Excitation Of Vacuum Research Articles

Endovascular Detection of Catheter-Thrombus Contact by Vacuum Excitation.

The objective of this work is to introduce and demonstrate the effectiveness of a novel sensing modality for contact detection between an off-the-shelf aspiration catheter and a thrombus. A custom robotic actuator with a pressure sensor was used to generate an oscillatory vacuum excitation and sense the pressure inside the extracorporeal portion of the catheter. Vacuum pressure profiles and robotic motion data were used to train a support vector machine (SVM) classification model to detect contact between the aspiration catheter tip and a mock thrombus. Validation consisted of benchtop accuracy verification, as well as user study comparison to the current standard of angiographic presentation. Benchtop accuracy of the sensing modality was shown to be 99.67%. The user study demonstrated statistically significant improvement in identifying catheter-thrombus contact compared to the current standard. The odds ratio of successful detection of clot contact was 2.86 (p = 0.03) when using the proposed sensory method compared to without it. The results of this work indicate that the proposed sensing modality can offer intraoperative feedback to interventionalists that can improve their ability to detect contact between the distal tip of a catheter and a thrombus. By offering a relatively low-cost technology that affords off-the-shelf aspiration catheters as clot-detecting sensors, interventionalists can improve the first-pass effect of the mechanical thrombectomy procedure while reducing procedural times and mental burden.

398 Towards Catheter-Clot Engagement Detection Via Classification of Vacuum and Motion Signature During Aspiration Thrombectomy

INTRODUCTION: While acute ischemic stroke caused by large vessel occlusion is effectively treated with aspiration thrombectomy, procedural success depends on the quality of engagement between the catheter tip and the thrombus. Currently, there is no method to identify whether the catheter tip is truly in contact with the clot surface. Poor thrombus engagement can result in failure of recanalization. METHODS: An in vitro arterial occlusion was modeled with Tygon tubing representing the blood vessel and a synthetic thrombus made from TrueClot simulants. A 6Fr microcatheter was controllably inserted into the mock vessel until it contacted the synthetic thrombus. A motorized syringe and pressure sensor were connected proximally to the catheter to precisely control and measure the cyclic vacuum excitation in the catheter. The cyclic vacuum excitation was performed with a stroke of ±0.5 mm at 2 Hz, 4 Hz, and 8 Hz at catheter-clot distances of 150 mm, 20 mm, 10 mm, 5 mm, and in contact on 17 different clot models. Control and sensing data was collected at 1000 Hz frequency. For each catheter-clot distance, 1000 vacuum measurements were collected and pressure traces were saved. The change in the pressure mean per a change in insertion depth of the catheter was used to train a support vector machine (SVM) classifier that confirms clot contact. RESULTS: Using 30% of the clot model samples to train the SVM classifier and the remaining samples for validation, the quality of classification was determined. The accuracy (and F1 score) of clot detection at 2 Hz, 4 Hz, and 8 Hz were 98.31% (95.65%), 100% (100%), and 93.22% (80.00%) respectively. CONCLUSIONS: Accurate detection of catheter-clot contact is feasible via small excitation of the aspiration syringe and concurrent measurement of vacuum pressure.

Quantum Vacuum Excitation of a Quasinormal Mode in an Analog Model of Black Hole Spacetime.

Vacuum quantum fluctuations near horizons are known to yield correlated emission by the Hawking effect. We use a driven-dissipative quantum fluid of microcavity polaritons as an analog model of a quantum field theory on a black-hole spacetime and numerically calculate correlated emission. We show that, in addition to the Hawking effect at the sonic horizon, quantum fluctuations may result in a sizable stationary excitation of a quasinormal mode of the field theory. Observable signatures of the excitation of the quasinormal mode are found in the spatial density fluctuations as well as in the spectrum of Hawking emission. This suggests an intrinsic fluctuation-driven mechanism leading to the quantum excitation of quasinormal modes on black hole spacetimes.

