Increase In Correlation Time Research Articles

(Invited) Novel Biosensing Platform Based on Image Analysis of Rotational Diffusion of Probe-Modified Janus Particles

Infectious diagnosis of high-risk viruses and pathogenic bacteria is made by PCR testing. RNA virus testing is performed through multiple steps of sample collection, RNA extraction, reverse transcription, and amplification by PCR. Present methods are problematic due to the length of testing time and complexity of the operation.In this study, we focus on the rotational Brownian motion of probe-modified particles and develop a new biosensor that is specific, quick, and simple to detect target DNA/RNA by photographing the rotational Brownian motion of probe-modified particles with a microscope and analyzing the diffusivity, which is the degree of the motion(Fig. A). The Stokes-Einstein-Debye equation, which considers the rotational motion of particles in solution, shows that the rotational diffusivity of particles is inversely proportional to the third power of the particle diameter when the ambient temperature and viscosity of the medium are controlled. In the case of Janus particles, which emit fluorescence only on half their surface, the rotational diffusivity corresponds to the correlation time, which is the correlation intensity per elapsed time of the flashing signal obtained from the rotational Brownian motion of the particles. Based on the above principle, we conducted experiments and found that under the presence of target RNA, Janus particles capture RNA, which leads to the formation of Janus particle-RNA complexes and an increase in particle volume, which in turn leads to an increase in correlation time (Fig. B). Also, the correlation time of the target RNA-Janus particle complex increases with an increase in the target RNA concentration (Fig. C). Furthermore, it was confirmed that the sensitivity and specificity of this sensor reached 85% and 100%, respectively. Since the correlation time can be measured only by microscopic observation and does with no amplification, this sensor is expected to be a simple and rapid detection.

The paradigm of magnetic molecule in quantum matter: Slow molecular spin relaxation

The quantum nature of single-ion magnets, single-molecule magnets, and single-chain magnets has been manifested among other phenomena by magnetic hysteresis due to slow spin relaxation, competing with fast quantum tunneling at low temperatures. Slow spin relaxation, described by Arrhenius-type law with the effective barrier energies Ueff = 50 cm–1, was discovered 3 decades ago in paramagnetic Mn12-acetate complex of oxy-bridged mixed-valence manganese ions, below the blocking temperature TB = 3 K. In contrast to common magnetic materials, it is governed primarily by magnetic anisotropy, set by zero-splitting of spin states of a magnetic ion in a field of ligands, and spin-lattice coupling. The emerging studies on the border of coordination chemistry, physics of spin systems with reduced dimensionality, and nanotechnologies, were performed in search of routes for enhancement of Ueff and TB characteristics, in line with increase of operation temperature and quantum correlation time, mandatory for quantum applications. The best results with TB ∼ 80 K and Ueff ∼ 1261 cm–1, were obtained for DyIII single-ion magnet, so far. Numerous excellent research and review articles address particular activities behind this achievement. It follows, that present challenges are dictated by the rational development of novel, smart magnetic molecules, featured by butterfly cores, cyano-bridges, 2D metal-organic frameworks, and metal-free graphene nanoclusters, as well as stable free radicals, magnetized by spare electrons. These species are briefly considered here with respect to the unique experience of international collaborative activity, established by Prof. Juan Bartolomé.

Stochastic dynamics of a nonlinear vibration energy harvester subjected to a combined parametric and external random excitation: The distinct cases of Itô and Stratonovich stochastic integration

