Taras Plakhotnik

Taras Plakhotnik
University of Queensland | UQ · School of Mathematics and Physics

PhD

About

126
Publications
15,553
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3,808
Citations
Additional affiliations
January 2019 - present
University of Queensland
Position
  • Professor (Associate)
August 2007 - December 2018
University of Queensland
Position
  • Professor (Associate)

Publications

Publications (126)
Article
For decades, the thermal broadening of zero-phonon lines of single organic molecules embedded in amorphous solids was associated with their weak electron-phonon coupling to quasilocal vibrational modes. In this paper we show that the generally accepted perturbative approach for the pure dephasing problem is not applicable to the studied chromophore...
Article
Full-text available
We investigate doping and formation of luminescent point defects in nanodiamond at high pressures and high temperatures (HPHT) in fluorine-containing hydrocarbon growth systems with an excessive content of dopant organosilicon component. It is shown experimentally that the average concentration of silicon-vacancy centers (SiV-) tends to increase pr...
Article
Full-text available
Peculiarities of the processes of self-assembly of carbon under pressure up to 8 GPa and temperatures up to 1600°C in pure carbon, hydrocarbon, fluorocarbon, organometallic systems and binary mixtures of all-carbon, hydrocarbon, and fluorocarbon compounds have been revealed in the course of studies of pressure and temperature-induced transformation...
Article
Nanodiamonds containing luminescent point defects are widely explored for applications in quantum biosensing such as nanoscale magnetometry, thermometry, and electrometry. A key challenge in the development of such applications is the large variation in fluorescence properties observed between particles, even when obtained from the same batch or no...
Preprint
Full-text available
Nanodiamonds containing luminescent point defects are widely explored for applications in quantum bio-sensing such as nanoscale magnetometry, thermometry, and electrometry. A key challenge in the development of such applications is a large variation in fluorescence properties observed between particles, even when obtained from the same batch or nom...
Article
Full-text available
A detailed description is given of how the liquid water content (LWC) and the ice water content (IWC) can be determined accurately and absolutely from the measured water Raman spectra of clouds. All instrumental and spectroscopic parameters that affect the accuracy of the water-content measurement are discussed and quantified, specifically, these a...
Article
Full-text available
Functionalized diamond nanocrystals persistently expand their use for sensing and labeling in a biological context. The surface of such crystals modified chemically adds additional modality to such applications. In this Perspective, we discuss mainly applications in nanothermometry but begin with a brief general introduction of fluorescent nanodiam...
Article
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In this paper, for the first time, tuned near-zero-index materials are used in a structure for the long-distance projection of very closely spaced objects with subwavelength separation. Near-zero-index materials have never been used for subwavelength projection/imaging. The proposed novel structure is composed of a two-layer slab that can project t...
Article
Full-text available
Modern image detectors with exceptionally low readout noise of about one electron ( ${{\rm e}^ -}$ e − ) per pixel allow for applications with ultra-low levels of light intensity. In this Letter, we report a property of scientific CMOS detectors that makes accurate spectroscopy at ultra-low levels of illumination depending on a thorough calibration...
Article
Full-text available
Understanding heat dissipation processes at nanoscale during cellular thermogenesis is essential to clarify the relationships between the heat and biological processes in cells and organisms. A key parameter determining the heat flux inside a cell is the local thermal conductivity, a factor poorly investigated both experimentally and theoretically....
Preprint
Full-text available
Understanding heat dissipation processes at nanoscale during cellular thermogenesis is essential to clarify the relationships between the heat and biological processes in cells and organisms. A key parameter determining the heat flux inside a cell is the local thermal conductivity, a factor poorly investigated both experimentally and theoretically....
Article
Full-text available
This short review begins with a brief introductory summary of luminescence nanothermometry. Current applications of luminescence nanothermometry are introduced in biological contexts. Then, theoretical bases of the “temperature” that luminescence nanothermometry determines are discussed. This argument is followed by the 105 gap issue between simple...
Article
Full-text available
We have produced two types of synthetic nanodiamonds Si- and Si,P-doped and have characterized thermal susceptibilities of the spectral band of silicon-vacancy (SiV-) centers at approximately 740 nm in each case. The covered temperature range from 295\,K to 350\,K is of interest for thermometry in biological systems. Comparison of the relative brig...
