Morphology development in polyethylene/polystyrene blends: the influence of processing conditions and interfacial modification

The influence of processing conditions and interfacial modification on the morphology evolution and the composition range within which fully co‐continuous high density polyethylene/polystyrene blend structures can exist during blending in a single screw extruder was studied. Blends ranging from pure A to pure B component, with and without compatibilizer, were prepared under two different shear rates. It was found that high shear rates displaced the breakdown–coalescence balance of the dispersed nodules to the side of coalescence, narrowing the percolation domain and the critical composition for full co‐continuity decreased with increasing shear rates. The addition of a tri‐block compatibilizer induced the percolation threshold of the polystyrene phase to begin at lower percentages of polyethylene but the phase inversion point did not change. The experimental results are discussed in the light of various theoretical models. Copyright © 2005 Society of Chemical Industry     

Efficient ARQ schemes with multiple copy decoding

Several modifications of an efficient automatic repeat request (ARQ) scheme proposed by Weldon (see IEEE Trans. Commun., vol.COM-30, p.480, 1982) are studied. Unlike Weldon's scheme, in which all erroneous data packets are discarded, the present schemes make use of copies of the data packet which may contain errors. A number of channel models are considered, namely, a binary symmetric channel, a nonfading, and a Rayleigh fading channel with additive white Gaussian noise. In most cases, it is found that the throughput can be substantially increased. Under poor channel conditions, the use of forward error correction can lead to further improvement. A type-II ARQ scheme which does not suffer the throughput degradation under good channel conditions due to overhead parity bits associated with conventional forward error correction is also analyzed     

The use of elastography to measure quality characteristics of pork semimembranosus muscle

The objectives of this study were to determine if ultrasonic strain image analysis could estimate pork eating quality parameters (such as fresh color, drip loss, and Warner/Bratzler shear). Intact semimembranosus (SM) muscles (cap off) were analyzed for ultimate pH (pH(ult)). Forty-five SM muscles were selected from the larger allotment of fresh hams over a 3-week period. The SM muscles were selected based on high and low pH(ult) in an attempt to represent a wide range of pork quality. Ultrasonic strain images were obtained perpendicular to the SM muscle fibers of an 8-cm cube. Radio-frequency data from each SM were obtained from a field-of-view (FOV) of 40×30 mm(2) and digitized for each compression step. Tissue displacements were computed for each compression step. Tissue strains were computed from displacement data located in the FOV representing areas of harder and softer muscle tissue and converted to gray scale images at 256 levels. Tissue irregularity of hardness and softness was measured using Fractal dimension and Haralicks parameters. Twenty-one Fractal dimension (FR) parameters, at two neighborhood distances (N), from each strain image and nine Haralick's (HAR) textural parameters (inter-pixel distance=1) were analyzed for each image. The variable FR4N4 had a -0.279 correlation with SM ultimate pH (p<0.10); FR6N8 correlated to WB shear force at 0.325 (p<0.05); and FR21N8 had a correlation coefficient of 0.364 with intramuscular fat (p<0.01). Linear regression equations generated from FRN and HAR parameters for intramuscular fat (R(2)=0.468), Warner/Bratzler shear (R(2)=0.360), and 30 h drip loss (R(2)=0.208). Although elastographic measurement was significantly correlated to shear (p<0.05), a better understanding of physical meat texture is necessary before elastography can be used to identify superior quality pork.     

On the performance of improved quadrature spatial modulation

Quadrature spatial modulation (QSM) utilizes the in‐phase and quadrature spatial dimensions to transmit the real and imaginary parts of a single signal symbol, respectively. The improved QSM (IQSM) transmits two signal symbols per channel use through a combination of two antennas for each of the real and imaginary parts. The main contributions of this study can be summarized as follows. First, we derive an upper bound for the error performance of the IQSM. We then design constellation sets that minimize the error performance of the IQSM for several system configurations. Second, we propose a double QSM (DQSM) that transmits the real and imaginary parts of two signal symbols through any available transmit antennas. Finally, we propose a parallel IQSM (PIQSM) that splits the antenna set into equal subsets and performs IQSM within each subset using the same two signal symbols. Simulation results demonstrate that the proposed constellations significantly outperform conventional constellations. Additionally, DQSM and PIQSM provide a performance similar to that of IQSM while requiring a smaller number of transmit antennas and outperform IQSM with the same number of transmit antennas.     

Non-Intrusive Monitoring of Everyday Behavioral Activities in an Indoor Environment

A non-intrusive design for monitoring everyday activities of an elderly person is presented. The proposed system is intended to be used in the bedroom, allowing the elders to stay at home in a safe environment. The required hardware design is simple in structure and cost effective. The sensor design is implemented by using capacitive sensors and an Arduino microcontroller unit. And a real time graphical user interface is implemented to monitor the elderly person. The performance analysis shows that the sensor design is able to differentiate between a human body and a house pet.     

