Evidence of Sharp Transitions between Octahedral and Capped Trigonal Prism States of the Solvation Shell of the Aqueous Fe3+ Ion.

The structure of the solvation shell of the aqueous Fe3+ ion has been a subject of controversy due to discrepancies between experiments and different levels of theory. We address this issue by performing simulations for a wide range of ion concentrations, using various potential energy functions, supplemented by density functional theory calculations of selected configurations. The solvation shell undergoes abrupt transitions between two states: a hexacoordinated octahedral (OH) state and a capped trigonal prism (CTP) state with 7-fold coordination. The lifetime of these states is dependent on concentration. In dilute FeCl3 solutions, the lifetimes of both are similar (≈1 ns). However, the lifetime of the OH state increases with ion concentration, while that of the CTP state decreases slightly. When a uniform negative background charge is used instead of explicit counterions, the lifetime of the OH state is greatly overestimated. These findings underscore the need for further experimental measurements and higher-level simulations.

Self-driven solutions and resilience adapted by people with drug-resistant tuberculosis and their caregivers in Bengaluru and Hyderabad, India: a qualitative study.

Background: One-fifth of people with drug-resistance tuberculosis (DR-TB) who were initiated on newer shorter treatment regimen (with injection) had unfavourable treatment outcomes in India as on 2020. Evidence on self-driven solutions and resilience adapted by people with DR-TB (PwDR-TB) towards their multi-dimensional disease and treatment challenges are scarce globally, which we aimed to understand. Methods: In this qualitative study using positive deviance framework, we conducted semi-structured in-depth interviews among consenting adult PwDR-TB (7 women, 13 men) who completed shorter treatment regimen (including injections) with maximum treatment adherence. The study was conducted in the southern districts of Bengaluru and Hyderabad, India between June 2020 and December 2022. Caregivers (14 women, 6 men) and health providers (8 men, 2 women) of PwDR-TB were also interviewed. Interviews were conducted in local language (Kannada, Tamil, Telugu, Urdu and Hindi) and inquired about practices, behaviours, experiences, perceptions and attributes which enabled maximum adherence and resilience of PwDR-TB. Interviews were audio recorded, transcribed, and translated to English and coded for thematic analysis using inductive approach. Findings: Distinctive themes explanatory of the self-driven solutions and resilience exhibited by PwDR-TB and their caregivers were identified: (i) Self-adaptation towards the biological consequences of drugs, by personalised nutritional and adjuvant practices, which helped to improve drug ingestion and therapeutic effects. Also home remedies and self-plans for ameliorating injection pain. (ii) Perceptual adaptation towards drugs aversion and fatigue, by their mind diversion practices, routinisation and normalisation of drug intake process. and constant reinforcement and re-interpretation of bodily signs of disease recovery (iii) Family caregivers intense and participatory care for PwDR-TB, by aiding their essential life activities and ensuring survival, learning and fulfilling special nutritional needs and goal oriented actions to aid drug intake (iv) Health care providers care, marked by swift and timely risk mitigation of side-effects and crisis response (v) Acquired self-efficacy of PwDR-TB, by their decisive family concerns resulting in attitudinal change. Also being sensitised on the detrimental consequences of disease and being motivated through positive examples. Interpretation: Synthesised findings on self-driven solutions and resilience towards the multi-dimensional DR-TB challenges provides opportunity for developing and testing new interventions for its effectiveness in DR-TB care settings globally. Designing and testing personalised cognitive interventions for PwDR-TB: to inculcate attitudinal change and self-efficacy towards medication, developing cognitive reinforcements to address the perception burden of treatment, skill building and mainstreaming the role of family caregivers as therapeutic partners of PwDR-TB, curating self-adaptive behaviours and practices of PwDR-TB to normalise their drug consumptions experiences could be the way forward in building resilience towards DR-TB. Funding: United States Agency for International Development (USAID) through Karnataka Health Promotion Trust (KHPT), Bengaluru, India.

