Surface tension of substantially undercooled liquid Ti–Al alloy

It is usually difficult to undercool Ti–Al alloys on account of their high reactivity in the liquid state. This results in a serious scarcity of information on their thermophysical properties in the metastable state. Here, we report on the surface tension of a liquid Ti–Al alloy under high undercooling condition. By using the electromagnetic levitation technique, a maximum undercooling of 324 K (0.19 T _L) was achieved for liquid Ti-51 at.% Al alloy. The surface tension of this alloy, which was determined over a broad temperature range 1429–2040 K, increases linearly with the enhancement of undercooling. The experimental value of the surface tension at the liquidus temperature of 1753 K is 1.094 N m^?1 and its temperature coefficient is ?1.422 × 10^?4 N m^?1 K^?1. The viscosity, solute diffusion coefficient and Marangoni number of this liquid Ti–Al alloy are also derived from the measured surface tension.     

Surface tension measurement of undercooled liquid Ni-based multicomponent alloys

The surface tensions of liquid ternary Ni–5%Cu–5%Fe, quaternary Ni–5%Cu–5%Fe–5%Sn and quinary Ni–5%Cu–5%Fe–5%Sn–5%Ge alloys were determined as a function of temperature by the electromagnetic levitation oscillating drop method. The maximum undercoolings obtained in the experiments are 272 (0.15T _L), 349 (0.21T _L) and 363?K (0.22T _L), respectively. For all the three alloys, the surface tension decreases linearly with the rise of temperature. The surface tension values are 1.799, 1.546 and 1.357?N/m at their liquidus temperatures of 1719, 1644 and 1641?K. Their temperature coefficients are ?4.972?×?10^–4, ?5.057?×?10^?4 and ?5.385?×?10^?4?N/m/K. It is revealed that Sn and Ge are much more efficient than Cu and Fe in reducing the surface tension of Ni-based alloys. The addition of Sn can significantly enlarge the maximum undercooling at the same experimental condition. The viscosity of the three undercooled liquid alloys was also derived from the surface tension data.     

Dendrite growth velocity in the undercooled melt of glass forming Ni50Zr50 compound

Glass-forming Ni₅₀Zr₅₀ intermetallic compound is containerless undercooled and solidified using electrostatic levitation. Large undercoolings up to ?T = 300 K are achieved. The dendrite growth velocity of the congruently melting alloy is measured as a function of undercooling using a high-speed camera technique. The experimental data is analysed within a sharp interface theory. It is found that the driving force of crystallisation is controlling the growth kinetics at ?T < 250 K but at larger undercoolings the growth kinetics is progressively controlled by atomic diffusion. This leads to a slowing down of the growth velocity. The maximum velocity and the temperature at which the maximum occurs (T_max) are inferred from the dendrite growth velocity – undercooling relation. The relation of the temperature T_max and the glass temperature fits into a general classification scheme for glass-forming systems. The kinetic and thermal undercooling terms are calculated within dendrite growth theory as a function of the total undercooling. At ?T > 126 K, the kinetic undercooling dominates and increases rapidly with the undercooling ?T. The maximum prefactor of the kinetic undercooling is plotted vs. the reciprocal temperature. Its temperature dependence is discussed.     

The order–dsorder transition at twin boundaries in Cu3Au as studied by TEM

Abstract

The order-disorder phase transition at ∑ = 3{111}- and {211}-type twin boundaries has been studied in the L1²-ordered alloy Cu³Au employing in situ heating in a transmission electron microscope. Evidence is presented for an order-disorder phase transition occurring in these boundaries prior to the bulk transition. The temperature difference ΔT between the transition temperature of both boundary types and the bulk is estimated as 0.5K <ΔT<2K. No difference in T _c for the twin boundaries can be established as yet. The nature of the order-disorder transition in both twin boundaries is presumably a second-order phase transition.     

