Showing papers by "University of Electro-Communications published in 2013"
TL;DR: It is demonstrated that the nature of the metallic precursor selected for SILAR has an active role in both the QD's deposition rate and the defect's distribution in the material, with important consequences for the final photovoltaic performance of the device.
Abstract: Here we report the preparation of high performance Quantum Dot Sensitized Solar Cells (QDSCs) based on PbS–CdS co-sensitized nanoporous TiO2 electrodes. QDs were directly grown on the TiO2 mesostructure by the Successive Ionic Layer Absorption and Reaction (SILAR) technique. This method is characterized by a fast deposition rate which involves random crystal growth and poor control of the defect states and lattice mismatch in the QDs limiting the quality of the electrodes for photovoltaic applications. In this work we demonstrate that the nature of the metallic precursor selected for SILAR has an active role in both the QD's deposition rate and the defect's distribution in the material, with important consequences for the final photovoltaic performance of the device. For this purpose, acetate and nitrate salts were selected as metallic precursors for the SILAR deposition and films with similar absorption properties and consequently with similar density of photogenerated carriers were studied. Under these conditions, ultrafast carrier dynamics and surface photovoltage spectroscopy reveal that the use of acetate precursors leads to higher injection efficiency and lower internal recombination due to contribution from defect states. This was corroborated in a complete cell configuration with films sensitized with acetate precursors, achieving unprecedented photocurrents of ∼22 mA cm−2 and high power conversion efficiency exceeding 4%, under full 1 sun illumination.
143 citations
TL;DR: A comprehensive view of molecular robotics is presented based on the discussions held in the Molecular Robotics Research Group, and the fundamental concept and research direction of molecular Robotics is clarified.
Abstract: The rapid progress of molecular nanotechnology has opened the door to molecular robotics, which uses molecules as robot components. In order to promote this new paradigm, the Molecular Robotics Research Group was established in the Systems and Information Division of the Society of Instrument and Control Engineers (SICE) in 2010. The group consists of researchers from various fields including chemistry, biophysics, DNA nanotechnology, systems science and robotics, challenging this emerging new field. Last year, the group proposed a research project focusing on molecular robotics, and it was recently awarded a Grant-in-Aid for Scientific Research on Innovative Areas (FY2012-16), one of the large-scale research projects in Japan, by MEXT (Ministry of Education, Culture, Sports, Science and Technology, JAPAN). Here, we wish to clarify the fundamental concept and research direction of molecular robotics. For this purpose, we present a comprehensive view of molecular robotics based on the discussions held in the Molecular Robotics Research Group.
119 citations
TL;DR: This study investigates different service provision scenarios and proposes both time domain and frequency domain overlay cognitive radio OFDM systems for next generation cellular networks and shows the proposed schemes can achieve satisfying performance in different use cases.
Abstract: In this study, we integrate overlay cognitive radio technology into 4G cellular networks for the sharing of TV spectrum. On one hand, OFDM is a promising technique for high-speed data transmission over multipath fading channels and has been considered to be the best candidate for 4G mobile networks. On another hand, the overlay cognitive radio model makes it possible to have two concurrent transmissions in a given interference region, where conventionally only one communication takes place at a given time. We investigate different service provision scenarios and propose both time domain and frequency domain overlay cognitive radio OFDM systems for next generation cellular networks. Numerical results show our proposed schemes can achieve satisfying performance in different use cases.
118 citations
TL;DR: In this paper, the authors address a subset of unresolved problems in collisionless shock physics from experimental point of view making use of multi-point observations onboard Cluster satellites, including determination of scales of fields and of a scale of electron heating, identification of energy source of precursor wave train, an estimate of the role of anomalous resistivity in energy dissipation process by means of measuring short scale wave fields, and direct observation of reformation process during one single shock front crossing.
Abstract: The physics of collisionless shocks is a very broad topic which has been studied for more than five decades. However, there are a number of important issues which remain unresolved. The energy repartition amongst particle populations in quasiperpendicular shocks is a multi-scale process related to the spatial and temporal structure of the electromagnetic fields within the shock layer. The most important processes take place in the close vicinity of the major magnetic transition or ramp region. The distribution of electromagnetic fields in this region determines the characteristics of ion reflection and thus defines the conditions for ion heating and energy dissipation for supercritical shocks and also the region where an important part of electron heating takes place. All of these processes are crucially dependent upon the characteristic spatial scales of the ramp and foot region provided that the shock is stationary. The earliest studies of collisionless shocks identified nonlinearity, dissipation, and dispersion as the processes that arrest the steepening of the shock transition. Their relative role determines the scales of electric and magnetic fields, and so control the characteristics of processes such as of ion reflection, electron heating and particle acceleration. The purpose of this review is to address a subset of unresolved problems in collisionless shock physics from experimental point of view making use multi-point observations onboard Cluster satellites. The problems we address are determination of scales of fields and of a scale of electron heating, identification of energy source of precursor wave train, an estimate of the role of anomalous resistivity in energy dissipation process by means of measuring short scale wave fields, and direct observation of reformation process during one single shock front crossing.
