Thin Gap Research Articles

Application of thin gap rheometry for high shear rate viscosity measurement in monoclonal antibody formulations

The key highlight of this work was to develop a thin gap methodology on a mechanical rheometer for characterizing high concentration monoclonal antibody formulations. This work was done from applied formulation perspective to provide guidance on an additional measurement protocol with the objective of further reducing sample volume requirement for biopharmaceutical formulation rheology measurements and provide viscosity data over a wide shear rate range. This is especially relevant for early stage discovery where there are sample volume limitations. This developed methodology in addition to an understanding of the diffusion interaction parameter was then in turn utilized to elucidate the effect of surfactants and excipients on the high shear rate viscosity of high concentration monoclonal antibodies. In this study, gap dependent changes in the fundamental rheological behavior were observed. At higher gaps, an initial shear thinning behavior was observed at lower shear rates and this trend was found to disappear at thin gaps. This shear thinning which is due to air water interface disappears as the gap size decreases. At high shear rates, there is a convergence of all the viscosity data for all the gaps. This also converges with the mVROC data. However, at smallest gaps studied (50 µm) shear thickening is observed at intermediate shear rates. This maybe attributable to the protein molecules undergoing flow induced aggregation due to increased confinement thereby causing shear thickening and an increase in viscosity. However, this trend eventually diminishes at higher shear rates which could be attributed to flow induced alignment of protein aggregates thereby causing a decrease in viscosity. Addition of either excipients (like Arginine- HCl, NaCl) or surfactants (like polysorbate80) seem to have a drastic impact on shear thickening caused potentially by flow induced aggregation. Addition of excipients also resulted in approximately 33–50% decrease in the viscosity of monoclonal antibody (mAb) solution and the diffusion interaction parameter kD was seen to be indicative of the high shear rate viscosity behavior of these formulations.

Modeling heat exchangers with an open source DEM-based code for granular flows

Dense granular flows exist in many solid particle heat exchangers and solar receivers studied in the field of Concentrating Solar Power (CSP). By tracking particles individually with the Discrete Element Method (DEM), the details of particle friction, collisions, and mixing can be modeled accurately. An open source DEM-based code for modeling heat transfer in dense granular flows is presented, called Dense Particle Heat Transfer (DPHT). It uses one-way coupling, with DEM run first to find the particle positions and DPHT run second to calculate heat transfer between particles and any walls. Heat transfer is computed with six sub-models, including effects from contact conduction, conduction through the thin fluid gap between particles, and thermal radiation. Simulations are run to investigate particle-particle radiation, with DPHT matching a full Monte Carlo ray tracing simulation to within 1.6%, whereas the “local environment temperature” models from literature show physically unrealistic results. As a test of the accuracy of DPHT, a simulation is run to replicate published experimental work, and results in terms of total heat transfer are within 4%. Finally, a tubular heat exchanger is analyzed, and a “radial” mixer design is introduced, increasing heat transfer by 8%. Several DEM-based heat transfer codes have been described in literature, but they are often kept in-house. Some open source codes exist as well, but they generally have drawbacks including missing heat transfer modes, insufficient flexibility to make significant changes, and incomplete documentation. DPHT aims to simplify this modeling method by providing a flexible, open source solution.

Thin gap rheometry for high shear viscosity measurement

Thin gap rheometry for high shear viscosity measurement

Anchoring and migration of balloon in REBOA

A mechanical theory is described for a phenomenon in the surgical procedure of resuscitative endovascular balloon occlusion of the aorta (REBOA). In this procedure a balloon is pushed into the aorta by a catheter and then inflated in order to stop haemorrhage. One of the hazards of this procedure is the tendency for the balloon to migrate away from its intended position. This work examines the mechanics of balloon anchoring and migration by analysing the effects of pressure waves, the sheet flow and solid friction in the thin gap between the walls of the aorta and balloon. A viscoelastic model is adopted for the aorta wall for pressure waves between the left ventricle and the balloon. The lubrication approximation is used for blood flow in the thin gap between the walls of the balloon and aorta. Samples of quantitative predictions are discussed on how the inflation pressure and balloon characteristics affect the balloon anchoring and migration. The crucial roles of solid friction and balloon placement are pointed out, which should help in guiding the manufacturing of balloons and their usage in the field.

