Fullerene Derivatives Attenuate Bronchoconstriction Induced by Xanthine-Xanthine OxidaseX

The intratracheal instillation of xanthine-xanthine oxidase caused a marked decrease in dynamic respiratory compliance, indicating airway constriction. The constriction was significantly attenuated by fullerenol-1, but not by other agents or receptor antagonists.     

Rational choice of the constriction of a flowmeter

The solution of the urgent problem of choosing the type of constriction in flowmeters with a variable pressure drop in industrial instruments for measuring the flow rate of liquids, gases and vapors is considered. Ten criteria are established by which the constriction must be chosen, numerical characteristics are given, and recommendations are made on the rational area of application of each type of constriction. Translated from Izmeritel'naya Tekhnika, No. 9, pp. 33–35, September, 1996     

Nano patterning of cone dots and nano constrictions of negative e-beam resist for single electron transistor fabrication

We present an optimization of nano dot of negative tone e-beam resist which is a very important step in single electron transistor fabrication process. The optimum design of dot and nano constriction plays a significant role in determining optimum etching resolution and single electron transistor performance. In this research, we have optimized nano dot and nano constriction dimensions of resist by controlling some parameters, such as e-beam dose, spin speed, pre-bake time and image development time. However, a nano constriction design variety of 120–200 nm in width was carried out to reach the optimum design. In this paper, the fabrication process of cone nano dots using e-beam lithography with considering proximity effect is reported. As nano constriction design decreased, cone nano dot changed to pyramid nano dot and the compression effect on the dot also significantly increased as well.     

High-yield electrofusion of biological cells based on field tailoring by microfabricated structures

The authors present the use of electric-field constriction created by a microfabricated structure to realise high-yield electrofusion of biological cells. The method uses an orifice on an electrically insulating wall (orifice plate) whose diameter is as small as that of the cells. Owing to the field constriction created by the orifice, we can induce the controlled magnitude of membrane voltage selectively around the contact point, regardless of the cell size. The field constriction also ensures 1:1 fusion even when more than two cells are forming a chain at the orifice. A device for electrofusion has been made with a standard SU-8 lithography and PDMS molding, and real-time observation of the electrofusion process is made. Experiments using plant protoplasts or mammalian cells show that the process is highly reproducible, and the yield higher than 90% is achieved.     

Transport Measurements of Strongly Correlated Electrons on Helium in a Classical Point-Contact Device

We present transport measurements of electrons on the surface of liquid helium in a microchannel device in which a constriction may be formed by a split-gate electrode. The surface electron current passing through the microchannel first decreases and is then completely suppressed as the split-gate voltage is swept negative. The current decreases in a steplike manner, due to changes in the number of electrons able to pass simultaneously through the constriction. We investigate the dependence of the electron transport on the AC driving voltage and the DC potentials applied to the sample electrodes, in order to understand the electrostatic potential profile of the constriction region. Our results are in good agreement with a finite element modeling analysis of the device. We demonstrate that the threshold of current flow depends not only on the applied potentials but also on the surface electron density. The detailed understanding of the characteristics of such a device is an important step in the development of mesoscopic experiments with surface electrons on liquid helium.     

A Size‐Selective Intracellular Delivery Platform

Identifying and separating a subpopulation of cells from a heterogeneous mixture are essential elements of biological research. Current approaches require detailed knowledge of unique cell surface properties of the target cell population. A method is described that exploits size differences of cells to facilitate selective intracellular delivery using a high throughput microfluidic device. Cells traversing a constriction within this device undergo a transient disruption of the cell membrane that allows for cytoplasmic delivery of cargo. Unique constriction widths allow for optimization of delivery to cells of different sizes. For example, a 4 μm wide constriction is effective for delivery of cargo to primary human T‐cells that have an average diameter of 6.7 μm. In contrast, a 6 or 7 μm wide constriction is best for large pancreatic cancer cell lines BxPc3 (10.8 μm) and PANC‐1 (12.3 μm). These small differences in cell diameter are sufficient to allow for selective delivery of cargo to pancreatic cancer cells within a heterogeneous mixture containing T‐cells. The application of this approach is demonstrated by selectively delivering dextran‐conjugated fluorophores to circulating tumor cells in patient blood allowing for their subsequent isolation and genomic characterization.     

Josephson Effect in the Micron and Submicron YBCO Constrictions Fabricated Using the Femtosecond Laser Technique

A femtosecond laser was used successfully to fabricate planar micron and submicron-sized constrictiontype Josephson junctions on YBa₂Cu₃O_7?x thin films. A simple program using G-code (control systems) programming language was written to control the movement of the sample stage during the etching process. The constriction’s geometry was investigated using both atomic force microscopy (AFM) and scanning electron microscopy (SEM). Electrical transport measurements were performed at different temperatures. Shapiro steps were observed and analyzed. The micron-sized constriction shows a linear relationship for the measured critical current against the temperature which is consistent with the behavior of an S–s’–Stype Josephson junction where “S” stands for a bulk superconductive material that is untouched by the laser and “s”’ is superconducting material whose critical temperature is lower than the value of “S” In the case of the narrower submicronsized constriction, the measured critical current dependence with temperature shows an exponential decay, which is consistent with the behavior of the long S–N–Stype Josephson junction where “N” stands for a normal material. A model is proposed to describe the observed behavior by considering the effect of sample heating during the constriction’s fabrication.     

