University of America

The X-IFU instrument for ESA's upcoming flagship mission Athena will use Mo/Au bilayer transition-edge sensors (TES) with Au/Bi X-ray absorbers to form a kilo-pixel microcalorimeter array. Such detectors require careful calibration to maintain their best possible performance, but such calibrations can change over long periods of time when exposed to certain environmental conditions. We have previously reported the effects of humidity and elevated temperature on prototype array characteristics. In that study, storage of a prototype array at 60 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula>C for 10 days under vacuum produced an unexpected shift in the TES critical temperature T <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{c}$</tex-math></inline-formula> (+13 to +19%) and normal resistance R<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{n}$</tex-math></inline-formula> (+4%). In this work, we continue investigating shifts in array characteristics after long-duration temperature exposures so that safe storage and handling conditions for X-IFU flight arrays can be set. A prototype array exposed to 35 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> C under vacuum for 26 days gradually increased in TES normal resistance. The energy scale of a second prototype array was measured before aging and then recovered to within 0.5 eV following a similar aging induced R<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{n}$</tex-math></inline-formula> increase. Aging of the TES was studied directly by applying the same thermal conditions exclusively to Mo/Au bilayers on Si substrate. These measurements allow a better understanding of the cause of the observed shift by decoupling the TES bilayer from the remaining device structures such as the SiNx membrane and the absorber. Four-point resistance measurements were used to readout the bilayer samples at 4.2 K. Bilayers aged in a vacuum generally saw no change or a slight increase in resistance, while bilayers aged in nitrogen gas decreased in resistance. Finally, we conclude with a comparative overview of all test results on prototype arrays and TES bilayers, elaborate on possible mechanisms for the observed shifts in characteristics, and make recommendations for maintaining the long-term stability of our devices.

Abstract Recent three-dimensional flare models suggest that flare ribbon substructure is linked to the fragmentation of the reconnecting current sheet in the corona. Flare ribbon substructure can therefore potentially serve as a unique diagnostic tool for physical processes in the flare current sheet. In this paper, we describe a new method to quantify the evolution of ribbon substructure that first extracts the ribbon’s bright leading edge and then quantifies its morphology using the box-counting dimension and correlation dimension mapping (CDM). We first test our method using synthetic observations. We then apply it to an M6.5-class solar flare on 2015 June 22 observed by the Interface Region Imaging Spectrograph (IRIS) 1330 Å slit-jaw imager. We find that when the flare ribbon boundary has more multiple-spatial-scale features (a higher box-counting dimension), hard X-ray emission and magnetic reconnection rates are the strongest. We also find that the flare ribbon complexity characterized by CDM has a moderate correlation with the IRIS Si IV 1402.77 Å nonthermal velocity (in the negative polarity ribbon) and reconnection flux rates (in ribbons of both magnetic polarities). We conclude that the buildup of the spatial complexity of the ribbons at multiple spatial scales can serve as an observational proxy for current-sheet fragmentation in the corona.

Carbon nanotube yarns (CNTYs) have received more consideration recently due to their excellent specific mechanical, electrical and thermal properties, making them promising materials for different applications. Until now, the axial properties of the yarn have been thoroughly investigated; however, the transverse or radial properties, orthogonal to the fiber axis, remain relatively unknown due to the challenges associated with their measurement. In this study, the transverse or radial response of the CNTY including its elastic modulus was determined using Atomic Force Microscopy (AFM) and Raman Spectroscopy. Determining transverse properties in fibrous materials presents challenges owing to their geometry, inherent anisotropy, whereby mechanical characteristics exhibit directional disparities; i.e., the properties in the transverse direction may be several orders of magnitude smaller than those in the axial direction. To overcome these difficulties, AFM was utilized to perform nanoindentation experiments, where a tipless flexible cantilever probe was used to apply a controlled force to the CNTY surface. The resulting indentation depth was then analyzed to determine the transversal elastic modulus. Preliminary findings indicate that the transverse elastic modulus of the CNTYs ranges from 10–54 kPa for strain levels below 3%. Complementary Raman spectroscopy provided insight into the bulk-scale mechanical behavior of CNTYs. Incremental compressive loading between microscope slides induced nonlinear upshifts in the 2D Raman band (from ~2686.6 to 2691.4 cm−1), indicating nanoscale tube realignment, inter-tube densification, and compaction. From lateral diameter measurements under load, a stress–strain curve was constructed, revealing three distinct regimes: one with an initial elastic modulus of 3.12 MPa (0.3–11.2% strain), another one with an elastic modulus increasing to 8.46 MPa (11.2–14.4%), and finally one with an elastic modulus peaking at 16.86 MPa beyond 14.4% strain. Together, these methods delineate the hierarchical and anisotropic nature of CNTYs, validating the importance of multiscale mechanical characterization for their deployment in piezoresistive sensors and multifunctional composites. This study establishes a robust framework for quantifying the transverse mechanical response of CNTYs.

Omega bands are mesoscale auroral structures that appear as eastward-moving poleward protrusions in the auroral oval. They typically appear in the post-midnight sector during periods of enhanced geomagnetic activity. Omega bands have been associated with Ps6 pulsations and rapidly time-varying magnetic fields on the ground, making them highly relevant to space weather forecasting. However, while the solar wind and magnetospheric drivers of omega bands have been previously studied, the characteristic signatures of omega band substorm events have not been identified.In this work, we compare solar wind, magnetospheric, and geomagnetic parameters measured during general substorm activity to the same parameters measured during 205 omega band events from 1997 to 2007 identified using the MIRACLE network. Non-omega substorm events are identified using spline fitting techniques to locate positive bays in the SuperMAG lower auroral electrojet index, and filtered to match the omega band substorm events in intensity. We use OMNI data to determine the solar wind drivers of these events and data from GOES and SuperMAG to identify magnetospheric and geomagnetic signatures of these events. This analysis will allow us to identify the unique solar wind drivers and magnetospheric configurations associated with omega band formation and improve our understanding of magnetosphere-ionosphere coupling dynamics during periods of enhanced geomagnetic activity.