109 citations
TL;DR: A series of 3d-4f binuclear complexes, [M(3-MeOsaltn)(MeOH)x(ac)Ln(hfac)2] have been synthesized and characterized, and the X-ray analyses demonstrated that all the complexes have an acetato- and diphenolato-bridged M(II)-Ln (III) binuclear structure.
Abstract: A series of 3d-4f binuclear complexes, [M(3-MeOsaltn)(MeOH)x(ac)Ln(hfac)2] (x = 0 for M = Cu(II), Zn(II); x = 1 for M = Co(II), Ni(II); Ln = Gd(III), Tb(III), Dy(III), La(III)), have been synthesized and characterized, where 3-MeOsaltn, ac, and hfac denote N,N'-bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato, acetato, and hexafluoroacetylacetonato, respectively. The X-ray analyses demonstrated that all the complexes have an acetato- and diphenolato-bridged M(II)-Ln(III) binuclear structure. The Cu(II)-Ln(III) and Zn(II)-Ln(III) complexes are crystallized in an isomorphous triclinic space group P1, where the Cu(II) or Zn(II) ion has square pyramidal coordination geometry with N2O2 donor atoms of 3-MeOsaltn at the equatorial coordination sites and one oxygen atom of the bridging acetato ion at the axial site. The Co(II)-Ln(III) and Ni(II)-Ln(III) complexes are crystallized in an isomorphous monoclinic space group P2(1)/c, where the Co(II) or Ni(II) ion at the high-spin state has an octahedral coordination environment with N2O2 donor atoms of 3-MeOsaltn at the equatorial sites, and one oxygen atom of the bridged acetato and a methanol oxygen atom at the two axial sites. Each Ln(III) ion for all the complexes is coordinated by four oxygen atoms of two phenolato and two methoxy oxygen atoms of "ligand-complex" M(3-MeOsaltn), four oxygen atoms of two hfac(-), and one oxygen atom of the bridging acetato ion; thus, the coordination number is nine. The temperature dependent magnetic susceptibilities from 1.9 to 300 K and the field-dependent magnetization up to 5 T at 1.9 K were measured. Due to the important orbital contributions of the Ln(III) (Tb(III), Dy(III)) and to a lesser extent the M(II) (Ni(II), Co(II)) components, the magnetic interaction between M(II) and Ln(III) ions were investigated by an empirical approach based on a comparison of the magnetic properties of the M(II)-Ln(III), Zn(II)-Ln(III), and M(II)-La(III) complexes. The differences of χ(M)T and M(H) values for the M(II)-Ln(III), Zn(II)-Ln(III) and those for the M(II)-La(III) complexes, that is, Δ(T) = (χ(M)T)(MLn) - (χ(M)T)(ZnLn) - (χ(M)T)(MLa) = J(MLn)(T) and Δ(H) = M(MLn)(H) - M(ZnLn)(H) - M(MLa)(H) = J(MLn)(H), give the information of 3d-4f magnetic interaction. The magnetic interactions are ferromagnetic if M(II) = (Cu(II), Ni(II), and Co(II)) and Ln = (Gd(III), Tb(III), and Dy(III)). The magnitudes of the ferromagnetic interaction, J(MLn)(T) and J(MLn)(H), are in the order Cu(II)-Gd(III) > Cu(II)-Dy(III) > Cu(II)-Tb(III), while those are in the order of M(II)-Gd(III) ≈ M(II)-Tb(III) > M(II)-Dy(III) for M(II) = Ni(II) and Co(II). Alternating current (ac) susceptibility measurements demonstrated that the Ni(II)-Tb(III) and Co(II)-Tb(III) complexes showed out-of-phase signal with frequency-dependence and the Ni(II)-Dy(III) and Co(II)-Dy(III) complexes showed small frequency-dependence. The energy barrier for the spin flipping was estimated from the Arrhenius plot to be 14.9(6) and 17.0(4) K for the Ni(II)-Tb(III) and Co(II)-Tb(III) complexes, respectively, under a dc bias field of 1000 Oe.
101 citations
TL;DR: The spectral tunability and purity of photon pairs generated from spontaneous parametric down conversion in periodically poled KTiOPO(4) crystal with group-velocity matching condition are investigated and predicted.