Cavity and ground effects on a superconducting microstrip resonator

Superconducting planar-transmission-line resonators play an increasingly important role in applications such as astronomical detection and circuit quantum electrodynamics. When measuring the transmission response of an array of resonators, however, one often observes some spurious resonances besides the intrinsic ones. In this letter, the effect of the cavity accommodating a half-wavelength superconducting microstrip resonator is investigated. An attenuation pole associated with the intrinsic resonance of the half-wavelength resonator is clearly observed and found to be resulted from the mutual coupling between the microstrip resonator and the cavity. In addition, it is demonstrated that adding a superconducting ground layer for such a microstrip resonator can avoid the frequency shift owing to an ever-present thin air gap between the microstrip resonator and the cavity and can also improve the Q factor of the microstrip resonator.

Thermosuperrepellency of a hot substrate caused by vapour percolation

Drop rebound after collision with a very hot substrate is usually attributed to the Leidenfrost effect, characterized by intensive film boiling in a thin vapour gap between the liquid and substrate. Similarly, drop impact onto a cold superhydrophobic substrate leads to a complete drop rebound, despite partial wetting of the substrate. Here we study the repellent properties of hot smooth hydrophilic substrates in the nucleate boiling, non-Leidenfrost regime and discover that the thermally induced repellency is associated with vapour percolation on the substrate. The wetting structure in the presence of the percolating vapour rivulets is analogous to the Cassie-Baxter wetting mode, which is a necessary condition for the repellency in the isothermal case. The theoretical predictions for the threshold temperature for vapour percolation agree well with the experimental data for drop rebound and correspond to the minimum heat flux when spray cooling.

Broadband RCS reduction for both microstrip array and Fabry‐Perot antenna based on the quasi‐ AMC superstrate

This article presents a new type of quasi-AMC superstrate (QAMCS), which can achieve wideband RCS reduction (RCSR) for both the microstrip array and Fabry-Perot (FP) antenna. The proposed QAMCS comprises of two-layer metallic patterns with a thin air gap. The top-layer consists of two types of frequency selective surfaces (FSSs) in a checkerboard layout, and the wideband RCSR is realized based on the phase cancelation principle. The bottom-layer consists of the slotted FSS, to reflect out-of-band signal while allowing the in-band signal to pass through with a low insertion loss. Besides, the reflection phase of the proposed QAMCS is about −180° around higher frequencies. Therefore, it can be regarded as a partially reflecting surface (PRS) to construct the FP antenna with a highgain and low-RCS. The simulation and measurement results show that the bandwidth of 10-dB RCSR is more than 76% (7.2-16.1 GHz). The 10-dB impedance bandwidth of the array antenna is ranging from 16.6 to 18.6 GHz. For the FP antenna, its aperture efficiency is 31.5% and the peak gain is 17.5 dBi at 20 GHz.

Mediation of lubricated air films using spatially periodic dielectrophoretic effect

A stone thrown in a lake captures air as it collides with water and sinks; likewise a rain drop falling on a flat surface traps air bubbles underneath and creates a spectacular splash. These natural occurrences, from bubble entrapment to liquid ejection, happen as air fails to escape from the closing gap between liquid and solid surfaces. Trapping of air is devastating for casting, coating, painting, and printing industries, or those intolerant of water entry noise. Attempts to eliminate the interfering air rely on either reducing the ambient pressure or modifying the solid surfaces. The former approach is inflexible in its implementation, while the latter one is inherently limited by the wetting speed of liquid or the draining capacity of air passages created on the solid. Here, we present a “divide and conquer” approach to split the thin air gap into tunnels and subsequently squeeze air out from the tunnels against its viscous resistance using spatially periodic dielectrophoretic force. We confirm the working principles by demonstrating suppression of both bubble entrapment and splash upon impacts of droplets on solid surfaces.

Demonstration of electronic devices in graphitic carbon nitride crystalline film

Graphitic carbon nitride (g-C3N4) exhibits semiconducting properties and is a promising candidate for use as a metal-free functional material. Electronic transport in g-C3N4 depends on the crystal orientation, resulting in the anisotropic characteristics of low out-of-plane and high in-plane resistivity. We investigated a Schottky barrier diode (SBD) and a heterojunction diode (HJD) with out-of-plane transport properties and a top-gate device with in-plane transport properties. The SBD with a Cr/Au Schottky contact exhibited rectifying behavior with a turn-on voltage of ∼1.0 V and estimated series resistance and barrier height at the interface of 1.63 kΩ and 344 meV, respectively. The HJD comprises a g-C3N4 film and an n-type hexagonal silicon carbide (4H–SiC) substrate, with a turn-on voltage of 4.0 eV. The HJD belonged to a type-II band alignment with a staggered-gap; it had a thin insulator-based van der Waals gap at the interface, thereby inducing tunneling transport. In-plane carrier transport control was carried out by the top-gate device with a Parylene-C film gate dielectric and was achieved only when the negative bias voltage was applied along the out-of-plane direction, indicating the realization of the normally off switch that utilizes the intrinsic transport characteristics and a simple device structure.

