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71.
John K. Gallos Alexandros E. Koumbis Vassiliki P. Xiraphaki Constantinos C. Dellios Evdoxia Coutouli-Argyropoulou 《Tetrahedron》1999,55(52):6304-15180
The influence of the 2-substituent on the diastereoselectivity of the intramolecular cycloadditions in a series of 2-substituted-erythro-3,4-isopropylidene-dioxyhex-5-enenitrile oxides, generated in situ from selected sugar derivatives, was examined. 相似文献
72.
Jongbae?Heo Dagmara?S.?Antkiewicz Martin?M.?Shafer Dawn?A.?K.?Perkins Constantinos?Sioutas James?J.?SchauerEmail author 《Analytical and bioanalytical chemistry》2015,407(20):5953-5963
In order to further our understanding of the influence of chemical components and ultimately specific sources of atmospheric particulate matter (PM) on pro-inflammatory and other adverse cellular responses, we promulgate and apply a suite of chemical fractionation tools to aqueous aerosol extracts of PM samples for analysis in toxicity assays. We illustrate the approach with a study that used water extracts of quasi-ultrafine PM (PM0.25) collected in the Los Angeles Basin. Filtered PM extracts were fractionated using Chelex, a weak anion exchanger diethylaminoethyl (DEAE), a strong anion exchanger (SAX), and a hydrophobic C18 resin, as well as by desferrioxamine (DFO) complexation that binds iron. The fractionated extracts were then analyzed using high-resolution sector field inductively coupled plasma mass spectrometry (SF-ICPMS) to determine elemental composition. Cellular responses to the fractionated extracts were probed in an in vitro rat alveolar macrophages model with measurement of reactive oxygen species (ROS) production and the cytokine tumor necrosis factor-α (TNF-α). The DFO treatment that chelates iron was very effective at reducing the cellular ROS activity but had only a small impact on the TNF-α production. In contrast, the hydrophobic C18 resin treatment had a small impact on the cellular ROS activity but significantly reduced the TNF-α production. The use of statistical methods to integrate the results across all treatments led to the conclusion that sufficient iron must be present to participate in the chemistry needed for ROS activity, but the amount of ROS activity is not proportional to the iron solution concentration. ROS activity was found to be most related to cationic mono- and divalent metals (i.e., Mn and Ni) and oxyanions (i.e., Mo and V). Although the TNF-α production was not significantly affected by the chelexation of iron, it was greatly impacted by the removal of organics with the C18 resin and all other metal removal methods, suggesting that iron is not a critical pathway leading to TNF-α production, but a wide range of soluble metals and organic compounds in particulate matter play a role. Although the results are specific to the Los Angeles Basin, where the samples used in the study were collected, the method employed in the study can be widely employed to study the role of components of particulate matter in in vitro or in vivo assays. 相似文献
73.
Zarganes-Tzitzikas T Terzidis MA Stephanidou-Stephanatou J Tsoleridis CA Kostakis GE 《The Journal of organic chemistry》2011,76(21):9008-9014
Another aspect concerning chromone chemistry leading to the one-pot synthesis of functionalized novel spirobenzofuranones has been described. The synthesis involves reaction of the zwitterionic intermediates formed by the 1:1 interaction between isocyanides and acetylenecarboxylates with 3-cyanochromones, whereupon through an unexpected and unprecedented reaction of the chromone moiety the isolated benzofuranones are formed. The regioselectivity of the reaction was investigated by DFT calculations. The geometries of the intermediates, transition structures, and intermediate products, leading to the final products, were optimized using the B3LYP functional with the 6-31G(d) basis set. The structures of the products were elucidated by 1D and 2D NMR experiments. Full assignment of all (1)H and (13)C NMR chemical shifts has been achieved. A plausible mechanistic rationale is proposed. 相似文献
74.
75.
