An all-fiber source of pulsed twin beams at telecom band for quantum communication

Motivated by the pursuit of a simple system to produce non-classical light sources for long- distance quantum communication, we generate for the first time an all-fiber source of pulsed twin beams in 1550 nm band by using a high gain fiber optical parametric amplifier. The noise of intensity difference of the twin beams is below the shot noise limit by 3.1 dB (10.4 dB after correction for losses). A detailed study reveals a number of limiting factors for higher noise reduction. Therefore, further noise reduction will be feasible once care is taken for these limiting factors.Comment: 5 pages, 6 figure

Defect-Fluorite Gd2Zr2O7 Ceramics under Helium Irradiation: Amorphization, Cell Volume Expansion, and Multi-stage Bubble Formation

Here, we report a study on the radiation resistance enhancement of Gd2Zr2O7 nanograin ceramics, in which amorphization, cell volume expansion and multi-stage helium (He) bubble formation are investigated and discussed. Gd2Zr2O7 ceramics with a series of grain sizes (55-221 nm) were synthesized and irradiated by 190 keV He ion beam up to a fluence of 5x10^17 ions/cm2. Both the degree of post irradiation cell volume expansion and the amorphization fraction appear to be size dependent. As the average grain size evolves from 55 to 221 nm, the degree of post irradiation cell volume expansion increases from 0.56 to 1.02 %, and the amorphization fraction increases from 6.8 to 11.1 %. Additionally, the threshold He concentrations (at. %) of bubbles at different formation stages and locations, including (1) bubbles at grain boundary, (2) bubble-chains and (3) ribbon-like bubbles within the grain, are all found to be much higher in the nanograin ceramic (55 nm) compared with that of the submicron sample (221 nm). We conclude that grain boundary plays a critical role in minimizing the structural defects, and inhibiting the multi-stage He bubble formation process

Approaching single temporal mode operation in twin beams generated by pulse pumped high gain spontaneous four wave mixing

By investigating the intensity correlation function, we study the spectral/temporal mode properties of twin beams generated by the pulse-pumped high gain spontaneous four wave mixing (SFWM) in optical fiber from both the theoretical and experimental aspects. The results show that the temporal property depends not only on the phase matching condition and the filters applied in the signal and idler fields, but also on the gain of SFWM. When the gain of SFWM is low, the spectral/temporal mode properties of the twin beams are determined by the phase matching condition and optical filtering and are usually of multi-mode nature, which leads to a value larger than 1 but distinctly smaller than 2 for the normalized intensity correlation function of individual signal/idler beam. However, when the gain of SFWM is very high, we demonstrate the normalized intensity correlation function of individual signal/idler beam approaches to 2, which is a signature of single temporal mode. This is so even if the frequencies of signal and idler fields are highly correlated so that the twin beams have multiple modes in low gain regime. We find that the reason for this behavior is the dominance of the fundamental mode over other higher order modes at high gain. Our investigation is useful for constructing high quality multi-mode squeezed and entangled states by using pulse-pumped spontaneous parametric down-conversion and SFWM

A generic method to synthesise graphitic carbon coated nanoparticles in large scale and their derivative polymer nanocomposites

A versatile Rotary Chemical Vapour Deposition (RCVD) technique for the in-situ synthesis of large scale carbon-coated non-magnetic metal oxide nanoparticles (NPs) is presented, and a controllable coating thickness varying between 1–5 nm has been achieved. The technique has significantly up-scaled the traditional chemical vapour deposition (CVD) production for NPs from mg level to 10 s of grams per batch, with the potential for continuous manufacturing. The resulting smooth and uniform C-coatings sheathing the inner core metal oxide NPs are made of well-crystallised graphitic layers, as confirmed by electron microscopy imaging, electron dispersive spectrum elemental line scan, X-ray powder diffractions and Raman spectroscopy. Using nylon 12 as an example matrix, we further demonstrate that the inclusion of C-coated composite NPs into the matrix improves the thermal conductivity, from 0.205 W∙m−1∙K−1 for neat nylon 12 to 0.305 W∙m−1∙K−1 for a 4 wt% C-coated ZnO composite, in addition to a 27% improvement in tensile strength at 2 wt% addition

