Capillary Axis Research Articles

Theory of particle beams transport over curved plasma-discharge capillaries

We present a new approach that demonstrates the deflection and guiding of relativistic electron beams over curved paths by means of the magnetic field generated in a plasma-discharge capillary. The active bending plasma (ABP) represents a promising solution that has been recently demonstrated with a proof of principle experiment. An ABP device consists of a curved capillary where large discharges (of the order of kA) are propagated in a plasma channel. Unlike conventional bending magnets, in which the field is constant over the bending plane, in the ABP, the azimuthal magnetic field generated by the discharge grows with the distance from the capillary axis. This features makes the device less affected by the beam chromatic dispersion so that it can be used to efficiently guide particle beams with non-negligible energy spreads. The study we present in the following aims to provide a theoretical basis of the main ABP features by presenting an analytical description of a single-particle motion and rms beam dynamics. The retrieved relationships are verified by means of numerical simulations and provide the theoretical matrix formalism needed to completely characterize such a new transport device. Published by the American Physical Society 2024

Study on transport process of 16 keV C<sup>– </sup>ions in tapered glass capillary: Role of capillary tilt angles

<sec>The tapered glass capillaries have been widely used in physics, biology, materials. The features of ions transmitted through the insulating tapered glass capillary manifest themselves mainly in the interaction between positive ions and tapered glass capillary, However, the transmission process of negative ions in tapered glass capillary has been studied scarcely so far.</sec><sec>In the present study, we measure the properties of 16 keV C<sup>–</sup> ions transmitted through the tapered glass capillary, such as the two-dimensional spectral distribution, the relative transmission rate, the centroid angle, the charge state purity and the full width at half maximum of the transmitted particles. As the tapered glass capillary tilt angle is equal to 0°, the transmitted particles are composed of three components, i.e. the core, the C<sup>–</sup> of halo and the C<sup>0</sup> of halo. As the tilt angle is 1°, the transmitted particles are composed of two components, i.e. C<sup>–</sup> and C<sup>0</sup>. As the tilt angle is >1°, there is no core region, the transmitted particles are composed of two components, i.e. C<sup>–</sup> and C<sup>0</sup>. No matter how the tilt angle changes, the centroid angles of core are always along the direction of the incident ions, independent of the tilt angels. And the centroid angles of transmitted C<sup>–</sup> and C<sup>0</sup> are always along the direction of the capillary axis. The transmission processes of 16 keV C<sup>–</sup> ions in tapered glass capillary with different tilting angles are analyzed qualitatively. When the tilting angle is small (0°–1°), the C<sup>–</sup> ions are directly traveling straight through the back cone hole of tapered glass capillary, which are mainly composed of C<sup>–</sup> ions. When the tilt angle is large (>1°), the C<sup>–</sup> ions cannot directly travel straight through the back cone hole of the tapered glass capillary, and the core region does not appear. Due to the guiding effect of the negative charges deposited on inner wall of tapered glass capillary, the transmitted C<sup>–</sup> ions are located around the direction of the capillary axis. The tapered glass capillary has a focusing effect on the incident ions. This experiment covers the lack of the studies of low-energy negative ions transmitted through tapered capillary and helps to strengthen the understanding of the transmission process of low-energy ions transmitted through tapered capillary.</sec>

Guiding as a General Consequence of the Charged Particle Interaction with the Inner Surface of an Insulator Capillary—Guiding of 1 MeV Proton Microbeam through Polytetrafluoroethylene Macrocapillary

The transmission of energetic, 1 MeV proton microbeam through a single, cylindrical shaped, macrometer-sized polytetrafluoroethylene capillary was studied experimentally. The capillary axis was tilted with respect to the axis of the incident ion beam. The tilting, the aspect ratio of the capillary and the small beam divergence disabled the geometrical transmission of the beam through the target. The intensity, energy, deflection and charge state of the transmitted beam were investigated. We found that the pure guided transmission of a MeV/amu energy ion beam is observable. We clearly identified three completely different stages during the guiding process according to the measured energy distribution of transmitted particles. At the beginning the transmission intensity was low and only inelastic contributions with energy lower than 1 MeV were found in the spectrum. Later, in the second stage, the elastic peak appeared and became more and more significant. Finally, when the stable transmission evolved, only the elastic peak was present and the inelastic area was totally absent as a direct consequence of the ion guiding and as a result of the charged particle interaction with a charged inner surface of the insulator capillary.

