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  1. Magnetically trapped antihydrogen atoms can be cooled by expanding the volume of the trap in which they are confined. We report a proof-of-principle experiment in which antiatoms are deliberately released from expanded and static traps. Antiatoms escape at an average trap depth of0.08±0.01K(statistical errors only) from the expanded trap while they escape at average depths of0.22±0.01and0.17±0.01Kfrom two different static traps. (We employ temperature-equivalent energy units.) Detailed simulations qualitatively agree with the escape times measured in the experiment and show a decrease of38%(statisticalerror<0.2%) in the mean energy of the population after the trap expansion without significantly increasing antiatom loss compared to typical static confinement protocols. This change is bracketed by the predictions of one-dimensional and three-dimensional semianalytic adiabatic expansion models. These experimental, simulational, and model results are consistent with obtaining an adiabatically cooled population of antihydrogen atoms that partially exchanged energy between axial and transverse degrees of freedom during the trap expansion. This result is important for future antihydrogen gravitational experiments which rely on adiabatic cooling, and it will enable antihydrogen cooling beyond the fundamental limits of laser cooling.

    <supplementary-material><permissions><copyright-statement>Published by the American Physical Society</copyright-statement><copyright-year>2024</copyright-year></permissions></supplementary-material></sec> </div> <a href='#' class='show open-abstract' style='margin-left:10px;'>more »</a> <a href='#' class='hide close-abstract' style='margin-left:10px;'>« less</a> <div class="actions" style="padding-left:10px;"> <span class="reader-count"> Free, publicly-accessible full text available September 1, 2025</span> </div> </div><div class="clearfix"></div> </div> </li> <li> <div class="article item document" itemscope itemtype="http://schema.org/TechArticle"> <div class="item-info"> <div class="title"> <a href="https://par.nsf.gov/biblio/10489859-maximally-preorganized-tetrapyridyl-ligand-rigid-fivemembered-chelate-rings-enhance-selectivity-large-metal-ions-th-iv-uo-lanthanides-dft-thermodynamic-study" itemprop="url"> <span class='span-link' itemprop="name">A maximally preorganized tetra‐pyridyl ligand. Rigid five‐membered chelate rings enhance selectivity for large metal ions, such as Th(IV), UO 2 2+ and Lanthanides. A DFT and Thermodynamic study</span> </a> </div> <div> <strong> <a class="misc external-link" href="https://doi.org/10.1002/ejic.202300633" target="_blank" title="Link to document DOI">https://doi.org/10.1002/ejic.202300633  <span class="fas fa-external-link-alt"></span></a> </strong> </div> <div class="metadata"> <span class="authors"> <span class="author" itemprop="author">Uritis, Stuart</span> <span class="sep">; </span><span class="author" itemprop="author">Thummel, Randolph P.</span> <span class="sep">; </span><span class="author" itemprop="author">Jones, S. Bart</span> <span class="sep">; </span><span class="author" itemprop="author">Lee, Hee‐Seung</span> <span class="sep">; </span><span class="author" itemprop="author">Hancock, Robert D.</span> </span> <span class="year">( <time itemprop="datePublished" datetime="2024-02-05">February 2024</time> , European Journal of Inorganic Chemistry) </span> </div> <div style="cursor: pointer;-webkit-line-clamp: 5;" class="abstract" itemprop="description"> <title>Abstract

    Size‐based selectivity for metal ions based on highly preorganized five‐membered chelate rings is discussed. Metal ion complexation by the tetra‐pyridyl ligand EBIP ((8,9‐dihydro‐diquino[8,7‐b:7′,8′‐j][1,10]phenanthroline) is investigated, Formation constants (log K1) are reported for EBIP with 28 metal ions in 50 % CH3OH/H2O (v/v). The shift in size‐selectivity toward large metal ions and against small metal is demonstrated. Log K1for the EBIP complexes shows a steady increase from La(III) to Lu(III), with a strong local maximum at Sm(III), and strong local minimum at Gd(III). This difference in log K1between Sm(III) and Gd(III) for the tetra‐pyridyls is shown to depend largely on the level of preorganization of the ligand, being at a maximum for EBIP and a minimum for quaterpyridine. Log K1for the Y(III) complex is invariably lower than for the similarly‐sized Ho(III) for all ligands that contain any nitrogen donors. Lower log K values for Y(III) are due to stabilization of the Ln(III) complexes with nitrogen donors by participation of the 5d orbitals, and to a lesser extent the 4 f orbitals, of the Ln(III) ions in M−L bonding. A DFT analysis of selectivity of tetra‐pyridyls for metal ions shows that Y(III) complexes should be less stable than similarly‐sized Ho(III) complexes.

