Reactive modification and crystallization behavior of foamed poly(butylene terephthalate)

The objective of this study is to investigate the feasibility of preparing low density foams based on poly(butylene terephthalate) (PBT) through modification of its molecular structure and rheological characteristics by reactive extrusion. The scientific and/or engineering interpretation of the experimental data was based on fundamentals of extrusion, crystallization mechanisms, as well as information on reactivity and tendency toward degradation of PBT. As a preliminary study, the extrusion foaming behavior of a commercial linear semi-crystalline PBT with a chemical blowing agent (CBA) was investigated. Foam characteristics were functions of extrusion operational variables, such as die set temperature and screw speed. Gas solubility and CBA decomposition kinetics were found to be key elements for controlling and optimizing the quality of the foamed polymer. Initially, the linear PBT polymer was reactively modified using a tri-functional epoxide in a batch mixer to produce a branched structure with a higher molecular weight (MW) and a broader molecular weight distribution (MWD) as evidenced by rheological analysis. These experiments provided information on the PBT/modifier reaction kinetics. Chain branching was then carried out by single screw extrusion, where the competing degradative chain scission reaction needed to be taken into account. Applications of fundamentals of extrusion theory to the reactive extrusion process enabled the optimization of the extrusion operational conditions. The optimization led to the production of a branched polymer with viscoelastic characteristics suitable for low density extrusion foaming by injection of a physical blowing agent (PBA). The branched product made under the optimized conditions could be foamed to densities as low as 0.33 g/cc and showed high expansion ratio of 4.0 and cell structure resistant to coalescence. The possibility of overlap of the polymer crystal formation with the nucleation/growth of gaseous cells was investigated based on theoretical predictions. Slow pressure drop rate was shown to decrease cell nucleation rate. Fast crystallization rate stabilized cell morphology. The occurrence of flow induced crystallization during bubble formation was investigated, to our knowledge, for the first time. Smaller size spherulitic structures at the bubble walls of the branched PBT compared with the linear polymer, suggested longer crystal nuclei lifetime, which may indicate that the formation of the crystalline structures was affected by the bi-axial deformation occurring during bubble growth

Internet Customer Segmentation Using Web Log Data

The objective of this paper is to analyze web transaction log data that reveal customer behavior in the Internet channel, and to provide a useful online customer segmentation scheme. To achieve this, we analyze the relationship between the behavior of customers for online pet shops and revenue. We use the decision-tree method as a data-mining technique, and clustering analysis to segment customers.  We perform the study in two stages. First, we investigate the web transaction data of both the member customers and nonmember customers of a Korean online pet shop. Second, we narrow down the study focus and analyze only the member customers’ demographic data and their web transaction data. As a result, we obtain several meaningful segments based on customers’ transaction behavior and demographic characteristics. We use web log data to analyze customer transaction behavior and log-in information to analyze customer demographic characteristics. We discuss some strategic implications, for online shopping mall marketing, suggested by the acquired market segments

Optical switching of the Dirac point in graphene multilayer field-effect transistors functionalized with spiropyran

A facile method for achieving optical switching of the Dirac point and conductance in reduced graphene oxide multilayer FETs that are non-covalently functionalized with a photoresponsive spiropyran derivative is presented. The photoresponsive transition from spiropyran to merocyanine induces the reversible optical switching in graphene based FETs.close6

Tip-Enhanced Raman Scattering Imaging of Two-Dimensional Tungsten Disulfide with Optimized Tip Fabrication Process

We successfully achieve the tip-enhanced nano Raman scattering images of a tungsten disulfide monolayer with optimizing a fabrication method of gold nanotip by controlling the concentration of etchant in an electrochemical etching process. By applying a square-wave voltage supplied from an arbitrary waveform generator to a gold wire, which is immersed in a hydrochloric acid solution diluted with ethanol at various ratios, we find that both the conical angle and radius of curvature of the tip apex can be varied by changing the ratio of hydrochloric acid and ethanol. We also suggest a model to explain the origin of these variations in the tip shape. From the systematic study, we find an optimal condition for achieving the yield of similar to 60% with the radius of similar to 34 nm and the cone angle of similar to 35 degrees. Using representative tips fabricated under the optimal etching condition, we demonstrate the tip-enhanced Raman scattering experiment of tungsten disulfide monolayer grown by a chemical vapor deposition method with a spatial resolution of similar to 40 nm and a Raman enhancement factor of similar to 4,760. © The Author(s) 2017

A case of Creutzfeldt–Jakob disease in a patient on hemodialysis

abstractWe report an unusual case of probable Creutzfeldt–Jakob disease (CJD) in hemodialysis patient. A woman 59 years of age with a past history of hypertension and end-stage renal disease presented with a stuporous state preceded by rapidly progressive cognitive dysfunction, myoclonus, and akinetic mutism. At first, the cause of the altered mental status was assumed to be uremic or hypertensive encephalopathy combined with fever. Proper managements, however, did not improve the neurologic symptoms. Diffusion-weighted magnetic resonance imaging revealed bilaterally asymmetric high signal intensity in both basal ganglia and cerebral cortices. Electroencephalography showed diffuse generalized theta-to-delta range slow wave and intermittent medium-to-high voltage complexes with a characteristic triphasic pattern on both hemispheres. Cerebrospinal fluid assay for the 14-3-3 protein was positive and diagnostic of CJD

UKIRT Widefield Infrared Survey for Fe+

The United Kingdom Infrared Telescope (UKIRT)Widefield Infrared Survey for Fe+ (UWIFE) is a 180 deg2 imaging survey of the first Galactic quadrant (7° < l < 62° |b| <1°.5) that uses a narrow-band filter centred on the [Fe II] 1.644-μm emission line. The [Fe II] 1.644-μm emission is a good tracer of dense, shock-excited gas, and the survey will probe violent environments around stars: star-forming regions, evolved stars, and supernova remnants, among others. The UWIFE survey is designed to complement the existing UKIRTW idefield Infrared Survey for H2 (UWISH2). The survey will also complement existing broad-band surveys. The observed images have a nominal 5Ï? detection limit of 18.7 mag for point sources, with a median seeing of 0.83 arcsec. For extended sources, we estimate a surface brightness limit of 8.1 Ã? 10-20 W m-2 arcsec-2. In this paper, we present an overview and some preliminary results of this survey. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society