Toward Quantitative Electrodeposition via In Situ Liquid Phase Transmission Electron Microscopy: Studying Electroplated Zinc Using Basic Image Processing and 4D STEM

High energy density electrochemical systems such as metal batteries suffer from uncontrollable dendrite growth on cycling, which can severely compromise battery safety and longevity. This originates from the thermodynamic preference of metal nucleation on electrode surfaces, where obtaining the crucial information on metal deposits in terms of crystal orientation, plated volume, and growth rate is very challenging. In situ liquid phase transmission electron microscopy (LPTEM) is a promising technique to visualize and understand electrodeposition processes, however a detailed quantification of which presents significant difficulties. Here by performing Zn electroplating and analyzing the data via basic image processing, this work not only sheds new light on the dendrite growth mechanism but also demonstrates a workflow showcasing how dendritic deposition can be visualized with volumetric and growth rate information. These results along with additionally corroborated 4D STEM analysis take steps to access information on the crystallographic orientation of the grown Zn nucleates and toward live quantification of in situ electrodeposition processes.

Quantitative electric field mapping between electrically biased needles by scanning transmission electron microscopy and electron holography

Stray electric fields in free space generated by two biased gold needles have been quantified in comprehensive finite-element (FE) simulations, accompanied by first moment (FM) scanning TEM (STEM) and electron holography (EH) experiments. The projected electrostatic potential and electric field have been derived numerically under geometrical variations of the needle setup. In contrast to the FE simulation, application of an analytical model based on line charges yields a qualitative understanding. By experimentally probing the electric field employing FM STEM and EH under alike conditions, a discrepancy of about 60% became apparent initially. However, the EH setup suggests the reconstructed phase to be significantly affected by the perturbed reference wave effect, opposite to STEM where the field-free reference was recorded subsequently with unbiased needles in which possibly remaining electrostatic influences are regarded as being minor. In that respect, the observed discrepancy between FM imaging and EH is resolved after including the long-range potential landscape from FE simulations into the phase of the reference wave in EH.

Screening of Coatings for an All-Solid-State Battery using In Situ Transmission Electron Microscopy

With the ever-increasing use of Li-ion batteries, especially due to their adoption in electric vehicles, their safety is in prime focus. Thus, the all-solid-state batteries (ASSBs) that use solid electrolytes instead of liquid electrolytes, which reduce the risk of flammability, have been the center stage of battery research for the last few years. However, in the ASSB, the ion transportation through the solid-solid electrolyte-electrode interface poses a challenge due to contact and chemical/electrochemical stability issues. Applying a suitable coating around the electrode and/or electrolyte particles offers a convenient solution, leading to better performance. For this, researchers are screening potential electronic/ionic conductive and nonconductive coatings to find the best coatings with suitable thickness for long-term chemical, electrochemical, and mechanical stability. Operando transmission electron microscopy (TEM) couples high spatial resolution with high temporal resolution to allow visualization of dynamic processes, and thus is an ideal tool to evaluate electrode/electrolyte coatings via studying (de)lithiation at a single particle level in real-time. However, the accumulated electron dose during a typical high-resolution in situ work may affect the electrochemical pathways, evaluation of which can be time-consuming. The current protocol presents an alternative procedure in which the potential coatings are applied on Si nanoparticles and are subjected to (de)lithiation during operando TEM experiments. The high volume changes of Si nanoparticles during (de)lithiation allow monitoring of the coating behavior at a relatively low magnification. Thus, the whole process is very electron-dose efficient and offers quick screening of potential coatings.

Pioglitazone-incorporated microspheres alleviates cardiac dysfunction through macrophage polarization in a rat myocardial infarction model

 

Inflammatory processes are essential for the repair processes after myocardial infarction. Among inflammatory cells involved in this process, macrophages play a critical role through polarization in pro-inflammatory M1 or reparative M2 subtype. Pioglitazone, known as a treatment drug for diabetes mellitus, is reported to regulate macrophage polarization toward reparative M2 subtype. Poly L-lactic-co-glycolic acid (PLGA) has been widely accepted as the delivery carrier in drug delivery system (DDS).

