Resistance associated with measurements of capacitance in electric double layers

The behavior of electric double layers at polarized interfaces in KC1 solutions is revisited in order to examine properties of the constant phase element (CPE). We pay attention specifically to frequency dependence of both the capacitance and the resistance. Two parallel platinum wires immersed in solution are used as insulator-free electrodes. They avoid stray capacitance or irreproducibility of impedance caused by incompleteness of electric shield of electrodes. The Nyquist plot takes approximately a straight line because the in-phase component, Z1, is inversely proportional to ac-frequency, similar to the capacitance. Since Zi extrapolated to zero separation of the electrodes is non-zero, a resistance is present at the double layer in parallel form. It is not a Faradaic resistance because of absence of any electroactive species. The parallel resistance is inversely proportional to the frequency, whereas the capacitance decreases with a linear relation to logarithm of the frequency. The latter is responsible for the frequency-dependence of the former. The parallel resistance is the apparent one involved inevitably in ac-measurements of the capacitance. Values of the capacitance are independent of concentration of KC1 in the domain from 0.1 mM to 3 M

Electrochemically instantaneous reduction of conducting polyaniline-coated latex particles dispersed in acidic solution

A cathodic voltammetric wave was observed in an aqueous suspension of mono-dispersed, spherical polyaniline-coated polystyrene particles, whereas no anodic wave was detected. This irreversibility was common to particles with eight different diameters ranging from 0.2 to 7.5 μm. Such irreversibility cannot be found at polyaniline-coated electrodes, and thus is a property of the dispersion of polyaniline latex. The reduction current was controlled by diffusion of dispersed particles. The reduction, being the conversion from the electrical conducting state to the resistive one, should begin at a point of contact between the conducting particle and the electrode in order to be propagated to the whole particle rapidly. In contrast, the oxidation proceeds slowly with the propagation of conducting zone, during which Brownian motion lets the particle detach from the electrode. The number of loaded aniline units per particle, determined by weight analysis, ranged from 6×10_6 (φ 0.2 μm) to 3×10_11 (φ 7.5 μm) and was proportional to 2.9 powers of the particle diameter. The diffusion-controlled current of the cathodic wave was proportional to 2.4 powers of the diameter. The difference in these powers, 0.5, agreed with a theoretical estimation of the diffusion-controlled current, the diffusion coefficient for which was given by the Stokes-Einstein equation

Effects of Social Support on New Mothers' Mental Stress Related to Infant Care Stressors

The purpose of this study was to further clarify the quality and function of social support and whether it acts as a buffer against stress or leads to conflicts as observed in the emotional reaction of new mothers during the early period of first infant caring. Seventy women in the early puerperal stage after normal childbirth through normal pregnancy progression at two general hospitals in H. prefecture took part in this study from July through November, 2002 after giving their informed consent. The subjects were interviewed by the authors at least three times during the early period of infant caring. The quality and function of the social support as perceived by the mothers was assessed according to House's four subconcepts : emotional, material, informational, and appraisal support. The mental stress of the mothers was evaluated according to the Japanese State Trait Anxiety Inventory (JSTAI). Two-way layout ANOVA was used for a comparative analysis of these scores related to the mental stresses caused by infant caring. It was found that the perceived material support from the subjects' mothers showed positively direct and buffer effects related to their recognition of stressors on both state and trait anxiety. In terms of appraisal support, however, its direct effect related to their recognition of a stressor was inversely related to the subject's state anxiety. Nurses should recognize the importance of social support for the new mothers because of the effects, both positive and negative, on their mental condition, as well as its potential to lead to conflict

Voltammetry in low concentration of electrolyte supported by ionic latex suspensions

Since ionic conductivity has a linear relation with the square of the number of charge, ionic latex particles with a huge number of the charge could provide high conductance. It is expected that addition of only a small amount of latex particles into voltammetric solution enhances the conductance so much that voltammograms can be measured, overcoming ohmic drop. Conductivity of latex suspensions of polystyrenepolystyrenesulfonic acid with volume fractions less than 0.02, which were well deionized by centrifugation, was determined by ac-impedance at two parallel wire electrodes. Since the resistance was determined by the dependence of the in-phase component on the electrode distance, it did not include participation of electric double layers or adsorption of latex. The relationship between conductivity and a diffusion coefficient stated that the conductivity of the suspension was provided mainly by diffusion of latex particles with multiple charges rather than that of the counterion. The suspension with [H^+] = 10^-5 M, corresponding to 8.9 x 10^5 number mm^-3, including hydrogen gas showed a voltammetric oxidation peak of hydrogen, whereas hydrochloric acid with [HCl] = 10^-5M showed a resistive current-potential curve

Determination of concentration of saturated ferrocene in aqueous solution

The solubility of ferrocene in aqueous solution is known to be approximately 0.04 mmol/dm3. The solubility values determined by voltammetry have been overestimated because of adsorption on electrodes. This work deals with discerning diffusion from adsorption by altering not only the voltammetric time scale but also the solvents used. Fast voltammetric responses by differential pulse voltammetry and fast scan voltammetry exhibited adsorption behavior. In contrast, quasi steady-state voltammetry showed the diffusion-control, the current of which seemed to evaluate the saturated concentration accurately. However, the currents in the solution including a small amount of organic solvent were smaller than those in the aqueous solution although the concentrations were identical. Solutions including organic solvents have often been used to obtain calibration curves. Therefore, the concentration evaluated from the calibration curve was estimated to be larger than the true concentration. The current in the organic solvent was explained in terms of the extra solvation energy by supersaturation, which was dissipated to low concentrated domains by diffusion. It was formulated in the form of diffusion coefficients. The true concentration was evaluated to be 0.01 mmol/dm3 by slow scan voltammetry in the solution without calibration curves

