Storage of multiple single-photon pulses emitted from a quantum dot in a solid-state quantum memory

Quantum repeaters are critical components for distributing entanglement over long distances in presence of unavoidable optical losses during transmission. Stimulated by Duan-Lukin-Cirac-Zoller protocol, many improved quantum-repeater protocols based on quantum memories have been proposed, which commonly focus on the entanglement-distribution rate. Among these protocols, the elimination of multi-photons (multi-photon-pairs) and the use of multimode quantum memory are demonstrated to have the ability to greatly improve the entanglement-distribution rate. Here, we demonstrate the storage of deterministic single photons emitted from a quantum dot in a polarization-maintaining solid-state quantum memory; in addition, multi-temporal-mode memory with $1$, $20$ and $100$ narrow single-photon pulses is also demonstrated. Multi-photons are eliminated, and only one photon at most is contained in each pulse. Moreover, the solid-state properties of both sub-systems make this configuration more stable and easier to be scalable. Our work will be helpful in the construction of efficient quantum repeaters based on all-solid-state devicesComment: Published version, including supplementary materia

Coexpression of VEGF-C and COX-2 and its association with lymphangiogenesis in human breast cancer

<p>Abstract</p> <p>Background</p> <p>Lymphangiogenesis has become a new research frontier in tumor metastasis since the discovery of reliable lymphatic markers that have allowed observation and isolation of lymphatic endothelium. Cyclooxygenase-2 (COX-2) has been reported to be involved in the critical steps in carcinogenesis. However, possible role of COX-2 in lymphangiogenesis and lymphatic metastasis is still poorly understood. In present study, we aimed to investigate the relationship between vascular endothelial growth factor-C (VEGF-C) and COX-2 in human breast cancer, and correlations with lymphangiogenesis and prognosis.</p> <p>Methods</p> <p>Tissue samples of primary tumors from 70 patients undergoing intentionally curative surgical resections for breast cancer were immunohistochemically examined for VEGF-C, COX-2, and D2-40 expressions. The association between COX-2 and VEGF-C expressions and clinicopathological parameters as well as prognosis were analysised. To demonstrate the presence of proliferating lymphatic endothelial cells, 10 random cases with high LVD counts were selected for D2-40/Ki-67 double immunostaining.</p> <p>Results</p> <p>A significant correlation was found between the expression of VEGF-C and COX-2 (<it>r </it>= 0.529, <it>P </it>< 0.001), and both elevated VEGF-C expression and elevated COX-2 expression were associated with higher lymph vessel density (LVD), lymph node metastasis and D2-40 positive lymphatic invasion (LVI) as well as worse disease free survival (DFS) and overall survival (OS) in a univariate analysis. In the double immunostain for the lymph vessel marker D2-40 and the proliferation marker Ki-67, the results confirmed Ki-67-positive nuclei in a proportion of lymph vessel endothelial cells.</p> <p>Conclusion</p> <p>There is indeed lymphangiogenesis in breast cancer, the most compelling evidence being the presence of proliferating lymphatic endothelial cells. VEGF-C and COX-2 are coexpressed and significantly associated with lymphangiogenesis and prognosis in invasive breast cancer. Suggesting COX-2 may up-regulate VEGF-C expression and thus promote lymph node metastasis via lymphangiogenesis pathway in human breast cancer.</p

Complete chloroplast genome sequence of Mucuna prurien and its phylogenetic position

Mucuna pruriens is traditional medicinal plant originated in South Africa. We characterize the complete plastid genome of M. pruriens, which is a circular-mapping molecule 152,119 bp in length. The genome has a large single-copy region (LSC) of 78,258 bp and a small single-copy region (SSC) of 18,735 bp, respectively. Additionally, the overall GC content of the chloroplast genome was 35.37%. The genome contains 138 genes, including 96 protein-coding, 38 tRNA, and four rRNA genes. The gene content and structure are conserved compared to other species in the genus Glycine. The chloroplast genome and existing data were used to infer its phylogenetic position. The results showed that M. pruriens clustered together with Glycine max and G. soja. These findings provide potential genetic markers that can aid in understanding the genetic diversity of M. pruriens