Here, we aimed to validate the therapeutic effects and investigate the mechanisms of DDS-based treatment using pioglitazone to left ventricular remodeling after myocardial infarction.

Pioglitazone-incorporated PLGA microspheres (PGZ-MS) were prepared and the drug release profile was evaluated. The concentration of interleukin-10 secreted from murine bone marrow derived macrophages incubated with PGZ-MS was quantified in the culture supernatant. To validate the therapeutic potential of PGZ-MS in vivo, Sprague-Dawley rats were subjected to permanent left coronary artery ligation to induce myocardial infarction. Mock-MS (100 μg) or PGZ-MS (100 μg) was injected to the infarct region just after induction (n=9–11/group). Cardiac function and left ventricular size were assessed by echocardiography. At 28-day after surgery, rats were sacrificed, and excised hearts were evaluated histologically.

PGZ-MS released 1.8±0.3% of incorporated PGZ within 24 hours and 29.5±1.2% within 14 days indicating sustained release of PGZ in vitro. PGZ-MS augmented Interleukin-10 release from bone marrow derived macrophages, indicating polarization toward reparative M2 subtype. PGZ-MS significantly ameliorated cardiac function after myocardial infarction (fractional shortening: MI vs MI+Mock-MS vs MI+PGZ-MS, 24.4±1.1 vs 24.3±1.6 vs 32.2±1.4%; P=0.0035) with reverse remodeling (wall thickness: MI vs MI+Mock-MS vs MI+PGZ-MS, 0.69±0.12 vs 0.71±0.13 vs 1.06±0.09; P=0.03). Immunohistochemical analyses revealed that PGZ-MS enhanced macrophage polarization toward reparative M2 subtype (ratio of reparative M2 macrophages: 0.39±0.03 vs 0.42±0.02 vs 0.54±0.02; P=0.0004) and attenuated apoptosis of cardiomyocytes in the ischemic border zone (MI vs MI+Mock-MS vs MI+PGZ-MS, 2.6±0.2 vs 1.9±0.2 vs 1.2±0.2 cells/field; P=0.002).

In the present study, we confirmed that PGZ-MS could realize sustained release of pioglitazone which resulted in sustained effect of macrophage polarization and attenuated left ventricular remodeling accompanied with the amelioration of cardiac dysfunction and cardiomyocytes apoptosis. The strategy of DDS-based macrophage polarization might serve as a promising strategy in cardiac regenerative therapy for ischemic heart disease in the future.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Grants-in-Aid for Scientific Research from the Ministry of Education, Science, Sports and Culture of Japan

Atomic Reconstruction and Oxygen Evolution Reaction of Mn3O4 Nanoparticles

Understanding the chemical states of individual surface atoms and their arrangements is essential for addressing several current issues such as catalysis, energy stroage/conversion, and environmental protection. Here, we exploit a profile imaging technique to understand the correlation between surface atomic structures and the oxygen evolution reaction (OER) in Mn₃O₄ nanoparticles. We image surface structures of Mn₃O₄ nanoparticles and observe surface reconstructions in the (110) and (101) planes. Mn³⁺ ions at the surface, which are commonly considered as the active sites in OER, disappear from the reconstructed planes, whereas Mn³⁺ ions are still exposed at the edges of nanoparticles. Our observations suggest that surface reconstructions can deactivate low-index surfaces of Mn oxides in OER. These structural and chemical observations are further validated by density functional theory calculations. This work shows why atomic-scale characterization of surface structures is crucial for a molecular-level understanding of a chemical reaction in oxide nanoparticles.

