Buffer Reservoir Research Articles

Intensity noise cancellation in solid-state laser at 1.5 μm using SHG depletion as a buffer reservoir.

An absorption mechanism based on second-harmonic generation (SHG) is successfully implemented as a buffer reservoir in a solid-state Er,Yb:Glass laser emitting at the telecom wavelength. We show that a slight absorption mechanism based on SHG rate conversion of 0.016% using a beta barium borate crystal enables the canceling out of the excess intensity noise at the relaxation oscillation frequency, i.e., 35dB reduction, as well as canceling the amplified spontaneous emission beating at the free spectral range resonances of the laser lying in the gigahertz range. Laser robustness is discussed.

Recording Synaptic Plasticity in Acute Hippocampal Slices Maintained in a Small-volume Recycling-, Perfusion-, and Submersion-type Chamber System.

Even though experiments on brain slices have been in use since 1951, problems remain that reduce the probability of achieving a stable and successful analysis of synaptic transmission modulation when performing field potential or intracellular recordings. This manuscript describes methodological aspects that might be helpful in improving experimental conditions for the maintenance of acute brain slices and for recording field excitatory postsynaptic potentials in a commercially available submersion chamber with an outflow-carbogenation unit. The outflow-carbogenation helps to stabilize the oxygen level in experiments that rely on the recycling of a small buffer reservoir to enhance the cost-efficiency of drug experiments. In addition, the manuscript presents representative experiments that examine the effects of different carbogenation modes and stimulation paradigms on the activity-dependent synaptic plasticity of synaptic transmission.

Predominance of two dimensional (2D) Mn2O3 nanowalls thin film for high performance electrochemical supercapacitors

Well-defined, organized and highly dense Mn2O3 nanowalls are synthesized on nickel (Ni) foam by a facile hydrothermal route and utilize as efficient electro-active electrode for the electrochemical supercapacitors. The crystal structure and quality studies by X-rays diffraction (XRD) and Raman spectroscopy describe the formation of orthorhombic Mn2O3 phases. Uniform and well-organized nanowalls like morphology are grown on the Ni foam in the high aspect ratios with the average wall thickness of 20–30nm. The highly dense network of Mn2O3 nanowalls in electrochemical system could favor the better electrolyte penetration and supply the ion buffer reservoir to assure the constant supply of electrolyte. From cyclicvoltammetry analysis, the fabricated supercapacitor with Mn2O3 nanowalls electrode accomplishes the excellent capacitance of 480Fg−1 at 10mVs−1 in 6M KOH electrolyte. Interestingly, similar specific capacitance of 461Fg−1 at 0.5Ag−1 has obtained from the galvanostat charge-discharge measurements of fabricated supercapacitor with Mn2O3 nanowalls electrode. The grown Mn2O3 nanowalls electrode show the fantabulous cycling stability by maintaining the retention ratio 82% after 5000 cycles. This work paves a new and effective way for the direct preparation of nanowalls-like Mn2O3 thin film to achieve high performance electrochemical supercapacitors.

Mathematical Modeling of Rotary Blood Pumps in a Pulsatile In Vitro Flow Environment.

Nowadays, sacrificing animals to develop medical devices and receive regulatory approval has become more common, which increases ethical concerns. Although in vivo tests are necessary for development and evaluation of new devices, nonetheless, with appropriate in vitro setups and mathematical models, a part of the validation process can be performed using these models to reduce the number of sacrificed animals. The main aim of this study is to present a mathematical model simulating the hydrodynamic function of a rotary blood pump (RBP) in a pulsatile in vitro flow environment. This model relates the pressure head of the RBP to the flow rate, rotational speed, and time derivatives of flow rate and rotational speed. To identify the model parameters, an in vitro setup was constructed consisting of a piston pump, a compliance chamber, a throttle, a buffer reservoir, and the CentriMag RBP. A 40% glycerin-water mixture as a blood analog fluid and deionized water were used in the hydraulic circuit to investigate the effect of viscosity and density of the working fluid on the model parameters. First, model variables were physically measured and digitally acquired. Second, an identification algorithm based on regression analysis was used to derive the model parameters. Third, the completed model was validated with a totally different set of in vitro data. The model is usable for both mathematical simulations of the interaction between the pump and heart and indirect pressure measurement in a clinical context.

