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A nitrogen vacancy (NV) center in diamond is a promising platform for the study of quantum sensing and quantum many-body physics. It is essential for such study to realize a system in which NV centers interact with one another. This requires the fabrication of highly concentrated NV centers, as the centers must exist within a few nanometers of one another. Only a few such samples have been fabricated, because the required irradiation of several-MV electron beams over long periods makes such sample preparation difficult. Here, highly concentrated NV ensembles ([NV] = 8.5 × 1018 cm-3) were created by narrowing the electron beam of a transmission electron microscope to generate large amounts of vacancies in highly concentrated nitrogen-doped CVD diamond ([N] = 8 × 1020 cm-3). This result reduces the difficulty of producing high-concentration NV ensembles and is expected to promote the development of many-body quantum physics.

The nitrogen vacancy (NV) center in diamond is fascinating and has a long spin coherence time. It is applied to magnetic sensors with high sensitivity (∼fT). To achieve a high sensitivity, an aligned NV ensemble is required. This paper presents a new methodology for the fabrication of two-dimensional (2D) aligned NV ensembles by using nitrogen-terminated (111) surface. To realize this, pure diamond growth and high nitrogen coverage on (111) surface were performed. As a result, we have succeeded in producing 2D NV ensembles, with 1 × 109 cm−2. Coherence time T2 was 2.45 μs. Also, Using dynamical decoupling, the decoherence sources were revealed. The alignment ratio along [111] axis was archived 60%. Thermal annealing of the nitrogen termination was introduced to improve the alignment ratio. After that, the alignment rate was up to 73%. This report shows that the aligned 2D NV ensemble has possibility to be applied for multiple quantum devices.

We demonstrated the correlation spectroscopy of organosilane monolayers using an ensemble of shallow nitrogen-vacancy centers as the quantum sensor. Several types of organosilane monolayers were grown directly on the diamond surface by exposing the surface to a silane precursor vapor. The feasibility of detecting 1H and 19F in the monolayer was examined by correlation spectroscopy measurements. The effect of the magnetic dipole–dipole interaction on the peak width was also discussed by comparing the spectrum of the monolayer with that of surface-attached 1H and that of immersion oil. The results highlight the feasibility of nitrogen-vacancy centers as the spin probe for physicochemical analyses of monolayers grown on the diamond surface.

Neurostimulation is an essential technique to trigger and modulate the spatiotemporal activity of local neuronal circuits. Current stimulation methods have a trade-off relationship among aiming precision, temporal resolution, and noninvasiveness, making it difficult to stimulate and monitor a single target neuron for a long term. Here, we show that a method using two needle electrodes in combination of micropatterning techniques provides new possibilities for targeting and stimulating a single neuron selectively. Results of physiological experiments as well as analog circuit simulation reveal that two needle electrodes can stimulate a target neuron selectively by placing the two needle electrodes in proximity to and to straddle the target neuron, and that the steepness of voltage applied to two needle electrodes is important for the target neuron to fire at a low voltage. The proposed method enables a noninvasive stimulation suitable for measuring long-term activity of local neuronal circuits.

The nitrogen-vacancy (NV) center in diamond is the most promising candidate for quantum sensing because of its beneficial properties. For quantum-sensing applications, a shallow NV center is critic...

Special point defects in semiconductors have been envisioned as suitable components for quantum-information technology. The identification of new deep centers in silicon that can be easily activated and controlled is a main target of the research in the field. Vacancy-related complexes are suitable to provide deep electronic levels but they are hard to control spatially. With the spirit of investigating solid state devices with intentional vacancy-related defects at controlled position, here we report on the functionalization of silicon vacancies by implanting Ge atoms through single-ion implantation, producing Ge-vacancy (GeV) complexes. We investigate the quantum transport through an array of GeV complexes in a silicon-based transistor. By exploiting a model based on an extended Hubbard Hamiltonian derived from ab-initio results we find anomalous activation energy values of the thermally activated conductance of both quasi-localized and delocalized many-body states, compared to conventional dopants. We identify such states, forming the upper Hubbard band, as responsible of the experimental sub-threshold transport across the transistor. The combination of our model with the single-ion implantation method enables future research for the engineering of GeV complexes towards the creation of spatially controllable individual defects in silicon for applications in quantum information technologies.

