Rheological and mechanical performance of ethyl‐vinyl acetate/poly(vinyl chloride) formulations

A range of powdered ethyl‐vinyl acetate (EVA) copolymers and poly(vinyl chloride) (PVC) formulations were compounded at PVC:EVA ratios of 100:0, 60:40, 50:50, 40:60, and 0:100. Two grades of EVA with 20% and 27% of vinyl acetate (VAc) (EVA I and EVA II) and two grades of PVC with K values of 56 and 71 (PVC I and PVC II) were used in the investigation. Mechanical analysis was performed on injection molded samples of these blends, and the results showed that the tensile and flexural moduli decreased significantly with increasing EVA concentration. Rheological analysis was performed by using dual capillary rheometry, and the results showed only slight changes in shear viscosity with increasing EVA content, even at lower shear rates. Dynamic mechanical thermal analysis showed partial miscib lity of the PVC and EVA over the range of concentrations studied.     

Analyses of lipids and oxidation products by partition chromatography: Hydroxy fatty acids and esters

A liquid-partition chromatographic procedure was used to separate hydroxy fatty acids, their methyl esters, and reduced fatty ester hydroperoxides. Mixtures of methyl stearate, mono- and dihydroxystearate, and mixtures of the corresponding free fatty acids were easily separated. Chromatographic determinations for ricinoleate in castor oils compared favorably with the chemical and infrared analyses. The chromatographic procedure was used to separate hydroxy fatty acids inDimorphotheca andStrophanthus seed oils. The methyl ester of dimorphecolic acid, the principal hydroxy fatty ester ofDimorphotheca oil, behaved like reduced methyl linoleate hydroperoxide and showed a polarity intermediate between methyl 12-hydroxystearate and methyl 9,10-dihydroxystearate. The 9-hydroxy-12-octadecenoic ester ofStrophanthus oil had a larger retention volume than methyl ous hydroxy fatty esters isolated chromatographically. The diene content of the reduced hydroperoxides agrees well with values reported in the literature (1,5,16). The diene content of the chromatographed methyl dimorphecolate is higher than reported by Smithet al. (20) for their preparations but agrees well with the value reported by Chipault and Hawkins (6) for puretrans-trans conjugated methyl linoleate. The extinction coefficient of methyl 12-hydroxystearate at 2.8 μ is higher than that reported for ricinoleate and the absorption band is much sharper. Because of these two conditions no association of the hydroxyl groups is indicated. These results also confirm the purity of the hydroxy fatty esters obtained by LPC. This method has been a valuable adjunct to the study of various oxygen-containing fatty acid and esters and was used to characterize the hydroxy esters obtained from the hydrogenation of methyl linolenate hydroperoxides (9). This work offers a basis for the development of analytical methods to determine the hydroxy and other polar acid content of fatty glycerides and their derivatives.     

Experiences from using heat integration software to determine retrofit opportunities within a refinery process

Heat integration techniques can be used to optimize the energy requirement for both new and retrofit plant designs. Software tools for identifying retrofit options are becoming available. This paper reports our experiences from using heat exchanger network (HEN) optimization software for a retrofit case study of an oil refinery process. The HEN optimization software was used to automate the search for the most beneficial retrofit designs following the twostage process proposed by Asante and Zhu. The software provided three potential retrofit designs. Results from this analysis were used as the basis of a rigorous mass and energy balance simulation of the plant. The simulation corroborated the energy savings, but there were some important differences. The simulation required 20% more heat exchange area. Furthermore, the retrofit design involving one topology change was shown to be less economic than an alternative design. These differences are discussed and a revised methodology is proposed.     

Involving the user Through Library 2.0

Libraries, as we know them today, can be defined by the term Library 1.0. This defines the way resources are kept on shelves or at a computer behind a login. These resources can be taken from a shelf, checked out by the library staff, taken home for a certain length of time and absorbed, and then returned to the library for someone else to avail of. Library 1.0 is a one-directional service that takes people to the information they require. Library 2.0 – or L2 as it is now more commonly addressed as – aims to take the information to the people by bringing the library service to the Internet and getting the users more involved by encouraging feedback participation. This paper presents an overview of Library 2.0 and introduces web 2.0 concepts.     