Abstract: We theoretically and experimentally investigate the spectral tunability and purity of photon pairs generated from spontaneous parametric down conversion in periodically poled KTiOPO4 crystal with group-velocity matching condition. The numerical simulation predicts that the spectral purity can be kept higher than 0.81 when the wavelength is tuned from 1460 nm to 1675 nm, which covers the S-, C-, L-, and U-band in telecommunication wavelengths. We also experimentally measured the joint spectral intensity at 1565 nm, 1584 nm and 1565 nm, yielding Schmidt numbers of 1.01, 1.02 and 1.04, respectively. Such a photon source is useful for quantum information and communication systems.
99 citations
TL;DR: Simple firefly luciferin analogs emitting blue, green, and red light were developed and the longest emission maximum was observed at 675 nm, which belongs to the NIR biological window, useful for deep site bioimaging of living animals.
97 citations
TL;DR: The analysis shows that, although they can be regarded as dual to each other, the facial reduction algorithm has ability to produce a finer sequence of faces of the cone including the feasible region, and a simple proof of the convergence of theacial reduction algorithm for the conic optimization is presented.
Abstract: In the conic optimization problems, it is well-known that a positive duality gap may occur, and that solving such a problem is numerically difficult or unstable. For such a case, we propose a facial reduction algorithm to find a primal–dual pair of conic optimization problems having the zero duality gap and the optimal value equal to one of the original primal or dual problems. The conic expansion approach is also known as a method to find such a primal–dual pair, and in this paper we clarify the relationship between our facial reduction algorithm and the conic expansion approach. Our analysis shows that, although they can be regarded as dual to each other, our facial reduction algorithm has ability to produce a finer sequence of faces of the cone including the feasible region. A simple proof of the convergence of our facial reduction algorithm for the conic optimization is presented. We also observe that our facial reduction algorithm has a practical impact by showing numerical experiments for graph partition problems; our facial reduction algorithm in fact enhances the numerical stability in those problems.
96 citations
TL;DR: A theory for deriving the input that effectively minimizes the average transient time required to entrain a phase model is presented, which enables a practical technique for constructing fast entrainment waveforms for general nonlinear oscillators.
Abstract: The entrainment process is fundamental to numerous scientific and engineering applications in which oscillating systems are asymptotically synchronized to an external periodic signal [1,2]. The ability to optimize entrainment has important implications for achieving rapid cardiac resynchronization [3] and quick adjustment from jet lag [4], maximizing the growth rate of plants [5], and implementing phase-locked loop circuits and injection-locked microintegrated oscillators [6]. When the weak perturbation approximation is made, a rescaling of the phase response curve (PRC) was shown to be the minimum energy signal for spiking or entraining oscillators at a given period [7–9], and a weighted sum of appropriately shifted PRCs maximizes the range of frequency detunings for which entrainment occurs [10,11]. An alternative essential objective is to minimize the time to entrainment at a given forcing signal energy, in order to establish a fixed phase relationship between the system and forcing signal as soon as possible after the forcing is applied [12]. This notion of fast entrainment can also be used to minimize the time required to reestablish entrainment after interruptions caused by disturbances [13]. In this Letter, we use phase model reduction to derive an asymptotically optimal waveform that maximizes the average rate of entrainment for general weakly forced nonlinear oscillators. The rate of entrainment is characterized by the coefficient of exponential decay in the phase difference between the system and forcing signal. We present a theory by which the entrainment time scale is minimized for a specified forcing energy, where the optimal waveform is a sum of the PRC and its derivative with weights that depend on the difference between the natural and forcing frequencies. These findings can be applied to weakly nonlinear oscillators just past the Hopf bifurcation, as well as strongly nonlinear relaxation oscillators. We confirm our results with numerical simulations using the Hodgkin-Huxley (HH) neuron model, as well as in experiments on an oscillatory chemical system arising through the electrodissolution of nickel in sulfuric acid. Phase coordinate transformation is a model reduction technique that is useful for examining nonlinear oscillating systems [14,15], and can also be used for system identification when the dynamics are complex or unknown [2]. Such models have been studied extensively, with a particular focus on neural [14,16] and electrochemical [17–19] systems. Consider a full state-space model described by a smooth ordinary differential equation system _ x ¼ fðx; uÞ,
85 citations
TL;DR: Large-scale direct numerical simulations of homogeneous-isotropic fluid turbulence, achieving sustained performance of 1.08 petaflop/s on gpu hardware using single precision, exceeds by an order of magnitude the largest vortex-method calculations to date.
84 citations
TL;DR: The femtosecond snapshots of the relaxation process were revealed by the ultrafast optics and the energy-resolved transient reflectivity spectra disclosed the energy loss rate of Dirac fermions at room temperature was about 1 meV/ps, crucial to the design of DirAC fermion devices.