In anatomical charts in conventional books, the pathways of nerve fibers are drawn in illustrations. Conversely, with diffusion tensor tractography (DTT), we can visually understand the trajectory of nerve fibers through color. We created a stereo color anatomical chart of the nerve fibers that can be used for magnetic resonance (MR) examination to diagnose the pathway of nerve fibers and that can be used to explain the results of MR examination to visually understand how nerve fiber information is transmitted from the frontal lobe, parietal lobe, occipital lobe, temporal lobe, cerebellar lobe, and cerebral cortex.

Employment of erbium in silicon devices suffers of difficulties preventing to act as reliable photon source. We review the convergence between single ion implantation and few photon emission regime at room temperature at 1550 nm.

Background noise in biological cortical microcircuits constitutes a powerful resource to assess their computational tasks, including, for instance, the synchronization of spiking activity, the enhancement of the speed of information transmission, and the minimization of the corruption of signals. We explore the correlation of spontaneous firing activity of ≈ 100 biological neurons adhering to engineered scaffolds by governing the number of functionalized patterned connection pathways among groups of neurons. We then emulate the biological system by a series of noise-activated silicon neural network simulations. We show that by suitably tuning both the amplitude of noise and the number of synapses between the silicon neurons, the same controlled correlation of the biological population is achieved. Our results extend to a realistic silicon nanoelectronics neuron design using noise injection to be exploited in artificial spiking neural networks such as liquid state machines and recurrent neural networks for stochastic computation.

Quantum information processing requires quantum registers based on coherently interacting quantum bits. The dipolar couplings between nitrogen vacancy (NV) centres with nanometre separation makes them a potential platform for room-temperature quantum registers. The fabrication of quantum registers that consist of NV centre arrays has not advanced beyond NV pairs for several years. Further scaling up of coupled NV centres by using nitrogen implantation through nanoholes has been hampered because the shortening of the separation distance is limited by the nanohole size and ion straggling. Here, we demonstrate the implantation of C5N4Hn from an adenine ion source to achieve further scaling. Because the C5N4Hn ion may be regarded as an ideal point source, the separation distance is solely determined by straggling. We successfully demonstrate the fabrication of strongly coupled triple NV centres. Our method may be extended to fabricate small quantum registers that can perform quantum information processing at room temperature., There is an extensive literature discussing the potential applications of individual nitrogen vacancy centres but some proposed developments require the use of multiple, coupled defects. Here the authors demonstrate a method to fabricate coupled nitrogen vacancy centre triplets.

We report on the photocurrent induced by 1550 nm laser irradiation in a Er-doped micron-scale silicon transistor. The erbium defects, activated in the channel of the transistor thanks to oxygen codoping, make it possible to observe a resonant photocurrent at telecom wavelength and at room temperature by using a supercontinuum laser source working in the $\mu\mathrm {W}$ range. By exploiting a back-gate, the transistor is tuned to exploit only the electrons lying in the Er-O states. We estimate a relatively small number of photoexcited atoms $(\sim 4\times 10^{4})$ making Er-dpoed silicon a candidate for designing resonance-based frequency selective single photon detectors at 1550 nm for quantum communications.

An erbium-doped silicon transistor prepared by ion implantation and co-doped with oxygen is investigated by photocurrent generation in the telecommunication range. The photocurrent is explored at room temperature as a function of the wavelength by using a supercontinuum laser source working in the &mu, W range. The 1-&mu, m2 transistor is tuned to involve in the transport only those electrons lying in the Er-O states. The spectrally resolved photocurrent is characterized by the typical absorption line of erbium and the linear dependence of the signal over the impinging power demonstrates that the Er-doped transistor is operating far from saturation. The relatively small number of estimated photoexcited atoms (&asymp, 4 &times, 10 4 ) makes Er-dpoed silicon potentially suitable for designing resonance-based frequency selective single photon detectors at 1550 nm.