Fish recolonization of a lowland river with non-buffered storm water discharges but with abated pollution from a large municipality

Water pollution from industrial Metro Łódź (ML), Poland, made the Ner River almost fishless in its middle-lower course for most of the 19th and 20th century. The new sewage treatment plant of ML and reduction of industry have caused pollution abatement there since the 1990s. As a result, the Ner became repopulated, which was shown by fish samples collected along its course in 2000–2012. Multivariate statistical methods helped distinguish unpolluted (I and II, in the upper course), and recovered (III, IV and V, in the middle-lower course) sections of the river. Historical and present data indicated that section III (downstream of ML) recovered least, both before and during the study. Section V (outflow one) recovered most and its fish fauna (almost exclusively native) now displays high and stable biomass, abundance and species richness, including those of obligatory riverine species. Non-native Prussian carp's dominance followed the river degradation gradient, i.e. was highest in section III, and in section V declined to almost absence. This study shows that the revival of native fish fauna seems to be a method of restricting the dominance of this highly tolerant species. Despite the abatement, storm events are very harmful to fish (mostly in section III), because the Ner discharge may then increase manifold and all storm water is drained by the ML combined sewer system to the Ner in several hours. Other stressors are numerous dams and desorption of pollutants from sediment in the middle Ner, and perhaps pollutant inflow from agriculture or local urban areas. Some moderation of storm impact on water entering the Ner from ML by constructing buffer reservoirs would probably cause further fish recovery in section III.

Reduction of residual excess noise in class-A lasers using two-photon absorption.

We demonstrate experimentally a significant reduction of the remaining excess intensity noise in a class-A semi-conductor laser. This is obtained by inserting into the laser cavity a buffer reservoir mechanism based on two-photon absorption in GaAs. The excess noise peaks at the laser-free spectral range, induced by the beating between the lasing mode and the amplified spontaneous emission in the adjacent non-oscillating modes, is reduced by 20 dB, while preserving the class-A dynamical behavior of the laser cavity.

In-phase and antiphase self-intensity regulated dual-frequency laser using two-photon absorption.

A 25 dB reduction of resonant intensity noise spectra is experimentally demonstrated for both the antiphase and in-phase relaxation oscillations of a dual-frequency solid-state laser operating at telecommunication wavelengths. Experimental results demonstrate that incorporation of an intracavity two-photon absorber that acts as a buffer reservoir reduces efficiently the in-phase noise contribution, while it is somewhat ineffective in lowering the antiphase noise contributions. A slight spatial separation of the two modes in the nonlinear two-photon absorber reduces the antiphase resonant intensity noise component. These experimental results provide a new approach in the design of ultra-low noise dual-frequency solid-state lasers.

Third-generation electrokinetically pumped sheath-flow nanospray interface with improved stability and sensitivity for automated capillary zone electrophoresis-mass spectrometry analysis of complex proteome digests.

We have reported a set of electrokinetically pumped sheath flow nanoelectrospray interfaces to couple capillary zone electrophoresis with mass spectrometry. A separation capillary is threaded through a cross into a glass emitter. A side arm provides fluidic contact with a sheath buffer reservoir that is connected to a power supply. The potential applied to the sheath buffer drives electro-osmosis in the emitter to pump the sheath fluid at nanoliter per minute rates. Our first-generation interface placed a flat-tipped capillary in the emitter. Sensitivity was inversely related to orifice size and to the distance from the capillary tip to the emitter orifice. A second-generation interface used a capillary with an etched tip that allowed the capillary exit to approach within a few hundred micrometers of the emitter orifice, resulting in a significant increase in sensitivity. In both the first- and second-generation interfaces, the emitter diameter was typically 8 μm; these narrow orifices were susceptible to plugging and tended to have limited lifetime. We now report a third-generation interface that employs a larger diameter emitter orifice with very short distance between the capillary tip and the emitter orifice. This modified interface is much more robust and produces much longer lifetime than our previous designs with no loss in sensitivity. We evaluated the third-generation interface for a 5000 min (127 runs, 3.5 days) repetitive analysis of bovine serum albumin digest using an uncoated capillary. We observed a 10% relative standard deviation in peak area, an average of 160,000 theoretical plates, and very low carry-over (much less than 1%). We employed a linear-polyacrylamide (LPA)-coated capillary for single-shot, bottom-up proteomic analysis of 300 ng of Xenopus laevis fertilized egg proteome digest and identified 1249 protein groups and 4038 peptides in a 110 min separation using an LTQ-Orbitrap Velos mass spectrometer; peak capacity was ∼330. The proteome data set using this third-generation interface-based CZE-MS/MS is similar in size to that generated using a commercial ultraperformance liquid chromatographic analysis of the same sample with the same mass spectrometer and similar analysis time.