Illness representations predict adherence in adolescents and young adults with type 1 diabetes

Objective: Most adolescents and young adults (AYAs) with type 1 diabetes struggle with diabetes self-management and exhibit suboptimal glycemic control. This study examined two models of association between illness representations, a modifiable predictor of suboptimal outcomes, and adherence and glycemic control in AYAs with type 1 diabetes.

Design and main outcome measures: Ninety-nine AYAs (ages 15–20?years) completed measures of illness representations and adherence at two visits. Blood glucose monitoring frequency and haemoglobin A1c were obtained via chart review. Relationships were examined using structural equation modelling.

Results: Illness representations accounted for a significant proportion of the variance in blood glucose monitoring frequency (ΔR^2?=?.23, p?<?.01) and adherence to emergency precautions at Time 1 (ΔR^2?=?.07, p?=?.03). Illness representations also accounted for significant variance in blood glucose monitoring frequency (ΔR^2?=?.08, p?=?.01), adherence to recommendations for insulin and food (ΔR²?=?.08, p?=?.02) and exercise (ΔR^2?=?.10, p?<?.01), and adherence to emergency precautions (ΔR^2?=?.16, p?<?.01) at Time 2.

Conclusion: Illness representations are salient predictors of adherence in this population. Interventions targeting adherence promotion and glycemic control in AYAs with type 1 diabetes may be enhanced by efforts to modify illness representations.     

Distancing oneself from God: relationships with borderline personality symptomatology

Self-harm behaviour traditionally has been associated with borderline personality disorder. In this study, we examined the relationship between borderline personality symptomatology and intentionally distancing oneself from God as self-punishment, based on the assumption that such self-punishment may represent a form of self-harm behaviour. Data from four previous samples of primary care outpatients collected over a two-year period were combined (N?=?1511). Borderline personality was assessed with two measures: the borderline personality scale of the Personality Diagnostic Questionnaire-4 (PDQ-4) and the Self-Harm Inventory (SHI). Point-biserial correlation coefficients revealed that those who endorsed distancing oneself from God as punishment scored relatively higher on both the PDQ-4 (r?=?0.40, p?<?0.001) and the SHI (r?=?0.46, p?<?0.001). Similarly, when compared to respondents who denied ever having distanced themselves from God as punishment, those who did were more likely to exceed the clinical cut-off score on the PDQ-4 (47.3% vs. 10.9%, X^{2 ?}=?152.53, p?<?0.001) and the SHI (57.3% vs. 11.4%, X^{2 ?}=?224.12, p?<?0.001). Findings support our hypothesis that distancing oneself from God as punishment may be a form of self-harm behaviour associated with borderline personality symptomatology.     

Thermophysical properties of substantially undercooled liquid Ti-Al-Nb ternary alloy measured by electromagnetic levitation

The thermophysical properties of undercooled liquid alloys at high temperature are usually difficult to measure by experiment. Here, we report the specific heat of liquid Ti₄₅Al₄₅Nb₁₀ ternary alloy in the undercooled state. By using electromagnetic levitation technique, a maximum undercooling of 287?K (0.15 T _L) is achieved for this alloy. Its specific heat is determined to be 32.72?±?2.51?J?mol^?1 K^?1 over a broad temperature range of 1578–2010?K.     

Meaning in life,emotional distress,suicidal ideation,and life functioning in an active duty military sample

The present study examined the relationship of meaning in life with emotional distress, suicidal ideation, and life functioning in a sample of 273 active duty Security Forces personnel assigned to two US Air Force bases. Results of regression analyses indicated that stronger meaning in life was significantly associated with less severe emotional distress (p?<?0.001, ΔR ²?=?0.047) and suicidal ideation (p?=?0.043, ΔR ²?=?0.017), and better functioning at work and in intimate relationships, nonfamily relationships, and recreational activities (p?<?0.001, ΔR ²?=?0.073). Meaning in life showed stronger associations with outcomes relative to other predictors and covariates and explained the relationship between belonging and life functioning. Findings suggest that meaning in life is associated with less emotional distress and suicide risk, and greater success and performance across multiple domains in life among military personnel.     