Design and Fabrication of Thermosyphon Water Purification System

Lack of clean drinking water in rural areas is a huge problem during the occurrences of floods and other environmental disasters. Often, it takes a long time to transport potable water to these areas resulting in health issues for the residents. In this research, a solar power-based water purification system using PCM to produce clean drinking water in flood-affected areas or remote areas where potable water is difficult to obtain is proposed. Purification reduces the concentration of particulate matter including suspended particles, parasites, bacteria, algae, viruses, and fungi as well as reduces the concentration of a range of dissolved and particulate matter. The purification system available is not easy to get for poor people. So we are using a different technique for water purification system is solar distillation technique, which is very cheap and convenient. These Thermosyphon purification system is a modification of conventional solar still but the efficiency achieved is much higher then the conventional solar still. There are 5 major components in our design consists of Upper basin, Lower basin, Thermosyphon system, Diffusion still, and PCM chamber. The dirty water inlet is taken into Lower basin, upper basin, and diffusion still. Initially the temperature of water in the lower basin is low, so to increase the temperature of the water, thermosyphon loop system is connected with the lower basin. The energy from the lower basin is transferred to the condensing cover and the side walls of the tank which is been wasted to surroundings will be captured by upper basin and diffusion still. In diffusion still, there will be a successive plate, so energy from sidewalls will be evaporated and will be diffuse in a thin gap and it will get condense of the facing surface and that water will be collected in the outlet. We will be adding phase-changing material, which helps the purification to work on in absence of sunlight. So our basic design of the project is to increase the rate of evaporation and condensation process.

Optical quantum technologies with hexagonal boron nitride single photon sources

Single photon quantum emitters are important building blocks of optical quantum technologies. Hexagonal boron nitride (hBN), an atomically thin wide band gap two dimensional material, hosts robust, optically active luminescent point defects, which are known to reduce phonon lifetimes, promises as a stable single-photon source at room temperature. In this Review, we present the recent advances in hBN quantum light emission, comparisons with other 2D material based quantum sources and analyze the performance of hBN quantum emitters. We also discuss state-of-the-art stable single photon emitter’s fabrication in UV, visible and near IR regions, their activation, characterization techniques, photostability towards a wide range of operating temperatures and harsh environments, Density-functional theory predictions of possible hBN defect structures for single photon emission in UV to IR regions and applications of single photon sources in quantum communication and quantum photonic circuits with associated potential obstacles.

The Ependymal Region Prevents Glioblastoma From Penetrating Into the Ventricle via a Nonmechanical Force.

BackgroundIntraventricular penetration is rare in glioblastoma (GBM). Whether the ependymal region including the ependyma and subventricular zone (SVZ) can prevent GBM invasion remains unclear.MethodsMagnetic resonance imaging (MRI) and haematoxylin–eosin (HE) staining were performed to evaluate the size and anatomical locations of GBM. Binary logistic regression analysis was used to assess the correlation between tumor-ependyma contact, ventricle penetration and clinical characteristics. Cell migration and invasion were assessed via Transwell assays and an orthotopic transplantation model.ResultsAmong 357 patients with GBM, the majority (66%) showed ependymal region contact, and 34 patients (10%) showed ventricle penetration of GBM. GBM cells were spread along the ependyma in the orthotopic transplantation model. The longest tumor diameter was an independent risk factor for GBM-ependymal region contact, as demonstrated by univariate (OR = 1.706, p < 0.0001) and multivariate logistic regression analyses (OR = 1.767, p < 0.0001), but was not associated with ventricle penetration. Cerebrospinal fluid (CSF) could significantly induce tumor cell migration (p < 0.0001), and GBM could grow in CSF. Compared with those from the cortex, cells from the ependymal region attenuated the invasion of C6 whether cocultured with C6 or mixed with Matrigel (p = 0.0054 and p = 0.0488). Immunofluorescence analysis shows a thin gap with GFAP expression delimiting the tumor and ependymal region.ConclusionThe ependymal region might restrict GBM cells from entering the ventricle via a non-mechanical force. Further studies in this area may reveal mechanisms that occur in GBM patients and may enable the design of new therapeutic strategies.

