Test and Analysis of Timekeeping Performance of Atomic Clock.

At present, there are few articles about the timekeeping performance of domestic atomic clocks in their moving state. In this paper, the frequency stability changes of hydrogen atomic and cesium atomic clocks in stationary and moving states are compared and analyzed; the frequency stability of the atomic clock at the beginning of its transition from moving state to stationary state is tested and analyzed; the influence of three main noises of atomic clocks on frequency stability is analyzed; and finally, the difference in the predictability of atomic clocks in moving and stationary states is analyzed. The results show that: (1) in the moving state, the frequency stability of a hydrogen clock decreases by 1-2 orders of magnitude, and the frequency stability of a cesium clock decreases by 0.5 orders of magnitude; (2) in the recovery stage, the frequency stability of hydrogen and cesium clocks is between that in static and moving stages, but the frequency stability fluctuates greatly in this stage; (3) in the moving state, the three main noises of the atomic clock all increase, of which the increase in the white noise of phase modulation is the largest, indicating that it is the most sensitive to vibration and has the greatest impact on the frequency stability of the atomic clock during the moving period; (4) in the mobile state, the RMS of the prediction data of the hydrogen clock and cesium clock greatly increases compared with that in the static state.

Characterization of a Self-Sufficient Cytochrome P450 Monooxygenase from Deinococcus apachensis for Enantioselective Benzylic Hydroxylation.

A self-sufficient cytochrome P450 monooxygenase from Deinococcus apachensis (P450DA) was identified and successfully overexpressed in Escherichia coli BL21(DE3). P450DA would be a member of the CYP102D subfamily and assigned as CYP102D2 according to the phylogenetic tree and sequence alignment. Purification and characterization of the recombinant P450DA indicated both NADH and NADPH could be used by P450DA as a reducing cofactor. The recombinant E. coli (P450DA) strain was functionally active, showing excellent enantioselectivity for benzylic hydroxylation of methyl 2-phenylacetate. Further substrate scope studies revealed that P450DA is able to catalyze benzylic hydroxylation of a variety of compounds, affording the corresponding chiral benzylic alcohols in 86-99 % ee and 130-1020 total turnover numbers.

miRLocator: Machine Learning-Based Prediction of Mature MicroRNAs within Plant Pre-miRNA Sequences.

MicroRNAs (miRNAs) are a class of short, non-coding RNA that play regulatory roles in a wide variety of biological processes, such as plant growth and abiotic stress responses. Although several computational tools have been developed to identify primary miRNAs and precursor miRNAs (pre-miRNAs), very few provide the functionality of locating mature miRNAs within plant pre-miRNAs. This manuscript introduces a novel algorithm for predicting miRNAs named miRLocator, which is based on machine learning techniques and sequence and structural features extracted from miRNA:miRNA* duplexes. To address the class imbalance problem (few real miRNAs and a large number of pseudo miRNAs), the prediction models in miRLocator were optimized by considering critical (and often ignored) factors that can markedly affect the prediction accuracy of mature miRNAs, including the machine learning algorithm and the ratio between training positive and negative samples. Ten-fold cross-validation on 5854 experimentally validated miRNAs from 19 plant species showed that miRLocator performed better than the state-of-art miRNA predictor miRdup in locating mature miRNAs within plant pre-miRNAs. miRLocator will aid researchers interested in discovering miRNAs from model and non-model plant species.

Using multiple linear regression and physicochemical changes of amino acid mutations to predict antigenic variants of influenza A/H3N2 viruses.

Among human influenza viruses, strain A/H3N2 accounts for over a quarter of a million deaths annually. Antigenic variants of these viruses often render current vaccinations ineffective and lead to repeated infections. In this study, a computational model was developed to predict antigenic variants of the A/H3N2 strain. First, 18 critical antigenic amino acids in the hemagglutinin (HA) protein were recognized using a scoring method combining phi (ϕ) coefficient and information entropy. Next, a prediction model was developed by integrating multiple linear regression method with eight types of physicochemical changes in critical amino acid positions. When compared to other three known models, our prediction model achieved the best performance not only on the training dataset but also on the commonly-used testing dataset composed of 31878 antigenic relationships of the H3N2 influenza virus.

