Pump Density Research Articles

Drilling fluid loss control via implementing the FMI and DSI logs to protect environment

Implementing the drilling fluids in drilling operations is of paramount importance owing to the variety of applications and benefits they provide. Materials added to drilling fluid could cause numerous environmental problems in soil and water resources, and these problems are more pronounced in offshore as compared to land fields. Heavy metals such as mercury, barium, arsenic, lead, and nickel exist in drilling fluid, which bring detrimental damages to the environment. Moreover, heavy metals exist in oil-based muds due to presence of oil where their nickel and vanadium are much greater than other heavy metals. Additive materials and heavy metals existing in drilling fluid could pose irreparable environmental damage if fluid loss into the formation occurs. Regarding to the fact that drilling fluid loss occurs via the open fractures in the wellbore, the main aim of this study is to evaluation of wellbore fractures via implementing the FMI log and fracturing pressure using the slowness of compressional and shear waves. A total of 61 fractures in Dalan formation and 72 fractures in Kangan formation are interpreted and fracturing pressure for these formations, ranges between 8400 and 9450 psi. Implementing the results obtained from this study, drilling fluid loss into the formation and subsequent environmental damage could be prohibited via controlling the pumping pressure and density variation of drilling fluid in accordance with the formation fracturing pressure.

Improving the Performance of a CH3NH3PbBr3 Perovskite Microrod Laser through Hybridization with Few‐Layered Graphene

Lead halide perovskite micro‐ and nanolasers have been thoroughly studied in past two years. Record low threshold and high Q factor have been demonstrated in perovskite nanorods. However, most of the researches are focusing on the observations of lasing actions. The performances of perovskite microlasers at high excitation power, which are supposed to be more important in applications such as displays and laser sources, have not been studied. Herein the perovskite microlasers have been studied at high pumping density and the mechanism to improve their performances has been explored. Different from the typical gain saturation, the perovskite microlaser shows a flat or a negative power slope at high pumping density and its total output power is thus limited. By transferring CH3NH3PbBr3 perovskite microrod onto a few‐layered graphene slice, it is found that the total output intensity has been significantly enhanced more than four times and the threshold is reduced around 20%. The following experiments show that the improvements are attributed to the electron acceptor property of graphene and the long carrier diffusion length. As the electrons are attracted by graphene, the electrons and holes are separated in different regions in the hybrid perovskite/graphene system and thus the Auger recombination at high pumping power can be dramatically reduced. The finding of this study will be important not only for the perovskite lasers but also for other semiconductor lasers.

The effects of Tmc1 Beethoven mutation on mechanotransducer channel function in cochlear hair cells.

Sound stimuli are converted into electrical signals via gating of mechano-electrical transducer (MT) channels in the hair cell stereociliary bundle. The molecular composition of the MT channel is still not fully established, although transmembrane channel-like protein isoform 1 (TMC1) may be one component. We found that in outer hair cells of Beethoven mice containing a M412K point mutation in TMC1, MT channels had a similar unitary conductance to that of wild-type channels but a reduced selectivity for Ca(2+). The Ca(2+)-dependent adaptation that adjusts the operating range of the channel was also impaired in Beethoven mutants, with reduced shifts in the relationship between MT current and hair bundle displacement for adapting steps or after lowering extracellular Ca(2+); these effects may be attributed to the channel's reduced Ca(2+) permeability. Moreover, the density of stereociliary CaATPase pumps for Ca(2+) extrusion was decreased in the mutant. The results suggest that a major component of channel adaptation is regulated by changes in intracellular Ca(2+). Consistent with this idea, the adaptive shift in the current-displacement relationship when hair bundles were bathed in endolymph-like Ca(2+) saline was usually abolished by raising the intracellular Ca(2+) concentration.

Near-Infrared Emission and Photon Energy Upconversion of Two-Dimensional Copper Silicates

BaCuSi4O10 (Han blue), CaCuSi4O10 (Egyptian blue), and SrCuSi4O10 are pigments found in many ancient artifacts all over the world. Behind their brilliant color, we demonstrate here that these ancient pigments are strong candidates for photonic materials due to their bright Stokes and anti-Stokes emissions. These pigments give near-infrared emissions (NIR) from Cu2+ centered at around 930 nm under excitation of 440–800 nm light. This NIR emission can also be produced by pumping using a NIR laser diode. With the rise of pumping density, the emission bandwidth increases notably and stretches to the visible region, giving rise to bright and broadband photon upconversion (UC). This photon UC process is interpreted in terms of laser-driven blackbody radiation from the ancient pigments.

