Magneto-optical spectroscopy of novel ferromagnetic materials

Two types of novel ferromagnetic materials, (Ga,Mn)As and Fei/4TaS2, were studied in this dissertation. Interest in (Ga,Mn)As is stimulated by the emerging field of spintronics, which has a potential of bringing a technology revolution in information processing, information storage, and quantum computing. The latter, Feu1/4TaS2, belongs to the family of intercalated transition-metal dichalcogenides (TMDC) with highly anisotropie layered structures. At cryogenic temperatures, ferromagnetic order appears in both materials through the interaction of localized spins and itinerant carriers. In order to investigate these underlying exchange interactions and spin-split band structures, we developed a magneto-optical Kerr effect (MOKE) spectrometer with the full capabilities of magnetic field, temperature, and photon energy scanning. We observed novel and unusual MOKE data as a function of these three continuously tunable parameters. Remanent Kerr angles of (Ga,Mn)As samples showed strong dependence on the photon energy, exhibiting a large positive peak at ∼ 1.7 eV. This peak increased in intensity and blue-shifted with Mn doping and further blue-shifted with annealing. We attribute these changes to the increased hole density and effective Mn content. Our data agree very well with theoretical calculations using a 30-band k · p model with antiferromagnetic p-d exchange interaction without any ad hoc introduction of impurity transitions. The agreement between the data and the model led us to conclude that above-bandgap magneto-optical Kerr rotation in ferromagnetic (Ga,Mn)As is determined by interband transitions. Fe1/4TaS2 exhibited abnormal Kerr hysteresis behavior with a strong sensitivity to the probing photon energy. The abnormal shapes can be fitted with the sum of two error functions, and we provide a tentative physical description based on domain wall physics. However, a few open questions remains, and its microscopic origin is still under investigation. The Kerr spectra were explained by the difference of joint-density-of-state (JDOS) of spin-up and spin-down bands in a simplified model, adopting literature DOS values of Fe1/3TaS2. Accurate simulations require future calculations of the band structure

Development and evaluation of an immunochromatographic strip test based on the recombinant UL51 protein for detecting antibody against duck enteritis virus

<p>Abstract</p> <p>Background</p> <p>Duck enteritis virus (DEV) infection causes substantial economic losses to the worldwide duck-producing areas. The monitoring of DEV-specific antibodies is a key to evaluate the effect of DEV vaccine and develop rational immunization programs. Thus, in this study, an immunochromatographic strip (ICS) test was developed for detecting DEV serum antibodies.</p> <p>Results</p> <p>The ICS test is based on membrane chromatography, and uses both the purified recombinant UL51 protein conjugated with colloidal gold and goat anti-rabbit IgG conjugated with colloidal gold as tracers, the purified recombinant UL51 protein as the capture reagent at the test line, and rabbit IgG as the capture reagent at the control line. The specificity of the ICS was evaluated by sera against DEV, Duck hepatitis virus (DHV), Riemerella anatipestifer (RA), Duck E. coli, Muscovy duck parvovirus (MPV), or Duck Influenza viruses (DIV). Only sera against DEV showed the strong positive results. In order to determine the sensitivity of the ICS, anti-DEV serum diluted serially was tested, and the minimum detection limit of 1:128 was obtained. The ICS components, which are provided in a sealed package, require no refrigeration and are stable for 12 months. To evaluate the effect of the ICS, 110 duck serum samples collected from several non-immune duck flocks were simultaneously tested by the ICS test, enzyme-linked immunosorbent assay (ELISA) and neutralization test (NT). The results showed that the sensitivity of the ICS test was almost consistent with ELISA and much higher than NT, has low cost, and is rapid (15 min) and easy to perform with no requirement of specialized equipment, reagent or technicians.</p> <p>Conclusions</p> <p>In this work, we successfully developed a simple and rapid ICS test for detecting DEV serum antibodies for the first time. The ICS test was high specific and sensitive for the rapid detection of anti-DEV antibodies, and has great potential to be used for the serological surveillance of DEV infection in the field.</p

GABAB Receptor Subunit GB1 at the Cell Surface Independently Activates ERK1/2 through IGF-1R Transactivation

BACKGROUND: Functional GABA(B) receptor is believed to require hetero-dimerization between GABA(B1) (GB1) and GABA(B2) (GB2) subunits. The GB1 extracellular domain is required for ligand binding, and the GB2 trans-membrane domain is responsible for coupling to G proteins. Atypical GABA(B) receptor responses observed in GB2-deficient mice suggested that GB1 may have activity in the absence of GB2. However the underlying mechanisms remain poorly characterized. METHODOLOGY/PRINCIPAL FINDINGS: Here, by using cells overexpressing a GB1 mutant (GB1asa) with the ability to translocate to the cell surface in the absence of GB2, we show that GABA(B) receptor agonists, such as GABA and Baclofen, can induce ERK1/2 phosphorylation in the absence of GB2. Furthermore, we demonstrate that GB1asa induces ERK1/2 phosphorylation through Gi/o proteins and PLC dependent IGF-1R transactivation. CONCLUSIONS/SIGNIFICANCE: Our data suggest that GB1 may form a functional receptor at the cell surface in the absence of GB2