Dynamics of pressure pulsations in thin annular gap

Fluid pulsations can significantly influence behavior of bearings or sealing parts of hydraulic machines and therefore their operation. In this contribution, an analytical approach to solve pressure pulsations dynamics is compared with a computational solution using acoustic simulation in ANSYS Mechanical FEM package. Studied problem is simplified to an annular gap and the pressure pulsations are excited either from one annulus end or excitation is made by a movement of an inner cylindrical surface perpendicularly to its axis. Excitation on an annulus surface can have angle dependent phase. This geometry allows a linearization of governing equations and so the equations are solvable analytically. Compressibility was incorporated to analytical and computational approach so the eigen frequencies for both methods were evaluated and compared. Also the added fluid effects were studied and evaluated.

Theoretical study of oscillating squeezing flow through a porous medium

In this paper, we report a theoretical study of a transient squeezing flow through a thin porous gap driven by an oscillating boundary. The process is governed by the viscous, inertial, and Darcy effects. It shows that when the squeezing depth increases, the alternating dominance of the viscous and inertial effects would increase the oscillation of the velocity profiles. The existence of the porous media effectively stabilizes the fluid field. The study presented herein, revealing the fundamental physics of an oscillating squeezing flow, has significant potential for biomedical and industrial applications, such as the cerebrospinal fluid flow under concussion and the oil film lubrication in journal bearings.

Destabilization of super-rotating Taylor–Couette flows by current-free helical magnetic fields

In an earlier paper we showed that the combination of azimuthal magnetic fields and super-rotation in Taylor–Couette flows of conducting fluids can be unstable against non-axisymmetric perturbations if the magnetic Prandtl number of the fluid is $\textrm {Pm}\neq 1$ . Here we demonstrate that the addition of a weak axial field component allows axisymmetric perturbation patterns for $\textrm {Pm}$ of order unity depending on the boundary conditions. The axisymmetric modes only occur for magnetic Mach numbers (of the azimuthal field) of order unity, while higher values are necessary for the non-axisymmetric modes. The typical growth time of the instability and the characteristic time scale of the axial migration of the axisymmetric mode are long compared with the rotation period, but short compared with the magnetic diffusion time. The modes travel in the positive or negative $z$ direction along the rotation axis depending on the sign of $B_\phi B_z$ . We also demonstrate that the azimuthal components of flow and field perturbations travel in phase if $|B_\phi |\gg |B_z|$ , independent of the form of the rotation law. Within a short-wave approximation for thin gaps it is also shown (in an appendix) that for ideal fluids the considered helical magnetorotational instability only exists for rotation laws with negative shear.

Porous Hydrophobic-Hydrophilic Composite Hollow Fiber and Flat Membranes Prepared by Plasma Polymerization for Direct Contact Membrane Distillation.

High water vapor flux at low brine temperatures without surface fouling is needed in membrane distillation-based desalination. Brine crossflow over surface-modified hydrophobic hollow fiber membranes (HFMs) yielded fouling-free operation with supersaturated solutions of scaling salts and their precipitates. Surface modification involved an ultrathin porous polyfluorosiloxane or polysiloxane coating deposited on the outside of porous polypropylene (PP) HFMs by plasma polymerization. The outside of hydrophilic MicroPES HFMs of polyethersulfone was also coated by an ultrathin coating of porous plasma-polymerized polyfluorosiloxane or polysiloxane rendering the surface hydrophobic. Direct contact membrane distillation-based desalination performances of these HFMs were determined and compared with porous PP-based HFMs. Salt concentrations of 1, 10, and 20 wt% were used. Leak rates were determined at low pressures. Surface and cross-sections of two kinds of coated HFMs were investigated by scanning electron microscopy. The HFMs based on water-wetted MicroPES substrate offered a very thin gas gap in the hydrophobic surface coating yielding a high flux of 26.4–27.6 kg/m2-h with 1 wt% feed brine at 70 °C. The fluxes of HFMs on porous PP substrates having a long vapor diffusion path were significantly lower. Coated HFM performances have been compared with flat hydrophilic membranes of polyvinylidene fluoride having a similar plasma-polymerized hydrophobic polyfluorosiloxane coating.

