69 resultados para Chiral symmetry


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To evaluate the correlation between symmetry of the craniofacial skeleton and aesthetics of the nose and upper lip in children with complete unilateral cleft lip and palate (CUCLP).

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The objective of this study was to evaluate the association between nasolabial symmetry and aesthetics in children with complete unilateral cleft lip and palate (CUCLP). Frontal and basal photographs of 60 consecutively treated children with CUCLP (cleft group: 41 boys and 19 girls, mean (SD) age 11 (2) years) and 44 children without clefts (control group: 16 boys and 28 girls, mean (SD) age 11(2) years), were used for evaluation of nasolabial symmetry and aesthetics. Nasal and labial measurements were made to calculate the coefficient of asymmetry (CA). The 5-grade aesthetic index described by Asher-McDade et al. was used to evaluate nasolabial appearance. Correlation and regression analysis were used to identify an association between aesthetics and CA, sex, and the presence of CUCLP. Ten measurements in the cleft, and 2 in the control, group differed significantly between the cleft and non-cleft (or right and left) sides, respectively. The significantly higher values of 9 of 11 CA in the children with CUCLP indicated that they had more asymmetrical nasolabial areas than children without clefts. However, the regression analyses showed that only a few CA were associated with nasolabial aesthetics. In conclusion, nasolabial aesthetics and nasolabial symmetry seem to be only weakly associated in patients with CUCLP.

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The quark-gluon plasma formed in heavy ion collisions contains charged chiral fermions evolving in an external magnetic field. At finite density of electric charge or baryon number (resulting either from nuclear stopping or from fluctuations), the triangle anomaly induces in the plasma the Chiral Magnetic Wave (CMW). The CMW first induces a separation of the right and left chiral charges along the magnetic field; the resulting dipolar axial charge density in turn induces the oppositely directed vector charge currents leading to an electric quadrupole moment of the quark-gluon plasma. Boosted by the strong collective flow, the electric quadrupole moment translates into the charge dependence of the elliptic flow coefficients, so that $v_2(\pi^+) < v_2(\pi^-)$ (at positive net charge). Using the latest quantitative simulations of the produced magnetic field and solving the CMW equation, we make further quantitative estimates of the produced $v_2$ splitting and its centrality dependence. We compare the results with the available experimental data.

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Biological homochirality on earth and its tremendous consequences for pharmaceutical science and technology has led to an ever increasing interest in the selective production, the resolution and the detection of enantiomers of a chiral compound. Chiral surfaces and interfaces that can distinguish between enantiomers play a key role in this respect as enantioselective catalysts as well as for separation purposes. Despite the impressive progress in these areas in the last decade, molecular-level understanding of the interactions that are at the origin of enantiodiscrimination are lagging behind due to the lack of powerful experimental techniques to spot these interactions selectively with high sensitivity. In this article, techniques based on infrared spectroscopy are highlighted that are able to selectively target the chiral properties of interfaces. In particular, these methods are the combination of Attenuated Total Reflection InfraRed (ATR-IR) with Modulation Excitation Spectroscopy (MES) to probe enantiodiscriminating interactions at chiral solid-liquid interfaces and Vibrational Circular Dichroism (VCD), which is used to probe the structure of chirally-modified metal nanoparticles. The former technique aims at suppressing signals arising from non-selective interactions, which may completely hide the signals of interest due to enantiodiscriminating interactions. Recently, this method was successfully applied to investigate enantiodiscrimination at self-assembled monolayers of chiral thiols on gold surfaces. The nanometer size analogues of the latter--gold nanoparticles protected by a monolayer of a chiral thiol--are amenable to VCD spectroscopy. It is shown that this technique yields detailed structural information on the adsorption mode and the conformation of the adsorbed thiol. This may also turn out to be useful to clarify how chirality can be bestowed onto the metal core itself and the nature of the chirality of the latter, which is manifested in the metal-based circular dichroism activity of these nanoparticles.