Slow Pumping Research Articles

Proton pumping of mitochondrial complex I: differential activation by analogs of ubiquinone.

As part of the ongoing studies aimed at elucidating the mechanism of the energy conserving function of mitochondrial complex I, NADH: ubiquinone (Q) reductase, we have investigated how short-chain Q analogs activate the proton pumping function of this complex. Using a pH-sensitive fluorescent dye we have monitored both the extent and initial velocity of proton pumping of complex I in submitochondrial particles. The results are consistent with two sites of interaction of Q analogs with complex I, each having different proton pumping capacity. One is the physiological site which leads to a rapid proton pumping and a stoichiometric consumption of NADH associated with the reduction of the most hydrophobic Q analogs. Of these, heptyl-Q appears to be the most efficient substrate in the assay of proton pumping. Q analogs with a short-chain of less than six carbons interact with a second site which drives a slow proton pumping activity associated with NADH oxidation that is overstoichiometric to the reduced quinone acceptor. This activity is also nonphysiological, since hydrophilic Q analogs show little or no respiratory control ratio of their NADH:Q reductase activity, contrary to hydrophobic Q analogs.

Effect of the rate of gadopentetate dimeglumine administration on abdominal vascular and soft-tissue MR imaging enhancement patterns.

To delineate dynamic gadopentetate dimeglumine enhancement profiles within the abdomen as a guide to improve gadolinium-enhanced magnetic resonance (MR) angiography. Fifteen patients (eight women, seven men; aged 19-80 years) underwent fast three-dimensional spoiled gradient-recalled-echo imaging with the keyhole technique during the administration of 0.1 mmol/kg gadopentetate dimeglumine by means of bolus (10-second) injection (n = 5), 60 second injection (n = 5), or slow (120-230-second) pump injection (n = 5). Injection was initiated 10 seconds after imaging began. Regions of interest were constructed within the aorta, inferior vena cava, liver, spleen, renal cortex, muscle, and fat. Inclusion of phantoms of gadopentetate dimeglumine in tubes allowed estimation of intravascular gadolinium concentration. Maximal arterial enhancement occurred with bolus administration; maximal parenchymal organ enhancement, with 60-second injection. Slow pump injection resulted in a longer time to preferential arterial to venous enhancement (120 seconds +/- 14 [+/-standard deviation]) than did bolus (48 seconds +/- 64) or 60-second (88 seconds +/- 39) injections. The peak arterial to venous enhancement ratio was 6.3 +/- 3.3 for the bolus injection, 4.7 +/- 1.6 for the 60-second injection, and 3.3 +/- 1.3 for the slow pump injection. The dynamics and magnitude of abdominal vascular and soft-tissue enhancement are affected by the rate of gadopentetate dimeglumine administration.

Aspects of nitrogen surface chemistry relevant to TiN chemical vapor deposition

NH3 is an important component of many chemical vapor deposition (CVD) processes for TiN films, which are used for diffusion barriers and other applications in microelectronic circuits. In this study, the interaction of NH3 with TiN surfaces is examined with temperature programmed desorption (TPD) and Auger electron spectroscopy. NH3 has two adsorption states on TiN: a chemisorbed state and a multilayer state. A new method for analyzing TPD spectra in systems with slow pumping speeds yields activation energies for desorption for the two states of 24 kcal/mol and 7.3 kcal/mol, respectively. The sticking probability into the chemisorption state is ∼0.06. These results are discussed in the context of TiN CVD. In addition, the high temperature stability of TiN is investigated. TiN decomposes to its elements only after heating to 1300 K, showing that decomposition is unlikely to occur under CVD conditions.

Interacting genes required for pharyngeal excitation by motor neuron MC in Caenorhabditis elegans.

