Determinants of frailty development and progression using a multidimensional frailty index: Evidence from the English Longitudinal Study of Ageing

This work was supported by grant number 689592 "my-AHA" from the Horizon 2020 research funding framework of the European Commission (https://ec.europa.eu/programmes/horizon2020/en).Open Access articl

Analysis of the interplay between soliton fission and modulation instability in supercontinuum generation

We investigate the generation mechanisms for ultrawide spectra in nonlinear optical fibers. Soliton fission and modulation instability represent fundamental mechanisms for the generation process. The primary origin of the spectral broadening changes with the pump-pulse duration. Soliton fission dominates for low input power and short pulses. Its efficiency for supercontinuum generation and especially the extend to the blue side can be increased by proper design of the dispersion profile. The modulation instability has a strong impact for high input powers and greatly enhances the generation process, but leads to a degradation of the coherence properties. Also for short pulses with durations of 60 fs the modulation instability is present and can hardly be suppressed. The interplay between these two effects leads to various characteristics of the resulting spectra, which are modified by to the relative impact of the modulation instability

They Are All After You: Investigating the Viability of a Threat Model That Involves Multiple Shoulder Surfers

Many of the authentication schemes for mobile devices that were proposed lately complicate shoulder surfing by splitting the attacker's attention into two or more entities. For example, multimodal authentication schemes such as GazeTouchPIN and GazeTouchPass require attackers to observe the user's gaze input and the touch input performed on the phone's screen. These schemes have always been evaluated against single observers, while multiple observers could potentially attack these schemes with greater ease, since each of them can focus exclusively on one part of the password. In this work, we study the effectiveness of a novel threat model against authentication schemes that split the attacker's attention. As a case study, we report on a security evaluation of two state of the art authentication schemes in the case of a team of two observers. Our results show that although multiple observers perform better against these schemes than single observers, multimodal schemes are significantly more secure against multiple observers compared to schemes that employ a single modality. We discuss how this threat model impacts the design of authentication schemes

Supercontinuum generation by the modelation instability

We report on a numerical study of supercontinuum generation in a single-mode optical fiber by the modulation instability. An ultrabroadband octave-spanning continuum is generated for femtosecond pulses with subkilowatt peak power. In particular, we investigate the influence of higher-order effects such as third- and fourth-order dispersion, self-steepening and intrapulse Raman scattering on the supercontinuum generation

Limit for pulse compression by pulse splitting

We have detected a fundamental pulse-compression limit for high-nonlinear fibers in the normal dispersion regime near the zero-dispersion wavelength. The desired generation of a broadband continuum by self-phase modulation is limited by already small amounts of third-order dispersion, which results in pulse splitting above a critical pulse power. We investigate the critical fiber length in dependence on pulse- and fiber parameters

Sasa--Satsuma equation: Soliton on a background and its limiting cases

We present a multi-parameter family of a soliton on a background solutions to the Sasa-Satsuma equation. The solution is controlled by a set of several free parameters that control the background amplitude as well as the soliton itself. This family of solutions admits a few nontrivial limiting cases that are considered in detail. Among these special cases is the NLSE limit and the limit of rogue wave solutions

Solitons on a background, rogue waves and classical soliton solutions of Sasa--Satsuma equation

We present the most general multi-parameter family of a soliton on a background solutions to the Sasa-Satsuma equation. The solution contains a set of several free parameters that control the background amplitude as well as the soliton itself. This family of solutions admits nontrivial limiting cases, such as rogue waves and classical solitons, that are considered in detail

Sasa-Satsuma equation: Soliton on a background and its limiting cases

We present a multi-parameter family of a soliton on a background solutions to the Sasa-Satsuma equation. The solution is controlled by a set of several free parameters that control the background amplitude as well as the soliton itself. This family of solutions admits a few nontrivial limiting cases that are considered in detail. Among these special cases is the NLSE limit and the limit of rogue wave solution

Unusual ways of four-wave mixing instability

A pump carrier wave in a dispersive system may decay by giving birth to blue- and red-shifted satellite waves due to modulation or four-wave mixing instability. We analyse situations where the satellites are so different from the carrier wave, that the red-shifted satellite either changes its propagation direction (k 0) or even gets a negative frequency (k, ω < 0). Both situations are beyond the envelope approach and require application of Maxwell equations

Fredholm Alternative for Periodic-Dirichlet Problems for Linear Hyperbolic Systems

This paper concerns hyperbolic systems of two linear first-order PDEs in one space dimension with periodicity conditions in time and reflection boundary conditions in space. The coefficients of the PDEs are supposed to be time independent, but allowed to be discontinuous with respect to the space variable. We construct two scales of Banach spaces (for the solutions and for the right hand sides of the equations, respectively) such that the problem can be modeled by means of Fredholm operators of index zero between corresponding spaces of the two scales.Comment: 20 page