Cardiac glycosides induced toxicity in human cells expressing α1-, α2-, or α3-isoforms of Na-K-ATPase.

The Na+-K+-ATPase is specifically inhibited by cardiac glycosides, some of which may also function as endogenous mammalian hormones. Previous studies using Xenopus oocytes, yeast cells, or purified isoforms demonstrated that affinities of various cardiac glycosides for three isoforms of the Na+-K+-ATPase (α1-α3β1) may differ, a finding with potential clinical implication. The present study investigates isoform selectivity and effects of cardiac glycosides on cultured mammalian cells under more physiological conditions. H1299 cells (non-small cell lung carcinoma) were engineered to express only one α-isoform (α1, α2, or α3) by combining stable transfection of isoforms and silencing endogenous α1. Cardiac glycoside binding was measured by displacement of bound 3H-ouabain. The experiments confirm moderate α1/α3:α2 selectivity of ouabain, moderate α2:α1 selectivity of digoxin, and enhanced α2:α1 selectivity of synthetic derivatives (Katz A, Tal DM, Heller D, Haviv H, Rabah B, Barkana Y, Marcovich AL, Karlish SJD. J Biol Chem 289: 21153-21162, 2014). Relative α2:α1 selectivity of digoxin vs. ouabain was also manifested by enhanced internalization of α2 in response to digoxin. Cellular proliferation assays of H1299 cells confirmed the patterns of α2:α1 selectivity for ouabain, digoxin, and a synthetic derivative and reveal a crucial role of surface pump density on sensitivity to cardiac glycosides. Because cardiac glycosides are being considered as drugs for treatment of cancer, effects of ouabain on proliferation of 12 cancer and noncancer cell lines, with variable plasma membrane expression of α1, have been tested. These demonstrated that sensitivity to ouabain indeed depends linearly on the plasma membrane surface density of Na+-K+-ATPase irrespective of status, malignant or nonmalignant.

Longitudinal and transverse spin dynamics of donor-bound electrons in fluorine-doped ZnSe: Spin inertia versus Hanle effect

The spin dynamics of strongly localized donor-bound electrons in fluorine-doped ZnSe epilayers is studied using pump-probe Kerr rotation techniques. A method exploiting the spin inertia is developed and used to measure the longitudinal spin relaxation time ${T}_{1}$ in a wide range of magnetic fields, temperatures, and pump densities. The ${T}_{1}$ time of the donor-bound electron spin of about $1.6 \ensuremath{\mu}\mathrm{s}$ remains nearly constant for external magnetic fields varied from zero up to 2.5 T (Faraday geometry) and in a temperature range 1.8--45 K. These findings impose severe restrictions on possible spin relaxation mechanisms. In our opinion they allow us to rule out scattering between free and donor-bound electrons, jumping of electrons between different donor centers, scattering between phonons and donor-bound electrons, and with less certainty charge fluctuations in the environment of the donors caused by the 1.5 ps pulsed laser excitation.

Gain-assisted critical coupling for high-performance coherent perfect absorbers.

Balanced radiation and absorption rates of an optical resonator are necessary for coherent perfect light absorption in many active device applications. This balance is referred to as critical coupling condition. We propose a gain-assisted method for exact access to critical coupling conditions without altering any structure parameters. In a coherent absorber with additional internal gain media, critical coupling with arbitrarily high coherent signal extinction can be obtained by continuously tuning optical pumping density. Assuming a surface-plasmon resonance grating covered by a gain layer as a promising architecture, we numerically demonstrate gain-assisted continuous access to its critical coupling point with experimentally probable settings. In addition, the gain tuning further introduces switching of the coherent-absorber's functionality to a conventional lossless beam splitter.

Effect of the modulation of the polariton potential on the polarization instability of stimulated polariton-polariton scattering in planar gaas microcavities

The polarization characteristics of the stimulated polariton-polariton scattering signal under resonance excitation in the vicinity of the inflection point of the polariton dispersion curve are investigated in the absence and in the presence of exciton-potential modulation imposed by a surface acoustic wave. It is found that the spatial modulation of the exciton potential leads to an abrupt decrease in the effective critical pump density above which the polarization of the scattering signal changes. This opens the way for the use of acoustic waves to control the polarization of the stimulated scattering signal in polariton systems.