Optimization of <i>CDT-1</i> and <i>XYL1</i> Expression for Balanced Co-Production of Ethanol and Xylitol from Cellobiose and Xylose by Engineered <i>Saccharomyces cerevisiae</i>

<div><p>Production of ethanol and xylitol from lignocellulosic hydrolysates is an alternative to the traditional production of ethanol in utilizing biomass. However, the conversion efficiency of xylose to xylitol is restricted by glucose repression, causing a low xylitol titer. To this end, we cloned genes <i>CDT-1</i> (encoding a cellodextrin transporter) and <i>gh1-1</i> (encoding an intracellular β-glucosidase) from <i>Neurospora crassa</i> and <i>XYL1</i> (encoding a xylose reductase that converts xylose into xylitol) from <i>Scheffersomyces stipitis</i> into <i>Saccharomyces cerevisiae</i>, enabling simultaneous production of ethanol and xylitol from a mixture of cellobiose and xylose (main components of lignocellulosic hydrolysates). We further optimized the expression levels of <i>CDT-1</i> and <i>XYL1</i> by manipulating their promoters and copy-numbers, and constructed an engineered <i>S. cerevisiae</i> strain (carrying one copy of <i>PGK1p-CDT1</i> and two copies of <i>TDH3p-XYL1</i>), which showed an 85.7% increase in xylitol production from the mixture of cellobiose and xylose than that from the mixture of glucose and xylose. Thus, we achieved a balanced co-fermentation of cellobiose (0.165 g/L/h) and xylose (0.162 g/L/h) at similar rates to co-produce ethanol (0.36 g/g) and xylitol (1.00 g/g).</p></div

Construction strategy of the recombinant <i>S.</i><i>cerevisiae</i> strain to achieve the co-production of ethanol and xylitol from ligonocellulosic biomass.

<p>The uptake and hydrolysis of cellobiose (derived from cellulose) were accomplished by a cellodextrin transporter (encoded by <i>cdt-1</i>) and an intracellular β-glucosidase (encoded by <i>gh1-1</i>), respectively. The uptake and conversion of xylose (derived from hemicellulose) was accomplished by endogenous hexose transporters and a xylose reductase (encoded by <i>XYL1</i>), respectively. Thus, ethanol and xylitol were produced simultaneously by this engineered yeast. NAD(P)H for xylitol production was provided by the cellobiose metabolism.</p

Strains and plasmids used in the study.

<p>Strains and plasmids used in the study.</p

Time profiles of the concentrations of cellobiose (A), ethanol (B), xylose (C) and xylitol (D) by the five recombinant yeast strains (SCX-1 to -5, see

<p><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0068317#pone-0068317-t002" target="_blank"><b>Table 2</b></a><b>).</b> The fermentation was conducted under anaerobic conditions in 50 mL YPXC medium containing 20 g/L xylose and 20 g/L cellobiose. The initial cell density was OD₆₀₀ = 1.0. The data was the mean ± standard deviation of duplicate experiments.</p

Co-fermentation of xylose and cellobiose by the five recombinant strains under anaerobic conditions.

<p>The growth was conducted in 50 mL YPXC medium containing 20 g/L xylose and 20 g/L cellobiose. The initial cell density was OD₆₀₀ = 1.0.</p>a<p>rxylose: volumetric xylose uptake rate in 120-h fermentation.</p>b<p>The values were calculated based on the concentrations of metabolites after 120-h fermentation.</p>c<p>Ethanol yield was represented as g/g consumed cellobiose.</p>d<p>Xylitol yield was represented as g/g consumed xylose.</p>e<p>The value was significantly different (<i>p</i><0.05) from SCX-2 and SCX-3.</p>f<p>The values were significantly different (<i>p</i><0.05) from SCX-4.</p

Detailed information on the promoter and copy number of the genes <i>CDT-1</i> and <i>XYL1</i> in the five recombinant strains.

<p>M: multiple copies.</p