We studied the control of pharyngeal excitation in Caenorhabditis elegans. By laser ablating subsets of the pharyngeal nervous system, we found that the MC neuron type is necessary and probably sufficient for rapid pharyngeal pumping. Electropharyngeograms showed that MC transmits excitatory postsynaptic potentials, suggesting that MC acts as a neurogenic pacemaker for pharyngeal pumping. Mutations in genes required for acetylcholine (ACh) release and an antagonist of the nicotinic ACh receptor (nAChR) reduced pumping rates, suggesting that a nAChR is required for MC transmission. To identify genes required for MC neurotransmission, we screened for mutations that cause slow pumping but no other defects. Mutations in two genes, eat-2 and eat-18, eliminated MC neurotransmission. A gain-of-function eat-18 mutation, ad820sd, and a putative loss-of-function eat-18 mutation, ad1110, both reduced the excitation of pharyngeal muscle in response to the nAChR agonists nicotine and carbachol, suggesting that eat-18 is required for the function of a pharyngeal nAChR. Fourteen recessive mutations in eat-2 fell into five complementation classes. We found allele-specific genetic interactions between eat-2 and eat-18 that correlated with complementation classes of eat-2. We propose that eat-18 and eat-2 function in a multisubunit protein complex involved in the function of a pharyngeal nAChR.

Skeletal muscle overload upregulates the sarcoplasmic reticulum slow calcium pump gene

Functional data suggest that the kinetics of force production and relaxation are slowed in hypertrophied skeletal muscle because of chronic overload. The purpose of this study was to determine whether gene expression of the slow/cardiac isoform of the sarcoplasmic reticulum (SR) Ca(2+)-adenosinetriphosphatase (ATPase) pump is upregulated in overloaded fast-twitch plantaris muscles. Increased active muscle loading was induced in rat plantaris muscles bilaterally by surgical removal of gastrocnemius and soleus muscles. Mass of the plantaris muscle was 80% greater 5 wk after surgery than in age-matched unoperated control rats (P < 0.05). Expression of the slow pump mRNA was 135% greater in hypertrophied muscles, as determined from autoradiograms of Northern blots with use of a cDNA probe specific for the slow/cardiac isoform. A monoclonal antibody (7E6) was used to quantify slow Ca2+ pump in SR vesicles with use of Western blot analysis. Densitometry of blots showed that the relative expression of the slow pump protein was 130% greater in hypertrophied plantaris muscles. Expression of the fast SR Ca2+ pump protein isoform, assessed using monoclonal antibody A52, was 25% less in hypertrophied than in control muscles. The Ca2+ uptake rate and ATPase activity of SR vesicles was approximately 15% lower in hypertrophied plantaris muscles (P < 0.05). Differential phospholamban expression could not account for changes in SR Ca2+ handling, because it could not be detected in rat slow- or fast-twitch skeletal muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

A pulsed iodine photodissociation laser with slow pumping

A construction and exploitation of a comparatively large I photodissociation laser system (Perun) is reported. This system was constructed in cooperation between the Institute of Physics of Czechoslovak Academy of Science in Prague and the Lebedev Institute of Physics of Soviet Academy of Science in Moscow. The laser produces subnanosecond pulses of maximum 50 J and 0·5 ns in duration. Although the pumping time by Xe flashlamps is long enough for an acoustic disturbance released in the active medium to introduce an optical inhomogeneity across the whole cross section of the laser tube, the radiation can be focused in a focal spot of a power density exceeding 1014 W/cm2, enough for meaningful laser target experiments both for a laser plasma production or a modification of solid surfaces. The repetition time of the shots is about 10 min.