Two alternative models of health behaviour and recovery from activity limitations due to acute injury: A prospective study

Cognitions influence recovery from activity limitations. In this study we aimed to independently test, compare and combine the common sense self-regulation model (CS-SRM) and social cognitive theory (SCT) in predicting recovery from activity limitations due to acute injury. Measures were gathered at two time points 5–6 weeks apart. The sample consisted of 146 university students (Mean age: 21.86, SD: 4.83, 62% female) with a heterogeneous range of injuries that limited their participation in physical activity. The dependent variable was recovery from activity limitations (Physical Functioning?–?Short Form-36). The predictor variables were measured using the Brief Illness Perception Questionnaire and SCT items designed according to theoretical recommendations. Time-line (TL) and self-efficacy (SE) were significant predictors of recovery in a multivariate analysis, controlling for reported pain at Time 1. A combined model including the best predictors from both models, TL (β = ?0.25, p < 0.05, R ² change = 0.17, p < 0.01) and SE (β =0.31, p < 0.05, R ² change = 0.05, p < 0.05), accounted for a significant amount of the variance in recovery from activity limitations. A combination of key variables from both models may be particularly useful for understanding the cognitive factors that influence recovery from activity limitations.     

Conditional probability and pragmatic conditionals: Dissociating truth and effectiveness

Recent research (e.g., Evans & Over, 2004 Over, D. E., Manktelow, K. I. and Hadjichristidis, C. 2004. Conditions for the acceptance of deontic conditionals. Canadian Journal of Experimental Psychology, 58: 111–120.  [Google Scholar]) has provided support for the hypothesis that people evaluate the probability of conditional statements of the form if p then q as the conditional probability of q given p, P(q/p). The present paper extends this approach to pragmatic conditionals in the form of inducements (i.e., promises and threats) and advice (i.e., tips and warnings). In so doing, we demonstrate a distinction between the truth status of these conditionals and their effectiveness as speech acts. Specifically, while probability judgements of the truth of conditional inducements and advice are highly correlated with estimates of P(q/p), their perceived effectiveness in changing behaviour instead varies as a function of the conditional probability of q given not-p, P(q/～p). Finally, we show that the conditional probability approach can be extended to predicting inference rates on a conditional reasoning task.     

Electrical properties and local structure of n-type conducting amorphous indium sulphide

An n-type amorphous chalcogenide, In₄₉S₅₁, having a band gap of 1.9eV, has been found. The conductivity in as-prepared films was ～10^?4?S?cm^?1, which increased to 1?×?10^?1?S?cm^?1 on post-annealing at 125°C in vacuum, accompanied by a reduction in the sulphur content of the films. TEM observations showed the amorphous nature of the films before and after annealing. Both Seebeck and Hall coefficients are negative, indicating that the major carriers are electrons. The Hall mobility can be as large as 26?cm²?V^?1?s^?1 at 300?K. No significant changes to the optical absorption were observed upon annealing. Analysis of the X-ray radial distribution function reveals that the sulphur atoms have four-fold coordination, making the structure more rigid than conventional amorphous chalcogenides in which the chalcogen is alloyed to elements of group IV or V of the periodic table. We tentatively associate the electron carrier generation with the formation of sulphur vacancies.     