MAPPING QUANTITATIVE TRAIT LOCI ASSOCIATED WITH RESISTANCE TO BACTERIAL SPOT (XANTHOMONAS ARBORICOLA PV. PRUNI) IN PEACH

Bacterial spot, caused by Xanthomonas arboricola pv. pruni (Xap), is a serious disease that can affect peach fruit quality and production worldwide. This disease causes severe defoliation and blemishing of fruit, particularly in areas with high rainfall, strong winds, high humidity and sandy soil. The molecular basis of its tolerance and susceptibility in peach is yet to be understood. To study the genetics of the peach response to Xap, an F2 segregating population between two peach cultivars, `Clayton\u27, a resistant phenotype, and `O\u27Henry\u27, which is very susceptible to Xap, was created. Phenotypic data for leaf and fruit response to Xap infection were collected over three years at two locations: the Sandhills Research Station, Jackson Springs, North Carolina (NC) and the Sandhill Research and Education Center, Pontiac, South Carolina (SC). Phenotypic data for leaf and fruit organs were collected with 26 data points in total. Our phenotypic data suggest that Xap resistance in peach is a quantitative trait, and leaf and fruit resistance is regulated by separate genetic factors. In addition, relative humidity higher than 80% from petal fall to shucks off (gererally from March 15th to April 15th) plays a significant role on the occurrence of Xap disease incidence and severity. A genetic map was initially developed using SSR markers, however, only thirteen SSR markers were put on the linkage map. Therefore, sixty three individuals exhibiting high tolerance/resistance to Xap were genotyped with an IPSC 9K peach SNP array v1. Out of 8,144 SNPs 1,341 were used to construct a high-density genetic linkage map. This map covers a genetic distance of 421.4 cM with an average spacing of 1.6 cM and is used for mapping QTLs responsible for Xap in peach. 95% of the mapped SNP markers on the linkage map showed consistency with the marker order on the peach genome v1.0 assembly. A QTL analysis revealed 14 QTLs involved in Xap resistance: 3 on linkage group (LG) 1; two on each LG2, 3, 4 and 8; and one on each LG5, 6, and 7. One major Xap.Pp.CO-4.1 on LG4 was associated with Xap resistance in leaf, and one major QTL Xap.Pp.CO-5.1 on LG5, was associated with Xap resistance on both leaf and fruit and two major QTLs. While Xap.Pp.CO-1.2 and Xap.Pp.CO-6.1 on LG1 and 6, was associated with Xap resistance in fruit

Global Stability of an SEIRS Model with Impulsive Vaccination and Saturating Incidence Rate

This paper introduces a impulsive vaccination SEIRS epidemic model with constant input, saturation incidence rate and exposed period, and the threshold valueσ=1 is obtained at which disease is eliminated. By using the impulsive differential equation theory, it is proved that whenσ<1, the disease-free periodic solution is globally asymptotically stable, and that whenσ>1,the system is uniformly persistent. On these grounds, it is shown that impulsive vaccination can bring obvious effects on the dynamics behaviors of the system

How the toughest inorganic fullerene cages absorb shockwave pressures in a protective nanocomposite: experimental evidence from two in situ investigations

Nanocomposites fabricated using the toughest caged inorganic fullerene WS2 (IF-WS2) nanoparticles could offer ultimate protection via absorbing shockwaves; however, if the IF-WS2 nanomaterials really work, how they behave and what they experience within the nanocomposites at the right moment of impact have never been investigated effectively, due to the limitations of existing investigation techniques that are unable to elucidate the true characteristics of high-speed impacts in composites. We first fabricated Al matrix model nanocomposites and then unlocked the exact roles of IF-WS2 in it at the exact moment of impact, at a time resolution that has never been attempted before, using two in situ techniques. We find that the presence of IF-WS2 reduced the impact velocity by over 100 m/s and in pressure by at least 2 GPa against those Al and hexagonal WS2 platelet composites at an impact speed of 1000 m/s. The IF-WS2 composites achieved an intriguing inelastic impact and outperformed other reference composites, all originating from the “balloon effect” by absorbing the shockwave pressures. This study not only provides fundamental understanding for the dynamic performance of composites but also benefits the development of protective nanocomposite engineering