Distortion analysis of magnetic excitation – a novel method for non-destructive evaluation of depth of surface-hardening in ferritic steels

The influence of ferritic steel samples with different case-depths on the distortion behaviour of magnetic excitation voltage has been investigated. The systematic changes in the height and position of the peak and the trough on the ((dV_E/dt) vs. V_T) profile (distortion analysis of the magnetic excitation, DAME profile) reflect the difference in the magnetization process and hence the effect of distortion of V_E in samples with different case-depths. This study shows the potential of this simple DAME method for evaluation of ferromagnetic steel components.     

Near-infrared transitions of LiNdP4O12 and LiErYP4O12

Abstract

Fluorescence transitions in LiNdP₄O₁₂: ⁴ F_3/2→⁴I_9/2 (0·90μm), ⁴F_3/2→⁴I_11/2 (1·05μm), ⁴F_3/2→⁴I_13/2 (1·32μm), ⁴F_3/2→⁴I_15/2 (1·77μm), and in LiErYP₄O₁₂: ⁴S_3/2→⁴I_11/2 (1·3μm), ⁴I_13/2→⁴I_15/2 (1·53μm), have been obtained at room temperature. The positions of the energy levels related to the excitation, nonradiative and radiative processes have been established from complementary absorption measurements. The fluorescence lifetimes of the above-mentioned transitions have been determined from single exponential decays.     

Highly fluorescent silver nanofluids with ferroelectric molecules

Highly fluorescent silver nanoparticles (Ag-NPs), soluble in a ferroelectric host of polymer molecules such as poly(vinylidene fluoride) (PVF₂), have been created in the form of nanofluids. The content of Ag-NPs (flocculates) is varied in steps 0.1–0.2 wt% up to a value of 5.0 wt% in tailoring a broad green emission band over 520–620 nm out of a hybrid percolation Ag–PVF₂ composite. A maximum intensity arises in this band at as small a percolation threshold as ～0.1 wt% Ag-NPs. It contains three distinct bands of peak values 541, 565, and 582 nm in an Ag-NPs tunable response of the localized surface plasmons. The emission-dependent anti-Stokes excitation spectrum contains a similar group of three bands 348, 401, and 421 nm. For Ag-contents above 0.1 wt%, interdependent intensities in the emission and excitation bands drop rapidly by as much as five times, conferring a metal–polymer percolation network. The results open wide applications for biological labels and light emitters using such nanofluids.     

Phase stability of Al3Nb as a function of nickel additions

Abstract

Phase stability of the intermetallic compound Al₃Nb is investigated as a function of nickel additions by band structure calculations based on an extended Hueckel tight-binding method. With this method, the electronic structure and total energies of the Al_6-n -Ni _n Nb₂ compounds (where n is an integer from 0 to 6) are calculated for both D0₂₂ and L1₂ structures under the assumption that nickel substitutes for aluminium. The electronic total energies obtained from integration of the energy states of all electrons considered have shown that the D0₂₂ structure is stable in the binary Al₃Nb compound as compared with the L1₂ structure; conversely, the L1₂ structure is stable for compounds with n values greater than 1. These calculations are in good agreement with X-ray diffraction results reported by Schubert and co-workers. Differences in the electronic total energy per atom between D0₂₂ and L1₂ are - 0·79 eV and 0·56 eV for n equal to 0 and 2, respectively.     

The general psychophysical differential equation: A comparison of three specifications

The general psychophysical differential equation, dy/dx = W₂(y)/W₁(x), with the solution y = f(x), where x and y are subjective variables and W₁ and W₂ their subjective Weber functions, is (a) compared with a corresponding functional equation, and (b) studied from a stochastic point of view by error calculus, Methods for evaluating and handling divergences are proposed and illustrated for a number of combinations of Weber functions. It is shown that either the differential: and the functional equations have the same solution or the difference between the solutions is negligible compared to empirical scatter. The error calculus gives the same result: either no error at all or a negligible one.     

