Plasma time-dependent plasmas

The electrons follow the oscillations in the electric field, and experience the time-dependent plasma potential. Due to the capacitor through which the RF power is coupled to the electrodes, no dc current flows through the plasma. The ion and electron currents towards each of the electrodes balance each other over one RF period. 

In this study, in order to better understand the fundamentals of the laser-cluster interaction, we have carried out systematic investigations of the properties of X-ray radiation from high-density and high-temperature cluster plasma created by the action of superintense laser irradiation. The interrelationship between the X-ray radiation properties and ion kinetic energies has been examined for the first time via simultaneous measurements of X-ray radiation spectra and ion energy spectra. The time scale and mechanism of the X-ray emission process are discussed here based on a time-dependent plasma kinetics model. Moreover, in order to demonstrate the practical capabilities of the X-rays thus produced, pulse X-ray diffraction from an Si crystal using this source has been examined. 

According to the relevant power and momentum balance, Eqs. (38) and (39), the electron kinetics in steady-state plasmas is characterized by tbe conditions that at any instant the power and the momentum input from the electric field are dissipated by elastic and inelastic electron collisions into the translational and internal energy of the gas particles. This instantaneous complete compensation of the respective gain from the field and the loss in collisions usually does not occur in time-dependent plasmas, and often the collisional dissipation follows with a more or less large delay—for example, the temporally varying action of a time-dependent field. Thus, the temporal response of the electrons to certain disturbances in the initial value of their velocity distribution or to rapid changes of the electric field becomes more complicated, and the study of kinetic problems related to time-dependent plasmas naturally becomes more complex and sophisticated. Despite this extended interplay between the action of the binary electron collisions and the action of the electric field, the electron kinetics in time-... 

When specifying the kinetic treatment to purely time-dependent plasmas with isotropic scattering in the conservative inelastic collision processes, from system (12) the simplified system (Wilhelm and Winkler, 1979 Winkler and Wuttke, 1992 Loffhagen and Winkler, 1994 Winkler, 1993 Winkler et al, 1995)... 

In contrast to the situation in plasmas in steady state or in time-dependent plasmas, the electron density n z) in space-dependent plasmas always depends on the z coordinate, and this happens already if only conservative inelastic collisions are considered. As an immediate consequence, it no longer makes sense to separate the density from the isotropic and anisotropic distribution of the electrons. 

Time to peak plasma concentration depends on the rate of IV dosing but is usually achieved in 45—90 seconds. Therapeutic plasma concentrations are 1.5—5.0 )J.g/mL, and concentrations above 5 )J.g/mL maybe toxic. The elimination half-life after a bolus iv dose is 8 min the elimination half-life after a 24 h iv infusion is about 100 min. The dmg is eliminated by the kidneys. Ten percent is unchanged and the remainder is in the form of inactive metabolites... 

In the direct insertion technique, the sample (liquid or powder) is inserted into the plasma in a graphite, tantalum, or tungsten probe. If the sample is a liquid, the probe is raised to a location just below the bottom of the plasma, until it is dry. Then the probe is moved upward into the plasma. Emission intensities must be measured with time resolution because the signal is transient and its time dependence is element dependent, due to selective volatilization of the sample. The intensity-time behavior depends on the sample, probe material, and the shape and location of the probe. The main limitations of this technique are a time-dependent background and sample heterogeneity-limited precision. Currently, no commercial instruments using direct sample insertion are available, although both manual and h ly automated systems have been described. ... 

Zero-order kinetics describe the time course of disappearance of drugs from the plasma, which do not follow an exponential pattern, but are initially linear (i.e. the drug is removed at a constant rate that is independent of its concentration in the plasma). This rare time course of elimination is most often caused by saturation of the elimination processes (e.g. a metabolizing enzyme), which occurs even at low drug concentrations. Ethanol or phenytoin are examples of drugs, which are eliminated in a time-dependent manner which follows a zero-order kinetic. 

In the catenary model of Fig. 39.14a we have a reservoir, absorption and plasma compartments and an elimination pool. The time-dependent contents in these compartments are labelled X, X, and X, respectively. Such a model can be transformed in the 5-domain in the form of a diagram in which each node represents a compartment, and where each connecting block contains the transfer function of the passage from one node to another. As shown in Fig. 39.14b, the... 

Prothrombin time PT is performed by adding thromboplastin (tissue) factor and calcium to citrate-anticoagulated plasma, recalcifying the plasma, and measuring the clotting time. The major utility of PT is to measure the activity of the vitamin K-dependent factors II, VII, and X. The PT is used in evaluation of liver disease, to monitor warfarin anticoagulant effect, and to assess vitamin K deficiency. 

The O Flaherty Model simulates the age-dependence of lead kinetics on such factors as absorption efficiency, excretion efficiency, uptake into bone and loss from bone, and partitioning between plasma and red blood cells. The model does not incorporate age, dose rate, or time dependence of lead accumulation in every organ (e g., kidney) because the complex patterns of lead accumulation in certain tissues are not known (O Flaherty 1991a) (see Section 2.4.1). However, the basic model structure allows for additional modules to be incorporated, depending on its intended use in risk assessment. For example, additional modules that are currently being developed are a pregnancy model and a model of net bone loss in older women and men. 

Gulyaev and Polak [Kinetics and Catalysis, 6 (352), 1965] have studied the kinetics of the thermal decomposition of methane with a view toward developing a method for the commercial production of acetylene in a plasma jet. The following differential equations represent the time dependence of the concentrations of the major species of interest. 

