A flexible synthesis of C-6 and N-1 analogues of a 4-amino-1,3-dihydroimidazo[4,5-c]pyridin-2-one core

A flexible route which enables access to derivatives of 4-amino-1,3-dihydroimidazo[4,5-c]pyridin-2-ones is described. Issues of selectivity, reaction safety, and low yields in original routes are overcome with the key improvements to the route, including a Negishi cross-coupling and use of a carbamate as a protecting group and intrinsic carbonyl source. The new route enables variation of C-6 and N-1 substituents.     

Plastic shear deformation of a thin strain-hardening disc: variational principles

An analytical solution is derived for the problem of shearing of a thin disc of incompressible rigid, plastic strain-hardening material. The solution is obtained by a methodology introduced by the author in previous publications, relying fundamentally on continuity of the rotation-rate vector field. A variational theorem is derived which shows that the velocity vector field is unique if the boundary values are properly prescribed. The derived solution is compared to experiments, with which it shows good agreement.     

Peptide modification through site-selective residue interconversion: application of the rhodium-catalysed 1,4-addition of aryl siloxanes and boronates

The site-selective interconversion of serine and cysteine residues of di- and tripeptides into phenylalanine derivatives, bearing a range of functionalities, has been achieved in high yield and selectivity through the common dehydroalanine intermediate. Through the application and development of the rhodium-catalysed 1,4-addition to α,β-dehydroamino acid moieties with organometallic nucleophiles, a variety of peptides have been successfully modified to contain unnatural amino acid residues in pre-designated residue positions.     

A Short Review of Experimental and Computational Diagnostics for Radiofrequency Plasma Micro-thrusters

Experimental and computational diagnostics for radiofrequency plasma micro-thrusters are presented, based on the low power (10–100 W) electrothermal thruster prototype, Mini Pocket Rocket, developed for use on the Cubesat nanosatellite platform. Computer simulations include computer fluid dynamics simulations and particle in cell simulations while experimental results are obtained using a variety of electrostatic, optical and momentum probes. The output and limitations of each diagnostic are discussed within the context of device development for space use.     

Safety and waste considerations in donated blood screening

We study an important problem faced by Blood Centers, of selecting screening tests for donated blood to reduce the risk of “transfusion-transmitted infectious diseases” (TTIs), including the human immunodeficiency virus (HIV), hepatitis viruses, human T-cell lymphotropic virus, syphilis, West Nile Virus, and Chagas’ Disease. This decision has a significant impact on health care quality in both developed and developing countries. The budget-constrained decision-maker needs to construct a portfolio of screening tests, from a set of available tests, each with given efficacy (sensitivity and specificity) and cost, to administer to each unit of donated blood so as to minimize the “risk” of a TTI for blood classified as “infection-free.” While doing this, it is critical, for a viable blood system, that the decision-maker does not falsely (i.e., through screening error) discard too much of the infection-free blood (“waste”). We construct mathematical models of this decision problem, considering the various objective functions (minimization of the TTI risk or the weighted TTI risk) and various constraints (on budget and wasted blood) relevant in practice. Our work generates insights on the test selection problem. We show, for example, that a reduction in risk does not necessarily come at the expense of an increase in waste. This underscores the importance of considering these different metrics in decision-making through an optimization-based model. Our work also highlights the importance of generating region-specific testing schemes that explicitly take into account the regional prevalence and co-infection rates, along with the impacts of the infections on the society and individuals.     

Allocation of flexible and indivisible resources with decision postponement and demand learning

We consider a firm that uses two perishable resources to satisfy two demand types. Resources are flexible such that each resource can be used to satisfy either demand type. Resources are also indivisible such that the entire resource must be allocated to the same demand type. This type of resource flexibility can be found in different applications such as movie theater complexes, cruise lines, and airlines. In our model, customers arrive according to independent Poisson processes, but the arrival rates are uncertain. Thus, the manager can learn about customer arrival rates from earlier demand figures and potentially increase the sales by postponing the resource allocation decision. We consider two settings, and derive the optimal resource allocation policy for one setting and develop a heuristic policy for the other. Our analysis provides managerial insights into the effectiveness of different resource allocation mechanisms for flexible and indivisible resources.     

Water-vapor adsorption and surface area measurement of poorly crystalline boehmite

Water-vapor adsorption on poorly crystalline boehmite (PCB) was studied using a gravimetric FTIR apparatus that measured FTIR spectra and water adsorption isotherms simultaneously. The intensity of the delta(HOH) band of adsorbed water changed linearly with water content and this linear relationship was used to determine the dry mass of the sample. Adsorption and desorption isotherms of PCB showed a Type IV isotherm. The BET(H2O) surface area of PCB was 514+/-36 m2/g. The mean crystallite dimensions of PCB were estimated to be 4.5 x 2.2 x 10.0 nm (dimensions along the a, b, and c axes, respectively) based on application of the Scherrer equation to powder diffraction data of PCB. A surface area value of 504+/-45 m2/g calculated using the mean crystallite dimensions was in good agreement with the BET(H2O) surface area. This work also demonstrated a method to determine surface areas for materials with minimal perturbation of their surface structure. In addition, the FTIR spectra of PCB were influenced by changes in water content. The delta(AlOH) band at 835 cm(-1) observed under dry conditions was assigned to the non-H-bonded surface OH groups. As the amount of adsorbed water increased, the intensity at 835 cm(-1) decreased and that at 890 and 965 cm(-1) increased. The 890- and 965-cm(-1) bands are assigned to surface OH groups H-bonded with adsorbed water.     

Decision support for hospital evacuation and emergency response

Evacuation planning is an important part of a hospital’s emergency management plan. In an evacuation the safety and health of patients is the fundamental success parameter. Thus, in this paper we introduce an evacuation model, appropriate for planning and operations, that has the objective of minimizing expected risk, both the threat risk that is forcing the evacuation, and the risk inherent in transporting patients, some in critical condition. Specifically, we study the allocation of patients, categorized by criticality and care requirements, to a limited fleet of vehicles of various capacities and medical capabilities, to be transported to appropriate receiving hospitals considering the current available space in each hospital for each category of patient. The model is an integer program, where the non-linear expected risks are calculated a-priori. This model has a structure that has excellent solution characteristics that permit us to solve large problems in a reasonable time, enabling the model to potentially be used for both planning and operations. To illustrate the solvability of this model and demonstrate its characteristics, we apply it to a realistic case study based on the evacuation of a large regional hospital.     

The optimal resource portfolio under consumer choice and demand risk for vertically differentiated products

We study the optimal resource portfolio of a firm that sells two vertically differentiated products and utilizes resource flexibility and responsive pricing. We model this decision problem as a two-stage stochastic programming problem with recourse: In the first stage, the firm determines its resource mix and capacities so as to maximize the expected profit under demand uncertainty; in the second stage, uncertainty is resolved and the firm determines its production and pricing decision, constrained by its investment decision. We show that the objective function of this decision problem is not well-behaved (ie, it may have multiple local maxima). Using the concept of Pareto dominance, we reduce the feasible investment region, without loss of optimality, to one in which the objective function is well-behaved everywhere. This reduction allows us to derive the necessary and sufficient conditions for the optimal capacity decision and to gain insights.