Quantum vacuum excitation of a quasi-normal mode in an analog model of black hole spacetime

Vacuum quantum fluctuations near horizons are known to yield correlated emission by the Hawking effect. In this talk, I will explain how a 1 dimensional flow of microcavity polaritons may be engineered to produce an effective curved spacetime with a black hole horizon. I will present numerical computations of correlated emission on this spacetime and show that, in addition to the Hawking effect at the sonic horizon, quantum fluctuations may result in a sizeable stationary excitation of a quasi-normal mode of the field theory. Observable signatures of the excitation of the quasi-normal mode are found in the spatial density fluctuations as well as in the spectrum of Hawking emission. I will explain how the driven-dissipative dynamics of the polariton fluid are key to observing the quantum excitation of the quasi-normal mode. Nonetheless, this observation suggests a general and intrinsic fluctuation-driven mechanism leading to the quantum excitation of quasi-normal modes on black hole spacetimes.

A precise photometric ratio via laser excitation of the sodium layer – I. One-photon excitation using 342.78 nm light

ABSTRACT The largest uncertainty on measurements of dark energy using type Ia supernovae (SNeIa) is presently due to systematics from photometry; specifically to the relative uncertainty on photometry as a function of wavelength in the optical spectrum. We show that a precise constraint on relative photometry between the visible and near-infrared can be achieved at upcoming survey telescopes, such as at the Vera C. Rubin Observatory, via a laser source tuned to the 342.78 nm vacuum excitation wavelength of neutral sodium atoms. Using a high-power laser, this excitation will produce an artificial star, which we term a ‘laser photometric ratio star’ (LPRS) of de-excitation light in the mesosphere at wavelengths in vacuum of 589.16, 589.76, 818.55, and 819.70 nm, with the sum of the numbers of 589.16 and 589.76 nm photons produced by this process equal to the sum of the numbers of 818.55 and 819.70 nm photons, establishing a precise calibration ratio between, for example, the r and $z$ filters of the LSST camera at the Rubin Observatory. This technique can thus provide a novel mechanism for establishing a spectrophotometric calibration ratio of unprecedented precision for upcoming telescopic observations across astronomy and atmospheric physics; thus greatly improving the performance of upcoming measurements of dark energy parameters using type SNeIa. The second paper of this pair describes an alternative technique to achieve a similar, but brighter, LPRS than the technique described in this paper, by using two lasers near resonances at 589.16 and 819.71 nm, rather than the single 342.78 nm on-resonance laser technique described in this paper.

Review on the physical basis of wave–particle duality: Conceptual connection between quantum mechanics and the Maxwell theory

A well-known mystery in quantum mechanics is wave–particle duality: Is an electron a point mass or a physical wave? What is the physical meaning of its wave function? About a hundred years ago, there was a famous debate between Bohr and Einstein on this topic. Their question is still open today. This paper reviews a new theoretical framework to address this problem. Here, it is hypothesized that both photons and electrons are quantized excitation waves of the vacuum, the physical properties of which can be modeled based on the Maxwell theory. Using the method of Helmholtz decomposition, one can show that the wave function of the particle is associated with an electric vector potential called “ Z”, which plays the role of basic field for the excitation wave. Using this framework, the quantum wave equations can be derived based on a quantization of the Maxwell theory. This work suggests that, the quantum wave function truly represents a physical wave; the wave packet looks like a “particle” only in the macroscopic view. Because the vacuum excitation obeys the principle of all-or-none, the probability of detecting this “particle” is related to the wave function as suggested in the Copenhagen interpretation.

Microscopic quantum generalization of classical Liénard oscillators.

Based on a system-reservoir model and an appropriate choice of nonlinear coupling, we have explored the microscopic quantum generalization of classical Liénard systems. Making use of oscillator coherent states and canonical thermal distributions of the associated c numbers, we have derived the quantum Langevin equation of the reduced system which admits single or multiple limit cycles. It has been shown that detailed balance in the form of the fluctuation-dissipation relation preserves the dynamical stability of the attractors even in the case of vacuum excitation. The quantum versions of Rayleigh, van der Pol, and several other variants of Liénard oscillators are derived as special cases in our theoretical scheme within a mean-field description.