Abstract: The recent focus on topological insulators is due to the scientific interest in the new state of quantum matter as well as the technology potential for a new generation of THz optoelectronics, spintronics and quantum computations. It is important to elucidate the dynamics of the Dirac fermions in the topologically protected surface state. Hence we utilized a novel ultrafast optical pump mid-infrared probe to explore the dynamics of Dirac fermions near the Dirac point. The femtosecond snapshots of the relaxation process were revealed by the ultrafast optics. Specifically, the Dirac fermion-phonon coupling strength in the Dirac cone was found to increase from 0.08 to 0.19 while Dirac fermions were away from the Dirac point into higher energy states. Further, the energy-resolved transient reflectivity spectra disclosed the energy loss rate of Dirac fermions at room temperature was about 1 meV/ps. These results are crucial to the design of Dirac fermion devices.
TL;DR: A novel approach to prioritize CRs in QFD process is proposed by developing two sets of new rating methods, called customer preference rating (CPR) method and customer satisfaction rating (CSR) method, for relative importance ratings and competitive priority ratings, respectively.
Abstract: Customer satisfaction is one of the critical success factors to many leading companies over the world. Quality function deployment (QFD) has gained extensive international support as one of the powerful techniques to increase the customer satisfaction. In the QFD, correctly rating the final importance of customer requirements (CRs) is a crucial and essential process since it largely affects the target value setting of design requirements. The final importance ratings of CRs are generally determined by combining relative importance ratings and competitive priority ratings. However, determining the final importance ratings is very difficult due to the typical uncertainty or imprecision of customer’s judgment (or perceptions). This paper proposes a novel approach to prioritize CRs in QFD process by developing two sets of new rating methods, called customer preference rating (CPR) method and customer satisfaction rating (CSR) method, for relative importance ratings and competitive priority ratings, respectively. The CPR method provides a simple and intuitive technique to capture the customers’ incomplete or uncertain perceptions on the relative importance of CRs based on their own preferences, allowing them to give a partial ordering of CRs. The CSR method constructs the customer satisfaction model based on the competitive benchmarking analysis and then evaluates the performance quality of company product using our satisfaction and uncertainty measure. Furthermore, the CSR method is integrated with the Kano’s model to capture the different impacts of CRs on customer satisfaction. Finally, the proposed approach is illustrated with a numerical example of car door design problem.
TL;DR: Exercise training (TR) not only leads to a decrease in WAT mass but also attenuates obesity-induced dysregulated expression of the inflammation-related adipokines in Wat.
Abstract: Obesity is recognized as a risk factor for lifestyle-related diseases such as type 2 diabetes and cardiovascular disease. White adipose tissue (WAT) is not only a static storage site for energy; it is also a dynamic tissue that is actively involved in metabolic reactions and produces humoral factors, such as leptin and adiponectin, which are collectively referred to as adipokines. Additionally, because there is much evidence that obesity-induced inflammatory changes in WAT, which is caused by dysregulated expression of inflammation-related adipokines involving tumor necrosis factor-α and monocyte chemoattractant protein 1, contribute to the development of insulin resistance, WAT has attracted special attention as an organ that causes diabetes and other lifestyle-related diseases. Exercise training (TR) not only leads to a decrease in WAT mass but also attenuates obesity-induced dysregulated expression of the inflammation-related adipokines in WAT. Therefore, TR is widely used as a tool for preventing and improving lifestyle-related diseases. This review outlines the impact of TR on the expression and secretory response of adipokines in WAT.
TL;DR: The temperature-dependent magnetic susceptibilities indicated a ferromagnetic interaction between the Ni(II) and Ln(III) ions for all of the complexes, with a distinctly different magnetic behavior between the two series in the lowest-temperature region due to the Ln (III)-Ln( III) magnetic interaction and/or different magnetic anisotropies of the Tb (III) or Dy(III).
