Charge Perturbation Research Articles

Phase transition and thermodynamic stability in extended phase space and charged Hořava–Lifshitz black holes

For charged black holes in Horava-Lifshitz gravity, a second order phase transition takes place in extended phase space where the cosmological constant is taken as thermodynamic pressure. We relate the second order nature of phase transition to the fact that the phase transition occurs at a sharp temperature and not over a temperature interval. Once we know the continuity of the first derivatives of the Gibbs free energy, we show that all the Ehrenfest equations are readily satisfied. We study the effect of the perturbation of the cosmological constant as well as the perturbation of the electric charge on thermodynamic stability of Horava-Lifshitz black hole. We also use thermodynamic geometry to study phase transition in extended phase space. We investigate the behavior of scalar curvature of Weinhold, Ruppeiner, and Quevedo metric in extended phase space of charged Horava-Lifshitz black holes. It is checked if these curvatures could reproduce the result of specific heat for the phase transition.

Langmuir wave in a dusty plasma with nonextensive electrons

The effect of the dust charge perturbation on Langmuir waves in a dusty plasma with nonextensive electrons and Maxwellian ions is investigated within the fluid theory framework, where the sink term of electrons in the continuity equation is considered. The dispersion of Langmuir waves shows that the dust charge relaxation introduces an additional source of dissipation in Langmuir waves. The damping rate of Langmuir oscillation caused by the dust charge fluctuations is bigger than the one with Maxwellian electrons when the nonextensively distributed electrons have a suprathermal tail. On the contrary, the excess of low energy electrons for nonextensively distributed electrons can lower the damping rate of Langmuir oscillation. These differences are mainly due to the modification of the unperturbed electron attachment frequency by the nonextensively distributed electrons. Our results may be of wide relevance to space and interstellar plasmas.

Charged black rings at large D

We study the charged slowly rotating black holes in the Einstein-Maxwell theory in the large dimensions (D). By using the 1/D expansion in the near regions of the black holes we obtain the effective equations for the charged slowly rotating black holes. The effective equations capture the dynamics of various stationary solutions, including the charged black ring, the charged slowly rotating Myers-Perry black hole and the charged slowly boosted black string. Via different embeddings we construct these stationary solutions explicitly. For the charged black ring at large D, we find that the charge lowers the angular momentum due to the regularity condition on the solution. By performing the perturbation analysis of the effective equations, we obtain the quasinormal modes of the charge perturbation and the gravitational perturbation analytically. Like the neutral case the charged thin black ring suffers from the Gregory-Laflamme-like instability under the non-axisymmetric perturbations, but the charge weakens the instability. Besides, we find that the large D analysis always respects the cosmic censorship.

Superradiant instability of near extremal and extremal four-dimensional charged hairy black holes in anti–de Sitter spacetime

We study the instability of near extremal and extremal four-dimensional AdS charged hairy black hole to radial neutral massive and charged massless scalar field perturbations. We solve the scalar field equation by using the improved asymptotic iteration method and the time domain analysis and we find the quasinormal frequencies. For the charged scalar perturbations, we find the superradiance condition by computing the reflection coefficient in the low-frequency limit and we show that in the superradiance regime, which depends on the scalar hair charge, all modes of radial charged massless perturbations are unstable, indicating that the charged hairy black hole is superradiantly unstable. On the other hand, calculating the quasinormal frequencies of radial neutral scalar perturbations in this background, we found stability of the charged hairy black hole.

