Evidence of diffusive fractal aggregation of TiO2 nanoparticles by femtosecond laser ablation at ambient conditions

The specific mechanisms which leads to the formation of fractal nanostructures by pulsed laser deposition remain elusive despite intense research efforts, motivated mainly by the technological interest in obtaining tailored nanostructures with simple and scalable production methods. Here we focus on fractal nanostructures of titanium dioxide, $TiO_2$, a strategic material for many applications, obtained by femtosecond laser ablation at ambient conditions. We model the fractal formation through extensive Monte Carlo simulations based on a set of minimal assumptions: irreversible sticking and size independent diffusion. Our model is able to reproduce the fractal dimensions and the area distributions of the nanostructures obtained in the experiments for different densities of the ablated material. The comparison of theory and experiment show that such fractal aggregates are formed after landing of the ablated material on the substrate surface by a diffusive mechanism. Finally we discuss the role of the thermal conductivity of the substrate and the laser fluence on the properties of the fractal nanostructures. Our results represent an advancement towards controlling the production of fractal nanostructures by pulsed laser deposition.Comment: 21 page

Investigation of the regenerative and cascadability properties of optical signal processing devices at high bit-rates.

This thesis investigates the use of Semiconductor Optical Amplifiers (SOA) for 10 and 40Gb/s all-optical 3R signal regeneration and wavelength conversion for application to advanced high-speed all-optical WDM networks. Detailed experimental characterisation of the magnitude and the time scales of inter-band nonlinear effects in SOA is carried out. The regenerative properties of SOA gates are theoretically investigated and related to the SOA physical parameters by means of deriving the SOA gate transfer function. A novel configuration for all-optical regeneration based on Polarisation Switching in an SOA-assisted Sagnac Interferometer (PSSI) is proposed and used to demonstrate, for the first time, multi-channel simultaneous 3R regeneration. This scheme allows to significantly enhance the switching frequency of the SOA, demonstrating error-free regeneration of 40Gb/s signal with long PRBS sequences using an SOA with carrier lifetime exceeding 250ps. The reshaping and retiming ability of the scheme are also assessed experimentally at bit-rate of 40Gb/s, to show the largest distortion tolerance range published to date for regeneration. The scheme is also used to demonstrate 40 to lOGb/s demultiplexing. The cascadability of optical regenerators and wavelength converters is also investigated experimentally. The impact of varying the inter-regenerator spacing in transmission with cascaded wavelength conversion and 3R regeneration over transoceanic distances, is experimentally investigated for the first time, using a novel reconfigurable fibre loop. These results show that a trade-off exists between the transmission signal Q-factor and the inter-regenerator spacing, which depends on the regenerator transfer function characteristics, and thus can be predicted from the SOA parameters. In 40Gb/s transmission with optical regeneration it was demonstrated that the use of an optical regenerator before the electrical receiver increases the power margin and maximum error-free transmission distance at 40Gb/s in excess of 100km. Finally a novel concept for multi-channel wavelength conversion and regeneration is presented utilising an integrated SOA array in a novel configuration to demonstrate, for the first time, simultaneous regenerative wavelength conversion of 1 OGb/s signals. This also shows the potential for large scale monolithic integration for optical processing applications in WDM networks

Epitope-dependent Selection of Highly Restricted or Diverse T Cell Receptor Repertoires in Response to Persistent Infection by Epstein-Barr Virus

The T cell receptor (TCR) repertoires of cytotoxic responses to the immunodominant and subdominant HLA A11–restricted epitopes in the Epstein-Barr virus (EBV) nuclear antigen-4 were investigated in four healthy virus carriers. The response to the subdominant epitope (EBNA4 399-408, designated AVF) was highly restricted with conserved Vβ usage and identical length and amino acid motifs in the third complementarity-determining regions (CDR3), while a broad repertoire using different combinations of TCR-α/β V and J segments and CDR3 regions was selected by the immunodominant epitope (EBNA4 416-424, designated IVT). Distinct patterns of interaction with the A11–peptide complex were revealed for each AVF- or IVT-specific TCR clonotype by alanine scanning mutagenesis analysis. Blocking of cytotoxic function by antibodies specific for the CD8 coreceptor indicated that, while AVF-specific TCRs are of high affinity, the oligoclonal response to the IVT epitope includes both low- and high-affinity TCRs. Thus, comparison of the memory response to two epitopes derived from the same viral antigen and presented through the same MHC class I allele suggests that immunodominance may correlate with the capacity to maintain a broad TCR repertoire