TECHNOLOGICAL PARAMETERS INFLUENCE OF OILWELLS ON ENERGY CONSUMPTION SUCKER ROD PUMPS

Sucker rod pump units are the primary means of mechanized borehole oil production worldwide. Difficult economic conditions, volatile oil prices and the continued growth of electricity tariffs forced oil producers to develop and implement energy-saving technologies. It is known that the most energy-intensive process at the oil companies is a well mechanized production. The technological process of lifting well fluid is accompanied by loss of energy in the following structural elements: a pump, plunger pair, valve assemblies, rod string, pumping unit, gearbox, motor, control station. The authors have developed a method of determining the relative energy consumption of sucker rod pump units. Pumping unit consumes from electric motor effective power required to lift well fluid. The losses in the motor are determined by efficiency and power factor. The exact definition of the loss in the motor is a difficult task due to the cyclic nature of the load. Cyclical nature of the load is taken into account by using the shape factor, which is determined by watt card. Regulatory relative energy consumption of oil production equipments is defined as the energy consumption on lifting 1 m 3 of well fluid. The main factors affecting the relative power consumption are balanced pumping unit, density and water content of oil, stroke length and frequency of oscillation balance bar. The authors developed a model of the relative energy consumption of sucker rod pumps. The model consists of the subsystems of the effective mechanical power, of the motor efficiency at a given load, the power consumed from the electrical network, taking into account the balance of the pumping unit, the theoretical flow rate, taking into account practical flow rates of depression, productivity, skin-factor and permeability. The developed methodology and model the relative power consumption to be introduced in the software of intelligent control stations for oil well pumps.

Abortive and propagating intracellular calcium waves: analysis from a hybrid model.

The functional properties of inositol(1,4,5)-triphosphate (IP3) receptors allow a variety of intracellular Ca2+ phenomena. In this way, global phenomena, such as propagating and abortive Ca2+ waves, as well as local events such as puffs, have been observed. Several experimental studies suggest that many features of global phenomena (e.g., frequency, amplitude, speed wave) depend on the interplay of biophysical processes such as diffusion, buffering, efflux and influx rates, which in turn depend on parameters such as buffer concentration, Ca2+ pump density, cytosolic IP3 level, and intercluster distance. Besides, it is known that cells are able to modify some of these parameters in order to regulate the Ca2+ signaling. By using a hybrid model, we analyzed different features of the hierarchy of calcium events as a function of two relevant parameters for the calcium signaling, the intercluster distance and the pump strength or intensity. In the space spanned by these two parameters, we found two modes of calcium dynamics, one dominated by abortive calcium waves and the other by propagating waves. Smaller distances between the release sites promote propagating calcium waves, while the increase of the efflux rate makes the transition from propagating to abortive waves occur at lower values of intercluster distance. We determined the frontier between these two modes, in the parameter space defined by the intercluster distance and the pump strength. Furthermore, we found that the velocity of simulated calcium waves accomplishes Luther’s law, and that an effective rate constant for autocatalytic calcium production decays linearly with both the intercluster distance and the pump strength.

Effects of pumping wavelength and pump density on the random laser performance of stoichiometric Nd crystal powders.

Laser slope and threshold properties have been investigated in Nd stoichiometric crystal powders as a function of pump wavelength and pump beam size. Above a given pumped area, the laser slope and the threshold pump energy per unit area are invariant and the known theoretical expressions are well fulfilled. Likewise, the size of the stimulated emission zone as a function of the pump beam area has been measured, also showing a different behavior above or below a given pumped area value which coincides with the one mentioned above. In conclusion, two different operating regimes with different performances are clearly observed as a function of the pump beam area.

Up-conversion luminescence of Y2O3: Yb, Er under 1.55 μm excitation

This study explores a new method to achieve highly efficient red up-conversion luminescence by using Y2O3: Yb, Er pumping with a 1550nm laser diode (Y2O3: Yb, Er@1550nm). The strongest red emission, with a peak situated at 660nm, can be assigned to Er3+ ion 4I9/2→4I15/2 transition. The radiation brightness of Y2O3: Yb, Er@1550nm is comparable to that of Y2O3: Yb, Er under an equivalent 980nm pumping density (Y2O3: Yb, Er@980nm). Y2O3: Yb, Er@1550nm presents a very weak green emission as compared with that of Y2O3: Yb, Er@980nm. Consequently, Y2O3: Yb, Er@1550nm exhibits much better color purity and excellent color stability with increasing pumping power.

