Stability of nanocrystalline disordered NiAl synthesized by mechanical alloying

The thermal stability of highly disordered mechanically alloyed nanocrystalline NiAl has been evaluated. The reordering of disordered NiAl(Cr) shows extremely fast kinetics on isothermal annealing at and above 673K, while the process is quite sluggish below this temperature. On the other hand, significant reordering in NiAl(Fe) takes place even at 573K. A unique dependence of reordering on the grain growth of the nanophase is evident during thermal treatment. Rapid grain coarsening begins only as the absolute temperature approaches approximately 0.4 T m, where T m is the melting point of the aluminide.     

Extended energy-loss fine structure analysis of 3d transition metals using L ionization edges

The extended energy-loss fine structure (EXELFS) in electron-energy-loss spectroscopy has been compared experimentally with the extended X-ray absorption fine structure (EXAFS), for determining local structure around 3d transition metals. Since the EXELFS spectrum is acquired in an analytical transmission electron microscope, the probing beam can be focused to offer a lateral spatial resolution in the nanometre range, which is several orders of magnitude better than that of X-rays. Also, the microscope allows the area of interest to be imaged and analysed by other methods. However, difficulties in the analysis of EXELFS of 3d transition metals arise from the overlap of the edges in the accessible L series. EXELFS of L ionization edges of crystalline Ni and Cu were examined as test specimens. The overlapped L₁,L₂ and L₃ edges were separated and compared with the K-edge EXAFS of the same samples. The first- and second-nearest-neighbour distances from EXELFS are in agreement with those measured from EXAFS and X-ray diffraction. As a structural probe, however, the accuracy of quantitative analysis of EXAFS is still superior since the L-edge EXELFS decays more rapidly than K-edge EXAFS.     

Electrical conductivity of Nd and Ce co-doped Gd2Zr2O7 ceramics

In this study, (Gd_{1? x} Nd _x )₂(Zr_{1? x} Ce _x )₂O₇ (0 ≤ x ≤ 0.5) ceramics have been prepared by pressureless sintering at 1973 K to investigate the influence of Nd and Ce co-doping on their electrical conductivity. The electrical conductivity of the ceramics was investigated by impedance spectroscopy measurements from 723 to 1173 K over the frequency range of 20 Hz to 2 MHz in air. The measured values obey the Arrhenius relation. For each composition, the grain conductivity gradually increases with increasing temperature from 723 to 1173 K. At a given temperature, it gradually decreases with increasing neodymium and cerium contents from x = 0 to 0.3; thereafter, the grain conductivity exhibits a slight increase with further increasing neodymium and cerium contents up to x = 0.5.     

Atomic geometry and energetics of carbon nanotube necking

Molecular mechanics simulations were performed to probe the incipient plastic deformation in carbon nanotubes (CNTs), which involves nucleation of Stone–Wales (SW) defects and spiral glide of 5/7 dislocation dipoles that lead to quantized necking through a stepwise reduction in tube diameter. Quantification of the strain-dependent energetics of dislocation glide reveals that such dislocation motions are energetically favoured at high tensile strain. Pre-existing dislocations critically affect subsequent nucleation and separation of SW defects, as manifested by the competing deformation modes of symmetric versus asymmetric necking. The results provide a quantitative basis for the dislocation dynamics simulations of superplastically deformed CNTs.     

Absorption and photoluminescence spectroscopy of Er3+-doped SrAl2O4 ceramic phosphors

A spectroscopic characterization of Er³⁺-doped SrAl₂O₄ phosphor materials synthesized by a solid-state reaction method with Er concentrations varying from 0.1 to 1?mol% has been performed by studying photoluminescence (PL) in the temperature range 10 to 360?K and absorption spectra. PL signals containing five emission bands at 1492, 1529, 1541, 1558, and 1600?nm, respectively, have been observed at room temperature for Er³⁺ transitions in the near infrared region. The samples exhibit a main luminescence peak at 1.54?µm, which is assigned to recombination via an intra-4f Er³⁺ transition. Sharp bands centered at around 378, 488, 521, 651, 980, 1492, and 1538?nm in the absorption spectra can be associated with transitions from ⁴I_15/2 level to ²H_9/2, ⁴F_7/2, ²H_11/2, ⁴F_9/2, ⁴I_11/2, ²H_11/2, and ⁴I_13/2 levels, respectively. The sharp emission peaks and excellent luminescence properties show that SrAl₂O₄ is a suitable host for rare-earth-doped phosphors, which may be suitable for optical applications.     

