Response to Comment on “Maxima in the thermodynamic response and correlation functions of deeply supercooled water”

Caupin et al. have raised several issues regarding our recent paper on maxima in thermodynamic response and correlation functions in deeply supercooled water. We show that these issues can be addressed without affecting the conclusion of the paper.113Ysciescopu

Intergenerational impacts of maternal mortality: Qualitative findings from rural Malawi

Background: Maternal mortality, although largely preventable, remains unacceptably high in developing countries such as Malawi and creates a number of intergenerational impacts. Few studies have investigated the far-reaching impacts of maternal death beyond infant survival. This study demonstrates the short- and long-term impacts of maternal death on children, families, and the community in order to raise awareness of the true costs of maternal mortality and poor maternal health care in Neno, a rural and remote district in Malawi. Methods: Qualitative in-depth interviews were conducted to assess the impact of maternal mortality on child, family, and community well-being. We conducted 20 key informant interviews, 20 stakeholder interviews, and six sex-stratified focus group discussions in the seven health centers that cover the district. Transcripts were translated, coded, and analyzed in NVivo 10. Results: Participants noted a number of far-reaching impacts on orphaned children, their new caretakers, and extended families following a maternal death. Female relatives typically took on caregiving responsibilities for orphaned children, regardless of the accompanying financial hardship and frequent lack of familial or governmental support. Maternal death exacerbated children’s vulnerabilities to long-term health and social impacts related to nutrition, education, employment, early partnership, pregnancy, and caretaking. Impacts were particularly salient for female children who were often forced to take on the majority of the household responsibilities. Participants cited a number of barriers to accessing quality child health care or support services, and many were unaware of programming available to assist them in raising orphaned children or how to access these services. Conclusions: In order to both reduce preventable maternal mortality and diminish the impacts on children, extended families, and communities, our findings highlight the importance of financing and implementing universal access to emergency obstetric and neonatal care, and contraception, as well as social protection programs, including among remote populations

X-ray scattering and spectroscopy of supercooled water and ice

This thesis presents experimental studies of water and ice at near-atmospheric pressures using intense x-rays only accessible at synchrotrons and free-electron lasers. In particular, it focuses on the deeply supercooled, metastable state and its implications on ice nucleation. The local structure of the liquid phase was studied by x-ray scattering over a wide temperature range extending from 339 K down to 227 K. In order to be able to study the deeply supercooled liquid, micron-sized water droplets were evaporatively cooled in vacuum and probed by ultrashort x-ray pulses. This is to date the lowest temperature at which measurements of the structure have been performed on bulk liquid water cooled from room temperature. Upon deep supercooling, the structure evolved toward that of a low-density liquid with local tetrahedral coordination. At ~230 K, where the low-density liquid structure started to dominate, the number of droplets containing ice nuclei increased rapidly. The estimated nucleation rate suggests that there is a “fragile-to-strong” transition in the dynamics of the liquid below 230 K, and its implications on water structure are discussed. Similarly, the electronic structure of deeply supercooled water was studied by x-ray emission spectroscopy down to 222 K, but the spectral changes expected from the structural transformation remained absent and explanations are discussed. At high fluence, the non-linear dependence of the x-ray emission yield indicated that there were high valence hole densities created during the x-ray pulse length due to Auger cascades, resulting in reabsorption of the x-ray emission. Finally, the hydrogen-bonded network in water was studied by x-ray absorption spectroscopy and compared to various ices. It was found that the pre-edge absorption cross-section, which is associated with distorted hydrogen bonds, could be minimized for crystalline ice grown on a hydrophobic BaF2(111) surface with low concentration of nucleation centers.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript. Paper 5: Manuscript. Paper 6: Manuscript.</p

Heterogeneous Ice Growth in Micron-Sized Water Droplets Due to Spontaneous Freezing

Understanding how ice nucleates and grows into larger crystals is of crucial importance for many research fields. The purpose of this study was to shed light on the phase and structure of ice once a nucleus is formed inside a metastable water droplet. Wide-angle X-ray scattering (WAXS) was performed on micron-sized droplets evaporatively cooled to temperatures where homogeneous nucleation occurs. We found that for our weak hits ice grows more cubic compared to the strong hits that are completely hexagonal. Due to efficient heat removal caused by evaporation, we propose that the cubicity of ice at the vicinity of the droplet’s surface is higher than for ice formed within the bulk of the droplet. Moreover, the Bragg peaks were classified based on their geometrical shapes and positions in reciprocal space, which showed that ice grows heterogeneously with a significant population of peaks indicative of truncation rods and crystal defects. Frequent occurrences of the (100) reflection with extended in-planar structure suggested that large planar ice crystals form at the droplet surface, then fracture into smaller domains to accommodate to the curvature of the droplets. Planar faulting due to misaligned domains would explain the increased cubicity close to the droplet surface. QC 20220223</p