Induced effects of advanced oxidation processes.

Hazardous organic wastes from industrial, military, and commercial activities represent one of the greatest challenges to human beings. Advanced oxidation processes (AOPs) are alternatives to the degradation of those organic wastes. However, the knowledge about the exact mechanisms of AOPs is still incomplete. Here we report a phenomenon in the AOPs: induced effects, which is a common property of combustion reaction. Through analysis EDTA oxidation processes by Fenton and UV-Fenton system, the results indicate that, just like combustion, AOPs are typical induction reactions. One most compelling example is that pre-feeding easily oxidizable organic matter can promote the oxidation of refractory organic compound when it was treated by AOPs. Connecting AOPs to combustion, it is possible to achieve some helpful enlightenment from combustion to analyze, predict and understand AOPs. In addition, we assume that maybe other oxidation reactions also have induced effects, such as corrosion, aging and passivation. Muchmore research is necessary to reveal the possibilities of induced effects in those fields.

Inactivation of microorganisms in apple juice using an ultraviolet silica-fiber optical device.

Most juices are opaque to ultraviolet (UV) due to the high-suspended solids in them and therefore the conventional UV treatment, generally used for water treatment, cannot be used for treating juices. In order to achieve a high germicidal efficiency of UV processing, an optical device with silica optical fibers for UV light delivery was designed. Its suitability for application could be shown in experiments with Escherichia coli, Lactobacillus brevis, Saccharomyces cerevisiae and naturally contaminating microorganisms as test microorganisms. The thin-film thickness for treating apple juice was optimized. At 2.0-mm film thickness, E. coli and L. brevis were reduced by up to 6 log orders with the UV dose of 23.7 m J/cm(2) and the optical-fiber distribution density of 15 fibers/cm(2), while only about 4-log reduction of S. cerevisiae was achieved under the same condition. Naturally contaminating lactic acid bacteria, Enterobacteriaceae and yeasts and moulds in freshly extracted apple juice were reduced to below 10 CFU/ml. These results indicate that this optical device could be used to improve microbial safety and extend shelf-life of apple juice.

Solution-processed bulk-heterojunction photovoltaic cells based on dendritic and star-shaped D-pi-A organic dyes.

A series of D-pi-A organic dendritic and star-shaped molecules based on three various chromophores (i.e., the truxene nodes, triphenylamine moieties as the donor, and benzothiadiazole chromophore as the acceptor) and their corresponding model compounds are facilely developed. Their photophysical and electrochemical properties are investigated in detail by UV/Vis absorption and photoluminescent spectroscopy, and cyclic voltammetry. By changing the various conjugated spacers (i.e., single bond, double bond, and triple bond) among the three chromophores of dendritic series, their photophysical properties (that is, the one-photon absorption range and two-photon absorption cross-section values) are effectively modulated. All D-pi-A conjugated oligomers show a broad and strong absorption band from 250 to 700 nm in thin films. Solution-processed bulk-heterojunction photovoltaic devices using our oligomer as donor and PCBM as acceptor are fabricated and measured. The power conversion efficiency of the devices based on our oligomers continuously increases from DBTTr to TrTD2A as a result of an increasing relative absorption intensity in longer wavelength region by changing the donor-acceptor ratio and conjugated spacers between the donor and acceptor. The power conversion efficiency of the devices based on TrTD2A was 0.54% under the illumination of AM 1.5 and 100 mW cm(-2), which is the highest value recorded based on D-pi-A conjugated oligomers containing triphenylamine moieties and benzothiadiazole chromophores with truxene to date.

Uniform suspended nanorods fabricated by bidirectional scanning via two-photon photopolymerization.

Suspended nanorods fabricated by two-photon photopolymerization gradually thickened in the scanning direction when the scanning speed was faster than 60 µm s(-1). For a 2 µm long suspended nanorod, the lateral widths of the thin and the thick ends were about 50 and 150 nm. A bidirectional scanning technique was proposed to effectively eliminate the size difference, resulting in uniform suspended nanorods of 100 nm in width and 2 µm in length.