     
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  2. Paleomagnetic, rock magnetic, or geomagnetic data found in the MagIC data repository from a paper titled: Archeointensity of the Four Corners Region of the American Southwest 
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  3. Bateiha, S. ; Cobbs, G. (Ed.)
    This study highlights parents’ linguistic capital and how they use specific languaging practices to facilitate their child’s learning. One bilingual family used multiple languages to facilitate their son’s learning through two mathematical tasks. Using Dominguez’ conceptual framework of bilingualism, we analyzed these conversations to look for natural units of communication and its relation towards their problem solving goals. The data shows the family would switch from English to Spanish to help their child surpass several barriers during their mathematical activities. Leveraging bilingual languaging practices can counter the deficit lens with which minoritized students are typically viewed. 
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  4. Antiprotons created by laser ionization of antihydrogen are observed to rapidly escape the ALPHA trap. Further, positron plasmas heat more quickly after the trap is illuminated by laser light for several hours. These phenomena can be caused by patch potentials—variations in the electrical potential along metal surfaces. A simple model of the effects of patch potentials explains the particle loss, and an experimental technique using trapped electrons is developed for measuring the electric field produced by the patch potentials. The model is validated by controlled experiments and simulations. 
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  5. Abstract

    Danthonia californicaBolander (Poaceae)is a native perennial bunchgrass commonly used in the restoration of prairie ecosystems in the western United States. Plants of this species simultaneously produce both chasmogamous (potentially outcrossed) and cleistogamous (obligately self‐fertilized) seeds. Restoration practitioners almost exclusively use chasmogamous seeds for outplanting, which are predicted to perform better in novel environments due to their greater genetic diversity. Meanwhile, cleistogamous seeds may exhibit greater local adaptation to the conditions in which the maternal plant exists. We performed a common garden experiment at two sites in the Willamette Valley, Oregon, to assess the influence of seed type and source population (eight populations from a latitudinal gradient) on seedling emergence and found no evidence of local adaptation for either seed type. Cleistogamous seeds outperformed chasmogamous seeds, regardless of whether seeds were sourced directly from the common gardens (local seeds) or other populations (nonlocal seeds). Furthermore, average seed weight had a strong positive effect on seedling emergence, despite the fact that chasmogamous seeds had significantly greater mass than cleistogamous seeds. At one common garden, we observed that seeds of both types sourced from north of our planting site performed significantly better than local or southern‐sourced seeds. We also found a significant seed type and distance‐dependent interaction, with cleistogamous seedling emergence peaking approximately 125 km from the garden. These results suggest that cleistogamous seeds should be considered for greater use inD. californicarestoration.

     
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  6. Abstract

    Soil is the largest terrestrial carbon (C) reservoir and a large potential source or sink of atmospheric CO. Soil C models have usually focused on refining representations of microbe‐mediated C turnover, whereas lateral hydrologic C fluxes have largely been ignored at regional and global scales. Here, we provide large‐scale estimates of hydrologic export of soil organic carbon (SOC) and its effects on bulk soil C turnover rates. Hydrologic export of SOC ranged from nearly 0 to 12 g C m−2yr−1amongst catchments across the conterminous United States, and total export across this region was 14 (95% CI 4‐41) Tg C/yr. The proportion of soil C turnover attributed to hydrologic export ranged from <1% to 20%, and averaged 0.97% (weighted by catchment area; 95% CI 0.3%–2.6%), with the lowest values in arid catchments. Ignoring hydrologic export in C cycle models might lead to overestimation of SOC stocks by 0.3–2.6 Pg C for the conterminous United States. High uncertainty in hydrologic C export fluxes and potentially substantial effects on soil C turnover illustrate the need for research aimed at improving our mechanistic understanding of the processes regulating hydrologic C export.

     
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  7. Abstract

    Einstein’s general theory of relativity from 19151remains the most successful description of gravitation. From the 1919 solar eclipse2to the observation of gravitational waves3, the theory has passed many crucial experimental tests. However, the evolving concepts of dark matter and dark energy illustrate that there is much to be learned about the gravitating content of the universe. Singularities in the general theory of relativity and the lack of a quantum theory of gravity suggest that our picture is incomplete. It is thus prudent to explore gravity in exotic physical systems. Antimatter was unknown to Einstein in 1915. Dirac’s theory4appeared in 1928; the positron was observed5in 1932. There has since been much speculation about gravity and antimatter. The theoretical consensus is that any laboratory mass must be attracted6by the Earth, although some authors have considered the cosmological consequences if antimatter should be repelled by matter7–10. In the general theory of relativity, the weak equivalence principle (WEP) requires that all masses react identically to gravity, independent of their internal structure. Here we show that antihydrogen atoms, released from magnetic confinement in the ALPHA-g apparatus, behave in a way consistent with gravitational attraction to the Earth. Repulsive ‘antigravity’ is ruled out in this case. This experiment paves the way for precision studies of the magnitude of the gravitational acceleration between anti-atoms and the Earth to test the WEP.

     
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  8. The fourth orbit of Parker Solar Probe (PSP) reached heliocentric distances down to 27.9 R ⊙ , allowing solar wind turbulence and acceleration mechanisms to be studied in situ closer to the Sun than previously possible. The turbulence properties were found to be significantly different in the inbound and outbound portions of PSP’s fourth solar encounter, which was likely due to the proximity to the heliospheric current sheet (HCS) in the outbound period. Near the HCS, in the streamer belt wind, the turbulence was found to have lower amplitudes, higher magnetic compressibility, a steeper magnetic field spectrum (with a spectral index close to –5/3 rather than –3/2), a lower Alfvénicity, and a ‘1∕ f ’ break at much lower frequencies. These are also features of slow wind at 1 au, suggesting the near-Sun streamer belt wind to be the prototypical slow solar wind. The transition in properties occurs at a predicted angular distance of ≈4° from the HCS, suggesting ≈8° as the full-width of the streamer belt wind at these distances. While the majority of the Alfvénic turbulence energy fluxes measured by PSP are consistent with those required for reflection-driven turbulence models of solar wind acceleration, the fluxes in the streamer belt are significantly lower than the model predictions, suggesting that additional mechanisms are necessary to explain the acceleration of the streamer belt solar wind. 
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