Finding new ways to control and slow down the group velocity of light in media remains a major challenge in the field of optics. For the design of plasmonic slow light structures, graphene represents an attractive alternative to metals due to its strong field confinement, comparably low ohmic loss and versatile tunability. Here we propose a novel nanostructure consisting of a monolayer graphene on a silicon based graded grating structure. An external gate voltage is applied to graphene and silicon, which are separated by a spacer layer of silica. Theoretical and numerical results demonstrate that the structure exhibits an ultra-high slowdown factor above 450 for the propagation of surface plasmon polaritons (SPPs) excited in graphene, which also enables the spatially resolved trapping of light. Slowdown and trapping occur in the mid-infrared wavelength region within a bandwidth of ~2.1 μm and on a length scale less than 1/6 of the operating wavelength. The slowdown factor can be precisely tuned simply by adjusting the external gate voltage, offering a dynamic pathway for the release of trapped SPPs at room temperature. The presented results will enable the development of highly tunable optoelectronic devices such as plasmonic switches and buffers. Here, the slowdown factor or group index relative to free space is defined as gc/v47789101112131415161819202122et al. first observed a slowdown of a SPP mode in a metallic Bragg grating by a factor of 2et al. proposed a graded grating structure to reduce the speed of light and realize a rainbow trapping effect on a metal surface19Optical signals in a medium of refractive index et al. found that graphene with spatially modulated conductivity patterns can be used as a one-atom-thick platform for transformation opticset al. showed that graphene sheet arrays are capable of steering light efficiently through the SPP coupling between individual monolayers2631Graphene, a two-dimensional monolayer of carbon atoms arranged in a honeycomb lattice, exhibits exceptional electronic, mechanical and optical properties242627282930313233343536373839404142Here, we propose a novel structure composed of a monolayer graphene and a silicon based graded grating structure. Graphene and silicon are separated by a silica spacer layer and the surface conductivity of graphene can be tuned via an external gate voltage. We theoretically and numerically demonstrate that the SPP mode in graphene shows an exceptional slowdown factor above 450 with a broad bandwidth of ~2.1 μm in the mid-infrared optical region. Furthermore, the length of graphene structure is about 1/6 of the operating wavelength. Such a small size possesses a huge potential for the realization of on-chip optoelectronic components. The slowdown factor as well as the rainbow trapping performance of the system can be readily controlled via the external gate voltage, rendering the release of trapped waves feasible at room temperature.h . A previous report showed that μ = 230000 cm2V−1s−1 could be obtained experimentally in high-quality suspended graphene2 substrate could reach 40000 cm2V−1s−1 at room temperatureμ = 20000 cm2V−1s−1 is chosen in our studyvf is set as 106 m/ssn) shows a linear dependence on the external gate voltage described by the following equation47In graphene, dε is the relative permittivity of SiO2 layer. Accordingly, sn can be set by the external voltage bV and the thickness h of SiO2 spacer, thereby controlling the chemical potential and surface conductivity of graphene. The dispersion relation of SPP modes in graphene can be derived from Maxwell's equations48In this equation, k0 = 2π/λ is the free-space wave vector of light and λ is the operating wavelength in vacuum. In the mid-infrared region, the dielectric permittivities of SiO2 and air are assumed to be dε = 3.9 and cε = 1.0, respectivelyeffn of the SPP mode, which is extremely sensitive to h and bV. Generally, the effective refractive index decreases with increasing bV due to the enlarged electric field. Thus, a larger h gives rise to a larger effective refractive index because the electric field on the graphene is smaller with a fixed voltage. In the mid-infrared region, the surface conductivity of graphene can be simplified into the Drude-like form27effn) is proportional to the square root of h, while inversely proportional to the square root of bV. The analysis is also verified by the calculation results  nearby the graphene.Here, ults see . It shouible see . Thus, t2. The Si substrate has a groove grating with period p, width w and depth d. The thickness of SiO2 spacer (the distance between the graphene and Si substrate) is t. Here, the groove depth d is constant. In general, a Bragg grating is a periodic modulation of the refractive index of the propagation medium, which is designed to selectively reflect a specific wavelength of light and transmit the others. One common way to achieve this is by stacking two materials with different refractive indiceseffn as described in the previous section.According to the Bragg scattering condition, the wavelength at which SPP modes in graphene are reflected by the grating can be derived fromeffn,1 and effn,2 represent the effective refractive indices of the SPP mode in the graphene with the two different areas above the silicon grating: effn,1,where the separation between graphene and Si is low and effn,2, where it is high  with increasing grating groove depth d. bV. Here, the blue-shift is caused by the change of Re(effn), which decreases with increasing the applied voltage bV. From k0 increases with the decrease of Re(effn).Here high see . m equalgv of light propagating in a mediumd. The group velocity is obtained from the slope of the tangent of a dispersion curve at a given point c/gv) of the graphene Bragg structure as a function of frequency (or wavelength). It demonstrates that a light signal in the graphene layer propagates at velocities more than 450 times slower than the speed of light as its frequency approaches the cutoff frequency. The slowdown factor is limited by ohmic losses in graphene and can be further improved by changing the physical factors such as carrier mobilities in graphene . To broaden the spectral region within which light signal can be slowed down efficiently, a graded grating structure  is introduced as illustrated in d is chosen to gradually increase from 100 nm to 400 nm along the x-axis, while pitch (p = 40 nm), width (w = 20 nm) and SiO2 thickness (t = 100 nm) remain constant. In order for the light trapping effect to occur, the grade gradient must satisfy the adiabaticity condition, which can in our case be expressed as δ = ∂k−1/∂x ≪ 1δ < 0.013 at the wavelength of 10 μm  distribution in the x-y plane of the structure for incident wavelengths of 8.0, 8.5 and 9.0 μm. The wavelengths are chosen to be located between the previously calculated cutoff frequencies for the minimum and maximum groove depths in the structure of d = 100 and 400 nm. x-axis, which is in excellent agreement with the results shown in λ = 7.65 to λ = 9.73 μm) feasible. The bandwidth corresponding to ~8.5 THz is improved by a factor of 4 when comparing with the results in Ref. gv can potentially be slowed down ever further and eventually approach zero.bV. Moreover, a stepwise increase of gate voltage will move the location at which a given wave is trapped continuously along the direction of propagation, as illustrated in the inset of bV = 85 V) is plotted in the inset of Another desired feature of a light tapping structure is the ability to release trapped waves in a controlled manner. It has been demonstrated that trapped waves in metal-based plasmonic waveguides can be released by introducing thermo-optic materialsIn this report, a novel structure consisting of a graphene monolayer and a graded silicon grating, which is separated from the graphene by a silica spacer layer, has been proposed. It has been demonstrated that the graphene-based plasmonic structure is capable of slowing down the group velocity of mid-infrared light propagating in graphene by a factor of more than 450. Numerical simulations as well as theoretical calculations reveal that both the grating groove depth and the applied gate voltage can be employed to efficiently tune the effective refractive index of the graphene monolayer. This allows for an exceptional tunability of the system's slowdown, light trapping and light release characteristics. By using a graded grating, incident light of a given wavelength can be trapped at a specific position in the graphene structure. Thus, optical input signals with different wavelengths can be separated spatially and trapped at specific positions in the graphene monolayer. The operating spectral bandwidth of this effect is ~2.1 μm in our structure and the trapping occurs on a length scale of one micrometer only, which is less than 1/6 of the wavelength of the propagating light. In particular, increasing the applied gate voltage allows for a controlled and systematic release of the trapped light at room temperature.The unique optical features of the graphene-based plasmonic structure combined with its simple tunability may pave the way towards the realization of nanoscale optoelectronic devices, in particular on-chip optical buffers and switches for signal processing and communications.The proposed graphene based structures are simulated using the finite-element method (FEM) software package COMSOL Multiphysics. In simulations, the graphene monolayer is represented by an ultrathin layer with a thickness of Δ = 1 nm2727It should be noted that Δ is not the actual thickness of a graphene monolayer (~0.33 nm). It is found that deviations between results obtained for Δ = 1 nm and Δ = 0.33 nm could be negligible if the simulation mesh is chosen to be sufficiently fine1920212338To theoretically calculate the dispersion relation of the graphene-based grating structure, we employ the following characteristic equationK is the Bloch wave number of SPPs in the direction along x axis. φ1 = k0neff,1(p-w) and φ2 = k0neff,2w represent the plasmonic phases of the graphene zones with SiO2 thickness of t (non-groove parts) and t + d (groove parts), respectively.Here, H.L. conceived the idea, carried out the numerical simulation and wrote the manuscript text. C.Z., Z.Q.M., X.M.L., H.M.M., R.P. and M.G. discussed the design of the proposed structure and simulation results, as well as improved the manuscript presentation. All authors discussed the results and substantially contributed to the manuscript.Supplementary Information


