The Estimation of the Molecular Weight of Polytetrafluoroethylene Based on the Heat of Crystallisation. A Comment on Suwa's Equation

Summary: The influence of number‐average molecular weight ranging from 1.4 · 10⁴ to 1.2 · 10⁶ g/mol on the thermal behaviour of polytetrafluoroethylene (PTFE) has been studied. Samples have been prepared by radiation‐induced degradation of commercial PTFE. The molecular weight has been calculated using end‐group concentration determined by infrared (IR) spectroscopy and ¹⁹F solid‐state nuclear magnetic resonance (NMR) spectroscopy. Melting and crystallisation heats were investigated by differential scanning calorimetry (DSC). The results have been discussed with respect to quantitative relationships between number‐average molecular weight and heat of crystallisation of PTFE described in the literature. The molecular weight calculated from Suwa's equation, which is often used in the literature, has been found to be too low.

Concentration of end‐groups and the molecular weight of PTFE versus the irradiation dose.     

Relationship between Creativity, Imitation, and Cultural Diversity

There are both benefits and drawbacks to cultural diversity. It can lead to friction and exacerbate differences. However, as with biological diversity, cultural diversity is valuable in times of upheaval; if a previously effective solution no longer works, it is good to have alternatives available. What factors give rise to cultural diversity? This paper describes a preliminary investigation of this question using a computational model of cultural evolution. The model is composed of neural network based agents that evolve fitter ideas for actions by (1) inventing new ideas through modification of existing ones, and (2) imitating neighbors'' ideas. Numerical simulations indicate that the diversity of ideas in a population is positively correlated with both the proportion of creators to imitators in the population, and the rate at which creators create. This is the case for both minimum and peak diversity of actions over the duration of a run.     

Incorporating characteristics of human creativity into an evolutionary art algorithm

A perceived limitation of evolutionary art and design algorithms is that they rely on human intervention; the artist selects the most aesthetically pleasing variants of one generation to produce the next. This paper discusses how computer generated art and design can become more creatively human-like with respect to both process and outcome. As an example of a step in this direction, we present an algorithm that overcomes the above limitation by employing an automatic fitness function. The goal is to evolve abstract portraits of Darwin, using our 2nd generation fitness function which rewards genomes that not just produce a likeness of Darwin but exhibit certain strategies characteristic of human artists. We note that in human creativity, change is less choosing amongst randomly generated variants and more capitalizing on the associative structure of a conceptual network to hone in on a vision. We discuss how to achieve this fluidity algorithmically.

Shear‐induced shish‐kebab structures in isotactic polypropylene using acicular precipitated calcium carbonate as whisker

It has been reported in the technical literature that whiskers of rodlike single crystals can be used in order to generate shish‐kebab structures or other different lamellae morphologies during isothermal or dynamic crystallization of sheared or presheared polymer melts. The expected advantage of the changed crystalline structure is a reinforcing effect of the composite. A lot of papers reported about the application of inorganic and organic whiskers such as cellulose and chitin whiskers. This study reports on an attempt to use acicular PCC as appropriate whisker for improving mechanical properties of polypropylene. In this article special attention is given to demonstrate the effect of flow induced crystallization under varying shear conditions in order to improve the mechanical properties. The effects were demonstrated using rheology, thermal analysis, tensile testing, and transmission electron microscopy. POLYM. ENG. SCI., 54:2057–2063, 2014. © 2013 Society of Plastics Engineers     

Managing computer networks using peer-to-peer technologies

Peer-to-peer systems and network management are usually related to each other because the traffic loads of P2P systems have to be controlled to avoid regular network services becoming unavailable due to network congestion. In this context, from a network operation point of view, P2P systems often mean problems. In this article we take a different perspective and look at P2P technologies as an alternative to improve current network management solutions. We introduce an approach where P2P networks are used as flexible interdomain distributed management systems able to provide facilities often absent in traditional management systems. We present three examples of P2P-based network management: how managed network views can be shared in a P2P network, how P2P-based application layer routing can improve connectivity between management entities, and how groups of peers can be used to process management tasks in a balanced way. Our main goal is to show that P2P technologies are a feasible tool for network management, and thus motivate further investigations on the subject.     