The Stratonovich and Itô interpretations of a stochastic integral are mathematically consistent, distinct representations that yield contrasting response characteristics for stochastic dynamical systems subjected to multiplicative noise, such as parametric random excitation. The contrasting dynamics from the two interpretations currently remain unexplored in vibration energy harvester dynamics. We analytically investigate the dynamics of a generic piezoelectric, nonlinear vibration energy harvester simultaneously subjected to stochastic damping and external random excitation, focusing on the contrasting dynamics engendered by the two interpretations. Numerically solving the Stratonovich and Itô stochastic differential equations in the nonequilibrium regime of harvester dynamics, we find that the Stratonovich version yields significantly higher root mean square values of the harvester voltage output, for lower values of the mechanical damping coefficient. Furthermore, we find positive values for the leading Lyapunov exponent indicating instabilities in the harvester response unique to the Stratonovich interpretation. Additionally, comparing the results for the harvester electrical output between the cases of external excitation represented by the white noise and the Ornstein–Uhlenbeck noise processes, we find lower root mean square values of the voltage output in the latter case. Moreover, the results indicate that the averaged voltage output becomes progressively lower with increasing correlation time of the Ornstein–Uhlenbeck process. Studying the equilibrium dynamics by deriving Fokker–Planck equations for the response amplitude of the harvester using the harmonic balance method and stochastic averaging techniques, we solve for the stationary probability densities to find that the harvester is more likely to attain a well-defined equilibrium state under the Itô interpretation. In summary, the results contribute to the theoretical understanding of the fundamental contrast between the Stratonovich and Itô interpretations in vibration energy harvester dynamics and are expected to motivate advances in harvester design for various applications.

Influence of orientational disorder in the adsorbent on the structure and dynamics of the adsorbate: MD simulations of SO2 in ZSM-22

Structural and dynamical behavior of SO2 molecules within ZSM-22 is studied using molecular dynamics simulations, to understand the influence of orientational disorder (OD) and inter – crystalline spacing in ZSM-22 as a function of adsorbate loading. Addition of inter-crystalline space provides connectivity of isolated pores in ZSM-22 and is shown to suppress both translational and rotational motion of SO2. We infer that geometry and dimensionality of the connecting space are important factors in determining the effects of pore connectivity on the adsorbed species behavior. As a function of OD, decrease in self-diffusion coefficient of SO2 in ZSM-22 is observed. An increase in rotational correlation time and a decrease in libration angle with OD is observed, ascribed to the restriction imposed on the orientational freedom of the adsorbate by an increase in OD. The behavior of SO2 results from an interplay of guest-host interactions and the dimensionality and geometry of confinement.

An underdamped and delayed tri-stable model-based stochastic resonance

Stochastic resonance (SR) is investigated in an underdamped tri-stable potential system driven by Gaussian colored noise and a periodic excitation, where both displacement and velocity time-delayed states feedback are considered. It is challenging to study SR in a second-order delayed multi-stable system analytically. In this paper, the improved energy envelope stochastic average method is developed to derive the analytical expressions of stationary probability density (SPD) and spectral amplification. The effects of noise intensity, damping coefficient, and time delay on SR are analyzed. The results show that the shapes of joint SPD can be adjusted to the desired structure by choosing the time delay and feedback gains. For fixed time delay, the SR peak is increased for negative displacement or velocity feedback gain. Meanwhile, the SR peak is decreased while the optimal noise intensity increases with increasing correlation time of noise. The Monte Carlo simulations (MCS) confirm the effectiveness of the theoretical results.

Water proton NMR relaxation revisited: Ultrahighly diluted aqueous solutions beyond Avogadro’s limit prepared by iterative centesimal dilution under shaking cannot be considered as pure solvent