Abstract: Atmospheric CO2 fixation of [Ni(II)(3-MeOsaltn)(H2O)2]·2.5H2O [3-MeOsaltn = N,N'-bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato], Ln(III)(NO3)3·6H2O, and triethylamine occurred in methanol/acetone, giving a first series of carbonato-bridged Ni(II)2Ln(III)2 complexes [(μ4-CO3)2{Ni(II)(3-MeOsaltn)(MeOH)Ln(III)(NO3)}2] (1Gd, 1Tb, and 1Dy). When the reaction was carried out in acetonitrile/water, it gave a second series of complexes [(μ4-CO3)2{Ni(II)(3-MeOsaltn)(H2O)Ln(III)(NO3)}2]·2CH3CN·2H2O (2Gd, 2Tb, and 2Dy). For both series, each Ni(II)2Ln(III)2 structure can be described as two di-μ-phenoxo-bridged Ni(II)Ln(III) binuclear units bridged by two carbonato CO3(2-) units to form a carbonato-bridged (μ4-CO3)2{Ni(II)2Ln(III)2} structure. The high-spin Ni(II) ion has octahedral coordination geometry, and the Ln(III) ion is coordinated by O9 donor atoms from Ni(II)(3-MeOsaltn), bidentate NO3(-), and one and two oxygen atoms of two CO3(2-) ions. The NO3(-) ion for the first series roughly lie on Ln-O(methoxy) bonds and are tilted toward the outside, while for the second series, the two oxygen atoms roughly lie on one of the Ln-O(phenoxy) bonds due to the intramolecular hydrogen bond. The temperature-dependent magnetic susceptibilities indicated a ferromagnetic interaction between the Ni(II) and Ln(III) ions (Ln(III) = Gd(III), Tb(III), Dy(III)) for all of the complexes, with a distinctly different magnetic behavior between the two series in the lowest-temperature region due to the Ln(III)-Ln(III) magnetic interaction and/or different magnetic anisotropies of the Tb(III) or Dy(III) ion. Alternating-current susceptibility measurements under the 0 and 1000 Oe direct-current (dc) bias fields showed no magnetic relaxation for the Ni(II)2Gd(III)2 complexes but exhibited an out-of-phase signal for Ni(II)2Tb(III)2 and Ni(II)2Dy(III)2, indicative of slow relaxation of magnetization. The energy barriers, Δ/kB, for the spin flipping were estimated from the Arrhenius plot to be 12.2(7) and 6.1(3) K for 1Tb and 2Tb, respectively, and 18.1(6) and 14.5(4) K for 1Dy and 2Dy, respectively, under a dc bias field of 1000 Oe. Compound 1Dy showed relatively slow relaxation of magnetization reorientation even at zero dc applied field with Δ/kB = 6.6(4) K.
28 Nov 2013
TL;DR: Unified proof of impossibility, namely, the lower bounds on key sizes are derived based on conditional Renyi entropies, and a new optimal symmetric key encryption protocol achieving the higher bounds is proposed.
Abstract: In this paper, information theoretic cryptography is discussed based on conditional Renyi entropies. Our discussion focuses not only on cryptography but also on the definitions of conditional Renyi entropies and the related information theoretic inequalities. First, we revisit conditional Renyi entropies, and clarify what kind of properties are required and actually satisfied. Then, we propose security criteria based on Renyi entropies, which suggests us deep relations between (conditional) Renyi entropies and error probabilities by using several guessing strategies. Based on these results, unified proof of impossibility, namely, the lower bounds on key sizes are derived based on conditional Renyi entropies. Our model and lower bounds include the Shannon’s perfect secrecy, and the min-entropy based encryption presented by Dodis, and Alimomeni and Safavi-Naini at ICITS2012. Finally, a new optimal symmetric key encryption protocol achieving the lower bounds is proposed.
TL;DR: The Stark splitting of the ground state was so evaluated, and the energy pattern indicates a strong easy axis (Ising type) anisotropy, indicative of single molecule magnet.
Abstract: Carbonato-bridged ZnII2LnIII2 complexes [(μ4-CO3)2{ZnIILnLnIII(NO3)}2]·solvent were synthesized through atmospheric CO2 fixation reaction of [ZnIILn(H2O)2]·xH2O, LnIII(NO3)3·6H2O, and triethylamine, where LnIII = GdIII, TbIII, DyIII; L1 = N,N′-bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato, L2 = N,N′-bis(3-ethoxy-2-oxybenzylidene)-1,3-propanediaminato. Each ZnII2LnIII2 structure possessing an inversion center can be described as two di-μ-phenoxo-bridged {ZnIILnLnIII(NO3)} binuclear units bridged by two carbonato CO32– ions. The ZnII ion has square pyramidal coordination geometry with N2O2 donor atoms of Ln and one oxygen atom of a bridging carbonato ion at the axial site. LnIII ion is coordinated by nine oxygen atoms consisting of four from the deprotonated Schiff-base Ln, two from a chelating nitrate, and three from two carbonate groups. The temperature-dependent magnetic susceptibilities in the range 1.9–300 K, field-dependent magnetization from 0 to 5 T at 1.9 K, and alternating current magnetic ...
TL;DR: In this article, the authors theoretically and experimentally investigate the spectral tunability and purity of photon pairs generated from spontaneous parametric down conversion in periodically poled KTiOPO_4$ crystal with group-velocity matching condition.