A strong developmental theory of field dependence-independence

Assume an X-linked gene in two alleles mediates performance on field dependent-independent tests such as the rod-and-frame test. Only the recessive gene with relative frequency q facilitates field independence. Other genotypes lead to field dependence. Under a simple genetic model, field dependence-independence may be viewed as outcomes of a discrete random variable B with field independent and dependent probabilities π_iq and 1 ? π_iq for men, and π_iq² and 1 ? π_iq² for women, respectively. The parameter π_i is a maturational ageindexed parameter, 0 < π_i ≤ 1, monotonically increasing with development until maturity when π_k = 1. Observations of performance are made on a random variable W of the form W = B + N, where N is normal in distribution independent of B; N represents a composite of influences including error. The model implies testable age-related between- and within-sex predictions regarding E(W) and Var(W), predictions which appear to coincide with major empirical findings; it also generates novel predictions. For instance, W is a mixture of normals distribution. The model is briefly evaluates in two data sets.     

Mechanical spectroscopy of a high-Nb-bearing γ-TiAl-based alloy with near-gamma and fully lamellar microstructure

Intermetallic γ-TiAl sheet material of composition Ti–46?at.%Al–9?at.%Nb and two different microstructures (fine-grained near-gamma and coarse-grained fully lamellar) was studied by mechanical-loss (internal-friction) measurements using two frequency ranges: (I) 0.01–10?Hz and (II) around 2?kHz. The mechanical spectra in range I show (i) a loss peak of Debye type at T?≈?1000?K, which occurs only in fully lamellar samples; and (ii) a high-temperature damping background above?≈?1100?K. The values of the activation enthalpy H of the high-temperature background, 4.3?eV (near-gamma) and 4.2?eV (fully lamellar), which were determined from the frequency shift, are distinctly higher than those obtained for TiAl sheet material with low Nb content. The high-temperature damping background is assigned to diffusion-assisted climb of dislocations, and the 1000?K peak (H?=?2.9?eV) to local (reversible) glide of dislocation segments anchored between lamella interfaces. From measurements of the eigenfrequency in range II, the variation of Young's modulus in the temperature range 300–1000?K was determined.     

Interpretation of the low-temperature photoconductivity in a-Si

Abstract

The paper is concerned with the interpretation of steady-state photoconductivity results on undoped a-Si at temperatures of 50K and below which lead to an essentially constant value of the (photogeneration efficiency x mobility x lifetime) product νμτ?10^?11 cm² V^?1. Measurements on p⁺-i-n⁺ junctions and Cr-i-n⁺ barriers were carried out to determine the above parameters separately: (i) steadystate reverse saturation currents gave a generation efficiency of ν? 5×10-² below 50K, suggesting that geminate recombination limits the generation process. (ii) the electron drift mobility μ_e through the tail states and the charge extracted from the absorption region of the incident light were investigated by transient experiments, these showed that μ_eτ_a is limited to about 3×10^?10cm²V^?1 at low T. The independent results account for the observed νμτ values and suggest that, contrary to the interpretation of Hoheisel, Carius and Fuhs (1984), the main contribution to the low-temperature photoconductivity arises from transport in tail states.     

Antiferromagnetic order and the structural order–disorder transition in the Cd6Ho quasicrystal approximant

It has generally been accepted that the orientational ordering of the Cd₄ tetrahedron within the Cd₆ R quasicrystal approximants is kinetically inhibited for R?=?Ho, Er, Tm and Lu by steric constraints. Our high-resolution X-ray scattering measurements of the Cd₆Ho quasicrystal approximant, however, reveal an abrupt (first-order) transition to a monoclinic structure below T _S?=?178?K for samples that have ‘aged’ at room temperature for approximately one year, reopening this question. Using X-ray resonant magnetic scattering at the Ho L ₃-edge we have elucidated the nature of the antiferromagnetic ordering below T _N?=?8.5?K in Cd₆Ho. The magnetic Bragg peaks are found at the charge forbidden H?+?K?+?L?=?2n?+?1 positions, referenced to the high-temperature body-centred cubic structure. In general terms, this corresponds to antiferromagnetic arrangements of the Ho moments on adjacent clusters in the unit cell as previously found for Cd₆Tb.     

