The effect of soft segment content and linker length on shape recovery and mechanical properties of laterally linked polyurethane copolymer

Lateral flexible linking of shape memory polyurethane (SMPU) by a polyethyleneglycol (PEG) linker through the allophanate linking method was studied, while adjusting the soft segment content and PEG length. The SMPU was composed of 4,4′‐methylenebis(phenylisocyanate) (MDI), poly(tetramethyleneglycol) (PTMG), 1,4‐butanediol (BD), and PEG‐200 as a linker. A second MDI was used to connect the carbamate group of the SMPU chain and PEG. The impact of soft segment content and PEG length on the mechanical properties and shape recovery of two series of SMPU were compared. In the best case, a 545% increase in maximum stress compared to a linear polymer was attained. The flexibly crosslinked SMPUs behave similarly to natural rubber in their stress–strain curve, but their tensile mechanical properties surpassed those of natural rubber. Shape recovery went up to 96%, which is among the best SMPUs tested so far, and shape recovery remained above 90% after four cyclic tests. The extraordinary shape memory results are analyzed and discussed together with DSC and IR data. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Adhesion energy,spreading coefficient and interfacial tension as an efficient tool for assessing biocide performance

It is estimated that microbiologically influenced corrosion (MIC) contributes to 20%–50% of the total cost of corrosion. Biocides are often used to counter MIC. Normally, the choice of a biocide is based on planktonic kill studies as well as cost of the treatment chemicals. Sessile kill studies have significant advantages over planktonic studies but usually take 8 weeks to complete. Furthermore, both sessile kill and planktonic studies only provide phenomenological results and therefore do not explain the mechanisms. To bridge this gap, we have calculated spreading coefficient and work of adhesion from contact angle measurements as a tool for assessing the performance of a biocide. This novel method provides insights into how biocides interact with a biofilm on a surface and is quicker than sessile kill study. Based on surface energy calculations, we have identified parameters that will aide in the prediction of biofilm removal and prevention. For example, surfactants with a positive spreading coefficient on a substrate and having a stronger affinity for the substrate than the biofilm (i.e., a lower interfacial tension) are effective in biofilm prevention. On the other hand, surfactants with a low interfacial tension with a substrate are effective in biofilm removal. Given the diversity of surfaces to which bacteria attach (carbon steel, near wellbore, membrane, etc.), this rapid technique is a good prediction tool for the effectiveness of a biocide application. This paper will provide an overview of the technique and discuss some examples of surfactants that can be used for biofilm removal and prevention.     

Adaptive Cooperative Decode-and-Forward Transmission with Power Allocation Under Interference Constraint

In this paper, we examine an adaptive decode-and-forward cooperative protocol under interference constraint. In the proposed protocol, relying on the obtained instantaneous signal-to-noise ratios (SNRs), a direct link or relay link is used to transmit data from the secondary source to the secondary destination. In addition, once the relay link is used, the secondary source and relay must adapt their transmit power to maximize the instantaneous SNR of this link. To evaluate the performance of the proposed protocol, we derive closed-form lower-bound and upper-bound expressions for the outage probability over Rayleigh fading channel. Finally, various Monte-Carlo simulations are presented to verify our analysis and compare the performance of the proposed protocol with that of the direct transmission protocol in underlay cognitive network.     

Auto-generated site layout: an integrated approach to real-time sensing of temporary facilities in infrastructure projects*

The use of computational algorithms is popular in method studies, especially in the aspects of knowledge that relates to construction site layout modelling. However, extant approaches in these seldom support automated tracking of construction resources and available spaces. As a result, it is often time-consuming and subjective to autogenerate site layouts. This paper describes the development and implementation of a component-level system that is capable of generating site layouts automatically. The system involves the integration of building information models, genetic algorithm and a radio frequency identification system that has the capability to report object locations in real time. System and software architectures are presented to illustrate the enabling technologies, subsystems and software that are required to facilitate the developed system. A case study is also presented to demonstrate the functionality of the developed system. The practical implication of this research is such that the reported findings builds on gaps in previous scholarly work to develop a system that models site layouts and the associated costs automatically. Findings from the study also facilitate both early signalling of pending delays and their immediate recovery protocols.     

Combination of nanogel polyethylene glycol-polyethylenimine and 6(hydroxymethyl)-1,4-anthracenedione as an anticancer nanomedicine

Polyethylene glycol-polyethylenimine (PEG-PEI) nanogels have been used to deliver nucleic acids and oligonucleotides into cells. First, we synthesized PEG-PEI nanogels with methylene proton ratios (CH2O:CH2N) in PEG-PEI ranging from approximately 6.8:1 to 4:1 and less, as shown by 1H NMR spectra. We first synthesized various nanogels with varying ratios of CH2O:CH2N (methylene proton) in PEG-PEI as shown by 1H NMR spectra and tested their cytotoxicity using a rodent pancreatic adenocarcinoma cell line (Pan 02). We showed that the nanogel PEG-PEI with methylene proton ratio of 4:1 was strongly cytotoxic to Pan 02 cells in vitro, while the nanogel with the methylene proton ratio of 6.8:1 was not toxic. We incorporated a novel anti-cancer drug, 6-(hydroxymethyl)-1,4-anthracenedione (AQ) analogue (AQ10) into nontoxic nanogel PEG-PEI and tested the effect of AQ10 loaded nanogel PEG-PEI (AQ10-nanogel PEG-PEI) and AQ10 dissolved in DMSO on Pan 02 cell growth. The size of this AQ10-nanogel PEG-PEI was characterized using atomic force microscopy (AFM). Our studies showed that the AQ10-nanogel PEG-PEI is readily taken up by Pan 02 cells. Growth attenuation of Pan 02 cells treated with AQ10-nanogel PEG-PEI was three to four times that of cells treated with AQ10 dissolved in DMSO. These results suggest that PEG-PEI, usually used to deliver nucleic acids into cells, can also be used to deliver an insoluble small molecule anticancer drug, AQ10.     