Companion and Point-of-Care Sensor System for Rapid Multiplexed Detection of a Panel of Infectious Disease Markers

A nanochannel-based electrochemical biosensor has been demonstrated for rapid and multiplexed detection of a panel of three biomarkers associated with rapid detection of sepsis. The label-free biosensor detected procalcitonin (PCT), lipoteichoic acid (LTA), and lipopolysaccharide (LPS) from human whole blood. The biosensor comprises a nanoporous nylon membrane integrated onto a microelectrode sensor platform for nanoconfinement effects. Charge perturbations due to biomarker binding are recorded as impedance changes using electrochemical impedance spectroscopy. The measured impedance change is used to quantitatively determine the concentration of the three biomarkers using antibody receptors from the tested sample. We were successful in detecting and quantifying the three biomarkers from whole blood. The limit of detection was 0.1 ng/mL for PCT and 1 µg/mL for LPS and LTA. The sensor was able to demonstrate a dynamic range of detection from 01.1 ng/mL to 10 µg/mL for PCT and from 1 µg/mL to 1000 µg/mL for LPS and LTA biomarkers. This novel technology has promising preliminary results toward the design of sensors for rapid and sensitive detection of the three panel biomarkers in whole blood toward diagnosis and classification of sepsis.

Ionic Strength, Surface Charge, and Packing Density Effects on the Properties of Peptide Self-Assembled Monolayers.

The various environmental parameters of packing density, ionic strength, and solution charge were examined for their effects on the properties of the immobilized peptide mimotope CH19 (CGSGSGSQLGPYELWELSH) that binds with the therapeutic antibody Trastuzumab (Herceptin) on a gold substrate. The immobilization of CH19 onto gold was examined with a quartz crystal microbalance (QCM). The QCM data showed the presence of intermolecular interactions resulting in the increase of viscoelastic properties of the peptide self-assembled monolayer (SAM). The CH19 SAM was diluted with CS7 (CGSGSGS) to decrease the packing density as CH19/CS7. The packing density and ionic strength parameters were evaluated by atomic force microscopy (AFM), ellipsometry, and QCM. AFM and ellipsometry showed a distinct conformational difference between CH19 and CH19/CS7, indicating a relationship between packing density and conformational state of the immobilized peptide. The CH19 SAM thickness was 40 Å with a rough topology, while the CH19/CS7 SAM thickness was 20 Å with a smooth topology. The affinity studies showed that the affinity of CH19 and CH19/CS7 to Trastuzumab were both on the order of 107 M-1 in undiluted PBS buffer, while the dilution of the buffer by 1000× increased both SAMs affinities to Trastuzumab to the order of 1015 M-2 and changed the binding behavior from noncooperative to cooperative binding. This indicated that ionic strength had a more pronounced effect on binding properties of the CH19 SAM than packing density. Electrochemical impedance spectroscopy (EIS) was conducted on the CH19/CS7 SAM, which showed an increase in impedance after each EIS measurement cycle. Cyclic voltammetry on the CH19/CS7 SAM decreased impedance to near initial values. The impact of the packing density, buffer ionic strength, and local charge perturbation of the peptide SAM properties was interpreted based on the titratable sites in CH19 that could participate in the proton transfer and water equilibrium.

Reissner–Nordstrom–anti–de Sitter nontopological solitons in broken Einstein-Maxwell-Higgs theory

Results are presented from numerical simulations of the Einstein-Maxwell-Higgs equations with a broken U(1) symmetry. Coherent nontopological soliton solutions are shown to exist that separate an anti--de Sitter (AdS) true vacuum interior from a Reissner-Nordstrom (RN) false vacuum exterior. The stability of these bubble solutions is tested by perturbing the charge of the coherent solution and evolving the time-dependent equations of motion. In the weak gravitational limit, the short-term stability depends on the sign of $(\ensuremath{\omega}/Q){\ensuremath{\partial}}_{\ensuremath{\omega}}Q$, similar to $Q$-balls. The long-term end state of the perturbed solutions demonstrates a rich structure and is visualized using ``phase diagrams.'' Regions of both stability and instability are shown to exist for ${\ensuremath{\kappa}}_{g}\ensuremath{\lesssim}0.015$, while solutions with ${\ensuremath{\kappa}}_{g}\ensuremath{\gtrsim}0.015$ were observed to be entirely unstable. Threshold solutions are shown to demonstrate time-scaling laws, and the space separating true and false vacuum end states is shown to be fractal in nature, similar to oscillons. Coherent states with superextremal charge-to-mass ratios are shown to exist and observed to collapse or expand, depending on the sign of the charge perturbation. Expanding superextremal bubbles induce phase transitions to the true AdS vacuum, while collapsing superextremal bubbles can form nonsingular strongly gravitating solutions with superextremal RN exteriors.