Calcium handling in muscle fibres of mice and men: evolutionary adaptation in different species to optimize performance and save energy

Calcium handling in muscle fibres of mice and men: evolutionary adaptation in different species to optimize performance and save energy

Nanoscale elucidation of Na,K-ATPase isoforms in dendritic spines

Abstract Background The dimensions of neuronal synapses suggest that optical super-resolution imaging methods are necessary for thorough investigation of protein distributions and interactions. Nanoscopic evaluation of neuronal samples has presented practical hurdles, but advancing methods are making synaptic protein topology and quantification measurements feasible. This work explores the application of Photoactivated Localization Microscopy (PALM) pointillistic super-resolution imaging for investigation of the membrane bound sodium pump, the Na,K-ATPase, in matured neurons. Results Two isoforms of the sodium pump (ATP1a1 and ATP1a3) were studied in cultured neurons using the PALM-compatible fluorescent proteins PAGFP and mEos. Nanoscopic imaging reveals a compartmentalized distribution of sodium pumps in dendritic spines. Several nanoclusters of pumps are typically found in the spine head and fewer in the spine neck. The density of sodium pumps was estimated from a quantification of detected single molecules at 450–650 pump copies/μm2 in the spine heads. Conclusions We have utilized PALM for dissection of nanoscale localization in mature cultured neurons and demonstrated similar topology and quantification estimates with PAGFP and mEos. PALM topology assessments of the sodium pump appeared similar to previous STED studies, though quantification estimates varied, implying that labeling strategies, sample analysis and choice of nanoscopic imaging method can be critical factors for correct molecular quantification.

Growth and Optimization of 2-μm InGaSb/AlGaSb Quantum-Well-Based VECSELs on GaAs/AlGaAs DBRs

We report the growth of optically pumped vertical-external-cavity surface-emitting lasers (VECSELs) based on InGaSb/AlGaSb quantum wells grown on GaAs/AlGaAs distributed Bragg reflectors (DBRs). The 7.78% lattice mismatch between GaSb and GaAs is accommodated by an array of 90° misfit dislocations at the interface. This results in spontaneous relaxation of the GaSb epilayer and also significantly reduces the threading dislocation density. The VECSELs are operated in both pulsed (with 340-W peak output power) and continuous wave mode (with 0.12-W peak output power). We investigate the effects of the GaSb/GaAs interface by comparing the lattice mismatched III-Sb VECSEL grown on GaAs/AlGaAs DBRs to a lattice matched III-Sb VECSEL grown on GaSb/AlAsSb DBRs. The lattice matched VECSEL outperforms the lattice mismatched VECSEL in terms of threshold pump density, efficiency, and maximum continuous-wave output power. This can be attributed to the presence of threading dislocations throughout the active region of the mismatched VECSEL, which is confirmed by cross-sectional transmission electron microscopy. The optical properties of the III-Sb active regions are characterized by time-resolved photoluminescence, which can be used to optimize the IMF interface.

Lasing and longitudinal cavity modes in photo-pumped deep ultraviolet AlGaN heterostructures

To unambiguously distinguish lasing from super luminescence, key elements of lasing such as longitudinal cavity modes with narrow line-width, polarized emission, and elliptically shaped far-field pattern, need to be demonstrated at the same time. Here, we show transverse electric polarized lasing at 280.8 nm and 263.9 nm for AlGaN based multi-quantum-wells and double heterojunction structures fabricated on single crystalline AlN substrates. An elliptically shaped far-field pattern was recorded when pumped above threshold. With cavities shorter than 200 μm, well-defined, equally spaced longitudinal modes with line widths as narrow as 0.014 nm were observed. The low threshold pumping density of 84 kW/cm2 suggests that the electrically pumped sub-300 nm ultraviolet laser diodes are imminent.

Room-temperature stimulated emission in two-dimensional MgxZn1−xO/ZnO heterostructures under optical pumping

Two series of MgxZn1−xO/ZnO multiple quantum wells with 18 and 27 at.% of magnesium content in the barrier layers and well widths Lw from 1 to 20 nm have been grown by the pulsed laser deposition method. Stimulated emission is observed in the photoluminescence (PL) spectra excited by the pulsed laser (λexc = 248 nm). The pump density threshold of stimulated emission depends nonmonotonically on the well width, which is associated with an increase of the internal quantum efficiency of the two-dimensional structures caused by a reduction of the radiative lifetime of excitons with decreasing well width, as has been shown by the time-resolved photoluminescence spectra analysis. A minimum value of the radiative lifetime τr = 355 ps was obtained for the Mg0.27Zn0.73O/ZnO MQW with a well width Lw = 2.6 nm. It has been established that the deep energy levels produced by active surface states with carrier recombination forming the green band in the PL spectrum (λGB = 510 nm) are metastable.

