On finding optimal and near-optimal lineal spanning trees

The search for good lineal, or depth-first, spanning trees is an important aspect in the implementation of a wide assortment of graph algorithms. We consider the complexity of findingoptimal lineal spanning trees under various notions of optimality. In particular, we show that several natural problems, such as constructing a shortest or a tallest lineal tree, are NP-hard. We also address the issue of polynomial-time, near-optimization strategies for these difficult problems, showing that efficient absolute approximation algorithms cannot exist unlessP = NP.This author's research was supported in part by the Sandia University Research Program and by the National Science Foundation under Grant M IP-8603879.This author's research was supported in part by the National Science Foundation under Grants ECS-8403859 and MIP-8603879.     

Hutchinsonianism and the Newtonian Enlightenment

Abstract. Historians of science have labeled followers of the 18th cosmologist John Hutchinson (1674– 1737) as anti‐Newtonian. While Hutchinson was clearly anti‐Newtonian, this was not the case with later followers like George Horne and William Jones. Horne and Jones sought a rapprochement between Newton and Hutchinson; in their hands, interpretations of Newton's works were refashioned to support Hutchinson's biblically based cosmos and Trinitarian natural philosophy. Newton's thought could be used by conservative Anglican Churchmen to battle religious heterodoxy. This raises problems for traditional Enlightenment historiography which views Newtonianism as a set of ideas which supported and reinforced emerging modern forms of political and religious thought.     

On finding optimal and near-optimal lineal spanning trees

The search for good lineal, or depth-first, spanning trees is an important aspect in the implementation of a wide assortment of graph algorithms. We consider the complexity of findingoptimal lineal spanning trees under various notions of optimality. In particular, we show that several natural problems, such as constructing a shortest or a tallest lineal tree, are NP-hard. We also address the issue of polynomial-time, near-optimization strategies for these difficult problems, showing that efficient absolute approximation algorithms cannot exist unlessP = NP.     

A discussion of the methods for comparing the relative effectiveness of phosphate fertilizers varying in solubility

Because various phosphate (P) fertilizers differ widely in their solubility, it is commonly observed that crop response to P fertilizers varies under the same soil and crop conditions. Furthermore, a major problem encountered in the methods for determining the relative effectiveness (RE) of water-insoluble P fertilizer (e.g., phosphate rock) with respect to water-soluble P fertilizers, e.g., single superphosphate (SSP) and triple superphosphate (TSP), is that their growth response curves are usually nonlinear and often do not share a common maximum yield. In this paper, we review and discuss the advantages and disadvantages of the three most commonly used methods for calculating the RE of phosphate rock with respect to TSP (or SSP). The three methods are vertical comparison, horizontal (substitution rate) comparison, and linear-response comparison.     

Synthesis and Polymerization of Cationic bis(cyclopentadienyliron)arene Complexes Containing Arylazo Dyes

The synthesis of the title complexes was achieved via the reaction of -p-dichlorobenzene- -cyclopentadienyliron cations with 4,4′-bis(4-hydroxyphenyl)valeric acid to produce the diiron complexes which were then reacted with a number of arylazo dyes to give cationic bis(cyclopentadienyliron)arene complexes containing the arylazo dyes. These iron-containing monomers were subsequently polymerized via nucleophilic aromatic substitution using 1,8-octanedithiol, 4,4′-thiobisbenzenethiol, or bisphenol A to produce the desired coloured cationic organoiron polymers. The weight – average molecular weights were estimated to range from 11,800 to 31,600. UV–vis studies conducted in dimethylformamide (DMF) showed that the metallated polymers exhibited of 412–491 nm. Addition of HCl to the polymer solution caused a bathochromic shift into the range of 515–530 nm. Thermogravimetric analysis (TGA) revealed that the iron moieties were cleaved between 205 and 248 °C while the polyether/thioether backbone degraded between 380 and 613 °C. Differential scanning calorimetry (DSC) showed that the polymers exhibited glass transition temperatures (Tg) ranging from 106 to 184°C.This paper is dedicated to Professor Richard J. Puddephatt in recognition of his outstanding contribution to the field of metal-containing polymers.     

