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Pleural effusions in the neonatal stage may result from chylothorax, hydrops fetalis, extravasation of percutaneously inserted central venous catheter, parapneumonic effusion, congestive heart failure, or other less frequently occurring conditions. Diagnostic chest tap is required for subsequent management. Good outcome is the rule except in hydrops fetalis, which carries high mortality rate.

Silica, sharing the same tetrahedral order and many structural, thermodynamic and dynamic anomalies with water, has been speculated to have a density increase upon melting similar to water. In this work, an increase in density upon melting cristobalite silica and a shallow density maximum followed by a density minimum during cooling of silica liquid are observed in classical molecular dynamics simulations. The density maximum gradually diminishes with the increase in alkali size/content in alkali silicate glasses. The structural origin of the anomalous density maximum in silica is revealed by detailed structural analysis. During the cooling process, a range of rings with different sizes form in liquid silica, with 6-member rings being the most dominant, which cause the silica network to open up and compensate the regular volume shrinkage upon cooling. These two competing factors lead to a density maximum, but to a less extent than that observed in melting of cristobalite silica. With the increase in modifier size/content in the alkali silicate glasses, the connectivity of silica network gradually breaks down; the population of 6-member rings decrease with the increase in smaller or larger rings, therefore the density maximum becomes less obvious and eventually disappears. K E Y W O R D Satomistic simulation, density maximum, silica, silicates

The mixed modifier effect (MME) in the lithium‐calcium borosilicate glasses, which have a composition of 0.4[(1−x)Li2O–xCaO]–0.6[(1−y)B2O3–ySiO2] with x in the range of 0~1 and y in the range of 0.33~0.83, is investigated. The MME manifests itself as a positive deviation from linearity in the activation energy of electrical conductivity (Eaσ) and as a negative deviation from linearity in the fraction of four‐coordinated boron (N4), glass transition temperature (Tg), dilatometric softening temperature (Td), Vickers microhardness (Hv), dielectric constant (ε), and dielectric loss (tanδ). Moreover, the deviation, which exhibits a maximum at [CaO]/([CaO]+[Li2O])=0.5, is enhanced with increasing [SiO2]/[B2O3] ratio in the glass network. The observed MME in Tg, Td, and Hv are attributed to the bond weakening in the network; however, the MME in ε, tanδ, and Eaσ are caused by the obstruction of modifier transport in the glass network.

This manuscript explores the connection between the fast relaxation processes in an undeformed polymer glass and essential trends in the mechanical toughness, a nonlinear mechanical property that is of practical interest for engineering polymers with high impact strength. We quantify the time scale of the molecular relaxations in the subnanosecond regime for a quiescent polycarbonate glass using inelastic and quasi-elastic neutron scattering and then correlate these processes with the macroscopic brittle-to-ductile transition (BDT), which demarcates a change in the dominant mechanism of failure and a marked increase in the material toughness. We show that the macroscopic phenomenon of the BDT corresponds to a change in the dominant dynamical process at the nanoscale. The brittle regime is characterized by collective vibrational modes (the so-called Boson peak) with a characteristic time scale τ ≈ 0.5–0.8 ps, while slower collective relaxations with τ ≈ 3 ps become dominant above the BDT. We further establish that the onset of ductility coincides with the appearance of anharmonicity in the mean-square atomic displacement ⟨u 2⟩ on a picosecond time scale, emphasizing that fast anharmonic molecular motions are important for energy dissipation. This builds upon our previous report correlating toughness with the amplitude of these anharmonic fluctuations across a wide range of polycarbonate glasses. Brillouin light scattering measurements are used to characterize the bulk and shear moduli of the material, revealing a concomitant upturn in Poisson’s ratio in the region of the BDT, a phenomenon that has been reported in metallic and oxide glasses. The ratio of transverse acoustic mode velocity and the Boson peak frequency is used to estimate the length scale for these processes, indicating that the dynamic heterogeneities are collective across 100–1000s of atoms. These length scales are strikingly similar to the activation volume of yield derived from mechanical measurements, suggesting that these fast and collective relaxation processes may be related to the mechanisms of yield.

Controlling nanoporosity to favorably impact multiple properties in layered crystalline inorganic thin films is a challenge. Here, we demonstrate that the thermoelectric and mechanical properties of Ca3Co4O9 films can be...

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