Preprint
Full-text available
We have characterized thermal susceptibilities of the spectral band at 740 nm of silicon-vacancy (SiV) centers in Si- and Si,P-doped nanodiamonds over a temperature range from 295 K to 350 K, which is of interest for thermometry in biological systems. Si-doped crystals reveal linear dependence of the SiV zero-phonon line position, width and relativ...
Article
Fluorescence excitation spectra of single terrylene molecules in transparent naphthalene and polyethylene matrices at ultralow (30–100 mK) temperatures have been studied under the conditions where the widths of zero-phonon spectral lines are determined only by the lifetime T1 of the excited electronic state. The experimentally observed dispersion o...
Preprint
Full-text available
Nanoscale thermometry is paramount to study primary processes of heat transfer in solids and is a subject of hot debate in cell biology. Here we report ultrafast temperature sensing using all-optical thermometry exploiting synthetic nanodiamonds with silicon-vacancy (SiV) centres embedded at a high concentration. Using multi-parametric analysis of...
Article
Full-text available
The paper describes application of diamond nano crystals to research on dynamic processes in small (less than 1 mm across) evaporating droplets deposited on a solid substrate. Such droplets are used as a model system for testing proposed bio applications of nitrogen-vacancy centers in diamond. We demonstrate that a high spatial resolution of our me...
Article
Full-text available
A theoretical framework is presented that permits investigations of the relation between inelastic backscattering from microparticles and bulk samples of Raman-active materials. It is based on the Lorentz reciprocity theorem and no fundamental restrictions concerning the microparticle shape apply. The approach provides a simple and intuitive explan...
Preprint
A theoretical framework is presented that permits investigations of the relation between inelastic backscattering from microparticles and bulk samples of Raman-active materials. It is based on the Lorentz reciprocity theorem and no fundamental restrictions concerning the microparticle shape apply. The approach provides a simple and intuitive explan...
Preprint
This paper presents a method for determination of the size distribution for diamond nanocrystals containing luminescent nitrogen-vacancy (NV) centers using the luminescence intensity only. We also revise the basic photo physical properties of NV centers and conclude that the luminescence quantum yield of such centers is significantly smaller than t...
Article
Full-text available
This paper presents a method for determination of the size distribution for diamond nanocrystals containing luminescent nitrogen-vacancy (NV) centers using the luminescence intensity only. We also revise the basic photo physical properties of NV centers and conclude that the luminescence quantum yield of such centers is significantly smaller than t...
Article
Full-text available
Measurements of Raman backscattering spectra between −15 °C and 22 °C in liquid water (including its supercooled state) and in polycrystalline ice (−35 °C to 0 °C) at two excitation wavelengths (407 and 532 nm) are presented. It is found that the spectrum-integrated backscattering cross section of the 3400 cm⁻¹ band is about 1.2 times larger for ic...
Article
Full-text available
We have measured 10 and 20 mT magnetic fields using NV centers in nanodiamonds and have demonstrated that the accuracy of these measurements is about 20 μT. This value is an order of magnitude larger than the precision defined by random fluctuations in the measurements. The presented analysis indicates that the 20 μT systematic errors at such field...
Article
This paper reviews applications of diamonds for sensing of magnetic and electrical fields, pressure and temperature. Considerable attention is focussed on the interaction of spins with static and oscillating magnetic fields as well as applications of such fields to spin control. A particular focus is on the spin of nitrogen-vacancy centers. Electro...
Article
We have synthesized novel composite particles made of single-domain nanomagnets chemically bound to nanocrystals of diamond. Optically detected magnetic resonance spectra of nitrogen-vacancy centers in diamond allowed us to estimate the magnetic field of the nanomagnets and to observe the saturation of their magnetization when an external field of...
Article
Full-text available
We demonstrate a temperature noise floor of 0.3 K [Formula: see text] and a long-term stability better than 0.6 K (peak-to-peak value) using a single crystal of diamond smaller than 50 nm across and containing about 100 nitrogen-vacancy centres as a temperature sensor. We compare the achieved characteristics to other single-particle sensors and sho...
Article
Full-text available
Applications of negatively charged nitrogen-vacancy center in diamond exploit the center's unique optical and spin properties, which at ambient temperature, are predominately governed by electron-phonon interactions. Here, we investigate these interactions at ambient and elevated temperatures by observing the motional narrowing of the center's exci...
