AN EXPERIMENTAL STUDY ON THERMAL STABILITY OF FAEE BIODIESEL FUEL WITH ETHANOL

Biodiesel fuel is usually synthesized from vegetable oil and animal fat, and now it has been widely used in tractors, trucks, buses and ships. Unlike traditional fossil fuels, biodiesel is more environment-friendly and it is renewable, which can help people solve the energy crisis to some extent. Nowadays, supercritical esterification has become a novel way to produce biodiesel, but high temperature may cause the decomposition of biodiesel. Researchers mainly focus on studying the properties of fatty acid methyl ester (FAME), however, fatty acid ethyl ester (FAEE) biodiesel has only been slightly explored. So in this study, ethanol was used to synthesize biodiesel instead of methanol. Also, the thermal decomposition of FAEE biodiesel with excess ethanol was also studied. In the synthesis studies of FAEE biodiesel, the conditions evaluated were: molar ratio of ethanol to oil of 9:1, potassium hydroxide is chosen as the catalyst, and the reaction is kept at 75°C (±1°C) and 1 atm for 2 hours. In order to study the decomposition of biodiesel, the thermal decomposition experiments were performed in stainless steel coils at the temperature from 250°C to 425°C for residence time from 3 to 63 minutes. When ethanol was added, the volume ratio of ethanol to biodiesel was 1:1. All the products were analyzed by GC-FID and GC-MS. There are mainly three kinds of reactions observed in the thermal decomposition of biodiesel: isomerization, polymerization and pyrolysis. They occurred at the following temperature range respectively: ≥ 275 °C, ≥ 300 °C and ≥ 350 °C. When the temperature is below 275 °C, the decomposition ratio is less than 5%, which suggests that FAEE biodiesel is stable below 275 °C. It is also found that at a given temperature, longer residence time results in higher decomposition ratio. A first-order reversible reaction model was proposed to represent the thermal decomposition of FAEE biodiesel, this model fits the experimental data very well from 250 °C to 400 °C. At 425 °C, the first-order irreversible reaction model is better, which suggests that the main reaction is pyrolysis at 425 °C. The reaction rate constants were calculated using these two models. Kinetic analysis was also conducted. The Arrhenius equation and van\u27t Hoff equation were used to define the kinetic parameters. For the forward reaction, the pre-exponential factor (A) is 2.54×109 min-1 and the activation energy (Ea) is 128.2 kJ/mol. For the reverse reaction, A is 7.98 min-1 and Ea is 29.6 kJ/mol. For the entire reaction, the standard enthalpy (∆H0) is 98.6 kJ/mol. In fitting the data, the high coefficient of determination of higher than 0.97 was obtained, which supports the hypothesis that the first-order reversible reaction model was reasonable over the range of conditions studied

Towards Fast Coherent Anti-Stokes Raman Scattering Microspectroscopy

Coherent anti-Stokes Raman scattering (CARS) microspectroscopy is a nonlinear spectroscopy and imaging technique that probes the vibrational and rotational modes of the molecule, enabling chemical-selective microscopy. Over the past years, CARS has found applications in a wide range of fields such as tumor imaging, gas sensing, and flow cytometry. More recently, commercial components and even a microscopic solution dedicated to CARS has become available. This research is devoted to the development of a high-speed, high-sensitivity CARS microspectroscopy system for chemical and biomedical analysis. We started with an easy-to-implement CARS scheme based on ultrafast pulse shaping of single laser beam. We demonstrated an improved setup that achieved higher epi-detection efficiency as compared to earlier experiment, and allowed low-wavenumber Raman band detection below 100 cm. We further simplified our setup by adopting a folded pulse-shaper design, and incorporated the femtosecond adaptive spectroscopic technique (FAST) developed earlier in the group to achieve versatile single-beam CARS detection with significant nonresonant background suppression. Finally, through utilizing the phase information contained in the signal, we devised and implemented an upgraded system by adopting heterodyne detection in the single-beam CARS setup to achieve high speed spectral detection with background suppression. We have also combined spectral detection and pulse shaping in the setup so as to achieve a one-box-solution for CARS measurement. To further extend the Raman detection range, it is necessary to incorporate means of wavelength extension to achieve broadband excitation. We studied the supercontinuum (SC) generation in large mode area photonic crystal fiber pumped by an industrial picosecond laser. Such an extension unit allowed a simultaneous Raman excitation bandwidth of over 3000 cm?1. We built a multiplex CARS system based on this SC source, and demonstrated its applicability through imaging standard samples. We further constructed a laser-scanning CARS microscope that can provide high spectral resolution and acquisition speed, and showed its capability in 3-dimensional scanning CARS microscopy. In order to boost CARS imaging speed, we also experimented with the wide-field CARS scheme, in which CARS excitation was performed over a large area simultaneously. Using the high-power SC source, we combined the wide-field CARS with multiplex CARS excitation scheme, such that a broad range of Raman modes over a significant spatial region were excited, and CARS image was obtained by applying a corresponding filter. We showed chemical-selective imaging using standard polymer microsphere samples, and demonstrated video-rate CARS microscopy using this setup