An optical device configuration allowing efficient electrical tuning of surface plasmon wavelength and absorption in a suspended/conformal graphene film is reported. An underlying 2-dimensional array of inverted rectangular pyramids greatly enhances optical coupling to the graphene film. In contrast to devices utilising 1D grating or Kretchman prism coupling configurations, both s and p polarization can excite plasmons due to symmetry of the grating structure. Additionally, the excited high frequency plasmon mode has a wavelength independent of incident photon angle allowing multidirectional coupling. By combining analytical methods with Rigorous Coupled-Wave Analysis, absorption of plasmons is mapped over near infrared spectral range as a function of chemical potential. Strong control over both plasmon wavelength and strength is provided by an ionic gel gate configuration. 0.04eV change in chemical potential increases plasmon energy by 0.05 eV shifting plasmon wavelength towards the visible, and providing enhancement in plasmon absorption. Most importantly, plasmon excitation can be dynamically switched off by lowering the chemical potential and moving from the intra-band to the inter-band transition region. Ability to electrically tune plasmon properties can be utilized in applications such as on-chip light modulation, photonic logic gates, optical interconnect and sensing applications. Graphene is a flat monolayer of carbon atoms tightly packed in a two-dimensional honeycomb lattice. Although graphene was only recently discovered it has attracted a lot of attention as it combines remarkable electronic, photonic and mechanical properties1234578Several methods have been implemented in order to couple and dynamically control plasmons in graphene. 1D trench based silicon diffraction gratings have been used as a wave vector/phase matching component between incident photons and plasmons in graphene. This provides control over the plasmon frequency by altering the grating lattice constant or by applying a voltage which alters the chemical potential in graphene10111214151616171921Obtaining strong coupling and highly tunable plasmons in graphene up to near infrared and visible frequencies is a difficult but highly anticipated task. In this work an inverted pyramid array diffraction grating with an ionic gel25Theoretical calculations as well as Rigorous coupled-wave-analysis simulations were undertaken demonstrating excitation of a plasmon mode, with excellent control of plasmon energy up to near infrared spectral range, using realistic chemical potential values for graphene. A plasmon energy shift from 0.65 eV to 0.84 eV when changing the chemical potential of graphene from 0.45 eV to 0.6 eV was achieved.We find that the structure supports a high frequency odd vector parity mode originating from the multi-interface nature of the device. This supports higher plasmon frequencies than typical single interface modes. Optimization of geometrical parameters such as pyramid size and pitch length were undertaken in order to achieve high coupling efficiency and demonstrate the scalable nature of the device. Unlike graphene micro and nanostructures, that can only support bound localized plasmon excitations12131415161710In practice n-doping of the graphene layer in combination with careful choice of the electrochemical window of ionic liquids used in the ionic gel can provide chemical potentials above 0.6 eV. Thus operation of the device can be extended for larger plasmon energies allowing plasmon excitations in the visible region of the spectrum.z orbitals of the neighboring carbon atoms overlap, forming bonding and antibonding states and thus the π-bands of graphene5* states form the conduction band5Carbon atoms have a total of six electrons out of which only four valence electrons can participate in bonds. The remaining two core electrons are strongly bound to the nucleus. In graphene carbon atoms are arranged in a honeycomb lattice formed by the spThe position of the chemical potential can easily be shifted above or below the Dirac point,  by applying a voltage. The carrier concentration in Graphene in relation with the applied voltage can be calculated as follows27Vg is the applied voltage, ε0 and εr the permittivity of vacuum and the relative permittivity of the substrate respectively, eq the electron charge, and d the substrate thickness. Having obtained the carrier concentration of the system the Chemical potential can be calculated aswhere vf Fermi velocity. To observe the change in optical behavior of graphene, conductivity is calculated as a function of wavelength taking into account the intraband and interband transitions. Chemical potential is obtained by use of the Kubo formulawhere ћ is the reduced Planck constant and, T the temperature, t the hopping parameter, and ω the angular frequency. By including a cubic term in the density of states this equation goes beyond the Dirac-cone approximation thus providing highly accurate results for high photon energies. Even though the response of the permittivity is essentially determined by valence and conduction electrons, the highly polarized environment originating from core electrons shouldn’t be ignored. The dielectric function including the contribution of the core electrons (background permittivity) can be expressed:wheredg graphene’s thickness (taken as 0.34 nm).where real) and 2.b (imaginary) parts at a temperature T of 300 K and a hoping parameter t of 2.7 eV for photon energies between 0.4 eV and 3 eV and chemical potential It should be mentioned that for wavelengths shorter than 410 nm (3.02 eV) an exciton-dominated peak with a maximum at 270 nm (4.6 eV) begins to appear35imaginary permittivity is positive, corresponding to energy loss for photons propagating through the material. This loss is due to absorption of photons by valence electrons participating in vertical interband transitions. In the same spectral region real permittivity has a stable value of 5.5 due to the polarization originating from the core electrons as seen in real and imaginary permittivity at the limit where photon energy equals twice the chemical potential in graphene  between the interfaces is smaller than the decay length The electrostatically controlled plasmon wave vector dispersion in graphene can be obtained by calculating the relation between the plasmon wave-vector and frequency. In multilayer systems of alternating dielectric/conducting materials each individual interface with a conducting layer can support Transverse Magnetic (TM) modes of bound surface plasmon polaritons37spersion . Taking where y of air . Since dx(z) component of electric field is odd, Hy(z) component of magnetic field and Ez(z) component of electric field are even functions) and x(z) is even, Hy(z) and Ez(z) are odd functions)sp) being greater than that of incident photons (ћk0) for the same frequency. Because of the mismatch in wave-vector, surface plasmons cannot normally be generated and thus phase matching is required. In this device, phase change is achieved by the introduction of a 2-dimensional grating below the graphene in the form of an inverted pyramid array. A simple one-dimensional groove approximation  features in the graphene dispersion and grating phase match conditions arising from the simple analytical analysis  is a highly efficient semi-analytical method for simulating electromagnetic behaviour of periodic structures. Electromagnetic fields and device geometries are represented by a sum of harmonic functions in Fourier space, and fields are solved in the form of a transmission line problem. RCWA simulations are particularly useful for graphene devices because (in contrast to FDTD or FEM methods) they don’t require solution of Maxwell’s equations over dense grids. Instead, structure is divided into uniform layers in the z direction and electromagnetic modes calculated by applying a layer by layer analytical solution which goes far beyond the simplified 3 layer system described in the previous section.In this section, relationship between geometrical parameters associated with the underlying inverted pyramid array diffraction grating  transfer process. Graphene is safely modelled as a 0.34 nm thick layer  with permittivity given by An absorption peak is observed away from the interband transition region and at the location of the phase match frequency appearing as a sharp (white) line. As graphene chemical potential increases, the real part of permittivity becomes increasingly negative due to higher quantity of free carriers. Thus a blue-shift in plasmon excitation frequency is observed (dispersion line moves to larger energy), thereby confirming electrically tuneable plasmon absorption.Looking more closely at the superimposed lines for the analytical model, for the single interface mode (cyan line) it predicts plasmon excitations at lower frequencies compared to RCWA method, whereas they are in excellent agreement to RCWA solutions for odd vector parity mode (black line). This provides proof that the excited mode is indeed a high frequency odd mode, and that the analytical model is actually very accurate. The higher plasmon frequencies supported by this mode when compared to plasmon excitations in single interface systems makes it ideal for scaling plasmons in graphene towards shorter wavelengths. In both cases strong modulation of plasmon excitation energy can be clearly observed with 0.04 eV shift in chemical potential resulting in ~0.05 eV shift in plasmon energy. Intensity of the absorption peak heavily depends on optical loss in graphene, mainly characterized by the imaginary part of permittivity, with higher losses corresponding to broader and lower peaksThe underlying 2D grating geometry can be scaled to shift the coupled graphene Plasmon frequency to match a broad range of incoming wavelengths and incidence angles, and also improve coupling efficiency. Plasmon absorption strength depends heavily on diffraction efficiency of the underlying grating structure used for phase matching. Improved diffraction efficiency increases coupling between incident light and graphene plasmons, resulting in higher intensity plasmon absorption peaks.Diffraction efficiency is related to density and size of diffractive structures. Optimization of size and spacing between inverted pyramids results in significantly improved diffraction efficiency. Effect of pyramid width (w) is investigated in frequency) is found to be unaffected by pyramid size.Plasmon absorption becomes stronger with increasing pyramid width, until the pyramid becomes approximately ¾ the size of the pitch where it begins decreasing again. Investigating this further, Diffracted photon k-vector is related to grating pitch (α) and so provides control of phase match frequency between incident photons and graphene plasmons. This is investigated in The analytical calculations are found to be highly accurate agreeing with RCWA simulations within 0.001 eV (1 nm).Virtually no shift