Engineering nanoscale hypersonic phonon transport.

Controlling vibrations in solids is crucial to tailor their elastic properties and interaction with light. Thermal vibrations represent a source of noise and dephasing for many physical processes at the quantum level. One strategy to avoid these vibrations is to structure a solid such that it possesses a phononic stop band, that is, a frequency range over which there are no available elastic waves. Here we demonstrate the complete absence of thermal vibrations in a nanostructured silicon membrane at room temperature over a broad spectral window, with a 5.3-GHz-wide bandgap centred at 8.4 GHz. By constructing a line-defect waveguide, we directly measure gigahertz guided modes without any external excitation using Brillouin light scattering spectroscopy. Our experimental results show that the shamrock crystal geometry can be used as an efficient platform for phonon manipulation with possible applications in optomechanics and signal processing transduction.

Fiber taper diameter characterization using forward Brillouin scattering.

We propose a fast and non-destructive method to characterize the absolute diameter and uniformity of micrometer-scale fiber tapers using a pump and probe forward Brillouin scattering setup. The fundamental torsional-radial acoustic mode supported by the wire is excited using a pulsed pump laser and oscillates at a frequency that is inversely proportional to the taper waist diameter. This standing time-varying torsional-radial wave induces polarization modulation on a probe signal, whose spectrum structure reveals the sample diameter and its non-uniformity. By comparing our results with measurements using scanning-electron microscopy, a relative deviation of 1% or less was demonstrated, and diameter non-uniformity of less than 0.5% could be detected.

Brillouin scattering self-cancellation.

The interaction between light and acoustic phonons is strongly modified in sub-wavelength confinement, and has led to the demonstration and control of Brillouin scattering in photonic structures such as nano-scale optical waveguides and cavities. Besides the small optical mode volume, two physical mechanisms come into play simultaneously: a volume effect caused by the strain-induced refractive index perturbation (known as photo-elasticity), and a surface effect caused by the shift of the optical boundaries due to mechanical vibrations. As a result, proper material and structure engineering allows one to control each contribution individually. Here, we experimentally demonstrate the perfect cancellation of Brillouin scattering arising from Rayleigh acoustic waves by engineering a silica nanowire with exactly opposing photo-elastic and moving-boundary effects. This demonstration provides clear experimental evidence that the interplay between the two mechanisms is a promising tool to precisely control the photon-phonon interaction, enhancing or suppressing it.

Polymorphisms of pro-inflammatory cytokine genes and the risk for acute suppurative or chronic nonsuppurative apical periodontitis in a Colombian population.

AIM: To determine the association of functional single nucleotide polymorphisms in genes of the pro-inflammatory cytokines tumour necrosis factor-α, interleukin-1ß, interleukin-8 and interleukin-12B with the development of two clinical forms of apical periodontitis (AP): acute suppurative and chronic nonsuppurative. METHODOLOGY: The study included 120 patients from Bucaramanga City, Colombia, 63 diagnosed with acute suppurative AP (ASAP) and 57 diagnosed with chronic nonsuppurative AP (CNAP). Genotyping for IL1B +3954 (rs1143634), IL8 / CXCL8 -251 (rs4073), IL12B +1188 (rs3212227) and TNFA -308 (rs1800629) was performed by the PCR-restriction fragment length polymorphisms method. The statistical analysis was performed using STATA 10.0 and PLINK V1.07 software. RESULTS: Significant differences in the distribution of IL8 / CXCL8 -251 A allele (P adjusted = 0.041; OR adjusted = 0.41, CI adjusted = 0.31-0.97) and IL8 / CXCL -251 TT genotype (P adjusted = 0.04; OR adjusted = 2.24, CI adjusted = 1.04-4.84) were observed comparing patients diagnosed with ASAP and CNAP. No association was observed in genotype and allele distribution for other genetic polymorphisms analysed. CONCLUSION: This study provides molecular epidemiological evidence that suggests in the present cohort that IL8 / CXCL8 -251 T allele, which is associated with higher production of IL8/CXCL8, is also associated with a higher risk of developing acute suppurative form of AP, whereas IL8 / CXCL8 -251 A allele, which is associated with lower production of IL8/CXCL8, is associated with chronic nonsuppurative form of AP. This suggests a pivotal role for IL-8/CXCL8 in periapical disease because of its ability to induce chemotaxis and modulating the directed migration of neutrophils to the site of inflammation in response to microbial infection of pulp.

Interleukin 4, interleukin 4 receptor-α and interleukin 10 gene polymorphisms in Chagas disease.

In this study, we investigated the association between single-nucleotide polymorphisms (SNPs) of the interleukin-4 (IL4), interleukin-4 receptor-α (IL4RA) and interleukin-10 (IL10) genes with the development of chagasic heart disease. This study included 260 patients from Colombia who were serologically positive for Trypanosoma cruzi antigens (cardiomyopathic, n=130; asymptomatic, n=130). Genotypes were determined by polymerase chain reaction (PCR)-restriction fragment length polymorphism or sequence-specific primer methods. We found statistically significant differences in the distribution of the IL4RA +148 AA (P=0·025, OR=1·89, CI=1·04-3·43) genotype when comparing asymptomatic and symptomatic patients. No statistically significant differences in the genotype and allele frequency of IL4 and IL10 gene polymorphisms between symptomatic and asymptomatic patients were observed. Our experimental evidence suggests that the IL4RA +148 AA genotype has a weak association with the development of chagasic cardiomyopathy in the population under study.