Single neurons in an autaptic culture exhibit various types of firing pattern with different firing durations and rhythms. However, a neuron with autapses has often been modeled as an oscillator providing a monotonic firing pattern with a constant periodicity because of the lack of a mathematical model. In the work described in this study, we use computational simulation and whole-cell patch-clamp recording to elucidate and model the mechanism by which such neurons generate various firing pattens. In the computational simulation, three types of spontaneous firing pattern, i.e., short, long-lasting, and periodic burst firing patterns are realized by changing the combination ratio of N-methyl-d-aspartate (NMDA) to α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) conductance. These three types of firing patterns are also observed in the experiments where neurons are cultured in isolation on micropatterned substrates. Using the AMPA and NMDA current models, we discuss that, in principle, autapses can regulate rhythmicity and information selection in neuronal networks.

BACKGROUND: Electrical stimulation of neurons is essential to control neuronal activities. Thus far, direct stimulation by whole-cell patch-clamp methods [1] and extracellular stimulation using multi-electrode arrays (MEAs) [2] have been performed commonly. While the whole-cell patch-clamp method merits from the precise control of stimulation, the use of MEAs takes advantage of maintaining neuronal activity over a long period owing to its non-invasiveness. An optogenetic technique [3] has a targeting precision of a single-cell level, but this has difficulties in applying fast stimulation patterns due to the slow photoresponse of opsin [4]. Alternative non-invasive methods capable of targeting a single neuron with arbitrary stimulation patterns open new possibility of controlling and monitoring neuronal activities over a long duration. In this presentation, we propose a novel method to combine cell-patterning techniques [5] with electrical stimulation of a target cell with a pair of needle electrodes [6]. We show that the firing of a single neuron cultured on the micropattern can be controlled by the proposed method. We also show the controllability of the stimulation by analogue circuit simulation of a neuron stimulated electrically by a pair of needle electrodes via culture medium. EXPERIMENTAL METHODS: Neurons were cultured on a micropatterned glass substrates in isolation. A pair of tungsten needles except for their tip apexes were coated with an insulating polymer and mounted on manipulators. Two needles were immersed in the medium so that the target neuron is placed in-between. The distance from the neuron to the needle tip was controlled to be several tens to 100 μm. A bipolar square pulse was applied between electrodes, and the neuronal activity was visualized by Ca imaging. SIMULATION: The membrane potential response of a neuron to extracellular stimulation was analysed using LTspice simulator [7]. The circuit model is shown in Fig. 1a. The integrate-and-fire neuron was connected electrically with two needle electrodes via the electric double layers and solution resistances. The key of the circuit simulation is to divide the neuron into two compartments, each is stimulated with either of two needle electrodes. We conjecture that the neuron fires if the membrane potential either of two compartments exceeds the threshold upon the electrical stimulation. We investigated the membrane potential response when the resistance corresponding to the relative distance from the neuron to the electrode, the capacitive component of the needles, and the shape of voltage input pulses were changed. RESULTS AND DISSCUSSION: As shown in Fig. 1b, the neuron fires if the amplitude of the bipolar square pulse exceeds 5 Vp-p. The amplitude required for the neuron firing decreases with increasing distance from the neuron to the needle electrodes. The LTspice simulation provided the following results: (i) The positive electrode hyperpolarizes the membrane potential, whereas the negative electrode depolarizes it, indicating the membrane potential of two compartments changes to inverse direction even if a bipolar pulse was applied, as shown in Fig. 1c. (ii) The closer the electrode is to the cell, the more the membrane potential of the neuron changes and the voltage drop in the solution resistance is comparatively small. (iii) The main factor of neuronal firing is the transient potential fluctuation caused by the capacitive component of the electrical double layer and the neuronal membrane. (iv) The membrane potential of both the compartments is sensitive to transient change of tip voltage and does not change if the system reaches the steady state. This is also true if the DC voltage is continuously applied. These results indicate that applying a voltage pulse of appropriate amplitude can stimulate only cells in the vicinity of needle electrodes. Only a single neuron in neuronal culture can be stimulated by the needle electrodes by placing the target neuron between two needles. The non-invasive stimulation can also be used for long-term stimulation and monitoring. [1] E. Neher, et al., Nature 260(1976) 799. [2] C.A. Thomas Jr., et al., Exp. Cell Res. 74(1972) 61. [3] K. Deisseroth, et al., J. Neurosci. 26(2006) 10380. [4] B.D. Allen, et al., Learn. Mem. 22(2015) 232. [5] L. Bekar, et al., Nat. Med. 14(2008) 75. [6] H. Yamamoto, et al., Appl. Phys. Lett. 113(2018) 133703. [7] https://www.analog.com/en/design-center/design-tools-and-calculators/ltspice-simulator.html# Figure 1