A Dual Perspective of Psycho-Social Barriers and Challenges Experienced by Drug-Resistant TB Patients and Their Caregivers through the Course of Diagnosis and Treatment: Findings from a Qualitative Study in Bengaluru and Hyderabad Districts of South India.

Qualitative insights regarding psycho-social barriers and challenges experienced by drug-resistant tuberculosis (DR-TB) patients and their caregivers are understudied in India. We conducted a qualitative study using semi-structured qualitative interviews among treatment-completed DR-TB patients (n = 20) and caregivers (n = 20) in Bengaluru and Hyderabad districts, which represented two different socio-cultural settings in South India. Criterion sampling was used for recruiting the eligible participants who completed treatment with adherence. "Emotional issues and social barriers" were identified to represent a major challenge for patients and caregivers, which occurred acutely after disease diagnosis, characterized by fear and emotional distress due to their perceived loss of life prospects, severity of symptoms, discomfort, and disease denial. Medication intolerance, chronic symptoms, lack of visible signs of treatment progress, loss of weight, and physical concerns caused subsequent fear and distress during the treatment phases for patients along with experiences of stigma. External triggers generated "decisive moments" of hopelessness and life-ending thoughts for patients at the diagnosis and early treatment phase. Medication related challenges included the perceived burden and power of pills which caused emotional distress for patients and intolerance towards caregivers. Pill burden was found as consequential as the side effects of injections. Challenges related to lack of support were another major theme, in which caregivers lacked resources for treatment support and nutrition. Throughout treatment, caregivers and patients expressed concern about a lack of supportive care from family members, sympathy, and intangible social support. Challenges during hospital admission in terms of lack of privacy, quality of services, individual attention, and empathy from health care workers were reported by patients and caregivers. Despite better adherence, DR-TB patients and caregivers experienced considerable emotional and social consequences. Differentiating DR-TB patients and caregivers' issues at different stages of diagnosis and treatment could help improve patient-centered outcomes in India and other high-burden nations.

Homogeneous nucleation of sheared liquids: advances and insights from simulations and theory.

One of the most ubiquitous and technologically important phenomena in nature is the nucleation of homogeneous flowing systems. The microscopic effects of shear on a nucleating system are still imperfectly understood, although in recent years a consistent picture has emerged. The opposing effects of shear can be split into two major contributions for simple atomic and molecular liquids: increase of the energetic cost of nucleation, and enhancement of the kinetics. In this perspective, we describe the latest computational and theoretical techniques which have been developed over the past two decades. We collate and unify the overarching influences of shear, temperature, and supersaturation on the process of homogeneous nucleation. Experimental techniques and capabilities are discussed, against the backdrop of results from simulations and theory. Although we primarily focus on simple systems, we also touch upon the sheared nucleation of more complex systems, including glasses and polymer melts. We speculate on the promising directions and possible advances that could come to fruition in the future.

Universal Nucleation Behavior of Sheared Systems.

Using molecular simulations and a modified classical nucleation theory, we study the nucleation, under flow, of a variety of liquids: different water models, Lennard-Jones, and hard sphere colloids. Our approach enables us to analyze a wide range of shear rates inaccessible to brute-force simulations. Our results reveal that the variation of the nucleation rate with shear is universal. A simplified version of the theory successfully captures the nonmonotonic temperature dependence of the nucleation behavior, which is shown to originate from the violation of the Stokes-Einstein relation.

A hybrid topological and shape-matching approach for structure analysis.