Modeling the Dynamics of an Infrastructure Project

Abstract:   Contractors frequently encounter various problems during project construction, even when properly employing traditional project management techniques and tools. These problems result in low project performance and poor project outcome. A dynamic simulation model is proposed to capture the dynamics of construction projects in the construction phase. Eight key feedback structures from previous models of project dynamics and the unique characteristics of construction projects are identified as dynamic hypotheses. They include the structures of labor, equipment, material, labor and equipment interaction, schedule, rework, safety, and quality. Subsequently, a formal simulation model is mathematically formulated in terms of stock and flow diagrams. The model is then calibrated into a real project under construction. Part of testing indicates that the simulated behavior of the model and the actual behavior of the project are similar. This implies that the model is able to simulate the dynamics of the project and, consequently, to enhance project monitoring and control.     

Comparison of Chemical Composition, Antioxidant and Antimicrobial Activity of Lavender (Lavandula angustifolia L.) Essential Oils Extracted by Supercritical CO2, Hexane and Hydrodistillation

The effects of three different extraction methods, namely hydrodistillation, supercritical CO₂ extraction (SCE) and hexane extraction on the yield, chemical composition and antimicrobial and antioxidant activities of lavender essential oil were investigated in this study. SCE produced a yield of 6.7 % (dry weight), which was comparable to that of solvent extraction (7.6 %), but significantly higher than that of hydrodistillation (4.6 %). The chemical composition of the oils showed considerable variations among the extraction methods, with linalool, linalyl acetate, camphor and borneol making up approximately 80 % of identified components in all extracts. Hexane extraction produced oils with the presence of waxes, colour pigments and albuminious materials with semi-solid consistency, while hydrodistillation extracts showed signs of thermal degradation. The SCE extracts had an aroma with the closest resemblance to the starting material, showing negligible thermal degradation, and exhibited significantly higher antioxidant activity than the hydrodistillation and hexane extracts. Oils produced by SCE and hydrodistillation had antimicrobial activities higher than hexane extracts. The results of this study demonstrate that SCE is a promising process for the extraction of lavender essential oil.     

A comprehensive cardiac motion estimation framework using both untagged and 3-D tagged MR images based on nonrigid registration

In this paper, we present a novel technique based on nonrigid image registration for myocardial motion estimation using both untagged and 3-D tagged MR images. The novel aspect of our technique is its simultaneous usage of complementary information from both untagged and 3-D tagged MR images. To estimate the motion within the myocardium, we register a sequence of tagged and untagged MR images during the cardiac cycle to a set of reference tagged and untagged MR images at end-diastole. The similarity measure is spatially weighted to maximize the utility of information from both images. In addition, the proposed approach integrates a valve plane tracker and adaptive incompressibility into the framework. We have evaluated the proposed approach on 12 subjects. Our results show a clear improvement in terms of accuracy compared to approaches that use either 3-D tagged or untagged MR image information alone. The relative error compared to manually tracked landmarks is less than 15% throughout the cardiac cycle. Finally, we demonstrate the automatic analysis of cardiac function from the myocardial deformation fields.     

Near‐infrared activation of semi‐crystalline shape memory polymer nanocomposites

Recently, indirect activation of the shape memory effect has become an increasingly popular triggering modality for shape memory polymer biomaterials. Amongst the known methods for remote activation, near‐infrared radiation (NIR) remains relatively unexplored, specifically for semicrystalline materials, which possess sharp thermal transitions. Herein, poly(ε‐caprolactone) (PCL) networks were photo‐polymerized from branched precursors doped with 150 nm surface modified gold nanoshells with a surface plasmon resonance of approximately 800 nm. The effect of nanoparticle loading on the thermal, mechanical, and shape memory properties of the PCL matrix were examined. The PCL nanocomposites exhibited excellent shape fixation and nearly quantitative shape memory recovery in response to low intensity NIR irradiation. Further, the heat dissipated by the irradiated nanocomposites to the surrounding medium was found to reach a maximum at biologically relevant temperatures. As such, this nanocomposite system represents a highly attractive candidate for many biomedical shape memory applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4551–4557, 2013     

Synthesis of molybdenum carbide nanoparticles using pulsed wire discharge in mixed atmosphere of kerosene and argon

Pulsed wire discharge was used to prepare nanoparticles of molybdenum and its carbides from Mo wires in a gas mixture of argon and kerosene at pressures of 100, 50, and 25 kPa. The different pressures affected the carburization process and particle formation. The most effective pressure was 25 kPa, where the volume fraction of MoC was identified by Rietveld refinement of X-ray diffraction data to be 98.4%. The particle size distribution was also obtained from transmission electron microscopy measurements, and the smallest geometric mean diameter was determined tobe 24.3 nm for the sample prepared at 25 kPa.