Solidification thermal parameters,microstructural evolution and dendritic growth in an AlCuNi alloy

ABSTRACT

Unsteady-state upward solidification experiment was carried out with the Al-3Cu-3Ni (wt.%) alloy. Temperature profiles were obtained through a water-cooled directional solidification device. Analysis on the resulting as-cast microstructure and its adaptation to thermal solidification parameter, such as growth and cooling rates and solidification local time, V_L, T_R and t_SL, respectively, was carried out. The results showed that the resulting microstructure is constituted by an Al-rich primary phase (Al _α ), characterised by a dendritic network, and by second phases that take place within the interdendritic regions, forming a eutectic mixture composed by the β-Al₃Ni?+?θ-Al₂Cu intermetallic compounds (IMCs), whose size and morphology have been affected by V_L and T_R. The length of the microstructural scale of the Al _α phase was measured by the secondary dendritic spacing (λ ₂). The experimental mathematical expression of λ ₂ obtained in this work was compared with mathematical models proposed in the literature that associate t_SL-λ ₂ for non-equilibrium and equilibrium solidification conditions.     

Effects of 7.5% CO2-Induced Anxiety on Individual Performance During a Group Computer Combat Game

The inhalation of 7.5% CO₂ has been shown to induce cognitive effects similar to anxiety. Sixteen healthy participants (14 male; mean age 25.6 years) inhaled either a mixture of 7.5% CO₂ gas or air while playing a group combat computer game. Participants reported greater feelings of anxiety and fired fewer bullets when inhaling CO₂ compared with air, indicating CO₂-induced anxiety may improve efficiency without task-related decrements. Being able to induce controlled and measured anxiety in group situations by CO₂ inhalation may be a useful technique when evaluating response to stressful situations, such as combat, in simulators or real-life scenarios.     

Successive discrimination training with equated reinforcement frequencies: failure to obtain behavioral contrast

In two experiments, pigeons were trained on two-component multiple schedules in which responding in one component (S₁) was always maintained by a variable-interval schedule. In Experiment I, low response rates were reinforced in the second (S₂) component for six master subjects. This schedule was adjusted to equate reinforcement frequencies in the two components. These subjects were compared to yoked partners, for which reinforcement in the S₂ component was made available on a variable-interval schedule whose value was determined by the master subjects. A similar procedure was used in Experiment II, where the S₂ schedule for master subjects made reinforcers contingent on the absence of responding. No evidence was found in either experiment for a behavioral contrast effect in the S₁ component attributable to response reduction in the S₂ component. A reliable contrast effect was obtained from a group of pigeons given extinction conditions in the S₂ component, which was compared to a group maintained throughout on a multiple variable-interval schedule. The results suggest that previous indications of behavioral contrast in similar situations were probably caused by uneven reinforcement distributions or reflect uncontrolled fluctuations in response rates.     

Identification of argentine Spanish vowels

The acoustical spectrum of the five Spanish vowels |a, e, i, o, u| has been delimited to show the areas covered by F ₁ , F ₂ , and F ₃ and the relative distribution energy among the formants. Through the analysis of the spectral components of vowels, isolated and in consonantal context, it is possible to estimate the different weight of each formant in vowel identification. At least for isolated vowels,F ₂ andF ₃ seem to be effective for the identification of [i] and [e] while theF ₁ andF ₂ carry the weight for the identification of [o] and [u]. The cue to differentiate [a] seems to beF ₂. Spanish vowels are compared with cardinals and North American English vowels. There is no correlation with cardinal vowels while similarities are found with English vowels.     

The missing fundamental in vowel height perception

Traunmüller (1981) suggested that the tonotopic distance between the first formant (F ₁) and the fundamental frequency (F ₀) is a major determinant of perceived vowel height. In the present study, subjects identified a vowel-height continuum ranging in formant pattern from /?/ to /ε/, at fiveF ₀ values. IncreasingF ₀ led to an increased probability of /I/ responses (i.e., the phoneme boundary shifted toward the /ε/ end of the continuum). Various conditions of filtering out the lower harmonics of the stimuli caused only marginal shifts of the phoneme boundary. The experiments provide evidence against interpretations of Traunmüller’s (1981) results that claim that vowel height is determined by the distance betweenF ₁ and the lowest harmonic that is present in the basilar membrane excitation pattern.     

