Currents lower than expected

A few studies (Kukkonen et al., 1989 Kukkonen and Oikari, 1991 Muir et al., 1994) have reported an enhancement of organic contaminant bioavailability to various organisms. In all cases this occurred at low DOM concentrations (< 10 mg/L carbon). Currently, a specific mechanism has not been determined, but Muir and co-workers (1994) have suggested that organic mucus in fish can act in a manner similar to that of DOM and bind contaminants. They observed lower than expected bioaccumulation of pyretheroids in control studies followed by an enhancement with the addition of small amounts of DOM. Nonetheless, this does not explain the enhanced bioaccumulation observed for other aquatic organisms. 

Special attention should be paid to the amplitude of the experimental curves, which roughly equals that predicted theoretically. In inelastic spectroscopy the amplitude of the EPI spectrum is an order of magnitude lower than expected one (see Fig. (1) in Ref. [14] and the discussion cited therein). This discrepancy may be explained either by the diffusive regime of current flow with and unknown mean free path (j, or by the specific PC-transport character of the EPI function obtained from the inelastic backscattering spectrum. 

The different electrode connections are top to bottom (T-B), top to mesh (T-M) and top to mesh + bottom (T-MB). The average ion current values at —400 volts and 2 torr are 2.8, 5.8 and 7.5 /xamp respectively for the different electrode connections. The mesh electrode collects a large fraction of the total current. Ideally the T-B current plus the T-M current should equal the T-MB current. The results show that the T-MB current is a little lower than expected. This is probably because of an artificially high T-M current caused by some transmitted ions being attracted back to the mesh electrode. Thus, in the T-B or T-MB connections 2.8/7.5 = 38% of the ions are transmitted through the mesh electrode. 

The electrochemical eflBdency gives more information about fuel cells than the thermodynamic efHciency as it is directly related to the performance of the cell. For a complete description of the fuel cell efHciency further factors associated with practical operation have to be considered. These include the faradaic efHciency ep which is deHned as the ratio of the actual current fact and the maximum possible current Imax- This faradaic efficiency considers the possibility of parallel reactions which can lead to a lower current yield than expected theoretically. Furthermore, the total efficiency of the cell requires the consideration of practical aspects concerned with the specific fuel used. In most cases fuel cells are not operated with 100 % fuel utilization in order to avoid fuel depletion in some areas of the electrodes. Therefore the fuel utilization should be included in the total efficiency, given as... 

A battery s capacity is the amoimt of electric charge which the battery can store. If there is more electrolyte and electrode material in the cell, capacity of the eell will be greater. A small cell has less capacity than a laiger cell with the same ehemistry. Because of the chemical reactions within the cells, the capacity of a battery depends on the discharge conditions such as the magnitude of the current. If a battery is discharged at a relatively high rate, the available capacity will be lower than expected. 

The two field exercises were conducted at DPG to provide information on the detection limits of our on-site analysis approach. Three types of samples were analyzed soil, water, and swipes. Each sample had been spiked by the "host facility" with CW-related target compounds at either 10 ppm or 100 ppb. The suite of spiked samples also included a blank, bringing the total to nine working samples. The new SPE procedures in conjunction with current analytical field instrumentation provided a detection limit of approximately 1 ppm, which was lower than expected. 

The presence of two cathodic peaks and one anodic peak confirms the statement that this process is not a simple diffusion-controlled one electron exchange from Fe(III) to Fe(II), as well as not pure diffusion controlled process (activation control is also involved [136]). By plotting current density of oxidation peaks (/p(ox)) versus well-defined linear dependence is also obtained (Fig. 5.26b), indicating diffusion-controlled oxidation [136], but the value of the diffusion coefficient calculated from the slope of this dependence (assuming that the concentration of reduced species is 0.1 M) was one order of magnitude lower than expected. Hence, it could be concluded that Fe(III) species reduce in the potential range between —0.2 V and —1.0 V and that under the convective diffusion reduced... 

