Anomalous behavior of thermosetting systems after cure vs. chemical conversion: A normalized conversion–temperature–property diagram

Isothermal properties of thermosetting materials after cure, such as density and modulus, pass through maximum and minimum values with increasing chemical conversion. In this report observed decreases in modulus and density at isothermal temperatures below the glass-transition temperature, T_g, are termed “anomalous.” Four diepoxide (diglycidyl ether of bisphenol A) and tetrafunctional diamine (trimethylene glycol di-p-aminobenzoate) high T_g thermosetting systems with different ratios of amine to epoxy were investigated for the purpose of analyzing the evolution of the isothermal properties with increasing conversion. The density, T_g, and modulus of the materials with increasing conversion were measured by a combination of dilatometric, differential scanning calorimetry, and torsional braid analysis techniques. The results are presented in the form of conversion–temperature–property (T_gTP) diagrams with modulus and density as the properties. T_g is used as a direct measure of conversion based on the one-to-one relationship between T_g and conversion. The property-conversion behavior of the systems with different ratios of amine to epoxy show similar behavior if T_g is used as the measure of conversion and the data are normalized with respect to T_g at a conversion corresponding to the lower limit of the conversion range at which a maximum in the isothermal modulus occurs. The conversion corresponding to molecular gelation, _gelT_g, correlates with the lower limit of the conversion range at which the maximum in isothermal modulus occurs; _gelT_g also marks a change in the behavior of the sub-T_g mechanical relaxations vs. conversion. The conversion corresponding to the maximum in isothermal modulus vs. conversion correlates with the conversion corresponding to the maximum in isothermal density vs. conversion. © 1995 John Wiley & Sons, Inc.     

Effects of sulfate ions and slightly acidic pH conditions on Cr(VI) adsorption onto silica gelatin composite

The feasibility of utilizing CTAB–silica gelatin composite (C-SGC) to remove hexavalent chromium from aqueous solutions under different conditions was investigated. Removal of chromate was assessed through evaluation of the adsorption kinetics of chromate ions on the composite under equilibrium conditions in the presence of sulfate ions and at a slightly acidic pH condition (pH 5.8). Adsorption competition tests in the presence of sulfate ions showed that Cr(VI) was still effectively adsorbed from aqueous solution regardless of the presence of the competing anions. In fact, the adsorption kinetics performed at different initial chromate concentrations were unaffected by the presence of 100 mg L^?1 sulfate ions (pH 7.5). The equilibrium adsorption data were fitted by Freundlich adsorption isotherms which confirmed that the adsorption efficiency of chromium on the CTAB–silica gelatin composite was unchanged in the presence of sulfate ions. Further, the adsorption process was shown to be pH dependent and more efficient at slightly acidic pH (5.8). These findings demonstrated a high specificity of the CTAB–silica gelatin composite for chromium, and highlight the possibility of using this matrix for efficient removal of chromium from industrial wastewater without the need to eliminate contaminant sulfate ions.     

Experimental techniques using optically enabled ring oscillators

We present a method for characterizing transceiver performance in parallel optical data links. By establishing a bidirectional link between two optically enabled chips, the conditions for a ring oscillator are made possible. We propose this technique as a means of measuring the sensitivity of transceiver latency to controlled variables such as temperature, optical output power, supply voltage, and device misalignment. This method is noninvasive and independent of the packaging, circuit topology, and optical medium used. The technique is demonstrated experimentally, and results are compared with a simulation.     

Organometallic Pt(II) containing polymer as silver protection against sulfide tarnishing

In this work, the use of a film of an organometallic polymer, namely Pt‐DEBP, has been tested for the selective capture of sulfides with the aim of protecting silver object. Ag foils were exposed to different environmental conditions in the presence of Pt‐DEBP films. Scanning electron microscopy, energy dispersive spectrometry, and colorimetric studies allowed to assess that the polymeric layer selectively captures H₂S, preventing the tarnishing of the silver substrate over a period at least of 2 months, without any manipulation of the sample. This approach open new perspectives for the prevention of aging effects on silver objects of artistic interest, for which cleaning or coating procedures should be avoid. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Characterization of Crude Oils and Their Fouling Deposits Using a Batch Stirred Cell System

A small (1 L) batch stirred cell system has been developed to study crude oil fouling at surface temperatures up to 400°C and pressures up to 30 bar. Fouling resistance–time data are obtained from experiments in which the principal operating variables are surface shear stress, surface temperature, heat flux, and crude oil type. The oils and deposits are characterized and correlated with the experimental heat transfer fouling data to understand better the effects of process conditions such as surface temperature and surface shear stress on the fouling process. Deposits are subjected to a range of qualitative and quantitative analyses in order to gain a better insight into the crude oil fouling phenomenon. Thermal data that can be obtained relatively quickly from the batch cell provide fouling rates, Arrhenius plots, and apparent activation energies as a function of process variables. The experimental system, supported by computational fluid dynamics (CFD) studies, allows fouling threshold conditions of surface temperature and shear stress to be identified relatively quickly in the laboratory. The data also contribute to existing knowledge about the compensation plot.     

