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71.
Alessandrini M Maggio S Porée J De Marchi L Speciale N Franceschini E Bernard O Basset O 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2011,58(11):2344-2360
Ultrasonic tissue characterization has become an area of intensive research. This procedure generally relies on the analysis of the unprocessed echo signal. Because the ultrasound echo is degraded by the non-ideal system point spread function, a deconvolution step could be employed to provide an estimate of the tissue response that could then be exploited for a more accurate characterization. In medical ultrasound, deconvolution is commonly used to increase diagnostic reliability of ultrasound images by improving their contrast and resolution. Most successful algorithms address deconvolution in a maximum a posteriori estimation framework; this typically leads to the solution of l(2)-norm or (1)-norm constrained optimization problems, depending on the choice of the prior distribution. Although these techniques are sufficient to obtain relevant image visual quality improvements, the obtained reflectivity estimates are, however, not appropriate for classification purposes. In this context, we introduce in this paper a maximum a posteriori deconvolution framework expressly derived to improve tissue characterization. The algorithm overcomes limitations associated with standard techniques by using a nonstandard prior model for the tissue response. We present an evaluation of the algorithm performance using both computer simulations and tissue-mimicking phantoms. These studies reveal increased accuracy in the characterization of media with different properties. A comparison with state-of-the-art Wiener and l(1)-norm deconvolution techniques attests to the superiority of the proposed algorithm. 相似文献
72.
Bread staling is a complex phenomenon that originates from multiple physico-chemical events (amylopectin retrogradation, water loss and redistribution) that are not yet completely elucidated. Molecular properties of white bread loaves were characterized by multiple proton Nuclear Magnetic Resonance (NMR) techniques (proton FID, T2 and T1 relaxation time) over 14 days of storage. Changes at a molecular level (faster decay of proton FIDs and shifting of proton T2 relaxation times distributions towards shorter times), indicating a proton mobility reduction of the bread matrix, were observed during storage. Multiple 1H T2 populations were observed and tentatively associated to water-gluten and water-starch domains. Proton T1 of bread was for the first time measured at variable frequencies (Fast Field Cycling NMR) and found to be strongly dependent upon frequency and to decrease in bread during storage, especially at frequencies ≤ 0.2 MHz. An additional proton T1 population, relaxing at 2 ms, was detected at 0.52 MHz only at early storage times and tentatively attributed to a water-gluten domain that lost mobility during storage. 相似文献
73.
Stefan M Marius S Hritcu L Lucian H Mihasan M Marius M Pricop D Daniela P Gostin I Irina G Olariu RI Romeo-Iulian O Dunca S Simona D Melnig V Viorel M 《Journal of materials science. Materials in medicine》2011,22(4):789-796
In the present study, we report enhanced antimicrobial properties of 29 and 23 nm silver nanoparticles (Ag NPs) obtained by
electrochemical synthesis in poly(amide-hydroxyurethane) media. Antibacterial activity assessed by disk diffusion method indicates
that silver nanoparticles produced inhibition zones for both Escherichia coli and Staphylococcus aureus depending on silver concentration. The bacterial growth curve performed in the presence of silver nanoparticles showed a
stronger antibacterial effect at lower concentrations than those described in the earlier reports. The effect was both dose
and size dependent and was more pronounced against Gram negative bacteria than Gram positive one. The smallest Ag NPs used
had a bactericidal effect resulting in killing E. coli cells. Scanning electron microscopy analysis indicated major damage and morphology changes of the silver nanoparticles treated
bacterial cells. The major mechanism responsible for the antibacterial effect probably consists in clusters formation and
nanoparticles anchorage to the bacterial cell surface. 相似文献
74.
Since the 1970s research on energy conversion technologies, such as biomass digestion, has been carried out in the Netherlands. However, after 30 years biomass digestion has not been implemented on large scale. The aim of this paper is to create insight into the underlying factors of this troublesome trajectory by applying the ‘Functions of Innovation Systems’ framework. This results in clear understanding of the (lack of) activities that took place in the innovation system of biomass digestion and the role of government policy in both inducing and blocking this development. The analysis provides several lessons to take into account when developing policies for the acceleration of the development and diffusion of biomass energy. 相似文献
75.