Quantitative conversion of biomass in giant DNA virus infection

Bioconversion of organic materials is the foundation of many applications in chemical engineering, microbiology and biochemistry. Herein, we introduce a new methodology to quantitatively determine conversion of biomass in viral infections while simultaneously imaging morphological changes of the host cell. As proof of concept, the viral replication of an unidentified giant DNA virus and the cellular response of an amoebal host are studied using soft X-ray microscopy, titration dilution measurements and thermal gravimetric analysis. We find that virions produced inside the cell are visible from 18 h post infection and their numbers increase gradually to a burst size of 280-660 virions. Due to the large size of the virion and its strong X-ray absorption contrast, we estimate that the burst size corresponds to a conversion of 6-12% of carbonaceous biomass from amoebal host to virus. The occurrence of virion production correlates with the appearance of a possible viral factory and morphological changes in the phagosomes and contractile vacuole complex of the amoeba, whereas the nucleus and nucleolus appear unaffected throughout most of the replication cycle

Maxima in the thermodynamic response and correlation functions of deeply supercooled water

Femtosecond x-ray laser pulses were used to probe micrometer-sized water droplets that were cooled down to 227 kelvin in vacuum. Isothermal compressibility and correlation length were extracted from x-ray scattering at the low-momentum transfer region. The temperature dependence of these thermodynamic response and correlation functions shows maxima at 229 kelvin for water and 233 kelvin for heavy water. In addition, we observed that the liquids undergo the fastest growth of tetrahedral structures at similar temperatures. These observations point to the existence of a Widom line, defined as the locus of maximum correlation length emanating from a critical point at positive pressures in the deeply supercooled regime. The difference in the maximum value of the isothermal compressibility between the two isotopes shows the importance of nuclear quantum effects.1131Nsciescopu

Observing ice structure of micron-sized vapor-deposited ice with an x-ray free-electron laser

The direct observation of the structure of micrometer-sized vapor-deposited ice is performed at Pohang Accelerator Laboratory x-ray free electron laser (PAL-XFEL). The formation of micrometer-sized ice crystals and their structure is important in various fields, including atmospheric science, cryobiology, and astrophysics, but understanding the structure of micrometer-sized ice crystals remains challenging due to the lack of direct observation. Using intense x-ray diffraction from PAL-XFEL, we could observe the structure of micrometer-sized vapor-deposited ice below 150 K with a thickness of 2–50 μm grown in an ultrahigh vacuum chamber. The structure of the ice grown comprises cubic and hexagonal sequences that are randomly arranged to produce a stacking-disordered ice. We observed that ice with a high cubicity of more than 80% was transformed to partially oriented hexagonal ice when the thickness of the ice deposition grew beyond 5 μm. This suggests that precise temperature control and clean deposition conditions allow μm-thick ice films with high cubicity to be grown on hydrophilic Si$_3$N$_4$ membranes. The low influence of impurities could enable in situ diffraction experiments of ice nucleation and growth from interfacial layers to bulk ice

Observing ice structure of micron-sized vapor-deposited ice with an x-ray free-electron laser

The direct observation of the structure of micrometer-sized vapor-deposited ice is performed at Pohang Accelerator Laboratory x-ray free electron laser (PAL-XFEL). The formation of micrometer-sized ice crystals and their structure is important in various fields, including atmospheric science, cryobiology, and astrophysics, but understanding the structure of micrometer-sized ice crystals remains challenging due to the lack of direct observation. Using intense x-ray diffraction from PAL-XFEL, we could observe the structure of micrometer-sized vapor-deposited ice below 150K with a thickness of 2-50 mu m grown in an ultrahigh vacuum chamber. The structure of the ice grown comprises cubic and hexagonal sequences that are randomly arranged to produce a stacking-disordered ice. We observed that ice with a high cubicity of more than 80% was transformed to partially oriented hexagonal ice when the thickness of the ice deposition grew beyond 5 mu m. This suggests that precise temperature control and clean deposition conditions allow mu m-thick ice films with high cubicity to be grown on hydrophilic Si3N4 membranes. The low influence of impurities could enable in situ diffraction experiments of ice nucleation and growth from interfacial layers to bulk ice