Preprint
The negatively-charged nitrogen-vacancy (NV) center in diamond is at the frontier of quantum nano-metrology and bio-sensing. Recent attention has focused on the application of high-sensitivity thermometry using the spin resonances of NV centers in nano-diamond to sub-cellular biological and biomedical research. Here, we report a comprehensive inves...
Article
Full-text available
The negatively-charged nitrogen-vacancy (NV) center in diamond is at the frontier of quantum nano-metrology and bio-sensing. Recent attention has focused on the application of high-sensitivity thermometry using the spin resonances of NV centers in nano-diamond to sub-cellular biological and biomedical research. Here, we report a comprehensive inves...
Article
Full-text available
We demonstrate a way of contrast increasing in wide-field optical images of diamond nanocrystals containing nitrogen-vacancy (NV) centers surrounded by an autofluorescing material, as in the case of intercellular imaging. Subtraction of an image taken in the presence of an external magnetic field of about 25 mT from an image of the same area measur...
Article
Full-text available
Despite a long history, the Raman scattering coefficient of water has so far only been measured with 10% uncertainty using a 95% confidence interval. In this paper, we present an experiment where we have achieved 1.5% uncertainty by using a low concentration of Rhodamine 6G in ethanol as a reference along with accurate consideration of polarization...
Article
Full-text available
The photoluminescence of the negatively charged nitrogen-vacancy (NV−) center displays anomalous saturation behavior at high excitation pulse energies. Where the luminescence is expected to approach a maximum value asymptotically, we have found that it instead drops by as much as a factor of two. In this report, we present evidence that these effec...
Article
Spectral diffusion of the emission line of single colloidal nanocrystals is generally regarded as a random process. Here, we show that each new spectral position has a finite memory of previous spectral positions, as evidenced by persistent anticorrelations in time series of spectral jumps. The anticorrelation indicates that there is an enhanced pr...
Article
Full-text available
Pulsed laser excitation causes the luminescence of Nitrogen Vacancy centers in diamond to unexpectedly decrease with increasing pulse energy. This decrease is observed in both the negatively charged and neutral centers and is caused by shortening of the luminescence lifetimes of the centers of both types. In darkness, the luminescence does not show...
Article
Full-text available
An unusual two- to threefold decrease in the luminescence intensity of nitrogen-vacancy centers in 30 nm diamonds under increasing pulsed-laser irradiation (up to the level of 0.1 J cm−2) has been measured. The effect showed little dependence on the pulse repetition rate below 1 MHz and was accompanied by insignificant changes in the emission spect...
Article
We show that the wandering of transition frequencies in colloidal quantum dots does not follow the statistics expected for ordinary diffusive processes. The trajectory of this anomalous spectral diffusion is characterized by a sqrt[t] dependence of the squared deviation. The behavior is reproduced when the electronic states of quantum dots are assu...
Article
Full-text available
It is shown that the intensity of photoluminescence of nitrogen-vacancy (NV) centers in nanodiamond decreases 4-fold (with a wide spread among nanocrystals) when the surrounding temperature rises from 300 to 670 K. The effect is accompanied by a 2.7-fold decrease in the luminescence lifetime but negligible changes in the shape of the emission spect...
Article
Spectral fluctuations observed in single CdSe/ZnS nanocrystals at 5 K are found to be entirely the result of discrete charge hops in the local environment of the nanocrystal, which occur at a rate comparable to the acquisition time of a single spectrum. We show that intervals between discrete spectral hops introduce a correlation between the succes...
Article
In this work we quantify and characterise the effects of air-oxidation on nitrogen-vacancy defect luminescence in both high-temperature-high-pressure and detonation synthesized nanodiamonds using Raman and luminescence spectroscopies. We find that oxidation treatments result in an increased nitrogen-vacancy centre excited state lifetime from 13 ns...
Article
Full-text available
Nitrogen-vacancy colour centres in diamond can undergo strong, spin-sensitive optical transitions under ambient conditions, which makes them attractive for applications in quantum optics, nanoscale magnetometry and biolabelling. Although nitrogen-vacancy centres have been observed in aggregated detonation nanodiamonds and milled nanodiamonds, they...