• Ultramolecular dilutions prepared according to homeopathic pharmacopoeia differ from solvent and from simply diluted samples. • Evidence for an unexpected gradual increase of correlation times of water with dilution in ultrahighly diluted solutions. • Evidence for solute-induced nanostructures in aqueous high dilutions growing with dilution. • Nanostructures result from nucleation between the solute, nanobubbles and elements coming from the medium during preparation. • Nanostructures in ultrahigh dilutions, even ultramolecular, enhance leaching processes in glass containers. The biological activity of ultrahigh dilutions (HDs) as used in homeopathy, especially those beyond Avogadro's limit, is still controversial and an intriguing problem for scientists. Homeopathic remedies are mostly prepared by iterative centesimal dilution under vigorous shaking, called dynamization. Cn corresponds to a dilution factor of 10 -2n , and C12 (10 -24 ) to the theoretical limit of molecular presence. Since the 1990 s, NMR relaxation of water protons has emerged as a potent tool for investigating HDs. This article reviews studies of high methodological quality by five independent teams over more than two decades. They demonstrate an increase in T1 and T1/T2, with a decrease in T2, although less constant, in dynamized aqueous HDs. No variation was observed in the similarly treated solvent controls. The phenomenon seems to be common, regardless of solute, dissolved oxygen, material used (glass or plastic), method of shaking, frequency from 0.02 to 600 MHz. Strikingly, the changes in relaxation times increased gradually with dilution, even in the C12-C30 ultramolecular range and they totally vanished after a heating–cooling cycle directly applied on the sealed NMR tubes. The results were interpreted in terms of increasing correlation times of water, greater than 10 −8 s, resulting from the formation of growing solute-induced nanostructures involving nanobubbles and various elements coming from the medium, the atmosphere and the container. Another unexpected result was that HDs were able to enhance some leaching processes in glass containers.

Synchronization transition in the two-dimensional Kuramoto model with dichotomous noise.

We numerically study the celebrated Kuramoto model of identical oscillators arranged on the sites of a two-dimensional periodic square lattice and subject to nearest-neighbor interactions and dichotomous noise. In the nonequilibrium stationary state attained after a long time, the model exhibits a Berezinskii-Kosterlitz-Thouless (BKT)-like transition between a phase at a low noise amplitude characterized by quasi long-range order (critically ordered phase) and an algebraic decay of correlations and a phase at a high noise amplitude that is characterized by complete disorder and an exponential decay of correlations. The interplay between the noise amplitude and the noise-correlation time is investigated, and the complete, nonequilibrium stationary-state phase diagram of the model is obtained. We further study the dynamics of a single topological defect for various amplitudes and correlation time of the noise. Our analysis reveals that a finite correlation time promotes vortex excitations, thereby lowering the critical noise amplitude of the transition with an increase in correlation time. In the suitable limit, the resulting phase diagram allows one to estimate the critical temperature of the equilibrium BKT transition, which is consistent with that obtained from the study of the dynamics in the Gaussian white noise limit.

Increasing the Correlation Time of Spin-Torque Oscillators Synchronized by Magnetostatic Interactions

Synchronisation of spin-torque oscillators (STOs) via magnetostatic interactions is investigated. In order for arrays of STOs to be used to carry out computational tasks the STOs should remain phase-locked for as long as possible. The correlation time for two STOs is shown to depend on H3/2d, where Hd is the strength of the magnetostatic interaction between the STOs. For a one dimensional array of STOs, introducing an angle between adjacent STOs can reduce the magnetostatic energy and increase the correlation time by an order of magnitude, or more. The increase in correlation time is resilient to moderate distributions of size and position among the STOs.

Optimal control for quantum detectors

Quantum systems are promising candidates for sensing of weak signals as they can be highly sensitive to external perturbations, thus providing excellent performance when estimating parameters of external fields. However, when trying to detect weak signals that are hidden by background noise, the signal-to-noise ratio is a more relevant metric than raw sensitivity. We identify, under modest assumptions about the statistical properties of the signal and noise, the optimal quantum control to detect an external signal in the presence of background noise using a quantum sensor. Interestingly, for white background noise, the optimal solution is the simple and well-known spin-locking control scheme. Using numerical techniques, we further generalize these results to the case of background noise with a Lorentzian spectrum. We show that for increasing correlation time, pulse based sequences, such as CPMG, are also close to the optimal control for detecting the signal, with the crossover dependent on the signal frequency. These results show that an optimal detection scheme can be easily implemented in near-term quantum sensors without the need for complicated pulse shaping.

How wide is the window opened by high-resolution relaxometry on the internal dynamics of proteins in solution?