Unusual room-temperature compressive plasticity in nanocrystal-toughened bulk copper-zirconium glass

Cast Cu₅₀Zr₅₀ alloy rods with a diameter of 1?mm have been found to consist of a glassy phase containing fine crystalline particles with a size of about 5?nm. They have a glass transition temperature T _g of 675?K, and a large supercooled-liquid region extending 57?K above T _g. The rods exhibit a high yield strength of 1860?MPa and a Young's modulus of 104?GPa. Because they contain a dispersion of embedded nanocrystals, the as-cast bulk metallic glass rods can sustain a compressive plastic strain at room temperature of more than 50%, an exceptional value which is explicable by compensation of any shear softening by nanocrystal coalescence and pinning of shear bands.     

Structural changes induced by low-energy electron irradiation in GaSb

Structural changes in GaSb (001) thin films upon low-energy electron (125?keV) irradiation have been studied by in situ transmission electron microscopy. No structural changes were observed for irradiation at room temperature. However, in a sample irradiated at 473?K domains of {110} variant, rotated 90° from each other, were formed in the matrix. The average diameter of the domains was approximately 18?nm in the sample irradiated to a fluence of 4.8?×?10²⁴?electrons/m². It is considered that the domains are pseudo-{110} planes in the matrix formed by electron-irradiation-induced Shockley partial dislocations.     

Microstructural development during transient directional solidification of a hypomonotectic Al–In alloy

Upward directional non-steady-state solidification experiments have been performed on a hypomonotectic Al–5.5?wt%In alloy. The alloy developed cellular as-solidified microstructure for tip growth rates, V _L, higher than 0.95?mm/s. The casting regions associated with V _L?<?0.95?mm/s were shown to be characterized by a microstructure formed by In droplets disseminated in the Al matrix. Tip growth rate and microstructural features, such as cell spacing and interphase spacing, have been experimentally determined. The experimental cell spacings have been compared with theoretical predictions furnished by the Hunt–Lu model. It was found that the experimental scatter lies below the minimum range of values theoretically predicted. Moreover, the experimental cell spacing evolution with V _L is characterized by a ?1.1 power law. The droplets’ interphase spacing, λ, is related to the growth rate by the Jackson–Hunt relationship (λ ² V _L?=?constant).     

The temporal architecture of central information processing: Evidence for a tentative time-quantum model

Summary A new, elaborated version of a time-quantum model (TQM) is outlined and illustrated by applying it to different experimental paradigms. As a basic prerequisite TQM adopts the coexistence of different discrete time units or (perceptual) intermittencies as constituent elements of the temporal architecture of mental processes. Unlike similar other approaches, TQM assumes the existence of an absolute lower bound for intermittencies, the time-quantum T, as an (approximately) universal constant and which has a duration of approximately 4.5 ms. Intermittencies of TQM must be multiples T _k=k·T ^* within the interval T ^*T _kL·T ^*M·T ^* with T ^*=q·T and integer q, k, L, and M. Here M denotes an upper bound for multipliers characteristic of individuals, the so-called coherence length; q and L may depend on task, individual and other factors. A second constraint is that admissible intermittencies must be integer fractions of L, the operative upper bound. In addition, M is assumed to determine the number of elementary information units to be stored in short-term memory.     

Must Differences in Cognitive Value be Transparent?

Frege’s ‘differential dubitability’ test is a test for differences in cognitive value: if one can rationally believe that p while simultaneously doubting that q, then the contents p and q amount to different ‘cognitive values’. If subject S is rational, does her simultaneous adoption of different attitudes towards p and q require that the difference between p and q (as cognitive values) be transparent to her? It is natural to think so. But I argue that, if attitude anti-individualism is true, then rational differential dubitability does not presuppose that differences in cognitive value are transparent. The significance of this argument lies in what it tells us, both about the notion of cognitive value and its relation to the differential dubitability test, but also about the prospects for a Burge-type position which aims to combine attitude anti-individualism with a (qualified) reliance on the differential dubitability test.