Security of a new two-way continuous-variable quantum key distribution protocol

The original two-way continuous-variable quantum-key-distribution (CV QKD) protocols [S. Pirandola, S. Mancini, S. Lloyd, and S. L. Braunstein, Nature Physics 4, 726 (2008)] give the security against the collective attack on the condition of the tomography of the quantum channels. We propose a family of new two-way CV QKD protocols and prove their security against collective entangling cloner attacks without the tomography of the quantum channels. The simulation result indicates that the new protocols maintain the same advantage as the original two-way protocols whose tolerable excess noise surpasses that of the one-way CV-QKD protocol. We also show that all sub-protocols within the family have higher secret key rate and much longer transmission distance than the one-way CV-QKD protocol for the noisy channel.Comment: 19 pages, 4 figures, accepted for publication in International Journal of Quantum Informatio

Vertically scanned laser sheet microscopy

Laser sheet microscopy is a widely used imaging technique for imaging the three-dimensional distribution of a fluorescence signal in fixed tissue or small organisms. In laser sheet microscopy, the stripe artifacts caused by high absorption or high scattering structures are very common, greatly affecting image quality. To solve this problem, we report here a two-step procedure which consists of continuously acquiring laser sheet images while vertically displacing the sample, and then using the variational stationary noise remover (VSNR) method to further reduce the remaining stripes. Images from a cleared murine colon acquired with a vertical scan are compared with common stitching procedures demonstrating that vertically scanned light sheet microscopy greatly improves the performance of current light sheet microscopy approaches without the need for complex changes to the imaging setup and allows imaging of elongated samples, extending the field of view in the vertical direction.This work was supported in part by the Bill and Melinda Gates Foundation, the National Basic Research Program of China (973 Program) under Grant No. 2011CB707700, the National Natural Science Foundation of China under Grant No. 81227901, 81027002, 61231004, and 81101095, the Fellowship for Young International Scientists of the Chinese Academy of Sciences under Grant No. 2010Y2GA03, and the Instrument Developing Project of the Chinese Academy of Sciences under Grant No. YZ201164. A. Arranz acknowledges support from the Marie Curie Intra-European Fellowship program IEF-2010-275137. J.R. acknowledges support from EC FP7 IMI project PREDICT-TB, the EC FP7 CIG grant HIGHTHROUGHPUT TOMO, and the Spanish MINECO project grant FIS2013-41802-R MESO-IMAGING

Continuous-variable quantum key distribution with Gaussian source noise

Source noise affects the security of continuous-variable quantum key distribution (CV QKD), and is diffcult to analyze. We propose a model to characterize Gaussian source noise through introducing a neutral party (Fred) who induces the noise with a general unitary transformation. Without knowing Fred's exact state, we derive the security bounds for both reverse and direct reconciliations and show that the bound for reverse reconciliation is tight.Comment: 7 pages, 3 figure