Value Stream Mapping: a study about the problems and challenges found in the literature from the past 15 years about application of Lean tools

Value stream mapping (VSM) is an important tool of the lean approach and is used to identify value-adding activities and those considered wasteful of materials and the flow of information and people. However, when not applied correctly, VSM can complicate the identification of waste, lead to misinterpretations and assessment mistakes, and undermine the implementation of future improvements. The purpose of this paper is to investigate the main difficulties and limitations encountered during the construction of current state maps, analysis of the associated causes, and pointing out of guidelines to facilitate the use of VSM to map processes. To do so, a search and evaluation of papers in journals, conferences, theses, and dissertations was conducted, and the articles were categorized according to the field of application (factory floor, supply chain, product development and services) and approach (theoretical or practical). In conclusion, this paper criticizes some ways that VSM has been used, observing that important constraints created by its application must be considered and that when used incorrectly, the tool can lead to mistakes that can cause problems instead of benefits. Considering the problems identified, the paper suggests future works for improving the use of VSM for mapping processes.     

A longitudinal study of phonological processing skills in children learning to read in a second language.

English-speaking children (N?=?122) in French immersion classes participated in a 1-year longitudinal study of the relation between phonological awareness and reading achievement in both languages. Participants were administered measures of word decoding and of phonological awareness in French and in English as well as measures of cognitive ability, speeded naming, and pseudoword repetition in English only. The relation of phonological awareness in French to reading achievement in each of the languages was equivalent to that in English. These relations remained significant after partialing out the influences of speeded naming and pseudoword repetition. Phonological awareness in both languages was specifically associated with 1-year increments in decoding skill in French. These findings support the transfer of phonological awareness skills across alphabetic languages. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Polymers containing formamidine groups

Summary New aromatic polymers containing formamidine groups were prepared by high temperature solution polycondensation of triethyl orthoformate with various aromatic diamines. The resulting polyformamidines were characterized by elemental analysis, IR' and ¹H NMR spectroscopy, viscosity measurements, thermogravimetry, DSC- and WAXS measurements. With few exceptions aromatic polyformamidines show excellent solubility in polar solvents and strong acids, but they were gradually decomposed in extended contact with moisture. Polyformamidines containing rigid para structures are well crystallizing materials, which was proved by WAXS investigations. Glass transition temperatures in the range of 62 – 163°C were observed for semicrystalline or amorphous polymers. All aromatic polyformamidines are thermally stable in nitrogen up to 300°C.     

Speaker-external versus speaker-internal forces on utterance form: Do cognitive demands override threats to referential success?

To what extent do speaker-external communicative pressures versus speaker-internal cognitive pressures affect utterance form? Four experiments measured speakers' references to privately known (i.e., privileged) objects when naming mutually known (i.e., common ground) objects. Although speaker-external communicative pressures demanded that speakers avoid references to privileged objects, 2 experiments showed that speakers often ignored this demand when it coexisted with a speaker-internal pressure to attend to those privileged objects. The authors hypothesize that this was due to increased salience of privileged objects (a speaker-internal pressure). Experiment 3 showed that directly boosting the salience of privileged objects increased the likelihood that speakers will inappropriately refer to those objects. Experiment 4 showed that the salience-sensitive mechanism in Experiments 1 and 2 is likely related to the mechanism causing such references in Experiment 3. Thus, the language production system is especially sensitive to cognitive pressures even when communicative harm results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Biologically Inspired and Magnetically Recoverable Copper Porphyrinic Catalysts: A Greener Approach for Oxidation of Hydrocarbons with Molecular Oxygen

An efficient synthetic method for magnetically recoverable hybrid copper porphyrinic nanomaterials is reported. These functionalized magnetic materials prove to be efficient bioinspired oxidation catalysts of olefins and thiols, using molecular oxygen as oxidant, in total absence of reductants and solvents, with the highest TON (turnover number) yet achieved for this reaction (≈200 000). A comparative study between homogeneous and heterogeneous oxidation of cyclohexene is discussed, revealing the heterogeneous system to be the most promising concerning stability and reusability of the catalysts. The full characterization of the magnetic hybrid porphyrinic nanomaterials, by transmission electron microscopy, flame atomic absorption spectrometry, thermogravimetry, N₂ sorption, and infrared spectroscopy, is also described.