in excitation energy is observed as a function of incidence angle  for a 10Phase matching can only occur for surface plasmon polaritons propagating perpendicular to the diffraction features when incident photons are polarized in the same direction10Finally it is interesting to see what happens when the aspect ratio of the system changes and how this affects plasmon excitations for different incident photon polarizations. Increasing the width (w) of only one side of the pyramid (moving from square to rectangular structures) breaks the symmetry, thus an increase of coupling efficiency for the polarization satisfying excitations perpendicular to the direction of the extended feature is expected. At the same time a decrease of efficiency is expected for the other polarization. This can be observed in 2 V−1 s−1 has been demonstrated (by employing current induced heating in order to reduce impurities), these high mobility values are limited over a small range of carrier concentrations2 V−1 s−1 at low temperatures and above 50.000 cm2 V−1 s−1 at room temperature) but once again for larger carrier concentrations the scattering loss increases2 V−1 s−1 and 1200 cm2 V−1 s−1 for unsuspended graphene layers172644It has been reported that dissipative losses in graphene in the TerahertzEven though this study is a purely theoretical approach, it is important to investigate how the device performs when including experimentally obtained mobility values in the calculations. In this case simplified equations for the conductivity of graphene are used instead of 46g is demonstrated in where the mobility is included through the phenomenological scattering rate By including the permittivity values for different mobility rates when modeling the graphene layer for the RCWA simulations the effect of dissipative loss can be observed in the absorption spectra as seen in In conclusion the reported optical device configuration shows strong electrical modulation of surface plasmon energy and absorption intensity. The underlying 2-dimensional array of inverted pyramids is highly efficient for coupling photons to the graphene film supporting excitation of plasmons equally for both s and p polarizations due to the structure symmetry. By optimizing the diffraction efficiency of the underlying structure significant increase in plasmon absorption intensity was observed. The device provides highly efficient dynamic modulation of the plasmon energy operating over a very large spectral range and up to the near infrared for currently easily achievable graphene chemical potentials. Assuming higher chemical potentials operation of the device can be extended to the visible spectrum as is. Furthermore, plasmon excitation can be effectively shut down by lowering the chemical potential providing dynamic means of photonic switching which can be exploited for high density optical interconnects. Plasmon absorption was also found to be highly unaffected by angle of incidence thus providing the possibility of exciting plasmons on the monolayer with the use of high numerical aperture lenses. Finally an analytical model assuming a multilayer setup was presented with excellent agreement to the RCWA simulation results for the high frequency odd plasmon mode providing an easy way to estimate the operation and design of new devices. Over-all the device can be utilized in a large number of possible applications including sensors, photonic logic gates, optical interconnects and modulators.How to cite this article: Matthaiakakis, N. et al. Strong modulation of plasmons in Graphene with the use of an Inverted pyramid array diffraction grating. Sci. Rep. 6, 27550; doi: 10.1038/srep27550 (2016).


We report ZnO/glass surface acoustic wave (SAW) humidity sensors with high sensitivity and fast response using graphene oxide sensing layer. The frequency shift of the sensors is exponentially correlated to the humidity change, induced mainly by mass loading effect rather than the complex impedance change of the sensing layer. The SAW sensors show high sensitivity at a broad humidity range from 0.5%RH to 85%RH with < 1 sec rise time. The simple design and excellent stability of our GO-based SAW humidity sensors, complemented with full humidity range measurement, highlights their potential in a wide range of applications. However, the ever-fast progressing science and technology require humidity sensors with better sensitivity, wider sensing range, faster response, shorter recovery time, and lower cost than what is now commercially available914etc in humidity sensors has resulted in many exciting progresses over the recent years. However, the development of novel sensitive materials and high performance humidity sensors, especially for applications requiring fast, low humidity level detection deserve more investigation and research.Measurement and control of environment humidity are of great importance in industrial processes, agricultural productions, and research experiments12256Functionalized graphene exhibits unique properties in chemical and biological sensing161718194etc27et alet al reported a SAW humidity sensor based on electrospun polyaniline/poly nanofibers sensitive layer with a sensitivity of ~75 kHz/%RH from 20 to 90%RHet al investigated SAW humidity sensors with silver nanoparticles as the sensing layer and obtained a sensitivity of over 10.6 kHz/%RHet al demonstrated humidity sensing characteristics of SAW sensors with atomizing GO sensitive layer with a sensitivity of 1.54 kHz/%RHet al and Ciplys et al investigated the mechanisms of SAW sensors with a graphene layer, and pointed out that the mass loading and viscoelastic effects are responsible for the increased attenuation observed19Surface acoustic wave (SAW) devices are one of the building blocks for electronicsWe prepared GO nanoflakes from natural graphite crystals using methods reported elsewhereGO dispersions allow deposition on target substrates by various methods such as drop-, spin-, spray-, and dip-coating23−1 and 1350 cm−1 which are known as the G and D peaks, respectively. The G peak corresponds to the E2g phonon at the Brillouin zone center. In pristine graphene−1. The presence of double-bonds (C = C) in our GO sample causes the blue-shift of the G band−1. The D peak originates from the breathing modes of six-atom rings and requires a defect for its activation. For the case of GO, this primarily comes from lattice defective states . Also, for the case of defected graphene samples like GO, G peak broadening is commonly observed as a result of the activation of q≠0 phonons−1. The high ID/IG ratio (~1.1) indicates large defect density in our GO sample. Considering FWHM(G) and ID/IG in our sample, we use I(D)/I(G) = C′(λ)La2 to find the cluster size, La, with C′ = 0.55 nm−2a ~ 1.4 nm. 2, O-C-O and O-C = O bonds, respectively. These oxygen-related chemical bonds increase the hydrophilicity of the GO layers, thus enhancing the humidity sensitivity of the SAW devicesThe typical Raman spectrum of the GO layers is shown in −1 is attributed to the -OH groups in stretching vibrations. This peak implies the good hydrophilicity of the GO samples used for our humidity sensing. Other absorption peaks at 1725 cm−1 originates from the C-O stretching vibrations of carbonyl and carboxylic groups, at 1627 cm−1 from the C-H, at 1398 cm−1 from the C-OH, at 1240 cm−1 from the C-O-C and at 1112 cm−1 of C-O stretching. These are all consistent with the results of the XPS spectrum. The presence of such carboxyl and hydroxyl functional groups in GO enhances the water adsorption ability of the sensing layer for humidity sensing.λ = 2d sin(θ)) of about 9.0 Å, which is much larger than that of bulk graphite crystal XRD pattern of the GO layers used in our experiments is shown in 2 gas to pass through for sensing. The relative humidity in the box was controlled by changing the flow ratio of dry N2 to wet N2 into the box, while keeping the total flow rate at 500 sccm. All the experiments were conducted at 25 ± 2°C.λ = 12 and 20 μm and resonant frequencies at ~225 MHz and ~140 MHz, respectively, were fabricated. They were coated with various GO layers for the humidity sensing experiments. SAW sensors with wavelengths of rf~140 MHz in Group A, sample D8 with a GO thickness of 200–300 nm over the whole surface exhibits the most significant frequency shift, i.e. the highest sensitivity, followed by the sensors with thinner or smaller area GO layers. Similarly, for the devices with a frequency of rf~225 MHz, D10 with a thicker GO layer has a larger frequency shift than that of D9 with a thinner GO layer.Moisture can be easily absorbed by the GO layer as it is a hydrophilic material 41434442319Δf, induced by a loaded mass, Δm, can be expressed asrf is the resonant frequency, μ and ρ are the shear modulus and the density of the substrate, respectively, A is the sensing area. sΔρ = Δm/A) change of the adsorbed water on the surface at various humidity for sensors D5-D10, indicating that the surface mass density increases non-linearly with the linear increase in humidity. Since the mass increase is associated with the number of water molecules, it actually reflects the nonlinear increase of water molecules adsorbed when the humidity increases. The sensor with thicker GO layer has higher capability to adsorb more water molecules, hence larger frequency shift. Note that we normalize the surface mass per unit area to eliminate the GO coverage difference from sample to sample. The increased frequency shift, hence the sensitivity, is attributed to the improved hydrophilicity and surface area of the active GO layers used. Assuming the hydrophilicity for ZnO and GO is similar, the increased surface mass density can be considered as a result of the increased sensing area, that can be calculated with respect to that of sample D1 with clean surface  as an example. They can be described by the following relation, 0f is the initial resonant frequency, 0RH is the reference relative humidity, a and b are two coefficient constants. The relationship has excellent linearity (0.9763<R2<0.9774) for both the sensors. The sensitivity of a humidity sensor is defined asΔf and ΔRH are the frequency shift and humidity change, respectively. From Eq.