BMS type symmetries at null-infinity and near horizon of non-extremal black holes

In this paper we consider a generally covariant theory of gravity, and extend the generalized off-shell ADT current such that it becomes conserved for field dependent (asymptotically) Killing vector field. Then we define the extended off-shell ADT current and the extended off-shell ADT charge. Consequently, we define the conserved charge perturbation by integrating from the extended off-shell ADT charge over a spacelike codimension two surface. Eventually, we use the presented formalism to find the conserved charge perturbation of an asymptotically flat spacetime. The conserved charge perturbation we obtain is exactly matched with the result of Ref. (Barnich and Troessaert, 12:105 2011). These charges are as representations of the $$\hbox {BMS}_4$$ symmetry algebra. Also, we find that the near horizon conserved charges of a non-extremal black hole with extended symmetries are the Noether charges. For this case our result is also exactly matched with that of Ref. (Donnay et al., arXiv:1607.05703 [hep-th], 2016).

Experimental investigation of cycling behaviour of pilot-scale thermal oil packed-bed thermal storage system

Extensive experimental study of dual media thermocline thermal energy storage using rock and sand as solid matrix and thermal oil as heat transfer fluid is presented. The work is devoted to the establishing of repeatable behaviours observed with multiple charge/discharge cycles and to the influences of operating parameters. Experimental results show that established behaviours are independent of most of operating parameters, notably tank initial state, mass flow rate and temperature ranges, and mainly depend on thermocline control strategy, i.e. part of the thermal gradient which is pulled out of the tank in charge and discharge. Experimental performances have been determined for a large range of control strategies and show tank utilisation rate ranging from about 10% to more than 80%. Thermocline response to perturbations has been studied and shows that partial charge perturbations lead to performances reduction with rapid return to established behaviours. These results may strongly enhance dual media thermocline understanding and may help design and integration of such TES in a given process.

Fe(II)/Fe(III) Redox Process Can Significantly Modulate the Conformational Dynamics and Electrostatics of Pirin in NF-κB Regulation.

Pirin is an iron (Fe)-dependent regulatory protein of nuclear factor κB (NF-κB) transcription factors. Binding studies have suggested that the oxidative state of iron plays a crucial role in modulating the binding of Pirin to NF-κB p65, in turn enhancing the binding of p65 to DNA. The Fe(III) form of Pirin is the active form and binds to NF-κB, whereas the Fe(II) form does not bind to NF-κB. However, the surprising consequence of a single charge perturbation in the functional modulation of NF-κB is not well understood. Here, we use quantum mechanical calculations and microsecond-long molecular dynamics simulations to explore the free-energy landscapes of the Fe(II) and Fe(III) forms of Pirin. We show that the restricted conformational space and electrostatic complementarity of the Fe(III) form of Pirin are crucial for binding and regulation of NF-κB. Our results suggest that a subtle single-electron redox trigger could significantly modulate the conformational dynamics and electrostatics of proteins in subcellular allosteric regulatory processes.

Superradiantly stable non-extremal Reissner–Nordström black holes

The superradiant stability is investigated for non-extremal Reissner-Nordstrom black hole. We use an algebraic method to demonstrate that all non-extremal Reissner-Nordstrom black holes are superradiantly stable against a charged massive scalar perturbation. This improves the results obtained before for non-extremal Reissner-Nordstrom black holes.

