RESUMO
Particle accelerators are essential tools in science, hospitals and industry1-6. Yet their costs and large footprint, ranging in length from metres to several kilometres, limit their use. The recently demonstrated nanophotonics-based acceleration of charged particles can reduce the cost and size of these accelerators by orders of magnitude7-9. In this approach, a carefully designed nanostructure transfers energy from laser light to the particles in a phase-synchronous manner, accelerating them. To accelerate particles to the megaelectronvolt range and beyond, with minimal particle loss10,11, the particle beam needs to be confined over extended distances, but the necessary control of the electron beam's phase space has been elusive. Here we demonstrate complex electron phase-space control at optical frequencies in the 225-nanometre narrow channel of a silicon-based photonic nanostructure that is 77.7 micrometres long. In particular, we experimentally show alternating phase focusing10-13, a particle propagation scheme for minimal-loss transport that could, in principle, be arbitrarily long. We expect this work to enable megaelectronvolt electron-beam generation on a photonic chip, with potential for applications in radiotherapy and compact light sources9, and other forms of electron phase-space control resulting in narrow energy or zeptosecond-bunched beams14-16.
RESUMO
Squamous cell carcinoma of the head and neck (HNSCC) most frequently arise in the epithelial tissues of the upper aerodigestive tract. Patients with HNSCC, aged <45 years are categorized as young adults (YA). They are characterized by more severe form of this disease and often lack of classical, causative risk factors (tobacco smoking, alcohol abusing) in comparison to older (typical) patients (OP). The study purpose was to establish an anticipated protective role of DNA repair genes polymorphisms against cancer-causing agents. It was assumed that the polymorphisms in these genes may have a significant role in the etiology of HNSCC in YA. Studies were carried out on three groups: YA group with HNSCC (n = 90), young healthy group without cancer (YH, n = 160) and OP with HNSCC (n = 205). Three polymorphisms in DNA repair genes were analyzed: XPD ex23: A35931C, XRCC1 ex10: G28152A, and XRCC3 ex7: C18067T. The choice of these genes was connected with their involvement in three different DNA repair pathways. Genotyping was carried out by polymerase chain reaction with restriction fragment length polymorphism (PCR-RFLP) technique. Statistical analysis included: calculation of odds ratio (ORs), 95 % confidence intervals (CIs) and p value. There was no significant difference in the distribution of XPD genotypes in YA compared to OP or YH. The XRCC1 AA genotype variant was observed less frequently in HNSCC YA (4.7 %) than in YH and in OP group (17.1 and 10.8 %, respectively). XRCC3 CT genotype variant was observed more frequently in HNSCC YA (61.8 %) than in YH (36.3 %) and this result is statistically significant. This variant was associated with the borderline increased risk of HNSCC development in an early age, however, a similar tendency was not observed in case of double mutated TT variant. The established differences of genotypes distribution do not seem to differentiate substantially YA and OP in head and neck cancer risk.
