Cladding mode coupling in highly localized fiber Bragg gratings: modal properties and transmission spectra

The spectral characteristics of a fiber Bragg grating (FBG) with a transversely inhomogeneous refractive index profile, differs con- siderably from that of a transversely uniform one. Transmission spectra of inhomogeneous and asymmetric FBGs that have been inscribed with focused ultrashort pulses with the so-called point-by-point technique are investigated. The cladding mode resonances of such FBGs can span a full octave in the spectrum and are very pronounced (deeper than 20dB). Using a coupled-mode approach, we compute the strength of resonant coupling and find that coupling into cladding modes of higher azimuthal order is very sensitive to the position of the modification in the core. Exploiting these properties allows precise control of such reflections and may lead to many new sensing applications.Comment: Submission to OE, 16 pages, 6 figure

Global burden of 369 diseases and injuries in 204 countries and territories, 1990–2019: a systematic analysis for the Global Burden of Disease Study 2019

Background: In an era of shifting global agendas and expanded emphasis on non-communicable diseases and injuries along with communicable diseases, sound evidence on trends by cause at the national level is essential. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) provides a systematic scientific assessment of published, publicly available, and contributed data on incidence, prevalence, and mortality for a mutually exclusive and collectively exhaustive list of diseases and injuries. Methods: GBD estimates incidence, prevalence, mortality, years of life lost (YLLs), years lived with disability (YLDs), and disability-adjusted life-years (DALYs) due to 369 diseases and injuries, for two sexes, and for 204 countries and territories. Input data were extracted from censuses, household surveys, civil registration and vital statistics, disease registries, health service use, air pollution monitors, satellite imaging, disease notifications, and other sources. Cause-specific death rates and cause fractions were calculated using the Cause of Death Ensemble model and spatiotemporal Gaussian process regression. Cause-specific deaths were adjusted to match the total all-cause deaths calculated as part of the GBD population, fertility, and mortality estimates. Deaths were multiplied by standard life expectancy at each age to calculate YLLs. A Bayesian meta-regression modelling tool, DisMod-MR 2.1, was used to ensure consistency between incidence, prevalence, remission, excess mortality, and cause-specific mortality for most causes. Prevalence estimates were multiplied by disability weights for mutually exclusive sequelae of diseases and injuries to calculate YLDs. We considered results in the context of the Socio-demographic Index (SDI), a composite indicator of income per capita, years of schooling, and fertility rate in females younger than 25 years. Uncertainty intervals (UIs) were generated for every metric using the 25th and 975th ordered 1000 draw values of the posterior distribution. Findings: Global health has steadily improved over the past 30 years as measured by age-standardised DALY rates. After taking into account population growth and ageing, the absolute number of DALYs has remained stable. Since 2010, the pace of decline in global age-standardised DALY rates has accelerated in age groups younger than 50 years compared with the 1990–2010 time period, with the greatest annualised rate of decline occurring in the 0–9-year age group. Six infectious diseases were among the top ten causes of DALYs in children younger than 10 years in 2019: lower respiratory infections (ranked second), diarrhoeal diseases (third), malaria (fifth), meningitis (sixth), whooping cough (ninth), and sexually transmitted infections (which, in this age group, is fully accounted for by congenital syphilis; ranked tenth). In adolescents aged 10–24 years, three injury causes were among the top causes of DALYs: road injuries (ranked first), self-harm (third), and interpersonal violence (fifth). Five of the causes that were in the top ten for ages 10–24 years were also in the top ten in the 25–49-year age group: road injuries (ranked first), HIV/AIDS (second), low back pain (fourth), headache disorders (fifth), and depressive disorders (sixth). In 2019, ischaemic heart disease and stroke were the top-ranked causes of DALYs in both the 50–74-year and 75-years-and-older age groups. Since 1990, there has been a marked shift towards a greater proportion of burden due to YLDs from non-communicable diseases and injuries. In 2019, there were 11 countries where non-communicable disease and injury YLDs constituted more than half of all disease burden. Decreases in age-standardised DALY rates have accelerated over the past decade in countries at the lower end of the SDI range, while improvements have started to stagnate or even reverse in countries with higher SDI. Interpretation: As disability becomes an increasingly large component of disease burden and a larger component of health expenditure, greater research and developm nt investment is needed to identify new, more effective intervention strategies. With a rapidly ageing global population, the demands on health services to deal with disabling outcomes, which increase with age, will require policy makers to anticipate these changes. The mix of universal and more geographically specific influences on health reinforces the need for regular reporting on population health in detail and by underlying cause to help decision makers to identify success stories of disease control to emulate, as well as opportunities to improve. Funding: Bill & Melinda Gates Foundation. © 2020 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 licens

Orientation dependence of higher order mode reflections in femtosecond pulse written fiber Bragg gratings

Ultrashort pulse lasers allow for the inscription of fiber Bragg gratings largely independent of the fiber geometry. Here, we investigate how the orientation of a reflected higher order mode depends on the FBG's cross-section

Tailored fiber Bragg gratings inscribed with a phase mask and a deformed wave front by ultrashort pulses

We report on the ultrashort pulse inscription of chirped fiber Bragg gratings (FBG) using a constant phase mask and a deformed wave front. To analyze the influence of wave front deformations on the grating period, a numerical model was developed. It is based on a ray optical solution of the diffraction of an arbitrary wave front at a phase mask with a constant period, where the wave front is described by Zernike polynomials. Generally, a plane wave front generates an interference pattern with half the phase mask period. A defocus changes the grating period, while higher order aberrations like coma or spherical aberration yield a chirp along the inscribed grating. Additionally, the grating period depends on the distance of phase mask and fiber. To experimentally deform the wave front of the inscription beam, a cylindrical tuning lens was introduced to the setup. Due to decentering and tilting of the tuning lens, higher order aberrations were generated. Furthermore the fiber was tilted with respect to the phase mask. A chirped FBG with a FWHM bandwidth of 6.2 nm was realized

ANTIANGIOGENIC AND VASCULAR-DISRUPTING AGENTS IN ENDOMETRIOSIS: PITFALLS AND PROMISES.

It is widely known that angiogenesis plays a key role in endometriotic lesion formation and development. Antiangiogenic treatments aimed at inhibiting new vessel formation have proven efficient in experimental models. However, as antiangiogenic strategies do not target pre-existing pericyte-protected vessels, they require chronic administration and are likely to be beneficial for early-stage disease only or to prevent recurrence after surgery. Moreover, they may have detrimental effects on reproductive function. Vascular-disrupting agents (VDAs) have emerged as a promising new tool for the treatment of tumors. VDAs target established blood vessels, resulting in tumor ischemia and necrosis. These agents may therefore be more efficient against advanced disease. Two major types of VDAs are being developed for cancer: ligand-directed VDAs using antibodies, peptides and growth factors to deliver toxic effectors to tumor endothelium; and small-molecule VDAs exploiting physiological differences between tumor and normal endothelium to induce acute vascular shut-down. The ongoing evolution in genomics and proteomics is revolutionizing the discovery of novel endothelial markers. Several studies suggest that the vasculature of endometriotic lesions may have particular pathophysiological properties, which could be exploited for the development of selective VDAs. The aim of this review is to explore the merits and limitations of vascular therapy for the treatment of endometriosis