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Surrogate selection is an experimental design that without sequencing any DNA can restrict a sample of cells to those carrying certain genomic mutations. In immunological disease studies, this design may provide a relatively easy approach to enrich a lymphocyte sample with cells relevant to the disease response because the emergence of neutral mutations associates with the proliferation history of clonal subpopulations. A statistical analysis of clonotype sizes provides a structured, quantitative perspective on this useful property of surrogate selection. Our model specification couples within-clonotype birth-death processes with an exchangeable model across clonotypes. Beyond enrichment questions about the surrogate selection design, our framework enables a study of sampling properties of elementary sample diversity statistics; it also points to new statistics that may usefully measure the burden of somatic genomic alterations associated with clonal expansion. We examine statistical properties of immunological samples governed by the coupled model specification, and we illustrate calculations in surrogate selection studies of melanoma and in single-cell genomic studies of T cell repertoires. 

Sudden onsets in the visual periphery elicit reflexive shifts of covert exogenous spatial attention. Here, we asked: are the behavioral effects of such an irrelevant exogenous cue modulated by implicit knowledge about the probability of the cue’s presence? Participants discriminated the orientation of a visual target that was preceded, on some trials, by an abrupt-onset task-irrelevant disk (exogenous cue). A color at fixation (red or green) signaled the probability that a cue would appear (0.8, “high- probability”, or 0.2, “low-probability”). When presented, this cue flashed briefly in the periphery, either near the target (valid cue) or non-target stimulus (invalid cue, equally likely). We used a speed- accuracy tradeoff (SAT) procedure to vary the time given for participants to process the stimuli before responding. We found that low-probability cues generated significantly larger cueing effects (discrimination accuracy, valid–invalid) than high-probability cues, but only when responses were made early in the accumulation of visual information (i.e., under strict time pressure). Both the directionality and temporal dynamics of these results were replicated across a series of online studies. Thus, expectations about an exogenous cue’s presence or absence have a significant yet transient impact on its ability to direct the reflexive allocation of covert exogenous spatial attention. 

Despite advances in digitizing vision and hearing, touch still lacks an equivalent digital interface matching the fidelity of human perception. This gap limits the quality of digital tactile information and the realism of virtual experiences. Here, we introduce a step toward human-resolution haptics: a class of wearable tactile displays designed to match the spatial and temporal acuity of the human fingertip. Our device, VoxeLite, is a 0.1-millimeter-thick, 0.19-gram, skin-conformal array of individually addressable soft electroadhesive actuators (“nodes”). As users touch and move across surfaces, VoxeLite delivers high-resolution distributed forces via the nodes. Enabled by scalable microfabrication techniques, the display achieves actuator densities up to 110 nodes per square centimeter, produces stimuli up to 800 hertz, and remains transparent to real-world tactile input. We demonstrate its ability to render small-scale hapticons and virtual textures and transmit physical surfaces, validated through human psychophysics and biomimetic sensing. These findings position VoxeLite as a platform for human-resolution haptics in immersive interfaces, robotics, and digital touch communication. 

Micro- or nano-diodes suspended in water can propel controllably under alternating-current fields or light without the need for fuels such as hydrogen peroxide or urea. This makes them promising candidates for miniature motors in biomedical and other applications. However, the mechanisms underlying their propulsion remain unclear. This study investigates the propulsion of diodes floating in an aqueous solution at the millimeter scale, which facilitates observation of motion, allowing direct correlation with electrical measurements of device properties. We find that the diode’s propulsion is driven by forward current under an alternating-current field and by photocurrent under illumination. The velocity of propulsion scales linearly with the net current, with the rectified or photogenerated current creating an imbalance of ions at the ends of the diodes. This, in turn, generates an electric field that induces electrophoretic flow around the diode and propels the diode. Additionally, we assess the velocity of diodes intentionally damaged by high reverse bias and find that it decreases significantly because of the reduced difference between forward and reverse currents. These results suggest potential uses of diode propulsion for characterizing and separating bottom-up-grown nano-/micro- diodes based on their reverse-saturation current, as well as nanomotors formed from multiple-junction nanowire diodes that can self-propel in water under light. 