Motion induced by asymmetric excitation of the quantum vacuum

During the last fifty-one years, the effect of excitation of the quantum vacuum field induced by its coupling with a moving object has been systematically studied. Here, we propose and investigate a somewhat inverted setting: an object, initially at rest, whose motion becomes induced by an excitation of the quantum vacuum caused by the object itself. In the present model, this excitation occurs asymmetrically on different sides of the object by a variation in time of one of its characteristic parameters, which couple it with the quantum vacuum field.

Uniformly accelerated point charge along a cusp

A uniformly accelerated point charge which moves neither in a straight line nor in a circle, but in a cusp, is investigated. We find the angular distribution of the Larmor radiation, the constant power, and the intensity in the maximal direction. It is found that the intensity of uniformly accelerated cusp motion scales like non-uniformly accelerated synchrotron radiation. We confirm the exact vacuum excitation spectra of quantized field detectors on the world line.

The global Higgs as a signal for compositeness at the LHC

The radial excitation of the global symmetry-breaking vacuum in composite Higgs models, called the “global Higgs”, has been recently a focus of investigation. In this paper we study the prospects for detecting this composite scalar at the 13 TeV LHC. We compute the global Higgs production rates and estimate the discovery potential of a global Higgs decaying into top quark pairs and into Higgs and electroweak gauge bosons with subsequent hadronic decays. The global Higgs may also decay into fermion resonances such as top partners, providing a new window into compositeness. We show that top partner jets can be effectively unresolved in some regions of the parameter space. Such “boosted top partner” signatures would deserve the development of dedicated substructure analyses.

The excitation of the global symmetry-breaking vacuum in composite Higgs models

We consider scenarios of Higgs compositeness where the Higgs doublet arises as a pseudo-Nambu Goldstone boson. Our focus is the physical scalar ("radial") excitation associated with the global symmetry breaking vacuum, which we call the "global Higgs". For the minimal case of a $SO(5)/SO(4)$ coset, the couplings of the global Higgs to Standard Model (SM) particles are fully determined by group theoretical factors and two decay constants. The global Higgs also couples to the composite resonances of the theory, inducing an interaction with the SM gauge bosons at one-loop. We thoroughly analyze representative fermionic sectors, considering a global Higgs both in the $\bf 5$ and $\bf 14$ representations of $SO(5)$ and taking into account the renormalization group evolution of couplings in the composite sector. We derive the one-loop effective couplings and all decays of the global Higgs, showing that its decay width over mass can range from $ O (10^{-3})$ to $ O(1)$. Because of the multiplicity of the resonances, the coupling of the global Higgs to gluons is sizeable, potentially opening a new window into composite models at the LHC.

Vacuum excitation by sudden appearance and disappearance of a Dirichlet wall in a cavity

Vacuum excitation by time-varying boundary conditions is not only of fundamental importance but also has recently been confirmed in a laboratory experiment. In this paper, we study the vacuum excitation of a scalar field by the instantaneous appearance and disappearance of a both-sided Dirichlet wall in the middle of a 1D cavity, as toy models of bifurcating and merging spacetimes, respectively. It is shown that the energy flux emitted positively diverges on the null lines emanating from the appearance and disappearance events, which is analogous to the result of Anderson and DeWitt. This result suggests that the semiclassical effect prevents the spacetime both from bifurcating and merging. In addition, we argue that the diverging flux in the disappearance case plays an interesting role to compensate for the lowness of ambient energy density after the disappearance, which is lower than the zero-point level.

