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1. The impact of trait number and correlation on functional diversity metrics in real-world ecosystems

   https://doi.org/10.1371/journal.pone.0306342  

   Ohlert, Timothy; Kimmel, Kaitlin; Avolio, Meghan; Chang, Cynthia; Forrestel, Elisabeth; Gerstner, Benjamin P; Hobbie, Sarah E; Reich, Peter; Whitney, Kenneth D; Komatsu, Kimberly (September 2024, PLOS ONE)

   Boscutti, Francesco (Ed.)

   The use of trait-based approaches to understand ecological communities has increased in the past two decades because of their promise to preserve more information about community structure than taxonomic methods and their potential to connect community responses to subsequent effects of ecosystem functioning. Though trait-based approaches are a powerful tool for describing ecological communities, many important properties of commonly-used trait metrics remain unexamined. Previous work with simulated communities and trait distributions shows sensitivity of functional diversity measures to the number and correlation of traits used to calculate them, but these relationships have yet to be studied in actual plant communities with a realistic distribution of trait values, ecologically meaningful covariation of traits, and a realistic number of traits available for analysis. To address this gap, we used data from six grassland plant communities in Minnesota and New Mexico, USA to test how the number of traits and the correlation between traits used in the calculation of eight functional diversity indices impact the magnitude of functional diversity metrics in real plant communities. We found that most metrics were sensitive to the number of traits used to calculate them, but functional dispersion (FDis), kernel density estimation dispersion (KDE dispersion), and Rao’s quadratic entropy (Rao’s Q) maintained consistent rankings of communities across the range of trait numbers. Despite sensitivity of metrics to trait correlation, there was no consistent pattern between communities as to how metrics were affected by the correlation of traits used to calculate them. We recommend that future use of evenness metrics include sensitivity analyses to ensure results are robust to the number of traits used to calculate them. In addition, we recommend use of FDis, KDE dispersion, and Rao’s Q when ecologically applicable due to their ability to produce consistent rankings among communities across a range of the numbers of traits used to calculate them. 

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2. Vulnerability assessment of Structural Insulated Panels with metal skins subjected to windborne debris impact

   https://doi.org/https://doi.org/10.1016/j.compositesb.2020.108163  

   Saini, D.; Shafei, B. (June 2020, Composites)

   Structural Insulated Panels (SIPs), which consist of a composite of an insulating polymer foam sandwiched between two layers of structural skins, are widely used in residential and commercial buildings. Such panels, in the regions prone to hurricanes and tornadoes, are often exposed to the risk of windborne debris impact. Despite the consequences associated with damage to SIPs, the studies on their perforation resistance and design variables have been rather limited. To address this gap, the current study develops a computational framework to assess the vulnerability of the SIPs of various configurations subjected to a range of windborne debris impact scenarios. For this purpose, impact simulations are conducted to quantify the response and evaluate the extent of damage to the SIPs. The study is further extended to evaluate the effect of various structural details and material properties on the perforation resistance of the SIPs. Based on the simulation results, a set of vulnerability curves are developed for the first time to capture the risk of failure of the SIPs under the windborne debris hazard. This is expected to improve the design of this important category of wall panels, especially to ensure their safety and performance during severe windstorms. 

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3. Sensory signals of unloading in insects are tuned to distinguish leg slipping from load variations in gait: experimental and modeling studies

   https://doi.org/10.1152/jn.00285.2022  

   Harris, Christian M.; Szczecinski, Nicholas S.; Büschges, Ansgar; Zill, Sasha N. (October 2022, Journal of Neurophysiology)