Time evolutions of scalar field perturbations in D-dimensional Reissner–Nordström Anti-de Sitter black holes

Reissner-Nordstr\"om Anti-de Sitter (RNAdS) black holes are unstable against the charged scalar field perturbations due to the well-known superradiance phenomenon. We present the time domain analysis of charged scalar field perturbations in the RNAdS black hole background in general dimensions. We show that the instabilities of charged scalar field can be explicitly illustrated from the time profiles of evolving scalar field. By using the Prony method to fit the time evolution data, we confirm the mode that dominates the long time behavior of scalar field is in accordance with the quasinormal mode from the frequency domain analysis. The superradiance origin of the instability can also be demonstrated by comparing the real part of the dominant mode with the superradiant condition of charged scalar field. It is shown that all the unstable modes are superradiant, which is consistent with the analytical result in the frequency domain analysis. Furthermore, we also confirm there exists the rapid exponential growing modes in the RNAdS case, which makes the RNAdS black hole a good test ground to investigate the nonlinear evolution of superradiant instability.

Charged scalar perturbations around a regular magnetic black hole

We study charged scalar perturbations in the background of a regular magnetic black hole. In this case, the charged scalar perturbation does not result in superradiance. By using careful time-domain analysis, we show that the charge of scalar field can change the real part of quasinormal frequency, but has little impact on the imaginary part of quasinormal frequency and the behavior of the late-time tail. Therefore, the regular magnetic black hole may be stable under the perturbations of charged scalar field at the linear level.

The direct-current response of electrically conducting fractures excited by a grounded current source

Hydraulic fracture stimulation of low permeability reservoir rocks is an established and cross–cutting technology for enhancing hydrocarbon production in sedimentary formations and increasing heat exchange in crystalline geothermal systems. Whereas the primary measure of success is the ability to keep the newly generated fractures sufficiently open, long–term reservoir management requires a knowledge of the spatial extent, morphology, and distribution of the fractures — knowledge primarily informed by microseismic and ground deformation monitoring. To minimize the uncertainty associated with interpreting such data, we investigate through numerical simulation the usefulness of direct-current (DC) resistivity data for characterizing subsurface fractures with elevated electrical conductivity by considering a geophysical experiment consisting of a grounded current source deployed in a steel cased borehole. In doing so, the casing efficiently energizes the fractures with steady current. Finite element simulations of this experiment for a horizontal well intersecting a small set of vertical fractures indicate that the fractures manifest electrically in (at least) two ways: (1) a local perturbation in electric potential proximal to the fracture set, with limited farfield expression and (2) an overall reduction in the electric potential along the borehole casing due to enhanced current flow through the fractures into the surrounding formation. The change in casing potential results in a measurable effect that can be observed far from fractures themselves. Under these conditions, our results suggest that farfield, timelapse measurements of DC potentials can be interpreted by simple, linear inversion for a Coulomb charge distribution along the borehole path, including a local charge perturbation due to the fractures. This approach offers an inexpensive method for detecting and monitoring the time-evolution of electrically conducting fractures while ultimately providing an estimate of their effective conductivity — the latter providing an important measure independent of seismic methods on fracture shape, size, and hydraulic connectivity.

Quasinormal modes of extremal black holes

The continued fraction method (also known as Leaver's method) is one of the most effective techniques used to determine the quasinormal modes of a black hole. For extremal black holes, however, the method does not work (since, in such a case, the event horizon is an irregular singular point of the associated wave equation). Fortunately, there exists a modified version of the method, devised by Onozawa et al. [Phys. Rev. D 53, 7033 (1996)], which works for neutral massless fields around an extremal Reissner-Nordstrom black hole. In this paper, we generalize the ideas of Onozawa et al. to charged massless perturbations around an extremal Reissner-Nordstrom black hole and to neutral massless perturbations around an extremal Kerr black hole. Similarities and differences between the results of the original continued fraction method for near extremal black holes and the results of the new continued fraction method for extremal black holes are discussed.