Approximation for scheduling on uniform nonsimultaneous parallel machines

We consider the problem of scheduling on uniform machines which may not start processing at the same time with the purpose of minimizing the maximum completion time. We propose using a variant of the MULTIFIT algorithm, LMULTIFIT, which generates schedules which end within 1.382 times the optimal maximum completion time for the general problem, and within \(\sqrt{6}/2\) times the optimal maximum completion time for problem instances with two machines. Both developments represent improvements over previous results. We prove that LMULTIFIT worst-case bounds for scheduling on simultaneous uniform machines are also LMULTIFIT worst-case approximation bounds for scheduling on nonsimultaneous uniform machines and show that worst-case approximation bounds of MULTIFIT variants for simultaneous uniform machines from previous literature also apply to LMULTIFIT. We also comment on how a PTAS for scheduling on a constant number of uniform machines with fixed jobs can be used to obtain a PTAS for scheduling on a constant number of uniform nonsimultaneous parallel machines.     

The questionable promise of social media for education: connective learning and the commercial imperative

Facebook and other social media have been hailed as delivering the promise of new, socially engaged educational experiences for students in undergraduate, self‐directed, and other educational sectors. A theoretical and historical analysis of these media in the light of earlier media transformations, however, helps to situate and qualify this promise. Specifically, the analysis of dominant social media presented here questions whether social media platforms satisfy a crucial component of learning – fostering the capacity for debate and disagreement. By using the analytical frame of media theorist Raymond Williams, with its emphasis on the influence of advertising in the content and form of television, we weigh the conditions of dominant social networking sites as constraints for debate and therefore learning. Accordingly, we propose an update to Williams' erudite work that is in keeping with our findings. Williams' critique focuses on the structural characteristics of sequence, rhythm, and flow of television as a cultural form. Our critique proposes the terms information design, architecture, and above all algorithm, as structural characteristics that similarly apply to the related but contemporary cultural form of social networking services. Illustrating the ongoing salience of media theory and history for research in e‐learning, the article updates Williams' work while leveraging it in a critical discussion of the suitability of commercial social media for education.     

Inhaled PYY(3–36) dry-powder formulation for appetite suppression

Objective: Peptide YY3–36 [PYY(3–36)] has shown efficacy in appetite suppression when dosed by injection modalities (intraperitoneal (IP)/subcutaneous). Transitioning to needle-free delivery, towards inhalation, often utilizes systemic pharmacokinetics as a key endpoint to compare different delivery methods and doses. Systemic pharmacokinetics were evaluated for PYY3–36 when delivered by IP, subcutaneous, and inhalation, the systemic pharmacokinetics were then used to select doses in an appetite suppression pharmacodynamic study.

Methods: Dry-powder formulations were manufactured by spray drying and delivered to mice via nose only inhalation. The systemic plasma, lung tissue, and bronchoalveolar lavage fluid pharmacokinetics of different inhalation doses of PYY(3–36) were compared to IP and subcutaneous efficacious doses. Based on these pharmacokinetic data, inhalation doses of 70:30 PYY(3–36):Dextran T10 were evaluated in a mouse model of appetite suppression and compared to IP and subcutaneous data.

Results: Inhalation pharmacokinetic studies showed that plasma exposure was similar for a 2?×?higher inhalation dose when compared to subcutaneous and IP delivery. Inhalation doses of 0.22 and 0.65?mg/kg were for efficacy studies. The results showed a dose-dependent (not dose proportional) decrease in food consumption over 4?h, which is similar to IP and subcutaneous delivery routes.

Conclusions: The pharmacokinetic and pharmacodynamics results substantiate the ability of pharmacokinetic data to inform pharmacodynamics dose selection for inhalation delivery of the peptide PYY(3–36). Additionally, engineered PYY(3–36):Dextran T10 particles delivered to the respiratory tract show promise as a non-invasive therapeutic for appetite suppression.     

Switchable Plasmonic Metasurface Utilizing the Electro-Optic Kerr Effect of a Blue Phase Liquid Crystal

A switchable metasurface composed of plasmonic split ring resonators and a polymer-stabilized liquid crystal blue phase is developed. Owing to field-induced birefringence (electro-optic Kerr effect), the state of polarization of the incident near infrared radiation changes, when a voltage is applied to the liquid crystal. Thus, different resonant modes of the split ring resonators can be addressed and the transmission spectrum changes accordingly. In comparison with other liquid crystal phases, blue phases have several advantages. For example, they are optically isotropic in the field-off state, so that no alignment layer is required. The results of the present study indicate that the advantages of these mesophases can be utilized for switchable metasurfaces.