The cognitive implications of asymmetric color generalization in honeybees

Generalization occurs when a conditioned response formed to one stimulus is also elicited by other stimuli which have not been used in the course of conditioning. Here, we studied color generalization in honeybees Apis mellifera trained to two rewarded colors, S₁+ and S₂+. After training, bees were tested with non-rewarded novel stimuli, which lay between the trained stimuli in a honeybee color space (Int) or outside the range defined by the trained stimuli (E ₁ and E ₂). We analyzed whether bees interpolated their choice to Int and/or extrapolated it to E ₁ and E ₂. We compared the performances of the group trained with S₁+ and S₂+ to those of control groups trained only with S₁+ or S₂+. Bees trained with S₁+ and S₂+ responded similarly and highly to all test stimuli. These results do not allow discerning between generalization models based on the presence of interpolation and/or extrapolation. Nevertheless, bee’s performance was consistent with a linear summation of the two generalization gradients generated by S₁+ and S₂+, respectively. These gradients were asymmetric because control bees responded to the test stimuli as if these belonged to different similarity classes in spite of the fact that they had similar perceptual distances separating them. Stimuli treated as similar were located in the same half of the color spaces, whereas stimuli treated as different were located in opposite halves. Our results suggest that color categories could exist in honeybees and may underlie the performance of the control groups. Under this assumption, color categories would be also present in simpler nervous systems, and would not require factors such as language to be expressed.     

Intensity discrilnination: Performance in three paradigms

Performance in the following auditory intensity-discrimination paradigms was compared: (1) 2IFC, (2) single-interval rating with an intensity cue preceding each observation interval, and (3) single-interval rating with no cue. ROCs obtained in the single-interval conditions could be well approximated by assuming that the underlying distributions were both normal and had equal variance. No large difference was observed between performance in the cue and the no-cue conditions. The normalized separation of the means for 2IFC was approximately twice the corresponding estimate for the single-interval conditions. i.e., d₂ = 1.91 d₁. This is consistent with the hypothesis that the O in intensity-discrimination tasks bases his decisions on the difference between the observed input and that of a noisy stored reference. The familiar result that d₂ = (2)^1/2 d₁ can be predicted for simple detection.     

Slow cortical and heart rate correlates of discrimination performance

Slow EEG potentials (F_z, C_z, P_z) and heart rate were recorded during the foreperiod of a reaction task, which involved different levels of discrimination difficulty. A simple reaction task was compared with a selective reaction task where either an easy or a difficult discrimination was required. In general, the terminal amplitude of the CNV was not affected by task difficulty. However, a prolonged negative wave was found when the difficulty of the task was not known to the subject in advance but was indicated by S₁. Moreover, the heart-rate deceleration around S₂ was more pronounced the more difficult the discrimination required at S₂.     

Experimental comparison of dyspnea and pain

Dyspnea and pain are similarly unpleasant, alarming physical sensations, but studies examining both sensations in combination are lacking. In the present study, dyspnea was induced in 7 healthy volunteers by breathing through inspiratory resistive loads and the effects were compared with those of a heat pain stimulus. End-tidal partial pressures of carbon dioxide (PET_CO2), inspiratory time (Ti), breathing frequency (f), experienced unpleasantness, and intensity were measured. No difference was observed between dyspnea and pain in experienced intensity and unpleasantness (p >.05). During dyspneic stimulation, slightly higherTi was found than for pain (p<.08). PET_CO2 showed slight increases during the dyspneic versus the baseline and painful conditions (ΔPET_CO2=1.5 and 1.3 mmHg, respectively;p<.01 andp<.05). This study shows that the effects of dyspnea and heat pain can be compared within one experiment; both stimuli can be presented with similar intensity and unpleasantness, which is a prerequisite for comparing responses to them. The changes in PET_CO2 between our conditions were minimal, allowing an application of the present design to future fMRI studies.     

Growth of carbon nanotubes: effect of Fe diffusion and oxidation

The diffusion and surface oxidation rates of Fe deposited on Si and barrier layers of Al/SiO₂ and Al₂O₃/SiO₂ have been comparatively studied and correlated with the growth of carbon nanotubes (CNTs). Initially, Fe/Si, Fe/Al/SiO₂/Si and Fe/Al₂O₃/SiO₂/Si samples were subjected to thermal chemical vapour deposition (CVD) at ～650°C for ～30?min to grow the CNTs. Scanning electron microscopy analysis showed that the height of the CNTs on the Fe/Al₂O₃/SiO₂/Si samples was relatively high (～9.5–11?µm), as compared with the other samples. To investigate this, a few as-prepared samples were thermally annealed at ～650°C for ～30?min and characterized by dynamic secondary ion mass spectroscopy (D-SIMS) and X-ray photoelectron spectroscopy (XPS). The D-SIMS results showed that the diffusion depth, x _Fe, and magnitude of the diffusivity, D _Fe, of the Fe atoms are highest for the Fe/Si sample. This is attributed to vacancy-mediated migration, which leads to the formation of unstable, non-stoichiometric Fe–Si and Fe–O–Si phases. However, for the Fe/Al₂O₃/SiO₂/Si samples, the magnitudes of x _Fe and D _Fe are found to be the lowest, which indicates steric hindrance to Fe by the Al₂O₃ layers. The XPS analysis revealed that the surface metallic state, after annealing, is almost unaffected for the Fe/Al₂O₃/SiO₂/Si samples, whereas the majority of the Fe precipitate was observed to be oxidized in the case of the other samples.     