Vibrational, NMR and UV–Visible spectroscopic investigation, VCD and NLO studies on Benzophenone thiosemicarbazone using computational calculations

In order to explore the unbelievable NLO property of prepared Benzophenone thiosemicarbazone (BPTSC), the experimental and theoretical investigation has been made. The theoretical calculations were made using RHF and CAM-B3LYP methods at 6-311++G(d,p) basis set. The title compound contains CS ligand which helps to improve the second harmonic generation (SHG) efficiency. The molecule has been examined in terms of the vibrational, electronic and optical properties. The entire molecular behavior was studied by their fundamental IR and Raman wavenumbers and was compared with the theoretical aspect. The molecular chirality has been studied by performing vibrational circular dichroism (circularly polarized infrared radiation). The Mulliken charge levels of the compound ensure the perturbation of atomic charges according to the ligand. The molecular interaction of frontier orbitals emphasizes the modification of chemical properties of the compound through the reaction path. The enormous amount of NLO activity was induced by the Benzophenone in thiosemicarbazone. The Gibbs free energy was evaluated at different temperature and from which the enhancement of chemical stability was stressed. The VCD spectrum was simulated and the optical dichroism of the compound has been analyzed.

Instability of charged massive scalar fields in bound states around Kerr–Sen black holes

In this paper, we show the instability of a charged massive scalar field in bound states around Kerr–Sen black holes. By matching the near and far region solutions of the radial part in the corresponding Klein–Gordon equation, one can show that the frequency of bound state scalar fields contains an imaginary component which gives rise to an amplification factor for the fields. Hence, the unstable modes for a charged and massive scalar perturbation in Kerr–Sen background can be shown.

Portable nanoporous electrical biosensor for ultrasensitive detection of Troponin-T.

Aim:To demonstrate the design, fabrication and testing of a portable, label-free biosensor for ultrasensitive detection of the cardiac Troponin-T (cTnT) from patient blood.Materials & methods:The biosensor is comprised of a nanoporous membrane integrated on to a microelectrode sensor platform for nanoconfinement effects. Charge perturbations due to antigen binding are recorded as impedance changes using electrochemical impedance spectroscopy.Results:The measured impedance change is used to quantitatively determine the cTnT concentration from the tested sample. We were successful in detecting and quantifying cardiac Troponin-T from a 40-patient cohort. The limit of detection was 0.01 pg/ml.Conclusion:This novel technology has promising preliminary results for rapid and sensitive detection of cTnT.

Charged scalar perturbations around Garfinkle–Horowitz–Strominger black holes

We examine the stability of the Garfinkle–Horowitz–Strominger (GHS) black hole under charged scalar perturbations. Employing the appropriate numerical methods, we show that the GHS black hole is always stable against charged scalar perturbations. This is different from the results obtained in the de Sitter and anti-de Sitter black holes. Furthermore, we argue that in the GHS black hole background there is no amplification of the incident charged scalar wave to cause the superradiance, so that the superradiant instability cannot exist in this spacetime.

Charging of a conducting sphere in a weakly ionized collisional plasma: Temporal dynamics and stationary state

We consider the interaction of a isolated conducting sphere with a collisional weakly ionized plasma in an external field. We assume that the plasma consists of two species of ions neglecting of electrons. We take into account charging of the sphere due to sedimentation of plasma ions on it, the field of the sphere charge and the space charge, as well as recombination and molecular diffusion. The nonstationary problem of interaction of the sphere with the surrounding plasma is solved numerically. The temporal dynamics of the sphere charge and plasma perturbations is analyzed, as well as the properties of the stationary state. It is shown that the duration of transient period is determined by the recombination time and by the reverse conductivity of ions. The temporal dynamics of the sphere charge and plasma perturbations is determined by the intensity of recombination processes relative to the influence of the space charge field and diffusion. The stationary absolute value of the sphere charge increases linearly with the external electric field, decreases with the relative intensity of recombination processes and increases in the presence of substantial diffusion. The scales of the perturbed region in the plasma are determined by the radius of the sphere, the external field, the effect of diffusion, and the relative intensity of recombination processes. In the limiting case of the absence of molecular diffusion and a strong external field, the properties of the stationary state coincide with those obtained earlier as a result of approximate solution.