   In control of walking, sensory signals of decreasing forces are used to regulate leg lifting in initiation of swing and to detect loss of substrate grip (leg slipping). We used extracellular recordings in two insect species to characterize and model responses to force decrements of tibial campaniform sensilla, receptors that detect forces as cuticular strains. Discharges to decreasing forces did not occur upon direct stimulation of the sites of mechanotransduction (cuticular caps) but were readily elicited by bending forces applied to the leg. Responses to bending force decreases were phasic but had rate sensitivities similar to discharges elicited by force increases in the opposite direction. Application of stimuli of equivalent amplitude at different offset levels showed that discharges were strongly dependent upon the tonic level of loading: firing was maximal to complete unloading of the leg but substantially decreased or eliminated by sustained loads. The contribution of cuticle properties to sensory responses was also evaluated: discharges to force increases showed decreased adaptation when mechanical stress relaxation was minimized; firing to force decreases could be related to viscoelastic “creep” in the cuticle. Discharges to force decrements apparently occur due to cuticle viscoelasticity that generates transient strains similar to bending in the opposite direction. Tuning of sensory responses through cuticular and membrane properties effectively distinguishes loss of substrate grip/complete unloading from force variations due to gait in walking. We have successfully reproduced these properties in a mathematical model of the receptors. Sensors with similar tuning could fulfil these functions in legs of walking machines. NEW & NOTEWORTHY Decreases in loading of legs are important in the regulation of posture and walking in both vertebrates and invertebrates. Recordings of activities of tibial campaniform sensilla, which encode forces in insects, showed that their responses are specifically tuned to detect force decreases at the end of the stance phase of walking or when a leg slips. These results have been reproduced in a mathematical model of the receptors and also have potential applications in robotics. 

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4. Use of CRISPRoff and synthetic Notch to modulate and relay endogenous gene expression programs in engineered cells

   https://doi.org/10.3389/fbioe.2024.1346810  

   Shi, Shuqun; Hamann, Catherine A; Lee, Joanne C; Brunger, Jonathan M (June 2024, Frontiers in Bioengineering and Biotechnology)

   Uncovering the stimulus-response histories that give rise to cell fates and behaviors is an area of great interest in developmental biology, tissue engineering, and regenerative medicine. A comprehensive accounting of cell experiences that lead to the development of organs and tissues can help us to understand developmental anomalies that may underly disease. Perhaps more provocatively, such a record can also reveal clues as to how to drive cell collective decision-making processes, which may yield predictable cell-based therapies or facilitate production of tissue substitutes for transplantation orin vitroscreening of prospective therapies to mitigate disease. Toward this end, various methods have been applied to molecularly trace developmental trajectories and record interaction histories of cells. Typical methods involve artificial gene circuits based on recombinases that activate a suite of fluorescent reporters or CRISPR-Cas9 genome writing technologies whose nucleic acid-based record keeping serves to chronicle cell-cell interactions or past exposure to stimuli of interests. Exciting expansions of the synthetic biology toolkit with artificial receptors that permit establishment of defined input-to-output linkages of cell decision-making processes opens the door to not only record cell-cell interactions, but to also potentiate directed manipulation of the outcomes of such interactions via regulation of carefully selected transgenes. Here, we combine CRISPR-based strategies to genetically and epigenetically manipulate cells to express components of the synthetic Notch receptor platform, a widely used artificial cell signaling module. Our approach gives rise to the ability to conditionally record interactions between human cells, where the record of engagement depends on expression of a state-specific marker of a subset of cells in a population. Further, such signal-competent interactions can be used to direct differentiation of human embryonic stem cells toward pre-selected fates based on assigned synNotch outputs. We also implemented CRISPR-based manipulation of native gene expression profiles to bias outcomes of cell engagement histories in a targeted manner. Thus, we present a useful strategy that gives rise to both state-specific recording of cell-cell interactions as well as methods to intentionally influence products of such cell-cell exchanges. 

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5. Comparison of Various Theoretical Measures of Aromaticity within Monosubstituted Benzene

   https://doi.org/10.3390/molecules29102260  

   Swain, Caleb K; Scheiner, Steve (May 2024, Molecules)

   The effects of monosubstitution on the aromaticity of benzene are assessed using a number of different quantitative schemes. The ability of the mobile π-electrons to respond to an external magnetic field is evaluated using several variants of the NICS scheme which calculate the shielding of points along the axis perpendicular to the molecule. Another class of measures is related to the drive toward the uniformity of C-C bond lengths and strengths. Several energetic quantities are devised to approximate an aromatic stabilization energy and the tendency of the molecule to maintain planarity. There is a lack of consistency in that the various measures of aromaticity lead to differing conclusions as to the effects of substituents on the aromaticity of the ring. 

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