotation or complicated normalization.

Self-renewal of embryonic stem cells through culture on nanopattern polydimethylsiloxane substrate.

Embryonic stem (ES) cells can undergo continual proliferation and differentiation into cells of all somatic cell lineages in vitro; they are an unlimited cell source for regenerative medicine. However, techniques for maintaining undifferentiated ES cells are often inefficient and result in heterogeneous cell populations. Here, we determined effects of nanopattern polydimethylsiloxane (PDMS) as a culture substrate in promoting the self-renewal of mouse ES (mES) cells, compared to commercial plastic culture dishes. After many passages, mES cells efficiently maintained their undifferentiated state on nanopattern PDMS, but randomly differentiated on commercial plastic culture dishes, as indicated by partially altered morphologies and decreases in alkaline phosphatase activity and stage-specific expression of embryonic antigen-1. Under nanopattern PDMS conditions, we found increased activities of STAT3 and Akt, important proteins involved in maintaining the self-renewal of mES cells. The substrate-cell interactions also enhanced leukemia inhibitory factor (LIF)-downstream signaling and inhibited spontaneous differentiation, concomitant with reduced focal adhesion kinase (FAK) signaling. This reduction in FAK signaling was shown to be important for promoting mES cell self-renewal. Thus, our data demonstrates that nanopattern PDMS contributes to maintaining the self-renewal of mES cells and may be applicable in the large-scale production of homogeneously undifferentiated mES cells.

Bisphosphonate-induced Severe Hypocalcemia - A Case Report -.

Bisphosphonate generally seems to be safe, but hypocalcemia may occasionally develop in the course of bisphosphonate treatment. Hypocalcemia induced by bisphosphonate is usually mild and asymptomatic, but unrecognized or poorly treated hypocalcemia can lead to life-threatening state. A 78-year-old woman who had a history of hip arthroplasty and intravenous zoledronate treatment for femur neck fracture was presented to emergency department with altered mental status. It turned out that her symptom was due to severe hypocalcemia which was caused by intravenous zoledronate treatment. She also had renal dysfunction. She was treated by intravenous calcium gluconate and calcitriol administration. This case supports the need for evaluation of renal dysfunction, vitamin D deficiency and parathyroid gland dysfunction before bisphosphonate treatment and accurate monitoring of plasma calcium and creatinine levels. In addition, vitamin D and calcium supply during treatment with bisphosphonate is mandatory.

Nanoscale lithography on monolayer graphene using hydrogenation and oxidation.

Monolayer graphene is one of the most interesting materials applicable to next-generation electronic devices due to its transport properties. However, realization of graphene devices requires suitable nanoscale lithography as well as a method to open a band gap in monolayer graphene. Nanoscale hydrogenation and oxidation are promising methods to open an energy band gap by modification of surface structures and to fabricate nanostructures such as graphene nanoribbons (GNRs). Until now it has been difficult to fabricate nanoscale devices consisting of both hydrogenated and oxidized graphene because the hydrogenation of graphene requires a complicated process composed of large-scale chemical modification, nanoscale patterning, and etching. We report on nanoscale hydrogenation and oxidation of graphene under normal atmospheric conditions and at room temperature without etching, wet process, or even any gas treatment by controlling just an external bias through atomic force microscope lithography. Both the lithographically defined nanoscale hydrogenation and oxidation have been confirmed by micro-Raman spectroscopy measurements. Patterned hydrogenated and oxidized graphene show insulating behaviors, and their friction values are several times larger than those of graphene. These differences can be used for fabricating electronic or electromechanical devices based on graphene.

Friction anisotropy-driven domain imaging on exfoliated monolayer graphene.

Graphene produced by exfoliation has not been able to provide an ideal graphene with performance comparable to that predicted by theory, and structural and/or electronic defects have been proposed as one cause of reduced performance. We report the observation of domains on exfoliated monolayer graphene that differ by their friction characteristics, as measured by friction force microscopy. Angle-dependent scanning revealed friction anisotropy with a periodicity of 180° on each friction domain. The friction anisotropy decreased as the applied load increased. We propose that the domains arise from ripple distortions that give rise to anisotropic friction in each domain as a result of the anisotropic puckering of the graphene.

3,4-dideoxyglucosone-3-ene induces apoptosis in human peritoneal mesothelial cells.

OBJECTIVE: Glucose degradation products (GDPs) are formed during heat sterilization and storage of peritoneal dialysis (PD) fluids. 3,4-dideoxyglucosone-3-ene (3,4-DGE) has been identified as the most bioreactive GDP. 3,4-DGE induces apoptosis in leukocytes and renal tubular epithelial cells. Our aim was to evaluate the apoptotic effects of 3,4-DGE on human peritoneal mesothelial cells (HPMCs). METHODS: Primary cultured HPMCs were treated with 25 or 50 micromol/L 3,4-DGE. MTT assay was used to determine cell viability. Apoptosis was measured using TUNEL assay and flow cytometry. Expressions of procaspase-3, Bax, and Bcl-2 were estimated by Western blot. Activity of caspase-3 was measured and the effect of the caspase inhibitor zVAD-fmk (Z-Val-Ala-DL-Asp-fluoromethylketone) was evaluated by TUNEL assay. RESULTS: 3,4-DGE treatment accelerated cell death in HPMCs in a dose- and time-dependent manner. Treatment with 3,4-DGE (25 and 50 micromol/L) significantly increased apoptosis compared to control (p<0.05 and p<0.01 respectively) by TUNEL assay. Flow cytometry showed treatment with 50 micromol/L 3,4-DGE significantly increased apoptosis compared to control (p<0.05). Decreased expression of procaspase-3 and increased activity of caspase-3 were observed in the presence of 50 micromol/L 3,4-DGE compared to control and 25 micromol/L 3,4-DGE (p<0.05). 3,4-DGE-induced HPMC apoptosis was decreased after pretreatment with the pan-caspase inhibitor zVAD-fmk in the 50 micromol/L 3,4-DGE-treated group (p<0.001). The ratio of Bcl-2 to Bax expression was decreased in the 25 micromol/L and the 50 micromol/L 3,4-DGE-treated groups compared to control (p<0.05). CONCLUSIONS: 3,4-DGE promotes apoptosis in HPMCs by a caspase-related mechanism.