Effects of the Heterointerface on the Growth Characteristics of a Brownmillerite SrFeO2.5 Thin Film Grown on SrRuO3 and SrTiO3 Perovskites

Manipulation of the heterointerfacial structure and/or chemistry of transition metal oxides is of great interest for the development of novel properties. However, few studies have focused on heterointerfacial effects on the growth characteristics of oxide thin films, although such interfacial engineering is crucial to determine the growth dynamics and physical properties of oxide heterostructures. Herein, we show that heterointerfacial effects play key roles in determining the growth process of oxide thin films by overcoming the simple epitaxial strain energy. Brownmillerite (SrFeO_2.5; BM-SFO) thin films are epitaxially grown along the b-axis on both SrTiO₃(001) and SrRuO₃/SrTiO₃(001) substrates, whereas growth along the a-axis is expected from conventional epitaxial strain effects originating from lattice mismatch with the substrates. Scanning transmission electron microscopy measurements and first principles calculations reveal that these peculiar growth characteristics of BM-SFO thin films originate from the heterointerfacial effects governed by their distinct interfacial structures. These include octahedral connectivity between dissimilar oxides containing different chemical species and a peculiar transition layer for BM-SFO/SrRuO₃/SrTiO₃(001) and BM-SFO/SrTiO₃(001) heterostructures, respectively. These effects enable subtle control of the growth process of oxide thin films and could facilitate the fabrication of novel functional devices.

Unraveling the Origin and Mechanism of Nanofilament Formation in Polycrystalline SrTiO3 Resistive Switching Memories

Three central themes in the study of the phenomenon of resistive switching are the nature of the conducting phase, why it forms, and how it forms. In this study, the answers to all three questions are provided by performing switching experiments in situ in a transmission electron microscope on thin films of the model system polycrystalline SrTiO₃ . On the basis of high-resolution transmission electron microscopy, electron-energy-loss spectroscopy and in situ current-voltage measurements, the conducting phase is identified to be SrTi₁₁ O₂₀ . This phase is only observed at specific grain boundaries, and a Ruddlesden-Popper phase, Sr₃ Ti₂ O₇ , is typically observed adjacent to the conducting phase. These results allow not only the proposal that filament formation in this system has a thermodynamic origin-it is driven by electrochemical polarization and the local oxygen activity in the film decreasing below a critical value-but also the deduction of a phase diagram for strongly reduced SrTiO₃ . Furthermore, why many conducting filaments are nucleated at one electrode but only one filament wins the race to the opposite electrode is also explained. The work thus provides detailed insights into the origin and mechanisms of filament generation and rupture.

Design optimization of a fast-neutron detector with scintillating fibers for triton burnup experiments at fusion experimental devices

Time-resolved triton burnup studies have been carried out to estimate the behavior of alpha particles in DD fusion experimental devices. In those studies, 14 MeV neutrons emitted through DT reactions in DD plasmas should be measured selectively in the backgrounds of DD neutrons and gamma rays. For this purpose, a scintillating-fiber (Sci-Fi) based fast-neutron detector has been adapted because of its advantages such as fast response, design flexibility in detection efficiency by changing the number of Sci-Fi, and discrimination property against 2.4 MeV neutrons produced through DD reactions and gamma rays. However, its length had conventionally been set to around 10 cm without an optimization study of its design parameters to meet the requirements as 14 MeV neutron detector. In the present study, we tested three types of Sci-Fi detectors with three different lengths and compared with the simulated results of energy deposition, through which we tried to understand the phenomena in the detection process of fast neutrons. From the results, it has been shown that, due to the self-shielding of neutrons by Sci-Fi and the attenuation of scintillation photons during the transmission process to the photomultiplier tube, the optimal length of Sci-Fi is concluded to be about 6 cm.

Determination of X-ray Elastic Constants in a Ti-14Al-21Nb Nb Alloy and a Ti-14Al-21Nb/SiC Metal Matrix Composite

Residual stress values in a material are governed by the measurements of the atomic spacings in a specific crystallographic plane and the elastic constant for that plane. It has been reported that the value of the elastic constant depends on microstructure, preferred orientation, plastic deformation and morphology [1], Thus, the theoretical calculation of the elastic constant may deviate from the intrinsic value for a real alloy.