The main constituent of green tea, (-)-Epigallocatechin-3-O-gallate (EGCG), is known to have cancer-specific chemopreventive effects. In the present work, we investigated how EGCG suppresses cell adhesion by comparing the adhesion of human pancreatic cancer cells (AsPC-1 and BxPC-3) and their counterpart, normal human embryonic pancreas-derived cells (1C3D3), in catechin-containing media using organosilane monolayer templates (OMTs). The purpose of this work is (1) to evaluate the quantitativeness in the measurement of cell adhesion with the OMT and (2) to show how green-tea catechins suppress cell adhesion in a cancer-specific manner. For the first purpose, the adhesion of cancer and normal cells was compared using the OMT. The cell adhesion in different type of catechins such as EGCG, (-)-Epicatechin-3-O-gallate (ECG) and (-)-Epicatechin (EC) was also evaluated. The measurements revealed that the anti-adhesion effect of green-tea catechins is cancer-specific, and the order is EGCG≫ECG>EC. The results agree well with the data reported to date, showing the quantitativeness of the new method. For the second purpose, the contact area of cells on the OMT was measured by reflection interference contrast microscopy. The cell-OMT contact area of cancer cells decreases with increasing EGCG concentration, whereas that of normal cells remains constant. The results reveal a twofold action of EGCG on cancer cell adhesion-suppressing cell attachment to a candidate adhesion site and decreasing the contact area of the cells-and validates the use of OMT as a tool for screening cancer cell adhesion.

Summary Inter-story drift displacement data can provide useful information for story damage assessment. The authors' research group has developed photonic-based sensors for the direct measurement of inter-story drift displacements. This paper proposes a scheme for evaluating the degree of damage in a building structure based on drift displacement sensing. The scheme requires only measured inter-story drift displacements without any additional finite element analysis. A method for estimating yield drift deformation is proposed, and then, the degree of beam end damage is evaluated based on the plastic deformation ratios derived with the yield drift deformation values estimated by the proposed method. The validity and effectiveness of the presented scheme are demonstrated via experimental data from a large-scale shaking table test of a one-third-scale model of an 18-story steel building structure conducted at E-Defense. Copyright © 2016 John Wiley & Sons, Ltd.

Adhesion of cancer cells with different metastatic potential and anticancer drug resistance has been quantitatively evaluated by using self-assembled monolayer (SAM)-patterned substrates and reflection interference contrast microscopy (RICM). Cell-adhesive SAM spots with optimized diameter could prevent cell-cell adhesion and thus allowed the systematic evaluation of statistically reliable numbers of contact area between single cancer cells and substrates by RICM. The statistical image analysis revealed that highly metastatic mouse melanoma cells showed larger contact area than lowly metastatic cells. We also found that both cancer cell types exhibited distinct transition from the "strong" to "weak" adhesion states with increase in the concentration of (-)-epigallocatechin gallate (EGCG), which is known to exhibit cancer preventive activity. Mathematical analysis of the adhesion transition revealed that adhesion of the highly metastatic mouse melanoma cells showed more EGCG tolerance than that of lowly metastatic cells. Moreover, time-lapse RICM observation revealed that EGCG weakened cancer cell adhesion in a stepwise manner, probably via focal adhesion complex. These results clearly indicate that contact area can be used as a quantitative measure for the determination of cancer phenotypes and their drug resistance, which will provide physical insights into the mechanism of cancer metastasis and cancer prevention.