Investigations of the optical spectra and EPR g-factors for the tetragonal Ce3+ centers in YPO4 and LuPO4 crystals

The optical spectral band positions and EPR g-factors (g_‖ , g _⊥) for the tetragonal Ce³⁺ centers in YPO₄ and LuPO₄ crystals with the zircon-structure are calculated using a complete diagonalization (of the energy matrix) method (CDM) related to 4f¹ ions in tetragonal symmetry. In this method, the Zeeman interaction term are added to the Hamiltonian in the conventional CDM and so no perturbation calculations are required to obtain the g factors. The crystal-field parameters used in the calculations are obtained from the superposition model in which the local lattice relaxation related to the bonding lengths is considered. The calculated results are in reasonable agreement with the experimental values. It is found that the four observed optical bands for both the systems can be attributed to Ce³⁺ ions in a tetragonal crystal field.     

Phonon densities of states of gamma-cerium and delta-cerium measured by time-of-flight inelastic neutron scattering

Time-of-flight inelastic neutron scattering spectra were measured on cerium metal at temperatures near the fcc (gamma)-to-bcc (delta) transition temperature. Phonon density-of-states (DOS) curves were extracted from data acquired over a wide range of momentum transfers. A large softening of the phonon DOS was found in going from gamma-cerium to delta-cerium, and this accounts for an increase in vibrational entropy of (0.71 +/- 0.05)k _B/atom. To be consistent with the latent heat of the gamma-delta transition, this increase in vibrational entropy must be accompanied by a large decrease in electronic entropy. The results not only confirm the recent discovery of a significant electronic contribution to the gamma-delta transition but also suggest that it may be twice that previously reported.     

The effect of hydrogen plasma on the properties of a-Si:H/a-Si1-xNx:H superlattices

Abstract

A hydrogen plasma introduced during the interrupting interval when alternating two gases affects the properties of a-Si:H/a-Si_1-xN_x:H superlattices resulting in the creation of fewer interface defects than the superlattices prepared without the hydrogen plasma.     

Effects of 7.5% CO2 inhalation on allocation of spatial attention to facial cues of emotional expression

Increased vigilance to threat-related stimuli is thought to be a core cognitive feature of anxiety. We sought to investigate the cognitive impact of experimentally induced anxiety, by means of a 7.5% CO₂ challenge, which acts as an unconditioned anxiogenic stimulus, on attentional bias for positive and negative facial cues of emotional expression in the dot-probe task. In two experiments we found robust physiological and subjective effects of the CO₂ inhalation consistent with the claim that the procedure reliably induces anxiety. Data from the dot-probe task demonstrated an attentional bias to emotional facial expressions compared with neutral faces regardless of valence (happy, angry, and fearful). These attentional effects, however, were entirely inconsistent in terms of their relationship with induced anxiety. We conclude that the previously reported poor reliability of this task is the most parsimonious explanation for our conflicting findings and that future research should develop a more reliable paradigm for measuring attentional bias in this field.     

The influence of the menstrual cycle on reactivity to a CO2 challenge among women with and without premenstrual symptoms

Clinically significant premenstrual symptoms (PMS) is conceptualized as a depressive disorder in DSM-5, however, it may share pathophysiological processes with anxiety- and fear-related disorders. Specifically, women with PMS panic at higher rates during biological challenge procedures. It is unclear if this increased interoceptive sensitivity is a general vulnerability or specific to the premenstrual phase. The current study examined the role of menstrual cycle phase on reactivity to a CO₂ challenge among women with (n = 11) and without (n = 26) clinically significant PMS (N = 37). During the late follicular phase (days 6–12), women with and without PMS responded similarly to the CO₂ challenge, whereas during the premenstrual phase (within 5 days before menses), women with PMS reported significantly more intense panic symptoms in response to the challenge than women without PMS. Vulnerability to panic in women with PMS may be specific to the premenstrual phase. Potential psychological and neurobiological mechanisms underlying this phenomenon are discussed.     