Scarano S Ermini ML Spiriti MM Mascini M Bogani P Minunni M 《Analytical chemistry》2011,83(16):6245-6253
Surface plasmon resonance imaging (SPRi) was used as the transduction principle for the development of optical-based sensing for transgenes detection in human cell lines. The objective was to develop a multianalyte, label-free, and real-time approach for DNA sequences that are identified as markers of transgenosis events. The strategy exploits SPRi sensing to detect the transgenic event by targeting selected marker sequences, which are present on shuttle vector backbone used to carry out the transfection of human embryonic kidney (HEK) cell lines. Here, we identified DNA sequences belonging to the Cytomegalovirus promoter and the Enhanced Green Fluorescent Protein gene. System development is discussed in terms of probe efficiency and influence of secondary structures on biorecognition reaction on sensor; moreover, optimization of PCR samples pretreatment was carried out to allow hybridization on biosensor, together with an approach to increase SPRi signals by in situ mass enhancement. Real-time PCR was also employed as reference technique for marker sequences detection on human HEK cells. We can foresee that the developed system may have potential applications in the field of antidoping research focused on the so-called gene doping. 相似文献
76.
Ionut Zamblau Simona Varvara Liana Maria Muresan 《Journal of Materials Science》2011,46(20):6484-6490
Copper silica composite coatings are an attractive alternative to chromium and nickel coatings in order to avoid environmental
problems and for application in electrical devices. However, co-deposition of SiO2 particles with metals occurs to a rather limited extent, generally under 1%, due to the hydrophilicity of SiO2, which makes the incorporation of particles in a metallic matrix difficult. To overcome this drawback, the influence of cetyl
trimethyl ammonium bromide (CTAB) on the deposition and corrosion behavior of Cu–SiO2 coatings on steel has been studied. It was established that CTAB plays a beneficial role in SiO2 suspension stabilization, promotes the co-deposition of nanoparticles in the copper matrix and improves the deposit morphology
and structure. Consequently, a higher corrosion resistance of Cu–SiO2 deposits obtained in the presence of CTAB was noticed. The most important effect was observed in the case when CTAB was used
in concentration of 10−3 M in the electroplating bath. 相似文献
77.
Hoi Po Cheng Jianming Dai Simona Nemes G S Vijaya Raghavan 《The Journal of microwave power and electromagnetic energy》2007,41(1):35-43
Popcorn offers an environmentally friendly alternative to the commercial synthetic loose-fill packing materials. Popcorn could be used for cushioning purposes if the oil is extracted after the popping process. Conventional and microwave-assisted extraction methods were used for oil extraction from whole and ground, popped and unpopped kernels. The conventional extraction method achieved 68.5% oil recovery from whole popped kernels. However, whole unpopped kernels were not efficiently de-oiled with either of the methods. Extraction of oil from popped kernels is recommended; corn varieties with higher starch content and lower oil content should be used. 相似文献
78.
Copolymers of 2‐(o‐chlorophenyl)‐4‐methylene‐1,3‐dioxolane with methyl methacrylate and styrene were synthesized in benzene at 85 °C in the presence of 2,2′‐azobisisobutyronitrile as initiator. The structure of the resulting copolymers was investigated and a polymerization mechanism was proposed. The intrinsic viscosity of the copolymers in dilute solutions of carbon tetrachloride was determined as a function of temperature and conformational transitions were investigated. Copyright © 2004 Society of Chemical Industry 相似文献
79.
The temperature-programmed polycondensation of tetrachlorobisphenol A with chloromethylphosphonic dichloride is carried out in the sample tube of an NMR spectrometer. From the spectra during polycondensation, the instantaneous concentration of components can be determined. Phosphorus and chlorine-containing polymers with flame-retardant properties are obtained. 相似文献
80.
An analysis of the hardness of resolution of random 3-SAT instances using the Davis-Putnam-Loveland-Logemann (DPLL) algorithm slightly below threshold is presented. While finding a solution for such instances demands exponential effort with high probability, we show that an exponentially small fraction of resolutions require a computation scaling linearly in the size of the instance only. We compute analytically this exponentially small probability of easy resolutions from a large deviation analysis of DPLL with the Generalized Unit Clause search heuristic, and show that the corresponding exponent is smaller (in absolute value) than the growth exponent of the typical resolution time. Our study therefore gives some quantitative basis to heuristic restart solving procedures, and suggests a natural cut-off cost (the size of the instance) for the restart. 相似文献