The dynamics of molecules in solution is usually quantified by the determination of timescale-specific amplitudes of motions. High-resolution nuclear magnetic resonance (NMR) relaxometry experiments—where the sample is transferred to low fields for longitudinal (T1) relaxation, and back to high field for detection with residue-specific resolution—seeks to increase the ability to distinguish the contributions from motion on timescales slower than a few nanoseconds. However, tumbling of a molecule in solution masks some of these motions. Therefore, we investigate to what extent relaxometry improves timescale resolution, using the “detector” analysis of dynamics. Here, we demonstrate improvements in the characterization of internal dynamics of methyl-bearing side chains by carbon-13 relaxometry in the small protein ubiquitin. We show that relaxometry data leads to better information about nanosecond motions as compared to high-field relaxation data only. Our calculations show that gains from relaxometry are greater with increasing correlation time of rotational diffusion.

Molecular Analysis of Retrogradation of Corn Starches.

Changes of the molecular dynamics of water in 5% corn starch pastes and 5% systems composed of starch and non-starchy hydrocolloid were studied during short and long term retrogradation. Low Field NMR was used to record mean correlation times (τc) of water molecules. This molecular parameter reflects the rotation of water molecules within the network of paste. Starches of different amylose and amylopectin content were selected for this study. Comparison of the changes of τc shows how particular polymers bind water molecules. During 90 days of storage, over 50% increase in mean correlation time was recorded in pastes of starches with high amylose content. This suggests that the formation of polymeric network is controlled by amylose to which water is binding. Amylopectin was found to influence the mobility of water in the pastes to a lesser extent with changes in mean correlation times of approximately 10–15% over 90 days. On retrogradation, amylopectin, Arabic and xanthan gums hindered the formation of solid phase structures. Guar gum evoked an increase in mean correlation times of approximately 40–50% during the prolonged process of changes of the molecular dynamics of water. This indicates continued expansion of the polymeric network. Mean correlation time available from spin–lattice and spin–spin relaxation times can be useful in the analysis of the rotational vibrations of the water molecules in biopolymeric structures.

The transport phenomenon of inertia Brownian particles in a periodic potential with non-Gaussian noise

The transport phenomenon (movement and diffusion) of inertia Brownian particles in a periodic potential with non-Gaussian noise is investigated. It is found that proper noise intensity Q will promote particles directional movement (or diffusion), but large Q will inhibit this phenomenon. For large value of Q, the average velocity [Formula: see text] (or the diffusion coefficient D) has a maximum with increasing correlation time [Formula: see text]. But for small value of Q, [Formula: see text] (or D) decreases with increasing [Formula: see text]. In some cases, for the same value of Q and the same value of [Formula: see text], non-Gaussian noise can induce particles directional movement (or diffusion), but Gaussian colored noise cannot.

Evolution of weak noise and regular waves on dissipative shock fronts described by the Burgers model

The interaction of weak noise and regular signals with a shock wave having a finite width is studied in the framework of the Burgers equation model. The temporal realization of the random process located behind the front approaches it at supersonic speed. In the process of moving to the front, the intensity of noise decreases and the correlation time increases. In the central region of the shock front, noise reveals non-trivial behaviour. For large acoustic Reynolds numbers the average intensity can increase and reach a maximum value at a definite distance. The behaviour of statistical characteristics is studied using linearized Burgers equation with variable coefficients reducible to an autonomous equation. This model allows one to take into account not only the finite width of the front, but the attenuation and diverse character of initial profiles and spectra as well. Analytical solutions of this equation are derived. Interaction of regular signals of complex shape with the front is studied by numerical methods. Some illustrative examples of ongoing processes are given. Among possible applications, the controlling the spectra of signals, in particular, noise suppression by irradiating it with shocks or sawtooth waves can be mentioned.

Regime shifts driven by dynamic correlations in gene expression noise.