To date, three pharmaceutical companies have entered clinical trials with PHD inhibitors for the treatment of anemia with the most advanced being FG-2216. In clinical studies, compound 2 (likely FG-2216) showed a dose- and time-dependent elevation of plasma erythropoietin after oral administration [66]. Healthy volunteers were orally administered various doses of compound 2 and serum erythropoietin (EPO) concentrations were measured at various times. Compound 2 increased serum EPO levels in a dose-dependent manner and, following administration of the 20 mg/kg dose, a 5-fold increase of EPO levels was observed after 12 h. In the same patent application, the effect of 2 on anemic predialysis patients with no previous rh-EPO exposure was also disclosed. Patients were treated with 2 three times/week for 4 weeks (no dose reported) and the hemoglobin levels were assessed on day 42. The patients who received treatment showed a mean increase in hemoglobin of 1.9 g/dL from baseline values, whereas subjects who received placebo showed a mean decrease of 0.35 g/dL from baseline levels. These data suggest for the first time that an oral PHD inhibitor could be effective for the treatment of anemia. 

Fig. 2(a) shows dependencies of KCN content in model solutions on time of plasma treatment. They were prepared by means of dilution of the parent solution, containing 21% KCN and 42% KOH. It was shown that at low concentrations of KCN (0,01 - 0,10 %), complete neutralization of solutions was achieved in 2 -8 min. Under cyanide content of 0,3-U,0 %, this time makes 30 minutes. Solutions with KCN concentration of 1,30 % are not neutralized completely within this time. 

Fig. 2(b) represents similar dependencies for technological solutions. Solutions were obtained by means of cyanidation of specified quantities of one metal (Au, Ag, Cu, Zn, curves l -6 ), or the ore concentrate containing all the above stated metals (curve 7 ). Figures prove that process of cyanide destruction is determined by the time of plasma action on the solution. For technological solutions, time of treatment required for complete destruction of cyanide ions depends on composition of the solution. The more complex is the composition, the longer time is required for complete degradation of cyanides. Character of the curves is changed as well. 

Figure 5. Change in content of KCN (1, 2, 3) and hydrogen peroxide (1 , 2 , 3 ) depending on time of plasma treatment in model solutions with various KCN content ...

Equation where the values of current strength and time of plasma exposure are correlated between each other is the most accurate in describing the dependence. This choice is proved by the least value of exact amount -deviation squares S0CT for the given equation [7],... 

After Cmax and distribution equilibrium have been reached, the subsequent drug elimination phase can generally be described by first-order kinetics. The time-dependent decrease in drug-plasma concentration is paralleled by a corresponding decrease in elimination rate. Under these conditions, the plasma concentration of the drug at time t is given by Eq. (3.1). 

Key points When both curves are drawn, mark a fixed concentration point on the y axis and label it C. Demonstrate that the plasma concentration curve crosses this value twice, at times tx and t2. At time f, the concentration in the plasma is rising and at t2 it is falling. The crucial point now that enables you to define hysteresis is to demonstrate that the effector site concentration is different at these two times depending on whether the plasma concentration is rising (giving concentration Ej) or falling (giving concentration E2). 

Pharmacokinetic concentration-time curves for a drug and ifs mefabolifes are used to identify primary exposure metrics such as AUC, or which are not time-dependent unlike the sequential measurements of concentration over time. A peak plasma concentration of a drug is often associated with a PD response, especially with an adverse event. There can be large inter-individual variability in the time-to-peak concentration, and closely spaced sampling times are often critical to determining the peak plasma concentration accurately in individual patients because of differences in demographics, disease states, and food effects, if any. All these elements are clearly spelled out in the protocols written to conduct these studies. 

Because of the relatively large dispersion from the electrons compared with the almost constant refractivity of the neutrals and the negligible contribution of the ions, it is possible, with simultaneous measurements at two different wavelength, to determine independent values of the density of electrons and of the nonelectronic components in the plasma 274). Alcock and Ramsden 275) used the light from a giant-pulse ruby laser and its second harmonic generated in an ADP-crystal (ammonium dihydrogen phosphate) to probe a pulsed plasma and its time-dependent density in a Mach-Zehnder interferometer. 

Figure 2.4. In vivo measurement of blood-brain barrier (BBB) permeability, (a) Internal carotid artery perfusion technique (i) in the rat. Other branches of the carotid artery are ligated or electrically coagulated (o, occipital artery p, pterygopalatine artery). The external carotid artery (e) is cannulated and the common carotid artery (c) ligated. Perfusion time may range from 15 s to 10 min, depending on the test substance. It is necessary to subtract the intravascular volume, Vo, from (apparent volume of distribution), to obtain true uptake values and this may be achieved by inclusion of a vascular marker in the perfusate, for example labelled albumin. Time-dependent analysis of results in estimates of the unidirectional brain influx constant Ki (pi min which is equivalent within certain constraints to the PS product. BBB permeability surface area product PS can be calculated from the increase in the apparent volume of distribution Vd over time. Capillary depletion, i.e. separation of the vascular elements from the homogenate by density centrifugation, can discriminate capillary uptake from transcytosis. (b) i.v. bolus kinetics. The PS product is calculated from the brain concentration at the sampling time, T, and the area under the plasma concentration-time curve, AUC.

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