Noise reduction in solid-state lasers using a SHG-based buffer reservoir.

The cancellation of resonant intensity noise, from a few kHz up to several GHz, is reported using a second-harmonic generation (SHG) buffer reservoir in a Nd:YAG solid-state laser. This approach is shown to be well suited and easily optimizable for reducing the excess noise lying at the laser relaxation oscillations as well as that originating from the beating between the lasing mode and nonlasing adjacent longitudinal modes. A thorough analysis of noise spectra of both laser and SHG signals confirms definitely that noise reduction is a consequence of a deep laser dynamics modification rather than noise evacuation mechanism.

Highly dispersed Mn2O3 microspheres: Facile solvothermal synthesis and their application as Li-ion battery anodes

Nanostructured transition metal oxides are promising alternative anodes for lithium ion batteries. Li-ion storage performance is expected to improve if high packing density energy particles are available. Herein, Mn2O3 microspheres with a ca. 18μm diameter and a tapped density of 1.33g/cm3 were synthesized by a facile solvothermal–thermal coversion route. Spherical MnCO3 precursors were obtained through solvothermal treatment and they decomposed and converted into Mn2O3 microspheres at an annealing temperature of 700°C. The Mn2O3 microspheres consisted of Mn2O3 nanoparticles with an average 40nm diameter. These porous Mn2O3 microspheres allow good electrolyte penetration and provide an ion buffer reservoir to ensure a constant electrolyte supply. The Mn2O3 microspheres have reversible capacities of 590 and 320mAh/g at 50 and 400mA/g, respectively. We thus report an efficient route for the fabrication of energy particles for advanced energy storage.

Dynamics from seconds to hours in Hodgkin-Huxley model with time-dependent ion concentrations and buffer reservoirs.

The classical Hodgkin-Huxley (HH) model neglects the time-dependence of ion concentrations in spiking dynamics. The dynamics is therefore limited to a time scale of milliseconds, which is determined by the membrane capacitance multiplied by the resistance of the ion channels, and by the gating time constants. We study slow dynamics in an extended HH framework that includes time-dependent ion concentrations, pumps, and buffers. Fluxes across the neuronal membrane change intra- and extracellular ion concentrations, whereby the latter can also change through contact to reservoirs in the surroundings. Ion gain and loss of the system is identified as a bifurcation parameter whose essential importance was not realized in earlier studies. Our systematic study of the bifurcation structure and thus the phase space structure helps to understand activation and inhibition of a new excitability in ion homeostasis which emerges in such extended models. Also modulatory mechanisms that regulate the spiking rate can be explained by bifurcations. The dynamics on three distinct slow times scales is determined by the cell volume-to-surface-area ratio and the membrane permeability (seconds), the buffer time constants (tens of seconds), and the slower backward buffering (minutes to hours). The modulatory dynamics and the newly emerging excitable dynamics corresponds to pathological conditions observed in epileptiform burst activity, and spreading depression in migraine aura and stroke, respectively.

Buffer reservoir approach for cancellation of laser resonant noises.

The introduction of a buffer reservoir mechanism with optimized time-constants and cross sections in a laser system enables breaking any resonant exchange between the population inversion and photon population over an extremely wide bandwidth. The associated noise cancellation, including the excess noise at relaxation oscillations and spontaneous-signal beating, is experimentally evidenced up to 16 GHz in an Er,Yb laser comprising a GaAs two-photon absorber. Such approach is shown to preserve the laser linewidth quality and is advantageously implemented for optical distribution of frequency references.