Advanced optical imaging reveals preferred spatial orientation of podocyte processes along the axis of glomerular capillaries

Mammalian kidneys filter enormous volumes of water and small solutes, a filtration driven by the hydrostatic pressure in glomerular capillaries, which is considerably higher than in most other tissues. Interdigitating cellular processes of podocytes form the slits for fluid filtration connected by the membrane-like slit diaphragm cell junction containing a mechanosensitive ion channel complex and allow filtration while counteracting hydrostatic pressure. Several previous publications speculated that podocyte processes may display a preferable orientation on glomerular capillaries instead of a random distribution. However, for decades, the controversy over spatially oriented filtration slits could not be resolved due to technical limitations of imaging technologies. Here, we used advanced high-resolution, three-dimensional microscopy with high data throughput to assess spatial orientation of podocyte processes and filtration slits quantitatively. Filtration-slit-generating secondary processes preferentially align along the capillaries' longitudinal axis while primary processes are preferably perpendicular to the longitudinal direction. This preferential orientation required maturation in development of the mice but was lost in mice with kidney disease due to treatment with nephrotoxic serum or with underlying heterologous mutations in the podocyte foot process protein podocin. Thus, the observation that podocytes maintain a preferred spatial orientation of their processes on glomerular capillaries goes well in line with the role of podocyte foot processes as mechanical buttresses to counteract mechanical forces resulting from pressurized capillaries. Future studies are needed to establish how podocytes establish and maintain their orientation and why orientation is lost under pathological conditions.

ДИНАМИКА И КИНЕМАТИКА ДВИЖЕНИЯ МЕНИСКА ЖИДКОСТИ В КАПИЛЛЯРЕ

The role of capillary pressure as a factor determining the dynamics and kinematics of the capillary flow is considered. The observed axial flow is considered as a consequence of the radial flow of the fluid bordering the surface of the meniscus. It is shown that the radial flow is due to the gradient of the superficial tension of the meniscus caused by the deformation of the meniscus surface by the forces of fluid adhesion to the capillary wall. An estimate of current velocities is given. Under typical conditions, the velocity of the radial flow is by a factor of ten greater than the flow velocity along the capillary axis when the volume velocities calculated from the values of the tension gradient and the capillary pressure, respectively, are equal. It is concluded that the observed movement of the meniscus is caused by the flow of fluid on the surface of the capillary, in which the axial component of the flow rate on the capillary wall is zero. This eliminates the contradiction between the apparent movement of the meniscus and the equation of the axial flow of fluid in the capillary, according to which the speed on the wall should be zero

Mechanical properties and chemical stability of alginate-based anisotropic capillary hydrogels

Anisotropic capillary hydrogels are formed by ionotropic gel formation of an aqueous sodium alginate solution during unidirectional diffusion and complexation with divalent cations. The type of cation used for gel formation dictates the size of the resulting capillary structure which might facilitate applications as biomaterial scaffolds in tissue engineering and regenerative medicine. Until now, such capillary hydrogel structures have not been characterized regarding their mechanical properties, and we hypothesise that both, the macroscopic capillary structure and the concentration of a chemical crosslinking agent, influence the mechanical properties and the stability of the hydrogels against degradation and dissolution in physiological environment. We prepared anisotropic gels with capillary sizes ranging between 12 and 100 μm using electrolyte solutions containing Ba2+, Sr2+, Zn2+ or Ni2+ cations. They were chemically crosslinked with hexamethylene diisocyanate in concentrations varying between 1 and 100 mmol L−1. Hydrogel properties were determined by swelling experiments, oscillatory rheometry and microindentation analysis and monitored during incubation in phosphate-buffered solution at 37 °C for up to three months. We found, that the mechanical strength generally decreases with increasing capillary diameter. The higher the concentration of the crosslinking agent, the higher is the mechanical strength. The resistance of the alginate hydrogels against degradation is positively correlated with the concentration of the crosslinking agent. Furthermore, microindentation experiments revealed a microscopic anisotropy of the mechanical properties resulting from a perpendicular orientation of the polymer fibres relative to the capillary axis.