Reduction of water aerosol contamination during pumping of a vacuum chamber from atmospheric pressure

The drop in temperature resulting from adiabatic expansion during pumping from atmosphere can cause formation of a dense water aerosol in an ordinary vacuum chamber. The aerosol, consisting of water and impurities, can form rapidly, deposit on a silicon wafer and introduce contamination. In this study a unique thermocouple arrangement has been used to obtain the temperature profile of the gas during the pumping transient. From the temperature profile the maximum degree of saturation was calculated. The distance between adjacent surfaces was decreased until the thermocouple measurements no longer indicated supersaturation. Measurements of water aerosol generation were also made in a chamber in which the wall spacing could be varied. Finally a model for a vacuum load lock has been proposed in which water aerosol will not form adjacent to a silicon wafer. This model proposes that wafer be positioned in the x–y plane, with the pumping port located on the 0,0,z axis. For typical system pumping time constants (V/S=3–6 s), a wafer spacing of ≤0.5 mm will permit normal pumping of the load lock without the added processing time required for nitrogen purging or slow pumping.

Kinetics of iodine photodissociation laser in a free running regime at slow pumping

Systematic analysis of pumping kinetics of iodine photodissociation laser was performed in a free running regime. For a practical example, the A 3 amplifier of the iodine laser system PERUN was placed inside a planar resonator and the output energy was calculated in dependence on the mixture composition and compared with the extractable energy in the amplifier case.

Mobilization of colloids in groundwater due to infiltration of water at a coal ash disposal site

We investigated groundwaters in the vicinity of a coal ash site near an electric generating station in the western U.S.A. The purpose of the study was to ascertain why fine particles or colloids appear in some subsurface water samples there. If such fine particles are merely introduced during bailing or pumping operations which suspend otherwise immobile soil colloids, we should exclude these particulate materials from the water samples before analysis intended to quantify what is moving through the aquifer. However, if the colloids were truly suspended and moving with the groundwater flow in situ, then we should includes their contribution to our assessment of the mobile loads. Application of very careful sampling techniques (slow pumping rates, no atmospheric exposure) did not cause the large quantities of colloids observed previously to disappear from well water in which they occured. Additionally, the same sampling procedures did not cause similar abundances of colloids to appear in waters collected from neighboring wells installed and developed in the same manner and in the same geologic strata. Thus we believe sampling artifacts do not explain the colloids' presence in the groundwater samples. On the other hand, the groundwater chemistry and the nature of the suspended colloids (size, composition) strongly suggest these fine particles were suspended and therefore moving with the groundwater flow. At wells exhibiting large amounts of suspended colloids (≈10–100 mg L −1), the water was enriched in CO 2 and depleted in O 2 relative to nearby locations. The colloids were typically between 0.1 and 2 μm in size and were primarily silicates. These results suggest to us that, where infiltrating water is percolating through a site that has been mixed with coal ash, the secondary carbonate mineral in the soils are being dissolved; removal of this cementing carbonate phase may consequently release soil silicate colloids to be carried in the flowing water. Such processes may enhance contaminant transport in groundwater by augmenting the pollutant load moving in the groundwater, and increasing the permeability of the porous medium to pollutant infiltration with water water and/or rainwater.

Movement of Crude Oil in an Experimental Spill on the SEEDS Simulated Pipeline Right-of-way, Fort Norman, N.W.T.

The Studies of the Environmental Effects of Disturbances in the Subarctic (SEEDS) experimental spill was conducted on a simulated pipeline right-of-way and trench. A total of 3273 L of Norman Wells crude oil was released over a 24 h period at a depth of 100 cm in a simulation of a rupture from a subsurface pipeline. Absorptive qualities of the surface vegetation and organic soil layers in an undisturbed forest produce rates of flow and area of contamination values much lower than the SEEDS experiment. Furthermore, the area of contamination (672.75 sq m) was greater than experiments in which the amount of oil and rates of pumping were larger. This resulted from the presence of surface water, a depressed mineral soil-dominated simulated pipeline trench, a cleared right-of-way and slow pumping rates. The SEEDS experiment was a more valid analogue of crude-oil spills associated with a buried pipeline in a subarctic environment.