Properties of crystalline and amorphous materials are characterized by the underlying long-range and local crystalline order. Deformations and defects are structural hallmarks of plasticity, ice formation, and crystal growth mechanisms. Partitioning topological networks into constituent crystal building blocks, which is the basis of topological identification criteria, is an intuitive approach for classification in both bulk and confinement. However, techniques reliant on the convex hull for assigning orientations of component units fail for non-convex blocks. Here, we propose a new framework, called Topological Unit Matching (TUM), which exploits information from topological criteria for an efficient shape-matching procedure. TUM is a general family of algorithms, capable of quantifying deformations and unambiguously determining grains of bulk and confined ice polymorphs. We show that TUM significantly improves the identification of quasi-one-dimensional ice by including deformed prism blocks. We demonstrate the efficacy of TUM by analyzing supercooled water nanoparticles, amorphous ice, and phase transitions in an ice nanotube. We also illustrate the superiority of TUM in resolving topological defect structures with minimal parameterization.

Seeding method for ice nucleation under shear.

Hydrodynamic flow can have complex and far-reaching consequences on the rate of homogeneous nucleation. We present a general formalism for calculating the nucleation rates of simply sheared systems. We have derived an extension to the conventional Classical Nucleation Theory, explicitly embodying the shear rate. Seeded molecular dynamics simulations form the backbone of our approach. The framework can be used for moderate supercooling, at which temperatures brute-force methods are practically infeasible. The competing energetic and kinetic effects of shear arise naturally from the equations. We show how the theory can be used to identify shear regimes of ice nucleation behavior for the mW water model, unifying disparate trends reported in the literature. At each temperature, we define a crossover shear rate in the limit of 1000 s-1-10 000 s-1, beyond which the nucleation rate increases steadily up to a maximum, at the optimal shear rate. For 235 K, 240 K, 255 K, and 260 K, the optimal shear rates are in the range of ≈106 s-1-107 s-1. For very high shear rates beyond 108 s-1, nucleation is strongly inhibited. Our results indicate that the optimal shear rates have a non-monotonic dependence on temperature.

d-SEAMS: Deferred Structural Elucidation Analysis for Molecular Simulations.

Structural analyses are an integral part of computational research on nucleation and supercooled water, whose accuracy and efficiency can impact the validity and feasibility of such studies. The underlying molecular mechanisms of these often elusive and computationally expensive processes can be inferred from the evolution of ice-like structures, determined using appropriate structural analysis techniques. We present d-SEAMS, a free and open-source postprocessing engine for the analysis of molecular dynamics trajectories, which is specifically able to qualitatively classify ice structures in both strong-confinement and bulk systems. For the first time, recent algorithms for confined ice structure determination have been implemented, along with topological network criteria for bulk ice structure determination. We also propose and validate a new order parameter for identifying the building blocks of quasi-one-dimensional ice. Recognizing the need for customization in structural analysis, d-SEAMS has a unique code architecture built with nix and employing a YAML-Lua scripting pipeline. The software has been designed to be user-friendly and extensible. The engine outputs are compatible with popular graphics software suites, allowing for immediate visual insights into the systems studied. We demonstrate the features of d-SEAMS by using it to analyze nucleation in the bulk regime and for quasi-one- and quasi-two-dimensional systems. Structural time evolution and quantitative metrics are determined for heterogeneous ice nucleation on a silver-exposed ß-AgI surface, homogeneous ice nucleation, flat monolayer square ice formation, and freezing of an ice nanotube.

A general topological network criterion for exploring the structure of icy nanoribbons and monolayers.

We develop intuitive metrics for quantifying complex nucleating systems under confinement. These are shown to arise naturally from the analysis of the topological ring network, and are amenable for use as order parameters for such systems. Drawing inspiration from qualitative visual inspection, we introduce a general topological criterion for elucidating the ordered structures of confined water, using a graph theoretic approach. Our criterion is based on primitive rings, and reinterprets the hydrogen-bond-network in terms of these primitives. This approach has no a priori assumptions, except the hydrogen bond definition, and may be used as an exploratory tool for the automated discovery of new ordered phases. We demonstrate the versatility of our criterion by applying it to analyse well-known monolayer ices. Our methodology is then extended to identify the building blocks of one-dimensional n-sided prismatic nanoribbon ices.