Mid-IR Multiwavelength Difference Frequency Generation Based on Fiber Lasers

A mid-IR multiwavelength difference frequency generation (DFG) laser source with fiber laser fundamental lights is demonstrated by using the dispersion property of PPLN to broaden the quasi-phase-matching (QPM) acceptance bandwidth (BW). Our results show that the QPM BW for the pump YDFL is much larger than that for the signal EDFL. Using a multiwavelength YDFL and a single-wavelength EDFL as the pump and the signal lights, the DFG laser source can simultaneously emit 14 mid-IR wavelengths with the spacing of 14nm at a fixed PPLN temperature. Moreover, mid-IR multiwavelength lasing lines can be synchronously tuned between 3.28 and 3.47μm

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Transient response of wavelength-switchable erbium -doped fiber lasers with linear coupled cavities

The transient characteristics of an erbium-doped fiber (F.DF) laser, which can switch between wavelengths. are investigated. 77te laser has a set of coupled linear cavities. The slow gain dynamics of EDFs and the cross-gain saturation in the coupled cavities give rise to delayed switching responses and relocation oscillations, which are respertively measured to be l ins and 3.5 ms for the worst rase, and which mar be decreased by increasing the pump power. Thus, the switching speed of the laser may be higher than 100 H

Morphological diversity of Quercus fossil pollen in the northern South China Sea during the last glacial maximum and its paleoclimatic implication.

We aimed to obtain high resolution vegetation data and climate information about the LGM in the inland of the northern SCS based on key pollen types. Dominant Quercus fossil pollen grains in the core from the continental shelf of the northern SCS have been identified at the infrageneric level by using scanning electron microscopy. Based on tectum ornamentation, we recognized five sculpture types of Quercus pollen, namely, rodlike, rodlike masked, rodlike vertical, verrucate and micro-verrucate. Such a high diversity of Quercus fossil pollen types indicated that broadleaved forests were widely distributed in the inland along the northern SCS and included species of the subgenera Cyclobalanopsis and Quercus, of which subgenus Cyclobalanopsis populations were highly dominant. Low abundance of deciduous Quercus pollen probably derived from temperate-subtropical forests, while abundant evergreen pollen types of subgenura Quercus and Cyclobalanopsis, as well as other pollen of broadleaved taxa in the pollen assemblages, strongly suggest that the inland has been covered by dense subtropical forests. Consequently, the warm and humid subtropical climate prevailed during the LGM in the inland along the northern SCS. Our results shed new light on regional climatic conditions during the LGM in eastern Asia based on high diversity of Quercus fossil pollen in marine deposits from northern SCS

On the Lanzhou index of graphs

Let $G$ be a simple graph with vertex set $V(G)$ and edge set $E(G)$. The Lanzhou index of a graph $G$ is defined as ${\rm Lz}(G)=\sum_{u\in V(G)}\,d_{\overline{G}}(v)\,d_G(v)^2$, where $d_G(v)$ denotes the degree of the vertex $v$ in $G$. In this paper, we determine extremal values of the Lanzhou index in terms of some graph parameters, as well as Nordhaus--Gaddum--type results. We also find relations between Lanzhou Index and other topological indices

YAP enhances autophagic flux to promote breast cancer cell survival in response to nutrient deprivation.

The Yes-associated protein (YAP), a transcriptional coactivator inactivated by the Hippo tumor suppressor pathway, functions as an oncoprotein in a variety of cancers. However, its contribution to breast cancer remains controversial. This study investigated the role of YAP in breast cancer cells under nutrient deprivation (ND). Here, we show that YAP knockdown sensitized MCF7 breast cancer cells to nutrient deprivation-induced apoptosis. Furthermore, in response to ND, YAP increased the autolysosome degradation, thereby enhancing the cellular autophagic flux in breast cancer cells. Of note, autophagy is crucial for YAP to protect MCF7 cells from apoptosis under ND conditions. In addition, the TEA domain (TEAD) family of growth-promoting transcription factors was indispensable for YAP-mediated regulation of autophagy. Collectively, our data reveal a role for YAP in promoting breast cancer cell survival upon ND stress and uncover an unappreciated function of YAP/TEAD in the regulation of autophagy

Visualization 1: Q-switched fiber laser based on an acousto-optic modulator with injection seeding technique

The video of injection-locked process Originally published in Applied Optics on 10 June 2016 (ao-55-17-4584