Characterization of a nylon 6/poly(methyl acrylate) copolymer produced by radiation grafting

Acrylic acid has been grafted onto nylon 6 by the mutual γ-irradiation technique. Methods are described for removing poly(acrylic acid) homopolymer and ungrfted nylon, the latter involving intermediate conversion to the calcium ionomer. The pure graft copolymer in its methylated form, viz., nylon 6/poly(methyl acrylate), NY/PMA, was characterized by light scattering in mixed solvents to yield the true molecular weight (3.2 × 10⁶) as well as the molecular weights M_PMA(domain) and M_NY(domain) of the PMA and NY portions, respectively. The molecular weight M_PMA of the grafts was measured after hydrolysis of the backbone, and the molecular weight M_NY of the backbone was determined via a previously devised indirect procedure. Comparisons of M_PMA(domain) with M_PMA and of M_NY(domain) with M_NY gave ? 7 nylon chains and ? 17 poly(methyl acrylate) chains per copolymer molecule. Chain transfer and bimolecular terminatin during grafting are proposed as probable contributory factors to the branched structure of the copolymer.     

Influence of Sulfur for Oxygen Substitution in the Solvolytic Reactions of Chloroformate Esters and Related Compounds

The replacement of oxygen within a chloroformate ester (ROCOCl) by sulfur can lead to a chlorothioformate (RSCOCl), a chlorothionoformate (ROCSCl), or a chlorodithioformate (RSCSCl). Phenyl chloroformate (PhOCOCl) reacts over the full range of solvents usually included in Grunwald-Winstein equation studies of solvolysis by an addition-elimination (A-E) pathway. At the other extreme, phenyl chlorodithioformate (PhSCSCl) reacts across the range by an ionization pathway. The phenyl chlorothioformate (PhSCOCl) and phenyl chlorothionoformate (PhOCSCl) react at remarkably similar rates in a given solvent and there is a dichotomy of behavior with the A-E pathway favored in solvents such as ethanol-water and the ionization mechanism favored in aqueous solvents rich in fluoroalcohol. Alkyl esters behave similarly but with increased tendency to ionization as the alkyl group goes from 1° to 2° to 3°. N,N-Disubstituted carbamoyl halides favor the ionization pathway as do also the considerably faster reacting thiocarbamoyl chlorides. The tendency towards ionization increases as, within the three contributing structures of the resonance hybrid for the formed cation, the atoms carrying positive charge (other than the central carbon) change from oxygen to sulfur to nitrogen, consistent with the relative stabilities of species with positive charge on these atoms.     

Rigid‐Rod Polymers: Synthesis,Processing, Simulation,Structure, and Properties

Synthesis, structure, and properties of rigid‐rod polymers with special emphasis on poly(p‐phenylene benzobisoxazole) (PBO) and poly(p‐phenylene benzobisthiazole) (PBZT) have been reviewed. Recent studies on chemical modifications and molecular simulations have also been given. After nearly 20 years of research and development, PBO fiber was commercialized in the late 1990s. However, due to processing difficulties, the concept of the so called molecular composites has not been successful. Development of the high compressive strength M5 and dihydroxy‐PBI fibers clearly suggest that there is potential for further developing properties of this class of materials. Opto‐electronic properties have also been reviewed.

Synthesis of PBZT.     

Mechanistic Studies of the Solvolyses of Carbamoyl Chlorides and Related Reactions

Carbamoyl chlorides are important intermediates, both in the research laboratory and in industrial scale syntheses. The most studied and used are the disubstituted derivatives, incorporating either aryl or alkyl groups (Ar₂NCOCl or R₂NCOCl). Sometimes, the groups are tied back to give a ring and piperidino- and morpholino-derivatives are commonly encountered. Some studies have been made with two different groups attached. Solvolyses tend to occur at the carbonyl carbon, with replacement of the chloride ion. Studies of both rate and products are reviewed and the solvolysis reactions are usually S_N1, although addition of an amine leads to a superimposable bimolecular component. Many of the studies under solvolytic conditions include the application of the extended Grunwald–Winstein equation. The monosubstituted derivatives (ArNHCOCl or RNHCOCl) are less studied. They are readily prepared by the addition of HCl to an isocyanate. In acetonitrile, they decompose to set up and reach equilibrium with the isocyanate (ArNCO or RNCO) and HCl. Considering that the structurally related formyl chloride (HOCOCl) is highly unstable (with formation of HCl + CO₂), the unsubstituted carbamoyl chloride (H₂NCOCl) is remarkably stable. Recommended synthetic procedures require it to survive reaction temperatures in the 300–400 °C range. There has been very little study of its reactions.     