Frictional stress at a sheared double‐diffusive interface

We describe the results from a laboratory experiment designed to directly measure the stress exerted across a sheared interface which lies between two convecting layers. The two‐layer convection was set up in an annular tank which was rotating slowly so as to provide a basic “store” of angular momentum. Slow radial pumping was used in each layer to drive azimuthal flows, and measurement of the layer velocities provided near‐direct measurements of azimuthal stress. The stress was found to be consistent at all times with that due to molecular viscosity and was independent of the buoyancy flux associated with the convection. The uncertainties of the experimental observations, taken together with the hypothesized stress‐shear relation of Ruddick (1985; equation (1) of this paper), imply a maximum turbulent Prandtl number (absolute value of the ratio of momentum and density diffusivities) of O(1). The experimental results of Ruddick (1985) are reconsidered, and it was concluded that the dependence of internal wave decay rate of buoyancy flux observed in those experiments is a result of the large eddy viscosity in the turbulent mixed layers acting on the strain field of the wave.

Changes of Carbon Isotopes in Atmospheric CO2 of the Kraków Region in the Last Five Years

The Krakow Radiocarbon Laboratory has been measuring isotope composition of atmospheric CO2 and its natural concentration in the Kraków region for the last five years. We have been sampling on a continuous basis in two-week intervals at ca 20m above ground level, close to the center of Kraków. CO2 was sorbed while slow pumping atmospheric air through a molecular sieve. After recovery by heating, the CO2 was converted to benzene and 14C measured in a liquid scintillation spectrometer. In a small portion of CO2 δ13C was determined in a mass spectrometer. Concentration of CO2 was assessed by measurement of the volumes of the sorbed CO2 and the pumped air. A five-year record (1983–1987) reveals a multi-annual linear trend and winter-summer oscillations. Calculated parameters of the regression line (intercept and slope) for the measured δ14C, δ13C and concentration are: 222 (Jan 1983) and −15.5/yr, −9.57% (Jan 1983) and −0.042/yr, 336ppm (Jan 1983) and 1.4ppm/yr, respectively.

Minimization of the photolysis-driven density gradients by slow pumping in the iodine laser amplifier with regard to the beam quality

The UV photolytical pumping of perfluoralkyl iodides C3F7I in the large atomic iodine laser amplifier gives rise to density waves in the gas mixture. The increasing gas temperature during photolysis contributes to the increase of the sound wave velocities. Our calculations of the time interval during which the influence of the oscillating part of the gradient of the refractive index on the focusability was at a minimum was made at a constant gas temperature, which was regarded as a parameter. The results are given in a nomographic chart for various parts of He and SF6 in gas mixture and for various laser tube diameters. The applicability of a heavier buffer gas-argon and a lighter iodine CF3I considering the sound waves velocities was investigated.

100 GW pulsed iodine photodissociation laser system PERUN I

The photodissociation iodine laser system PERUN I is described. The laser generates and amplifies the subnanosecond pulse with the energy about 80 J of the fundamental wavelength 1·315 μm and beam diameter 10 cm. The physical principles of this type of the high power laser are briefly explained and the laser system and its characteristics are described from the physical and technical point of view. Special attention is paid to the realization of such system with the slow optical pumping (≈300 μs).

Kinetics of the photodissociation iodine laser with slow pumping

Systematic calculations of maximum inversion were performed for iodine photodissociation laser in dependence on the mixture composition. The flash-lamp radiation was modelled as emanating from an optically thin Xe plasma. Duration of the pumping pulse is about 300 μs. The sensitivity of the model to the values of kinetic constants was also tested.

Evolution of active-medium perturbations and the focusing of radiation from photodissociation lasers utilizing "slow" pumping

A theoretical investigation was made of the evolution of the radial gradient of the refractive index of the active medium in a photodissociation iodine laser amplifier of nanosecond pulses utilizing slow pumping. Two mechanisms were taken into account in discussing the appearance of an optical inhomogeneity in the medium: the excitation of acoustic waves in the laser cell during pumping in the interior and near the walls. It became clear that the amplitudes of both waves could be made to pass through a minimum simultaneously by choosing the composition of the active gaseous medium. It was concluded, on the basis of the results obtained, that if the pulse being amplified is applied at this moment of time there will be a negligible deterioration in the focusing of the beam.