Confining vertical conducting filament for reliable resistive switching by using a Au-probe tip as the top electrode for epitaxial brownmillerite oxide memristive device

We had discovered novel resistance switching phenomena in SrCoOx epitaxial thin films. We have interpreted the results in terms of the topotactic phase transformation between their insulating brownmillerite phase and the conducting perovskite phase and the existence of a rather vertical conducting filament due to its inherent layered structure. However, the rough interface observed between the SrCoOx and the Au top electrode (area ~10000 μm2) was assumed to result in the observed fluctuation in key switching parameters. In order to verify the effect of rough interface on the switching performance in the SrCoOx device, in this work, we studied the resistive switching properties of a SrCoOx device by placing a Au-coated tip (end area ~0.5 μm2) directly on the film surface as the top electrode. The resulting device displayed much improved endurance and showed high uniformity in key switching parameters as compared to the device having a large top electrode area. A simulation result confirmed that the Au-coated tip provides a local confinement of the electrical field, resulting in confinement of oxygen ion distribution and therefore localization of the conducting filament. By minimizing other free and uncontrollable parameters, the designed experiment here provides the most direct and isolated evidence that the rough interface between electrode and ReRAM matrix is detrimental for the reproducibility of resistivity switching phenomena.

Tris(2-benzimidazolylmethyl)amine-Directed Synthesis of Single-Atom Nickel Catalysts for Electrochemical CO Production from CO2

The electrochemical reduction of carbon dioxide (CO₂ ) to value-added products is a promising approach to reducing excess CO₂ in the atmosphere. However, the development of electrocatalysts for highly selective and efficient electrochemical CO₂ reduction has been challenging because protons are usually easier to reduce than CO₂ in an aqueous electrolyte. Recently, single-atom catalysts (SACs) have been suggested as candidate CO₂ reduction catalysts due to their unique catalytic properties. To prepare single-atom metal active sites, the stabilization of metal atoms over conductive supports such as graphene sheets to prevent metal aggregation is crucial. To address this issue, a facile method was developed to prepare single-atom nickel active sites on reduced graphene oxide (RGO) sheets for the selective production of carbon monoxide (CO) from CO₂ . The tris(2-benzimidazolylmethyl)amine (NTB) ligand was introduced as a linker that can homogeneously disperse nickel atoms on the graphene oxide (GO) sheets. Because the NTB ligands form strong interactions with the GO sheets by π-π interactions and with nickel ions by ligation, they can effectively stabilize nickel ions on GO sheets by forming Ni(NTB)-GO complexes. High-temperature annealing of Ni(NTB)-GO under inert atmosphere produces nickel- and nitrogen-doped reduced graphene oxide sheets (Ni-N-RGO) with single-atom Ni-N₄ active sites. Ni-N-RGO shows high CO₂ reduction selectivity in the reduction of CO₂ to CO with 97 % faradaic efficiency at -0.8 V vs. RHE (reversible hydrogen electrode).

Tumor Markers in Patients with Chronic Renal Failure

In order to evaluate the specificity of tumor markers in chronic renal failure, we have determined serum levels of carcinoembryonic antigen (CEA), carbohydrate antigen 19.9 (CA 19.9), carbohydrate antigen 50 (CA 50), alfafetoprotein (AFP), neuron-specific enolase (NSE), prostatic acid phosphatase (PAP), prostatic specific antigen (PSA), squamous cell carcinoma antigen (SCC), carbohydrate antigen 15.3 (CA 15.3) and carbohydrate antigen 125 (CA 125) in 30 patients with cronic renal failure and in 36 hemodialyzed patients without clinical evidence of neoplasia. CEA, CA 50, NSE and SCC frequently show increased serum levels, suggesting a renal metabolism, while others remain, generally, within the normal levels.

