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1. Low melt viscosity enables melt doublets above the 410-km discontinuity

   https://doi.org/10.1038/s41467-025-58518-7  

   Xie, Longjian; Andrault, Denis; Yoshino, Takashi; Han, Cunrui; Hammond, James_O S; Xu, Fang; Zhao, Bin; Lord, Oliver T; Fei, Yingwei; Falvard, Simon; et al (December 2025, Nature Communications)

   Abstract Seismic and magnetotelluric studies suggest hydrous silicate melts atop the 410 km discontinuity form 30–100 km thick layers. Importantly, in some regions, two layers are observed. These stagnant layers are related to their comparable density to the surrounding mantle, but their formation mechanisms and detailed structures remain unclear. Here we report a large decrease of silicate melt viscosity at ~14 GPa, from 96(5) to 11.7(6) mPa⋅s, as water content increases from 15.5 to 31.8 mol% H₂O. Such low viscosities facilitate rapid segregation of melt, which would typically prevent thick layer accumulation. Our 1D finite element simulations show that continuous dehydration melting of upwelling mantle material produces a primary melt layer above 410 km and a secondary layer at the depth of equal mantle-melt densities. These layers can merge into a single thick layer under low density contrasts or high upwelling rates, explaining both melt doublets and thick single layers. 

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2. Fate of Hydrous Fe‐Rich Silicate Melt in Earth's Deep Mantle

   https://doi.org/10.1029/2019GL083633  

   Du, Zhixue; Deng, Jie; Miyazaki, Yoshinori; Mao, Ho‐kwang; Karki, Bijaya_B; Lee, Kanani_K_M (August 2019, Geophysical Research Letters)

   Abstract Density of silicate melt dictates melt migration and establishes the gross structure of Earth's interior. However, due to technical challenges, the melt density of relevant compositions is poorly known at deep mantle conditions. Particularly, water may be dissolved in such melts in large amounts and can potentially affect their density at extreme pressure and temperature conditions. Here we perform first‐principles molecular dynamics simulations to evaluate the density of Fe‐rich, eutectic‐like silicate melt (Emelt) with varying water content up to about 12 wt %. Our results show that water mixes nearly ideally with the nonvolatile component in silicate melt and can decrease the melt density significantly. They also suggest that hydrous melts can be gravitationally stable in the lowermost mantle given its likely high iron content, providing a mechanism to explain seismically slow and dense layers near the core‐mantle boundary. 

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3. A Study of Call Graph Construction for JVM-Hosted Languages

   Ali, Karim; Lai, Xiaoni; Luo, Zhaoyi; Lhotak, Ondrej; Dolby, Julian; Tip, Frank (January 2019, IEEE transactions on software engineering)

   Call graphs have many applications in software engineering, including bug-finding, security analysis, and code navigation in IDEs. However, the construction of call graphs requires significant investment in program analysis infrastructure. An increasing number of programming languages compile to the Java Virtual Machine (JVM), and program analysis frameworks such as WALA and SOOT support a broad range of program analysis algorithms by analyzing JVM bytecode. This approach has been shown to work well when applied to bytecode produced from Java code. In this paper, we show that it also works well for diverse other JVM-hosted languages: dynamically-typed functional Scheme, statically-typed object-oriented Scala, and polymorphic functional OCaml. Effectively, we get call graph construction for these languages for free, using existing analysis infrastructure for Java, with only minor challenges to soundness. This, in turn, suggests that bytecode-based analysis could serve as an implementation vehicle for bug-finding, security analysis, and IDE features for these languages. We present qualitative and quantitative analyses of the soundness and precision of call graphs constructed from JVM bytecodes for these languages, and also for Groovy, Clojure, Python, and Ruby. However, we also show that implementation details matter greatly. In particular, the JVM-hosted implementations of Groovy, Clojure, Python, and Ruby produce very unsound call graphs, due to the pervasive use of reflection, invokedynamic instructions, and run-time code generation. Interestingly, the dynamic translation schemes employed by these languages, which result in unsound static call graphs, tend to be correlated with poor performance at run time. 

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4. A Solution for the Density Dichotomy Problem of Kuiper Belt Objects with Multispecies Streaming Instability and Pebble Accretion

   https://doi.org/10.3847/PSJ/ad1d5b  

   Cañas, Manuel H.; Lyra, Wladimir; Carrera, Daniel; Krapp, Leonardo; Sengupta, Debanjan; Simon, Jacob B.; Umurhan, Orkan M.; Yang 楊, Chao-Chin 朝欽; Youdin, Andrew N. (February 2024, The Planetary Science Journal)

   Abstract Kuiper Belt objects (KBOs) show an unexpected trend, whereby large bodies have increasingly higher densities, up to five times greater than their smaller counterparts. Current explanations for this trend assume formation at constant composition, with the increasing density resulting from gravitational compaction. However, this scenario poses a timing problem to avoid early melting by decay of²⁶Al. We aim to explain the density trend in the context of streaming instability and pebble accretion. Small pebbles experience lofting into the atmosphere of the disk, being exposed to UV and partially losing their ice via desorption. Conversely, larger pebbles are shielded and remain icier. We use a shearing box model including gas and solids, the latter split into ices and silicate pebbles. Self-gravity is included, allowing dense clumps to collapse into planetesimals. We find that the streaming instability leads to the formation of mostly icy planetesimals, albeit with an unexpected trend that the lighter ones are more silicate-rich than the heavier ones. We feed the resulting planetesimals into a pebble accretion integrator with a continuous size distribution, finding that they undergo drastic changes in composition as they preferentially accrete silicate pebbles. The density and masses of large KBOs are best reproduced if they form between 15 and 22 au. Our solution avoids the timing problem because the first planetesimals are primarily icy and²⁶Al is mostly incorporated in the slow phase of silicate pebble accretion. Our results lend further credibility to the streaming instability and pebble accretion as formation and growth mechanisms. 

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5. Low Density Plasma Waveguides Driven by Ultrashort (30 fs) and Long (300 ps) Pulses for Laser Wakefield Acceleration

   https://doi.org/10.1109/AAC.2018.8659410  

   Pagano, Isabella; Brooks, Jason; Bernstein, Aaron; Zgadzaj, Rafal; Leddy, Jarrod; Cary, John; Downer, Michael C. (August 2018, 2018 IEEE Advanced Accelerator Concepts Workshop)

   We simulate the possibility of scaling channel formation to low density plasmas of low atomic number gas over a large range of pulse duration including (1) pulses up to 300 ps in duration, using inverse bremsstrahlung (IB) heating and (2) ultrashort pulses up to 100s of femtoseconds for generating tenuous plasmas of centimeter to meter lengths by optical field ionization (OFI). Results show IB heating up to tens of eV, and channels formed from an initial density of 1e18 cm-􀀀3 with axial densities as low as 1e17cm-3 and radius of 50 microns. It has been shown that centimeter-scale waveguides can be generated via OFI heating at densities of approximately 1e17 cm-􀀀3. Lastly, we outline the experimental setup to be used in future experiments at the University of Texas Tabletop Terawatt (UT3) facility. 

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