Gene expression is a noisy process that leads to regime shifts between alternative steady states among individual living cells, inducing phenotypic variability. The effects of white noise on the regime shift in bistable systems have been well characterized, however little is known about such effects of colored noise (noise with nonzero correlation time). Here, we show that noise correlation time, by considering a genetic circuit of autoactivation, can have a significant effect on the regime shift between distinct phenotypic states in gene expression. We demonstrate this theoretically, using stochastic potential, stationary probability density function, and first-passage time based on the Fokker-Planck description, where the Ornstein-Uhlenbeck process is used to model colored noise. We find that an increase in noise correlation time in the degradation rate can induce a regime shift from a low to a high protein concentration state and enhance the bistable regime, while an increase in noise correlation time in the basal rate retains the bimodal distribution. We then show how cross-correlated colored noises in basal and degradation rates can induce regime shifts from a low to a high protein concentration state, but reduce the bistable regime. We also validate these results through direct numerical simulations of the stochastic differential equation. In gene expression understanding the causes of regime shift to a harmful phenotype could improve early therapeutic intervention in complex human diseases.

Array-enhanced logical stochastic resonance subject to colored noise

This paper proposes an approach that uses a parallel array to improve the reliability and robustness of logical stochastic resonance subject to colored noise. The experimental results demonstrate that (i) the increase of array size can extend the optimal range of noise intensity and increase the maximum probability of obtaining correct logic operation. (ii) The optimal range of noise correlation time is broadened with the increase of array size. (iii) The main difference between logical stochastic resonance subject to white noise and colored noise is that the increase of noise correlation time broadens the optimal range of noise intensity when the stochastic noise is colored noise. At the same time, the maximum probability of obtaining correct logic operation is close to 1. Therefore, reliable and robust logic gate can be realized under a certain array size.

Experimental and Quantum Chemical Calculations of Imidazolium Appended Naphthalene Hybrid in Different Biomimicking Aqueous Interfaces.

The effect of solvent polarity and micellar headgroup on a newly designed imidazolium based ionic liquid (IL) conjugated with naphthalene, 1,2-dimethyl-3-((6-(octyloxy)naphthalen-2-yl)methyl)-1H-imidazol-3-ium chloride (IN-O8-Cl), was studied using steady state and time-resolved fluorescence techniques. We observed that the dipole moment in the excited state is remarkably higher than the ground state. The effect of micellar surface charge on the photophysics of IN-O8-Cl in aqueous phase at room temperature was investigated. Formation of premicellar aggregates in sodium dodecylsulfate (SDS) was perceived; further the microenvironment of IN-O8-Cl was examined using steady-state fluorescence spectroscopy. Micropolarity of the micellar environment of SDS was found to be lower than that of cetyltrimethylammonium bromide (CTAB) and triton X-100 (TX100) following the order SDS < TX-100 < CTAB. The binding constant (Kb) and edge excitation red shift (EERS) from the emission maximum suggest that the probe binds strongly to the micelles. Multiexponential behavior was observed in time-resolved fluorescence lifetime studies in all micellar environments. We have observed an increase in rotational correlation time as we move from pure aqueous phase to solution containing surfactants of different head charge. Varieties of spectral parameters were used to justify the region in which the probe is present. The experimentally obtained dipole moment data were justified and explained by the DFT calculations of the electronic properties of IN-O8-Cl molecules in gas phase and in selected solvents.

Effect of tumor microenvironmental factors on tumor growth dynamics modeled by correlated colored noises with colored cross-correlation

The effect of non-immunogenic tumor microenvironmental factors on tumor growth dynamics modeled by correlated additive and multiplicative colored noises is investigated. Using the Novikov theorem, Fox approach and Ansatz of Hanggi, an approximate Fokker–Planck equation for the system is obtained and analytic expression for the steady state distribution Pst(x) is derived. Based on the numerical results, we find that fluctuations of microenvironmental factors within the tumor site with parameter θ have a diffusive effect on the tumor growth dynamics, and the tumor response to the microenvironmental factors with parameter α inhibits growth at weak correlation time τ. Moreover, at increasing correlation time τ the inhibitive effect of tumor response α is suppressed and instead a systematic growth promotion is noticed. The result also reveals that the strength of the correlation time τ has a strong influence on the growth effects exerted by the non-immunogenic component of tumor microenvironment on tumor growth.