The simultaneous control of the number and position of negatively charged nitrogen-vacancy (NV) centers in diamond was achieved. While single near-surface NV centers are known to exhibit outstanding capabilities in external spin sensing, trade-off relationships among the accuracy of the number and position, and the coherence of NV centers have made the use of such engineered NV centers difficult. Namely, low-energy nitrogen implantation with lithographic techniques enables the nanoscale position control but results in degradation of the creation yield and the coherence property. In this paper, we show that low-energy nitrogen ion implantation to a 12C (99.95%)-enriched homoepitaxial diamond layer using nanomask is applicable to create shallow NV centers with a sufficiently long coherence time for external spin sensing, at a high creation yield. Furthermore, the NV centers were arranged in a regular array so that 40% lattice sites contain single NV centers. The XY8-k measurements using the individual NV centers reveal that the created NV centers have depths from 2 to 12 nm, which is comparable to the stopping range of nitrogen ions implanted at 2.5 keV. We show that the position-controlled NV centers are capable of external spin sensing with a ultra-high spatial resolution., publishedVersion

We characterize germanium-vacancy GeVn complexes in silicon using first-principles Density Functional Theory calculations with screening-dependent hybrid functionals. We report on the local geometry and electronic excited states of these defects, including charge transition levels corresponding to the addition of one or more electrons to the defect. Our main theoretical result concerns the GeV complex, which we show to give rise to two excited states deep in the gap, at -0.51 and -0.35 eV from the conduction band, consistently with the available spectroscopic data. The adopted theoretical scheme, suitable to compute a reliable estimate of the wavefunction decay, leads us to predict that such states are associated to an electron localization over a length of about 0.45 nm. By combining the electronic properties of the bare silicon vacancy, carrying deep states in the band gap, with the spatial controllability arising from single Ge ion implantation techniques, the GeVn complex emerges as a suitable ingredient for silicon-based room-temperature single-atom devices.

The authors\' research group has developed a noncontact type of sensors which directly measure the inter-story drift displacements of a building during a seismic event. Soon after that event, such seismically-induced drift displacement data would provide structural engineers with useful information to judge how the stories have been damaged. This paper presents a scheme of estimating the story cumulative plastic deformation ratios based on such measured drift displacement information toward the building safety monitoring. The presented scheme requires the data of story drift displacements and the ground motion acceleration. The involved calculations are rather simple without any detailed information on structural elements required: the story hysteresis loops are first estimated and then the cumulative plastic deformation ratio of each story is evaluated from the estimated hysteresis. The effectiveness of the scheme is demonstrated by utilizing the data of full-scale building model experiment performed at E-defense and conducting numerical simulations.

The demand for single photon emitters at λ=1.54 μm, which follows from the consistent development of quantum networks based on optical fiber technologies, makes Er:O

It has been reported that erbium (Er) is a source of optical emission at λ=1.54 pm due to 4I 13/2 →4I 15/2 transition of Er3+. A method of oxygen (O) codoping with Er has attracted attention as a candidate for obtaining more efficient optical gain by forming Er:O complex. Although several simulations predict the equilibrium structure of Er:O complex, it is difficult to understand experimentally how related between these implanted ions followed by annealing for optical activation. In this workshop, we reported the preliminary results on three-dimensional distributions of Er and O co-implanted into Si investigated by atom probe tomography.

