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.     

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.     

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.     

Structural, magnetic and electrical properties of (La0.70−xNdx)Sr0.30Mn0.70Cr0.30O3 with 0 ≤ x ≤ 0.30

The structural, magnetic and electrical properties of (La_0.70−xNd_x)Sr_0.30Mn_0.70Cr_0.30O₃ perovskites (0 ≤ x ≤ 0.30) prepared by the usual ceramic procedure were investigated. Structural Rietveld refinement revealed that these compounds crystallize in a rhombohedral perovskite structure when x = 0, 0.10 and 0.20, while for x = 0.30 the structure becomes orthorhombic (Pbnm). It was found that the substitution of La by Nd reduces the Curie temperature (T_C). The FC, ZFC, M(H) and AC susceptibility measurements show typical canted-antiferromagnetism for the Nd-doped samples, in which a ferromagnetic component coexists with predominant antiferromagnetic interactions. The values of the magnetization (M(H)) decrease very slightly when increasing the Nd content, compared to the undoped sample (M_S values at 5 T and 2 K are, respectively, 47.9, 47.3 and 47.5 emu/g for x = 0.10, 0.20 and 0.30, compared to 48.2 emu/g for x = 0), indicating that the Nd³⁺ contribution is negligible compared to the total moment of the ferromagnetic (Mn/Cr) network. The resistivity increases by several orders of magnitude with Nd-doping and the semi-conducting behaviour persists in the whole temperature range. The interaction between Mn⁴⁺–O–Cr³⁺and Cr³⁺–O–Cr³⁺ is responsible for the semi-conducting state.     

Large magnetocaloric effect in Ti-modified La0.70Sr0.30MnO3 perovskite

The effect of Ti substitution on the magnetocaloric effect of the La_0.70Sr_0.30MnO₃ perovskite was investigated. The magnetic entropy change (− ΔS_M) was deduced by two methods: a Maxwell relation and the Landau theory. The magnetocaloric data displays a large value of the magnetic entropy change (− ΔS_M) near the Curie temperature (T_C = 210 K), which increases when increasing the applied magnetic field. A good agreement is found between the experimental (− ΔS_M) and the one estimated by Landau theory. The relative cooling power values vary from 49 to 288 J kg^− 1 upon variation of the applied magnetic field at 1 and 5 T. Under 5 T, the relative cooling power value for La_0.70Sr_0.30Mn_0.90Ti_0.10O₃ is about 70% of the conventional refrigerant Gd material. As a result, the herein reported compound can be considered as a promising material in magnetic refrigeration technology.     

Complementary punctured convolutional (CPC) codes and theirapplications

Presents a new class of punctured convolutional codes that are complementary (CPC codes). A set of punctured convolutional codes derived from the same original low rate code are said to be complementary if they are equivalent (in terms of their distance properties) and if when combined yield at least the original low rate code. Based on these CPC codes the author proposes and analyzes a variation of the type II hybrid ARQ scheme which is called a type III hybrid ARQ scheme. With the type III hybrid ARQ scheme, the starting code rate can be chosen to match the channel noise requirements, and as with the type II scheme, packets that are detected in error are not discarded, but are combined with complementary transmissions provided by the transmitter to help recover the transmitted message. The main advantage is that any complementary sequence sent for a packet that is detected with errors is self decodable. That is the decoder does not have to rely on previously received sequences for the same data packet for decoding, as is generally the case with incremental redundancy ARQ schemes. This feature is desirable especially in situations where a transmitted packet can be lost or severely damaged as a result of interference. CPC codes can find applications in diversity transmission systems. A novel complementary diversity scheme which makes use of CPC codes is briefly discussed     

Elastographic dynamic range expansion using variable applied strains

In elastography, we want to image the entire range of stiffnesses of the elastic components found in inhomogeneous tissues. In order to achieve this, the elastographic dynamic range should equal the entire stiffness dynamic range in the target. Various sources of noise limit the dynamic range of elastography. The recently-defined strain filter concept offers an analytical and graphical way of observing these limitations. In this paper, we describe a method that achieves the expansion of the elastographic dynamic range. It involves the application of variable strains in combination with selective storage of strain data that have optimal elastographic signal-to-noise ratios. This expands the current dynamic range of elastography by orders of magnitude when compared to single compression elastography. The process is explained theoretically using the strain filter framework, and 1 D as well as 2D tissue simulations are used to corroborate the theory.     