Chemical modification of group IV graphene analogs

Mono-elemental two-dimensional (2D) crystals (graphene, silicene, germanene, stanene, and so on), termed 2D-Xenes, have been brought to the forefront of scientific research. The stability and electronic properties of 2D-Xenes are main challenges in developing practical devices. Therefore, in this review, we focus on 2D free-standing group-IV graphene analogs (graphene quantum dots, silicane, and germanane) and the functionalization of these sheets with organic moieties, which could be handled under ambient conditions. We highlight the present results and future opportunities, functions and applications, and novel device concepts.     

Impact of arteriovenous fistula cannulation on the quality of dialysis

Introduction: Adequate hemodialysis directly improves health. Puncturing an arteriovenous fistula (AVF) and the amount of blood recirculation greatly affect the quality of dialysis. Few studies have assessed the method to cannulate a fistula and its influence on efficiency of hemodialysis. Methods: This prospective pilot study included 14 patients with end‐stage renal failure receiving regular intermittent hemodialysis. Patients received three consecutive treatments with both needles directed upstream then three consecutive treatments with the venous needle directed upstream and the arterial needle directed downstream. With both techniques, the distance between the needles was kept constant at 2.5 cm. Recirculation rate and Kt/V ratio were measured during each treatment using thermodilution and a diascan Fresenius generator. Findings: The 14 patients received 84 hemodialysis sessions: i.e., 8 (57.1%) males and 6 (42.8%) females, mean age 62.3 ± 15.57 years. Results showed that mean recirculation rates and Kt/V did not significantly differ between the two techniques. Discussion: Because no significant difference was found between the two techniques, the direction of insertion of needles should be decided upon on a case‐by‐case basis depending on the anatomy of the AVF and the feasibility of the puncture.     

Evaluation of artery visualizations for heart disease diagnosis

Heart disease is the number one killer in the United States, and finding indicators of the disease at an early stage is critical for treatment and prevention. In this paper we evaluate visualization techniques that enable the diagnosis of coronary artery disease. A key physical quantity of medical interest is endothelial shear stress (ESS). Low ESS has been associated with sites of lesion formation and rapid progression of disease in the coronary arteries. Having effective visualizations of a patient's ESS data is vital for the quick and thorough non-invasive evaluation by a cardiologist. We present a task taxonomy for hemodynamics based on a formative user study with domain experts. Based on the results of this study we developed HemoVis, an interactive visualization application for heart disease diagnosis that uses a novel 2D tree diagram representation of coronary artery trees. We present the results of a formal quantitative user study with domain experts that evaluates the effect of 2D versus 3D artery representations and of color maps on identifying regions of low ESS. We show statistically significant results demonstrating that our 2D visualizations are more accurate and efficient than 3D representations, and that a perceptually appropriate color map leads to fewer diagnostic mistakes than a rainbow color map.     

Linear-Time Recognition of Helly Circular-Arc Models and Graphs

A circular-arc model ℳ is a circle C together with a collection A\mathcal{A} of arcs of C. If A\mathcal{A} satisfies the Helly Property then ℳ is a Helly circular-arc model. A (Helly) circular-arc graph is the intersection graph of a (Helly) circular-arc model. Circular-arc graphs and their subclasses have been the object of a great deal of attention in the literature. Linear-time recognition algorithms have been described both for the general class and for some of its subclasses. However, for Helly circular-arc graphs, the best recognition algorithm is that by Gavril, whose complexity is O(n ³). In this article, we describe different characterizations for Helly circular-arc graphs, including a characterization by forbidden induced subgraphs for the class. The characterizations lead to a linear-time recognition algorithm for recognizing graphs of this class. The algorithm also produces certificates for a negative answer, by exhibiting a forbidden subgraph of it, within this same bound.