Cyfra 21–1 in Lung Cancer: Comparison with Cea, Ca 125, Scc and Nse Serum Levels

CYFRA 21–1, CEA, CA 125, SCC and NSE serum levels were determined in 50 healthy subjects and in 189 patients with primary lung cancer (101 with locoregional disease, 68 with recurrence and 20 patients with no evidence of residual disease (NED). Abnormal CYFRA 21–1 serum levels were found in 53.6% (90/168) of the patients with active cancer. Neither healthy subjects nor NED patients had abnormal serum levels. CYFRa 21–1 serum concentrations were significantly higher in patients with active cancer than in healthy subjects or in NED patients (p < 0.0001). CYFRA 21–1 sensitivity was related to tumor histology with abnormal levels in 64.7% of patients with NSCLC and in 30% of patients with SCLC (P <0.0001). In NSCLC, serum CYFRA 21–1 concentrations were also related to histological type, the highest values being found in squamous cell carcinomas and LCLC and the lowest in adenocarcinomas (p < 0.04). There was also a clear relationship between CYFRA 21–1 and tumor extension, with significantly higher values in patients with metastases than in those without metastases (p < 0.0001). Abnormal CEA values were found in 49.1%, CA 125 in 39%, SCC in 27.8% and NSE in 21.3% of the patients with active cancer. With respect to histological type, CYFRA was elevated in 68.3% of squamous cell carcinomas (CEA: 46.7%, SCC: 50%, CA 125:31.7%, NSE: 11.7%), in 54.8% of adenocarcinomas (CEA: 62%, SCC: 26.2%, CA 125: 59.5%, NSE: 9.5%), in 78.6% of LCLC (CEA: 64.3%, SCC: 28.6%, CA 125: 78.6%, NSE: 7.1%) and in 30% of SCLC (CEA: 37.7%, SCC: 3.8%, CA 125:20.8%, NSE: 45.3%). In summary, CYFRA 21–1 is the most sensitive tumor marker in patients with lung cancer, especially in NSCLC patients.

Mucin-Like Carcinoma-Associated Antigen (MCA) in Tissue and Serum of Patients with Breast Cancer: Clinical Applications in Prognosis and Disease Monitoring

Mucin-like Carcinoma-associated Antigen (MCA) has been associated with many breast cancers. The aim of this study was to evaluate MCA in tumor tissue and serum as a potential tumor marker for prognosis and disease monitoring. MCA levels were determined in the tissue of 196 patients with primary breast cancer, 25 with metastatic disease and 25 patients with benign diseases, in pellet and/or cytosol. MCA levels were also determined in the serum of 50 patients with benign diseases, 148 with primary breast cancer (Mo), 150 with metastatic breast cancer (MT), and 200 with no clinical evidence of disease (NED). MCA tissue concentrations in pellet and cytosol were similar: 66.7 + 251 U/mg and 41.1 + 53 U/mg, respectively. No relationship between MCA levels and tumor size or nodal involvement was found. Higher MCA levels were observed in patients with ER + or PgR + tumors than in those with ER- or PgR- tumors (p < 0.01). Patients with MCA pellet concentrations lower than 10 U/mg of protein had shorter disease - free intervals (DFI) than those with higher values (p < 0.05).

Abnormally high serum levels of MCA were found in 8% of patients with benign diseases, 4% of NED patients, 22% of Mo patients, and in 76% of MT cases. In primary breast cancer MCA values were related to tumor size and nodal involvement. A trend toward a lower DFI in patients with elevated presurgical MCA levels was observed but was of no statistical significance. These differences became statistically significant when patients were subdivided according to nodal status, with shorter DFI in those without nodal invasion (p < 0.05). In metastatic patients, changes in serum MCA were related to the tumor's response to treatment in 82% of cases. The highest MCA values were found in patients with liver or bone metastasis and the lowest values were found in those with locoregional recurrence. In conclusion, although MCA is not a specific tumor marker, it can be useful as a prognostic factor (tissue and serum) and in monitoring metastatic patients.

CA 125 in Biological Fluids

CA 125 is not a specific tumor marker, and is synthesized by normal and malignant cells of different origin (mainly in tissues derived from the müllerian epithelia) in a similar proportion. Abnormal CA 125 levels may be found in fluids of different origin (ascites, pleura, pericardium, amniotic fluid, cyst fluid, bronchoalveolar fluid, etc.) and in serum from patients with these fluids. Differences in serum CA 125 found in malignant or benign diseases may be related to the number of cells that synthesize the marker, and are highly dependent on the access to serum, where the marker is normally determined. Moreover, CA 125 is a very good tumor marker in ovarian and lung cancer. The sensitivity of CA 125 in ovarian cancer is related to stage (40–95%), histological type (lower levels in mucinous adenocarcinoma), and the marker is useful in the early detection of recurrence (sensitivity 80%) and in therapy monitoring. It's sensitivity in lung cancer is lower than in ovarian cancer, 39% in locoregional malignancies and 69% in metastastatic disease, but clearly related to stage and histology (mainly in adenocarcinomas and large cell lung cancer) and it is useful in prognosis and disease monitoring.