Abstract We report the detection of methanol (CH 3 OH) toward interstellar comet 3I/ATLAS using the Atacama Compact Array of the Atacama Large Millimeter/submillimeter Array (ALMA) on UT 2025 August 28, September 18 and 22, and October 1 and of hydrogen cyanide (HCN) on September 12 and 15. These observations spanned pre-perihelion heliocentric distances ( r H ) of 2.6–1.7 au. The molecules showed outgassing patterns distinct from one another, with HCN production being depleted in the sunward hemisphere of the coma, whereas CH 3 OH was enhanced in that direction. Statistical analysis of molecular scale lengths in 3I/ATLAS indicated that CH 3 OH included production from coma sources at L p &gt; 258 km at 99% confidence. However, low signal-to-noise ratio (S/N) on long baselines, which sample emission on small spatial scales closest to the nucleus, prevented definitively ruling out CH 3 OH as purely a parent species. In contrast, HCN production was indistinguishable from direct nucleus sublimation. The CH 3 OH production rate increased sharply from August through October, including an uptick near the inner edge of the H 2 O sublimation zone at r H = 2 au. Compared to comets measured to date at radio wavelengths, the derived CH 3 OH/HCN ratios in 3I/ATLAS of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>12</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>34</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>30</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>7</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>9</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>14</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>11</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> on September 12 and 15, respectively, are among the most enriched values measured in any comet, surpassed only by anomalous solar system comet C/2016 R2 (Pan-STARRS).

Abstract We present results from coordinated multiwavelength observations of the microquasar SS 433, obtained with XRISM, optical telescopes (Seimei, LCO, Tomo-e Gozen, MITSuME), and the kSIRIUS near-infrared camera during 2024 April and 2025 March. The XRISM exposures amounted to ${\sim}200$ ks in 2024 and ~100 ks in 2025, corresponding to different combinations of orbital and precessional phases. With XRISM/Resolve’s high spectral resolution and large effective area, we clearly resolved numerous emission lines even in short time segments, achieving improved accuracy in Doppler-shift measurements relative to earlier observations. The simultaneously obtained X-ray and optical Doppler shifts suggest a possible tendency for the optical emission to lag slightly behind the X-rays. In the Resolve data, the Doppler shifts of the two jet components exhibited apparent asymmetries, with jet speeds fluctuating around ${\sim}0.26 \pm 0.01c$ in 2024 and ${\sim}0.30 \pm 0.01c$ in 2025. The velocity variations indicated modulations on a timescale of ~6.3 d, with a phase offset of about $-90^{\circ }$ relative to the nutation cycle. The observed line widths and flux of the approaching and receding jets appear consistent with the expected geometrical effects, indicating systematically larger line widths in the inner regions of the jets, as proposed by Shidatsu et al. (2025, PASJ, 77, 1313). Optical light curves show flares of ~400 s in 2024 and ~1600 s in 2025, with amplitudes up to ~15% during out-of-eclipse intervals, while the XRISM/Xtend light curves show no significant variability within the overlapping intervals and given the statistical uncertainties. Near-infrared photometry in 2024, obtained during an out-of-eclipse interval at a different epoch from the optical observations, showed no flare-like variability, and the X-ray band also remained constant within uncertainties. These coordinated observations provide a foundation for future XRISM studies aimed at probing the dynamical properties of the relativistic jets in SS 433.

The primary objective of this work is to provide recommendations for glasses to be used for Single Pass Flow Through (SPFT) testing in FY 2016. Since LAW glass formulation development is ongoing, particularly with respect to enhanced formulations with increased waste loading as compared to the present WTP baseline, it is anticipated that this report will be revised on an annual basis in order to provide appropriate recommendation for testing in each fiscal year.

This study analyses birth mothers’ primary motivations for placing their child for adoption, aiming to provide a more comprehensive understanding of the factors influencing these choices. The researchers examined open-ended survey question responses from 768 birth mothers who placed a child for private domestic adoption. Four key themes emerged: (1) lack of resources and support for parenting; (2) respondents’ desire for an ideal family environment for their child; (3) present life circumstances; and (4) beliefs and pressures related to adoption. Responses also highlighted the complexity and multifaceted nature of birth mothers’ placement decisions, with many offering several factors that contributed to their decision-making. These results can inform future research, impact service delivery and improve public discourse regarding motivations for placement.

Histone modifications play essential roles in regulating chromatin accessibility and downstream transcription, serving as critical determinants of cell identity and function. However, the diversity of histone post-translational modifications (PTMs) and their tendency to be studied in isolation limits our understanding of their coordinated roles in shaping cellular states. Conventional flow cytometry methods for histone PTM assessment suffer from low multiplexing capacity and typically require nuclear isolation, resulting in significant sample loss and an incomplete picture of the overall cell state. Here, we present EpiFlow, a spectral flow cytometry protocol designed for multiparametric analysis of histone PTMs within whole cells. By utilizing a 96-well plate format and preserving the cell entirely, EpiFlow improves throughput and efficiency while retaining sample integrity. This method resolves subtle variations in histone PTMs within neural progenitor cells, capturing distinct chromatin states across the cell cycle and correlating them with several markers. Furthermore, we provide an open-access GitHub repository containing detailed protocols and analysis workflows, ensuring reproducibility and accessibility of this approach. EpiFlow offers a robust framework for exploring chromatin dynamics, with broad implications for advancing fundamental research and therapeutic research.