Working tubes for metrological constriction devices

To improve the accuracy in flow measurement, the tubes connecting to the constriction are turned to exact diameters on a lathe. The internal diameter is used in designing the constriction device. Translated from Izmeritel'naya Tekhnika, No. 6, pp. 60–62, June, 2000.     

Lattice expansion in seamless bilayer graphene constrictions at high bias

Our understanding of sp(2) carbon nanostructures is still emerging and is important for the development of high performance all carbon devices. For example, in terms of the structural behavior of graphene or bilayer graphene at high bias, little to nothing is known. To this end, we investigated bilayer graphene constrictions with closed edges (seamless) at high bias using in situ atomic resolution transmission electron microscopy. We directly observe a highly localized anomalously large lattice expansion inside the constriction. Both the current density and lattice expansion increase as the bilayer graphene constriction narrows. As the constriction width decreases below 10 nm, shortly before failure, the current density rises to 4 × 10(9) A cm(-2) and the constriction exhibits a lattice expansion with a uniaxial component showing an expansion approaching 5% and an isotropic component showing an expansion exceeding 1%. The origin of the lattice expansion is hard to fully ascribe to thermal expansion. Impact ionization is a process in which charge carriers transfer from bonding states to antibonding states, thus weakening bonds. The altered character of C-C bonds by impact ionization could explain the anomalously large lattice expansion we observe in seamless bilayer graphene constrictions. Moreover, impact ionization might also contribute to the observed anisotropy in the lattice expansion, although strain is probably the predominant factor.     

Light intensity analysis of plasma jet constriction with applied magnetic field

Light intensity analysis was carried out to consider the constriction of plasma jet with the application of a strong magnetic field. Argon was employed as working gas. Plasma jet was generated in a vacuum chamber by a plasma torch and went into a magnet bore. The magnet composed of a pair of superconducting coils imposes a strong axial magnetic field on the jet. The jet between the coils was taken with  a digital single-lens reflex camera through viewing window. The light intensity is determined from the RAW image files of the camera with the software for analyzing the RAW format. The jet constriction with applied magnetic field was evaluated quantitatively on the basis of the obtained results. The distributions of the light intensity were also compared with those of the typical spectral lines from excited argon that were measured at the same time as shooting the images. The results suggest that the light intensity analysis of the RAW image files could be utilized for the quantitative evaluation of the constriction of plasma jet due to the magnetic field.     

Constriction and Corner Permeances for Finite Domains

The known formulas for two-dimensional "corner" and "constriction" permeances, which were derived by using conformal mappings for infinite domains, can be applied only for large enough domains. In this paper, we analytically solve the problem for finite domains and propose new exact and approximate formulas. We show that, for finite domains, the corner and constriction permeances can be much smaller than for infinite dimensions, and we determine the limits of applicability of simple exact formulas. This offers the possibility to make more accurate analytical calculations of magnetic devices and better evaluate acting magnetic forces     

Oscillatory non-Newtonian flow in tubes of slowly varying radius

Summary The paper studies low Reynolds number flow of a non-Newtonian fluid in an axisymmetric tube of slowly varying radius which is subjected to an axial oscillatory pressure gradient. It is observed that the leading approximation is affected by the visco-elastic coefficient. In the higher approximation particular attention is centered around the steady streaming components for both small and large values of the frequency of oscillation. On the overall the combined effect of visco-elast c and cross viscosity parameter is to induce a radial pressure gradient. For the velocity components the Newtonian and non-Newtonian effects are of the same magnitude when the frequency is small; but when this frequency is large the non-Newtonian effects swamp the flow velociites. When the results are applied to a locally constricted tube, flow reversal is possible downstream of this constriction. The most striking feature however is the condition of zero velocity at a locally constricted tube for the steady streaming velocities—upstream of this constriction the velocity is positive while downstream it is negative. In pathophysiology thrombus formation in constrictions is believed to be caused by aggregation of platelets due to endothelium damage. The condition of zero steady streaming velocity at the constriction is another possible explaination of platelet accumulation and possible blood cloting.With 2 Figures     

Gasflußmessung mit Blenden und Düsen

The amount of gas flowing through a duct can be measured by inserting a constriction and detecting the pressure drop at the constriction. In the case of ideal flow conditions, the relation between gas flow and pressure drop can be calculated from fundamental principles. In practical operation, however, disturbing effects have to be considered. The various types of constrictions (orifice, short nozzle, Venturi nozzle) exhibit different characteristics. In the laboratory for vacuum technology of the Fachhochschule in Giessen several rigs for measuring the gas throughput by means of the pressure drop principle have been installed. The characteristics of these rigs have been determined by calibration using primary methods. The apparatus allows the measurement of gas throughput in the range 10^?7 bis 10⁵ mbar · l/s.     