Analysis of a type II hybrid ARQ scheme with codecombining

An analysis is presented of the selective-repeat type II hybrid AR Q (automatic-repeat-request) scheme, using convolutional coding and exploiting code combining. With code combining, at successive decoding attempts for a data packet, the decoder for error correction operates on a combination of all received sequences for that packet rather than only on the two most recent received ones as in the conventional type II hybrid ARQ scheme. It is shown by means of analysis and computer simulations that with code combining, a significant throughput is achievable, even at very high channel error rates     

In vivo study of hybrid biomaterial scaffold bioactive glass–chitosan after incorporation of Ciprofloxacin

The present study aimed to evaluate the effect of bioactive glass as well as the presence of Ciprofloxacin drug (%Cip) into bioactive glass–chitosan composite on the in vivo behavior of these scaffolds. These scaffolds were implanted in the femoral condyl of an ovariectomized rat. The serum and organs (liver and kidney) of the under investigated rats were analyzed. Also the physicochemical properties of the prepared implants were assessed using Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) before and after implantation (at different periods of implantation). Biochemical and histological analyses of the under investigated rats proved the biocompatibility of the prepared scaffolds. The hydroxyapatite like layer was significantly precipitated on the surface of BG–CH scaffold than BG–CH–20Cip. In this same period, FT-IR of BG–CH shows complete disappearance of Si–O–Si. Their characteristics bands were replaced by P–O group arisen form bone apatite bands. Physicochemical results show progressive degradation of BG–CH and BG–CH–20Cip that occurred at the same time as replacement of the implant by an apatite layer. However, the bioresorbability and bioactivity of BG–CH are faster than those of BG–CH–20Cip. Therefore, the incorporation of the Ciprofloxacin in the BG–CH induces a retarding effect on the formation of the hydroxyapatite, and consequently on the ossification, without any side effects on the liver–kidney.     

Molecular weight influence on shape memory effect of shape memory polymer blend (poly(caprolactone)/styrene-butadiene-styrene)

The shape memory effect (SME) does not only concern the macroscopic structure. It concerns also the polymer structure at morphological, macromolecular, and molecular scales. This effect may depend on different physicochemical properties like morphology heterogeneity, chain rigidity, steric hindrance, chain polarity, free volume, cross-linking or entanglement density, molecular shape and weight, and so on. Hence, finding the relationship between the SME and these properties is very important. This can help to obtain the knowledge about the phenomenon origin and mechanism. One of the basic polymer properties, which can have direct SME, may be the molecular weight (M_w ). The question here is: If the M_w of a shape memory polymer (SMP) changes, for different reasons like degradation, what will be the effect of this change on its SME. In order to answer to this question, the investigation is focused on an SMP blend of 40% poly(ɛ-caprolactone) (PCL) and 60% styrene-butadiene-styrene (SBS). Then, enzymatic hydrolysis is performed on this blend to change its M_w . It is shown that this change is only related to the variation in the M_w of PCL. After that, different samples with a distinct average M_w are prepared and characterized by various experimental methods. Shape memory tests are performed on these blends, and the recovery rate (R_r ) for each of them is determined. It is found that when M_w of PCL decreases, its degree of crystallinity, its glass transition, and its melting temperatures, corresponding to the PCL phase, increase. However, the elongation at break of the blend declines with the reduction in M_w . The tests show that the alteration in the blend's M_w influences its SME. Indeed, R_r of the (PCL/SBS) mixture drops with the decrease in M_w of PCL.     

Distinct Pharmacological Properties of Gaseous CO and CO-Releasing Molecule in Human Platelets

Carbon monoxide (CO)—gaseous or released by CO-RMs—both possess antiplatelet properties; however, it remains uncertain whether the mechanisms involved are the same. Here, we characterise the involvement of soluble guanylate cyclase (sGC) in the effects of CO—delivered by gaseous CO–saturated buffer (CO_G) and generated by CORM-A1—on platelet aggregation and energy metabolism, as well as on vasodilatation in aorta, using light transmission aggregometry, Seahorse XFe technique, and wire myography, respectively. ODQ completely prevented the inhibitory effect of CO_G on platelet aggregation, but did not modify antiplatelet effect of CORM-A1. In turn, CO_G did not affect, whereas CORM-A1 substantially inhibited energy metabolism in platelets. Even though activation of sGC by BAY 41-2272 or BAY 58-2667 inhibited significantly platelet aggregation, their effects on energy metabolism in platelets were absent or weak and could not contribute to antiplatelet effects of sGC activation. In contrast, vasodilatation of murine aortic rings, induced either by CO_G or CORM-A1, was dependent on sGC. We conclude that the source (CO_G vs. CORM-A1) and kinetics (rapid vs. slow) of CO delivery represent key determinants of the mechanism of antiplatelet action of CO, involving either impairment of energy metabolism or activation of sGG.     

Brinkman–Forchheimer modeling for porous media thermoacoustic system

In this paper, analytical studies have been conducted on the flow and thermal fields of unsteady compressible viscous oscillating flow through channels filled with porous media representing stacks in thermoacoustic systems. The flow in the porous material is described by the Brinkman–Forchheimer–extended Darcy model. Analytical expressions for oscillating velocity, temperature, and energy flux density are obtained after linearizing and solving the governing differential equations with long wave, short stack, and small amplitude oscillation approximations. Experimental work is also conducted to verify the temperature difference obtained across the porous stack ends. To produce the experimental results, a thermoacoustic heat pump is designed and constructed where reticulated vitreous carbon (RVC) is used as the stack material. A very good agreement is obtained between the modeling and the experimental results. The expression of temperature difference across the stack ends obtained in the present study is also compared with the existing thermoacoustic literature. The proposed expression surpasses the existing expression available in the literature. The system of equations developed in the present study is a helpful tool for thermal engineers and physicist to design porous stacks for thermoacoustic devices.