Calibration plots of peak current versus standard DA concentration are prepared for each electrode used to evaluate the concentration of measured exocy-totic events, and an estimate of the concentration during exocytosis can be obtained by comparison of the peak current for voltammograms obtained for individual exocytosis events to the calibration plot [13]. However these concentration estimates are lower than expected for vesicular concentrations. This is because in measuring exocytotic events, the released catecholamine only accesses a very... 

LESS Brightness level of LEDs lower than expected LED current too low Brightness level not as intended... 

In sodium chloride solutions the ion transport number for Na+ is about 0.4 compared to about 0.6 for CU. Thus a CX membrane would be expected to polarize at lower current densities than an AX membrane. Careful measurements show that CX membranes do polarize at lower current densities however, the effects on pH are not as significant as those found when AX membranes polarize. Such differences ia behavior have beea satisfactorily explaiaed as resultiag from catalysis of water dissociatioa by weaMy basic groups ia the AX membrane surfaces and/or by weaMy acidic organic compounds absorbed on such surfaces (5). 

Many fluids of natural origin contain detectable quantities of high molecular weight organic anions, such as those from humic, fulvic, and tannic acids, which can be carried to and deposited on AX membranes. Such deposits can behave as thin films partially selective to cations (6). The iaterfaces between such films and the undedyiag AX membranes then act as very thin stagnant depletion compartments and the AX membranes may exhibit polarization at current densities that are much lower than would be expected for new membranes ia the abseace of such anioas. 

An important eonelusion was that the best catalyst is not the alloyed one as expected, nor the mixture of Pt/XC 72 and Ru/XC 72 powders, but one eonsisting of a dispersion of Pt colloid and Ru colloid on the same carbon support, i.e., the Pt + Ru/XC 72 eatalyst. The latter leads to higher current densities for the eleetro-oxidation of methanol than the other catalysts with the same atomic ratio for potentials lower than 0.5 V versus a reversible hydrogen electrode (RHE) (Fig. 11.3). This result... 

Unlike solid electrodes, the shape of the ITIES can be varied by application of an external pressure to the pipette. The shape of the meniscus formed at the pipette tip was studied in situ by video microscopy under controlled pressure [19]. When a negative pressure was applied, the ITIES shape was concave. As expected from the theory [25a], the diffusion current to a recessed ITIES was lower than in absence of negative external pressure. When a positive pressure was applied to the pipette, the solution meniscus became convex, and the diffusion current increased. The diffusion-limiting current increased with increasing height of the spherical segment (up to the complete sphere), as the theory predicts [25b]. Importantly, with no external pressure applied to the pipette, the micro-ITIES was found to be essentially flat. This observation was corroborated by numerous experiments performed with different concentrations of dissolved species and different pipette radii [19]. The measured diffusion current to such an interface agrees quantitatively with Eq. (6) if the outer pipette wall is silanized (see next section). The effective radius of a pipette can be calculated from Eq. (6) and compared to the value found microscopically [19]. 

In general, most converters are tested on the bench with the electronic load set to constant current (CC mode). True, that s not benign, nor as malignant as it gets. But the implied expectation is that converters should at least work in CC mode. They should, in particular, have no startup issues with this type of load profile. But even that may not be the end of the story Some loads can also vary with time. For example, an incandescent bulb has a resistive profile, but its cold resistance is much lower than its hot resistance. That s why most bulbs fail towards the end of their natural lifetime just when you throw the wall switch to its ON position. And if the converter is powering a system board characterized by sudden variations in its instantaneous supply current demand, that can cause severe problems to the converter, too. The best known example of this is an AC-DC power supply inside a computer. The 12V rail goes to the hard disk, which can suddenly demand very high currents as it spins up, and then lapse back equally suddenly into a lower current mode. 

Although it may be intended that current should be shared between 106 emitters, in practice there is huge current crowding so that emission occurs from only a few of them, perhaps 1 or 10 in 105. This has two severe consequences. First, the emission site density is much lower than might be expected from the nanotube density. Second, the operating emitters can easily exceed their maximum currents and burn out, passing the emission onto those with the next highest p value, and so on. This leads to unstable emission behavior [27]. 

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