(3), the humidity sensitivity of all the sensors can be calculated with the results summarized in rf~225 MHz are 70–90% higher than those of sensors D6-D9 with similar GO layers but different resonant frequency, rf~140, showing that the resonant frequency has a significant effect on sensitivity of the SAW sensors. The sensitivity of the sensors increases as the resonant frequency increases.The frequency responses to humidity are approximately exponential as shown in Δf and insertion loss vs. RH when the humidity is changed from 10%RH to 85%RH and back to the initial value, showing little hysteresis to the humidity change. The rf shifts down, while the insertion loss increases with humidity. Both the frequency and insertion loss show fast response when the humidity is changed in a stepwise fashion. This indicates that the residual moisture in GO layer is very limited, and is not detrimental to the accurate measurement of humidity, even when fast response is necessary.As the sensor with a GO thickness of 100–130 nm has high sensitivity and fast response, it has been investigated in detail. rf~140 and 225 MHz) are far away from the ionic and dipole relaxation frequency of water molecules. Therefore, the impedance (conductivity) change induced by water molecules at SAW resonant frequencies is expected to be negligible. A detailed discussion about the surface conductivity window is presented in In general, adsorption of moisture decreases the surface complex impedance. This, in turn, may change both the acoustic velocity and attenuation of a SAW device49shσ ~ 0.2 Ω−1), it will screen off any minor surface conductivity change of the GO layer induced by adsorbed water. Therefore, the structure of D12 can eliminate the effect caused by the surface conductivity variation, and a smaller frequency shift is expected for D12 than that of D5 if there is a water-induced conductivity change in the narrow window. To further determine whether the resonant frequency shift is caused by the conductivity change or not, we designed an experiment with samples D5 and D12  were further investigated  of GO may produce protons, which may induce additional mass and change the surface conductivity. However, the change in mass on the surface is very small owing to the chemical reaction, which has little mass exchange involved, and will not change the resonant frequency. The generation of free proton carriers may partially contribute to the total change of the surface conductivity of the sensors with GO layer, which has been proven to be not the major factor to affect the resonant frequency change as discussed above. Therefore we can conclude that the possible interaction of free carrier protons via reaction of GO with water would not affect the sensing results obtained in this work.The viscoelastic effect is another possible cause responsible for the frequency shift upon moisture absorption, and especially important for SAW humidity sensors with a polymer coating. It is difficult to separate its effect from the mass loading effect19In summary, ZnO on glass SAW humidity sensors with GO sensitive layers have been fabricated and characterized. The sensitivity of the SAW sensors is positively correlated with GO layer thickness, resonant frequency, and the covered surface area by the GO sensitive layer. The frequency shift of the sensors is exponentially sensitive to the humidity change, and is caused by mass loading effect. The sensors with an extended coverage of a drop-casting GO layer over IDTs area have the best performance, followed by those with a GO layer in between the IDTs and those with spin-coated GO layers. The SAW sensors show very fast response to humidity change with a rise time of less than 1 sec, and the total fall time of less than 19 sec. They also show good stability at various humidity levels for up to 60 days without much deterioration. Our results demonstrate SAW devices with GO sensing layer are suitable for applications in various fields such as health and environment humidity monitoring at room temperature.2 with 100 and 50 sccm flow rates were employed for the deposition with the substrate temperature and the deposition pressure at 200°C and 2 Pa, respectively. The bias voltage at target was 75 V and the deposition power was 175 W. The thickness of ZnO is ~3.0 ± 0.06 μm for all the devices used in this study. After deposition, the samples were annealed at 400°C for 10 min in N2 atmosphere  to reduce the stress and defects in the films. The samples were then characterized by X-ray diffraction , atomic force microscopy , and scanning electron microscopy  as previously reportedZnO piezoelectric films were deposited on the glass substrate by direct-current (DC) reactive magnetron sputtering. The optimized deposition conditions have been reported previouslyλ = 12 and 20 μm were fabricated to investigate the effect of resonant frequency on the sensing performance. The corresponding resonant frequencies, rf, are approximately 225 and 140 MHz, respectively. All the SAW devices have 50 pairs of IDT fingers and 10 pairs of reflecting gratings. The transmission spectrum (S21) and insertion loss of the sensors were investigated at various relative humidity (RH) using a network analyzer , which was controlled by a LabVIEW-based software through general purpose interface bus (GPIB).The SAW devices were fabricated on 500 μm thick Corning 2318 glass substrates with ZnO as the piezoelectric layer60Graphene oxide layers were characterized by Raman spectrocopy , X-ray photoelectron spectroscopy , X-ray diffraction , and Fourier transform infrared spectroscopy . The thickness and morphology of the GO layers were characterized by profilometer  and scanning electron microscopy .2 gas with various humidity levels to pass through and two SMA (SubMiniature version A) interfaces for transmission measurements. The relative humidity in the box was controlled by changing the flow ratio of dry N2 to wet N2 into the box, while keeping the total flow rate at 500 sccm. A commercial hygrothermograph (TASI-621 TASI, based on SHT71GO material was prepared and deposited on the surface of the SAW devices more than a month before sensing experiments. The SAW sensors were placed in a hermetic box with two through-holes for NW.X., M.H. deposited ZnO and Al thin films, fabricated SAW devices; Z.X. provided the GO samples; W.X., N.M. conducted the characterization of the GO materials. W.X., X.H., W.W. and J.C. set up the humidity sensing experiment and assisted the sensing experiments. W.X. and T.S. measured all the sensors. Y.X., T.H. and J.K.L. supervised the project, analyzed the results and modified and revised the paper. All authors contributed to the discussions.Supplementary Information


Retroelement activity is a common source of polymorphisms in human genome. The mechanism whereby retroelements contribute to the intraindividual genetic heterogeneity by inserting into the DNA of somatic cells is gaining increasing attention. Brain tissues are suspected to accumulate genetic heterogeneity as a result of the retroelements somatic activity. This study aims to expand our understanding of the role retroelements play in generating somatic mosaicism of neural tissues. Whole-genome Alu and L1 profiling of genomic DNA extracted from the cerebellum, frontal cortex, subventricular zone, dentate gyrus, and the myocardium revealed hundreds of somatic insertions in each of the analyzed tissues. Interestingly, the highest concentration of such insertions was detected in the dentate gyrus—the hotspot of adult neurogenesis. Insertions of retroelements and their activity could produce genetically diverse neuronal subsets, which can be involved in hippocampal-dependent learning and memory. Approximately 40% of the human genome is comprised of multiple copies of retroelements (REs) due to their winning streak in the course of mammalian evolution . The majIt has been long considered that the majority of retrotranspositions occur in the germ line, while the mobility of REs in somatic cells is strictly suppressed. Mammalian cells possess multiple mechanisms of inhibiting REs expression, including siRNA , miRNA , piRNA-iHere we applied a high-throughput approach to directly compare the number of autonomous (L1) and non-autonomous (Alu) retroelement somatic insertions in various human adult brain regions and a control non-nervous tissue. Whole-genome Alu and L1 profiling was performed for four brain regions including the dentate gyrus, the only region of the adult human brain that was shown to retain significant neurogenic capacity.in vitro and in vivo in the mouse dentate gyrus [Previously, activation of L1 retrotranspositions was associated with a switch from neural stem cells to fast proliferating neural progenitor cells te gyrus , 28. Thete gyrus . In the te gyrus , 31, whete gyrus –35. To aFor library preparation, we modified the suppression PCR-based method of retrieving REs terminal and flanking sequences from genomic DNA , 37. BriA total of 10,709,681 and 61,213,133 high-quality reads were obtained for L1 and Alu libraries, respectively. The detailed information on the number of reads and somatic insertions detected in each library is shown in A total of 7,497 potentially somatic L1 and 8,990 potentially somatic Alu insertions were identified in the tissue libraries . All theA total of 3,798 somatic L1 and 4,314 somatic Alu elements from all libraries integrated into genes (overwhelmingly into introns). Another portion of somatic insertions (436 L1 and 393 Alu) was detected within 5,000 bp upstream of the gene transcription start sites . In ordeInterestingly, across all samples analyzed, the distribution of somatic L1 or Alu insertions was very similar, namely, the percentages of somatic L1 or Alu that integrated into the genes or 5 kb region upstream genes were 50–51% and 5.5–6.5% for L1 or 47–49% and 3.5–5% for Alu, respectively . The samFinally, we analyzed the orientation of somatic retroelement insertions relative to genes (for those retroelements that integrated into introns or 5 kb regions upstream genes). Strikingly, intronic L1 elements preferentially integrated in the opposite orientation relative to the gene  −40.96 ±Nested PCR and Sanger sequencing of the PCR products were carried out to validate the potentially somatic insertions. We selected 34 L1 and 26 Alu elements integration events for validation . We confIn this study we for the first time showed an increased number of L1 somatic retrotranspositions in the dentate gyrus of the human brain in comparison to other brain regions and the myocardium by directly sequencing and mapping the somatic insertions. Several recent studies proposed that activation of L1 retroelements coincides with neuronal differentiation , 23, 28.Notably, we did not find any increase in the retrotranspositions in another putative neurogenic zone of the adult mammalian brain, the SVZ. However, several recent studies indicated that in humans, unlike rodents, the neurogenesis in the adult SVZ is negligible , 35. RobInterestingly, we showed that the number of somatic L1 retrotranspositions in promoters and genes is higher than expected for all brain samples and the myocardium. This observation is different from the data obtained by Ewing and Kazazian  where auThe orientation of genic L1 insertions