Joseph Rotblat: Moral Dilemmas and the Manhattan Project

John Fitzgerald Kennedy famously said, “One man can make a difference and every man should try.”1 Joseph Rotblat (1908–2005) was the quintessence of Kennedy’s conviction. He was the only scientist who left Los Alamos after it transpired that the atomic bomb being developed there was intended for use against adversaries other than Nazi Germany. I explore Rotblat’s early research in Warsaw and Liverpool, which established his reputation as a highly capable experimental physicist, and which led him to join the Manhattan Project at Los Alamos in 1944. I examine his motivation for resigning from the project in 1945, and the unwillingness of his fellow scientists to follow suit, which draws attention to the continuing discourse on the responsibility of scientists for the consequences of their research.     

Hydrophobization and evaluation of absorption capacity of Aloe vera,Opuntia ficus-indica and Gelidium for oil spill cleanup

Natural sorbent materials have practical advantages for the oil spill cleanup, whose advantages are their low-cost, feasibility for real-life applications and environmental adaptability. In this work, absorption capacity was determined for lyophilized aloe, nopal and agar and their composites with silica, Fe₃O₄/polysterene and multi-wall carbon nanotubes (MWCNTs). Freeze-drying was performed in order to preserve the structure and increase the internal volume of sorbents. The structures of lyophilized sorbents and composites were analyzed by scanning electron microscopy (SEM). SEM images for lyophilized sorbents show a tridimensional arrangement formed by plant-derived materials, which allows the oil absorption. The composites keep their tridimensional structure after freeze-drying and composite formation and exhibit coupling between both materials. Absorption capacity of aloe, nopal and agar are 9?g/g, 3?g/g, and 26?g/g, respectively without any pretreatment. Composites with Fe₃O₄/polysterene own capacities of 5.8?g/g, 2.8?g/g, and 14?g/g, respectively. Finally, for MWCNT composites, capacities are 7.8?g/g, 2.9?g/g and 23?g/g. A significant difference of adsorption capacity between lyophilized sorbents and composites is attributed to lyophilized materials absorbing oil, water and other compounds. Meanwhile, for composites the absorption is a more selective process, since the hydrophobization does not allow the absorption of water.     

An Object-Based Shale Permeability Model: Non-Darcy Gas Flow,Sorption, and Surface Diffusion Effects

Shale samples consist of two major components: organic matter (OM) and inorganic mineral component (iOM). Each component has its distinct pore network topology and morphology, which necessitates generating a model capable of distinguishing the two media. We constructed an object-based model using the OM and iOM composition of shale samples. In the model, we integrated information such as OM population and size distribution, as well as its associated pore-size distribution. For the iOM part, we used mineralogy and pore-size information derived from X-ray diffraction, scanning electron microscopy, and nitrogen sorption measurements. Our proposed model results in millimeter-scale 2D realizations of shale samples by honoring OM and mineral types, their compositions, shapes, and size distributions. The model can capture heterogeneities smaller than 1 mm. We studied the effects of different gas flow processes and found that Knudsen diffusion and gas slippage dominate the flow, but surface diffusion has little impact on total gas flow.     

Three‐Dimensional Branched and Faceted Gold–Ruthenium Nanoparticles: Using Nanostructure to Improve Stability in Oxygen Evolution Electrocatalysis

Achieving stability with highly active Ru nanoparticles for electrocatalysis is a major challenge for the oxygen evolution reaction. As improved stability of Ru catalysts has been shown for bulk surfaces with low‐index facets, there is an opportunity to incorporate these stable facets into Ru nanoparticles. Now, a new solution synthesis is presented in which hexagonal close‐packed structured Ru is grown on Au to form nanoparticles with 3D branches. Exposing low‐index facets on these 3D branches creates stable reaction kinetics to achieve high activity and the highest stability observed for Ru nanoparticle oxygen evolution reaction catalysts. These design principles provide a synthetic strategy to achieve stable and active electrocatalysts.     

Quantitative Prediction of Rate Constants for Aqueous Racemization To Avoid Pointless Stereoselective Syntheses

Racemization has a large impact upon the biological properties of molecules but the chemical scope of compounds with known rate constants for racemization in aqueous conditions was hitherto limited. To address this remarkable blind spot, we have measured the kinetics for racemization of 28 compounds using circular dichroism and ¹H NMR spectroscopy. We show that rate constants for racemization (measured by ourselves and others) correlate well with deprotonation energies from quantum mechanical (QM) and group contribution calculations. Such calculations thus provide predictions of the second‐order rate constants for general‐base‐catalyzed racemization that are usefully accurate. When applied to recent publications describing the stereoselective synthesis of compounds of purported biological value, the calculations reveal that racemization would be sufficiently fast to render these expensive syntheses pointless.     

Photoflocculation of TiO2 microgel mixed suspensions

Photocatalytic TiO 2 was derivatized with an amino silane to give a positively charged colloidal suspension in water. UV irradiation of the cationic titania oxidized the organo silane coating converting the titania to a negatively charged colloid. Irradiation of mixed suspensions of cationic titania and cationic polyvinylamine microgel induced catastrophic flocculation. Electrophoresis and XPS evidence suggests that the UV removed the amine groups from the titania resulting in heteroflocculation of anionic titania with cationic microgel particles.     

Controlling crystallization and its absence: proteins, colloids and patchy models

The ability to control the crystallization behaviour (including its absence) of particles, be they biomolecules such as globular proteins, inorganic colloids, nanoparticles, or metal atoms in an alloy, is of both fundamental and technological importance. Much can be learnt from the exquisite control that biological systems exert over the behaviour of proteins, where protein crystallization and aggregation are generally suppressed, but where in particular instances complex crystalline assemblies can be formed that have a functional purpose. We also explore the insights that can be obtained from computational modelling, focussing on the subtle interplay between the interparticle interactions, the preferred local order and the resulting crystallization kinetics. In particular, we highlight the role played by "frustration", where there is an incompatibility between the preferred local order and the global crystalline order, using examples from atomic glass formers and model anisotropic particles.     

Polymeric micelle systems of hydroxycamptothecin based on amphiphilic N-alkyl-N-trimethyl chitosan derivatives

This research investigated the possible utilization of amphiphilic N-octyl-N-trimethyl chitosan (OTMCS) derivatives in solublization and controlled release of 10-hydroxycamptothecin (10-HCPT), a hydrophobic anticancer drug. The release behavior of the 10-HCPT-OTMCS micelles was measured and compared to that of a commercial 10-HCPT lyophilized powder in vitro and in vivo. This research also examined the effects of chemical structure of the chitosan derivatives and the micellar preparation conditions on the encapsulation efficiency, drug loading content, and particle size of the polymeric micelles. The results showed that these chitosan derivatives were able to self-assemble and form spherical shape polymeric micelles with an average particle size range of 24–280 nm and a drug loading content of 4.1–32.5%, depending on the modified structures and loading procedures. The solubility of 10-HCPT in aqueous fluid was increased about 80,000-fold from 2 ng/ml in water to 1.9 mg/ml in OTMCS micellar (degree of octyl and trimethyl substitution is 8% and 54%, respectively) solution. In addition, OTMCS was able to modulate the in vitro release of 10-HCPT and improve its pharmacokinetic properties and lactone ring stability in vivo. These data suggested the possible utilization of the amphiphilic micellar chitosan derivatives as carriers for hydrophobic drugs for improving their delivery and release properties.