Lattice distortion enabling enhanced strength and plasticity in high entropy intermetallic alloy.

Intermetallic alloys have traditionally been characterized by their inherent brittleness due to their lack of sufficient slip systems and absence of strain hardening. However, here we developed a single-phase B2 high-entropy intermetallic alloy that is both strong and plastic. Unlike conventional intermetallics, this high-entropy alloy features a highly distorted crystalline lattice with complex chemical order, leading to multiple slip systems and high flow stress. In addition, the alloy exhibits a dynamic hardening mechanism triggered by dislocation gliding that preserves its strength across a wide range of temperatures. As a result, this high-entropy intermetallic circumvents precipitous thermal softening, with extensive plastic flows even at high homologous temperatures, outperforming a variety of both body-centered cubic and B2 alloys. These findings reveal a promising direction for the development of intermetallic alloys with broad engineering applications.

Duty-related trauma and PTSD symptoms in US urban firefighters.

BACKGROUND: Little is known about the multi-dimensional nature of traumatic duty-related events encountered by firefighters in relation to their post-traumatic stress disorder (PTSD) risk. AIMS: To describe the types of duty-related events encountered by career firefighters and explore if years in the fire service or total event load moderated the association of trauma exposure to PTSD symptoms. METHODS: Participants included 755 career, male firefighters (19% of the department's firefighters and 76% of those who accessed the electronic anonymous survey). The Duty-Related Incident Stressors scale was used to assess exposure to 25 potentially traumatic events (event load) and self-appraisal of the stress associated with these events, grouped by type of event (indirect, direct and colleague-related). The Post-Traumatic Stress Disorder Checklist was used to assess PTSD symptoms. RESULTS: Firefighters rated colleague-related events as the most stressful, followed by indirect and direct events. Event load (r = 0.25) and indirect, direct and colleague-related events stress (r = 0.32-0.35) were positively associated with PTSD symptoms. Results of moderation analyses indicated that event load served as a risk factor in the relation of indirect events stress to PTSD symptoms, and as a buffer in the relation of direct events stress to PTSD symptoms. Years in the fire service were not associated with PTSD symptoms nor moderated the relation of event stress to PTSD symptoms. CONCLUSIONS: Findings underscored the importance of considering the differential effects that types of duty-related traumatic events and cumulative exposure to trauma may have on firefighters' PTSD symptoms.

Early Pseudomonas aeruginosa predicts poorer pulmonary function in preschool children with cystic fibrosis.

BACKGROUND: We previously reported relatively normal pulmonary function (2 years of age) and computed tomography (CT, 1 year of age) in cystic fibrosis (CF) newborn screened (NBS) infants. We now report follow up of these children to preschool age. METHODS: 67 NBS children with CF and 41 healthy controls underwent pulmonary function tests in infancy (∼3 months, 1 year and 2 years) and at preschool (3-6 years). Broncho-alveolar lavage (BAL) and CT were undertaken in those with CF at 1 year. Primary outcomes at preschool were lung clearance index (LCI) and forced expired volume (FEV0.75). Risk factors for lung function impairment were identified by regression modelling, emphasising factors that could be identified or measured in the first 2 years of life. RESULTS: At preschool age children with CF had poorer lung function than controls, mean(95% CI) difference in LCI z-score: 1.47(0.96;1.97) and FEV0.75 z-score -0.54(-0.98; -0.10). Isolation of Pseudomonas aeruginosa before 6 months was a highly significant predictor of raised (abnormal) preschool LCI, associated with a mean (95%CI) increase of 1.69(0.43, 2.95) z-scores, compared to those with no Pseudomonas aeruginosa during the first 2 years of life. Including 2 year LCI and 1 year CT data in the predictive model increased the r2 from 13% to 61%. CONCLUSIONS: Lung function deteriorates after 2 years in NBS children with CF. Isolation of Pseudomonas aeruginosa before 6 months and minor abnormalities of infant lung function tests and CT in infancy are associated with higher preschool LCI.

A highly distorted ultraelastic chemically complex Elinvar alloy.

The development of high-performance ultraelastic metals with superb strength, a large elastic strain limit and temperature-insensitive elastic modulus (Elinvar effect) are important for various industrial applications, from actuators and medical devices to high-precision instruments1,2. The elastic strain limit of bulk crystalline metals is usually less than 1 per cent, owing to dislocation easy gliding. Shape memory alloys3-including gum metals4,5 and strain glass alloys6,7-may attain an elastic strain limit up to several per cent, although this is the result of pseudo-elasticity and is accompanied by large energy dissipation3. Recently, chemically complex alloys, such as 'high-entropy' alloys8, have attracted tremendous research interest owing to their promising properties9-15. In this work we report on a chemically complex alloy with a large atomic size misfit usually unaffordable in conventional alloys. The alloy exhibits a high elastic strain limit (approximately 2 per cent) and a very low internal friction (less than 2 × 10-4) at room temperature. More interestingly, this alloy exhibits an extraordinary Elinvar effect, maintaining near-constant elastic modulus between room temperature and 627 degrees Celsius (900 kelvin), which is, to our knowledge, unmatched by the existing alloys hitherto reported.

The effect of orbital-lattice coupling on the electrical resistivity of YBaCuFeO5 investigated by X-ray absorption.

