Pump Channel Research Articles

Crosstalk of Signals in Pump Probe Structure with Self-phase Modulation and Cross-phase Modulation

The transmission of optical signals under the effects of cross-phase modulation (XPM) and self-phase modulation (SPM) together in pump-probe wave structure is investigated in intensity modulation-direct detection wavelength division multiplexing (IM-DD WDM) systems. A simple expression for frequency domain IM of probe channel is derived. The analytical method to determine the temporal shape of probe wave when arbitrary wave is inputted in pump channel is confirmed. The impact of channel separation and transmission rate to XPM is assessed. We find that the SPM in pump channel increase temporal intensity modulation index reflected XPM to a certain extent. The analytical result agrees well with numerical simulation.

Frequency domain model to calculate the pump to signal RIN transfer in multi-pump Raman fiber amplifiers

In this paper, a novel frequency domain model to compute the pump to signal relative intensity noise (RIN) transfer in multi-pump Raman fiber amplifiers (RFAs) is proposed. The analytical expressions for RFAs with single pump and single signal channel are derived as a specific case of the model. The formulas exactly agree with the published results both for the co-pumped and counter-pumped RFAs. Afterwards, the pump to signal RIN transfer in multi-pump RFAs is studied numerically with thorough discussions.

New trends in increasing the quality of para-aramid fibres from domestic manufacturers

Changing the design of metering pumps used in spinning allows increasing the quality of para-aramid fibres. When the cast-iron body of the pumps is replaced by a body made of a composite material with a polymer matrix, the amount of gas bubbles formed in electrochemical and chemical reactions in friction pairs and in pump channels decreases.

Alteration of Cyclopiazonic Acid-Mediated Contracture of Mouse Diaphragm after Denervation

As a major Ca²⁺ source for muscle contraction, the sarcoplasmic reticulum (SR) of skeletal muscle maintains its Ca²⁺ content by uptake of myoplasmic Ca²⁺ and by replenishment with extracellular Ca²⁺. Since transection of motor nerve alters the functions of SR Ca²⁺ pump and sarcolemma ion channels, this study explored the effect of denervation on the contracture evoked by cyclopiazonic acid (CPA), an inhibitor of SR Ca²⁺ pump. In innervated hemidiaphragm, CPA elicited a bimodal elevation of muscle tone, which was dependent on extracellular Ca²⁺ and differentially inhibited by pretreatment with 2-aminoethoxydiphenylborane (APB) and U73122. Activation of muscle Na⁺ channels to simulate denervation-induced membrane depolarization did not change the contracture profile. After denervation for 5–14 days when the contracture induced by caffeine was not yet depressed, CPA elicited only APB-sensitive monophasic contracture. Stimulation of ATP-regulated K⁺ channels with lemakalim hyperpolarized muscle membrane and attenuated CPA contracture in denervated, but not innervated, hemidiaphragm. The effects of lemakalim were antagonized by glybenclamide. It is inferred that the bimodal CPA contracture is resulted from distinct recruitments of Ca²⁺ entry and that denervation alters the voltage dependence and down-regulates CPA-mediated Ca²⁺ influx.

Modeling Gas-Liquid Head Performance of Electrical Submersible Pumps

This study presents a new gas-liquid model to predict electrical submersible pumps head performance. The newly derived approach based on gas-liquid momentum equations along pump channels has improved the Sachdeva model (Sachdeva, R., Doty, D. R., and Schmidt, Z., 1988, “Two-Phase Flow through Electrical Submersible Pumps,” Ph.D. dissertation, The University of Tulsa, Oklahoma; 1994, “Performance of Electric Submersible Pumps in Gassy Wells,” SPE Prod. Facil., 9, pp. 55–60) in the petroleum industry and generalized the Minemura model (Minemura, K., Uchiyama, T., Shoda, S. and Kazuyuki, E., 1998, “Prediction of Air-Water Two-Phase Flow Performance of a Centrifugal Pump Based on One-Dimensional Two-Fluid Model,” ASME J. Fluids. Eng., 120, pp. 327–334) in the nuclear industry. The new two-phase model includes novel approaches for wall frictional losses for each phase using a gas-liquid stratified assumption and existing correlations, a new shock loss model incorporating rotational speeds, a new correlation for drag coefficient and interfacial characteristic length effects by fitting the model results with experimental data, and an algorithm to solve the model equations. The model can predict pressure and void fraction distributions along impellers and diffusers in addition to the pump head performance curve under different fluid properties, pump intake conditions, and rotational speeds.

