A Facile Process for the Preparation of Three‐Dimensional Hollow Zn(OH)2 Nanoflowers at Room Temperature

A facile strategy has been developed to synthesize double‐shelled Zn(OH)₂ nanoflowers (DNFs) at room temperature. The nanoflowers were generated via conversion of Cu₂O nanoparticles (NPs) using ZnCl₂ and Na₂S₂O₃ by a simple process. Outward diffusion of the Cu²⁺, produced by an oxidation process on the surface of NPs, and the inward diffusion of Zn²⁺ by coordination and migration, eventually lead to a hollow cavity in the inner NPs with a double‐shelled 3D hollow flower shapes. The thickness of the inner and outer shells is estimated to be about 20 nm, and the thickness of nanopetals is about 7 nm. The nanoflowers have large surface areas and excellent adsorption properties. As a proof of potential applications, the DNFs exhibited an excellent ability to remove organic molecules from aqueous solutions.     

Valuable New Cyclohexadiene Building Blocks from Cationic η5‐Iron–Carbonyl Complexes Derived from a Microbial Arene Oxidation Product

Biooxidation of benzoic acid by Ralstonia eutropha B9 provides an unusual cyclohexadiene carboxy diol that contains a quaternary stereocentre. Tricarbonyliron derivatives of this chiron, on treatment with acid, give two isomeric η⁵‐cyclohexadienyl complexes as observed by NMR spectroscopy. Both of these can be subjected to the addition of nucleophiles to provide isomeric cyclohexadiene complexes with new substituent patterns, several of which have been characterised crystallographically. De‐metallation of these provides a versatile library of cyclohexadiene building blocks, the utility of which is demonstrated by formal syntheses of oseltamivir. The mechanism of product formation and its stereochemical implications are discussed, as are the procedures undertaken to establish the enantiopurity of a representative cyclohexadiene product.     

On the structure and accuracy of programmed burn

Accurate computation of the evolution of a (typically curved) detonation front in a complex geometry, and of the state behind it, is a practical problem in the design of devices that use high-energy explosives. Direct numerical simulations are infeasible: accuracy demands high resolution of the smallest scale (the reaction zone), which is typically several orders of magnitude smaller than the device scale. Programmed burn is an engineering alternative that has been shown to produce acceptable results at a fraction of the cost. The underlying algorithm prescribes the trajectory of the detonation front a priori and replaces the actual reaction zone by a mock up that is a few computational cells thick and in which the reaction rate is taken to be a constant. The state of the explosive at the end of the reaction zone is thereby computed at a relatively modest cost, and the bulk of the computational effort is reserved for the region behind the reaction zone wherein the products of detonation perform useful work. The reasons for the remarkable fidelity to which the physical situation is captured by the programmed burn are not well-understood. This investigation, aimed at achieving such an understanding, considers a model problem for a steady, curved detonation propagating down a rate stick. It examines the pseudo-reaction-zone structure of the programmed burn, studies the sensitivity of the state of the reaction products to the choice of the reaction zone length, and compares the results to those for the actual, physical reaction zone. Conclusions are drawn as to the causes behind the success of the programmed-burn algorithm. The analysis is based on the asymptotic limits of small front curvature and small departures from the Chapman–Jouguet speed. Results are presented for ideal as well as nonideal explosives.     

Curvilinear deflagration of energetic materials

The effects of material interface curvature on deflagration of a homogeneous solid energetic material (EM) is studied in a limit when the radius of curvature is much larger than the deflagration front thickness. Under the assumption of quasi-steady burning, a method of matched asymptotics is employed do derive first-order curvature corrections to the mass flux across the gas–solid interface as well as to the interface temperature. As an illustration, a problem of quasi-steady spherical particle deflagration is solved numerically and the simulation results are used to verify those obtained through asymptotic analysis. An algorithm for a fully-coupled unsteady solver suitable for EM deflagration simulation is presented. Numerical solution of the unsteady spherical particle deflagration is used to show that the assumption of quasi-steady deflagration is valid.     