Color control and white upconversion luminescence of LaOF:Ln3+ (Ln = Yb, Er, Tm) nanocrystals prepared by the sol–gel Pechini method

A series of Yb(3+)-Er(3+) and Yb(3+)-Er(3+)-Tm(3+) codoped LaOF nanocrystals were synthesized via a modified sol-gel Pechini method. The phases and morphologies as well as the luminescence properties of the as-prepared samples were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and upconversion luminescence (UCL) spectra, respectively. Under 980 nm near infrared (NIR) excitation, the UCL properties and the corresponding luminescent colors of the samples could be precisely modulated by changing the annealing temperatures, the dopant concentrations and the pump densities. By regulating the intensities of blue, green and red emissions in Yb(3+)-Er(3+)-Tm(3+) codoped LaOF nanocrystals, an ideal white upconversion luminescence with chromaticity coordinates of (0.331, 0.368) is obtained in La0.885Yb0.1Er0.01Tm0.005OF nanocrystals for the first time. The blue, green and red components of the white light come from the (1)G4 → (3)H6 transition of Tm(3+), (2)H11/2/(4)S3/2 → (4)I15/2 transitions of Er(3+) and (4)F9/2 → (4)I15/2 transition of the Er(3+) ions, respectively. The possible physical mechanisms involved in the different upconversion processes were discussed in detail.

Power scaling limitations in quasi-three level thin gain lasers

In this paper, based on a self-consistent numerical method, the re-absorption and concentration quenching effects on Yb:YAG thin disc laser operation is simulated. These effects are evaluated taking into account the spectroscopic, population and mechanical factors dependent on the doping concentration and temperature. A photon tracing code and finite element analysis is utilized to calculate the absorbed pump density and the temperature distribution, respectively. This model shows that the optical efficiency is affected by re-absorption losses and fluorescence concentration quenching and drops at concentrations greater than 28%. It is concluded that the optimum thickness decreases exponentially with doping concentration. The temperature has most influences on the lasing action through the Boltzmann's redistribution. The predicted laser output power exceeds the actual value if the temperature and doping concentration dependency of laser parameters are neglected. Modeling results are accurately in agreement with experimental data. Through variation of laser designing parameters, power scaling laws of thin disc laser has been derived.

Influences of temperature, oxidative stress, and phosphorylation on binding of heat shock proteins in skeletal muscle fibers

Heat shock proteins (HSPs) help maintain cellular function in stressful situations, but the processes controlling their interactions with target proteins are not well defined. This study examined the binding of HSP72, HSP25, and αB-crystallin in skeletal muscle fibers following various stresses. Rat soleus (SOL) and extensor digitorum longus (EDL) muscles were subjected in vitro to heat stress or strongly fatiguing stimulation. Superficial fibers were "skinned" by microdissection and HSP diffusibility assessed from the extent of washout following 10- to 30 min exposure to a physiological intracellular solution. In fibers from nonstressed (control) SOL muscle, >80% of each HSP is readily diffusible. However, after heating a muscle to 40°C for 30 min ∼95% of HSP25 and αB-crystallin becomes tightly bound at nonmembranous myofibrillar sites, whereas HSP72 bound at membranous sites only after heat treatment to ≥44°C. The ratio of reduced to oxidized cytoplasmic glutathione (GSH:GSSG) decreased approximately two- and fourfold after heating muscles to 40° and 45°C, respectively. The reducing agent dithiothreitol reversed HSP72 binding in heated muscles but had no effect on the other HSPs. Intense in vitro stimulation of SOL muscles, sufficient to elicit substantial oxidation-related loss of maximum force and approximately fourfold decrease in the GSH:GSSG ratio, had no effect on diffusibility of any of the HSPs. When skinned fibers from heat-treated muscles were bathed with additional exogenous HSP72, total binding increased approximately two- and 10-fold, respectively, in SOL and EDL fibers, possibly reflective of the relative sarco(endo)plasmic reticulum Ca(2+)-ATPase pump densities in the two fiber types. Phosphorylation at Ser59 on αB-crystallin and Ser85 on HSP25 increased with heat treatment but did not appear to determine HSP binding. The findings highlight major differences in the processes controlling binding of HSP72 and the two small HSPs. Binding was not directly related to cytoplasmic oxidative status, but oxidation of cysteine residues influenced HSP72 binding.