Effects of Polarization-Mode Dispersion on Cross-Phase Modulation in Dispersion-Managed Wavelength-Division-Multiplexed Systems

This paper develops a vector theory of cross-phase modulation (XPM) in optical fibers and use it to investigate the impact of polarization-mode dispersion (PMD) on the crosstalk induced by XPM in wavelength-division multiplexed lightwave systems. Under certain reasonable approximations, the theory permits us to obtain an analytic expression for the amplitude of probe fluctuations induced by a copropagating pump channel through XPM. We use this expression to calculate the average level of XPM-induced crosstalk together with its variance for several dispersion maps. We show that PMD not only reduces the crosstalk on average, but also impacts the efficiency of a commonly used polarization-interleaving technique.

Large diameter of palytoxin-induced Na/K pump channels and modulation of palytoxin interaction by Na/K pump ligands.

Palytoxin binds to Na/K pumps to generate nonselective cation channels whose pore likely comprises at least part of the pump's ion translocation pathway. We systematically analyzed palytoxin's interactions with native human Na/K pumps in outside-out patches from HEK293 cells over a broad range of ionic and nucleotide conditions, and with or without cardiotonic steroids. With 5 mM internal (pipette) [MgATP], palytoxin activated the conductance with an apparent affinity that was highest for Na+-containing (K+-free) external and internal solutions, lowest for K+-containing (Na+-free) external and internal solutions, and intermediate for the mixed external Na+/internal K+, and external K+/internal Na+ conditions; with Na+ solutions and MgATP, the mean dwell time of palytoxin on the Na/K pump was about one day. With Na+ solutions, the apparent affinity for palytoxin action was low after equilibration of patches with nucleotide-free pipette solution. That apparent affinity was increased in two phases as the equilibrating [MgATP] was raised over the submicromolar, and submillimolar, ranges, but was increased by pipette MgAMPPNP in a single phase, over the submillimolar range; the apparent affinity at saturating [MgAMPPNP] remained ∼30-fold lower than at saturating [MgATP]. After palytoxin washout, the conductance decay that reflects palytoxin unbinding was accelerated by cardiotonic steroid. When Na/K pumps were preincubated with cardiotonic steroid, subsequent activation of palytoxin-induced conductance was greatly slowed, even after washout of the cardiotonic steroid, but activation could still be accelerated by increasing palytoxin concentration. These results indicate that palytoxin and a cardiotonic steroid can simultaneously occupy the same Na/K pump, each destabilizing the other. The palytoxin-induced channels were permeable to several large organic cations, including N-methyl-d-glucamine+, suggesting that the narrowest section of the pore must be ∼7.5 Å wide. Enhanced understanding of palytoxin action now allows its use for examining the structures and mechanisms of the gates that occlude/deocclude transported ions during the normal Na/K pump cycle.

Microfabricated electroosmotic pump for capillary-based sequential injection analysis

A microfabricated electroosmotic pump with an integrated serpentine isolation channel was developed on a glass chip and applied to a capillary-based sequential injection analysis (SIA) system for an enzyme inhibition assay. The pump chip contains an anode reservoir, an ion-exchange membrane electric field decoupler (EFD) that also serves as a cathode reservoir, parallel pump channels and an isolation channel. A two-step etching process was adopted to etch the pump channels to a depth of 20 μm and the isolation channel to a depth of 90 μm. The pump flow rate was very stable: the relative standard deviation (RSD) of the pump rate was 1.9% for propulsion and 2.3% for aspiration. The pump chip was successfully applied to a capillary-based sequential injection analysis system with a confocal fluorescence detector. For repetitive analysis of a 13 μM fluorescein solution, an RSD of 0.6% was attained, which demonstrated the flow stability of the EOF pump. The system was then applied to an enzyme inhibition assay, the diethylenetriaminepentaacetic acid (DTPA) inhibition of the β-galactosidase-catalyzed hydrolysis of fluorescein di(β- d-galactopyranoside). Reproducible results (RSD<3.0%) were obtained.

Modeling and optimization of colloidal micro-pumps

Manipulating micro-particles is very important in microfluidic applications, such as biomedical flows and self-assembled structures. Here, flows generated by the forced motion of colloidal micro-particles in a microchannel are investigated. The force coupling method combined with the spectral/hp element method is used to numerically simulate the dynamics of the flow, while a penalty method is used to determine the required forces on the particles. The pumping motion is investigated for two specific systems: a peristaltic micro-pump and a gear micro-pump. We verify the accuracy of the simulations and then for each system, we investigate the net flow rate as a function of pump frequency and channel dimension, and present optimization results. The results for the net flow rate are comparable to and within the range of the experimental data.