Response of a mechanical oscillator in an optomechanical cavity driven by a finite-bandwidth squeezed vacuum excitation

In this paper, we theoretically investigate the displacement and momentum fluctuations spectra of the movable mirror in a standard optomechanical system driven by a finite bandwidth squeezed vacuum light accompanying a coherent laser field. Two cases in which the squeezed vacuum is generated by degenerated and non-degenerate parametric oscillators (DPO and NDPO) are considered. We find that for the case of finite bandwidth squeezed vacuum injection, the two spectra exhibit unique features, which strongly differ from those of broadband squeezing excitation. In particular, the spectra exhibit a three-peaked and a four-peaked structure, respectively, for the squeezing injection from DPO and NDPO. Besides, some anomalous characteristics of the spectra such as squeezing-induced pimple, hole burning, and dispersive profile are found to be highly sensitive to the squeezing parameters and the temperature of the mirror. We also evaluate the mean-square fluctuations in position and momentum quadratures of the movable mirror and analyze the influence of the squeezing parameters of the input field on the mechanical squeezing. It will be shown that the parameters of driven squeezed vacuum affects the squeezing. We find the optimal mechanical squeezing is achievable via finite bandwidth squeezed vacuum injection which is affected by the intensity of squeezed vacuum. We also show that the phase of incident squeezed vacuum determines whether position or momentum squeezing occurs. Our proposed scheme not only provides a feasible experimental method to detect and characterize squeezed light by optomechanical systems, but also suggests a way for controllable transfer of squeezing from an optical field to a mechanical oscillator.

Dynamical Schwinger effect: Properties of the e + e − plasma created from vacuum in strong laser fields

We study the dynamical Schwinger effect in the vacuum excitation of the electron-positron plasma under action of a "laser pulse" of the simplest configuration: a linearly polarized, time-dependent and spatially homogeneous electric field. Methodical basis of this investigation is the kinetic equation which is an exact consequence of the basic equations of motion of QED in the considered field model. In the present work we investigate some features of the residual electron-positron plasma and the transient process of its formation.

The Oscillating Universe Theory (To the Unified Field Theory)

This paper represents model of oscillating universe theory. We try to realize model of both electromagnetic waves and spectrum of elementary particles from the unified point of view. Consideration of problems of the gravitational optics and dark matter is developing from the solid crystal model for the vacuum. The vacuum is represented as a three-dimensional crystal lattice matter with a very small lattice period, much less than 10-26 cm. The oscillators are located at the nodes of an infinite lattice. It is shown that an infinite set of equations to describe the coupled oscillations of moving oscillators converges to a system of twelve equations. We have obtained the combined equations for a multicomponent order parameter in the form of the electric and magnetic vacuum polarization, which defines the spectrum and symmetry of normal oscillations in the form of elementary particles. Two order parameters—a polar vector and an axial vector— had to be introduced as electrical and magnetic polarization, correspondingly, in order to describe dynamic properties of vacuum. Vacuum susceptibility has been determined to be equal to the fine structure constant a. Unified interaction constant g for all particles equal to the double charge of Dirac monopole has been found (g = e/a, where e—electron charge). The fundamental vacuum constants are: g, a, parameters of length and parameters of time for electron and nucleon oscillations, correspondingly. Energy of elementary particles has been expressed in terms of the fundamental vacuum parameters, light velocity being equal to . The term mass of particle has been shown to have no independent meaning. Particle energy does have physical sense as wave packet energy related to vacuum excitation. Exact equation for particle movement in the gravitational field has been derived, the equation being applied to any relatively compact object: planet, satellite, electron, proton, photon and neutrino. The situation has been examined according to the cosmological principle when galaxies are distributed around an infinite space. In this case the recession of galaxies is impossible, so the red shift of far galaxies’ radiation has to be interpreted as the blue time shift of atomic spectra; it follows that zero-energy, and consequently electron mass are being increased at the time. Since physical vacuum has existed eternally, vacuum parameters can be either constant, or oscillating with time. It is the time oscillation of the parameters that leads to the growth of electron mass within the last 15 billion years and that is displayed in the red shift; the proton mass being decreased that is displayed in planet radiation.

Excitation of physical vacuum throughp¯pannihilation in selected channels

In this work we discuss the interest of measuring the ratio of $p\overline{p}$ annihilation into kaon and pion pairs near the threshold region, where the $S$ state dominates. It is shown that a good agreement with existing data on the ratio of the yields of charged kaon to pion pairs is obtained taking into account not only quark rearrangement in the incident hadrons, but also vacuum excitations.