Lithium attenuates behavioral and biochemical effects of neuropeptide S in mice

Neuropeptide S (NPS) and its receptor NPSR comprise a recently deorphaned G-protein-coupled receptor system. There is a body of evidence suggesting the involvement of NPS in wakefulness, anxiety, locomotor activity and oxidative stress damage. Considering that mood stabilizers block the stimulatory effect of psychostimulants in rodents, the present study aimed to investigate the effects of the pretreatment with lithium and valproate on the hyperlocomotion evoked by NPS. Another relevant action induced by lithium and valproate is the neuroprotection against oxidative stress. Thus, aiming to get further information about the mechanisms of action of NPS, herein we evaluated the effects of NPS, lithium and valproate, and the combination of them on oxidative stress damage. Behavioral studies revealed that the pretreatment with lithium (100 mg/kg, i.p.) and valproate (200 mg/kg, i.p.) prevented hyperlocomotion evoked by NPS 0.1 nmol. Importantly, the dose of valproate used in this study reduced mouse locomotion, although it did not reach the statistical significance. Biochemical analyses showed that lithium attenuated thiobarbituric reactive species (TBARS) formation in the striatum, cerebellum and hippocampus. NPS per se reduced TBARS levels only in the hippocampus. Valproate did not significantly affect TBARS levels in the brain. However, the combination of mood stabilizers and NPS blocked, instead of potentiate, the neuroprotective effects of each one. No relevant alterations were observed in carbonylated proteins after all treatments. Altogether, the present findings suggested that mainly the mood stabilizer lithium evoked antagonistic effects on the mediation of hyperlocomotion and protection against lipid peroxidation induced by NPS

Up to 10.7-Gb/s high-PDG RSOA-based colorless transmitter for WDM networks

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Ultrasound Examination of Common Carotid Adventitial Thickness Can Differentiate Takayasu Arteritis and Large Vessel Giant Cell Arteritis

Pathological studies have demonstrated that the adventitial layer is markedly thickened in Takayasu (TAK) as compared to large vessel giant cell arteritis (LV-GCA). An ultrasound (US) examination of the arterial vessels allows the determination of intima media thickness (IMT) and of adventitial layer thickness (extra media thickness (EMT)). No previous study has evaluated if there are differences in EMT thickness between TAK and LV-GCA. In this cross-sectional retrospective study of stored ultrasound (US) imaging, we have compared common carotid artery (CCA) EMT and IMT in a series of consecutive TAK and LV-GCA patients. US examination CCA IMT and EMT were significantly higher in TAK as compared to LV-GCA. With ROC curve analysis, we have found that an EMT > 0.76 mm has high sensitivity and specificity for TAK CCA examination. The percentage of CCA at EMT > 0.76 mm and the total arterial wall thickening were significantly higher in TAK group examinations. EMT thickness correlated with disease duration and IMT in the TAK group, as well as with the IMT and ESR values in the LV-GCA group. Upon multivariate logistic regression analysis, factors independently associated with TAK CCA were EMT > 0.76 mm and age. No significant variation in IMT and EMT could be demonstrated in subsequent US CCA examinations

Hpv-specific systemic antibody responses and memory b cells are independently maintained up to 6 years and in a vaccine-specific manner following immunization with cervarix and gardasil in adolescent and young adult women in vaccination programs in Italy

Human papillomavirus (HPV) persistent infections are associated with cervical cancer and other HPV-related diseases and tumors. Thus, the characterization of long lasting immunity to currently available HPV vaccines is important. A total of 149 female subjects vaccinated with Cervarix or Gardasil participated to the study and they were stratified according to age (10–12-year-old and 16–20-year-old). Humoral immune responses (IgG and neutralizing antibody titers, antibody avidity) and circulating memory B cells were analyzed after an average of 4–6 years from the third immunization. The humoral responses against HPV-16 and HPV-18 (and HPV-6 and HPV- 11 for Gardasil) were high in both age groups and vaccines up to six years from the third dose. However, Cervarix induced significantly higher and more persistent antibody responses, while the two vaccines were rather equivalent in inducing memory B cells against HPV-16 and HPV-18. Moreover, the percentage of subjects with vaccine-specific memory B cells was even superior among Gardasil vaccinees and, conversely, Cervarix vaccinated individuals with circulating antibodies, but undetectable memory B cells were found. Finally, a higher proportion of Cervarix-vaccinated subjects displayed cross-neutralizing responses against non-vaccine types HPV-31 and HPV-45. Gardasil and Cervarix may, thus, differently affect long-lasting humoral immunity from both the quantitative and qualitative point of view

Influence of steps on the tilting and adsorption dynamics of ordered Pn films on vicinal Ag(111) surfaces

Here we present a structural study of pentacene (Pn) thin films on vicinal Ag(111) surfaces by He atom diffraction measurements and density functional theory (DFT) calculations supplemented with van der Waals (vdW) interactions. Our He atom diffraction results suggest initial adsorption at the step edges evidenced by initial slow specular reflection intensity decay rate as a function of Pn deposition time. In parallel with the experimental findings, our DFT+vdW calculations predict the step edges as the most stable adsorption site on the surface. An isolated molecule adsorbs as tilted on the step edge with a binding energy of 1.4 eV. In addition, a complete monolayer (ML) with pentacenes flat on the terraces and tilted only at the step edges is found to be more stable than one with all lying flat or tilted molecules, which in turn influences multilayers. Hence our results suggest that step edges can trap Pn molecules and act as nucleation sites for the growth of ordered thin films with a crystal structure similar to that of bulk Pn.Comment: 4 pages, 4 figures, 1 tabl

Embedded modulable self-tuning cavity for WDM-PON transmitter

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