Protein channels of biological membranes are dynamic structures that are subject to equilibrium thermal fluctuations. The most well-known empirical manifestation of such fluctuations is channel gating, i.e., the channel's ability to spontaneously switch between states of different conductance. However, channel gating, which provides functional regulation of channel-facilitated transport in response to voltage, ligands, stress, and other factors, does not exhaust the variety of possible structural fluctuations and their consequences. In this study, we investigate the impact of a fluctuating side chain on the transport properties of the channel. We limit ourselves to the case of a two-state three-dimensional cylindrical channel that, due to fluctuations in the chain conformation, undergoes random transitions between fully open and partially (or completely) blocked states. When transitions are slow, the average flux through the channel is just a weighted sum of the fluxes through the fully open and blocked channel states. Here, we demonstrate that this simple relationship breaks down when the characteristic time of conformational fluctuations becomes comparable to that of solute dynamics in the channel. Using the framework of a continuum diffusion model, we show that the blocking effect of the side chain decreases as the fluctuation rate increases. Importantly, this surprising asymptotic behavior persists independent of the blockage degree and the probability of finding the channel in the blocked state, thus suggesting that the "closed state," obtained in crystallography or other structural methods, may in fact be open for solute transport.

Quantitative remote wound monitoring has the potential to shorten patient recovery time and alleviate the workload of healthcare professionals. In this study, a nitrogen-doped horizontally grown graphene (NHG) antenna sensor with a working frequency of 2.45 GHz was designed for wireless real-time monitoring of wounds. The sensor comprises 32 NHG microtubes (1 mm in diameter), a porous Cu radiation electrode, a polydimethylsiloxane substrate with a cylindrical channel array, and a Cu ground plane. Its novel structure enables body fluid and its temperature and pH value sensing by tracking dual signals, such as resonance frequency and return loss, thereby facilitating the identification of living organisms and real-time quantitative wound assessment. Notably, the NHG microtubes, which penetrate the Cu electrode and PDMS substrate, regulate the radiofrequency radiation field and enhance the monitoring sensitivity. The sensor exhibits a minimum fluid response volume of 25 μL, a temperature detection range of 34-43 °C, a resolution of 0.1 °C, and a response time of 20 s. Furthermore, the NHG antenna sensor reliably evaluated the pH value, volume, and area of the wound using a machine learning algorithm. The system was successfully validated for real-time monitoring of wound healing in mice and has been preliminarily applied to monitor wounds of various sizes and locations in human patients.

Ferrohydrodynamic circulatory flow in a cylindrical end-wall channel

ABSTRACT Three new high‐dimensional MOFs, {[Cd 3 (L) 2 (H 2 O) 4 ]·5.5H 2 O} n ( 1 ), {[Co 2 (L)(H 2 O) 2 (OH)]·(CH 3 CN)} n ( 2 ), {[Mn(H 2 L) 2 ]} n ( 3 ) were constructed using Cd(II)/Co(II)/Mn(II) metal ions and pyridine tricarboxylate ligand 3‐(3,5‐dicarboxyphenyl)‐4‐carboxypyridine (H 3 L) under solvothermal conditions. Based on the diversity of ligand coordination patterns, the complexes show unique structures and properties. Complexes 1 – 2 are new three‐dimensional frameworks based on diverse dinuclear/tetranuclear metal clusters, respectively. Complex 1 contains a one‐dimensional cylindrical channel in its structure, which has good thermal stability. It not only has excellent solid‐state fluorescence properties at room temperature, but also can highly sensitively identify the Cr 2 O 7 2− , CrO 4 2− , and Fe 3+ in aqueous solutions with low detection limits (5.9 × 10 −4 M, 9.9 × 10 −4 M and 3.7 × 10 −4 M). In addition, the fluorescence quenching mechanism of specific ions in aqueous solution was discussed in depth. Complex 3 is a two‐dimensional layered structure with a unique Mn‐O metal oxygen chains. At the same time, the magnetic studies of complexes 2–3 confirmed the existence of antiferromagnetic interactions between adjacent metal ions within the framework.

