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11.
Firat AK Karakaş HM Yakinci C Altinok T Alkan A Biçak U 《Magnetic resonance imaging》2004,22(9):1329-1332
Acute disseminated encephalomyelitis (ADEM) is an immune-mediated demyelinating disorder usually encountered in children or adolescents and characterized by multifocal neurological deficits of rapid onset. Typical target areas of demyelination include the corona radiata, centrum semiovale, periventricular white matter, cerebellar peduncles and brainstem. Involvement of deep gray matter nuclei is also frequent. We report a 6-year-old boy with ADEM who had only brainstem involvement. Serial magnetic resonance images representing the stage of disease and response to steroid treatment are presented. 相似文献
12.
13.
Ugur Yahsi Kemal Ulutas Cumali Tav Deniz Deger 《Journal of Polymer Science.Polymer Physics》2008,46(20):2249-2254
A theoretical model to interpret the conductivity of ions through polymer electrolytes is established in terms of the temperature and pressure‐dependent hole fraction computed from Simha‐Somcynsky hole theory. The model successfully linearizes the logarithm of PPG and PEG conductivity data with NaCF3SO3 in a 20:1 ratio for a broad range of temperature and pressure. The conductivity parameter and transmission coefficient with an additive hole fraction constant are discussed and compared for both species. The derivative of the logarithm of conductivity with respect to the hole fraction decreases inversely with the hole fraction and saturates at about 0.08 and 0.12 hole fractions for PPG and PEG, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2249–2254, 2008 相似文献
14.
Muhammed Oz Namik Kemal Saritekin Cetin Bozkurt Erhan Budak Gurcan Yildirim 《Crystal Research and Technology》2016,51(12):708-717
This study is interested in the effect of lithium carbonate on the formation of hexagonal boron nitride (hBN) by means of the available experimental methods including TGA, XRD, FTIR, SEM and HR‐TEM. hBN samples were synthesized at the 1450 °C with different molar ratios of lithium carbonate by modified O'Connor routine. The crystalline hBN formation tended to improve with the increment of the Li2CO3 concentration level (especially after more 20 %). The dopant quantity decreased the residual stresses due to the presence of possible relaxation mechanisms along with the nanocrystal structure, even favored by XRD experimental findings regarding the enhancement of crystal plane alignments, crystallite sizes and lattice parameters. As for the FTIR surveys, the Li2CO3 foreign impurities strengthened more and more the covalent bonds between boron and nitrogen atoms. At the same time, the samples with 40 % lithium carbonate were annealed at the varied temperatures of 1000, 1150, 1300 and 1450 °C to determine the optimum annealing temperature. The XRD+FTIR investigations indicated that the degree of hexagonality improved with the increased annealing temperature. Similarly, the surface morphology confirmed not only the formation of regularity and flaky hexagonal BN structures, but also the strengthening of covalent bonds between the atoms. 相似文献
15.
Sibel Irmak Kemal Solakyildirim Arif Hesenov Oktay Erbatur 《Journal of Analytical Chemistry》2010,65(9):899-906
The aim of this study was to examine the influence of storage conditions and duration on composition and antioxidant activity
of supercritical fluid (SCF) extracted essential oil of rosemary (Rosmarinus officinalis L.). Supercritical extraction was carried out sequentially by using SCF carbondioxide in the first two steps and with 5%
ethanol as entrainer in the third step. The compositions of the extracts were determined by gas chromatography/mass spectrometry.
The total phenolics were analyzed using Folin-Ciocalteau assay. Antioxidant activities of the extracts were tested by β-carotene-linoleic
acid bleaching method. 相似文献
16.
We illustrate how data envelopment analysis (DEA) can be used as a forward-looking method to flag bank holding companies (BHCs) likely to become distressed. Various financial performance models are tested in the period leading up to the recent global financial crisis. Results generally support DEA’s discriminatory and predictive power, suggesting that it can identify distressed banks up to 2 years in advance. Robustness tests reveal that DEA has a stable efficient frontier and its discriminatory and predictive powers prevail even after data perturbations. DEA can be used as a preliminary off-site screening tool by regulators, by business managers to ascertain their standing among competitors, and by investors. Attention by regulators can be further directed at potentially distressed banks as some of them would be candidates for closer monitoring. In conclusion, DEA may be useful in making economic decisions because there is an identifiable link between inefficiency and financial distress. To the best of our knowledge, application of DEA to predict financial distress among BHCs prior to a major crisis has not been published. 相似文献
17.