Detection of change in nonstationary binary sequences

The present study was designed to investigate the ability of humans to detect changes in the underlying probability structure of binary sequences of events. Four Ss were presented with sequences of 30 events (zeros and ones) which had been generated by two underlying probability values. P₁ was the probability of a one in the first i events, P₂ was the probability of a one in the last 30-i events, and the distribution of i was uniform from 1 to 29. The Ss indicated, without feedback, where the transition point from P₁ to P₂ took place for four sets of problems in which P₁ and P₂ took on the following pairs of values: (.40, .60), (.20, .80), (.05, .60), and (.50, 1.00). Estimates by Ss were compared with true transition points, i, and with maximum likelihood estimates of i. The difference between P₁ and P₂ and the closeness of at least one P value to the boundaries, either zero or unity, interacted in determining the difficulty of the problem for Ss.     

Progesterone to ovariectomized mice enhances cognitive performance in the spontaneous alternation, object recognition, but not placement, water maze, and contextual and cued conditioned fear tasks

Research on how steroid hormones mediate mnemonic processes have focused on effects of 17β-estradiol (E₂); yet, progesterone (P₄) co-varies with E₂ across endogenous hormonal milieu, and itself may influence cognitive processes. We investigated the hypothesis that acute P₄ treatment enhances cognitive performance compared to vehicle. Ovariectomized (OVX) c57/BL6J mice were randomly assigned to be subcutaneously injected with oil vehicle or P₄ (10 mg/kg). Mice were trained in the spontaneous alternation, object recognition, object placement, water maze, or fear conditioning tasks, and injected with vehicle or P₄ before training or immediately post-training, and then were tested 1, 4, or 24 h later. The data obtained from these experiments supported our hypothesis. P₄ increased the percentage of spontaneous alterations made in a T-maze more so than did vehicle. P₄, compared to vehicle, increased the percentage of time spent exploring the novel object in the object recognition task, but did not alter performance in the object placement task. P₄, compared to vehicle, decreased latencies to reach the location in the water maze where the platform had been during training in a probe trial, but did not alter performance in the control, cued trial. Compared to vehicle, P₄ treatment increased freezing in contextual and cued fear testing. Thus, acute P₄ treatment to OVX mice can improve cognitive performance across a variety of tasks.     

Short-range order in the arrangement of grains in two-dimensional polycrystals

Abstract

Experimental results for two-dimensional grain growth are compared with the results obtained from computer-generated random threefold vertex networks with a fixed one-particle distribution function. A considerable discrepancy in the two-particle distributions implies some kind of short-range order. New results in the computer simulation of normal grain growth are reported, demonstrating a similar kind of ordering. A simple relation is suggested for the quantity m _n, introduced by Aboav and the second moment of the one-particle distribution μ₂     

Acutely induced anxiety increases negative interpretations of events in a closed-circuit television monitoring task

In two experiments we measured the effects of 7.5% CO₂ inhalation on the interpretation of video footage recorded on closed circuit television (CCTV). As predicted, inhalation of 7.5% CO₂ was associated with increases in physiological and subjective correlates of anxiety compared with inhalation of medical air (placebo). Importantly, when in the 7.5% CO₂ condition, participants reported the increased presence of suspicious activity compared with placebo (Experiment 1), a finding that was replicated and extended (Experiment 2) with no concomitant increase in the reporting of the presence of positive activity. These findings support previous work on interpretative bias in anxiety but are novel in terms of how the anxiety was elicited, the nature of the interpretative bias, and the ecological validity of the task.     

Excitation of a chain of neurones

When the first of a uniform chain of neurones is excited with a stimulus intensityS ₁, it is found that, according to the nature of the chain,either the excitation is always transmitted with decreasing intensity,or else the intensity for succeeding neurones of the chain approaches a fixed finite value, characteristic of the chain and independent ofS ₁, wheneverS ₁ exceeds a certain threshold value.