The Effects of an Axial Index on a Low-nonlinear and Nonzerodispersion Wideband Optical Fiber Link containing an Er-doped Dispersion Compensating Optical Fiber Amplifier

We present the simulation results of the effects of axial index dip of an optical fiber amplifier used in an optical fiber communication link. The results are based on the mode field diameter, chromatic dispersion, zero-dispersion length of dispersion compensating optical fiber amplifier, minimum pump power requirement, noise figure, bit rate and channel capacity.

Electric field-decoupled electroosmotic pump for microfluidic devices

An electric field-free electroosmotic pump has been constructed and its pumping rate has been measured under various experimental conditions. The key component of the pump is an ion-exchange membrane grounding joint that serves two major functions: (i) to maintain fluid continuity between pump channels and microfluidic conduit and (ii) to ground the solution in the microfluidic channel at the joint through an external electrode, and hence to decouple the electric field applied to the pump channels from the rest of the microfluidic system. A theoretical model has been developed to calculate the pumping rates and its validity has been demonstrated.

Polyethylene powder microcolumn for protein separation prior to HPLC plasma analysis. Application to the determination of copper and zinc

AbstractThree different types of polyethylene powder (PE) were investigated with regard to their ability to adsorb proteins, with the goal of accomplishing plasma deproteinization for further HPLC analysis. Best results were obtained with ultrahigh molecular mass polyethylene The proteins retained by the PE powder were washed out of the column with methanol followed by water. A chromatographic system with the PE column as pre‐column was set up for the determination of copper and zinc in plasma. The plasma sample was injected into the chromatograph, and, on passage through the pre‐column, the proteins were adsorbed onto the PE. While a protein‐free eluate was being sent to the analytical column, by switching the pump channels the pre‐column was being flushed with methanol and water to elute the adsorbed proteins. After washing, the pre‐column was conditioned with the eluent to receive the next sample. Copper and zinc determination was performed by HPLC with photometric detection after post‐column derivatization with 4‐(2‐pyridylazo)resorcinol (PAR). The results, compared with those from flame atomic absorption spectrometry, showed that zinc can be determined by direct injection of the sample, but copper only after dilution. As the copper recovery from undiluted samples was about 65%, it was probably retained together with the proteins. However, on previous dilution of the sample with the eluent (acidic solution of lactic acid) the copper recovery reached 100%. The proposed method is suitable for the HPLC determination of copper and zinc in plasma samples without further sample treatment, in about 30 min.

Chemiluminescence response of β-glucan stimulated leukocytes isolated from different tissues and peritoneal cavity of Dicentrarchus labrax

The respiratory burst of leukocytes isolated from sea bass (Dicentrarchus labrax) pronephros, peritoneal cavity (P.C.), spleen and blood, was measured by a chemiluminescence (CL) assay after stimulation with β-glucan. The CL response by P.C. and pronephros leukocytes was significantly higher than that expressed by a similar number of cells separated from spleen and blood. This probably reflects the observation that the proportion of macrophages and neutrophils was highest in the populations of leukocytes from peritoneal cavity and pronephros. Comparative observations showed a higher degree of yeast phagocytosis by leukocytes taken from peritoneal cavity than the pronephros. Moreover phagocytic index evaluated by microscopical observations, indicated that peritoneal macrophages internalised more yeast cells than neutrophils (identified by the peroxidase reaction). Scanning electron microscopy observations were also carried out.Inhibition experiments by a myeloperoxidase inhibitor sodium azide, iodonium-diphenyl-chloride which inhibits NADPH-oxidase, and exogenous superoxide dismutase, which catalyses O−2 dismutation to H2O2, supported the correlation between CL and respiratory burst. Treatment with ouabain and DNP suggested that in this response, Ca++ pump channels and calmodulin are involved in a metabolic energy-dependent pathway.

Changes of pH in Petunia hybrida (Hort.) styles induced by pollination and influence of proton pump and ion channels on its regulation

Ionselective microelectrode method was used to study changes of pH in transmitting tissue of style in Petunia hybrida (Hort.). Effect of pollination and pollen tube growth were examined. Subsequently solutions of ions and various stimulators or blockers of ion channels were applied on pollinated styles to examine the possible role of ion channels in pH stabilisation. It was confirmed in the present study that: (1) there is a pH gradient in the transmitting tissue of a petunia unpollinated style with the stigma region being more acidic; (2) pollination causes further acidification of transmitting tissue: (3) the gradient of pH first vanishes at 24 h after pollination then is reversed up to 72 h after pollination; (4) active transport of ions plays an important role in pH regulation in transmitting tissue. The presented results confirm the role of pH changes and Ca2+ as a mediator in controlling proton influx into the apoplast of the transmitting tissue during pollen tube growth.