The temperature distribution field in a cylindrical channel of finite length, which was filled with moving biomass due to the rotation of an induction-heated helix, was analyzed. The outer and inner surfaces of the channel were assumed to be thermally insulated and to meet third-kind boundary conditions on temperature at the entrance and exit of the reactor. To solve the thermal conductivity problem, the desired function was decomposed into a Fourier-Bessel series with respect to the angular and radial variables. Then, an integral Laplace transformation was applied with respect to time. The exact solution was replaced by an approximate solution for practical numerical reasons. A detailed numerical analysis of the temperature field was performed. The analysis showed that the duration of the transition process was inversely proportional to the square of the biomass movement velocity and that temperature oscillation amplitudes in the quasi-stationary regime were weak. However, these oscillations are clearly manifested under space-time resonance conditions, especially when the velocities of helix rotation and rectilinear movement of the biomass are correspondingly selected. It was also determined that a local temperature increase occurs at low velocities of mass movement.

Stochastic fluid variables refer to the various fluid properties such as velocity, temperature, pressure, concentration etc, that exhibit random or unpredictable behavior due to the influence of stochastic factors. Therefore, paper presents the problem of heat and mass transfer for stimulation of non-isothermal flow in cylindrical channel with an assumption of electrically conducting Newtonian fluid. The governing coupled partial differential equations were transformed into a set of non-trivial variable coefficient differential equations in a cylindrical geometry. Using the series solution approach of Frobenius and method of undetermined coefficient, closed-form analytical solutions were obtained for the flow variables. Therefore, graphical results for the flow variables were presented and effectively discussed with the effects of the relevant flow parameters. The results showed as follows: an increase in injection parameter increases both fluid velocity and stochastic fluid velocity; an increase in Grashof number increases both fluid velocity and stochastic fluid velocity; increase in magnetic field parameter decreases the fluid velocity and stochastic fluid velocity; increase in pressure Gradient reduces fluid velocity and stochastic fluid velocity; increase in cooling parameter decreases fluid temperature; increase in injection parameter increases fluid mass concentration but in stochastic mass concentration there were small-scale fluctuations in the surface roughness of the channel walls which makes the trends to be unstable.

Abstract We present a new class of warp bubble geometries that are both interior-flat and segmented into {Gaussian cylinders (interchangeably called ``nacelles''\footnote{In aviation, \textit{nacelle} refers to the streamlined cylindrical housing for an engine such as a jet engine nacelle. In spacecraft, it can also be used to describe the engine pods or propulsion housings.} throughout the paper)}, providing an alternative to the continuous toroidal energy distribution of the Alcubierre model. Using the ADM 3+1 formalism, we derive the extrinsic curvature, York time, momentum densities, and energy density for both the Alcubierre baseline and the {Gaussian cylinder} generalizations with $n = 2, 3, 4$ {cylinders equally spaced azimuthally around the warp bubble}. The interior-flat condition guarantees that observers within the bubble remain synchronized with external clocks, yielding a habitable region of flat spacetime. Unlike the diffuse azimuthal ring of negative energy in the Alcubierre solution, our construction localizes exotic stress-energy into discrete cylindrical channels aligned with the bubble wall. Energy density maps, boost magnitude contours, and three-dimensional isosurfaces demonstrate how these segmented {Gaussian cylinders} maintain a synchronized interior while tuning curvature effects to end-caps. The results suggest that warp bubbles can be engineered with structurally discrete geometries resembling science-fiction starship architectures, where exotic matter localization, end-cap shaping, and interior flatness are tunable engineering parameters consistent with general relativity. These findings extend the ongoing search for physically motivated warp constructs and underscore the value of bridging theoretical warp metrics with engineering-oriented design principles.