Urea dimethacrylates functionalized with bisphosphonate/bisphosphonic acid for improved dental materials
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Melek Naz Guven Ece Akyol Fatma Demir Duman Havva Yagci Acar Ozlem Karahan Duygu Avci 《Journal of polymer science. Part A, Polymer chemistry》2017,55(19):3195-3204
Incorporation of bisphosphonate/bisphosphonic acid groups in dental monomer structures should increase interaction of these monomers with dental tissue as these groups have strong affinity for hydroxyapatite. Therefore, new urea dimethacrylates functionalized with bisphosphonate (1a, 1b) and bisphosphonic acid (2a, 2b) groups are synthesized and evaluated for dental applications. Monomers 1a and 1b are synthesized from 2‐isocyanatoethyl methacrylate (IEM) and two bisphosphonated amines (BPA1 and BPA2), prepared as reported elsewhere. Selective dealkylation of the bisphosphonate ester groups of 1a and 1b using trimethylsilyl bromide (TMSBr) gives monomers (2a and 2b) with bisphosphonic acid functionality. X‐ray diffractometer (XRD), Raman spectroscopy, and X‐ray photoelectron spectroscopy (XPS) analyses of monomer‐treated HAP particles show that 2a induces formation of stable monomer‐calcium salts, similar to 10‐methacryloyloxydecyl dihydrogen phosphate (MDP), with higher chemical interaction than 2b. The photopolymerization studies indicate good copolymerizability with commercial dental monomers. In vitro studies on NIH 3T3 mouse embryonic fibroblast cells have clearly shown that the tested monomers (1b and 2b) are not toxic according to the MTT standards. All these properties make these monomers suitable as biocompatible cross‐linkers/adhesives for dental applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3195–3204 相似文献
18.
With the continuous improvement of computational performance, vehicle structural design has been addressed using computational methods, resulting in more efficient development of new vehicles. Most simulation-based optimization approaches generate deterministic optimal designs without considering variability effects in modeling, simulation, and/or manufacturing. One of the main reasons for this omission is due to the fact that the computing time of a single crash analysis for vehicle structural design still requires significant computing time using a state-of-the-art computer. This calls for the development and implementation of an efficient optimization under uncertainty method. In this paper, a new integrated stochastic optimization method, which combines the advantages of metamodeling techniques and Better Optimization of Nonlinear Uncertain Systems (BONUS), is developed for vehicle side impact design. Nonlinear metamodels are built by using a stepwise regression method to replace the expensive computational model and BONUS is employed to obtain optimal designs under uncertainty. A benchmark problem for vehicle safety design is used to demonstrate the method. The main goal of this case study is to maintain or enhance the vehicle side impact test performance while minimizing the vehicle weight under various uncertainties. 相似文献
19.
Opening Enediyne Scissors Wider: pH‐Dependent DNA Photocleavage by meta‐Diyne Lysine Conjugates
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Photochemical activation of meta‐diynes incapable of Bergman and C1–C5 cyclizations still leads to efficient double‐strand DNA cleavage. Spatial proximity of the two arylethynyl groups is not required for efficient DNA photocleavage by the enediyne‐lysine conjugates. Efficiency of the cleavage is a function of the external pH and DNA damage is strongly enhanced at pH < 7. The pH‐dependence of the DNA photocleavage activity stems from the protonation states of lysine amino groups, the internal electron donors responsible for intramolecular PET quenching and deactivation of the photoreactive excited states. DNA‐binding analysis suggests intercalative DNA binding for phenyl substituted conjugate and groove binding for TFP‐substituted conjugate. Additional insights in the possible mechanism for DNA damage from the ROS (Reactive Oxygen Species) scavenger experiments found that generation of singlet oxygen is partially involved in the DNA damage. 相似文献
20.
In this study, water-distilled essential oils from the flowers of Tanacetum zahlbruckneri and flowers and stems of Tanacetum tabrisianum from Turkey were analysed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The flower oil of T. zahlbruckneri was characterised by the sesquiterpenes germacrene D (29.7%) and spathulenol (12%). Flower (A) and stem (B) oil of T. tabrisianum was characterised by 1,8-cineole: 17.6% (A), 22.5% (B), hexadecanoic acid: 10.3% (A), 8% (B), decanoic acid: 5.8% (A) and trans-linalooloxide acetate: 5.3% (A), 4% (B). Unlike a previous report on the essential oil composition of T. tabrisianum, in this study a 1,8-cineole and hexadecanoic acid-rich oil with a low percentage of caryophyllene oxide and spathulenol was obtained. The composition of the essential oil of endemic T. zahlbruckneri was investigated for the first time. 相似文献