Distance-dependent switching of anti-predator behavior of frogs from immobility to fleeing

To avoid predation, many animals are required to appropriately switch between immobility for crypsis and fleeing for escape. We conducted two staged-encounter experiments using a frog and a snake to examine factors that affect the occurrence of immobility and fleeing, and to evaluate the efficiency of them. The first experiment demonstrated that frogs initially exhibit immobility, when snakes are moving at a long distance, and then switch from immobility to fleeing at a shorter distance even when snakes have not detected them. The second experiment demonstrated that snakes at 400–800 mm distance detect only fleeing frogs, whereas snakes at 100 mm or closer detect both immobile and fleeing frogs. Thus, the ability of snakes to detect motionless frogs depends on the distance, and the distance-dependent switching can be considered an adaptive strategy of the frog. However, a previous model predicts that cryptic prey should flee immediately on seeing a predator or not flee until being detected by the predator. To explain this discordance, we propose two factors: engagement of intensive searching mode by predator at short distance and effects of sudden fleeing at close distance. We suggest incorporating them in future theory for better understanding of anti-predator strategy

Early Duplication of a Single MHC IIB Locus Prior to the Passerine Radiations.

A key characteristic of MHC genes is the persistence of allelic lineages over macroevolutionary periods, often through multiple speciation events. This phenomenon, known as trans-species polymorphism (TSP), is well documented in several major taxonomic groups, but has less frequently been observed in birds. The order Passeriformes is arguably the most successful terrestrial vertebrate order in terms of diversity of species and ecological range, but the reasons for this success remain unclear. Passerines exhibit the most highly duplicated MHC genes of any major vertebrate taxonomic group, which may generate increased immune response relative to other avian orders with fewer MHC loci. Here, we describe phylogenetic patterns of the MHC IIB in the passerine family Corvidae. Our results indicate wide-spread TSP within this family, with at least four supported MHC IIB allelic lineages that predate speciation by many millions of years. Markov chain Monte Carlo simulations indicate that divergence of these lineages occurred near the time of the divergence of the Passeriformes and other avian orders. We suggest that the current MHC diversity observed in passerines is due in part to the multiple duplication of a single MHC locus, DAB1, early in passerine evolution and that subsequent duplications of these paralogues have contributed to the enormous success of this order by increasing their ability to recognize and mount immune responses to novel pathogens

Old divergences in a boreal bird supports long-term survival through the Ice Ages

<p>Abstract</p> <p>Background</p> <p>Unlike northern Europe and most of northern North America, the Eastern Palearctic and the northwesternmost tip of North America are believed to have been almost unglaciated during the Quarternary glacial periods. This could have facilitated long-term survival of many organisms in that area. To evaluate this, we studied the phylogeography in east Asia and Alaska of a boreal migratory passerine bird, the Arctic Warbler <it>Phylloscopus borealis</it>, and compared our results with published data on especially North American species.</p> <p>Results</p> <p>In a sample of 113 individuals from 18 populations we identified 42 haplotypes of the mitochondrial cytochrome <it>b </it>gene, which separated into three clades: A - Alaska and mainland Eurasia (except Kamchatka); B - Kamchatka, Sakhalin and Hokkaido; and C - Honshu, Shikoku and Kyushu (i.e. Japan except Hokkaido). The oldest split among these clades, between A/B and C, is estimated to have taken place sometime between the mid Pliocene and early Pleistocene, and the second divergence, between clades A and B, in the early to mid Pleistocene. Within all of the three main clades, there are signs of population expansion.</p> <p>Conclusions</p> <p>The Arctic Warbler separated into three main clades in close succession around the Pliocene/Pleistocene border, with the two northern clades diverging last. All three clades probably experienced population bottlenecks during the Pleistocene as a result of range shifts and contractions, but nevertheless survived and maintained their integrities. Several other clades of Northeastern Palearctic birds are noted to have diversified during the Pliocene. In contrast, avian species or phylogroups presently occupying formerly glaciated North American ground are generally younger. The differences between these regions could be due to slower speciation rates in the Eastern Palearctic due to less fragmentation of forest habitats during glacial periods, or to longer survival of Eastern Palearctic clades as a result of less severe conditions in that region compared to northern North America. Several other Palearctic organisms show concordant biogeographical patterns to that of the Arctic Warbler, indicating common causes of their diversifications.</p

A miniaturized threshold-triggered acceleration data-logger for recording burst movements of aquatic animals

Although animal-borne accelerometers are effective tools for quantifying the kinematics of animal behaviors, quantifying burst movements of small and agile aquatic animals remains challenging. To capture the details of burst movements, accelerometers need to sample at a very high frequency, which will inevitably shorten the recording duration or increase the device size. To overcome this problem, we developed a high-frequency acceleration data-logger that can be triggered by a manually-defined acceleration threshold, thus allowing the selective measurement of burst movements. We conducted experiments under laboratory and field conditions to examine the performance of the logger. The laboratory experiment using red seabream (Pagrus major) showed that the new logger could measure the kinematics of their escape behaviors. The field experiment using free-swimming yellowtail kingfish (Seriola lalandi) showed that the loggers trigger correctly. We suggest that this new logger can be applied to measure the burst movements of various small and agile animals.</jats:p