Objective. The aim of the work is to study heat and mass transfer processes during He–II boiling as a cryogenic agent on a flat heating surface inside a cylindrical channel at immersion depths comparable to its height. Method. The study is based on the application of thermodynamic analysis methods, natural and computational modeling of processes and objects of cryogenic engineering. Result. A schematic of the experimental cell, as well as the methodology for conducting the experiment and data processing, are presented. Attention is paid to the behavior of the interfacial surface depending on various experimental parameters: pressure above the liquid surface, specific heat load and the height of the liquid column above the heating element. A classification of boiling regimes in a vertical channel depending on the visual nature of the processes at the liquid-vapor interfacial surface is proposed. Dependences of the position of the liquid level in the channel on time are constructed. All series were compared, regularities between the interfacial surface velocity, the temperature difference in the liquid and the immersion depth of the heating element in superfluid helium were revealed. A heat balance for the evaporated liquid was compiled in order to estimate heat losses into free volume. Conclusion . When developing and designing systems using superfluid helium as a cryogenic agent, one can assume the morphology of the interfacial surface and the corresponding operating mode of the system.

In nuclear thermal-hydraulic studies, counter-current flow limitation (CCFL) typically refers to steam rising at a fast rate such that it prevents coolant from draining down within a confined channel. CCFL is a crucial issue in nuclear reactor safety analysis. This study investigates CCFL in debris bed channels using high-resolution interface-capturing simulations. A novel proportional-integral-derivative flow rate controller is developed to efficiently achieve the CCFL conditions. Verification studies confirm that CCFL occurs under the same conditions with or without the controller, demonstrating that PID control ensures accurate prediction. Three debris bed channel geometries were examined: a cylindrical channel, a channel with small obstacles, and a channel with large obstacles. Results show that obstacles significantly impact flow behavior, interfacial shear, wall shear, and pressure gradients required for CCFL. The comparison with experimental data confirmed that simulations incorporating geometric complexities align more closely with experimental CCFL conditions. A pressure gradient correlation was also developed for CCFL prediction.

One of the significant challenges in urbanization and industrialization is the release of harmful reactive contaminants that undergo exothermic chemical reactions into drinking water sources. This challenge is of interest even to the United Nations in ensuring clean water, environments free of hazardous material, and good health. In this article, a mathematical examination of the heat generation due to exothermic chemical reaction in water is conducted on the dissolved oxygen level for aquatic life and the emergence of dangerous bacteria and algae that could trigger water-related diseases. The study compares the temperature rise in a one-step (includes one activation energy profile), two-step (includes two activation energy profiles), and three-step (includes three activation energy profiles) exothermic chemical reactions to observe how the oxygen depletion rate occurs accordingly. The appropriate equations governing the heat and mass transfer within the cylindrical channel are formulated, presented in dimensionless form, and solved numerically using the Runge-Kutta Fehlberg method in conjunction with the Shooting technique. The results indicate that the oxygen depletion in a one-step exothermic chemical reaction is less than in the two-step reaction and is highest in the three-step condition, as the temperature increase strength is observed from one-step to three-step situation. Moreover, the results show that the temperature intensity becomes stronger as the reaction mechanism steps increase from one to three.

Abstract To develop a new ion-beam control technique, we examined the guiding effect of highly charged ions using a glass channel. A 20 keV Ar8+ ion beam was injected into a biconvex cylindrical glass channel (BC-CGC), comprising two cylindrical convex lenses facing each other with a 1 mm gap. Subsequently, the time evolution of the charge state, kinetic energy, deflection angle and count rate of the transmitted ions was evaluated using a two-dimensional position-sensitive detector. When a pulsed ion beam was injected into the BC-CGC at a 3° tilt relative to the beam axis, mean charge state of the transmitted ions decreased by less than one. However, the kinetic energy remained at its initial value and the absolute deflection angle increased exponentially with a time constant of 8.0 × 102 s. In another experiment using a direct current beam with a fluency rate 11 times greater than that of the pulsed beam, the absolute deflection angle of the transmitted ions exhibited a similar exponential increase, with a time constant of 6.5 × 102 s. A comparable exponential time dependence was observed for the count rate of the transmitted ions but with a shorter time constant of 37 s.