New Consideration of Problems of Gravitational Optics and Dark Matter Based on Crystal Model of Vacuum

In presented paper we try to consider problems of the gravitational optics and dark matter developing from the crystal model for the vacuum. How it is follows from consideration it enables to describe both electromagnetic waves and spectrum of elementary particles from the unified point of view. Two order parameters – a polar vector and an axial vector - had to be introduced as electrical and magnetic polarization, correspondingly, in order to describe dynamic properties of vacuum. Vacuum susceptibility has been determined to be equal to the fine structure constant . Unified interaction constant g for all particles equal to the double charge of Dirac monopole has been found (g = e/, where e charge electron). The fundamental vacuum constants are: g, , parameters of length and parameters of ti- me for electron and nucleon oscillations, correspondingly. Energy of elementary particles has been expressed in terms of the fundamental vacuum parameters, light velocity being equal to . The term mass of particle has been shown to have no independent meaning. Particle energy does have physical sense as wave packet energy related to vacuum excitation. Exact equation for particle movement in the gravitational field has been derived, the equation being applied to any relatively compact object: planet, satellite, electron, proton, photon and neutrino. The situation has been examined according to the cosmological principle when galaxies are distributed around an infinite space. In this case the recession of galaxies is impossible, so the red shift of far galaxies’ radiation has to be interpreted as the blue time shift of atomic spectra; it follows that zero-energy, and consequently electron mass are being increased at the time. Since physical vacuum has been existed eternally, vacuum parameters can be either constant, or oscillating with time. It is the time oscillation of the parameters that leads to the growth of electron mass within the last 15 billion years and that is displayed in the red shift; the proton mass being decreased that is displayed in planet radiation.

Resonant mechanism of axion photoproduction in a magnetized electron gas

It was shown that the contribution of diagrams with electron-positron vacuum excitation in a strong magnetic field B ≫ B0 = m2/e = 4.41 × 1013 G in the Compton mechanism of axion production γe → ae at temperatures on the order of the axion mass exceeds the contribution of the “simple” Compton diagram and the contribution of the neutrino production γe → (ν\(\bar \nu \))e to the radiation power by many orders of magnitude. The conclusion is made on the probable axionic nature of the cold hidden mass of the Universe.

Vacuum excitation in shearographic NDT

Materials of composite nature, such as for example carbon fibre skin, sandwiching Nomex core and other honeycomb structures, are increasingly being utilised in the aerospace industry due to the benefits of reduced weight, the ease of formability and good mechanical properties that they offer. Composite materials are difficult to inspect for flaws such as delaminations and disbanding using traditional NOT techniques, however digital shearography is demonstrably well-suited for the purpose and particularly when applying vacuum stressing. The paper reports on developments regarding the challenge of transferring shearographic inspection from the confines of the laboratory to the industrial environment, the development of a portable vacuum chamber which would be placed on the surface to be inspected, and guidelines on the technique's sensitivity or resolution in attempting to detect hidden flaws of differing reduced magnitude. The results indicate that vacuum stressing is particularly desirable when inspecting laminates for disbanding or delaminations because its nature dramatically highlights the flaw, with the added benefit of allowing the detection of relatively small magnitude defects. Notwithstanding the fact that the shearographic method is an optical interferometric technique, an additional optical element, such as the window of a vacuum chamber, interposed between the shearography optics and the surface of the component under test, did not affect the procedure in any manner. This fact provided the confidence to proceed in developing the portable vacuum chamber, in that the current digital shearograph _ > : system's versatility would be conserved by not transforming it to a turnke _ v solution for only composites vacuum testing.

Scattering of vacuum states by dynamic plasmon singularities: generating photons from vacuum

A metallic nanoparticle surrounded by an amplifying medium results in a boundary condition that creates a singularity in the particle's dynamic polarizability at a critical value of the gain. When this boundary condition is time dependent, parametric excitation of the electromagnetic vacuum results in photon emission. Estimates of the vacuum emission from nanostructures embedded in high-gain laser dyes excited by femtosecond lasers predict energies nearly 2 orders of magnitude larger than the spontaneous emission background.