Effect of heat treatment on the NO2-sensing properties of sputter-deposited indium tin oxide thin films

Transparent conducting indium tin oxide (ITO) films were deposited onto glass substrates by radio-frequency magnetron sputtering at 648?K, under an oxygen partial pressure of 1?Pa. The effect of annealing on the electrical properties of the films was studied. Characterization of the coatings revealed an electrical resistivity below 6.5?×?10^??3?Ω?cm. The ITO films deposited at 648?K were amorphous, while the crystallinity improved after annealing at 700?K. The surface morphology examined by scanning electron microscopy appears to be uniform over the entire surface area after annealing. The NO₂-sensing properties of the ITO films were investigated and showed sensitivity at concentrations lower than 50?ppm, at a working temperature of 600?K.     

Enhanced learning by posttrial injection of H1-but not H2-histaminergic antagonists into the nucleus basalis magnocellularis region

The aim of this study was to examine the effects of histaminergic antagonists on memory upon injection into the region of the nucleus basalis magnocellularis (NBM). In experiment 1, rats with chronically implanted cannulae were trained on the uphill avoidance task, which involves a punishment of a high-probability turning response on a tilted platform (negative geotaxis). Immediately after the training trial, that is, after a tail shock was administered upon performing the response, rats received one microinjection (0.5 microliter) of H1-receptor blocker chlorpheniramine (dose range 0.1 to 20 microgram) or the H2-receptor blocker ranitidine (same dose range) or saline into the NBM region. When tested 24 h later, rats treated with chlorpheniramine (20 micrograms) had significantly longer uphill latencies than vehicle controls and ranitidine-treated animals, indicative of superior learning of the avoidance response. In experiment 2, a test for possible proactive effects of posttrial chlorpheniramine on performance during the retention trial was performed. Animals were injected with either 20 micrograms chlorpheniramine or saline immediately after the training trial of the uphill task. One chlorpheniramine control group was treated with a delay of 5 h. Additional groups which received chlorpheniramine or vehicle after the training trial but no trail shock were included. When tested 24 h later, rats injected with 20 micrograms chlorpheniramine again exhibited significantly longer uphill latencies than did vehicle-injected rats. Retention latencies for the rats of the chlorpheniramine 5-h delayed group did not differ from those of the vehicle-injected rats, ruling out proactive effects of chlorpheniramine on performance. In summary, the histaminergic H1-blocker chlorpheniramine can enhance mnemonic functioning in addition to its reinforcing effects upon NBM injection as reported previously.     

Differential effects of massage and heelstick procedures on transcutaneous oxygen tension in preterm neonates

The present study investigated the differential effects of heelsticks and tactile-kinesthetic massage on transcutaneous oxygen tension (TcPO₂) in preterm infants. The sample was comprised of 37 stabilized preterm neonates from the Neonatal Intensive Care Unit. During the heelstick procedure, TcPO₂ significantly declined an average of 14 mmHg. When compared to the tactile-kinesthetic massage, TcPO₂ levels during the heelstick (M = 39.8) were significantly lower than during the stimulation (M = 72.8). Mean TcPO₂ levels remained clinically safe during the four massage sessions evaluated. The TcPO₂ levels during kinesthetic stimulation were somewhat more varied, and movement and pressurization of the TcPO₂ electrode were investigated as possible artifactual explanations for this phenomenon. Overall, the findings indicate that social forms of touch such as tactile-kinesthetic massage do not appear to have a medically compromising effect on TcPO₂ in the preterm neonate. These findings are evaluated in relation to the “minimal touch” policy, and implications for future handling of the stabilized preterm neonate are discussed.     

Assessing the Predictive Accuracy of hMLH1 and hMSH2 Mutation Probability Models

Hereditary nonpolyposis colorectal cancer (HNPCC) is characterized by a susceptibility to colorectal and extra-colonic cancers. Several guidelines exist for the identification of families suspected of having HNPCC, however these guidelines lack adequate sensitivity and specificity. In an attempt to improve accuracy for the detection of individuals with HNPCC, the Wijnen pre-test probability model (1998) and Myriad Genetics Laboratory prevalence table (2004) were developed. Here we evaluate the Wijnen model and Myriad table at predicting the presence of a mutation in individuals undergoing genetic testing for HNPCC. Forty-nine patients who had undergone genetic testing for germline mutations in hMLH1 and/or hMSH2 were part of our analysis. Our results revealed that the revised Bethesda guidelines performed with the highest sensitivity for germline mutations (94.4%), however the specificity was low (12.9%). Using a 10.0% mutation probability threshold, the Wijnen model and Myriad table had sensitivities of 55.6 and 60.0%, respectively and specificities of 54.8 and 23.8%, respectively. The Wijnen model and Myriad table were poor predictors of mutation prevalence, which is shown by the areas underneath their corresponding receiver operator characteristic curves (0.616 and 0.400, respectively). The results of this study demonsrate that neither the Wijnen model nor the Myriad table are sensitive or specific enough to be used as the only indication when to offer genetic testing for HNPCC.     