Laser-plasma acceleration is considered as a modern method of accelerating bunches using a wakefield excited by a laser pulse. This paper demonstrates the use of a longitudinally inhomogeneous increasing plasma density gradient in a conical channel to increase of the energy of a self-injected bunch. Comparison of a conical channels with homogeneous and inhomogeneous plasma and also conical and cylindrical homogeneous channels, shows a clear advantage of an inhomogeneous conical channel. The longitudinally inhomogeneous plasma helps to maintain the self-injected bunch in the wakefield acceleration phase and increases the accelerating gradient. The conical geometry prevents laser pulse expanding, and compress it. The combined effect was shown: the inhomogeneous plasma use, the effect of a conical geometry led to significant increasing the accelerating gradient and longitudinal momentum of the bunch.

The effect of initial temperature on the thermal performance of silica aerogel/copper oxide/pcm nanostructure in a cylindrical channel using molecular dynamics simulation

High-intensity focused ultrasound (HIFU) is an emerging non-invasive treatment for various pathologies, including in the field of vascular medicine. Clinical studies have demonstrated its efficacy for vascular occlusion through thermal effects. An interesting yet early-stage alternative is mechanical HIFU, where occlusion is achieved by cavitation initiated by the injection of microbubble contrast agents. Our study aims to demonstrate the feasibility of an innovative ultrasound-guided mechanical HIFU device for non-invasive in-vivo vein occlusion by cavitation without microbubble contrast agents. A four piezoelectric ceramic device was developed and acoustically characterized. Erosion efficiency by cavitation was assessed on agar phantom models with cylindrical channels created to mimic veins. A preclinical feasibility demonstration was carried out in-vivo on a sheep model, targeting a collateral saphenous vein in the hind limb. Vein occlusion was investigated using ultrasound imaging during a 7-day follow-up and at the cellular level by histological analysis. A maximum negative pressure of -23 MPa was measured at the focal point of dimension 1.27 mm3 at -6 dB . In agar phantom models, a centrally applied HIFU treatment was sufficient to erode small veins, while an application at multiple points was needed for larger veins. In vivo, cavitation was triggered in a small-diameter vein, causing occlusion and preventing blood flow. Histology confirmed vein wall damage and occlusion. Vein occlusion was successfully achieved in-vivo by cavitation using mechanical HIFU without microbubble contrast agents. This approach holds real potential for the non-invasive treatment of varicose veins, without the limitations of current techniques.

Numerical modeling of the local flow structure and mixing process during injection of a gas-droplet wall jet into a turbulent heated air flow has been performed. The numerical solution is based on a system of axisymmetric Reynolds-averaged Navier–Stokes equations (RANS) taking into account the two-phase character of the flow. To describe the dynamics and heat and mass transfer in the dispersed phase, the Euler two-fluid approach is applied. A significant effect of the liquid mass concentration on the distribution of parameters over the channel cross section and thermal efficiency is shown. An increase in thermal efficiency reaches 30 % in the initial part of the channel and 200 % in its end part in comparison with a single-phase wall air jet.

Surgical prosthetic valve labelling is misleading, as labelled diameters (LDs) are currently always larger than inlet orifice diameter (IOD), while the outlet orifice diameter (OOD) is unknown. The IOD, OOD, and height of the flow channel determine its conical shape. The instructions for use (IFUs) do not list all essential metrics. This study reports a comprehensive overview of all relevant aortic stented tissue prosthetic valve metrics. We measured the OOD of these valves with an optical method. Height was measured using a calliper. The conicity angle of the flow channel was calculated. We hunted for IFU on the internet and in packaging boxes. Eight valve models of 4 manufacturers were included. In all but 2 models, the OODs were smaller (89%, range 83%-95%) than their IODs, which depicts a converging shape of the flow channel. In 1 model (Avalus) OOD equals IOD, implicating a cylindrical flow channel; and 1 model (Crown) has a diverging shape. The proportion of OOD in relation to IOD seemed to be consistent among the different sizes within the same model type. Information on metrics for surgical aortic tissue valves is incomplete, scarce, and confusing. This article shows a comprehensive overview of valve metrics, which makes it possible to compare different aortic valve models and sizes. Flow channel shape turned out to be different amongst models. The smallest flow channel diameter is most often the OOD. Since LD should reflect the IOD, one must be aware of all relevant metrics.

