On-the-fly machine learning for parametrization of the effective Hamiltonian

The first-principles-based effective Hamiltonian is widely used to predict and simulate the properties of ferroelectrics and relaxor ferroelectrics. However, the parametrization method of the effective Hamiltonian is complicated and hardly can resolve the systems with complex interactions and/or complex components. Here, we developed an on-the-fly machine learning approach to parametrize the effective Hamiltonian based on Bayesian linear regression. The parametrization is completed in molecular dynamics simulations, with the energy, forces and stress predicted at each step along with their uncertainties. First-principles calculations are executed when the uncertainties are large to retrain the parameters. This approach provides a universal and automatic way to compute the effective Hamiltonian parameters for any considered systems including complex systems which previous methods can not handle. BaTiO3 and Pb(Sc,Ta)O3 are taken as examples to show the accurateness of this approach comparing with conventional first-principles parametrization method.Comment: 11 pages, 2 figure

Experimental demonstrations of high-Q superconducting coplanar waveguide resonators

We designed and successfully fabricated an absorption-type of superconducting coplanar waveguide (CPW) resonators. The resonators are made from a Niobium film (about 160 nm thick) on a high-resistance Si substrate, and each resonator is fabricated as a meandered quarter-wavelength transmission line (one end shorts to the ground and another end is capacitively coupled to a through feedline). With a vector network analyzer we measured the transmissions of the applied microwave through the resonators at ultra-low temperature (e.g., at 20 mK), and found that their loaded quality factors are significantly high, i.e., up to 10^6. With the temperature increases slowly from the base temperature (i.e., 20 mK), we observed the resonance frequencies of the resonators are blue shifted and the quality factors are lowered slightly. In principle, this type of CPW-device can integrate a series of resonators with a common feedline, making it a promising candidate of either the data bus for coupling the distant solid-state qubits or the sensitive detector of single photons.Comment: Accepted by Chinese Science Bulleti

Spectrum of malignancies among the population of adults living with HIV infection in China: A nationwide follow-up study, 2008-2011.

BackgroundAlthough increasingly studied in high-income countries, there is a paucity of data from the Chinese population on the patterns of cancer among people living with HIV (PLHIV).MethodsWe conducted a nationwide follow-up study using routinely collected data for adult PLHIV diagnosed on or before 31 December 2011 and alive and in care as of 1 January 2008. Participants were observed from 1 January 2008 (study start) to 30 June 2012 (study end). Main outcome measures were gender-stratified age-standardized incidence rates for China (ASIRC) and standardized incidence ratios (SIR) for all malignancy types/sites observed.ResultsAmong 399,451 subjects, a majority was aged 30-44 years (49.3%), male (69.8%), and Han Chinese (67.9%). A total of 3,819 reports of cancer were identified. Overall, ASIRC was 776.4 per 100,000 for males and 486.5 per 100,000 for females. Malignancy sites/types with highest ASIRC among males were lung (226.0 per 100,000), liver (145.7 per 100,000), and lymphoma (63.1 per 100,000), and among females were lung (66.8 per 100,000), lymphoma (48.0 per 100,000), stomach (47.8 per 100,000), and cervix (47.6 per 100,000). Overall SIR for males was 3.4 and for females was 2.6. Highest SIR was observed for Kaposi sarcoma (2,639.8 for males, 1,593.5 for females) and lymphoma (13.9 for males, 16.0 for females).ConclusionsThese results provide evidence of substantial AIDS-defining and non-AIDS-defining cancer burden among adult Chinese PLHIV between 2008 and 2011. Although further study is warranted, China should take action to improve cancer screening, diagnosis, and treatment for this vulnerable population

Toxicological responses in alfalfa (Medicago sativa) under joint stress of cadmium and napropamide

Joint effects of Cd2+ and napropamide in seeds, roots or leaves of alfalfa were investigated under different treatments. It was shown that single stress of Cd2+ or napropamide decreased chlorophyll content after 30 days of treatment in different concentrations. The decrease in chlorophyll content became insignificant under joint stress of Cd2+ and napropamide. It can be concluded that the interaction of Cd2+ and napropamide would aggravate the toxic effects on chlorophyll synthesis in leaves of alfalfa. The joint effect of Cd2+ and napropamide was markedly significant (p < 0.05) on the change of SP content in leaves in all treatment. Moreover, Cd2+ and napropamide mixture exposure can increase lignin content and present synergistic effect. In a mixture treated with Cd2+ and napropamide, 52% decrease in β-carotene content contrasted with the control in young leaves. The contents of protein thiols and non-protein thiols in the roots of alfalfa were significantly increased by Cd2+ treatment in all treatment levels. In contrast, increasing napropamide supply did not have any significant effect on the protein thiols and non-protein thiols content. The Cd2+ induced accumulation of O2•- in seeds could be increased by treatment with different Cd2+ concentration. Production of H2O2 and O2•- was also higher in the napropamide treatments than in the control. The addition of napropamide significantly increased the H2O2 and O2•- level in the seeds of alfalfa.Key words: Alfalfa, joint stress, cadmium, napropamide

Negative electrocaloric effect in nonpolar phases of perovskite over wide range of temperature

