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This paper directly links the abstract geometry of structural form-finding to the fabrication-aware design of discrete shells and spatial structures for 3D concrete printing through a bidirectional approach, where it creates surface-toolpath twins for the components, optimizing the buildability of the parts and their surface quality. The design-to-production process of efficient structural systems for 3D printing is often a top-down unidirectional process involving form-finding, segmentation, and slicing, where results face printability challenges due to incompatibility between the initial geometry and the printing system, as well as material constraints. We introduce surface-toolpath twins that can be interconverted and synchronized through efficient slicing and surface reconstruction algorithms to allow the combination of optimizations and modifications on either part of the twin in flexible orders. We provide two core methods for fabrication rationalization: (1) global buildability optimization on the surface mesh by normal-driven shape stylization and (2) local surface quality optimization on toolpath curves through intra-layer iterative adjustments. The result is a bidirectional design-to-production process where one can plug and play different form-finding results, assess and optimize their fabrication schemes, or leverage knowledge in fabrication design, model toolpath curves as sections, reconstruct surfaces, and merge them into form-finding and segmentation in an inverse way. The proposed framework enables the integration of form-finding expertise with fabrication-oriented design, allowing the realization of spatial shell structures with complex topologies or extreme geometrical features through 3D concrete printing. 

Xanthine dehydrogenase (XDH) is a molybdenum cofactor (Moco) requiring enzyme that catabolizes hypoxanthine into xanthine and xanthine into uric acid, the final steps in purine catabolism. Human patients with mutations in XDH develop xanthinuria which can lead to xanthine stones in the kidney, recurrent urinary tract infections, and renal failure. Currently, there are no therapies for treating human XDH deficiency. Thus, understanding mechanisms that maintain purine homeostasis is an important goal of human health. Here, we used the nematodeCaenorhabditis elegansto model human XDH deficiency using two clinically relevant paradigms: Moco deficiency or loss-of-function mutations inxdh-1,theC. elegansortholog of XDH.Both Moco deficiency andxdh-1loss of function caused the formation of autofluorescent xanthine stones inC. elegans. Surprisingly, only 2% ofxdh-1null mutantC. elegansdeveloped a xanthine stone, suggesting additional pathways may regulate this process. To uncover such pathways, we performed a forward genetic screen for mutations that enhance the penetrance of xanthine stone formation inxdh-1null mutantC. elegans. We isolated multiple loss-of-function mutations in the genesulp-4which encodes a sulfate permease homologous to human SLC26 anion exchange proteins. We demonstrated that SULP-4 acts cell-nonautonomously in the excretory cell to limit xanthine stone accumulation. Interestingly,sulp-4mutant phenotypes were suppressed by mutations in genes that encode for cystathionase (cth-2)or cysteine dioxygenase (cdo-1), members of the sulfur amino acid catabolism pathway required for production of sulfate, a substrate of SULP-4. We propose that sulfate accumulation caused bysulp-4loss of function promotes xanthine stone accumulation. We speculate that sulfate accumulation causes osmotic imbalance, creating conditions in the intestinal lumen that favor xanthine stone accumulation. Supporting this model, a mutation inosm-8that constitutively activates the osmotic stress response also promoted xanthine stone accumulation in anxdh-1mutant background. Thus, our work establishes aC. elegansmodel for human XDH deficiency and identifies the sulfate permeasesulp-4as a critical player controlling xanthine stone accumulation. 

Real-time Hybrid Simulation (RTHS) is a technique wherein a structural system is divided into an analytical and an experimental substructure. The former is modeled numerically while the latter is physically present in the laboratory. The two substructures are kinematically linked together at their interface degrees of freedom (DOFs) and the equations of motion are solved in real-time to determine the structure’s response. One of the main challenges of RTHS is to include the effects of soil–foundation–structure interaction (SFSI), which can have a substantial effect on the overall response. The soil domain cannot be modeled experimentally due to the large payload size. On the other hand, modeling the soil domain numerically, using a continuum-based approach, in real-time is challenging due to the associated computational cost. To address these issues, this paper presents a framework for seismic RTHS of SFSI systems using a Neural Network (NN)-based macroelement model of the soil–foundation system. A coupled SFSI model is used to train the NN model and the loss function is based on dynamic equilibrium at the interface between the foundation and the structure. The framework is demonstrated using a three-story building with the lateral load resisting system comprised of moment resisting and damped brace frames. The proposed framework ensures a stable and accurate RTHS, accounting for SFSI by incorporating: (a) spring elements at the output DOFs of the NN model to remove rigid body modes; (b) dashpot elements at the output DOFs of the NN model to mitigate spurious higher frequencies of vibration; and (c) regularization in the NN model’s architecture with data augmentation to reduce overfitting. 