Real-Time Characterization Using in situ RHEED Transmission Mode and TEM for Investigation of the Growth Behaviour of Nanomaterials

A novel characterization technique using both in situ reflection high-energy electron diffraction (RHEED) transmission mode and transmission electron microscopy (TEM) has been developed to investigate the growth behaviour of semiconductor nanostructures. RHEED employed in transmission mode enables the acquisition of structural information during the growth of nanostructures such as nanorods. Such real-time observation allows the investigation of growth mechanisms of various nanomaterials that is not possible with conventional ex situ analytical methods. Additionally, real-time monitoring by RHEED transmission mode offers a complete range of information when coupled with TEM, providing structural and chemical information with excellent spatial resolution, leading to a better understanding of the growth behaviour of nanomaterials. Here, as a representative study using the combined technique, the nucleation and crystallization of InAs nanorods and the epitaxial growth of In_xGa_1−xAs(GaAs) shell layers on InAs nanorods are explored. The structural changes in the InAs nanorods at the early growth stage caused by the transition of the local growth conditions and the strain relaxation processes that occur during epitaxial coating of the shell layers are shown. This technique advances our understanding of the growth behaviour of various nanomaterials, which allows the realization of nanostructures with novel properties and their application in future electronics and optoelectronics.

A pilot study of planar coil based magnetic stimulation using acute hippocampal slice in mice

Micromagnetic stimulation using small-sized implantable coils has recently been studied. The main advantage of this method is that it can provide sustainable stimulation performance even if a fibrotic encapsulation layer is formed around the implanted coil by inflammation response, because indirectly induced currents are used to induce neural responses. In previous research, we optimized the geometrical and control parameters used in implantable magnetic stimulation. Based on those results, we fabricated the planar coil and studied the LTP effect in the hippocampal slice by two different magnetic stimulation protocols using the quadripulse stimulation (QPS) pattern. We found that direct magnetic stimulation (DMS) induced insignificant LTP effect and priming magnetic stimulation (PMS) occluded LTP effect after tetanic stimulation, when QPS patterned magnetic stimulation with 1 A current pulse was applied to the planar coil.

Brownmillerite thin films as fast ion conductors for ultimate-performance resistance switching memory

An oxide-based resistance memory is a leading candidate to replace Si-based flash memory as it meets the emerging specifications for future memory devices. The non-uniformity in the key switching parameters and low endurance in conventional resistance memory devices are preventing its practical application. Here, a novel strategy to overcome the aforementioned challenges has been unveiled by tuning the growth direction of epitaxial brownmillerite SrFeO_2.5 thin films along the SrTiO₃ [111] direction so that the oxygen vacancy channels can connect both the top and bottom electrodes rather directly. The controlled oxygen vacancy channels help reduce the randomness of the conducting filament (CF). The resulting device displayed high endurance over 10⁶ cycles, and a short switching time of ∼10 ns. In addition, the device showed very high uniformity in the key switching parameters for device-to-device and within a device. This work demonstrates a feasible example for improving the nanoscale device performance by controlling the atomic structure of a functional oxide layer.

Microtube Light-Emitting Diode Arrays with Metal Cores

We report the fabrication and characteristics of vertical microtube light-emitting diode (LED) arrays with a metal core inside the devices. To make the LEDs, gallium nitride (GaN)/indium gallium nitride (In(x)Ga(1-x)N)/zinc oxide (ZnO) coaxial microtube LED arrays were grown on an n-GaN/c-aluminum oxide (Al2O3) substrate. The microtube LED arrays were then lifted-off the substrate by wet chemical etching of the sacrificial ZnO microtubes and the silicon dioxide (SiO2) layer. The chemically lifted-off LED layer was then transferred upside-down on other supporting substrates. To create the metal cores, titanium/gold and indium tin oxide were deposited on the inner shells of the microtubes, forming n-type electrodes inside the metal-cored LEDs. The characteristics of the resulting devices were determined by measuring electroluminescence and current-voltage characteristic curves. To gain insights into the current-spreading characteristics of the devices and understand how to make them more efficient, we modeled them computationally.