Peruvian Food Chain Jenga: Learning Ecosystems with an Interactive Model

A pilot study was conducted on a multimodal educational tool, Peruvian Food Chain Jenga (PFCJ), with 5th‐grade students (N = 54) at a public charter school. The goal was to compare the effectiveness of the multimodal tool to a more traditional presentation of the same materials (food chain) using an experimental/control design. Data collection included a pretest/posttest and a “What I Did/What I Learned” response sheet. Quantitative analysis of pretest/posttest results showed both groups improved from pretest to posttest; however, there was no statistically significant difference between posttest results of experimental and control groups. Qualitative analysis of student open‐ended responses indicated a difference between students who used the PFCJ and students in the control. The most striking difference occurred in how the students perceived the connectedness of species and the awareness of human impact. Our findings suggest that using a model such as PFCJ as a means of teaching and connecting scientific content with practices related to ecosystems is an effective method of engaging students in intelligent discussions about these topics.     

Addressing the sample size problem in behavioural operational research: simulating the newsvendor problem

Laboratory-based experimental studies with human participants are beneficial for testing hypotheses in behavioural operational research. However, such experiments are not without their problems. One specific problem is obtaining a sufficient sample size, not only in terms of the number of participants but also the time they are willing to devote to an experiment. In this paper, we explore how agent-based simulation (ABS) can be used to address the sample size problem and demonstrate the approach in the newsvendor setting. The decision-making strategies of a small sample of individual decision-makers are determined through laboratory experiments. The interactions of these suppliers and retailers are then simulated using an ABS to generate a large sample set of decisions. With only a small number of participants, we demonstrate that it is possible to produce similar results to previous experimental studies that involved much larger sample sizes. We conclude that ABS provides the potential to extend the scope of experimental research in behavioural operational research.     

Projections of Veronese surface and morphisms from projective plane to Grassmannian

In this note, we describe the image of ?² in Gr(2, ?⁴) under a morphism given by a rank two vector bundle on ?² with Chern classes (2, 2).     

Microarrays for the scalable production of metabolically relevant tumour spheroids: a tool for modulating chemosensitivity traits

We report the use of thin film poly(dimethylsiloxane) (PDMS) prints for the arrayed mass production of highly uniform 3-D human HT29 colon carcinoma spheroids. The spheroids have an organotypic density and, as determined by 3-axis imaging, were genuinely spherical. Critically, the array density impacts growth kinetics and can be tuned to produce spheroids ranging in diameter from 200 to 550 μm. The diffusive limit of competition for media occurred with a pitch of ≥1250 μm and was used for the optimal array-based culture of large, viable spheroids. During sustained culture mass transfer gradients surrounding and within the spheroids are established, and lead to growth cessation, altered expression patterns and the formation of a central secondary necrosis. These features reflect the microenvironment of avascularised tumours, making the array format well suited for the production of model tumours with defined sizes and thus defined spatio-temporal pathophysiological gradients. Experimental windows, before and after the onset of hypoxia, were identified and used with an enzyme activity-based viability assay to measure the chemosensitivity towards irinotecan. Compared to monolayer cultures, a marked reduction in the drug efficacy towards the different spheroid culture states was observed and attributed to cell cycle arrest, the 3-D character, scale and/or hypoxia factors. In summary, spheroid culture using the array format has great potential to support drug discovery and development, as well as tumour biology research.     

Effect of Well Orientation (Vertical vs. Horizontal) and Well Length on the Injection of CO<Subscript>2</Subscript> in Deep Saline Aquifers

Simulations of CO₂ injection into confined saline aquifers were conducted for both vertical and horizontal injection wells. The metrics used in quantifying the performances of different injection scenarios included changes in pressure near the injection well, mass of CO₂ dissolved into brine (solubility trapping), and storage efficiency, all evaluated with an assumed injection period of 50 years. Metrics were quantified as functions of well length, well orientation, CO₂ injection rate, and formation anisotropy (ratio of vertical to horizontal conductivity). When equal well lengths are compared, there is not a significant difference between the predicted performances of horizontal and vertical wells. However, the length of a horizontal well may exceed the length of a vertical well because the length of the horizontal well is not constrained to the vertical thickness of the geologic formation. Simulations show that, as the length of the horizontal well is allowed to increase, the geologic formation can receive a significantly higher CO₂ injection rate without exceeding a maximum allowable pressure. This result is observed in both isotropic and anisotropic formations, and suggests that horizontal wells may be advantageous under pressure-limited conditions. However, the use of horizontal wells does not significantly improve the storage efficiency, and under strongly anisotropic conditions, a vertical well provides higher storage efficiency than a horizontal well. We conclude that horizontal wells may be preferable if the goal is to sequester a large amount of CO₂ in a short period of time, but do not offer a significant advantage in terms of long-term capacity of a potential repository.