The electrocaloric effect (ECE) offers a promising alternative to the traditional gas compressing refrigeration due to its high efficiency and environmental friendliness. The unusual negative electrocaloric effect refers to the adiabatic temperature drops due to application of electric field, in contrast with the normal (positive) ECE, and provides ways to improve the electrocaloric efficiency in refrigeration cycles. However, negative ECE is unusual and requires a clear understanding of microscopic mechanisms. Here, we found unexpected and extensive negative ECE in nonpolar orthorhombic, tetragonal, and cubic phases of halide and oxide perovskite at wide range of temperature by means of first-principle-based large scale Monte Carlo methods. Such unexpected negative ECE originates from the octahedral tilting related entropy change rather than the polarization entropy change under the application of electric field. Furthermore, a giant negative ECE with temperature change of 8.6 K is found at room temperature. This giant and extensive negative ECE in perovskite opens up new horizon in the research of caloric effects and broadens the electrocaloric refrigeration ways with high efficiency.Comment: 11 pages, 7 figure

Validation of internal control for gene expression study in soybean by quantitative real-time PCR

<p>Abstract</p> <p>Background</p> <p>Normalizing to housekeeping gene (HKG) can make results from quantitative real-time PCR (qRT-PCR) more reliable. Recent studies have shown that no single HKG is universal for all experiments. Thus, a suitable HKG should be selected before its use. Only a few studies on HKGs have been done in plants, and none in soybean, an economically important crop. Therefore, the present study was conducted to identify suitable HKG(s) for normalization of gene expression in soybean.</p> <p>Results</p> <p>All ten HKGs displayed a wide range of Ct values in 21 sample pools, confirming that they were variably expressed. GeNorm was used to determine the expression stability of the HGKs in seven series sets. For all the sample pools analyzed, the stability rank was <it>ELF1B</it>, <it>CYP2 </it>> <it>ACT11 </it>> <it>TUA </it>> <it>ELF1A </it>> <it>UBC2 </it>> <it>ACT2/7 </it>> <it>TUB </it>> <it>G6PD </it>> <it>UBQ10</it>. For different tissues under the same developmental stage, the rank was <it>ELF1B</it>, <it>CYP2 </it>> <it>ACT2/7 </it>> <it>UBC2 </it>> <it>TUA </it>> <it>ELF1A </it>> <it>ACT11 </it>> <it>TUB </it>> <it>G6PD </it>> <it>UBQ10</it>. For the developmental stage series, the stability rank was <it>ACT2/7</it>, <it>TUA </it>> <it>ELF1A </it>> <it>UBC2 </it>> <it>ELF1B </it>> <it>TUB </it>> <it>CYP2 </it>> <it>ACT11 </it>> <it>G6PD </it>> <it>UBQ10</it>. For photoperiodic treatments, the rank was <it>ACT11</it>, <it>ELF1B </it>> <it>CYP2 </it>> <it>TUA </it>> <it>ELF1A </it>> <it>UBC2 </it>> <it>ACT2/7 </it>> <it>TUB </it>> <it>G6PD </it>> <it>UBQ10</it>. For different times of the day, the rank was <it>ELF1A</it>, <it>TUA </it>> <it>ELF1B </it>> <it>G6PD </it>> <it>CYP2 </it>> <it>ACT11 </it>> <it>ACT2/7 </it>> <it>TUB </it>> <it>UBC2 </it>> <it>UBQ10</it>. For different cultivars and leaves on different nodes of the main stem, the ten HKGs' stability did not differ significantly. ΔCt approach and 'Stability index' were also used to analyze the expression stability in all 21 sample pools. Results from ΔCt approach and geNorm indicated that <it>ELF1B </it>and <it>CYP2 </it>were the most stable HKGs, and <it>UBQ10 </it>and <it>G6PD </it>the most variable ones. Results from 'Stability index' analysis were different, with <it>ACT11 </it>and <it>CYP2 </it>being the most stable HKGs, and <it>ELF1A </it>and <it>TUA </it>the most variable ones.</p> <p>Conclusion</p> <p>Our data suggests that HKGs are expressed variably in soybean. Based on the results from geNorm and ΔCt analysis, <it>ELF1B </it>and <it>CYP2 </it>could be used as internal controls to normalize gene expression in soybean, while <it>UBQ10 </it>and <it>G6PD </it>should be avoided. To achieve accurate results, some conditions may require more than one HKG to be used for normalization.</p

Influence of EOM sideband modulation noise on space-borne gravitational wave detection

Clock noise is one of the dominant noises in the space-borne gravitational wave (GW) detection. To suppress this noise, the clock noise-calibrated time-delay-interferometry (TDI) technique is proposed. In this technique, an inter-spacecraft clock tone transfer chain is necessary to obtain the comparison information of the clock noises in two spacecraft, during which an electro-optic-modulator (EOM) is critical and used to modulate the clock noise to the laser phase. Since the EOM sideband modulation process introduces modulation noise, it is significant to put forward the corresponding requirements and assess whether the commercial EOM meets. In this work, based on the typical Michelson TDI algorithm and the fundamental noise requirement of GW detectors, the analytic expression of the modulation noise requirement is strictly derived, which relax the component indicator need compared to the existing commonly used rough assessments. Furthermore, a commercial EOM (iXblue-NIR-10 GHz) is tested, and the experimental results show that it can meet the requirement of the typical GW detection mission LISA in whole scientific bandwidth by taking the optimal combination of the data stream. Even when the displacement measurement accuracy of LISA is improved to 1 pm/ $\mathrm{Hz^{1/2}}$ in the future, it still meets the demand