Double-twisted nematic director configurations in cylindrical capillaries with a photocontrollable angle of twist.

The orientational configurations of thermotropic nematic liquid crystal in cylindrical capillaries with nondegenerated planar surface anchoring are investigated. The boundary conditions were determined by a photoaligning coating on the inner wall of the capillary treated with a linearly polarized UV light while rotating the capillary around its long axis, thus providing the easy alignment axis perpendicular to the polarization direction of illuminating light. By changing the angle between the incident light polarization and the capillary axis, this procedure allows us to realize axially symmetric twisted structure with any angle of twist, ranging from a trivial axial alignment with zero twist (when the UV polarization is perpendicular to the capillary axis) to the 180^{∘}-twisted configuration (when the UV polarization is along the capillary). These two extreme configurations together with an intermediate configuration induced by UV light polarized at an angle of 45^{∘} to the capillary axis were produced and their director profiles were studied using polarizing microscopy techniques. UV light intensity and polarization distribution over inner capillary surface covered with photoaligning layer were analyzed using optical ray tracing calculations. An analytical model of the observed configurations of the liquid crystal director field is proposed, which takes into account the finite anchoring on the capillary surface. By comparing the theoretically calculated and experimentally estimated director profiles, the liquid crystal anchoring energy on the photoaligned capillary surface was estimated.

On the mechanisms of the influence of preliminary ionization on the plasma dynamics of nanosecond capillary discharges and the properties of discharge-based EUV lasers

In this paper, we present the results of numerical investigations into the influence of preionization on the properties of extreme ultraviolet (EUV) lasers based on nanosecond capillary discharges. Prior to application of the main current pulse, gas inside the capillary is usually preionized by a separate current pulse with longer duration and lower amplitude, which creates plasma with minimal density on the capillary axis and maximal at the capillary wall. Magnetohydrodynamic simulations were performed for a range of prepulse parameters that defined different degrees of inhomogeneity of this initial profile. It was found that the plasma density distribution at the start of the main current pulse affects the cylindrical shock wave that takes place during the compression stage of a capillary discharge: A lower degree of radial inhomogeneity results in a steeper front of the shock wave. It is further shown that a steeper wave front results in a more concave electron density profile moments before the shock wave collapses on the capillary axis, when the EUV laser pulse presumably takes place, which may lead to a decrease in the rate of refraction losses. The proposed interpretation of the obtained numerical results correlates well with the available experimental data on the dependence of EUV laser pulse intensity and duration on the preliminary pulse amplitude.

Synthesis of human amyloid restricted to liver results in an Alzheimer disease-like neurodegenerative phenotype.

Several lines of study suggest that peripheral metabolism of amyloid beta (Aß) is associated with risk for Alzheimer disease (AD). In blood, greater than 90% of Aß is complexed as an apolipoprotein, raising the possibility of a lipoprotein-mediated axis for AD risk. In this study, we report that genetic modification of C57BL/6J mice engineered to synthesise human Aß only in liver (hepatocyte-specific human amyloid (HSHA) strain) has marked neurodegeneration concomitant with capillary dysfunction, parenchymal extravasation of lipoprotein-Aß, and neurovascular inflammation. Moreover, the HSHA mice showed impaired performance in the passive avoidance test, suggesting impairment in hippocampal-dependent learning. Transmission electron microscopy shows marked neurovascular disruption in HSHA mice. This study provides causal evidence of a lipoprotein-Aß /capillary axis for onset and progression of a neurodegenerative process.