The stability of the mixing layer in a cylindrical cell between two counter-rotating vortex flows created by electromagnetic forces is investigated numerically. The flow is described during the development of instability. The resulting Kelvin–Helmholtz instability becomes a source of small disturbances and leads to turbulent mixing of the liquid. The second and third modes of flow make the greatest contribution to the development of disturbances.

The liquid metal velocities and the processes of formation of the reversal flow in a hollow cylindrical channel and a cylindrical channel with an insert in different flow modes are compared. Velocity profiles and pressure drop–flow rate characteristic are obtained. It is shown that, at the same electromagnetic force, the metal velocity and flow rate in the channel with an insert are higher than in the cylindrical channel due to a decrease in the contribution of the reversal flow.

The processes of reflection and diffraction of a pressure wave in a cylindrical channel filled with a bubbly liquid are considered in the presence of an abrupt decrease in the channel diameter. The case is considered when the gas phase of the bubbly liquid is an explosive gas mixture. The main purpose of the work is numerical study of the dynamics of detonation waves in a bubbly liquid with an abrupt decrease in the diameter of a cylindrical channel. To numerically analyze the evolution of waves in a cylindrical channel filled with a bubbly liquid, a system of equations in Lagrangian variables was used, where the Eulerian coordinates at the initial moment of time are taken as Lagrangian variables. An acetylene-oxygen stoichiometric mixture was used as the gas phase for calculations. As a liquid phase, a water–glycerin solution with a mass fraction of 0.5 glycerin was used. It is shown that when high-pressure waves pass through cylindrical channels with an abrupt decrease in diameter containing a bubbly liquid with a combustible gas, both continuous propagation of detonation and attenuation of detonation are possible; and the transition from one detonation mode to another depends not only on the transverse dimensions of the narrow part of the channel, but also on the volume content of bubbles. It has been established that when high-pressure waves pass through cylindrical channels with an abrupt decrease in diameter containing a bubbly liquid with a combustible gas, detonation can be caused by the following reasons: collision of an incident wave with rigid walls in the area of channel diameter reduction; as a result of interference of waves during propagation from a wide to a narrow part of the channel. An analysis of the dynamicsof detonation wave propagation shows that with a low volume gas content, detonation is formed only when high-pressure waves pass into a narrow part of the channel in the direction of the incident wave movement due to wave interference.

The phase behavior of a quasi-one-dimensional fluid of hard spheres is studied in hard cylindrical and rectangular straight channels using the transfer operator method. The radius of the channel (R) is chosen such that only first-neighbor interactions are present, which allows only fluidlike and zigzag solidlike structures to form. It is managed to show that the fluid-solid structural change occurs approximately at ρ=1/〈σ_{∥}〉, where ρ is the one-dimensional density and 〈σ_{||}〉 is the average of the longitudinal contact distance in the case of uniform particle distribution. At this density, the pressure of positionally disordered structure diverges, but the pressure ratio (P/P_{T}), where P is the pressure of the system and P_{T} is the pressure of an effective one-dimensional hard rod fluid, exhibits a peak. At the close packing, while the positional fluctuation (〈Δr^{2}〉) vanishes with P^{β[over ̃]}, where β[over ̃]=-2 for any R and cross section, P/P_{T} (we call it α[over ̃]) goes to 2 in the rectangular and 2.5 in the cylindrical channel. The most striking difference can be observed in the transversal position correlation length (ξ). It exhibits exp(ΔP) dependence in the rectangular channel with Δ being the extra length necessary to create a defect. However, ξ goes with P^{γ[over ̃]} in the cylindrical channel, where γ[over ̃]=1. Interestingly, the cylindrically confined hard spheres obey the sum rules α[over ̃]+β[over ̃]=1/2 and β[over ̃]+γ[over ̃]=-1 for any R.