High-resolution palynological analysis in Lake Sapanca as a tool to detect recent earthquakes on the North Anatolian Fault

High-resolution palynological analysis of a 38-cm-long core collected from Lake Sapanca, northwest Turkey, reveals large earthquakes that occurred during the second half of the 20th century along the North Anatolian Fault Zone. Four events have disturbed the lacustrine sedimentary sequence. Three of the four events are historical earthquakes in 1999 in Izmit, 1967 in Mudurnu and 1957 in Abant. These events are recorded in the core by turbiditic deposits and reworked sediment and by low overall palynomorph concentrations but high values of thick-exined pollen, fern spores and fungal spores. Palynomorphs in the event beds have been grouped based on their associations in modern moss, river and lake samples. The inferred mechanisms of transport and sources for the palynomorphs are: 1- lake sediment displaced by slump, 2- collapsed shoreline sediment owing to seiche, waves and sudden lake level changes, 3- subsidence of deltas and 4- river-transported soil and sediment from upland areas. The 1999 Izmit earthquake is only weakly recorded by palynomorphs, probably due to recent engineering control on the rivers. The 1967 Mudurnu earthquake had the strongest effect on the lake, introducing successive packages of sediment to the centre of the lake from underwater slopes, the lakeshore and rivers

Stability analysis of second order pulsed Raman laser in dispersion managed systems

8siWavelength tunable synchronous pulse sources are highly desirable for spectroscopy and optical diagnostics. The common method to generate short pulses in the fiber is the use of nonlinear induced spectral broadening which result in soliton shaping in anomalous dispersion regime. However, to generate ultra-short pulses, broadband gain mechanism is also required. In recent years, Raman fiber lasers have retrieved strong interest due to their capability of serving as pump sources in gain-flattened amplifiers for optical communication systems. The fixed-wavelength Raman lasers have been widely studied in the last years, but recently, much focus has been on the multi wavelength tunable Raman fiber lasers which generate output Stokes pulses in a broad wavelength range by so called cascaded stimulated Raman scattering. In this paper we investigate synchronous 1st and 2nd order pulsed Raman lasers that can achieve frequency spacing of up to 1000cm-1 that is highly desired for CARS microscopy. In particular, analytical and numerical analysis of pulsed stability derived for Raman lasers by using dispersion managed telecom fibers and pumped by 1530nm fiber lasers. We show the evolution of the 1st and 2nd order Stokes signals at the output for different pump power and SMF length (determines the net anomalous dispersion) combinations. We investigated the stability of dispersion managed synchronous Raman laser up to second order both analytically and numerically. The results show that the stable 2nd order Raman Stokes pulses with 0.04W to 0.1W peak power and 2ps to 3.5ps pulse width can be achieved in dispersion managed systemopenopenS. K. Kalyoncu; S. Gao; E.K. Tien; Y. Huang; D. Yildirim; E. Adas; S. Wabnitz; O. BoyrazS. K., Kalyoncu; S., Gao; E. K., Tien; Y., Huang; D., Yildirim; E., Adas; Wabnitz, Stefan; O., Boyra

Radiation properties of an integrated optical leaky wave antenna with periodic silicon perturbations

We propose a highly directive optical leaky wave antenna (OLWA) radiating at 1550 nm composed of a dielectric waveguide comprising periodic silicon (Si) perturbations. The antenna working principle is based on the excitation of a leaky wave guided mode in the perturbed waveguide. Here we study the radiation properties for two sets of perturbation dimensions, and show beam scanning capabilities of the antenna (radiation level and direction) at broadside by varying the free space wavelength. Moreover, the use of Si offers the electronic/optical tunability of its complex refractive index by excess electron-hole carrier density generation via current injection (electronic control) or optical absorption (optical control). Therefore, by changing the Si refractive index we vary the leaky wave attenuation constant and the input impedance of the antenna, which in turn allow for beam control capabilities. © 2012 IEEE

Mode-locked picosecond pulse generation from an octave-spanning supercontinuum

We generate mode-locked picosecond pulses near 1110 nm by spectrally slicing and reamplifying an octave-spanning supercontinuum source pumped at 1550 nm. The 1110 nm pulses are near transform-limited, with 1.7 ps duration over their 1.2 nm bandwidth, and exhibit high interpulse coherence. Both the supercontinuum source and the pulse synthesis system are implemented completely in fiber. The versatile source construction suggests that pulse synthesis from sliced supercontinuum may be a useful technique across the 1000 - 2000 nm wavelength range

Hybrid integration of III/V lasers on a silicon-on-insulator (SOI) optical board

Abstract: Heterogeneous integration of III-V semiconductor materials on a silicon-on-insulator (SOI) platform has recently emerged as one of the most promising methods for the fabrication of active photonic devices in silicon photonics. For this integration, it is essential to have a reliable and robust bonding procedure, which also provides a uniform and ultra-thin bonding layer for an effective optical coupling between III-V active layers and SOI waveguides. A new process for bonding of III-V dies to processed siliconon-insulator waveguide circuits using divinylsiloxane-bis-benzocyclobutene (DVS-BCB) was developed using a commercial wafer bonder. This "cold bonding" method significantly simplifies the bonding preparation for machine-based bonding both for die and wafer-scale bonding. High-quality bonding, with ultra-thin bonding layers (<50 nm) is demonstrated, which is suitable for the fabrication of heterogeneously integrated photonic devices, specifically hybrid III-V/Si lasers. K. Mayora, "Novel three-dimensional embedded SU-8 microchannels fabricated using a low temperature full wafer adhesive bonding," J. Micromech. Microeng. 14(7), 1047-1056 (200

‘Browning’ the cardiac and peri-vascular adipose tissues to modulate cardiovascular risk

Excess visceral adiposity, in particular that located adjacent to the heart and coronary arteries is associated with increased cardiovascular risk. In the pathophysiological state, dysfunctional adipose tissue secretes an array of factors modulating vascular function and driving atherogenesis. Conversely, brown and beige adipose tissues utilise glucose and lipids to generate heat and are associated with improved cardiometabolic health. The cardiac and thoracic perivascular adipose tissues are now understood to be composed of brown adipose tissue in the healthy state and undergo a brown-to-white transition i.e. during obesity which may be a driving factor of cardiovascular disease. In this review we discuss the risks of excess cardiac and vascular adiposity and potential mechanisms by which restoring the brown phenotype i.e. “re-browning” could potentially be achieved in clinically relevant populations