Ezekiel’s classic estimator of the population squared multiple correlation coefficient: Monte Carlo-based extensions and refinements

Abstract

Ezekiel’s adjusted R² is widely used in linear regression analysis. The present study examined the statistical properties of Ezekiel’s measure through a series of Monte Carlo simulations. Specifically, we examined the bias and root mean squared error (RMSE) of Ezekiel’s adjusted R² relative to (a) the sample R² statistic, and (b) the sample R² minus the expected value of R². Simulation design factors consisted of sample sizes (N?=?50, 100, 200, 400), number of predictors (2, 3, 4, 5, 6), and population squared multiple correlations (ρ² = 0, .10, .25, .40, .60). Factorially crossing these design factors resulted in 100 simulation conditions. All populations were normal/Gaussian, and for each condition, we drew 10,000 Monte Carlo samples. Regarding systematic variation (bias), results indicated that with few exceptions, Ezekiel’s adjusted R² demonstrated the lowest bias. Regarding unsystematic variation (RMSE), the performance of Ezekiel’s measure was comparable to the other statistics, suggesting that the bias-variance tradeoff is minimal for Ezekiel’s adjusted R². Additional findings indicated that sample size-to-predictor ratios of 66.67 and greater were associated with low bias and that ratios of this magnitude were accompanied by large sample sizes (N?=?200 and 400), thus suggesting that researchers using Ezekiel’s adjusted R² should aim for sample sizes of 200 or greater in order to minimize bias when estimating the population squared multiple correlation coefficient. Overall, these findings indicate that Ezekiel’s adjusted R² has desirable properties and, in addition, these findings bring needed clarity to the statistical literature on Ezekiel’s classic estimator.     

AF-DX 116, a Presynaptic Muscarinic Receptor Antagonist, Potentiates the Effects of Glucose and Reverses the Effects of Insulin on Memory

Male Swiss mice were tested 24 h after training in a one-trial step-through inhibitory avoidance task. Low subeffective doses of -(+)-glucose (10 mg/kg, ip), but not its stereoisomer -(−)-glucose (30 mg/kg, ip), administered immediately after training, and AF-DX 116 (0.3 mg/kg, ip), a presynaptic muscarinic receptor antagonist, given 10 min after training, interact to improve retention. Insulin (8 IU/kg, ip) impaired retention when injected immediately after training, and the effects were reversed, in a dose-related manner, by AF-DX 116 (0.3, 1.0, or 3.0 mg/kg, ip) administered 10 min following insulin. Since AF-DX 116 possibly blocks autoreceptors mediating the inhibition of acetylcholine release from cholinergic nerve terminals, the present data support the view that changes in the central nervous system glucose availability, subsequent to modification of circulating glucose levels, influence the activity of central cholinergic mechanisms involved in memory storage of an inhibitory avoidance response in mice.     

The inclosure scheme and the solution to the paradoxes of self-reference

Proponents of the explanatory gap claim that consciousness is a mystery. No one has ever given an account of how a physical thing could be identical to a phenomenal one. We fully understand the identity between water and H₂O but the identity between pain and the firing of C-fibers is inconceivable. Mark Johnston [Journal of philosophy (1997), 564–583] suggests that if water is constituted by H₂O, not identical to it, then the explanatory gap becomes a pseudo-problem. This is because all “manifest kinds”—those identified in experience—are on a par in not being identical to their physical bases, so that the special problem of the inconceivability of ‘pain = the firing of C-fibers’ vanishes. Moreover, the substitute relation, constitution, raises no explanatory difficulties: pain can be constituted by its physical base, as can water. The thesis of this paper is that the EG does not disappear when we substitute constitution for identity. I examine four arguments for the EG, and show that none of them is undermined by the move from constitution to identity.