Blood flow dynamics reflect degree of outflow tract banding in Hamburger–Hamilton stage 18 chicken embryos

Altered blood flow during embryonic development has been shown to cause cardiac defects; however, the mechanisms by which the resulting haemodynamic forces trigger heart malformation are unclear. This study used heart outflow tract banding to alter normal haemodynamics in a chick embryo model at HH18 and characterized the immediate blood flow response versus the degree of band tightness. Optical coherence tomography was used to acquire two-dimensional longitudinal structure and Doppler velocity images from control (n = 16) and banded (n = 25, 6–64% measured band tightness) embryos, from which structural and velocity data were extracted to estimate haemodynamic measures. Peak blood flow velocity and wall shear rate (WSR) initially increased linearly with band tightness (p < 0.01), but then velocity plateaued between 40% and 50% band tightness and started to decrease with constriction greater than 50%, whereas WSR continued to increase up to 60% constriction before it began decreasing with increased band tightness. Time of flow decreased with constriction greater than 20% (p < 0.01), while stroke volume in banded embryos remained comparable to control levels over the entire range of constriction (p > 0.1). The haemodynamic dependence on the degree of banding reveals immediate adaptations of the early embryonic cardiovascular system and could help elucidate a range of cardiac adaptations to gradually increased load.     

The constriction model for SNS Josephson junctions

The approach developed by Blonder, Tinkham and Klapwijk (BTK) for calculation of the quasiparticle (qp) current in NcS contacts is generalized to the case of ScNS and SNcNS contacts with disordered NS electrodes. Amplitudes of Andreev and normal reflections at the ballistic constriction are calculated. The relation between the qp current and energy spectrum of NS proximity sandwich is found for arbitrary transparencies of the constriction and NS interfaces. The appearance of new series of subharmonic peaks associated with the two-gap structure in the density of states of NS electrodes is demonstrated. The model is also applied to calculation of the critical and the excess currents in ScNS and SNcNS for different interface parameters. The relevance of the model to transport mechanisms in step-edge HTS SNS contacts is discussed.     

A bipolar spin-filtering effect in graphene zigzag nanoribbons with spin-orbit coupling

We predict a large spin-filtering effect in graphene zigzag nanoribbons in the presence of Rashba spin-orbit coupling. The spin polarization of the transmitted current reaches a maximum when the incoming electrons occupy only one subband and the outgoing electrons occupy two subbands (spin is not taken into account). This situation can be reached by applying a potential barrier or a width constriction to the incoming lead of the ribbon. A simple physical picture is provided to explain the spin-filtering effect. Because of the electron-hole symmetry and the time-reversal symmetry, the spin-filtering is antisymmetric for the hole when compared with that for the electron. So the bipolar spin-polarized current can be generated by tuning the Fermi energy across the Dirac point. Besides, the wedge-shaped constriction can modify the conductance spin polarization.     

Lattice Effects on Charge Localization in Cuprates

Recent experimental results on cuprates and manganites, including those of elastic and inelastic neutron scattering measurements, suggest that charges are not homogeneously distributed even in the metallic state in these compounds. Charge inhomogeneity results from spin/lattice charge constriction. In cuprates the LO phonons strongly reflect the temperature- and composition-dependent charge inhomogeneity and may possibly be involved in causing it. Unlike the static stripes that compete against superconductivity, the charge inhomogeneity seen by the LO phonons is markedly increased in the superconducting phase. A new mechanism of high-temperature superconductivity involving lattice/spin charge constriction is proposed.     

收缩电阻的高频特性研究

文章重点分析接触界面处的收缩电阻与信号频率之间的关系。首先推导出了收缩电阻关于频率的理论表达式，然后依据实验室所采用的触头尺寸以及直流情况下的实验数据，可以直观的得到收缩电阻关于频率的变化规律。这些研究成果对今后继续深入研究接触界面的腐蚀与传输高频数字信号完整性之间的关系，提供了很好的依据。     

Asymmetric ion track nanopores for sensor technology. Reconstruction of pore profile from conductometric measurements

We reconstruct the profile of asymmetric ion track nanopores from an algorithm developed for conductometric measurements of symmetric nanopores. The validity of the reconstruction is supported by FESEM observations. Our analysis reveals that asymmetric pores fabricated by one-sided etching are funnel-like and not conical. The analysis provides the constriction diameter and the pore profile as a function of etching time. The reconstruction of the pore profile defines the starting conditions of asymmetric nanopores at breakthrough. The deviation from the conical shape is most pronounced at the pore tip. This critical zone dominates transport properties relevant to ion conductance, selectivity, current rectification, resistive pulse sensing and biosensors. The classical cone approximation used until now underestimates the tip diameter by a factor of two. As transport processes in nanopores depend in a highly nonlinear way on the constriction diameter the presented reconstruction must be taken into account when studying ionic and molecular transport processes in asymmetric pores.