Characteristics of an immobilized lipase for the commercial synthesis of esters

The lipase-catalyzed synthesis of ester bonds has been well-documented lately and is of much current commercial interest. Immobilization of a fungal lipase on a unique macroporous support allows not only the ability to operate in non-aqueous media but to catalyze ester synthesis in quantitative yields, employing attractive commercial conditions. Catalyst dose and process configurations will be illustrated. The capability of the catalyst to operate efficiently in reverse under a variety of unnatural, hostile, solvent-containing environments will be discussed. The range of substrates for this immobilized lipase, Lipzome, has been investigated. The enzyme will catalyze ester synthesis with saturated, unsaturated and a variety of branched carboxylic acids. The alcohol specificity for this enzyme also is equally broad. A wide variety of straight-chain, branched and polar alcohols can be substrates. In addition, some examples of alcohol specificity for kinetic isomer resolution will be cited. Presented at the symposium “The Biology, Biotechnology and Technology of Lipases” at the 78th annual meeting of the American Oil Chemists’ Society held May 17–21, 1987, in New Orleans, Louisiana.     

Assessing Adaptive Expertise in Undergraduate Biomechanics

This paper describes the design, development, implementation, and assessment of a multimedia‐based learning module focused on biomechanics. The module is comprised of three challenges and is based on a model of learning and instruction known as the How People Learn (HPL) framework. Classroom assessment of the first challenge was undertaken to test the hypothesis that the HPL approach increases adaptive expertise in movement biomechanics. Student achievement was quantified using pre‐ and post‐test questionnaires designed to measure changes in three facets of adaptive expertise: factual and conceptual knowledge and transfer. The results showed that the HPL approach increased students' conceptual knowledge as well as their ability to transfer knowledge to new situations. These findings indicate that challenge‐based instruction, when combined with an intellectually engaging curriculum and principled instructional design, can accelerate the trajectory of novice to expert development in bioengineering education.     

A Study of Mill Power as a Function of Media Type and Shape

ABSTRACT

The mill power of a laboratory scale tumbling media mill was determined for the different shapes of media which are used industrially for dry grinding of quartz to produce silica flow. The tested media were ceramic balls and cylinders of high density alumina, and natural flint pebbles; tests were performed over ranges of filling levels and rotational speeds, with and without lifters in the mill. The experiments showed that ceramic balls at low levels of ball charge slipped excessively against the mill wall when the mill interior was smooth and without lifters. The use of lifters gave a consistent tumbling action and, under otherwise comparable conditions, mill power was linearly proportional to media density. Equations were developed which enable the comparison of mill conditions which give the same mill power draw for the different shapes and densities. Combined with studies of grinding kinetics, this enables comparison of the grinding efficiencies for different media shapes.     

Space–time interface-tracking with topology change (ST-TC)

To address the computational challenges associated with contact between moving interfaces, such as those in cardiovascular fluid–structure interaction (FSI), parachute FSI, and flapping-wing aerodynamics, we introduce a space–time (ST) interface-tracking method that can deal with topology change (TC). In cardiovascular FSI, our primary target is heart valves. The method is a new version of the deforming-spatial-domain/stabilized space–time (DSD/SST) method, and we call it ST-TC. It includes a master–slave system that maintains the connectivity of the “parent” mesh when there is contact between the moving interfaces. It is an efficient, practical alternative to using unstructured ST meshes, but without giving up on the accurate representation of the interface or consistent representation of the interface motion. We explain the method with conceptual examples and present 2D test computations with models representative of the classes of problems we are targeting.     

Improving water security through rainwater harvesting: a case from Guatemala and the potential for expanding coverage

Municipal infrastructure for water supply and delivery often does not reach populations in rural and peri-urban areas. This article examines rainwater harvesting as a means of increasing water security in such areas, through the case of Guachtuq, a peri-urban community outside San Cristóbal, Alta Verapaz, Guatemala. The project team designed a rainwater harvesting system to improve three dimensions of water security: quantity, quality and access. The design was implemented for 12 households and evaluated for its contribution to water security and for the potential of expanding project coverage to the region and beyond. The system has improved water security. Several concerns remain, however, regarding the potential of expanding the project to other households in the region and beyond, including system cost, water quality and the individualization of public responsibility for water security.     

