Size Dependence of Metal-Insulator Transition in Stoichiometric Fe3O4 Nanocrystals

Magnetite (Fe3O4) is one of the most actively studied materials with a famous metal-insulator transition (MIT), so-called the Verwey transition at around 123 K. Despite the recent progress in synthesis and characterization of Fe3O4 nanocrystals (NCs), it is still an open question how the Verwey transition changes on a nanometer scale. We herein report the systematic studies on size dependence of the Verwey transition of stoichiometric Fe3O4 NCs. We have successfully synthesized stoichiometric and uniform-sized Fe3O4 NCs with sizes ranging from 5 to 100 nm. These stoichiometric Fe3O4 NCs show the Verwey transition when they are characterized by conductance, magnetization, cryo-XRD, and heat capacity measurements. The Verwey transition is weakly size-dependent and becomes suppressed in NCs smaller than 20 nm before disappearing completely for less than 6 nm, which is a clear, yet highly interesting indication of a size effect of this well-known phenomena. Our current work will shed new light on this ages-old problem of Verwey transition.Comment: 18 pages, 4 figures, Nano Letters (accepted

Size Dependence of Metal-Insulator Transition in Stoichiometric Fe3O4 Nanocrystals

Magnetite (Fe3O4) is one of the most actively studied materials with a famous metal-insulator transition (MIT), so-called the Verwey transition at around 123 K. Despite the recent progress in synthesis and characterization of Fe3O4 nanocrystals (NCs), it is still an open question how the Verwey transition changes on a nanometer scale. We herein report the systematic studies on size dependence of the Verwey transition of stoichiometric Fe3O4 NCs. We have successfully synthesized stoichiometric and uniform-sized Fe3O4 NCs with sizes ranging from 5 to 100 nm. These stoichiometric Fe3O4 NCs show the Verwey transition when they are characterized by conductance, magnetization, cryo-XRD, and heat capacity measurements. The Verwey transition is weakly size-dependent and becomes suppressed in NCs smaller than 20 nm before disappearing completely for less than 6 nm, which is a clear, yet highly interesting indication of a size effect of this well-known phenomena. Our current work will shed new light on this ages-old problem of Verwey transition.Comment: 18 pages, 4 figures, Nano Letters (accepted

Expression and characterization of Pantoea CO dehydrogenase to utilize CO-containing industrial waste gas for expanding the versatility of CO dehydrogenase

Although aerobic CO dehydrogenases (CODHs) might be applicable in various fields, their practical applications have been hampered by low activity and no heterologous expression. We, for the first time, could functionally express recombinant PsCODH in E. coli and obtained a highly concentrated recombinant enzyme using an easy and convenient method. Its electron acceptor spectra, optimum conditions (pH 6.5 and 30 degrees C), and kinetic parameters (k(cat) of 12.97 s(-1), Km of 0.065 mM, and specific activity of 0.86 Umg(-1)) were examined. Blast furnace gas (BFG) containing 20% CO, which is a waste gas from the steel-making process, was tested as a substrate for PsCODH. Even with BFG, the recombinant PsCODH retained 88.2% and 108.4% activity compared with those of pure CO and 20% CO, respectively. The results provide not only a promising strategy to utilize CO-containing industrial waste gases as cheap, abundant, and renewable resources but also significant information for further studies about cascade reactions producing value-added chemicals via CO2 as an intermediate produced by a CODHbased CO-utilization system, which would ultimately expand the versatility of CODH.ope

Reconfigurable Intelligent Surface-Aided Wireless Power Transfer Systems: Analysis and Implementation

Reconfigurable intelligent surface (RIS) is a promising technology for RF wireless power transfer (WPT) as it is capable of beamforming and beam focusing without using active and power-hungry components. In this paper, we propose a multi-tile RIS beam scanning (MTBS) algorithm for powering up internet-of-things (IoT) devices. Considering the hardware limitations of the IoT devices, the proposed algorithm requires only power information to enable the beam focusing capability of the RIS. Specifically, we first divide the RIS into smaller RIS tiles. Then, all RIS tiles and the phased array transmitter are iteratively scanned and optimized to maximize the receive power. We elaborately analyze the proposed algorithm and build a simulator to verify it. Furthermore, we have built a real-life testbed of RIS-aided WPT systems to validate the algorithm. The experimental results show that the proposed MTBS algorithm can properly control the transmission phase of the transmitter and the reflection phase of the RIS to focus the power at the receiver. Consequently, after executing the algorithm, about 20 dB improvement of the receive power is achieved compared to the case that all unit cells of the RIS are in OFF state. By experiments, we confirm that the RIS with the MTBS algorithm can greatly enhance the power transfer efficiency

Fusarium Wilt of Strawberry: Etiological and Ecological Characteristics, and Management