Abstract: We theoretically and experimentally investigate the spectral tunability and purity of photon pairs generated from spontaneous parametric down conversion in periodically poled $\mathrm{KTiOPO_4}$ crystal with group-velocity matching condition. The numerical simulation predicts that the purity of joint spectral intensity ($P_{JSI}$) and the purity of joint spectral amplitude ($P_{JSA}$) can be kept higher than 0.98 and 0.81, respectively, when the wavelength is tuned from 1460 nm to 1675 nm, which covers the S-, C-, L-, and U-band in telecommunication wavelengths. We also directly measured the joint spectral intensity at 1565 nm, 1584 nm and 1565 nm, yielding $P_{JSI}$ of 0.989, 0.983 and 0.958, respectively. Such a photon source is useful for quantum information and communication systems.
TL;DR: The final two-colour correction of the refractive index of air over a path length of 61 m was demonstrated to exhibit an uncertainty better than 1.4 × 10−8, which is the best result ever reported without precise knowledge of environmental parameters.
Abstract: Optical frequency combs have become an essential tool for distance metrology, showing great advantages compared with traditional laser interferometry. However, there is not yet an appropriate method for air refractive index correction to ensure the high performance of such techniques when they are applied in air. In this study, we developed a novel heterodyne interferometry technique based on two-colour frequency combs for air refractive index correction. In continuous 500-second tests, a stability of 1.0 × 10−11 was achieved in the measurement of the difference in the optical distance between two wavelengths. Furthermore, the measurement results and the calculations are in nearly perfect agreement, with a standard deviation of 3.8 × 10−11 throughout the 10-hour period. The final two-colour correction of the refractive index of air over a path length of 61 m was demonstrated to exhibit an uncertainty better than 1.4 × 10−8, which is the best result ever reported without precise knowledge of environmental parameters.
TL;DR: A high-dynamic-range two-dimensional phase measurement system that does not need phase unwrapping processing was developed and the optical path difference distribution about three wavelengths could be measured, demonstrating the high dynamic-range of this system.
Abstract: Experiments for cell identification are presented using a high-precision cell phase measurement system that does not require any phase unwrapping. This system is based on a Mach–Zehnder interferometer using a phase-locking technique, and it measures the change in optical path length while the sample is scanned across the optical axis. The spatial resolution is estimated to be less than 1.1 μm. The sensitivity of optical path length difference is estimated to be less than 2 nm. Using experiments, we investigate the potential of this approach for cancer cell identification. In our preliminary experiments, cancer cells were distinguished from normal cells through comparison of optical path length differences.
TL;DR: In this paper, electric field-induced magnetization switching through magnetization precession is investigated as a function of in-plane component of external magnetic field for a CoFeB/MgO-based magnetic tunnel junction with perpendicular easy axis.
Abstract: Electric field-induced magnetization switching through magnetization precession is investigated as a function of in-plane component of external magnetic field for a CoFeB/MgO-based magnetic tunnel junction with perpendicular easy axis. The switching probability is an oscillatory function of the duration of voltage pulses and its magnitude and period depend on the magnitude of in-plane magnetic field. Experimental results are compared with simulated ones by using Landau-Lifshitz-Gilbert-Langevin equation, and possible factors determining the probability are discussed.
TL;DR: The development of a multiplex stimulated Raman microscope for spectral imaging through multi-channel lock-in detection with a single light source and the observation of pseudo-continuous stimulated Ramen spectra is reported, demonstrating the strong ability of qualitative analysis to identify various types of C-H stretching modes such as the symmetric and asymmetric modes of the methylene∕methyl and aromatic groups.
Abstract: We report the development of a multiplex stimulated Raman microscope for spectral imaging through multi-channel lock-in detection with a single light source. A white pump beam is prepared with a piece of photonic crystal fiber (PCF). The system does not require the synchronization of plural light sources or the scanning of their wavelengths, and thus a jitter-free pair of pump and Stokes beams is obtained, and a high degree of temporal synchronization is attained in the spectra. The multi-channel lock-in detection (extended to 128 channels) enables the observation of pseudo-continuous stimulated Raman spectra, demonstrating the strong ability of qualitative analysis to identify various types of C–H stretching modes such as the symmetric and asymmetric modes of the methylene/methyl and aromatic groups. Images of a mixed film of polystyrene and polymethylmethacrylate are presented to demonstrate the system's spectral imaging ability. The spatial distribution of these materials is successfully captured through one-time imaging, although the noise of the white light pump beam generated with the PCF limits the system's imaging speed.
TL;DR: In this article, a wide field (0.17-deg2) and high-angular resolution (21''3 ~ 0.04-pc) observations were carried out in the [C I] line toward the Orion-A giant molecular cloud with the Atacama Submillimeter Telescope Experiment 10m telescope in the On-The-Fly mode.
