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1. Allometric scaling and growth: Evaluation and applications in subadult body mass estimation

   https://doi.org/10.1002/ajpa.24329  

   Yim, An‐Di; Konigsberg, Lyle W.; Hwa, Hsiao‐Lin; Chang, Chin‐Chen; Chen, Jo‐Yu; Liu, Hon‐Man (May 2021, American Journal of Physical Anthropology)

   Abstract ObjectivesPreviously developed methods in subadult body mass estimation have not been tested in populations other than European–American or African–American. This study uses a contemporary Taiwanese sample to test these methods. Through evaluating their accuracy and bias, we addressed whether the allometric relationships between body mass and skeletal traits commonly used in subadult body mass estimation are conserved among different populations. Materials and MethodsComputed tomography scans of lower limbs from individuals aged 0–17 years old of both sexes were collected from National Taiwan University Hospital along with documented body weight. Polar second moment of area, distal femoral metaphyseal breadth, and maximum superior/inferior femoral head diameter were collected either directly from the scans or from reconstructed 3D models. Estimated body mass was compared with documented body mass to assess the performance of the equations. ResultsCurrent methods provided good body mass estimates in Taiwanese individuals, with accuracy and bias similar to those reported in other validation studies. A tendency for increasing error with increasing age was observed for all methods. Reduced major axis regression showed the allometric relationships between different skeletal traits and body mass across different age categories can all be summarized using a common fitted line. A revised, maximum likelihood‐based approach was proposed for all skeletal traits. DiscussionThe results suggested that the allometric relationships between body mass and different skeletal traits are largely conserved among populations. The revised method provided improved applicability with strong underlying theoretical justifications, and potential for future improvements. 

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2. A Neptune-mass exoplanet in close orbit around a very low-mass star challenges formation models

   https://doi.org/10.1126/science.abo0233  

   Stefánsson, Guðmundur; Mahadevan, Suvrath; Miguel, Yamila; Robertson, Paul; Delamer, Megan; Kanodia, Shubham; Cañas, Caleb I.; Winn, Joshua N.; Ninan, Joe P.; Terrien, Ryan C.; et al (December 2023, Science)

   Theories of planet formation predict that low-mass stars should rarely host exoplanets with masses exceeding that of Neptune. We used radial velocity observations to detect a Neptune-mass exoplanet orbiting LHS 3154, a star that is nine times less massive than the Sun. The exoplanet’s orbital period is 3.7 days, and its minimum mass is 13.2 Earth masses. We used simulations to show that the high planet-to-star mass ratio (>3.5 × 10⁻⁴) is not an expected outcome of either the core accretion or gravitational instability theories of planet formation. In the core-accretion simulations, we show that close-in Neptune-mass planets are only formed if the dust mass of the protoplanetary disk is an order of magnitude greater than typically observed around very low-mass stars. 

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3. Selective breeding for high voluntary exercise in mice increases maximal ( V̇ O2,max) but not basal metabolic rate

   https://doi.org/10.1242/jeb.245256  

   Schwartz, Nicole E; McNamara, Monica P; Orozco, Jocelyn M; Rashid, Jaanam O; Thai, Angie P; Garland, Theodore (August 2023, Journal of Experimental Biology)

   ABSTRACT In general, sustained high rates of physical activity require a high maximal aerobic capacity (V̇O2,max), which may also necessitate a high basal aerobic metabolism (BMR), given that the two metabolic states are linked via shared organ systems, cellular properties and metabolic pathways. We tested the hypotheses that (a) selective breeding for high voluntary exercise in mice would elevate both V̇O2,max and BMR, and (b) these increases are accompanied by increases in the size of some internal organs (ventricle, triceps surae muscle, liver, kidney, spleen, lung, brain). We measured 72 females from generations 88 and 96 of an ongoing artificial selection experiment comprising four replicate High Runner (HR) lines bred for voluntary daily wheel-running distance and four non-selected control lines. With body mass as a covariate, HR lines as a group had significantly higher V̇O2,max (+13.6%, P<0.0001), consistent with previous studies, but BMR did not significantly differ between HR and control lines (+6.5%, P=0.181). Additionally, HR mice did not statistically differ from control mice for whole-body lean or fat mass, or for the mass of any organ collected (with body mass as a covariate). Finally, mass-independent V̇O2,max and BMR were uncorrelated (r=0.073, P=0.552) and the only statistically significant correlation with an organ mass was for V̇O2,max and ventricle mass (r=0.285, P=0.015). Overall, our results indicate that selection for a behavioral trait can yield large changes in behavior without proportional modifications to underlying morphological or physiological traits. 

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4. Progress in High-Precision Mass Measurements of Light Ions

   https://doi.org/10.3390/atoms12020008  

   Myers, Edmund G (February 2024, Atoms)

   Significant advances in Penning trap measurements of atomic masses and mass ratios of the proton, deuteron, triton, helion, and alpha-particle have occurred in the last five years. These include a measurement of the mass of the deuteron against 12C with 8.5 × 10−12 fractional uncertainty; resolution of vibrational levels of H2+ as mass and the application of a simultaneous measurement technique to the H2+/D+ cyclotron frequency ratio, yielding a deuteron/proton mass ratio at 5 × 10−12; new measurements of HD+/3He+, HD+/T+, and T+/3He+ leading to a tritium beta-decay Q-value with an uncertainty of 22 meV, and atomic masses of the helion and triton at 13 × 10−12; and a new measurement of the mass of the alpha-particle against 12C at 12 × 10−12. Some of these results are in strong disagreement with previous values in the literature. Their impact in determining a precise proton/electron mass ratio and electron atomic mass from spectroscopy of the HD+ molecular ion is also discussed. 

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5. No Peaks without Valleys: The Stable Mass Transfer Channel for Gravitational-wave Sources in Light of the Neutron Star–Black Hole Mass Gap

   https://doi.org/10.3847/1538-4357/ac9b0a  

   van_Son, L_A_C; de_Mink, S_E; Renzo, M.; Justham, S.; Zapartas, E.; Breivik, K.; Callister, T.; Farr, W_M; Conroy, C. (December 2022, The Astrophysical Journal)

   Abstract Gravitational-wave (GW) detections are starting to reveal features in the mass distribution of double compact objects. The lower end of the black hole (BH) mass distribution is especially interesting as few formation channels contribute here and because it is more robust against variations in the cosmic star formation than the high-mass end. In this work we explore the stable mass transfer channel for the formation of GW sources with a focus on the low-mass end of the mass distribution. We conduct an extensive exploration of the uncertain physical processes that impact this channel. We note that, for fiducial assumptions, this channel reproduces the peak at ∼9M_☉in the GW-observed binary BH mass distribution remarkably well and predicts a cutoff mass that coincides with the upper edge of the purported neutron star–black hole (NS–BH) mass gap. The peak and cutoff mass are a consequence of the unique properties of this channel; namely (1) the requirement of stability during the mass transfer phases, and (2) the complex way in which the final compact object masses scale with the initial mass. We provide an analytical expression for the cutoff in the primary component mass and show that this adequately matches our numerical results. Our results imply that selection effects resulting from the formation channel alone can provide an explanation for the purported NS–BH mass gap in GW detections. This provides an alternative to the commonly adopted view that the gap emerges during BH formation. 

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