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1.
We perform first principles total energy calculations to investigate the atomic structures of the adsorption of phenol (C6H5OH) on hexagonal boron nitride (BN) sheets. Calculations are done within the density functional theory as implemented in the
DMOL code. Electron-ion interactions are modeled according to the local-spin-density-approximation (LSDA) method with the
Perdew-Wang parametrization. Our studies take into account the hexagonal h-BN sheets and the modified by defects d-BN sheets.
The d-BN sheets are composed of one hexagon, three pentagons and three heptagons. Five different atomic structures are investigated:
parallel to the sheet, perpendicular to the sheet at the B site, perpendicular to the sheet at the N site, perpendicular to
the central hexagon and perpendicular to the B-N bond (bridge site). To determine the structural stability we apply the criteria
of minimum energy and vibration frequency. After the structural relaxation phenol molecules adsorb on both h-BN and d-BN sheets.
Results of the binding energies indicate that phenol is chemisorbed. The polarity of the system increases as a consequence
of the defects presence which induces transformation from an ionic to covalent bonding. The elastic properties on the BN structure
present similar behavior to those reported in the literature for graphene. 相似文献
2.
Paloma Rocha Arakaki Paula Andrea Borges Salgado Joo Diego de Agostini Losano Dbora Rodrigues Gonalves Rodrigo del Rio do Valle Ricardo Jos Garcia Pereira Marcilio Nichi 《American journal of primatology》2019,81(12)
Wild animal genetic resource banking (GRB) represents a valuable tool in conservation breeding programs, particularly in cases involving endangered species such as the golden‐headed lion tamarin (Leontopithecus chrysomelas). Thus, we aimed to assess a sperm freezing protocol for golden‐headed lion tamarins using two different exenders: BotuBOV® (BB) and Test Yolk Buffer® (TYB). Ejaculates were collected by penile vibrostimulation from animals housed at São Paulo Zoological Park Foundation, São Paulo, Brazil, and after immediate analysis, two aliquots were diluted in BB and TYB. Postthawing samples were evaluated for total and progressive motility, plasma membrane and acrosome integrities, mitochondrial activity, susceptibility to oxidative stress, and sperm–egg‐binding. No differences between BB and TYB were found for most seminal parameters, except for acrosome integrity and susceptibility to oxidative stress (in both cases BB showed higher values). However, in spite of these differences and regardless of the extender used, postthaw sperm motility and viability with the described protocol were encouraging (on average >50% and >80%, respectively), indicating that sperm cryopreservation may be a short‐term measure for the conservation of golden‐headed lion tamarins. 相似文献
3.
Late Quaternary climate change,relict populations and present‐day refugia in the northern Atacama Desert: a case study from Quebrada La Higuera (18° S)
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4.
Halobacterial megaplasmids are negatively supercoiled 总被引:1,自引:0,他引:1
Purificación López-García Josefa Antón Jose Pascua Abad Ricardo Amils 《Molecular microbiology》1994,11(3):421-427
Several covalently closed circular halobacterial megaplasmids (up to more than 500 kb) from different strains of Halolerax mediterranei, have been resolved by orthogonal-field alternating gel electro-phoresis (OFAGE). These molecules seem to be negatively supercoiled in vivo, as deduced from the effect of intercalating agents affecting their topology and, therefore, their electrophoretic mobility. It has also been demonstrated that the topolsomerase II Inhibitor novobiocin affects the native topological state of halobacterial megaplasmids impeding their migration in OFAGE under standard conditions for resolution of large supercoiled molecules. 相似文献
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7.
Rafael L. X. Consani Mariana R. Carmignani Marcelo F. Mesquita Lourenço Correr‐Sobrinho Ricardo D. Guiraldo 《Gerodontology》2010,27(3):236-242
doi:10.1111/j.1741‐2358.2009.00333.x Effect of microwave treatment on the shear bond strength of different types of commercial teeth to acrylic resin Objective: The purpose of this study was to verify the effect of microwave treatment on the shear bond strength of commercial types of teeth to acrylic resin, when the glossy ridge laps were unmodified (groups 1 and 5), bur abraded (groups 2 and 6), bur grooved (groups 3 and 7) or etched by monomer (groups 4 and 8). Background: Controversial findings have shown that mechanical or chemical changes in ridge‐lap surface of the tooth increase or decrease the bond strength between tooth and acrylic resin, and the microwave disinfection may cause different changes on this bond strength. Materials and methods: Eighty specimens (n = 10) were made with the acrylic resin bonded to tooth glossy ridge lap, polymerised in water at 74°C for 9 h, and deflasked after flask cooling. Specimens of the groups 5, 6, 7 and 8 were individually immersed in 150 ml of water and submitted to microwave treatment in an oven at 650 W for 3 min. Control specimens (groups 1, 2, 3 and 4) were not microwave treated. Shear bond strength test was performed in an Instron machine with a cross‐speed of 1 mm/min. Collected data were submitted to anova and Tukey’s test (α = 0.05). Results: Microwave treatment decreased the shear bond strength values of the tooth/resin bond. In the microwaved and non‐microwaved procedures, mechanical retention improved the shear bond strength when compared with the control and monomer treatments. Conclusion: Shear bond strength of the tooth/resin bond was influenced by the microwave treatment and different commercial teeth association, and was lower for the Biotone tooth. 相似文献
8.
Ricardo Gonzalez-Mendez David Wemmer George Hahn Norma Wade-Jardetzky Oleg Jardetzky 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》1982,720(3):274-280
A continuous-flow NMR culture system for mammalian cells has been developed on which 31P-NMR experiments under complete and strictly physiologic conditions have been performed. Observations on the response of the cellular metabolism to stresses such as starvation, low temperature and changes in environmental pH monitored by 31P-NMR are reported. The response of the intracellular pH relative to the external pH of the growth medium is studied. We find that under the experimental conditions used there exists a ΔpH varying between less than 0.2 and more than 0.6 pH units. These results are compatible with those obtained using other techniques. 相似文献
9.
Ernesto Trucco 《Bulletin of mathematical biology》1956,18(1):65-85
A graphG may have more than one point-baseB
G. In a primordial graphP of Rashevsky's (1954) TransformationT, some of the pointbases may consist of nonspecialized points only, and some other pointbases may contains specialized points.
In this case, Rashevsky's Theorem (1955a) on point-bases may not hold. The Theorem is certainly true ifall point-bases ofP consists of nonspecialized points. A rigorous proof is given. Some results are derived for the more general case, when point-bases
include both kinds of points. A general expression for the point-base ratio of the transformed graphP(T) is obtained. It is shown that with some biologically plausible assumptions Rashevsky's interpretation of the point-base ratio
and his conclusions are still true. A few simple Theorems on point-bases of graphs are included in this work. 相似文献
10.
Infectivity and effects on host of a long-term stored aqueous suspension of Paranosema locustae on juveniles of Dichroplus maculipennis, a pest grasshopper in parts of the Pampas and Patagonia, were evaluated. Infections developed in 90–97.8% of treated individuals. Mortality increased with time, reaching highest values at 30–40 days post-inoculation (79.5–100%). Infected nymphs showed significantly slower development. 相似文献