Numerical simulation of the electric field induced in a contactless dielectrophoretic quadrupole cell separator

PurposeThis study aims to propose a contactless and continuous dielectrophoretic cell-separation device using quadrupole electric field. To examine the separation performance, numerical simulations of the electric field in the cross-section of the glass capillary installed in the center of the quadrupole electrode were conducted.Design/methodology/approachTo estimate the magnitude of the dielectrophoretic force induced on cells, electrostatic analysis was performed by using a boundary-fitted coordinate system.Distribution of the electric field and gradient of the electric field square in the cross-section of the glass capillary were simulated for various ratios of radii of the glass capillary to the electrode rod.FindingsThe distribution of the electric field was found to have a cone-like profile about the center axis of the glass capillary with maximum at the internal surface of the glass capillary. The magnitude of the gradient of electric field square had similar distribution as that of the electric field, but had steeper slope near the internal surface of the glass capillary. The optimal values of the ratio of radii and the applied voltage were also estimated to achieve the local electric field strength suitable for cell separation.Originality/valueOne major advantage of the proposed device is simple and low fabrication cost, in addition to its contactless structure free from cell damage. Derived knowledge is instructive in achieving high-throughput cell separation without the use of devices of complex structure.

Recovering the appearance of the capillary blood column from under-sampled flow data.

The regular spacing of cells in capillary flow results in spurious cell trajectories if the sampling rate is too low. This makes it difficult to identify cells, even if the velocity is known. Here, we demonstrate a software method to overcome this problem and validate it using high frame rate data with known velocity, which is downsampled to produce aliasing. The method assumes high spatial sampling, constant velocity over short epochs, and an incompressible blood column. Data in successive frames are shifted along the capillary tube axis according to the flow velocity, faithfully rendering cells and plasma. The velocity estimate, required as input to this procedure, can be obtained from either a) the blind optimization of a simple heuristic, or b) a recently proposed velocimetry algorithm, which appears to extend the aliasing limit.

Bidirectional tuning of whispering gallery modes in a silica microbubble infiltrated with magnetic fluids.

A bidirectional tuning mechanism of whispering gallery modes (WGMs) in a capillary-based microbubble microresonator infiltrated with magnetic fluids (MFs) is investigated. Owing to distinct RI responses of MFs dependent on the applied magnetic field direction with respect to the capillary axis, the RI of MFs shows different variation trends when an external magnetic field is parallel or perpendicular to the capillary axis. Experimental results indicate that WGM resonance dips exhibit wavelength shift in inverse directions for the above two cases, which is in accordance with our theoretical analysis on different refractive variation behaviors of MFs. As the applied magnetic field is perpendicular or parallel to the capillary axis, the WGM resonance wavelength tuning sensitivities tend to be $ - {15.01}\;{\rm pm/mT}$-15.01pm/mT and 6.3 pm/mT, respectively. Our proposed WGM tuning scheme has several desirable advantages, including bidirectional tunability, high Q-factor, ease of fabrication, and good compatibility with functional materials, making it a promising candidate in the field of magnetic field vector sensing and magnetically manipulated micro-optic devices.

Two-dimensional director configurations in a nematic-filled cylindrical capillary with the hybrid director alignment on its surface

ABSTRACTWe analytically calculate two-dimensional equilibrium configurations of the nematic liquid crystal (NLC) director in a right cylindrical capillary with the hybrid director alignment on its inner surface. A part of this surface is treated to impose the strong homeotropic alignment, while on the remaining part the strong circular alignment, perpendicular to the capillary axis, is imposed. Owing to the system homogeneity along the capillary axis, a disclination line emerges in the bulk of the NLC, which runs parallel to the axis. It is shown that there exist either one or two equilibrium locations of the disclination line depending on the ratio of capillary surface parts with homeotropic and circular alignment. The technique that allows to obtain an analytical expression for the system free energy as a function of a disclination line location is presented. It considerably simplifies calculations and can be used while solving a variety of problems in which a defect location is sought.