The Mississippi River Basin (MRB), the fourth-largest river basin in the world, is an important corridor for hy- droelectric power generation, agricultural and industrial production, riverine transportation, and ecosystem goods and services. Historically, flooding of the Mississippi River has resulted in significant economic losses. In a future with an intensified global hydrological cycle, the altered discharge of the river may jeopardize commu- nities and infrastructure situated in the floodplain. This study utilizes output from the Community Earth System Model version 2 (CESM2) large ensemble simulations spanning 1930 to 2100 to quantify changes in future MRB discharge under a high greenhouse gas emissions scenario (SSP3–7.0). The simulations show that increasing precipitation trends exceed and dominate increased evapotranspiration (ET), driving an overall increase in total discharge in the Ohio and Lower Mississippi River basins. On a seasonal scale, reduced spring snowmelt is projected in the Ohio and Missouri River basins, leading to reduced spring runoff in those regions. However, decreased snowmelt and spring runoff is overshadowed by a larger increase in projected precipitation minus ET over the entire basin and leads to an increase in mean river discharge. This increase in discharge is linked to a relatively small increase in the magnitude of extreme floods (2 % and 3 % for 100-year and 1000-year floods, respectively) by the late 21st century relative to the late 20th century. Our analyses imply that under SSP3–7.0 forcing, the Mississippi River and Tributaries (MR&T) project design flood would not be exceeded at the 100-year return period. Our results harbor implications for water resources management including increased vulnerability of the Mississippi River given projected changes in climate. 

The Pelona–Orocopia–Rand (POR) schists were emplaced during the Farallon flat subduction in the early Cenozoic and now occupy the root of major strike-slip faults of the San Andreas Fault system. The POR schists are considered frictionally stable at lower temperatures than other basement rocks, limiting the maximum depth of seismicity in Southern California. However, experimental constraints on the composition and frictional properties of POR schists are still missing. Here, we study the frictional behavior of synthetic gouge derived from Pelona, Portal, and Rand Mountain schist wall rocks under hydrothermal, triaxial conditions. We conduct velocity-step experiments from 0.04 to 1 μm/s from room temperature to 500ºC under 200 MPa effective normal stress, including a 30 MPa porefluid pressure. The frictional stability of POR schists in the lower crust is caused by a thermally activated transition from slip-rate- and state-dependent friction to inherently stable, rate-dependent creep between 300ºC and 500ºC, depending on sample composition and slip-rate. The mineralogy of POR schists shows much variability caused by different protoliths and metamorphic grades, featuring various amounts of phyllosilicates, quartz, feldspar, and amphibole. Pelona and Portal schists exhibit a velocity-weakening regime enabling the nucleation and propagation of earthquakes when exhumed in the middle crust, as in the Mojave section of the San Andreas Fault. The contrasted frictional properties of POR schists exemplify the lithological control of seismic processes and associated hazards. 

ABSTRACT Photoautotrophic diazotrophs, specifically the generaTrichodesmiumand UCYN-A, play a pivotal role in marine nitrogen cycling through their capacity for nitrogen fixation. Despite their global distribution, the microdiversity and environmental drivers of these diazotrophs remain underexplored. This study provides a comprehensive analysis of the global diversity and distribution ofTrichodesmiumand UCYN-A using the nitrogenase gene (nifH) as a genetic marker. We sequenced 954 samples from the Pacific, Atlantic, and Indian Oceans as part of the Bio-GO-SHIP project. Our results reveal significant phylogenetic and biogeographic differences between and within the two genera.Trichodesmiumexhibited greater microdiversity compared to UCYN-A, with clades showing region-specific distribution.Trichodesmiumclades were primarily influenced by temperature and nutrient availability. They were particularly frequent in regions of phosphorus stress. In contrast, UCYN-A was most frequently observed in regions experiencing iron stress. UCYN-A clades demonstrated more homogeneous distributions, with a single sequence variant within the UCYN-A1 clade dominating across varied environments. The biogeographic patterns and environmental correlations ofTrichodesmiumand UCYN-A highlight the role of microdiversity in their ecological adaptation and reflect their different ecological strategies. These findings underscore the importance of characterizing the global patterns of fine-scale genetic diversity to better understand the functional roles and distribution of marine nitrogen-fixing photoautotrophs.IMPORTANCEThis study provides insights into the global diversity and distribution of nitrogen-fixing photoautotrophs, specificallyTrichodesmiumand UCYN-A. We sequenced 954 oceanic samples of thenifHnitrogenase gene and uncovered significant differences in microdiversity and environmental associations between these genera.Trichodesmiumshowed high levels of sequence diversity and region-specific clades influenced by temperature and nutrient availability. In contrast, UCYN-A exhibited a more uniform distribution, thriving in iron-stressed regions. Quantifying these fine-scale genetic variations enhances our knowledge of their ecological roles and adaptations, emphasizing the need to characterize the genetic diversity of marine nitrogen-fixing prokaryotes. 