Temperature-dependent X-ray absorption near-edge structures, X-ray linear dichroism (XLD) and extended X-ray absorption fine structure (EXAFS) spectroscopic techniques were used to investigate the valence state, preferred orbital and local atomic structure that significantly affect the electrical and magnetic properties of a single crystal of YBaCuFeO5 (YBCFO). An onset of increase of resistivity at ~180 K, followed by a rapid increase at/below 125 K, is observed. An antiferromagnetic (AFM)-like transition is close to the temperature at which the resistivity starts to increase in the ab-plane and is also observed with strong anisotropy between the ab-plane and the c-axis. The XLD spectra at the Fe L3,2-edge revealed a change in Fe 3d eg holes from the preferential [Formula: see text] orbital at high temperature (300-150 K) to the [Formula: see text] orbital at/below 125 K. The analysis of the Fe K-edge EXAFS data of YBCFO further revealed an unusual increase in the Debye-Waller factor of the nearest-neighbor Fe-O bond length at/below 125 K, suggesting phonon-softening behavior, resulting in the breaking of lattice symmetry, particularly in the ab-plane of Fe-related square pyramids. These findings demonstrate a close correlation between electrical resistivity and coupling of the preferred Fe 3d orbital with lattice distortion of a single crystal of YBCFO.

Evolution of superconductivity in K2-xFe4+ySe5: Spectroscopic studies of X-ray absorption and emission.

This study investigates the evolution of superconductivity in K2-xFe4+ySe5 using temperature-dependent X-ray absorption and resonant inelastic X-ray scattering techniques. Magnetization measurements show that polycrystalline superconducting (SC) K1.9Fe4.2Se5 has a critical temperature (T c) of ∼31 K with a varying superconducting volume fraction, which strongly depends on its synthesis temperature. An increase in Fe-structural/vacancy disorder in SC samples with more Fe atoms occupying vacant 4d sites is found to be closely related to the decrease in the spin magnetic moment of Fe. Moreover, the nearest-neighbor Fe-Se bond length in SC samples exceeds that in the non-SC (NS) sample, K2Fe4Se5, which indicates a weaker hybridization between the Fe 3d and Se 4p states in SC samples. These results clearly demonstrate the correlations among the local electronic and atomic structures and the magnetic properties of K2-xFe4+ySe5 superconductors, providing deeper insight into the electron pairing mechanisms of superconductivity.

PTSD symptoms and suicidal ideation in US female firefighters.

BACKGROUND: Little is known regarding the mental health of women firefighters. AIMS: To identify demographic, work-related and mental health characteristics associated with post-traumatic stress disorder (PTSD) symptoms and lifetime suicidal ideation in female firefighters compared with male colleagues. METHODS: Participants were firefighters (75 women and 2564 men) employed in a large urban fire department in the USA. Chi-square, correlations, t-tests and analyses of variance were conducted to examine the predictors of PTSD symptoms and lifetime suicide ideation in men and women. RESULTS: Approximately 20% of women scored positively for PTSD and 30% reported lifetime suicidal ideation. Women with PTSD symptoms were more likely to be in their mid-career years (11-20) than in their first 10 years (87% versus 44%; χ2 = 8.77, P < 0.05) and to have received counselling (53% versus 14%; χ2 = 8.11, P < 0.01). Being single (73% versus 58%; χ2 = 6.02, P < 0.05), having a second job (68% versus 38%; χ2 = 5.79, P < 0.05) and having received counselling (41% versus 11%; χ2 = 8.51, P < 0.01) predicted suicide ideation. Depression and general stress positively predicted PTSD symptoms and suicide ideation. PTSD also predicted suicide ideation. CONCLUSIONS: Compared to male firefighters, women were at high risk for PTSD symptoms and suicide ideation. Particularly for women, few socio-demographic and work-related variables were associated with these outcomes. Mental health variables predicted depression and suicide ideation for both gender groups. Therefore, in screening and intervention efforts, it may be most fruitful to focus on mental health risk correlates of PTSD and suicide ideation.

Anisotropy in the magnetic interaction and lattice-orbital coupling of single crystal Ni3TeO6.

This investigation reports on anisotropy in the magnetic interaction, lattice-orbital coupling and degree of phonon softening in single crystal Ni3TeO6 (NTO) using temperature- and polarization-dependent X-ray absorption spectroscopic techniques. The magnetic field-cooled and zero-field-cooled measurements and temperature-dependent Ni L3,2-edge X-ray magnetic circular dichroism spectra of NTO reveal a weak Ni-Ni ferromagnetic interaction close to ~60 K (TSO: temperature of the onset of spin ordering) with a net alignment of Ni spins (the uncompensated components of the Ni moments) along the crystallographic c-axis, which is absent from the ab-plane. Below the Néel temperature, TN~ 52 K, NTO is stable in the antiferromagnetic state with its spin axis parallel to the c-axis. The Ni L3,2-edge X-ray linear dichroism results indicate that above TSO, the Ni 3d eg electrons preferentially occupy the out-of-plane 3d3z2-r2 orbitals and switch to the in-plane 3dx2-y2 orbitals below TSO. The inherent distortion of the NiO6 octahedra and anisotropic nearest-neighbor Ni-O bond lengths between the c-axis and the ab-plane of NTO, followed by anomalous Debye-Waller factors and orbital-lattice in conjunction with spin-phonon couplings, stabilize the occupied out-of-plane (3d3z2-r2) and in-plane (3dx2-y2) Ni eg orbitals above and below TSO, respectively.