Abstract: We have carried out wide-field (0.17 deg2) and high-angular resolution (21.''3 ~ 0.04 pc) observations in the [C I] line toward the Orion-A giant molecular cloud with the Atacama Submillimeter Telescope Experiment 10 m telescope in the On-The-Fly mode. The overall features of the [C I] emission are similar to those of the 12CO (J = 1-0) emission by Shimajiri et al. in 2011; the total intensity ratio of the [C I] to CO emission ranges from 0.05 to 0.2. The optical depth of the [C I] emission is found to be 0.1-0.75, suggesting optically thin emission. The column density of the [C I] emission is estimated to be (1.0-19) × 1017 cm–2. These results are consistent with the results of the previous [C I] observations with a low-angular resolution of 2.'2. In the nearly edge-on photon-dominated regions (PDRs) and their candidates of the Orion Bar, DLSF, M 43 Shell, and Region D, the distributions of the [C I] emission coincide with those of the 12CO emission, inconsistent with the prediction by the plane-parallel PDR model. In addition, the [C I] distribution in the Orion A cloud is found to be more similar to those of the 13CO (J = 1-0), C18O (J = 1-0), and H13CO+ (J = 1-0) lines than that of the 12CO (J = 1-0) line, suggesting that the [C I] emission is not limited to the cloud surface, but is tracing the dense, inner parts of the cloud.
TL;DR: It is demonstrated that thousands of periodic nano-craters are fabricated on a subwavelength-diameter tapered optical fiber, an optical nanofiber, by irradiating with just a single femtosecond laser pulse.
Abstract: We demonstrate that thousands of periodic nano-craters are fabricated on a subwavelength-diameter tapered optical fiber, an optical nanofiber, by irradiating with just a single femtosecond laser pulse. A key aspect of the fabrication is that the nanofiber itself acts as a cylindrical lens and focuses the femtosecond laser beam on its shadow surface. We also demonstrate that the periodic nano-crater array on the nanofiber shows polarization dependent fiber Bragg grating (FBG) characteristics. Such FBG structures on the nanofiber may act as a 1-D photonic crystal due to the strong transverse and longitudinal confinement of the field.
TL;DR: In this paper, the potential-dependent transformations of surface structures, Pt oxidation states, and Pt-O bondings in Pt/C, Au(core)-Pt(shell)/C, and Pd@Pt/C cathode catalysts in polymer electrolyte fuel cells during the voltage-stepping processes were characterized by in situ X-ray absorption fine structure (XAFS).
Abstract: Potential-dependent transformations of surface structures, Pt oxidation states, and Pt–O bondings in Pt/C, Au(core)-Pt(shell)/C (denoted as Au@Pt/C), and Pd(core)-Pt(shell)/C (denoted as Pd@Pt/C) cathode catalysts in polymer electrolyte fuel cells (PEFCs) during the voltage-stepping processes were characterized by in situ (operando) X-ray absorption fine structure (XAFS). The active surface phase of the Au@Pt/C for oxygen reduction reaction (ORR) was suggested to be the Pt3Au alloy layer on Au core nanoparticles, while that of the Pd@Pt/C was the Pt atomic layer on Pd core nanoparticles. The surfaces of the Pt, Au@Pt and Pd@Pt nanoparticles were restructured and disordered at high potentials, which were induced by strong Pt–O bonds, resulting in hysteresis in the structural and electronic transformations in increasing and decreasing voltage operations. The potential-dependent restructuring, disordering, and hysteresis may be relevant to hindered Pt performance, Pt dissolution to the electrolyte, and degra...
TL;DR: In this article, a grid-based numerical Hartree-fock approximation of the structure factor for the highest occupied molecular orbital (HOMO) is presented. But, for larger molecules, to solve the Hartreefock equations one should resort to basis-based approaches with too rapidly decaying Gaussian basis functions.
Abstract: Within the weak-field asymptotic theory, the dependence of the tunneling ionization rate of a molecule in a static electric field on its orientation with respect to the field is determined by the structure factor for the highest occupied molecular orbital (HOMO). An accurate determination of this factor, and hence the ionization rate, requires accurate values of the HOMO in the asymptotic region. Techniques for calculating the structure factors for molecules in the Hartree-Fock approximation are discussed. For diatomics, grid-based numerical Hartree-Fock calculations which reproduce the correct asymptotic tail of the HOMO are possible. However, for larger molecules, to solve the Hartree-Fock equations one should resort to basis-based approaches with too rapidly decaying Gaussian basis functions. A systematic study of the possibility to reproduce the asymptotic tail of the HOMO in calculations with Gaussian basis sets is presented. We find that polarization-consistent basis sets with quadruple or pentuple-zeta quality greatly improve the tail of the HOMO, but only when used with variationally optimized exponents. This methodology is validated by considering the CO molecule for which reliable grid-based calculations can be performed. The optimized Gaussian basis sets are used to calculate the structure factors for the triatomic molecules CO${}_{2}$ and OCS. The results are compared with available experimental and theoretical results.
