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Thermal diffusion and recombination control the kinetics of photochemical reactions of reactive radicals formed by ultraviolet photon irradiation in interstellar ices. Here, we show that upon vacuum ultraviolet photolysis, N2O ice produces O3and several oxides of nitrogen, such as NO, NO2, N2O2, N2O3, N2O4, and N2O5in interstellar ice mimics. Photoproducts within the bulk and on the surface were analyzed using reflection absorption infrared spectroscopy and Cs+ion-based secondary ion mass spectrometry, while desorbed species were studied using temperature-programmed desorption mass spectrometry. Notably, thermal annealing of the photoirradiated ice to 90 K resulted in a significant increase in NO and N2O3. Photoirradiation at 10 K revealed the dominance of three atom photoproducts, such as NO2and O3. In contrast, irradiation at 50 K significantly enhanced the production of four or higher atom photoproducts (N2O2, N2O3, N2O4, and N2O5). This behavior is attributed to the restricted diffusion of reactive radicals and unstable oxygen species (O and O3) at 10 K, which confines radical–radical reactions to three or fewer atom photoproducts, whereas higher temperatures facilitate oxygen and other radical diffusion and recombination, yielding heavier photoproducts. These results throw light on the thermal diffusion effects on the kinetics of photoproducts in interstellar ice mimics.

The endoplasmic reticulum (ER) is a single-copy organelle that cannot be generated de novo, suggesting coordination between the mechanisms overseeing ER integrity and those controlling the cell cycle to maintain organelle inheritance. The Unfolded Protein Response (UPR) is a conserved signaling network that regulates ER homeostasis. Here, we show that pharmacological and genetic inhibition of the UPR sensors IRE1, ATF6, and PERK in unstressed cells delays the cell cycle, with PERK inhibition showing the most penetrant effect, which was associated with a slowdown of the G1-to-S/G2transition. Treatment with the small molecule ISRIB to bypass the effects of PERK-dependent phosphorylation of the translation initiation factor eIF2α had no such effect, suggesting that cell cycle timing depends on PERK’s kinase activity but is independent of eIF2α phosphorylation. Using complementary light and electron microscopy and flow cytometry-based analyses, we also demonstrate that the ER enlarges before mitosis. Together, our results suggest coordination between UPR signaling and the cell cycle to maintain ER physiology during cell division.

Ti-based alloys have been commonly employed in manufacturing implants for orthopedic applications. Binary Titanium-Niobium (Ti-25Nb) alloy is a promising material for potential applications in orthopedics because of their lower elastic moduli and superior biocompatibility than the conventional Ti-based alloys. Implants with porous structures encourage bone ingrowth and reduce the effect of stress-shielding further. This study is aimed at establishing the relationship between the mechanical performance and structural parameters of porous body-centered-cubic (BCC) structures made up of Ti-25Nb (25% by wt.). Solid models of BCC porous structures were constructed (unit cell size: 2 mm; overall size: 8 × 8 × 8 mm3). Finite element analysis (FEA) of the BCC structures with porosity ranging from 29% to 79% (seven porosities) was conducted under tension, bending, and torsional loads. The Gibson-Ashby model and Exponential regression model were also employed to determine the stiffness of the above porous structures. The functional relationships between effective Young’s modulus, effective yield strength, and porosity generated from both the models were found to match the FEA results well. Results indicated that porosity in the range of 50%−70% can be used to design graded porous stems to mimic the mechanical properties of cortical bone.