Evanescent-wave coupling phase-matching for ultrawidely tunable frequency conversion in silicon-waveguide chips.

We propose and analyze an evanescent-wave coupling phase-matching method for ultrawidely tunable frequency conversion in coupled -waveguides which will boost the nonlinear optical properties of photonic chips. Taking a silicon-waveguide as an example, we design a two-coupled-waveguide system which provides an efficient coupling coefficient for the compensation of phase-mismatch in spontaneous four-wave mixing, achieving widely tunable entangled photon pairs which are usually not accessible in -waveguides. A tuning range of 1170-2300 for TE-mode or 1400-1730 for TM-mode entangled photons is realized when the inter-waveguide gap varies within the range of 400-900 .

Identification of Sex-Specific Markers Reveals Male Heterogametic Sex Determination in Pseudobagrus ussuriensis.

Comprehending sex determination mechanism is a first step for developing sex control breeding biotechnologies in fish. Pseudobagrus ussuriensis, one of bagrid catfishes in Bagridae, had been observed to have about threefold size dimorphism between males and females, but its sex determination mechanism had been unknown. In this study, we firstly used the amplified fragment length polymorphism (AFLP)-based screening approach to isolate a male-specific DNA fragment and thereby identified a 10,569 bp of male-specific sequence and a 10,365 bp of female-related sequence by genome walking in the bagrid catfish, in which a substantial genetic differentiation with 96.