P16.31 * THERANOSTIC APPLICATION OF WATER-SOLUBLE GADOLINIUM FULLERENE (GD@FUL) IN EXPERIMENTAL GLIOMA MODEL

Glioblastoma multiforme (GMB) is a highly invasive brain tumour with poor prognosis. Alternative treatments offering a better outcome are needed. Novel approach could be based on gadofullerenes that can be used as diagnostic MR imaging contrast agent and as a therapeutic drug. Water soluble gadofullerene Gd@Ful with composition Gd@C82(OH)x x ≥20 was synthesized for theranostic study. Nanosuspensions of Gd@Ful were used for magnetic relaxation measurements in vitro and for MR imaging of a rat with intracranially implanted C6 glioma. Gd@Ful was shown to reduce proton relaxation times in vitro, and provide dual contrast of T1- and T2-weighted images in a rat brain tumour model after paramagnetic intravenous delivery. Magnetic relaxation times and relaxivity of water protons under action of Gd@Ful were strongly shortened due to cluster formation and increase of motional correlation times of protons in the vicinity of the fulleren cage. The Gd@Ful administration promoted the improvement of glioma contrast enhancement at T2-weighted images due to accumulation of paramagnetic substance at the tumour site. The contrast efficiency of Gd@Ful corresponds to the characteristics of negative contrast agent. Retention of the Gd@Ful in the C6 glioma provides not only the tumor contrast enhancement but also has a high therapeutic relevance. We observed the increased survival rates in animals that were intravenously administered with Gd@Ful. Thus, in experimental group the survival was 75% higher then in the control group, constituting 34.2 ± 9.94 and 19.5 ± 3.02 days respectively (P < 0.001). The Gd@Ful solution is shown to be a contrast enhancer with high anti-tumour therapeutic potency.

Set–Reset latch logical operation induced by colored noise

We examine the possibility of obtaining Set–Reset latch logical operation in a symmetric bistable system subjected to OU noise. Three major results are presented. First, we prove the Set–Reset latch logical operation can be obtained driven by OU noise. Second, while increasing the correlation time, the optimal noise band shifts to higher level and becomes wider. Meanwhile, peak performance degrades from 100% accuracy, but the system can still perform reliable logical operation. Third, at fixed noise intensity, the success probability evolves non-monotonically as correlation time increases. The study might provide development of the new paradigm of memory device. • We prove the Set–Reset latch logical operation can be obtained in nonlinear system. • The LSR phenomenon is obtained driven by OU noise. • Under strong noisy background, the logical output is better driven by strong correlated noise. • At fixed noise intensity, the accuracy evolves nonmonotonically as correlation time increases.

Magnetic Resonance Imaging of Rat C6 Glioma Model Enhanced by Using Water-Soluble Gadolinium Fullerene

Water-soluble gadofullerene Gd@Ful with composition Gd3+@C82(OH)X3– (x ~ 20) was synthesized for theranostic study. Nanosuspensions of Gd@Ful were used for magnetic relaxation measurements in vitro and for magnetic resonance imaging of a rat with intracranially implanted C6 glioma. Gd@Ful was shown to reduce proton relaxation times in vitro and provide dual contrast of T1- and T2-weighted images in a rat brain tumor model after paramagnetic intravenous delivery. Magnetic relaxation times of water protons under action of Gd@Ful were strongly shortened due to cluster formation and increase of motional correlation times of protons in the vicinity of the fullerene cage. The Gd@Ful administration promoted the improvement of glioma contrast enhancement at T2-weighted images due to accumulation of paramagnetic substance at the tumor site. The contrast efficiency of Gd@Ful corresponds to the characteristics of negative contrast agent. The Gd@Ful nanosuspension is shown to be a contrast enhancer with high anti-tumor therapeutic potency. The retention of the Gd@Ful in the tumor resulted in a 75 % increase in survival times of the tumor-bearing animals.