CT scan contrast enhancement using singular value decomposition and adaptive gamma correction

We propose in this paper a new enhancement algorithm dedicated to dark computed tomography (CT) scan based on discrete wavelet transform with singular value decomposition (DWT–SVD) followed by adaptive gamma correction (AGC). Discrete wavelet transform (DWT) is considered to decompose the input dark CT image in four sub-bands. Singular value decomposition (SVD) is used in order to compute the corresponding singular value matrix of low–low (LL) sub-band image. The enhanced LL sub-band is determined by scaling the singular value matrix of original LL sub-band by an adequate correction factor, followed by inverse SVD. For a further contrast improvement, the new enhanced LL sub-band image is processed using an AGC algorithm. Finally, the obtained LL sub-band image undergoes inverse DWT together with the unprocessed sub-bands to generate the final enhanced image. This proposed method has the advantage of being fully automatic and could be applied for dark input images with either low or moderate contrast. Different dark CT images are considered to compare the performance of our proposed method to three other enhancement techniques using both objective and subjective assessments. Simulation results show that our proposed algorithm consistently produces good contrast enhancement, with best brightness and edges details conservation and with minimum added distortions to the enhanced CT images.     

Optimal business process deployment cost in cloud resources

Cloud computing is the fastest emerging technology that proposes several resources under various pricing strategies that are specified based on temporal constraints. The main aim of cloud computing is to enhance the performance level and minimize operating costs. Thus, organizations looking towards optimizing their spending on IT infrastructure find such pricing strategies very attractive, especially, to deploy their business process models. However, discovering the optimal deployment cost of a business process in cloud resources proposed under various pricing strategies becomes a highly challenging problem. So, the objective of the present paper is to present an approach that assists business process designers in finding an optimal assignment or scheduling based on the variety of pricing strategies. We use linear programming models with an objective function under a set of constraints. Besides, we propose an extension of the famous cloud simulator provided in the market, CloudSim, to simulate the cloud resources consumed to deploy a business process model. The experimental results show the feasibility, effectiveness, and performance of our approach.

     

Comparative analysis of triacylglycerols from Olea europaea L. fruits using HPLC and MALDI‐TOFMS

MALDI‐TOFMS and HPLC are two analytical methods that were used to characterize triacylglycerols (TAG) of the Meski, Sayali, and Picholine Tunisian olive varieties. The HPLC chromatograms of the oils showed the presence of 15 TAG species, among which triolein (OOO) was the most abundant (21–48%). In the Sayali cultivar, OOO was the predominant TAG species followed by POO and LOO. However, the minor TAG molecules were represented by LnLO and LnLP. MALDI mass spectra produced sodiated ([M + Na]⁺) and potassiated ([M + K]⁺) TAG molecules; only the major TAG were potassiated [OOO + K] ([OOO + K]⁺, [POO + K]⁺, and [LOO + K]⁺). In contrast to the HPLC chromatograms, the MALDI mass spectra showed 13 peaks of TAG. The major peak was detected at m/z 907, which corresponds to OOO with an Na⁺ adduct. The results from both HPLC and MALDI techniques predict the fatty acid composition and their percentages for each olive variety. Practical applications: TAG are the main components in vegetable oils. These biomolecules determine the physical, chemical, and nutritional properties of the oils. The nutritional benefits of TAG are related to DAG (moderate plasma lipid level) and esterified FA, which are intermediate biosynthetic molecules of TAG. TAG analysis is necessary to discriminate between oils of different origin, since some oils have similar FA profiles. Olive products, oils, and table olives, are the main diet sources of TAG in the Mediterranean countries. In this work, chromatographic and spectrometric methods were used for TAG analysis and characterization of Tunisian olive varieties.