Epitaxial Brownmillerite Oxide Thin Films for Reliable Switching Memory

Resistive switching memory, which is mostly based on polycrystalline thin films, suffers from wide distributions in switching parameters-including set voltage, reset voltage, and resistance-in their low- and high-resistance states. One of the most commonly used methods to overcome this limitation is to introduce inhomogeneity. By contrast, in this paper, we obtained uniform resistive switching parameters and sufficiently low forming voltage by maximizing the uniformity of an epitaxial thin film. To achieve this result, we deposited an SrFeOx/SrRuO3 heteroepitaxial structure onto an SrTiO3 (001) substrate by pulsed laser deposition, and then we deposited an Au top electrode by electron-beam evaporation. This device exhibited excellent bipolar resistance switching characteristics, including a high on/off ratio, narrow distribution of key switching parameters, and long data retention time. We interpret these phenomena in terms of a local, reversible phase transformation in the SrFeOx film between brownmillerite and perovskite structures. Using the brownmillerite structure and atomically uniform thickness of the heteroepitaxial SrFeOx thin film, we overcame two major hurdles in the development of resistive random-access memory devices: high forming voltage and broad distributions of switching parameters.

EBV-positive diffuse large B-cell lymphoma in young adults: is this a distinct disease entity?

BACKGROUND

Epstein-Barr virus (EBV)-positive diffuse large B-cell lymphoma (DLBCL) of the elderly is defined only in adults older than 50 years. However, EBV-positive DLBCL can affect younger patients. We investigated the prevalence, clinical characteristics and survival outcomes of EBV-positive DLBCL in young adults.

PATIENTS AND METHODS

We analyzed patients with de novo DLBCL who were registered in the Samsung Medical Center (SMC) retrospective lymphoma cohort and prospective SMC Lymphoma Cohort Study I (ClinicalTrials.gov: NCT00822731).

RESULTS

A total of 571 cases were included in the analysis. The prevalence of EBV positivity was 6.7% (13/195) and 9.3% (35/376) in the young group (≤50 years) and in the elderly group (>50 years), respectively. EBV status was closely associated with unique unfavorable clinical characteristics [older age, more advanced stage, two or more sites of extranodal involvement, higher International Prognostic Index (IPI), and age-adjusted IPI risk] only in the elderly group. Poor prognostic impact of EBV positivity on overall survival was observed only in the elderly group [hazard ratio (HR) 2.86; 95% confidence interval (CI) 1.83-4.47; P < 0.001], but not in the young group (HR 1.17; 95% CI 0.35-3.89; P = 0.801).

CONCLUSION

A substantial proportion of EBV-positive DLBCL of the elderly can occur in young adults. EBV positivity of DLBCL in young adults was not associated with unfavorable clinical characteristics or worse outcomes. We suggest that EBV-positive DLBCL should not be confined only in the elderly and 'EBV-positive DLBCL in young adults' needs to be considered as a clinically distinct disease entity. ClinicalTrials.gov: NCT02060435.

Variable-color light-emitting diodes using GaN microdonut arrays

Microdonut-shaped GaN/Inx Ga1-x N light-emitting diode (LED) microarrays are fabricated for variable-color emitters. The figure shows clearly donut-shaped light emission from all the individual microdonut LEDs. Furthermore, microdonut LEDs exhibit spatially-resolved blue and green EL colors, which can be tuned by either controlling the external bias voltage or changing the size of the microdonut LED.

High-resolution observation of nucleation and growth behavior of nanomaterials using a graphene template

By using graphene as an electron beam-transparent substrate for both nanomaterial growth and transmission electron microscopy (TEM) measurements, we investigate initial growth behavior of nanomaterials. The direct growth and imaging method using graphene facilitate atomic-resolution imaging of nanomaterials at the very early stage of growth. This enables the observation of the transition in crystal structure of ZnO nuclei and the formation of various defects during nanomaterial growth.