Dynamics of knowledge-intensive production: An agency-structure framework

In the vast majority of modern technological and knowledge-intensive production systems, human agency and the structure of social interactions among the human individuals are implicated in each other. While the force of agency drives an individual’s urge to introduce innovation and novelty into production, the force of the structuring interactions demands shared expectations and mutual adaptation for co-creation. In an organizational context, when the objective is to manage production work that is governed by the concurrent interplay of both these forces, one might ask whether the cumulative output of each could be reconciled through the emergence of a stable balance between them over time. In this article, I introduce a framework to study the conditions under which this balance can be attained. Based on a real-life application, I show, in particular, that, while a direct realization of the condition is unlikely in practice, it is possible, nevertheless, to establish indirectly the condition through adjustments of certain parameters relevant to the dynamics of a networked system. The work contributes to the growing body of literature that explores the role of coordination between self-driven activities of individuals and their structure-mediated interactions in an underlying social context.     

A high-order low-Mach number AMR construction for chemically reacting flows

A high-order projection scheme was developed for the study of chemically reacting flows in the low-Mach number limit. The numerical approach for the momentum transport uses a combination of cell-centered/cell-averaged discretizations to achieve a fourth order formulation for the pressure projection algorithm. This scheme is coupled with a second order in time operator-split stiff approach for the species and energy equations. The code employs a fourth order, block-structured, adaptive mesh refinement approach to address the challenges posed by the large spectrum of spatial scales encountered in reacting flow computations. Results for advection–diffusion-reaction configurations are used to illustrate the performance of the numerical construction.     

Synthesis of novel glycolipids derived from glycopyranosyl azides and N-(β-glycopyranosyl)azidoacetamides

A general and expedient method based on a click reaction has been developed for the synthesis of novel glycolipids. The Cu(I) catalyzed [3+2] cycloaddition of several fully acetylated β- as well as α-d-glycopyranosyl azides, including the 1,6-diazide derived from d-glucose, with long chain alkyl propargyl ethers gave the respective 1,4-substituted 1,2,3-triazole derivatives in good yields. Treatment of fully acetylated N-(β-glycopyranosyl)azidoacetamides under similar conditions with alkyl propargyl ethers afforded the 1,2,3-triazolylacetamido derivatives in fairly good yields. Zemplen de-O-acetylation of all the fully acetylated derivatives furnished the free glycolipids in quantitative yields.     

Improved synthesis of per-O-acetylated C1 hydroxyglycopyranose and structural study as non-covalent organic framework

An improved method for the synthesis of per-O-acetylated C-1-hydroxyglycopyranose was developed by hydrolysis of per-O-acetylated glycopyranosyl α-chlorides derived from sugars with C-2 axial acetates for example l-rhamnose and d-mannose. 2,3,4-Tri-O-acetyl-α-l-rhamnopyranose crystallized in tetragonal space group I4, a rare phenomenon in carbohydrate literature. The three dimensional packing of the molecule with the help of regular hydrogen bond and C–H···O interactions resulted in the formation of porous framework showing channels with pore size 7 Å.     

Charge transport through Geobacter sulfurreducens biofilms grown on graphite rods

Biofilms of the electroactive bacterium Geobacter sulfurreducens were induced to grow on graphite-rod electrodes under a potential of 0 V (vs Ag/AgCl) in the presence of acetate as an electron donor. Increased anodic currents for bioelectrocatalytic oxidation of acetate were obtained when the electrodes were incubated for longer periods with periodic electron-donor feeding. The maximum current density for acetate oxidation increased 2.8-fold, and the biofilm thickness increased by 4.25-fold, over a time period of 83-147 h. Cyclic voltammetry in the presence of acetate supports a model of heterogeneous electron transfer, one electron at time, from biofilm to electrode through a dominant redox species centered at -0.41 V vs Ag/AgCl. Voltammetry performed under nonturnover conditions provided an estimate of the surface coverage of the redox species of 25 nmol/cm(2). This value was used to estimate a redox species concentration of 7.3 mM within the 34-μm-thick biofilm and a charge-transport diffusion coefficient of 3.6 × 10(-7) cm(2)/s. This value of diffusion coefficient is greater than that observed in traditional thin-film voltammetric studies with redox polymer films containing much higher surface concentrations of redox species and might be associated with proton transport to ensure electroneutrality within the biofilm upon electrolysis.     