was observed to be biased towards counter-orientated state in all brain regions and myocardium. This can be caused by a higher negative effect of co-oriented insertions on gene expression (e.g. knock-down of gene expression) and is similar to the results obtained by Ewing and Kazazian . Howevercis-preference to the self RNA [Similar to the somatic L1 insertions, the Alu insertions demonstrated the most persistent expansion in the dentate gyrus. However, the rates of Alu propagation in the rest of the samples was not as equal as for the L1. The percentage of somatic Alu elements was variable and significantly different between the regions analyzed. This can probably be explained by the differences between the mechanisms of Alu and L1 suppression , 39 or bself RNA .Interestingly, the number of somatic Alu integration events in genes and promoters was similar to the expected values for all regions analyzed, but the DG. Furthermore, in the DG while Alu integrated preferably in the genes, they avoided integrating in the promoter regions, which is opposite to L1. Moreover, DG was the only brain region in which the orientation bias of the somatic Alu insertions was observed. Altogether these facts suggest that cells of the DG carrying new Alu insertions are subject to selection.The data on both L1 and Alu somatic insertions obtained in the current work indicate an increased retrotranspositional activity in the DG. Since our results are based on the analysis of a single donor we cannot exclude the possibility that the observed pattern of the somatic insertion distribution in brain tissues is unique and can vary in other members of the population. However, our results match the data obtained by qPCR  indicatiWe have not observed any insertions which were represented by many sequencing reads on the one hand and could be considered somatic on the other. This indicates that the retroelement hops in the genome occur mainly in adult tissues or at the stage of late development, but not during embryogenesis. This corresponds to the results of Baillie and colleagues  who haveOur results are consistent with the studies that were performed in mice. Although L1 can retrotranspose in many regions of the mouse brain , an injeA three room standard was applied for sample preparation: all procedures with genomic DNA were performed in room 1; PCR preparation was performed in room 2; electrophoresis and other post-PCR activities were performed in room 3.Primers for validating potential somatic insertions lied out of the sequences which comprised the resulting Illumina libraries in order to avoid the amplification of the contaminating molecules from these libraries.Tissue samples were taken within 12 hours after death from a 72 year old male individual. Tissue samples were frozen in liquid nitrogen immediately after sectioning and then stored at -80°C. The study was approved by the local ethics committee of the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences and conducted in accordance with the Declaration of Helsinki. As no consent could be obtained from the donor, the written consent was provided by the next of the kin. Genomic DNA was extracted from five frozen tissue samples of a single individual: cerebellum, frontal cortex, subventricular zone, dentate gyrus and myocardium, using the standard phenol-chloroform extraction method.The library construction protocol included the step of genomic DNA digestion by restriction enzymes , adapter ligation and two steps of suppression PCR selectively amplifying the insertion sites of the most active RE subfamilies (L1Hs and AluYa5). Sequences of the oligonucleotides used for library preparation are shown in Data analysis included the use of standard tools: Bowtie2 , 47 and The coordinates of the potential somatic insertions were intersected with the coordinates of the known genes and genes promoter regions  present in hg19 by the Galaxy tool “Join”. Statistical analysis was done using R software  includinThe analysis of Alu and L1 distributions in different brain areas and of the genomic distribution of the somatic L1 and Alu insertions was performed using an overdispersion test. The distribution of Alu and L1 in the dentate gyrus was compared with the distribution in all other samples combined using the Poisson test. Binomial tests were applied for the analysis of somatic L1 and Alu orientation relative to nearby genes. Monte Carlo simulations of random retroelement distributions throughout the genome were performed to analyze the randomness of the Alu and L1 distributions in promoters and genes.Nested PCR was performed for the validation of the selected somatic retroelement insertions. PCR products were Sanger sequenced. Primer structures and sequences are given in Nested PCR was performed to amplify the RE insertion flanking sequences from gDNA. Primer structures are given in S1 Materials and MethodsFor more details see The European Nucleotide Archive accession number for the Illumina sequences reported in this paper is PRJEB4787.S1 Table(XLSX)Click here for additional data file.S2 Table(PDF)Click here for additional data file.S1 Materials and Methods(PDF)Click here for additional data file.


The core niche for language use is in verbal interaction, involving the rapid exchange of turns at talking. This paper reviews the extensive literature about this system, adding new statistical analyses of behavioral data where they have been missing, demonstrating that turn-taking has the systematic properties originally noted by  One of the most distinctive ethological properties of humans is that they spend considerable hours in the day in a close (often face-to-face) position with others, exchanging short bursts of sound in a human-specific communication pattern: extrapolating from This core form of language use poses a central puzzle for psycholinguistics (see Section 6), which has largely ignored this context, instead examining details of the processes of language production or comprehension separately in laboratory contexts. Yet this prime use of language involves rapid switching between comprehension and production at a rate implying that these processes must sometimes overlap. Decades of experimentation have shown that the language production system has latencies of around 600 ms and up for encoding a new word (reviewed in Section 6.3) but the gaps between turns average around 200 ms (see Section 5). This would seem to imply that participants planning to respond are already encoding their responses while the incoming turn from the other speaker is still unfinished. This in turn implies potentially long-range prediction in comprehension. A sketch model of the interleaving of comprehension and production processes is presented in Section 7.To appreciate the full nature of this puzzle, it is essential to review what we know about the turn-taking system and its temporal properties. In Section 2, we review the foundational (1)If the current speaker C selects the next speaker N, then C must stop, and N should start. (2)If C does not select N, than any participant can self-select, first starter gaining rights to that next unit.(3)If no other party self-selects, C may continue.These rules then recursively apply at each TRP.These rules predict that intra-speaker silent gaps (generated by rule 3) will be longer than inter-speaker ones, a fact shown to be correct on large samples of conversation  so that the bulk of overlaps are of short duration. ‘Interruption’ is a sanctionable breach of social mores, as every child learns. The systematic properties of all the corpora that have been studied would be entirely different if overlap was not avoided.On the basis of their dismissal of the no-gap–no-overlap target, The central plank of the dismissal of projection is that turn-taking is often not as rapid as has been claimed. “The cumulative distribution above the 200 ms threshold was also of interest, as it represented the cases where reaction to cessation of speech might be relevant given published minimal reaction times for spoken utterances . The disThere are two separate proposals here. The first is that for gaps longer than 200 ms, participants might simply react to silence. This threshold is implausible. First, silence will only become recognizable as silence after c. 200 ms . Note that although mean values vary, they do so in narrow window, roughly a quarter of a second either side of the cross-linguistic mean, and that the factors affecting response times are uniform across cultures  questions cross-linguistically In running speech, how common is overlap  compared to talk by one party alone?(2)In floor transfers, how common are overlaps compared to gaps?(3)What is the distribution of overlap duration, and where do overlaps tend to start relative to the interlocutor’s turn?(4)What is the distribution of different overlap types cf. ?gaps, pauses, between-overlaps, and within-overlaps as follows. Gaps (n = 14648) corresponded to portions of the stereo signal that contained silence in each speaker’s channel, and that involved a floor transfer between the two speakers. Between-overlaps (n = 6524) were floor transfers that occurred without a silent gap between the speakers, whereas within-overlaps (n = 3343) were parts of the signal with overlapping inter-pausal units that did not result in an effective floor transfer. Figure 1 below illustrates the operationalization of gaps, between-overlaps and within-overlaps.We analyzed a subset of 348 conversations  that were free of timing errors, and with annotations included in the NXT-Switchboard Corpus release . To estiThe recordings were divided as follows: 77% of the signal corresponded to speech by one speaker only, 19.2% to silence , and only 3.8% to simultaneous speech by both speakers (either between-overlaps or within-overlaps). If we exclude silent parts, 95.3% of the speech signal corresponded to speech by one speaker. This seems to fit well with Sacks and colleagues’ observation that “overwhelmingly, one party speaks at a time” , p. 700.Figure 2 shows the distribution of the duration of gaps and between-overlaps combined together as FTOs . Between-overlaps (negative FTOs) represented 30.1% of all floor transfers. As for the duration of overlaps, and their location within the interlocutor’s turn, we observed that between-overlaps exhibited a distribution highly skewed to the left, with an estimated modal duration of 96 ms, a median of 205 ms, a mean of 275 ms, and with 75% of the data with values below 374 ms. Within-overlaps tended to start close to the beginning of the utterances that they overlapped, with a modal offset of 350 ms, a median of 389 ms, a mean of 447 ms, and 75% of the data exhibiting offsets below 532 ms. Their duration exhibited a distribution