Simulation of oxidative stress of guanosine and 8-oxo-7,8-dihydroguanosine by electrochemically assisted injection–capillary electrophoresis–mass spectrometry

Oxidative stress plays a crucial role in DNA and RNA damage within biological cells. As a consequence, mutations of DNA can occur, leading to disorders like cancer and neurodegenerative and cardiovascular diseases. The oxidative attack of guanosine and 8-oxo-7,8-dihydroguanosine is simulated by electrochemistry coupled to capillary electrophoresis-mass spectrometry. The electrochemical conversion of the compound of interest is implemented in the injection protocol termed electrochemically assisted injection (EAI). In this way, oxidation products of guanosine can be generated electrochemically, separated by capillary electrophoresis, and detected by electrospray ionization time-of-flight mass spectrometry (EAI-CE-MS). A fully automated laboratory-made EAI cell with an integrated buffer reservoir and a compartment holding screen-printed electrodes is used for the injection. In this study, parameters like pH of the sample solution and the redox potential applied during the injection were investigated in terms of corresponding formation of well-known markers of DNA damage. The important product species, 8-oxo-7,8-dihydroguanosine, was investigated in a separate study to distinguish between primary and secondary oxidation products. A comparison of product species formed under alkaline, neutral, and acidic conditions is presented. To compare real biological systems with an analytical approach for simulation of oxidative stress, it is desirable to have a well-defined control over the redox potential and to use solutions, which are close to physiological conditions. In contrast to typical HPLC-MS protocols, the hyphenation of EAI, CE, and MS enables the generation and separation of species involved without the use of organic solvents. Thus, information of the electrochemical behavior of the nucleoside guanosine as well as the primary oxidation product 8-oxo-7,8-dihydroguanosine can be characterized under conditions close to the physiological situation. In addition, the migration behavior found in CE separations of product species can be used to identify compounds if several possible species have the same mass-to-charge values determined by MS detection.

Tin Anode for Sodium-Ion Batteries Using Natural Wood Fiber as a Mechanical Buffer and Electrolyte Reservoir

Sodium (Na)-ion batteries offer an attractive option for low cost grid scale storage due to the abundance of Na. Tin (Sn) is touted as a high capacity anode for Na-ion batteries with a high theoretical capacity of 847 mAh/g, but it has several limitations such as large volume expansion with cycling, slow kinetics, and unstable solid electrolyte interphase (SEI) formation. In this article, we demonstrate that an anode consisting of a Sn thin film deposited on a hierarchical wood fiber substrate simultaneously addresses all the challenges associated with Sn anodes. The soft nature of wood fibers effectively releases the mechanical stresses associated with the sodiation process, and the mesoporous structure functions as an electrolyte reservoir that allows for ion transport through the outer and inner surface of the fiber. These properties are confirmed experimentally and computationally. A stable cycling performance of 400 cycles with an initial capacity of 339 mAh/g is demonstrated; a significant improvement over other reported Sn nanostructures. The soft and mesoporous wood fiber substrate can be utilized as a new platform for low cost Na-ion batteries.

Development and characterization of a novel semiautomated arrangement for electrochemically assisted injection in combination with capillary electrophoresis time‐of‐flight mass spectrometry

Electrochemically assisted injection (EAI) is an attractive injection concept for CE that enables the separation of neutral analytes via electrochemical generation of charged species during the injection process. A new semiautomated EAI configuration was developed and applied in conjunction with CE-MS (EAI-CE-MS). The EAI cell arrangement consists of an integrated buffer reservoir for CE separations and a compartment holding screen-printed electrodes. A drop of sample solution (50 μL) was sufficient to cover the three-electrode structures. A piezo motor provided a fast and precise capillary positioning over the screen-printed electrode assembly. Using ferrocene methanol as a model system, the EAI arrangement was characterized regarding coulometric efficiency, precision, and sensitivity of electrospray ionization-time-of-flight-MS. The formation of the cationic oxidation product of ferrocene methanol enhanced the sensitivity of CE-MS determination by two orders of magnitude and the electrochemically formed product showed a migration time corresponding to its individual electrophoretic mobility. Preliminary studies of EAI-CE-MS in the field of the analysis of nitroaromatic compounds were carried out. The formation of corresponding hydroxylamines and amines paved the way for selective and sensitive CE-MS determinations without the need of adding surfactants to the electrophoresis buffer.