Prediction of household dust mite concentration based on machine learning algorithm

Household dust mites (HDMs) are the important allergens causing allergic diseases in children. A predictive model can help us understand the concentration of HDMs in different areas of China to better prevent and control this kind of allergen. This study used 454 household inspection samples in childrens’ room obtained from China, Children, Homes, Health (CCHH) phase 2 study, conducted during 2013-2014. Spearman correlation and multiple logistic regression were used to explore the influencing factors of HDMs concentrations, by comprehensively considering residents’ lifestyle, building characteristics, environmental exposure, especially dampness-related exposures. This study used the Gradient Boosting Decision Tree(GBDT) algorithm to build the prediction model. The data from CCHH were used to established the prediction model. It was found that there were some differences in the influencing factors between two types of HDMs. The concentration of HDMs were found a significant correlation (p0. 9). This paper provides a reference for predicting the HDMs concentrations in children's bedrooms and the influence of the influencing factors

Characteristic and Concentration Distribution of Culturable Airborne Bacteria in Residential Environments in Beijing, China

The present investigation was conducted to assess the culturable concentration and distribution characteristics of airborne bacteria in 31 homes with children aged from 1 to 10 years in Beijing, China. The results showed that the concentration of culturable airborne bacteria in these homes ranged from 47 colony forming units (CFU)/m(3) to 12341 CFU/m(3), with a mean and a median of 1821 and 877 CFU/m3, respectively. A total of 632 bacterial isolates from the air in homes in different regions and different seasons were identified and distributed across 43 genera and 136 species of bacteria. Micrococcus (26.74%), Bacillus (14.56%), Kocuria (12.66%), and Staphylococcus (12.03%) were determined as the most common culturable airborne bacteria, and the dominant bacterial species were Micrococcus luteus (14.56%), Kocuria roseus (8.39%), Bacillus megaterium (4.75%), Staphylococcus cohnii (3.63%), and Micrococcus lylae (3.01%). Data analysis revealed that bacterial concentrations in homes with a male child were significantly higher than those with a female child (**P < 0.01), and a negative correlation was found between bacterial concentration and living area per person in the homes (**P < 0.01). Additionally, the mean bacterial concentration was highest in Spring, followed by Summer and Autumn, and lowest in Winter (**P < 0.01) in homes with child. The results provide an exposure database of airborne bacteria in family homes in Beijing, and suggest that the sex of children and living area per person in homes have a significant influence on the bacterial concentration in the air

Hierarchically porous N-doped carbon framework with enlarged interlayer spacing as dual-carbon electrodes for potassium ion hybrid capacitors

Abstract Thanks to the high power/energy densities together with lower cost, potassium ion hybrid capacitors (PIHCs) have broad application prospects. Nevertheless, the significant volume changes during K+ intercalation/deintercalation together with the misfit between anode as well as cathode limit their further development. Herein, hierarchically porous nitrogen-doped carbon (N-HPC) is fabricated and used as two electrodes materials for PIHCs. The three-dimensional hierarchical porous structure and large interlayer distance of N-HPC afford enough space to alleviate the volume expansion of potassium. Furthermore, the suitable N doping enables additional active sites towards K+ storage and improves electrical conductivity of electrodes. Hence, the constructed PIHCs assembled with dual N-HPC electrodes deliver a high energy density of 103.5 Wh kg‒1 at 1000.0 W kg‒1. Meanwhile, the PIHCs devices also display superior cycling stability, achieving a capacity retention rate of 70.2% after 10,000 cycles at 1.0 A g‒1. Graphical Abstract Hierarchically porous nitrogen-doped carbon (N-HPC) is fabricated and used as two electrode materials for PIHCs. The three-dimensional porous structure of N-HPC, the larger inter-layer distance, and the synergy of N-doped introduction of more active sites make it have good magnification properties. At the same time, the assembled PIHCs cycle of 10000 laps has an excellent cycle retention rate

The gradient-boosting decision tree model can predict the concentration of PAEs in children bedroom

Exposure of phthalate has adverse effects on child health. Currently, the field measurement on PAEs concentration in children’s bedrooms were limited, and the test of PAEs is laborious. Based on the data of home detection in 454 residences from March 2013 to December 2014 in Shanghai, the association of PAEs in children's bedroom and building characteristics, residents’ lifestyle and indoor environment characterization were built by Spearman correlation. According to the Spearman correlation coefficient method, the concentration of PAEs, such as residential area was significantly correlated with DMP, BBP and DiBP in children’s bedroom (sig 0), and the use of chemicals was significantly associated with DEP and DiBP in children’s bedroom (sig 0). Then a gradient-boosting decision tree model with higher prediction accuracy is established. The influencing factors of the studied PAEs were determined by comprehensive consideration of the current study and literature review. 11 influencing factors of PAEs concentrations from three aspects were finally established in this study. The training model of GBDT has a reasonable accuracy( R2>0.9). This paper provides a reference for the prediction of PAEs concentration in the residential bedroom and the influence degree of influencing factors