Article
Full-text available
To model the light-guiding properties of a hexagonal array of dielectric cylinders, we have numerically solved Maxwell’s equations with the finite-difference time-domain technique. The sizes and refractive indices of the cylinders are representative of those of the outer segments of the cone photoreceptors in the human central retina. In the array,...
Article
A general method for counting of obscure events in presence of detection noise is presented. The method combines the measurement data with additional information about the system under investigation to improve the measurement accuracy with the help of probability theory. As an example, we apply the method to the case of counting molecules in a micr...
Article
Full-text available
A study was conducted to investigate the properties of weakly bound clusters of single-digit nanodiamonds (SND) using spectrally and temporally resolved luminescence detection, electron paramagnetic resonance (EPR) spectroscopy, and transmission electron microscopy (SEM). Nitrogen-vacancy (NV) centers were created in diamonds by high-energy proton...
Article
Full-text available
This book reviews recently developed theoretical and numerical approaches to deal with optical and mechanical signals from individual molecules. The character of data generated by single molecules, and more generally by single nano-objects, qualitatively differs from those obtained in conventional experiments on large ensembles of molecules. Fluctu...
Article
We propose a new methodology for probing transport of just one electron, a process of great importance both in nature and in artificial devices. Our idea for locating a single electron is analogues to the conventional GPS where signals from several satellites are used to locate a macro object. Using fluorescent molecules as tiny sensors, it is poss...
Article
Abstract We report on the first demonstration of nanodiamond (ND) as a scattering optical label in a biological environment. NDs were efficiently transfected into cells using cationic liposomes, and imaged using differential interference and Hoffman modulation ‘space’ contrast microscopy techniques. We have shown that 55 nm NDs are biologically ine...
Article
Abstract This paper reviews a number of used and/or proposed ideas for optical detection of small particles including single-molecules. Different techniques (direct absorption and scattering, interferometry, use of sub Poissonian statistics, cavity enhancement, and thermal lens detection) are compared in terms of signal-to-noise (SNR) ratio. It is...
Article
Full-text available
The ultimate sensitivity of optical detection is limited by the signal-to-noise ratio (SNR). The first part of the paper shows that coherence plays an important role in the noise analysis. Although interference between an auxiliary wave and a signal wave makes the photo detector response to the signal stronger, the coherent noise also enhances. Thi...
Article
A proposal for using single molecules as nanoprobes capable of detecting the trajectory of an elementary charge is discussed in detail. Presented numerical simulations prove that this single-molecule technique allows determination of a three-dimensional single-electron displacement within a few seconds with an accuracy better than 0.006 nm. Surpris...
Conference Paper
A rigorous numerical solution is presented for plane wave scattering by a photoreceptor cell. The calculated optical intensity distribution exhibits axial oscillations which are explained on the basis of substantial Bessel-wave type radiation mode excitation.
Article
Full-text available
We report on the observation of the excitation/emission spectrum of a dendrimer-encapsulated gold nanocluster; the synthesis of Au-PAMAM was based on reduction of HAuCl4 x 3 H2O co-dissolved in methanol together with fourth-generation OH-terminated PAMAM.
Article
Full-text available
Electron-multiplying charge coupled devices promise to revolutionize ultrasensitive optical imaging. The authors present a simple methodology allowing reliable measurement of camera characteristics and statistics of single-electron events, compare the measurements to a simple theoretical model, and report camera performance in a truly photon-counti...
Article
Full-text available
Typical disturbances of biological environment such as background scatter and refractive index variations have little effect on the size-dependent scattering property of highly refractive nanocrystals, which are potentially attractive optical labels. We report on what is to our knowledge the first investigation of these scattering optical labels, a...
Article
Optical Bloch equations are widely used for describing dynamics in a system consisting molecules, electromagnetic waves, and a thermal bath. We analyze applicability of these equations to a single molecule imbedded in a solid matrix. Classical Bloch equations and the limits of their applicability are derived from more general master equations. Simp...
Article
Full-text available
A straightforward derivation of relativistic expressions for the mechanical momentum, kinetic and total energies, and mass-energy equivalence (including potential energy) which does not require any knowledge of the energy-momentum relation for electromagnetic waves or consideration of elastic collisions, but is directly based on Newton's second law...