This paper examines the integration of justice-centered making into STEM teacher preparation programs, focusing on how these programs can foster equity and inclusivity while acknowledging the need for more research on the overlapping areas of STEM teacher preparation, social justice, and makerspace. Therefore, I synthesize recent literature in the overlapping areas and identify how each component brings insight to purposeful activity, identity formation, and connection. The discussion leads to how utilizing justice-centered-making activities can prepare educators to address systemic inequities in STEM fields. The implications of these pedagogical approaches for both teachers and students are discussed. 

Abstract DNA double-strand breaks (DSBs) are formed in meiosis, so their repair in the homologous recombination (HR) pathway will lead to crossover formation, which is essential for successful chromosome segregation. HR contains 2 subpathways: synthesis-dependent strand annealing (SDSA) that creates noncrossover and double Holliday junction (dHJ) that generates crossovers. RAD-51 is a protein essential to the formation of all products of HR, as it assembles on the processed DSB, allowing the invasion of the single-stranded DNA into a region of homology. RAD-51 is removed by RAD-54.L after invasion to allow for repair to occur. Here, we investigate a separation of function allele of rad-51, rad-51::FLAG, as compared to 2 other RAD-51 alleles: rad-51::degron and GFP::rad-51. rad-51::FLAG displays slowed repair kinetics, resulting in an accumulation of RAD-51 foci. rad-51::FLAG worms also activate the DSB checkpoint, but to a less extant than that of rad-51 null mutants. In a proximity ligation assay, RAD-54.L and RAD-51 show enriched colocalization in rad-51::FLAG germlines (but not in rad-51::degron), consistent with stalling at the strand invasion step in HR. The defects in RAD-51 disassembly in rad-51::FLAG mutants lead to formation of chromosomal fragments, similar in their magnitude to ones observed in rad-51 or rad-54.L null mutants. However, rad-51::FLAG mutants (unlike a rad-51 null, GFP::rad-51 or rad-54.L null mutants) displayed no defects in the formation of crossover-designated sites (via GFP::COSA-1 localization). Given that rad-51::FLAG worms show checkpoint activation and chromosomal fragments, these results suggest that crossover repair concludes normally, while the noncrossover pathway is perturbed. This is strikingly different from rad-51::degron and GFP::rad-51 strains, which are proficient or deficient in both pathways, respectively. These results suggest that noncrossovers vs crossovers have distinct recombination intermediates and diverge prior to RAD-51 disassembly. 

Fell’s absorption principle states that the left regular representation of a group absorbs any unitary representation of the group when tensored with it. In a weakened form, this result carries over to the left regular representation of a right LCM submonoid of a group and its Nica-covariant isometric representations but it fails if the semigroup does not satisfy independence. In this paper, we explain how to extend Fell’s absorption principle to an arbitrary submonoidPof a groupGby using an enhanced version of the left regular representation. Li’s semigroup\mathrm{C}^{*}-algebra\mathrm{C}^{*}_{s}(P)and its representations appear naturally in our context. Using the enhanced left regular representation, we not only provide a very concrete presentation for the reduced object for\mathrm{C}^{*}_{s}(P)but we also resolve open problems and obtain very transparent proofs of earlier results. In particular, we address the non-selfadjoint theory and we show that the non-selfadjoint object attached to the enhanced left regular representation coincides with that of the left regular representation. We obtain a non-selfadjoint version of Fell’s absorption principle involving the tensor algebra of a semigroup and we use it to improve recent results of Clouâtre and Dor-On on the residual finite dimensionality of certain\mathrm{C}^{*}-algebras associated with such tensor algebras. As another application, we give yet another proof for the existence of a\mathrm{C}^{*}-algebra which is co-universal for equivariant, Li-covariant representations of a submonoidPof a groupG.