Anomalous anisotropic transport of scalars in dilute ferrofluids under uniform rotating magnetic fields – Mixing time measurements and ferrohydrodynamic simulations

This study reports experimental observations and numerical simulations on the transport of scalars in ferrofluids under rotating magnetic fields (RMF). Mass transport experiments were conducted in a T-mixer capillary with RMF rotational axis parallel to capillary central axis. Significant mass transport enhancement was measured in the transverse direction as RMF frequency and/or magnetic nanoparticles concentration increased. RMF directional control of mass flux enhancement was anisotropic as molecular diffusion was the only transport mechanism parallel to the capillary axis. The significance of ferrofluid advection (spin-up flow) as mass transport enhancement was examined in light of the advection-diffusion transport and experimental results. Hence, the ferrohydrodynamic equations (FHD) of motion were solved for the lower spin viscosity limit [based on Rosensweig’s interpretation of micro-eddies diffusion length scale], and upper limit as reported from earlier spin-up flow studies. FHD simulations predicted lower magnitudes of the linear azimuthal velocities with decreasingly trends as spin viscosity increased. These findings were in disagreement with previously reported ferrofluid flows calculated on the basis of spin diffusion theory. To clarify the inconsistency’s origin and confirm reliability of numerical simulations, the spin field and asymmetric stresses were analyzed to conclude that the small length scale of the capillary could not accredit the role of spin-up flow effects via azimuthal velocities for the improved mixing observations. Mixing time measurements and analysis of the advection-diffusion equation pointed toward lack of current FHD theory to resolve scalar transport due to the nanoparticle-scale secondary circumferential micro-convective flows. A pragmatic approach was therefore proposed to estimate from mixing time measurements the anomalous anisotropic effective diffusion coefficients induced by rotating nanoparticles, and to correlate them to RMF frequency and/or nanoparticles concentration.

Temporal evolution of the energy spectrum of proton microbeam guided through an insulating macrocapillary

We present theoretical investigation of the temporal evolution of the energy spectrum of ions passing through an insulating capillary. In our simulation we used 1 MeV proton microbeam, and a single, cylindrical shaped polytetrafluoroethylene (PTFE) macrocapillary. In order to prevent the simple geometrical transmission the beam axis was tilted with 1° compared to the capillary axis. According to our simulations, we found that the beam first hit the inner wall of the capillary and build a positive charge patch at a well localized place of the inner capillary surface. As a result, a repulsive electric field is generated for protons enter later into the capillary and a collision-less transmission occurs, which is called ion guiding. We show that our simulated energy spectra are in good agreement with our previous experimental findings.

Optimisation of secondary ion transport in ambient pressure MeV SIMS

Ambient Pressure MeV SIMS (AP MeV SIMS) is a special application of MeV SIMS technique for molecular detection and imaging under ambient conditions. There are several advantages of using ambient over non-ambient techniques such as minimising or completely avoiding sample preparation that can contribute to the reducing of costs and shortening of analysis. Moreover, by performing analysis in ambient conditions negative vacuum influence on samples will be avoided. The emergence of ambient mass spectrometry techniques over the past decade has been enormous with a broad range of applications such as food quality, environmental analysis and life sciences [1,2]. On the other hand, the disadvantage of ambient pressure mass spectrometry techniques is the influence of the ambient background which can suppress the signal from the target. In AP MeV SIMS, molecular species present in ambient surrounding of the sampling site will also be ionised by ion beams hence secondary ions originating from the sample have to be transported in the most efficient manner from the site of interaction of ion beams and target into the mass spectrometer capillary and, finally, into the mass spectrometer [3]. In this work, we present the optimisation of the mass spectrometer capillary temperature, distances of mass spectrometer and sheath gas, in our case helium, with respect to the beam axis and angle of the helium flow capillary with respect to the sample.