Article
Full-text available
A new design of an optical resonator for generation of single-photon pulses is proposed. The resonator is made of a cylindrical or spherical piece of a polymer squeezed between two flat dielectric mirrors. The mode characteristics of this resonator are calculated numerically. The numerical analysis is backed by a physical explanation. The decay tim...
Article
The fluorescence of single molecules coupled to a thermal bath is studied both experimentally and theoretically. The effect of different fluctuations on the coherence properties of resonance fluorescence is considered first. Coherence is measured in an interference experiment where a single molecule is used as a light source. A standard approach ba...
Article
Fluorescence of single molecules coupled to a pseudo localized vibration (PLV) and a thermal bath is studied both experimentally and theoretically. The coupled system molecule-PLV is described by master equations which are tested in an experiment where a shape of an excitation spectral line of a single molecule is accurately measured over six order...
Article
Absorption of single molecules is considered as a special case of an interference effect. Different schemes of interference measurements, which are more suitable for single molecules, are described. Advantages and disadvantages of absorption detection relative to emission (luminescence) detection are analyzed. A great attention is paid to a compari...
Article
Full-text available
A novel technique of saturation spectroscopy is applied to study the individual vibronic spectra of single impurity molecules embedded in a low-temperature solid matrix. Homogeneous linewidths and vibrational frequencies for two lower vibronic levels of the excited electronic state S1 are determined for several terrylene single molecules in a napht...
Article
The paper briefly overviews a master equation theory for the case of a single pseudolocal vibration interacting with an electronic molecular transition, a phonon bath, and laser irradiation. The theory is valid for a broad range of laser powers. At low laser powers it was compared to sudden-jump model. Qualitatively, both theories predict that in a...
Article
We present a progress report on investigations of dye-doped microstructures. Motivated by the effect that a confined sample volume may have upon the optical linewidths of dye doped into a small sample, we studied polystyrene microspheres (300nm in diameter) doped with terrylene. Terrylene doped into polystyrene microspheres has a quantum efficiency...
Article
Full-text available
We built an interferometer where one of the two slits of a classical Young's setup is replaced by a single molecule embedded in a solid matrix. This enabled direct measurement of the first order coherence of the 0-0 single-molecule emission, which at high excitation powers proves to be split in coherent and incoherent parts. We demonstrate an order...
Article
Transition frequency jumps for single terrylene molecules in a polyethylene matrix caused by resonant laser irradiation are investigated at 30 mK. These jumps are not accompanied by substantial sample heating. A model for the effect is proposed, based on the interaction of tunneling two-level systems (TLSs) surrounding the single molecule with high...
Article
Linewidth measurements for single terrylene molecules in polyethylene at a temperature of 30 mK indicate that there is a distribution of lifetimes for the terrylene molecules with a relative standard deviation of ∼ 20%. An analysis of the linewidth–line area correlation shows that the variations arise from approximately equal radiative and nonradia...
Article
Detailed analysis is done for the case of a single pseudo local phonon interacting with an electronic molecular transition and a phonon bath. Both the sudden-jump model and the master equation formalism predict a complex optical line shape for a single-molecule embedded in a solid matrix. In addition to the conventional Lorentzian, the line consist...
Article
Fluorescence excitation spectroscopy is used to study vibronic transitions in terrylene molecules doped in a naphthalene crystal. Evidence for the excitation of individual dye molecules is reported. The average linewidth (FWHM) for transitions to the first and second vibronic levels is, in both cases, 30(4) GHz. Linewidths and vibrational frequenci...
Article
The main subject of this paper is the characterization of distributions. Methods are discussed for finding characteristic parameters like the mean and width for three model distributions, namely, Gaussian, rectangular, and Lorentzian, with the greatest emphasis placed on Lorentzian distributions because of their special properties and their central...
Article
The temperature and laser-power dependent S1 ← S0 spectra of single diphenyloctatetraene molecules in n-tetradecane are investigated using one- and two-photon excitation at cryogenic temperatures. Under one-photon excitation, the single-molecule transitions shift to lower frequencies and the line widths increase with increasing temperature while th...
Article
Full-text available
This paper reviews a number of used and/or proposed ideas for optical detection of small particles including single molecules. Different techniques (direct absorption and scattering, interferometry, use of sub Poissonian statistics, cavity enhancement, and thermal lens detection) are compared in terms of signal-to-noise ratio. It is shown that scat...