Characteristics and suppression of flow pulsation from peristaltic pump.

Characteristics of the ripple in the liquid flow through a peristaltic pump was detected quantitatively as pressure fluctuation by using a silicon-pressure sensor. The ripple was associated with the rotation of the squeezing rollers and it could be caused by the periodic release of tension on a flexible tube. At the slow rotation of rollers, i.e., slow pumping speed, the negative pulse on smooth flow was observed, but the ripple on flow was rather complex at the faster rotation, and finally it became periodic. Moreover, ripple was larger for tubes of smaller internal diameters. An air damper consisting of simple glass cylinder was available to reduce these ripples.

Treatment of Malignant Glioma with Neocarzinostatin

The authors evaluated the results of a combined chemoradiotherapy with intracarotid administration of neocarzinostatin (NCS) and radiation in a follow-up study of 26 patients with cerebral malignant glioma. The survival rate was 84.6% at 1 year, and 52.4% at 2 years. Computed tomography scans within 3 months after complete application of the protocols showed complete remission, partial response, minor response, no change, and progressive disease in 11.5%, 38.5%, 19.2%, 23.1%, and 7.7% of patients, respectively. Thus, it was effective in 69.2% of patients. Six (33.3%) out of the 18 patients treated more than 3 years before were alive at full scale (100%) of Karnofsky performance status. Intra-arterial NCS administration was especially appropriate to the malignant glioma, which was fed by unilateral internal carotid artery, and showed marked hypervascularity. Since a preliminary experimental study revealed a synergic effect in cytotoxicity of NCS with radiation, NCS was clinically administered through a slow infusion pump during radiation therapy. The most untoward effect of this method was ocular retinopathy. One third of the cases suffered visual impairment during or after the treatment, when the selective catheterization of the internal carotid artery failed to pass the origin of the ophthalmic artery. NCS seems to be a suitable chemotherapeutic agent for intra-arterial administration, because of the short half-life in the blood (12 seconds), selective cytotoxicity for glioma cells, and increase of the radiation effect. The total dose of NCS should be over 5 mg in order to attain sufficient therapeutic effect.

Optical inhomogeneities in a photodissociation nanosecond-pulse iodine amplifier utilizing slow pumping by ultraviolet radiation

A study was made of the evolution of the refractive index gradient profile of the active medium in a nanosecond-pulse iodine amplifier with a pump duration tp exceeding the period tr of radial acoustic vibrations of the gas in the laser cell. The refractive index gradient was found to be made up of a slow component, monotonically increasing with time, and a rapidly oscillating component associated with the appearance of standing acoustic waves. The former is equivalent to a converging spherical lens and the latter to an aspheric lens. It is shown that only the first cylindrical vibrational mode is excited and that the adverse effects of the acoustic vibrations can be avoided if the pulse is amplified at the moment when the refraction of the aspheric lens vanishes. A comparison between the experimental data and calculations demonstrates that the monotonic component of the refractive index gradient can be explained by the radially inhomogeneous nature of the pumping. The calculated oscillatory component is of much lower intensity than that observed experimentally. This is explained by assuming that the source exciting the acoustic wave is concentrated in the region near the walls. The possibility is mentioned of using pump pulses of tp > tr duration in large-diameter amplifiers having output energies of the order of hundreds of joules.

Thermoconvective instability of longitudinal flow in a vertical layer

An experimental study has been made of convection in a vertical slit cavity heated from below and with longitudinal horizontal forced flow. It was shown that the convective stability of such flow increases appreciably when the velocity of the forced flow is raised. In the case of slow pumping, an increase in the pressure difference leads to superposition on the rectilinear flow of first monotonic convection and then auto-oscillatory convection. At high flow velocities, the instability is immediately of an oscillatory nature. A diagram of the flow regimes is constructed, and the evolution of the supercritical structures described.