highly skewed to the right, with an estimated modal duration of 350 ms, a median of 389 ms, a mean of 447 ms, and 75% of the data with values below 532 ms. The duration of within-overlaps is thus usually shorter than that of two syllables. This appears to fit well with With regard to how common overlaps are in terms of proportion of turn-transitions, yeah, right) and other minimal utterances that do not constitute an attempt to take the floor. The We now examine the distribution of different types of overlaps. A prediction made by the yeah, right) in either the overlapped or overlapping utterance, (b) the presence of a period of silence within 200 ms from the beginning of the overlap period, (c) the presence of a transition relevance place  in the overlapped turn within the 500 ms leading to the overlap, (d) an abandoned  utterance by any of the two speakers during or immediately following the overlap interval, and (e) the presence of repeated syllables or words in any of the two speaker’s utterances during or immediately following the overlap interval. Other recurrent features observed during or close to the overlap interval, such as laughter and disfluencies, were also annotated.To estimate the prevalence of such possible causal contexts for overlap, in a separate analysis we randomly sampled 100 between-overlaps and 100 within-overlaps from our data, and annotated them for a number of relevant features, including (a) the presence of a backchannel or brief token of agreement . Interestingly, the majority of overlap cases (73%) involved a backchannel. Backchannels, especially continuers like “mm hm” or “uh huh,” are not construed as full turns, but rather pass up the opportunity to take a turn, and are thus principled intrusions into the other’s speech , or resulted in one of the two speakers abandoning their turn prematurely before reaching a point syntactic and prosodic completion . The presence of a disfluency in the utterance of the overlapped speaker before the start of the overlap  was also common. In these cases, it seems that the recipient produced a backchannel in response to the disfluency at a point when the interlocutor had already resumed her turn, causing overlap. In total, cases exhibiting one or more of these six features accounted for 95% of the data.The second most common feature (37%) was the presence of a possible transition-relevance place  in the overlapped turn within a time window of 500 ms before the start of the overlap. Another common feature was a period of silence (29%). In cases with this feature, one of the two speakers produced an utterance briefly after her interlocutor. These cases often involved a backchannel (uhm and well) produced in overlap with the last syllable of the preceding turn, one case with a speaker talking to someone else in the room, and one case of overlap due a clear phonetic segmentation error in the annotation.The remaining 10 cases involved three terminal between-overlaps affecting the last syllable of the previous turn, two cases exhibiting laughter by one of the speakers, two cases involving a turn-initial particle , are of short duration , occur largely in principled places , and mostly involve backchannels (which do not constitute full turns). In light of these observations, we conclude that the vast majority of instances of overlap in our dyadic conversations are consistent with the turn-taking system proposed by Psycholinguistic processing puts tight constraints on any psychologically real model of turn-taking. Here we first draw attention to the early sensitivity to turn-taking in child development. Then we consider three main psycholinguistic aspects: predictive theories of language comprehension, studies of language production , and ideas about the relation between these two processes. Finally we turn to a small number of experimental studies aimed at understanding the relationship between comprehension and production processes in turn-taking.increased toward a second and a half in toddlers, presumably because of the cognitive difficulties of language production, and remained at around a second even for 5-year-olds [this slow convergence with adult norms has recently been confirmed for a larger sample by Stivers et al. (under review)].Parallel to anticipate speaker transitions  have confirmed the general pattern earlier reported, namely relatively fast transitions in the prelinguistic period, with a slowing down as language starts to be comprehended at 9 months. Using eye-tracking of infants watching dyadic interaction, several studies have shown that 3-year-olds observers of dyadic conversations between two adults can nsitions . Althougnsitions , showingnsitions . Casillaun vs. une), Adjectives (“freshly baked”) and verbs (“eat”) can predict nouns by their selectional restrictions; in language that have verbs at the end of the sentence like Japanese, participants can use the nouns to predict the verbs . These studies use the inverse correlation between the cloze probability and the amplitude of an N400 to demonstrate prediction , it takes about 1500 ms before speech output begins . InteresDuring this period of planning for language production, output processes involve the synergies between multiple speech organs. For example, breathing for speaking may need to be initiated. Earlier studies have shown that such breathing activity involves a number of latencies: first, c. 140–320 ms must be allowed for from the time the decision to inhale is made till the time the signal reaches the intercostal muscles ; second,2(n) and n is the number of equally probable choices). When one considers that in production single words have to be plucked from a word lexicon consisting of over 20,000 entries, one can see immediately the processing problems involved. Combined with the relatively slow nature of nerve conduction Which character from the famous movies, is also called 007? (Late).In a second experiment, participants heard the same questions but did not have to answer them. Instead, they only had to remember them, as prompted by later probes. The neural patterns were then compared with those in the first experiment, where participants had to verbally respond, to the second where they only had to comprehend and memorize. The results revealed a clear neural signature associated with production, localized in the appropriate areas, occurring within 500 ms of the point at which a plausible answer to the question became available. Bögels and colleagues interpreted this as showing that participants begin planning their response as soon as they can, up to a second or more before the incoming turn ends.sine qua non for planning their appropriate response. In order to overcome the production latencies, they must also start the planning and encoding of the response as soon as possible.From a psycholinguistic point of view, turn-taking presents the following puzzle: in spite of the long latencies involved in language production (600–1500 ms or more), participants often manage to achieve smooth turn transitions . As a solution to this puzzle, we suggest that comprehension is predictive, even more so than is currently thought. As soon as possible, participants extract the speech act of the incoming utterance, which is the This suggests that there is a significant overlap of comprehension and production processes. Given an average turn  of 1680 ms, somewhere in the middle response preparation may already be underway. This provides a second central puzzle: conversation involves constant double tasking, and this double tasking uses the same language system. The difficulty of the puzzle is increased when one takes into account the findings that both comprehension and production use much of the same neural circuitry . It is pminus the phonological and phonetic encoding, which account for the bulk of the production latency.In any case, regardless of how this is achieved, the experimental and corpus studies reviewed in this section converge in showing that participants in conversation often anticipate the content of the others’ turns well in advance, and that they use that information to prepare their response early.Let us now gather together how the observations and inferences discussed above constrain viable models of turn-taking. Any adequate model must be consistent with a number of observations and constraints, as originally noted by (1)Turns are mostly short , consisting of one or more interjections, phrases or clauses at the syntactic level, and one or more intonational units at the prosodic level. Turn ends typically co-occur with points of both syntactic and prosodic completion.(2)Intra-speaker gaps are longer by c. 150 ms than inter-speaker gaps , suggest(3)Figure 2). Medium gaps and short overlaps are also common, although less so than short gaps.Inter-speaker gaps are most typically short, with modal values for FTOs falling between 100 and 200 ms (cf. (4)Lengthy gaps (over 700 ms) may carry semiotic significance Overlaps, though common, are brief . Overlaps are more common at turn transitions than within turns, and mostly involve back-channels, simultaneous first-starts, disfluencies, and other features predicted by (6)Turn-taking is established early in infancy, long before full linguistic competence, which actually appears to slow down response times; adult conversation timing is not achieved till late in middle childhood.(7)Given the latencies of speech production (over 600 ms), incoming turns have to be predicted if accurate timing is to be achieved. EEG recordings suggest the production process in responsive turns starts as soon as the gist of the incoming turn can be detected.