Change of cytosolic Ca(2+) mobility in cultured bovine corneal endothelial cells by endothelin-1.

The effect of endothelin-1 (ET-1) on the intracellular free Ca(2+) ([Ca(2+)](i)) in cultured bovine corneal endothelial cells was studied after loading with fura-2-AM. In Ca(2+)-containing buffer and Ca(2+)-free buffer, ET-1 induced a significant rise in [Ca(2+)](i) at concentrations from 10(-9) to 10(-7) M. In Ca(2+)-free buffer, pretreatment of the cells with ET-1 inhibited thapsigargin-induced [Ca(2+)](i) increase and carbonylcyanide m-chlorophenylhydrazone (CCCP)-induced Ca(2+) release by 99% and 62%, respectively. Pretreatment of the cells with thapsigargin or CCCP also inhibited ET-1-induced [Ca(2+)](i) rise by 36% and 92%, respectively. In Ca(2+)-containing buffer, the ET(A) receptor antagonist (BQ123) and ET(B) receptor antagonist (BQ788) partially inhibited ET-1-induced [Ca(2+)](i) by 92% and 98%, respectively. Nifedipine and La(3+) also inhibited ET-1-induced [Ca(2+)](i) increase by 26% and 91%, respectively. The intracellular calcium release caused by ET-1 was partially inhibited by phospholipase C inhibitor (U73122). After incubation of the cells with ET-1 in Ca(2+)-free buffer, the addition of 5 mM CaCl(2) increased Ca(2+) influx, implying that release of Ca(2+) from internal stores caused by ET-1 further induced capacitative Ca(2+) entry. These data suggest that ET-1-induced [Ca(2+)](i) rise in bovine corneal endothelial cells are mediated by ET(A) receptor, ET(B) receptor, La(3+)-sensitive Ca(2+) pump and L-type voltage-operated Ca(2+) channel, leading to Ca(2+) influx. ET-1 also increased the internal Ca(2+) release from endoplasmic reticulum and mitochondria Ca(2+) stores followed by capacitative Ca(2+) entry. ET-1-induced intracellular Ca(2+) release was modulated by phospholipase C-coupled events.

Effect of low pH on glutamate uptake and release in isolated presynaptic endings from rat brain.

The effect of acidification of the incubation medium on the membrane potential and glutamate uptake and release was studied in isolated presynaptic neuronal endings (synaptosomes) from rat brain. Using the fluorescent probe diS-C3-(5), a rapid depolarization of plasma membrane was detected at pH 6.0, most probably as a result of the inhibition of the sodium pump and potassium channel blockade. The membrane potential decrease did not result in increase of basal efflux of glutamate. Glutamate release following K(+)-induced depolarization was decreased upon lowering pH to 6.0. Acidosis inhibited mainly calcium-dependent (vesicular) release of glutamate and did not significantly reduce [14C]glutamate uptake. This inhibition of glutamate release but not of glutamate uptake may be a mechanism of the protective effect of acidosis during brain ischemia.