Expanding the scope of aminosugars: synthesis of 2-amino septanosyl glycoconjugates using septanosyl fluoride donors

A general strategy amenable to the strerocontrolled synthesis of complex, ring-expanded analogues of natural aminoglycosides has been developed. Central to the method is the utilization of septanosyl fluorides as glycosyl donors in facile and selective glycosylation reactions. The septanosyl fluorides proved to be the best choice for the glycosylations because of their accessibility and the scope of aglycones that they could glycosylate. Moreover, a high degree of stereoselectivity was observed in the glycosylations, exclusively giving 1,2-trans-glycosides. 2-Amino septanosyl fluorides were prepared from D-glucose, D-galactose, and D-mannose. Other routes to the septanosyl glyconjugates, especially with regard to alternate donor types, were systematically investigated. Since routes to the individual donor types were being explored, factors that exert a controlling influence on the acid-mediated cyclization of 1,6-hydroxy-aldehydes were determined. The newly prepared 2-amino septanosyl glycoconjugates illustrate the scope of the reaction and how it may be utilized for the preparation of other ring-expanded analogues of glycosylated natural products.     

Glycosylations with a septanosyl fluoride donor lacking a C2 protecting group

Septanosyl fluorides, prepared from protected pyranoses, were used as donors in glycosylation reactions. The fluorides were synthesized by the addition of vinyl Grignard to the pyranoses followed by ozonolysis and then DAST-mediated fluorination. Activation in the presence of nucleophiles then provided the product glycosides. High α-stereoselectivity was observed for glycosylations using a donor that had a free C2 hydroxyl group; a model where the hydroxyl group participates to guide the stereochemical outcome is proposed.     

Deformylation of indole and azaindole-3-carboxaldehydes using anthranilamide and solid acid heterogeneous catalyst via quinazolinone intermediate

The deformylation of indole and azaindole-3-carboxaldehydes was achieved in the presence of anthranilamide and a solid acid heterogeneous catalyst under reflux conditions in 25–90% yield. The reaction proceeds via quinazolinone intermediate, which undergoes acid catalyzed cleavage to form deformylated product.     

Dual-deposition rates in colloid filtration caused by coupled heterogeneities in a colloidal population

Colloidal deposition from an aqueous suspension, during its flow through saturated porous media, is of significance in many natural and man-made processes which lead to water purification. Colloid filtration theory (CFT), which was used to predict removal of homogeneous colloids, in the above systems, is based on a distance-invariant deposition rate. However, many authors over the past decade have reported data which suggest that more than one deposition rate is demonstrated by colloids naturally occurring in the environment on apparently homogeneous media. The observation of two or more deposition rates has been attributed to two modes of deposition as well to the possibility of heterogeneity in the colloidal population, in the recent literature. In this paper, we first examine the variation of liquid-phase concentration C(x) with distance, and find that only two distinct deposition rates are demonstrated by the data under multiple conditions. Since heterogeneity in the colloidal population is expected to produce continuous property variations and hence multiple deposition rates, the appearance of the above dual-deposition behavior is probed further. Depth-wise zeta-potential and particle-size-distribution data reveal that there is a coupling of favorable properties (larger size with positive surface charge) in a section of the population along with a coupling of unfavorable properties in the rest. The above coupling is then confirmed by independent separation experiments. This paper experimentally demonstrates how coupling of two types of heterogeneities in a colloidal population can lead to the appearance of dual-deposition rates while recognizing that the above may be one of the many possible causes for the appearance of dual-deposition rates.