Article
Linewidth distributions for single terrylene molecules in polyethylene have been measured in the temperature range from 30 mK to 1.83 K. The temperature dependence of the average linewidth is linear over the full temperature range. Linewidth distributions were simulated using the tunneling two-level system model and compared to the data in order to...
Article
One- and two-photon excitation spectra, as well as absorption and emission spectra of diphenyloctatetraene (DPOT) in n-alkanes are investigated at low temperatures. For DPOT in n-octane we report on the measurements of one-photon excitation and emission spectra and for DPOT in n-tetradecane (TD) on the measurements of one- and two-photon excitation...
Article
The excitation line shape of a single terrylene molecule in a naphthalene crystal has been investigated. In addition to the conventional Lorentzian, it consists of a dispersive component in the core region and a sideband. This is due to a pseudolocal phonon caused by the substitution of a host molecule with the chromophore. When the pseudolocal pho...
Article
Linewidth distributions for single terrylene molecules in polyethylene have been measured in the temperature range from 30 mK to 1.83 K. The temperature dependence of the average linewidth is best described by a linear relationship over the full temperature range. At 30 mK, the linewidth distribution has a full-width at half-maximum of &18.6 MHz an...
Article
In this work, frequency trajectories for a single terrylene molecule in n-hexadecane undergoing light-induced spectral diffusion are studied in detail. The molecule was scanned over 5000 times at three different laser powers and jumped between 6 sites. Two mechanisms for the jumping are suggested and compared to the data statistically. The linewidt...
Article
The line width distributions for single terrylene molecules in a naphthalene crystal have been measured at temperatures down to 30 mK. The line width distribution becomes narrower with decreasing temperature, and has a full-width at half-maximum of approximately 4.3(13) MHz at 30 mK and an average line width of 42.7(3) MHz.
Article
When a single quantum system (SQS) interacts with a fluctuating environment, ordinary approaches to spectroscopy fail because measured spectra are subject to strong stochastic fluctuations. Strictly speaking, it is also impossible to employ spectral line shape theories based on the fluctuation dissipation theorem for such systems. Such theories app...
Article
In this work, discrepancies between measured distributions of single-molecule linewidths and distributions calculated using the standard tunneling model in the sudden jump approximation are investigated for terrylene and di-tert-butylterrylene molecules in polyvinylbutyral (PVB). The agreement between experimental results and theory is explored wit...
Article
In this work, discrepancies between measured single-molecule linewidth distributions and distributions simulated with the standard tunneling model in the sudden-jump approximation are studied for terrylene and di-tert-butylterrylene dopant molecules in poly(vinylbutyral). The experimental data has been carefully checked for systematic errors. It is...
Article
A general conceptual problem of time-dependent single molecule spectra is discussed theoretically in the framework of recently developed intensity-time-frequency correlation spectroscopy. It is shown that the new method is closely related to a “gedanken” three-pulse photon echo experiment done on an ensemble of identical molecules interacting with...
Article
Full-text available
A new method based on the calculation of autocorrelation functions for spectra measured at a high acquisition rate is developed to study spectral dynamics of single molecules. The technique allows for spectroscopy with time resolutions down to the luminescence lifetime. The method is used to study spectral diffusion in two-photon excitation spectra...
Article
Full-text available
Scanning near-field optical microscopy (SNOM) is an optical microscopy whose resolution is not bound to the diffraction limit. It provides chemical information based upon spectral, polarization and/or fluorescence contrast images. Details as small as 20 nm can be recognized. Photophysical and photochemical effects can be studied with SNOM on a simi...
Article
One- and two-photon excitation (OPE and TPE) spectra of single 1,8-diphenyloctatetraene molecules in n-tetradecane (transition at 444 nm) were recorded at cryogenic temperature. The high-power infrared light used for TPE changed the conditions in the sample so that the number of single molecule lines observed in OPE spectra was approximately twice...
Article
We report investigations on one- and two-photon excitation of single molecules of diphenyloctatetraene in n-tetradecane at cryogenic temperatures. Saturation intensities, count rates and linewidths of single molecules are compared with corresponding ensemble values obtained from statistical fine structure investigations. The single-molecule linewid...