Quantitative assessment of flow and electric fields for electrophoretic focusing at a converging channel entrance with interfacial electrode

The electric field and flow field gradients near an electrified converging channel are amenable to separating and focusing specific classes of electrokinetic material, but the detailed local electric field and flow dynamics in this region have not been thoroughly investigated. Finite elemental analysis was used to develop a model of a buffer reservoir connected to a smaller channel to simulate the electrophoretic and flow velocities (which correspond directly to the respective electric and flow fields) at a converging entrance. A detailed PTV (Particle Tracking Velocimetry) study using charged fluorescent microspheres was performed to assess the model validity both in the absence and presence of an applied electric field. The predicted flow velocity gradient from the model agreed with the PTV data when no electric field was present. Once the additional forces that act on the large particles required for tracing (dielectrophoresis) were included, the model accurately described the velocity of the charged particles in electric fields.

ABOUT CALCULATING FLOODWATER FILTER SPILLWAYS OPERATING AT VARIABLE PRESSURE

In order to reduce flood peaks, environmental and economic risks it is offered to build buffer reservoirs. The approximate theoretically proved formula for calculating the capacity of the filter spillway at variable pressure has been derived.

Paper-Based Analytical Device for Electrochemical Flow-Injection Analysis of Glucose in Urine

This article describes a new design for a paper-based electrochemical system for flow-injection analysis. Capillary wicking facilitates a gravity-driven flow of buffer solution continuously through paper and nitrocellulose, from a buffer reservoir at one end of the device to a sink at the other. A difference in height between the reservoir and the sink leads to a continuous and constant flow. The nitrocellulose lies horizontally on a working electrode, which consists of a thin platinum layer deposited on a solid support. The counter and reference electrodes are strategically positioned upstream in the buffer reservoir. A simple pipetting device was developed for reliable application of (sub)microliter volumes of sample without the need of commercial micropipets; this device did not damage the nitrocellulose membrane. Demonstration of the system for the determination of the concentration of glucose in urine resulted in a noninvasive, quantitative assay that could be used for diagnosis and monitoring of diabetes. This method does not require disposable test strips, with enzyme and electrodes, that are thrown away after each measurement. Because of its low cost, this system could be used in medical environments that are resource-limited.

On a mean reverting dividend strategy with Brownian motion

In actuarial risk theory, the introduction of dividend pay-outs in surplus models goes back to de Finetti (1957). Dividend strategies that can be found in the literature often yield pay-out patterns that are inconsistent with actual practice. One issue is the high variability of the dividend payment rates over time. We aim at addressing that problem by specifying a dividend strategy that yields stable dividend pay-outs over time.In this paper, we model the surplus of a company with a Brownian risk model. Dividends are paid at a constant rate g of the company’s modified surplus (after distribution of dividends), which operates as a buffer reservoir to yield a regular flow of shareholders’ income. The dividend payment rate reverts around the drift of the original process μ, whereas the modified surplus itself reverts around the level l=μ/g.We determine the distribution of the present value of dividends when the surplus process is never absorbed. After introducing an absorbing barrier a (inferior to the initial surplus) and stating the Laplace transform of the time of absorption, we derive the expected present value of dividends until absorption. The latter is then also determined if dividends are not paid whenever the surplus is too close to the absorbing barrier. The calculation of the optimal value of the parameter l (and equivalently g) is discussed. We conclude by comparing both barrier and mean reverting dividend strategies.

On a Mean Reverting Dividend Strategy with Brownian Motion

In actuarial risk theory, the introduction of dividend pay-outs in surplus models goes back to Bruno de Finetti (1957). Dividend strategies that can be found in the literature often yield pay-out patterns that are inconsistent with actual practice. One issue is the high variability of the dividend payment rates over time. We aim at addressing that problem by specifying a dividend strategy that yields stable dividend pay-outs over time.In this paper, we model the surplus of a company with a Brownian risk model. Dividends are paid at a constant rate $g$ of the company's modified surplus (after distribution of dividends), which operates as a buffer reservoir to yield a regular flow of shareholders' income. The dividend payment rate reverts around the drift of the original process $\mu$, whereas the modified surplus itself reverts around the level $l=\mu/g$.We determine the distribution of the present value of dividends when the surplus process is never absorbed. After introducing an absorbing barrier $a$ (inferior to the initial surplus) and stating the Laplace transform of the time of absorption, we derive the expected present value of dividends until absorption. The latter is then also determined if dividends are not paid whenever the surplus is too close to the absorbing barrier. The calculation of the optimal value of the parameter $l$ (and equivalently $g$) is discussed. We conclude by comparing both barrier and mean reverting dividend strategies.