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Clathrate hydrates (CHs) are believed to exist within interstellar environments, potentially contributing to the preservation of diverse volatile compounds within icy bodies across the cosmos. In this study, using reflection absorption infrared spectroscopy, we show the formation of dimethyl ether (DME) CH from a vapor-deposited DME–water amorphous ice mixture. Experiments were conducted in an environment mimicking interstellar conditions: ultrahigh vacuum (P∼ 5 × 10–10mbar) and cryogenic conditions (T∼ 10–150 K). Thermal annealing of the amorphous ice mixture to a higher temperature (T∼ 125 K) resulted in the formation of CH. Quantum chemical calculations suggested the formation of 51264cages of structure II CH. Subsequent investigations into the dissociation of DME CH unveiled its transformation into hexagonal ice, requiring a substantial activation energy of 68.04 kJ mol–1. Additionally, confirmation of the formation and dissociation of CH was supported by temperature-programmed desorption mass spectrometry. These results significantly advance our understanding of the existence of CHs under extreme conditions relevant to an interstellar medium.

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 existence of many molecules in the form of clathrate hydrates (CHs) in ultrahigh vacuum (UHV) and cryogenic conditions has not been explored adequately. In the present study, a detailed investigation by reflection absorption infrared spectroscopy confirmed that the three phases of ethane, i.e., amorphous, crystalline, and CH, coexist in a vapor-deposited ethane–water mixture at 60 K in UHV. Experiments were conducted with vapor-deposited ice films at 10 K, which were annealed to 60 K for tens of hours, and the IR spectral evolution was monitored systematically. Upon maintaining the system at 60 K, three phases of ethane were seen to coexist, but a gradual increase in the hydrate phase was noticed. The evolution of ethane CH from the amorphous ethane–water ice mixture was observed for the very first time in UHV under cryogenic conditions. The formation of the CH was further confirmed by temperature-programmed desorption (TPD) mass spectrometry. Quantum chemical calculation suggested the formation of 51262cage of structure I CH in the ice matrix. The formation of ethane CH in a thin ice film at such a low temperature under UHV suggests its existence in the cometary environment.

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.

Photochemistry can generate chemical complexity in an interstellar space. This may occur due to photolysis and associated events that can happen in condensed molecular solids under the prevailing temperature and pressure conditions. In the present study, using reflection absorption infrared spectroscopy (RAIRS), three different condensed phases of methyl chloride ice, namely, amorphous, crystalline, and polycrystalline, were detected in ultrahigh vacuum (UHV) (p = 5 × 10–10mbar) and cryogenic conditions (T = 10–90 K). Upon vacuum ultraviolet (VUV) photoirradiation, crystalline methyl chloride formed more photoproducts than amorphous and polycrystalline forms. This unusual finding is attributed to the rapid diffusion and reaction of photochemical intermediates in a crystalline matrix, whereas the intermediates are trapped at grain boundaries in the polycrystalline solid. Normally, the intermediate diffusion is high in the case of the amorphous phase as compared with the crystalline phase. During long-term irradiation, discontinuity in the polycrystalline phase is removed, resulting in enhancement in the formation of photoproducts in the matrix, which was observed by the intensified desorption of photoproducts in temperature-programmed desorption mass spectrometry (TPD-MS). Further, all major and minor neutral photoproducts were detected by highly surface-sensitive Cs+ion-based secondary ion mass spectrometry (SIMS).