Generation of Noble and Refractory Metals Plasma Jets by Electrothermal Discharge for Surface Deposition Applications

Arc-dominated capillary discharges generate high-density plasmas from the ablation of the material of the inner lining sleeve, where ablation is determined by the radiant energy transport in such electrothermal (ET) plasma devices. Properties of sleeve material are an important factor on the generated plasma in ET devices. The 1-D time-dependent NC State University ET plasma code ETFLOW provides simulation of the capillary discharge and predicts the plasma parameters along the capillary axis. Of interest are the plasma parameters at the exit of the capillary which include temperature, pressure, velocity, heat flux and total ablated mass ejected from the source. The experimental discharge current was used in the code, and the plasma parameters at the source exit were calculated. Six materials were tested, namely, titanium, chromium, copper, silver, platinum, and gold. The code results show that the plasma temperature is between 2.4 and 2.57 eV for all tested materials. The lower heat of sublimation of gold and silver leads to increase the total ablated mass, density, electrical conductivity, and the exit pressure combined with reduction of the plasma bulk velocity. The gold has the highest ablated mass while titanium has the lowest values. The total ablated mass of copper material is about 168 mg, which is in a good agreement with previous experimental results.

Electron transmission through a steel capillary

Abstract The transmission of low-energy electrons through a macroscopic steel capillary has been investigated both experimentally and theoretically. The length of the steel capillary was L = 19.5 mm and the inner diameter was d = 0.9 mm. The kinetic energy distribution of electrons transmitted through the steel capillary was recorded for a tilt angle of ψ = 2.6 ° of the incident electron beam with respect to the capillary axis. Accompanying simulations based on classical transport theory reproduce the experimental data to a high degree of agreement. Transmission for other tilt angles has also been simulated to investigate the influence of the tilt angle on the guiding efficiency.

Experimental and theoritical research on the dynamical transmission of 30 keV H+ ions through polycarbonate nanocapillaries

The ions with different incident energies transmitting through insulating nanocapillaries are studied in various configurations. For the low energy ions transmitting through nanocapillaries, Stolterfoht et al.[2002 Phys. Rev. Lett. 88 133201] have observed the guiding effect. Subsequent studies revealed that the self-organizing charge patches on the capillary wall inhibit charge exchange and the ions are transmitted along the capillary axis direction. The high energies of ions transmitting through nanocapillaries are measured, the main transmission mechanism is multiple random inelastic collisions below the surface, and the charge patches will not affect the transmitted ions trajectories. The transmission features of the intermediate energy ions are different from those of the low and high energy ions. The ion beams with intermediate energies have many applications, so it is necessary to understand the transmission features of the intermediate energy ions though nanocapillaries. Recent studies have focused on the transmission of the intermediate energies ions through the nanocapillaries. In the present work, we investigate thie transmission features, such as the two-dimensional transmitted angular distributions, the charge states and position distributions, and the evolution of the relative transmission rate and the charge purity of 30 keV H+ transmitting through nanocapillaries in a polycarbonate membrane at the angles of-1 and-2. The experimental data clearly show that the transmitted H+ ions consist of the transmitted scattering H+ ions, which are located around the direction of the incident beam, and the transmitted guiding H+ ions, which are located around the direction of the capillary axis. With the charges depositing in the capillary, the proportion of the transmitted scattering H+ ions increases and the proportion of the transmitted guiding H+ ion decreases, which directly demonstrates the dynamical evolution of the scattering ions and the guiding ions. To understand the competition between the transmitted scattering ions and the transmitted guiding ions and the physical picture of the intermediate energy ions transmitting through the insulating nanocapillaries, the trajectories of the H+ ions in the capillary and the potential distribution and electric field intensity distribution in the capillary are numerically simulated. The results show that the potential distributions and electric field intensitiesy are different for H+ ions transmitting through nanocapillaries at various tilt angles, and the simulation results are in good agreement with the experimental data. The experimental and simulation results give us a further insight into the mechanisms of guiding and scattering in intermediate energy ions transmitting through nanocapillaries.

Guiding of charged particle beams in curved capillary-discharge waveguides

A new method able to transport charged particle beams along a curved path is presented. It is based on curved capillary-discharge waveguides where the induced azimuthal magnetic field is used to focus the beam and, at the same time, keep it close to the capillary axis. We show that such a solution is highly tunable, it allows to develop compact structures providing large deflecting angles and, unlike conventional solutions based on bending magnets, preserves the beam longitudinal phase space. Such a feature, in particular, is very promising when dealing with ultra-short bunches for which non-trivial manipulations on the longitudinal phase spaces are usually required when employing conventional deflecting devices.