(8)Turn-final cues seem to be used to recognize that a turn is definitely coming to an end. These cues are typically prosodic  but also syntactic , and in principle could be of other types too . In the appropriate pragmatic context, these turn-final cues can trigger the decision of the next speaker to articulate. From the point of view of social interaction, it is effective articulation that constitutes a point of no return .We have outlined above the (9)D: I forgot to tell you the two best things that happen’ to me today.R: Oh super=What were they?D: I got a B+ on my math test ) and I got an athletic award.An alternative model is the turn-end signaling system proposed by We believe that the property list in Section 7 above puts fairly narrow constraints on a possible model of turn-taking. One area of particular interest is the temporal constraints that turn-taking imposes on language processing, given that conversational interchange is the core form of language use. These constraints are funneled into one crucial link in the system, namely, the current addressee preparing to respond. Here we consider the cognitive processes that must be involved.The crucial questions concern what factors govern the decision making process that lies behind the initiation and timing of response. While turn-final cues in the incoming turn seem likely to play a role, they cannot be sufficient given the long latencies in language planning and production. To overcome these long latencies, predictive comprehension must be involved, together with a strategy of early beginnings to production. Bögels et al. (submitted) suggest that production begins as soon as it can – that is, as soon as the speech act content of the incoming turn is clear. This implies of course dual-tasking, perhaps by rapid alternation (‘time sharing’). A new study using a dual-task paradigm and eye-tracking suggests that the heaviest interference is rather late , and tieFigure 3 sketches the cognitive processes that must minimally be at work in the recipient of a typical turn at talk during conversation. Predictive comprehension is underway early, and already by half way through more predictable turns will suggest a temporal envelope for completion (if or either or whenever projects a two clause structure), so offering some long distance projection. Within the last half second or so, the actual words will often be predicted . Production is, at least in the latter stages, serial, and proceeds through conceptualization, lemma retrieval, phonological retrieval, and phonetic encoding, following a time course that seems well understood , extendiFigure 3 sketches the kind of interaction between comprehension and production processes that must be involved in a typical turn transition . There is an early gist comprehension with speech act apprehension sent as soon as possible to the production conceptualizer an account of how responders can often respond with short latencies despite the long latencies of the production system;(b)why the corpus statistical results reliably show a modal response with positive offsets of around 100–300 ms, reflecting the reaction time to the turn-final prosodic cues in the incoming turn , and it poses a substantial puzzle for psycholinguistic models , which until recently have completely ignored this, the most central form of language use.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Nitrogen-doped graphene decorated by iron-nickel alloy is introduced as a promising electrode material for supercapacitors. Compared to pristine and Ni-decorated graphene, in acid media, the introduced electrode revealed excellent specific capacitance as the corresponding specific capacitance was multiplied around ten times with capacity retention maintained at 94.9% for 1,000 cycles. Briefly, iron acetate, nickel acetate, urea, and graphene oxide were ultrasonicated and subjected to MW heating and then sintered with melanin in Ar. The introduced N-doped FeNi@Gr exhibits remarkable electrochemical behavior with long-term stability. Due to the intense shortage of reserves of fossil fuels, increasing the awareness of energy conservation and environmental preservation has internationally spurred unprecedented interest in developing green and renewable energy. Electrochemical capacitors (ECs), as one of the promising technology for energy storage systems, have attracted significant attention due to their high power performance, very long life cycle, and reasonable energy density. Accordingly, ECs are often favored in various applications including portable electronics, uninterruptible power sources, memory backup systems, and hybrid electric vehicles -3. It isAs for other energy devices such as fuel cells and dye-sensitized solar cells, the best performance in the electrochemical supercapacitors was achieved with precious metal-based electrodes which constraints the commercialization process ,6. Recenπ bonding [It is generally believed that pseudocapacitance in carbon-based materials is largely based on the redox reactions of surface quinoid functionalities, whose reduction requires protons to proceed . Neverth bonding ,25 and t bonding . The wor bonding .Besides, some transition metal-based materials containing manganese, silver, nickel, and iron revealed good electrochemical behavior -32. In tNitrogen-doped, FeNi alloy-doped graphene was synthesized by dissolving 250 mg of urea in 100 ml aqueous solution from iron(II) acetate (0.5 mM) and nickel(II) acetate tetrahydrate (0.5 mM); the solution was stirred for 2 h and ultrasonicated for 30 min. The obtained solution was mixed with 50 ml aqueous solution containing 200 mg of graphene oxide (GO) prepared by a modified Hummers method  using miλ = 1.54056 Å) radiation over a range of 2θ angles from 10° to 80° was utilized to get information about the phase and crystallinity. The surface morphology and elemental mapping were investigated by a JEOL JSM-5900 scanning electron microscope  and transmission electron microscope  operated at 200 kV equipped with energy-dispersive X-ray (EDX) analysis. Electrochemical analysis was carried out using a different three-electrode system: platinum wire as counter electrode, Ag/AgCl as reference electrode, and the fabricated materials as working electrode. The electrochemical impedance spectroscopy (EIS) was measured with a frequency range between 0.01 Hz and 100 kHz. This system was controlled using a VersaStat4 potentiostat device . The surface composition was detected by X-ray photoelectron spectroscopy (XPS) analysis  with the following conditions: base pressure 6.5 × 10−9 Torr, resolution (pass energy) 20 eV, and scan step 0.05 eV step−1.A Rigaku X-ray diffractometer  with Cu Kα , (200), and (220) crystal planes, respectively, indicate the formation of FeNi alloy [Figure Ni alloy . XPS speNi alloy . Figure 2SO4 as electrolyte solution. As shown in Figure −1. Figure −1. Obviously, the N-doped FeNi@Gr electrode shows redox peaks, indicating that the capacitance characteristics are mainly governed by faradaic redox reactions; thus, the curve pronounces pseudocapacitive behavior attributed to nature-doped materials with nitrogen-containing surface functional groups [−1. The specific capacitance could be determined from the following equation [For proper comparison, the electrochemical properties of the introduced N-doped FeNi@Gr electrode, pristine graphene, and N-doped Ni@graphene were investigated. Figure l groups . Noteworequation ,38:FigurCsp is the specific capacitance (F g−1), I is the response current (A), V is the potential (V), υ is the potential scan rate (V s−1), and m is the mass of the electroactive materials in the electrodes (g). As shown in Figure −1 is 254 F g−1 which is about tenfolds of the other formulations. As the introduced material is based on pristine metals and the electrochemical property investigations have been carried out in acidic media, cycling performance is important to check the corrosion resistance of the introduced alloy NPs. A long-term cycle stability test was evaluated for 1,000 cycles (Figure where Bimetallic N-doped FeNi@graphene can be prepared by multi-treatment of FeAc, NiAc, urea, and GO followed by calcination of the mixture with melanin in an argon atmosphere at 750°C. The FeNi alloy structure can distinctly enhance the electrochemical properties compared to the pristine metals. The synthesized alloy NPs have an average size of 15 nm and homogeneous distribution on the graphene sheets. The introduced electrode material provides a high specific capacitance with excellent cyclability in acidic media, so it can be recommended for commercial application.


Sarcoidosis is a granulomatous disease, the etiology of which is currently unknown. The role of mycobacteria in the etiology of sarcoidosis has been extensively investigated. In this meta-analysis, we assessed the immunological evidence of the possible role of mycobacteria in the pathogenesis and development of sarcoidosis.We performed a systematic search of relevant articles from PubMed, Embase and Cochrane Library databases published between January 1990 and October 2015. Data extracted from the articles were analyzed with Review Manager 5.3 .In this meta-analysis, 13 case-control studies (733 participants) were considered eligible according to our criteria. Methodological quality was assessed using the Newcastle-Ottawa Scale (NOS). The positivity incidence of the immune response  in sarcoidosis patients was significantly higher than that in controls, as determined using fixed-effects model. The odds ratio (OR) of the positivity incidence of T-cell response in the patients with sarcoidosis versus the controls with PPD- or unknown PPD status was 5.54 (95% CI 3.56–8.61); the ORs were 16.70 (95% CI 8.19–34.08) and 1.48 (95% CI 0.74–2.96) for the two subgroups with PPD- controls and unknown PPD status respectively. However, the OR of the positivity incidence in patients with sarcoidosis versus PPD+ controls  was 0.26 (95% 0.10–0.66). Regarding the humoral response, pooled analysis of the positivity incidence revealed an OR (95%CI) of 20.43 (5.53–75.53) for the patients with sarcoidosis versus controls; the ORs were 11.93 (95% CI 2.15–66.27) and 41.97 (95% CI 5.24–336.15) in two subgroups of controls with PPD- and unknown PPD statuses respectively. Data on heterogeneity and evidence of publication bias were examined.M.tuberculosis) and sarcoidosis. The current available evidence indicates that some insoluble mycobacterial antigens that preferentially within the body are involved in the pathogenesis of sarcoidosis rather than the whole mycobacteria and that they elicit a type IV immune response.This meta-analysis confirmed the existence of an association between mycobacteria (especially  M. tuberculosis) is the second most common infectious cause of death in adults worldwide (HIV is the most common). The human host serves as a natural reservoir for M. tuberculosis, which is an intracellular obligate and aerobic bacillus that multiplies within macrophages. The bacterium triggers the production of free radicals and avoids being killed by the same radicals [M. tuberculosis to efficiently establish latent infection has enabled it to spread to nearly one-third of individuals worldwide.Mycobacterium tuberculosis  have been suggested to be infectious factors for the pathogenesis of SA [Sarcoidosis is a systemic granulomatous disease characterized by the formation of epithelioid cell granulomas (and is accompanied by an infiltration of inflammatory cells) without caseous necrosis. Multisystem granulomatous inflammation involving the lungs, lymph nodes, skin, eyes, heart, and muscles is a hallmark of sarcoidosis. Infectious and genetic factors, as well as autoimmunity, are considered to be potential causes of SA –4. In adis of SA .M. tuberculosis was isolated from several sarcoidosis patients by Scadding [M. tuberculosis