Near‐Infrared Intraoperative Chemiluminescence Imaging

Intraoperative imaging technologies recently entered the operating room, and their implementation is revolutionizing how physicians plan, monitor, and perform surgical interventions. In this work, we present a novel surgical imaging reporter system: intraoperative chemiluminescence imaging (ICI). To this end, we have leveraged the ability of a chemiluminescent metal complex to generate near‐infrared light upon exposure to an aqueous solution of Ce⁴⁺ in the presence of reducing tissue or blood components. An optical camera spatially resolves the resulting photon flux. We describe the construction and application of a prototype imaging setup, which achieves a detection limit as low as 6.9 pmol cm^?2 of the transition‐metal‐based ICI agent. As a proof of concept, we use ICI for the in vivo detection of our transition metal tracer following both systemic and subdermal injections. The very high signal‐to‐noise ratios make ICI an interesting candidate for the development of new intraoperative imaging technologies.     

7,8-Dihydro-8-oxoguanosine Lesions Inhibit the Theophylline Aptamer or Change Its Selectivity

Aptamers are attractive constructs due to their high affinity/selectivity towards a target. Here 7,8-dihydro-8-oxoguanosine (8-oxoG) has been used, due in part to its unique H-bonding capabilities (Watson–Crick or Hoogsteen), to expand the “RNA alphabet”. Its impact on the theophylline RNA aptamer was explored by modifying its binding pocket at positions G11, G25, or G26. Structural probing, with RNases A and T₁, showed that modification at G11 leads to a drastic structural change, whereas the G25-/G26-modified analogues exhibited cleavage patterns similar to that of the canonical construct. The recognition properties towards three xanthine derivatives were then explored through thermophoresis. Modifying the aptamer at position G11 led to binding inhibition. Modification at G25, however, changed the selectivity towards theobromine (K_d≈160 μm ), with a poor affinity for theophylline (K_d>1.5 mm ) being observed. Overall, 8-oxoG can have an impact on the structures of aptamers in a position-dependent manner, leading to altered target selectivity.     

Modeling segregation of bidisperse granular materials using physical control parameters in the quasi‐2D bounded heap

Quantitatively predicting segregation of size‐disperse granular materials is of potential value in many industrial applications. We consider granular segregation of size‐bidisperse particles in quasi‐2D bounded heaps, a canonical granular flow, using an advection‐diffusion transport equation with an additional term to account for particle segregation. The equation is characterized by two dimensionless parameters that are functions of control parameters (flow rate, system size, and particle sizes) and kinematic parameters (flowing layer depth, diffusion coefficient, and percolation length scale). As the kinematic parameters are usually difficult to measure in practice, their dependence on the control parameters is determined directly from discrete element method simulations. Using these relationships, it is possible to determine which values of the control parameters result in a mixed or segregated heap. The approach used here is broadly applicable to a wide range of other flow geometries and particle systems. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1524–1534, 2015     

Studies on slag deposit formation in pulverized coal combustors. 1. Results on the wetting and adherence of synthetic coal ash drops on steel

As part of a study of slag deposit formation in pulverized-coal-fired boilers, apparent contact angles and adhesion strengths of molten mineral drops contacted with cooler oxidized steel substrates have been investigated. High-speed photography indicated that freezing of the interface between the molten drop and metal surface occurred in milliseconds. Adherence occurred between an oxide film on the metal and the drop, adherence was weak on stainless steels, and particles of oxide film were broken away from the substrate when the drops were sheared off. Higher substrate temperatures gave increased adhesion, with a larger area of strong interaction between the oxide and the drop interface and less area of weak interaction. Addition of compounds to lower the liquidus temperature of the drop gave increased adherence. Pyrite drops were converted to mainly pyrrhotite on melting and showed a high degree of wetting and adherence to the oxidized steel even at low temperatures.