Luminescence of erbium in silicon has been intensively explored in the past in the high power emission regime, but its employment for manufacturability of active components for silicon photonics proved unfeasible. We explore the room-temperature photoluminescence (PL) at the telecomm wavelength of very low implantation doses of ErO x in Si for accessing few photon regime towards single photon emission. We achieve countable photon regime and we assess the lower-bound number of detectable emission centers by micron scale implanted dots, whose emission is collected by an inverted confocal microscope.

Nanoscale electronic devices will require the placement of dopants in a predetermined location, namely, a single atom control to explore novel functions for future nanoelectronics. Deterministic doping method, i.e. single-ion implantation, realizes ordered arrays of single-atoms in silicon, diamond and other materials, which might provide opportunities to single-dopant transport or single-photon source beneficial to quantum processing.

We study the effect of network size on synchronized activity in living neuronal networks. Dissociated cortical neurons form synaptic connections in culture and generate synchronized spontaneous activity within 10 days in vitro. Using micropatterned surfaces to extrinsically control the size of neuronal networks, we show that synchronized activity can emerge in a network as small as 12 cells. Furthermore, a detailed comparison of small (∼20 cells), medium (∼100 cells), and large (∼400 cells) networks reveal that synchronized activity becomes destabilized in the small networks. A computational modeling of neural activity is then employed to explore the underlying mechanism responsible for the size effect. We find that the generation and maintenance of the synchronized activity can be minimally described by: (1) the stochastic firing of each neuron in the network, (2) enhancement in the network activity in a positive feedback loop of excitatory synapses, and (3) Ca-dependent suppression of bursting activity. The model further shows that the decrease in total synaptic input to a neuron that drives the positive feedback amplification of correlated activity is a key factor underlying the destabilization of synchrony in smaller networks. Spontaneous neural activity plays a critical role in cortical information processing, and our work constructively clarifies an aspect of the structural basis behind this.

Hippocampal granule cells (GCs) are generated throughout the lifetime and are properly incorporated into the innermost region of the granule cell layer (GCL). Hypotheses for the well-regulated lamination of newly generated GCs suggest that polysialic acid (PSA) is present on the GC surface to modulate GC-to-GC interactions, regulating the process of GC migration; however, direct evidence of this involvement is lacking. We show that PSA facilitates the migration of newly generated GCs and that the activity of N-acetyl-α-neuraminidase 1 (NEU1, sialidase 1) cleaves PSA from immature GCs, terminating their migration in the innermost GCL. Developing a migration assay of immature GCs in vitro, we found that the pharmacological depletion of PSA prevents the migration of GCs, whereas the inhibition of PSA degradation with a neuraminidase inhibitor accelerates this migration. We found that NEU1 is highly expressed in immature GCs. The knockdown of NEU1 in newly generated GCs in vivo increased PSA presence on these cells, and attenuated the proper termination of GC migration in the innermost GCL. In conclusion, this study identifies a novel mechanism that underlies the proper lamination of newly generated GCs through the modulation of PSA presence by neuronal NEU1.

Formation of an axon is the first morphological evidence of neuronal polarization, visible as a profound outgrowth of the axon compared with sibling neurites. One unsolved question on the mechanism of axon formation is the role of axon outgrowth in axon specification. This question was difficult to assess, because neurons freely extend their neurites in a conventional culture. Here, we leveraged surface nano/micro-modification techniques to fabricate a template substrate for constraining neurite lengths of cultured neurons. Using the template, we asked (i) Do neurons polarize even if all neurites cannot grow sufficiently long? (ii) Would the neurite be fated to become an axon if only one was allowed to grow long? A pattern with symmetrical short paths (20 μm) was used to address the former question, and an asymmetrical pattern with one path extended to 100 μm for the latter. Axon formation was evaluated by tau-1/MAP2 immunostaining and live-cell imaging of constitutively-active kinesin-1. We found that (1) neurons cannot polarize when extension of all neurites is restricted and that (2) when only a single neurite is permitted to grow long, neurons polarize and the longest neurite becomes the axon. These results provide clear evidence that axon outgrowth is required for its specification.