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The crystallization and melting behaviors of linear polylactic acid (PLA) treated by compressed CO2 was investigated. The isothermal crystallization test indicated that while PLA exhibited very low crystallization kinetics under atmospheric pressure, CO2 exposure significantly increased PLA’s crystallization rate; a high crystallinity of 16.5% was achieved after CO2 treatment for only 1 min at 100 °C and 6.89 MPa. One melting peak could be found in the DSC curve, and this exhibited a slight dependency on treatment times, temperatures, and pressures. PLA samples tended to foam during the gas release process, and a foaming window as a function of time and temperature was established. Based on the foaming window, crystallinity, and cell morphology, it was found that foaming clearly reduced the needed time for PLA’s crystallization equilibrium.

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In this study, the non-isothermal cold crystallization and isothermal melt crystallization of both linear and long-chain-branched (LCB) polylactide (PLA) were investigated using a differential scanning calorimeter (DSC). Talc was used as a nucleating agent to promote crystallization. The effects of chain branching on PLA’s cold crystallization kinetics at different heating rates and on PLA’s melt crystallization kinetics under different temperatures were studied by using Avrami analysis. The results showed that LCB-PLAs have faster cold and melt crystallization rates than those of linear PLA, since branched chains can play a role of nucleating site. Talc is a powerful nucleating agent, especially for linear PLA, either in cold crystallization or melt crystallization process. It was seen that addition of talc to PLA improves the crystallinity of PLA samples with more linear structure, more effectively because of its role of crystal nucleation. In PLA samples with more branched structure, talc has the least effect on crystallinity suggesting that the branched structure dominated crystallization already regardless of the presence of talc. Isothermal melt crystallization experimental results also showed that branched PLAs crystallized much faster than linear PLA and talc could increase the melt crystallization rate of linear PLA, but not that of PLA with a more branched structure.

We discuss excess noise contributions of a practical balanced homodyne detector in Gaussianmodulated coherent-state (GMCS) quantum key distribution (QKD). We point out the key generated from the original realistic model of GMCS QKD may not be secure. In our refined realistic model, we take into account excess noise due to the finite bandwidth of the homodyne detector and the fluctuation of the local oscillator. A high speed balanced homodyne detector suitable for GMCS QKD in the telecommunication wavelength region is built and experimentally tested. The 3 dB bandwidth of the balanced homodyne detector is found to be 104 MHz and its electronic noise level is 13 dB below the shot noise at a local oscillator level of 8.5×10 8 photon per pulse.The secure key rate of a GMCS QKD experiment with this homodyne detector is expected to reach Mbits/s over a few kilometers. PACS numbers: 03.67.Dd * Electronic address: l.qian@utoronto.ca. If we assume E(W n ) = 0, E(W n W n+2 ) = 0 (only consecutive pulse value has a non-zero expectation), CC = a. In GMCS QKD, the variance of Bob's measurement of individual pulse will be contributed by the variances of its adjacent pulses. With the quadrature modulation of the coherent state prepared by Alice V , the excess noise due to the overlap between pulses ε overlap referring to

A balanced homodyne detector for highrate Gaussian-modulated coherent-state quantum key distribution Yue-Meng Chi, Bing Qi, Wen Zhu et al.Quantum key distribution and 1 Gbps data encryption over a single fibre P Eraerds, N Walenta, M Legré et al. Abstract. In this paper, we study the feasibility of conducting quantum key distribution (QKD) together with classical communication through the same optical fiber by employing dense-wavelength-division-multiplexing (DWDM) technology at telecom wavelength. The impact of classical channels on the quantum channel has been investigated for both QKD based on single-photon detection and QKD based on homodyne detection. Our studies show that the latter can tolerate a much higher level of contamination from classical channels than the former. This is because the local oscillator used in the homodyne detector acts as a 'mode selector', which can suppress noise photons effectively. We have performed simulations based on both the decoy BB84 QKD protocol and the Gaussian-modulated coherent state (GMCS) QKD protocol. While the former cannot tolerate even one classical channel (with a power of 0 dBm), the latter can be multiplexed with 38 classical channels (0 dBm power per channel) and still has a secure distance around 10 km. A preliminary experiment has been conducted based on a 100 MHz bandwidth homodyne detector.

Protein-stabilized gold nanoclusters (protein-Au NCs) have been an attractive frontier of nanoparticle research. Due to their unique fluorescence properties, high stability, environmentally friendly synthetic routes and nontoxicity, protein-Au NCs could find applications in highly sensitive and selective detection of metal ions, inorganic ions and biomolecules in food, soil, water and biological samples. The past few years have witnessed the development of many successful strategies for the preparation of numerous protein-Au NC-based sensing systems. In this review, we focus on a number of sensing systems based on protein-Au NCs for the detection of various analytes of interest with a special emphasis on their corresponding sensing mechanisms.

The crystallization behavior, banded spherulite and morphological transition of poly(L-lactide) (PLLA) phases within the block copolymers were investigated. All experimental results showed that the structure and thermal properties of PLLA-PCL copolymers could be adjusted by varying the ratios of the chain length of the two blocks. Morphological results indicated that the banded spherulites of PLLA formed when PLLArich copolymers crystallized. PCL segments introduced unbalanced stresses around PLLA lamellar crystals, which resulted in a bending moment responsible for twisting of PLLA lamellar crystals. As the block length ratio of PCL to PLLA increased, an over accumulation of PCL segments influenced the twisting of PLLA lamellae. In addition, it was interesting to find that the banded spherulite morphology changed with increasing the crystallization temperature. The crystallization temperature has an effect on the relationship between the sense of lamellar twisting and the morphological transition of PLLA, which is reflected in the fact that the band spacing of banded spherulites showed strong temperature dependence when the crystallization temperature exceeds 115 C, while it exhibited weak temperature dependence below 115 C. In particular, above 125 C the band spacing disappeared and nonbanded spherulites formed.