Marios Pittalis Demetra Pitta-Pantazi Constantinos Christou 《Mathematical Thinking and Learning》2018,20(3):222-247
The aim of this study was to propose a new conceptualization of early number sense. Six-year-old students’ (n = 204) number sense was tracked from the beginning of Grade 1 through the beginning of Grade 2. Data analysis suggested that elementary arithmetic, conventional arithmetic, and algebraic arithmetic contributed to the latent construct early number sense, and the invariance of the model over time was validated empirically. Algebraic arithmetic represents the dimension of early number sense that moves beyond conventional arithmetic and encompasses an abstract understanding of the relations between numbers. A parallel process growth model showed that the three components of number sense adopt a linear growth rate. A structural model showed that the growth rate of the algebraic arithmetic component has a direct effect on the growth rate of conventional arithmetic, and subsequently the growth rate of conventional arithmetic predicts the growth rate of elementary arithmetic. 相似文献
76.
Constantinos V. Chrysikopoulos Vasiliki I. Syngouna Ioanna A. Vasiliadou Vasileios E. Katzourakis 《Transport in Porous Media》2012,94(3):617-642
This study is focused on the transport of Pseudomonas (P.) putida bacterial cells in a 3-D model aquifer. The pilot-scale aquifer consisted of a rectangular glass tank with internal dimensions: 120?cm length, 48?cm width, and 50?cm height, carefully packed with well-characterized quartz sand. The P. putida decay was adequately represented by a first-order model. Transport experiments with a conservative tracer and P. putida were conducted to characterize the aquifer and to investigate the bacterial behavior during transport in water saturated porous media. A 3-D, finite-difference numerical model for bacterial transport in saturated, homogeneous porous media was developed and was used to successfully fit the experimental data. Furthermore, theoretical interaction energy calculations suggested that the extended-DLVO theory seems to predict bacteria attachment onto the aquifer sand better than the classical DLVO theory. 相似文献
77.
Laboratory-scale virus transport experiments were conducted in columns packed with sand under saturated and unsaturated conditions.
The viruses employed were the male-specific RNA coliphage, MS2, and the Salmonella typhimurium phage, PRD1. The mathematical model developed by Sim and Chrysikopoulos (Water Resour Res 36:173–179, 2000) that accounts
for processes responsible for removal of viruses during vertical transport in one-dimensional, unsaturated porous media was
used to fit the data collected from the laboratory experiments. The liquid to liquid–solid and liquid to air–liquid interface
mass transfer rate coefficients were shown to increase for both bacteriophage as saturation levels were reduced. The experimental
results indicate that even for unfavorable attachment conditions within a sand column (e.g., phosphate-buffered saline solution;
pH = 7.5; ionic strength = 2 mM), saturation levels can affect virus transport through porous media. 相似文献
78.
Paraskevas D. Tzanavaras Constantinos K. Zacharis 《Central European Journal of Chemistry》2008,6(2):140-144
Three simple protocols for the extraction of acyclovir from its pharmaceutical creams based on ultrasonication, ultrasonication
with heating and magnetic stirring were evaluated and compared. Extraction kinetics were studied at different time intervals
(5, 10, 15, 30 and 60 min) and the extraction efficiency was determined by HPLC. The effect of concentration of aqueous NaOH
as the extraction medium and the stirring speed were also studied and optimized. Best results were obtained with 50 mL of
0.01 mol L−1 aqueous NaOH with magnetic stirring speed of 500 r.p.m. HPLC analysis involved rapid separation of acyclovir from the cream
matrix using a 100 × 4.6 mm i.d. monolithic column and UV detection at 254 nm. Magnetic stirring produced the best results
in terms of extraction efficiency with an average extraction yield of 100.8%, n = 16 at an optimum extraction time of 15 min. The selected protocol was validated for within and day-to-day precision and
ruggedness.
相似文献
79.
Cano J Cauchy T Ruiz E Milios CJ Stoumpos CC Stamatatos TC Perlepes SP Christou G Brechin EK 《Dalton transactions (Cambridge, England : 2003)》2008,(2):234-240
DFT calculations reveal the unusual ferromagnetic exchange observed in an oxo-centered Mn(III) triangle may originate from a combination of the 'non-planarity' of the bridging oxime ligands and the non-parallel alignment of the Jahn-Teller axes. 相似文献
80.
Epoxy terpenes cyclize readily, by confinement within zeolite NaY, to form exomethylenic cyclohexanols as the major products. The selective monocyclization of 10,11-epoxyfarnesyl acetate within NaY provides a short and efficient biomimetic route to (+/-)-elengasidiol and (+/-)-farnesiferols B-D. [reaction: see text]. 相似文献