and sarcoidosis has since been explored with increasing frequency. The advent of molecular biology invigorated the search for mycobacterial DNA in sarcoidosis patients [In the middle of the 20th century, Scadding . The relpatients , 8. One patients  compiledM. tuberculosis antigens could be involved in the pathogenesis of sarcoidosis. Many studies on the T-cell response to M. tuberculosis antigens have been conducted using an interferon gamma release assay (IGRA), which has been proven to be more efficient than the TST (tuberculin skin test) [Recent studies evaluating immunological evidence of mycobacterial antigens in sarcoidosis patients has renewed interest in the role of mycobacteria in sarcoidosis , indicatin test) . We condM. tuberculosis antigens in patients with sarcoidosis. To identify relevant articles for inclusion in this review, all authors independently searched PubMed, Embase, and Cochrane Library databases for relevant studies published from 1990–2015 using the following terms: sarcoidosis AND mycobacteria (OR) mycobacterium; sarcoidosis AND mycobacterium tuberculosis; and sarcoidosis AND tuberculosis. Additional eligible studies were identified by reviewing the references of all retrieved- literatures and review articles addressing the relationship between sarcoidosis and mycobacteria. The outcome measure of all included studies was positivity incidence of the immune response to M. tuberculosis antigens. No language or geographic restrictions were imposed on identified studies.The aim of this meta-analysis was to collect all publicly available studies on the immune response to M. tuberculosis antigens were extracted onto standardized data collection forms by the two reviewers, and the verified data were entered into a Microsoft Excel spreadsheet . The following items were extracted: 1) the publication details including the study geography (country or region), year of publication, first author and other citation details; 2) the number of patients with sarcoidosis and the type of mycobacterium (M. tuberculosis or other mycobacterium) used in analysis; 3) details of the technique used to evaluate the immune response in samples; 4) the health condition of the control subjects and whether details on TST outcomes were provided and 5) the numbers of the samples with an active immune response to mycobacterial antigens for patients with sarcoidosis and control. No attempt was made to include unpublished data. Methodological quality was assessed by the Newcastle-Ottawa Scale (NOS).Paired reviewers (Chuling Fang and Hui Huang) independently evaluated studies for eligibility using a two-stage procedure. During the first stage, all identified abstracts were evaluated to ensure that they were involved in the relationship between sarcoidosis and mycobacteria. All potentially relevant studies were retrieved and selected for the second stage of the procedure, in which a full-text review was performed to determine whether the studies provided the positivity incidence of the immune response. Any disagreements were resolved by discussion and consensus. Data concerning the immune response to M. tuberculosis, binomial proportions were used in which the numerator was sarcoid samples with active immune response to M. tuberculosis antigens and the denominator was the total number of study samples. As dichotomous outcomes, the percentage of sarcoid samples with a positive immune response out of the total samples versus the same percentage of control samples was expressed as an odds ratio (OR) and a 95% confidence interval (CI). The fixed-effects model was used, and the random-effects model weighted by the Mantel-Haenszel method was utilized for data with significant heterogeneity . P<0.05 was considered statistically significant.The included articles were analyzed using Cochrane Collaboration Review Manager statistical software . To calculate the percentage of sarcoidosis samples with a positive immune reaction to 2 test . An I2 value >50% indicates significant heterogeneity.The impact of heterogeneity on the pooled estimates of individual outcomes of meta-analysis was assessed using the Chi-squared test and/or IA funnel plot test was used to assess publication bias. The funnel plot is a measurement of the log of the OR  against the standard error of the log of the OR . Each point represents a study in meta-analysis.The process of identifying eligible studies is summarized in All studies performed detailed immunology analysis and the meta-analysis included studies conducted around the world . In totaM.tuberculosis antigens. Further, nine studies [The quality scores of all 13 included studies were above five points, ranging from five to nine points. Five studies , 20, 24  studies –19, 24 uM. tuberculosis specific antigens. Among the 253 samples in the sarcoidosis group, 126 exhibited a positive immune response to M. tuberculosis specific antigens, as demonstrated by immunology. The combined results of the nine trials revealed that the sarcoidosis patients had a significantly higher positivity rate of the T-cell immune response to M. tuberculosis specific antigens compared to the controls with PPD- or unknown PPD status  (2 statistics (subgroup of PPD- controls (Q (d.f. = 5) = 4.57, P = 0.47, I2 = 0%); subgroup of controls with unknown PPD status (Q (d.f. = 2) = 1.24, P = 0.54, I2 = 0%)) (2 = 95.6%) (2 = 0%)  . Combine0.00001) . An addi0.00001) . Heterog2 = 0%)) . However= 95.6%) . Further(2 = 0%) . Publicaantigens .M. tuberculosis specific antigens. Of the100 samples in the sarcoidosis group, 55 exhibited a positive immune response to M. tuberculosis specific antigens, as demonstrated by ELISA and immunohistochemical analysis. The combined results of four trials [M. tuberculosis specific antigens than the control group . Further, the combined results of two trials [M. tuberculosis specific antigens than subgroup of PPD- controls . Similarly, combined analysis of another two trials [2 statistic (subgroup of PPD- controls (Q (d.f. = 1) = 0.28, P = 0.60, I2 = 0%); subgroup of controls with unknown PPD status (Q (d.f. = 1) = 0.14, P = 0.71, I2 = 0%)) (2 = 0%). Publication bias was not evident, as estimated by generation of a funnel plot for the studies on the T-cell immune response to M. tuberculosis specific antigens ) . The hetantigens .Meta-analysis was the main method used in this research paper. It is more accurate and reliable than regression analysis or original papers.M. tuberculosis has been a highly contested and challenging issue. Further analysis is important considering their opposite therapeutic effects In the current meta-analysis, a greater positivity incidence of the immune response to M. tuberculosis specific antigens was observed in sarcoidosis group compared to the control group of subjects with PPD- or unknown PPD status for both the T-cell immune response and humoral response, indicating that these antigens induce T-cell-specific responses in the blood or BALF of sarcoidosis patients. However, it is important to note that sarcoidosis patients may be more likely to have positive TST results (i.e. to be more sensitive to LTBI) than healthy individuals due to unknown host factors with no known etiologic link between sarcoidosis and M. tuberculosis. Notably, the positivity incidence of T-cell immune response to M. tuberculosis specific antigens in sarcoidosis group was found to be significantly lower in the sarcoidosis patients than in the PPD+ (LTBI) controls, although the incidences did not differ among the four primary trials. Further, it was hypothesized that M. tuberculosis specific antigens response would not be observed in all sarcoidosis patients, and that the specific mycobacterial antigen may represent just one of the most important factors for the pathogenesis of sarcoidosis.The relationship between sarcoidosis and In the T-cell immune response, no significant heterogeneity was observed in either the subgroup of PPD- controls or in the subgroup of controls with an unknown PPD status. Similarly, no significant heterogeneity was detected in the group of PPD+ (LTBI) controls. Similarly, no significant heterogeneity was detected in the group of PPD+ (LTBI) controls. Further, in the humoral response, no significant heterogeneity was observed in either the subgroup of PPD- controls or the subgroup of controls with an unknown PPD status. However, significant heterogeneity was detected between the two subgroups with PPD- or unknown PPD status on the T-cell immune response, indicating that PPD status strongly influenced experimental outcome.M. tuberculosis antigens are involved in the pathogenesis of sarcoidosis [M. tuberculosis antigens including catalase‑peroxidase antigen (mKatG) and Mtb 16S rRNA in nearly 40% of their sarcoidosis subjects as detected by in situ hybridization [M. tuberculosis (and not the whole mycobacteria) are involved in the pathogenesis of sarcoidosis [M. tuberculosis antigens in sarcoidosis patients; (3) development of mycobacterial disease either coincidentally, before or after development of sarcoidosis [M. tuberculosis antigens or molecular evidence was observed in some sarcoidosis subjects. Therefore, we assumed that other factors besides mycobacterial antigens contribute to the pathogenesis of sarcoidosis.A number of original studies have examined mycobacteria in samples of sarcoidosis patients , 25–32, coidosis , 34. Amodization . Furthercoidosis –37; (4) coidosis , 27; andcoidosis , 39. It coidosis , 40. HowThere are several limitations to this study. First, although data were collected from more than 700 patients, the number of incorporated studies was still small, and therefore these results may have been affected by publication bias. Second, the definite sensitivity of the immunological data is unknown, as they were not described or analyzed in detail in this study. Third, some variations may also have occurred due to differences in local environmental exposure and the fact that some sarcoidosis patients may have a disorder initiated by organisms or triggers other than mycobacteria. Therefore, additional studies would be useful to provide more concrete data to investigate the accuracy of this conclusion are needed.M.tuberculosis) and sarcoidosis. Mycobacteria was not observed in all cases of sarcoidosis, however, these bacteria indeed represent an important factor involved in the pathogenesis of this disease. It has been hypothesized that only some specific, poorly degraded mycobacterial pathogenic antigens contribute to immune-mediated granulomatous inflammation rather than the whole active mycobacteria and that they elicit a type IV immune response.In conclusion, the results of this meta-analysis have demonstrated an association between mycobacteria Click here for additional data file.