Ontology-driven hypothesis generation to explain anomalous patient responses to treatment

Within the medical domain there are clear expectations as to how a patient should respond to treatments administered. When these responses are not observed it can be challenging for clinicians to understand the anomalous responses. The work reported here describes a tool which can detect anomalous patient responses to treatment and further suggest hypotheses to explain the anomaly. In order to develop this tool, we have undertaken a study to determine how Intensive Care Unit (ICU) clinicians identify anomalous patient responses; we then asked further clinicians to provide potential explanations for such anomalies. The high level reasoning deployed by the clinicians has been captured and generalised to form the procedural component of the ontology-driven tool. An evaluation has shown that the tool successfully reproduced the clinician’s hypotheses in the majority of cases. Finally, the paper concludes by describing planned extensions to this work.     

一种有约束矩形排样问题的求解算法

对属于NP完全问题的有约束矩形排样问题，国内外多采用计算复杂度较小、时间较快、便于控制问题约束条件的启发式方法.分析了启发式排料算法影响优化程度的原因，提出利用回溯寻求优化零件组合的混合启发式策略，并利用排样过程中产生的小剩余区域划分与合并的方法和现有的矩形排样启发式算法相比，说明该方法可以更大地提高板材的利用率.     

Laminar flow through unconsolidated packed beds of spherical and non-spherical material

This paper presents a revised form of the Kozeny equation for laminar fluid flow through packed beds in terms of particle shape factor and surface mean diameter, rather than specific surface. The equation is based upon a model of pore formation which takes into account the interlocking of irregular particles. It is concluded that for comparative purposes the ‘effective’ specific surface is a quantity which can be derived exactly from permeability and porosity measurement. The effective specific surface affords a ready means of control in comparing one packing with another, provided that a standard, conventional method is adopted for the assessment of surface mean diameter.     

Anionic functional initiators. 1: 3-dimethylaminopropyllithium as an initiator for the synthesis of Bi- and difunctional polybutadienes

Methods are described whereby a series of novel bi- and difunctional (telechelic) high 1,4-microstructure polybutadienes are prepared by use of an anionic functional initiator. This initiator, 3-dimethylaminopropyllithium, has been extensively investigated and methods for its preparation and use in non-polar solvents are described. When utilised in such non-polar solvents the polybutadienes produced are uniquely functionalised, possessing a high 1,4-structure and a low glass transition temperature. Evidence is presented to demonstrate that these reactions are true ‘living’ polymerisations and that quantitative functional termination reactions may be used to yield a wide range of multi-, bi- or difunctional polymers.     

Assessing the sustainability of the UK society using thermodynamic concepts: Part 1

This paper provides a concise overview of the influence of human activity within the UK society on resource consumption and the subsequent effects on the environment. The concept of the Multi Scale Integrated Analysis of Societal Metabolism (MSIASM) is applied in order to elucidate the evolution of the UK economy for the period between 1981 and 2004. Our findings highlight the transition to a service-based economy and the disproportionate increase of energy demand when compared to the overall population increase. Emergy synthesis is applied in order to understand the production and consumption patterns and the environmental support required to sustain human activity within the UK for the year 2004. Generally speaking the UK society greatly benefits from its significant natural resources with 44.3% of the total emergy used coming from home sources and 29.1% from locally renewable sources. Interestingly enough, despite its significant natural resources, the UK economy, seems to be a net emergy importer by 638.5 × 10²¹ seJ. Furthermore, the current economic activity is believed to have a significant impact in the environment despite the relatively low environmental load ratio of 2.44.