TL;DR: In this article, a survey of medium-scale traveling ionospheric disturbances (MSTIDs) observed by a Super Dual Auroral Radar Network HF radar located in the Falkland Islands between May 2010 and April 2011 is presented.
Abstract: We present a survey of medium-scale traveling ionospheric disturbances (MSTIDs) observed by a Super Dual Auroral Radar Network HF radar located in the Falkland Islands between May 2010 and April 2011. The radar has a field of view that overlooks the Antarctic Peninsula, a known hot spot of gravity wave activity. We present observations of radar ground-backscatter data, in which the signatures of MSTIDs are manifested as structured enhancements in echo power. Observed periods were in the range 30–80 min, corresponding to frequencies of 0.2–0.6 mHz. Wavelengths were generally in the range 200–800 km and phase speeds in the range 100–300 m s−1. These values are within the ranges typically associated with medium-scale gravity waves. We find a primary population of northward (equatorward) propagating MSTIDs, which demonstrate an association with enhanced solar wind-magnetosphere coupling and a smaller, westward propagating population, that could be associated with atmospheric gravity waves excited by winds over the Andean and Antarctic Peninsula mountains or by the high winds of the Antarctic Polar Vortex.
01 Jan 2013
TL;DR: This paper proposes a travel route recommendation system which utilizes actual travel paths extracted from a large number of photos uploaded by many people on the Web.
Abstract: Due to the recent wide spread of camera devices with GPS, the number of geotagged photos on the Web is increasing rapidly. Some image retrieval systems and travel recommendation systems which make use of geotagged images on the Web have been proposed so far. While most of them handle a large number of geotagged images as a set of location points, in this paper we handle them as sequences of location points. We propose a travel route recommendation system which utilizes actual travel paths extracted from a large number of photos uploaded by many people on the Web.
TL;DR: In this article, a Hong-Ou-Mandel interference between two independent, intrinsically pure, heralded single photons from spontaneous parametric down-conversion (SPDC) at telecommunication wavelength was achieved without using any bandpass filter.
Abstract: We demonstrate a Hong-Ou-Mandel interference between two independent, intrinsically pure, heralded single photons from spontaneous parametric down-conversion (SPDC) at telecommunication wavelength. A visibility of $85.5\ifmmode\pm\else\textpm\fi{}8.3%$ was achieved without using any bandpass filter. Thanks to the group-velocity-matched SPDC and superconducting nanowire single-photon detectors (SNSPDs), the fourfold coincidence counts are one order higher than that in the previous experiments. The combination of bright single-photon sources and SNSPDs is a crucial step for future practical quantum infocommunication systems at telecommunication wavelength.
TL;DR: Simulation of translocation dynamics of a vesicle cell under collision with a Janus or a homogeneous hydrophobic/hydrophilic nanoparticle provides microscopic insights into the resilience of thevesicle-cell membrane and dynamical behavior of the vesicles under the attack of a foreign nanoparticle.
Abstract: We investigate translocation dynamics of a vesicle cell under collision with a Janus or a homogeneous hydrophobic/hydrophilic nanoparticle. To this end, we perform dissipative particle dynamics simulation by setting the nanoparticle with different initial velocities, different chemical patterns of the surface for the nanoparticle, and different orientations (for the Janus nanoparticle). Particular attention is given to translocation dynamics, in-cell water discharge, and the late-stage morphologies of the vesicle/nanoparticle system after the collision. We observe three late-stage states for the Janus nanoparticle, and four late-stage states for the homogeneous nanoparticles. We find that the late-stage state and the associated dynamical pathway not only depend on the relative velocity but also on the chemical pattern of the nanoparticle surface, as well as on the orientation of the incident Janus nanoparticle. We have examined the time-dependent mean radius of the vesicle, the number of in-cell water beads lost from the vesicle, as well as the collision-induced pore size on the lipid membrane during the course of collision. Our simulation provides microscopic insights into the resilience of the vesicle-cell membrane and dynamical behavior of the vesicle under the attack of a foreign nanoparticle. Knowledge and insights gained through the simulation will have implication to the drug delivery with different chemical coatings.
TL;DR: In this article, the authors presented a method to detect the presence of a virus in the human brain using the Web of Science Record (WRSR) created on 2014-01-09, modified on 2017-05-12.
Abstract: Reference EPFL-ARTICLE-195580doi:10.1002/adom.201300221View record in Web of Science Record created on 2014-01-09, modified on 2017-05-12