Fusarium wilt, caused by Fusarium oxysporum f. sp. fragariae, is a major disease affecting strawberry plants worldwide. Since it was first reported in Korea in 1982, strawberry Fusarium wilt has occurred in most cultivated strawberry cultivars. Although many efforts have been made to control the disease, a comprehensive review of Fusarium wilt control is necessary because of its continuing occurrence. In this review, we introduce a variety of strawberry Fusarium wilt management methods, including the pathogen taxonomy involved in this disease, the importance of latent infection, diagnostic techniques, environmental factors, and control methods. We hope that this review will help strawberry farmers and researchers adopt a comprehensive and effective approach for Fusarium wilt control by understanding this disease and studying the latest control methods

Notch1 binds and induces degradation of Snail in hepatocellular carcinoma

<p>Abstract</p> <p>Background</p> <p>Hepatocellular carcinoma (HCC) is a common, highly invasive malignant tumor associated with a high mortality rate. We previously reported that the aberrant expression of Snail via activation of reactive oxygen species contributes to the invasive property of HCC, in part by downregulation of E-cadherin through both transcriptional repression and epigenetic modification of the E-cadherin promoter. Having demonstrated the ability of Snail to bind and recruit histone deacetylase 1 and DNA methyltransferase 1 in this context, we set out to look for other interactions that could affect its ability to promote oncogenic transformation and cancer cell invasion.</p> <p>Results</p> <p>Using cells that stably expressed Snail, we characterized Snail protein interactors by tandem affinity purification and mass spectrometry. Immunoprecipitation and subcellular colocalization studies were performed to confirm our identification of the Notch1 intracellular domain (NICD) as a novel Snail-binding partner. NICD interaction with Snail was found to induce ubiquitination and MDM2-dependent degradation of Snail. Interestingly, NICD inhibited Snail-dependent invasive properties in both HCC cells and mouse embryonic fibroblasts.</p> <p>Conclusions</p> <p>Our study demonstrates that NICD can oppose Snail-dependent HCC cell invasion by binding and inducing proteolytic degradation of Snail. Although Notch signaling and Snail are both widely considered tumor-promoting factors, our findings indicate that the individual oncogenic contribution of Notch1 and Snail in malignant systems should be interpreted carefully, particularly when they are conjointly expressed.</p

Slow oxidation of magnetite nanoparticles elucidates the limits of the Verwey transition

Magnetite (Fe3O4) is of fundamental importance as the original magnetic material and also for the Verwey transition near T_V = 125 K, below which a complex lattice distortion and electron orders occur. The Verwey transition is suppressed by strain or chemical doping effects giving rise to well-documented first and second-order regimes, but the origin of the order change is unclear. Here, we show that slow oxidation of monodisperse Fe3O4 nanoparticles leads to an intriguing variation of the Verwey transition that elucidates the doping effects. Exposure to various fixed oxygen pressures at ambient temperature leads to an initial drop to TV minima as low as 70 K after 45-75 days, followed by recovery to a constant value of 95 K after 160 days that persists in all experiments for aging times up to 1070 days. A physical model based on both doping and doping-gradient effects accounts quantitatively for this evolution and demonstrates that the persistent 95 K value corresponds to the lower limit for homogenously doped magnetite and hence for the first order regime. In comparison, further suppression down to 70 K results from inhomogeneous strains that characterize the second-order region. This work demonstrates that slow reactions of nanoparticles can give exquisite control and separation of homogenous and inhomogeneous doping or strain effects on an nm scale and offers opportunities for similar insights into complex electronic and magnetic phase transitions in other materials.Comment: 24 pages, 13 figures, 2 tables, the manuscript is accepted for publishing at Nature Communication

Does robot-assisted laparoscopic radical prostatectomy enable to obtain adequate oncological and functional outcomes during the learning curve? From the Korean experience

To estimate the short-term results of robot-assisted laparoscopic radical prostatectomy (RALRP) during the learning curve, in terms of surgical, oncological and functional outcomes, we conducted a prospective survey on RALRP. From July 2007, a single surgeon performed 63 robotic prostatectomies using the same operative technique. Perioperative data, including pathological and early functional results of the patient, were collected prospectively and analyzed. Along with the accumulation of the cases, the total operative time, setup time, console time and blood loss were significantly decreased. No major complication was present in any patient. Transfusion was needed in six patients; all of them were within the initial 15 cases. The positive surgical margin rate was 9.8% (5/51) in pT2 disease. The most frequent location of positive margin in this stage was the lateral aspect (60%), but in pT3 disease multiple margins were the most frequent (41.7%). Overall, 53 (84.1%) patients had totally continent status and the median time to continence was 6.56 weeks. Among 17 patients who maintained preoperative sexual activity ( Sexual Health Inventory for Men \u3e = 17), stage below pT2, followed up for \u3e 6 months with minimally one side of neurovascular bundle preservation procedure, 12 (70.6%) were capable of intercourse postoperatively, and the mean time for sexual intercourse after operation was 5.7 months. In this series, robotic prostatectomy was a feasible and reproducible technique, with a short learning curve and low perioperative complication rate. Even during the initial phase of the learning curve, satisfactory results were obtained with regard to functional and oncological outcome