Simulation the motion of a viscous fluid containing graphene plates in the gap between static and rotating stepped discs

The motion of a viscous fluid containing graphene nanostructures in a thin gap between a stationary stepped stator and a rotating stepped rotor is considered. Dependences are obtained for calculating the parameters of motion of an elementary volume of a viscous liquid. Using the Maple mathematical package, characteristic trajectories of movement of elementary volumes of fluid in the gap are obtained. A similar idea of the movement trajectories of an elementary volume was obtained using computational fluid dynamics using the Flow Vision package (TESIS, Russia). The transition from a mathematical description to a computer model makes it possible to take into account changes in the viscosity of a liquid caused by a change in the concentration of graphite in the initial suspension. The use of a computer model opens the way to modeling the mixing of graphene nanostructures with a viscous liquid.

Mathematical Modelling and Computer Simulation of the Flow in Thin Gap Channel due to Alternating Volumetric Mass Forces

The mathematical modelling and computer simulation are presented for the complex flow in thin gap channel due to alternating volumetrically distributed mass forces. The flow equations and obtained analytical solutions for limit cases are considered in the cylindrical coordinate system with the axis directed along the channel, which is rotating around its axis. The channel is placed inside the cylinder on the edge of the circular horizontal disk, which is rotating around vertical axis in its centre. The two rotations around different perpendicular axes create complex unknown features in a flow due to the alternating centrifugal and Coriolis forces, which substantially vary by the angle. The centrifugal force from the disk rotation is directed to its edge, while the centrifugal force due to rotation of the channel is acting by the channel’s radius. As a result, the two different centrifugal forces are directed counter currently in one side of the channel and vary by the angle up to adding of the two of them in the same direction in the opposite side of the channel. The conditions may fit to the strong cavitation regime inside the volume of fluid flow due to a stretching of the liquid in some locations.

Investigation of Position and Velocity Stability of the Nanometer Resolution Linear Motor Stage with Air Bearings by Shaping of Controller Transfer Function

Modern industrial enterprises require high accuracy and precision feedback systems to fulfil cutting edge requirements of technological processes. As demand for a highly accurate system grows, a thin gap between throughput and quality exists. The conjunction of ultrafast lasers and modern control strategies of mechatronic systems can be taken into account as an effective solution to reach both throughput and tolerances. In the present paper, the dynamic errors of the moving platform of the one degree of freedom stage, based on linear motor and air bearings, have been analyzed. A precision positioning system is investigated as a symmetric system which is based on symmetric linear motor. The goal of the present article is to investigate the controllers of the different architecture and to find the best controller that can ensure a stable and small dynamic error of the displacement of the stage platform at four different constant velocities of the moving platform. The relations between the controller order, velocity and the displacement dynamic error have been investigated. It is determined that higher-order controllers can reduce the dynamic error significantly at low velocities of the moving platforms: 1 and 5 mm/s. On the contrary, the low order controllers of 4th-degree polynomials of the transfer function can also provide small dynamic errors of the displacement of the platform.

The STAR detector upgrades for the BES II and beyond physics program

The Beam Energy Scan program (BES) at the Relativistic Heavy Ion Collider (RHIC) is dedicated to explore the Quantum Chromodynamics (QCD) phase diagram and to search for the critical point of the QCD phase transition. The results from the BES phase I program show hints of a first-order phase transition in the QCD phase diagram and the turn-off of the characteristic signatures of the quark gluon plasma at low collision energies, sNN<20GeV. Three upgrades of the STAR detector, the inner Time Projection Chamber, the Event Plane Detector, and the endcap Time Of Flight, provide unique opportunities to further investigate the nature of the QCD phase diagram during the BES phase II program (BES II), which covers the sNN from 7.7 to 19.6 GeV in the collider mode and from 3 to 7.7 GeV in the fixed-target mode. Beyond the BES II, the STAR Collaboration currently designs, constructs, and installs a suite of new detectors in the forward rapidity region (2.5 <η < 4) over the next two years, enabling a program of novel measurements in p+p, p+A and A+A collisions. This extension of STAR's kinematic reach will allow a detailed study of cold QCD physics at both very high and very low partonic momentum fraction. The new subdetectors to be installed comprise a Forward Calorimeter System, with electromagnetic and hadronic calorimetry. As well as a Forward Tracking System, which consists of 3 layers of silicon mini-strip detectors and 4 layers of small-strip Thin Gap Chambers. In this presentation, the detailed description on the STAR detector upgrades for the BES II and beyond, their performance, as well as the future physics opportunities, will be given.