Many taxa have independently evolved genetic sex determination where a single gene located on a sex chromosome controls gonadal differentiation. The gene anti-Mullerian hormone (amh) has convergently evolved as a sex determination gene in numerous vertebrate species, but how this gene has repeatedly evolved this novel function is not well understood. In the threespine stickleback (Gasterosteus aculeatus),amhwas duplicated onto the Y chromosome (amhy) ~22 million years ago. To determine whetheramhyis the primary sex determination gene, we used CRISPR/Cas9 and transgenesis to show thatamhyis necessary and sufficient for male sex determination, consistent with the function of a primary sex determination gene. We find thatamhycontributes to a higher total dosage ofamhearly in development and likely contributes to differential germ cell proliferation key to sex determination. The creation of sex-reversed lines also allowed us to investigate the genetic basis of secondary sex characteristics. Threespine stickleback have striking differences in behavior and morphology between sexes. Here we show one of the classic traits important for reproductive success, blue male nuptial coloration, is controlled by both sex-linked genetic factors as well as hormonal factors independent of sex chromosome genotype. This research establishes stickleback as a model to investigate howamhregulates gonadal development and how this gene repeatedly evolves novel function in sex determination. Analogous to the “Four Core Genotypes” model in house mice, sex-reversed threespine stickleback offer a new vertebrate model for investigating the separate contributions of gonadal sex and sex chromosomes to sexual dimorphism. 

Sex chromosomes often evolve unique patterns of gene expression during spermatogenesis. In many species, sex-linked genes are downregulated during meiosis in response to asynapsis of the heterogametic sex chromosome pair (meiotic sex chromosome inactivation; MSCI). This process has evolved convergently across many taxa with independently derived sex chromosomes. Our understanding how quickly MSCI can evolve and whether it is connected to the degree of sequence degeneration remains limited. Teleost fish are a noteworthy group to investigate MSCI because sex chromosomes have evolved repeatedly across species, often over short evolutionary timescales. Here, we investigate whether MSCI occurs in the threespine stickleback fish (Gasterosteus aculeatus), which have an X and Y chromosome that evolved less than 26 million years ago. Using single-cell RNA-seq, we found that the X and Y chromosomes do not have a signature of MSCI, maintaining gene expression across meiosis. Using immunofluorescence, we also show the threespine stickleback do not form a condensed sex body around the X and Y, a feature of MSCI in many species. We did not see patterns of gene content evolution documented in other species with MSCI. Y-linked ampliconic gene families were expressed across multiple stages of spermatogenesis, rather than being restricted to post-meiotic stages, like in mammals. Our work shows MSCI does not occur in the threespine stickleback fish and has not shaped the evolution of the Y chromosome. In addition, the absence of MSCI in the threespine stickleback suggests this process may not be a conserved feature of teleost fish, despite overall sequence degeneration and structural evolution of the Y chromosome, and argues for additional investigation in other species. We also observed testis-dependent differences in coding and expression evolution for X-linked genes, revealing evidence of testis specific faster-X effect and gene-by-gene dosage compensation. 

The search for new functional materials with tunable properties remains a central challenge in chemistry, particularly for applications in energy and electronics. In this work, we present a framework for predictive crystal design in alkali metal chalcogenides that enables controlled dimensional reduction of a parent covalent motif, yielding a broad range of electronic structures, which systematically evolve from one parent to the other. We present 11 new members of the AnCu4–nSnS4 family (A = alkali metal; n = 0–4), which reduce the three-dimensional (3D) covalent network of Cu4SnS4 into various 3D, 2D, 1D, and 0D [Cu4–nSnS4]n− motifs through the substitution of Cu with alkali metals of various radii. The end members of the family set the range in achievable band gaps at 0.99 eV for fully covalent Cu4SnS4 (n = 0) and 3.38 eV for K4SnS4 (n = 4) with 0D [SnS4]n− tetrahedra. As the dimensionality of [Cu4–nSnS4]n− systematically reduces within AnCu4–nSnS4 (n = 1–3), a stepwise increase in band gap energy occurs through a gradual decrease in the energy of the valence band maximum and an increase in the conduction band minimum, with an increase in the effective masses of charge carriers. Furthermore, irrespective of the alkali metal, the thermal stability decreases with decreasing [Cu4–nSnS4]n− dimensionality within the quaternary members. Most importantly, we demonstrate that predictable crystal structure and property evolution for a given composition space is possible by deriving a general formula based on substituting the covalent metals of a parent structure with alkali metals.