Detoxification of woody hydrolyzates with activated carbon for bioconversion to ethanol by the thermophilic anaerobic bacterium Thermoanaerobacterium saccharolyticum

Autohydrolysis is a simple, green method of recovering sugars from biomass, using only hot water. One potential drawback is that byproducts are formed during the autohydrolysis process that could interfere with subsequent hydrolysis and fermentation to ethanol. In the present work, autohydrolysis prehydrolyzate from mixed hardwood chips was detoxified with activated carbon and the removal efficiency of byproducts as well as the loss of sugars determined. The resulting detoxified prehydrolyzate was evaluated for the fermentation to ethanol with a thermophilic anaerobic bacterium. Activated carbon at a 2.5 wt % level on the prehydrolyzate was able to remove 42% of formic acid, 14% of acetic acid, 96% of hydroxymethylfurfural (HMF) and 93% of the furfural. However, 8.9% of sugars were also removed. The removal of HMF and furfural follow expected adsorption isotherms but formic acid, acetic acid, and sugars did not. Autohydrolysis prehydrolyzates from mixed hardwood detoxified with activated carbon can be fermented with Thermoanaerobacterium saccharolyticum strain MO1442 with an essentially 100% yield. T. saccharolyticum strain MO1442 is able to metabolize the glucose, xylose, and arabinose in the hydrolyzate. The results showed the detoxification process with activated carbon improved the ethanol yields by the removal of toxic compounds, mainly HMF and furfural, with moderate loss of fermentable sugars.     

Application of parallel forward-error correction in two-dimensional optical-data links

We propose the use of on-chip parallel forward-error correction (FEC) to improve the performance of two-dimensional (2-D) optical-data links (2-D-ODLs). Using an optical system model that describes a 2-D-ODL, we show the merits of using the Golay code as an FEC scheme to enable the reliable operation of 2-D-ODLs in the presence of erasures [e.g., a dead laser or photodetector, a dark fiber, an alignment problem, or a fault on the application-specific integrated circuit (ASIC)]. In addition, we study the impact of using on-chip FEC in 2-D-ODLs and show that FEC can reduce the launched optical power requirements, reduce on-chip power consumption, and relax the throughput requirements of the optical system.     

Vector Quantization-Based Motion Field Segmentation under the Entropy Criterion

This paper proposes a segmentation of block-based motion fields under the constraint of the entropy criterion. The segmentation is performed by a vector quantization technique which associates the segmentation pattern to an element of a codebook. Optimization of the bit rate as a trade-off between motion and segmentation on the one hand and prediction error on the other hand is addressed. An estimation of the amount of information to code the displaced frame difference is derived, making it possible to control the segmentation process. Simulation results show the efficiency of the segmentation method combined with the entropy criterion in a video coding scheme.     

Analysis of treatment failure in patients with minimally differentiated acute myeloid leukemia (AML-M0)

Reports of treatment of patients with minimally differentiated acute myeloid leukemia (AML-M0) are limited, heterogeneous, and controversial. We verified the prognosis of this subtype by analyzing the results of 189 consecutive patients with de novo AML. Fifteen cases fitting the criteria of AML-M0 were identified. No clinical features distinguished them from other patients with AML. The median age was 61 years (range 27 to 70), with a leukocyte count ranging from 0.6 to 185 x 10(9)/L. In all cases the leukemic cells expressed CD34 and reacted with at least one of the antibodies to early myeloid antigens, ie, CD13, CD33, or myeloperoxidase. Immunophenotypic analysis also showed positivity for CD7 in seven samples and the multidrug-resistance P-glycoprotein (P-170) in six. Cytogenetic analysis was abnormal in 12 of the 13 patients in whom an adequate number of mitoses could be evaluated. No single abnormality prevailed, the most common findings being trisomy 8 (three cases) and aberrations of chromosome 7 (two cases). Antileukemic treatment differed according to age, but for remission induction, all patients received a combination of cytosine arabinoside and an anthracycline or mitoxantrone. The prognosis of patients with AML-M0 was remarkably poor as compared with the other French-American-British subtypes. Whereas the overall rate of complete remission (CR) was 58% with a median survival of 63 weeks, only 6 of the 15 patients with AML-M0 achieved a CR, and the median survival of this group was 16 weeks (range 3 to 39). The major determinant of treatment failure was unresponsiveness to chemotherapy, as only one patient died of infection during the hypoplastic phase. The CR duration of responders was short, ranging from 3 to 22 weeks, and no second remissions were observed. We conclude that conventional combination chemotherapy yields disappointing results in AML-M0. The reason for this may be the convergence of various unfavorable prognostic factors, such as (1) the high incidence of cytogenetic abnormalities; (2) the lack of differentiation features and the expression of immaturity markers such as CD34 and CD7; and (3) the frequent expression of P-170. Nonconventional therapeutic approaches should be developed to alter the prognosis of this form of leukemia.