Molecular basis for the mechanical response of sulfa drug crystals

Comprehension of the nanomechanical response of crystalline materials requires the understanding of the elastic and plastic deformation mechanisms in terms of the underlying crystal structures. Nanoindentation data were combined with structural and computational inputs to derive a molecular-level understanding of the nanomechanical response in eight prototypical sulfa drug molecular crystals. The magnitude of the modulus, E, was strongly connected to the non-covalent bond features, that is, the bond strength, the relative orientation with the measured crystal facet and their disposition in the crystal lattice. Additional features derived from the current study are the following. Firstly, robust synthons well isolated by weak and dispersive interactions reduce the material stiffness; in contrast, the interweaving of interactions with diverse energetics fortifies the crystal packing. Secondly, mere observation of layered structures with orthogonal distribution of strong and weak interactions is a prerequisite, but inadequate, to attain higher plasticity. Thirdly, interlocked molecular arrangements prevent long-range sliding of molecular planes and, hence, lead to enhanced E values. In a broader perspective, the observations are remarkable in deriving a molecular basis of the mechanical properties of crystalline solids, which can be exploited through crystal engineering for the purposeful design of materials with specific properties

Dimorphs of a Benzothiophene-quinoline Derivative with Distinct Mechanical, Optical, Photophysical and Conducting Properties

Because of distinct molecular conformations, packing modes, interaction types, and consequently their physicochemical properties, polymorphic forms of organic conjugated small molecules are intrinsically ideal for elucidating the relationship between their microstructures and the transcribed properties. Ethyl-2‐(1‐benzothiophene‐2‐yl)quinoline‐4‐carboxylate (BZQ) exists as dimorphs with distinct crystal habits―blocks (BZB) and needles (BZN). The crystal forms differ in their molecular arrangements―BZB has a slip-stacked column-like structure in contrast to a zig-zag crystal packing with limited π–overlap in BZN―and their photophysical and conducting properties. The BZB crystals characterized by extended π-stacking along [100] demonstrated semiconductor behavior, whereas the BZN, with its zig-zag crystal packing and limited stacking characteristics, was reckoned as an insulator. Monotropically related crystal forms also differ in their nanomechanical properties, with BZB crystals being considerably softer than BZN crystals. This discrepancy in mechanical behavior can be attributed to the distinct molecular arrangements adopted by each crystal form, resulting in unique mechanisms to relieve the strain generated during nanoindentation experiments. Waveguiding experiments on the acicular crystals of BZN revealed the passive waveguiding properties of the crystals. Excitation of these crystals using a 532 nm laser confirmed the propagation of elastically scattered photons (green) and the subsequent generation of inelastically scattered (orange) photons by the crystals. Further, the dimorphs display dissimilar photoluminescence properties; they are both blue-emissive, but BZN displays twice the quantum yield of BZB. This study underscores the integral role of polymorphism in modulating the mechanical, photophysical, and conducting properties of functional molecular materials. Importantly, our findings reveal the existence of light-emitting crystal polymorphs with varying electric conductivity, a relatively scarce phenomenon in the literature

Plasmablastic myeloma presenting as rapidly progressive renal failure in a young adult

Multiple myeloma (MM) is a condition where there is malignant proliferation of plasma cells. There is a strong correlation with age, peaking at 60-70 years. The clinical course in adolescents and young individuals is generally indolent and the survival is longer. We report a case of a 28-year-old male, who was diagnosed to have plasmablastic myeloma, an atypical variant of MM with a poor prognosis, presenting as rapidly progressive renal failure. He was given induction chemotherapy and then underwent autologous peripheral blood stem cell transplantation

Structural Snapshots of Metastable Intermediates Reveals Sequential Addition of Growth Units in the Formation of an Archetypal Coordination Complex: Anisotropic Layer Migration and Solid-State Thermochromic Transitions

Kinetically trapped partially preassembled metastable structures afford vital inputs on the reaction progression and the formation mechanism of technologically promising coordination assemblies. We report the structural and transformational relations in a series of coordination complexes, [Co­(ad)₂(H₂O)₄]­(btc-)₂(H₂O)₂ (<b>1</b>), [Co­(ad)₂(H₂O)₄]­[Co­(H₂O)₆]­(btc-)₂(H₂O)₁₀ (<b>2</b>), [Co₃(ad)₂(H₂O)₁₄]­(btc-)₂(H₂O)₄ (<b>3</b>), and [Co₃(ad)₂(btc-)₂(H₂O)₈] (<b>4</b>), in which ad = adenine and btc = 1,3,5-benzenetricarboxylic acid, to provide insights on sequential structure evolution in an archetypal coordination assembly. Crystals of <b>3</b> undergo solid-state thermochromic transformation to a glassy phase <b>5</b> consequent to dehydration and anation reaction. With carefully optimized thermal treatment, we obtained a transient crystalline phase <b>4</b>, which unambiguously proves a restructuring in the Co­(II) coordination geometry from octahedral to trigonal bipyramidal. With the <b>3</b> → <b>4</b> transformation, the crystal surface undergoes drastic modification. Surface reconstruction events associated with photoreactions in the molecular crystals are noted, but analogous observations for thermally induced events are exceptional and unprecedented for coordination complexes. Correlative atomic force microscopy, nanoindentation, and structural inputs provide insights on the surface reconstruction events brought about by anisotropic long-range layer migration subsequent to <b>3</b> → <b>4</b> transition. The slip plane (011̅) that crosses the crystal face (010) at an optimal angle offers an energetically viable route for layer reorientation and migration

Load shedding strategies for preventing cascading failures in power grid

Load shedding has always been a commonly adopted method in emergency situations to maintain power system reliability. Several load reduction strategies have been suggested in the past but most are complex and not scalable. In this paper, we have proposed and thoroughly investigated three load shedding strategies to prevent cascading failures in power grid. The first strategy is a base line case called the homogeneous load shedding strategy. It reduces load homogeneously in all the buses of the system. This strategy is extremely simple and fast, and these properties motivate its use in some specific scenarios in spite of its inefficiencies. Next, to accurately find the location and amount of load shedding, we propose a linear optimization formulation which is much more efficient in overall load shedding in the system. A novel tree heuristic is proposed to overcome the drawbacks of the optimization, namely fairness and scalability. The tree heuristic is linear and very simple to implement. In general, it gives close to optimal results. The results of the tree strategy are compared with that of another existing heuristic and it is found that the tree performs equal to or better than the existing heuristic for all cases