MHD-features of the main service and bypass pump in the MEGAPIE design

Within the MegaWatt Pilot Experiment (MEGAPIE) to be conducted at the Paul-Scherrer Institute (PSI) the feasibility of a lead-bismuth alloy cooled target for spallation purposes will be demonstrated. Such types of liquid metal cooled targets are under consideration for various concepts of accelerator driven systems (ADS) aimed to transmute nuclear waste in order to reduce the size of a final repository or to generate fast neutrons for applications like neutron tomography etc. A major component of such targets are the pumps, which are necessary to remove the heat from the highly heat loaded window facing the proton beam generated by the accelarator and transporting the heat through the heat exchangers. Since the pumps are merely inaccessible for maintenance during operation electro-magnetic pumps without any rotating parts are preferred compared to mechanical devices. Within this report the general performance features of the electro-magnetic tandem pump for the MEGAPIE target being designed and constructed at the Institute of Physics in Riga are reviewed and recalculated using a two-dimensional approach. Additionally the power balance as well as the velocity profile and the operational characteristics are discussed. The main results of this report are: a.) Both the main pump as well as the bypass pump will very likely attain the required flow rates. They are in principle capable to reach 27.5m 3 /h at a pressure head of 0.3bars for the main pump and 2.2m 3 /h at a pressure head of 0.71bars for bypass pump. This corresponds to a safety margin of 50%. b.) The power limiting variable is the input current which should not exceed 37 Amperes for each pump in order to keep the copper winding temperature within acceptable limits. c.) The overall pump efficiency is extremely weak. It accounts for the main pump to 1.18% and for the bypass unit to only 0.249%. Both is caused by an initially in the design chosen very high slip ratio s which is far above s=0.5. The second major reason leading to this weak efficiency is the improper design of the end regions (of in- and outlet), where most of the input power is only spent as eddy loss currents. A proper design here without any change of the pump channel could lead to an order of magnitude higher efficiencies. d.) The relatively large gap in the main pump causes a pressure variation through the gap in radial direction leading to a non-uniform magnetic induction, which itself leads to a non-uniform velocity profile. This profile has been calculated for nominal conditions. It should be proofed with a computational fluid dynamics code (CFD) if with this profile at the pump outlet the afterwards connected heat exchanger is capable to remove the desired power. e.) The time scales being given in the report of Platacis and Freibergs (2002) for heating up the pump before filling it with the PbBi do only account for the wall currents and, hence, they are significantly too long. If they would be conducted in the way proposed the pump will very likely be damaged. A more secure way for controlling the up-heating procedure is to use only about 10% of the nominal power and to wait longer times in order to get a more homogeneous temperature distribution in the pump. Therefore, the minimum amount of control thermocouples for each pump are 7. The exact location is given in this report (c.f. fig. 6.1). f.) In order to avoid misreadings of the pump temperatures by the existing magnetic field and the appearing temperature gradients Copper-Konstantan thermocouples should by used. g.) A fixation of the iron sheets by means of a mechanical clamping or welding should be used in order to prevent vibrations. h.) The calculated spaces for thermal expansions in radial of at least 0.85mm and axial of at least 0.2mm should be existent both on the inductor side and the core side due to the different temperatures within the pump. The drawings show spaces but the distances where not given. i.) Estimates about the response tim

Comparison of FWM- and XPM-induced crosstalk using the volterra series transfer function method

New analytical tools to calculate the variance due to cross-phase modulation (XPM) and four-wave mixing (FWM) induced intensity distortion are derived based on the Volterra series transfer function method. The analysis for both the XPM and FWM effects is based on the same system configuration with a continuous-wave (CW) probe channel plus modulated pump channels, which makes possible a fair comparison between the two nonlinear effects. Effective ways to reduce the XPM- and FWM-induced intensity distortion are given. The new results on the variance of the nonlinearity-induced intensity fluctuation also make it possible to study both synchronous wavelength-division multiplexing (WDM) systems with fixed channel delays and asynchronous WDM systems with random channel delays. The new analytical results provide accurate and efficient ways for system parameter optimization to reduce these two nonlinear effects.

Functional role of the N-terminus of Na +,K +-ATPase α-subunit as an inactivation gate of palytoxin-induced pump channel

The N-terminus of the Na +,K +-ATPase α-subunit shows some homology to that of Shaker-B K + channels; the latter has been shown to mediate the N-type channel inactivation in a ball-and-chain mechanism. When the Torpedo Na +,K +-ATPase is expressed in Xenopus oocytes and the pump is transformed into an ion channel with palytoxin (PTX), the channel exhibits a time-dependent inactivation gating at positive potentials. The inactivation gating is eliminated when the N-terminus is truncated by deleting the first 35 amino acids after the initial methionine. The inactivation gating is restored when a synthetic N-terminal peptide is applied to the truncated pumps at the intracellular surface. Truncated pumps generate no electrogenic current and exhibit an altered stoichiometry for active transport. Thus, the N-terminus of the α-subunit appears to act like an inactivation gate and performs a critical step in the Na +,K +-ATPase pumping function.

Signal transmission analysis of backward-pumped fiber Raman amplifiers

We present a fast numerical method for the design and transmission analysis of backward-pumped fiber Raman amplifiers (FRAs). Our method groups pump-and-signal channels to exclude unimportant spectral bands between the groups during the simulation. Neglecting the weak pump channel modulation by the counterpropagating signal channels, we find the signal and pump evolutions from the FRA input toward the FRA output. The initial conditions at the FRA input may be obtained from the conventional power analysis. Our method may provide amplifier-induced transmission penalties that become increasingly important in high bit rate long-haul wavelength-division multiplexing transmissions.