10 research outputs found
Oxygen and hydrogen sulfide concentration of Nootka Sound bottom water
No full textSenior thesis written for Oceanography 445[author abstract] Nootka Sound is a narrow fjord located at the west side of the Vancouver Island that have little investigation been done. It has a large sill that could potentially trap ocean water. Along with steep salinity and other geological reasons, Nootka Sound is susceptible to oxygen depletion in water, which is detrimental to benthic communities and fisheries. In this study, oxygen concentrations were measured with oxygen probe on CTD instrument. Oxygen data was calibrated with titration of water sample from CTD, with Winkler Method. Water samples was analyzed to show its nutrient concentration, specifically nitrate, nitrite and ammonia concentrations. Results shows that at the time of the study, water below 350 meters in depth is oxygen depleted. At one of the station, water sample had a strong rotten egg smell, which means there was a lot of dissolved hydrogen sulfide. Hydrogen sulfide is a great indicator of sulfate reduction, which only happens when no oxygen and nitrate exists. The condition of Muchalat Inlet is similar to Sannich Inlet and Hood Canal in terms of the mechanisms that causes oxygen depletion.University of Washington School of Oceanograph
Time Resolved Fluorescence Studies of Genetically Encoded Protein Sensor Frex for Nadh and pH Levels
No full textUsing Fractional Intensities of Time-resolved Fluorescence to Sensitively Quantify NADH/NAD+ with Genetically Encoded Fluorescent Biosensors
No full textAbstractIn this paper, we propose a novel and sensitive ratiometric analysis method that uses the fractional intensities of time-resolved fluorescence of genetically encoded fluorescent NADH/NAD+ biosensors, Peredox, SoNar, and Frex. When the conformations of the biosensors change upon NADH/NAD+ binding, the fractional intensities (α
i
τ
i
) have opposite changing trends. Their ratios could be exploited to quantify NADH/NAD+ levels with a larger dynamic range and higher resolution versus commonly used fluorescence intensity and lifetime methods. Moreover, only one excitation and one emission wavelength are required for this ratiometric measurement. This eliminates problems of traditional excitation-ratiometric and emission-ratiometric methods. This method could be used to simplify the design and achieve highly sensitive analyte quantification of genetically encoded fluorescent biosensors. Wide potential applications could be developed for imaging live cell metabolism based on this new method.</jats:p
Main Group SnN4O Single Sites with Optimized Charge Distribution for Boosting the Oxygen Reduction Reaction
No full textTransition metal single-atom catalysts (SACs) have been regarded as possible alternatives to platinum-based materials due to their satisfactory performance of the oxygen reduction reaction (ORR). By contrast, main-group metal elements are rarely studied due to their unfavorable surface and electronic states. Herein, a main-group Sn-based SAC with penta-coordinated and asymmetric first-shell ligands is reported as an efficient and robust ORR catalyst. The introduction of the vertical oxygen atom breaks the symmetric charge balance, modulating the binding strength to oxygen intermediates and decreasing the energy barrier for the ORR process. As expected, the prepared Sn SAC exhibits outstanding ORR activity with a high half-wave potential of 0.912 V (vs RHE) and an excellent mass activity of 13.1 A mgSn–1 at 0.850 V (vs RHE), which surpasses that of commercial Pt/C and most reported transition-metal-based SACs. Additionally, the reported Sn SAC shows excellent ORR stability due to the strong interaction between Sn sites and the carbon support with oxygen atom as the bridge. The excellent ORR performance of Sn SAC was also proven by both liquid- and solid-state zinc–air battery (ZAB) measurements, indicating its great potential in practical applications.補正完畢US
The phosphorescence and excitation-wavelength dependent fluorescence kinetics of large-scale graphene oxide nanosheets
No full textNational Science Foundation of China [61108077, 61178085, 61008003, 61275147]; Key Project of Science and Technology of Shandong Province of China [2010GGX10127]; Shandong Province Natural Science Foundation of China [ZR2012AL11, ZR2013EML006]In this study, phosphorescence emission and a strong excitation-wavelength dependent fluorescence has been found in large-scale graphene oxide (GO) nanosheets. GO was covalently functionalized with triphenylamine (GO-CONH-TPA) in order to enhance the GO fluorescence quantum yield to 18%. The intersystem crossing (ISC) dynamics were studied using a femtosecond transient absorption technique, which appeared in the same timescale as the fluorescence dynamics of GO-CONH-TPA in both a polar solvent and solid film. Therefore, both, the solvation (several hundreds of picoseconds) and the intersystem crossing (ISC) gave rise to the strong excitation-wavelength dependent fluorescence. Moreover, the phosphorescence emission of the GO-CONH-TPA film at room temperature has been described for the first time in this report, and the lifetime of phosphorescence was found to be 6.95 ms. The fluorescence kinetics of GO-CONH-TPA were attributed to the aromatic hydrocarbon-carboxylic domain structure of GO
Levels and potential health hazards of PCBs in shallow groundwater of an e-waste recycling area, China
No full textThe improper disassembly of polychlorinated biphenyl (PCB)-containing equipments such as capacitor and electrical transformer can lead to PCB pollution. To investigate the levels and patterns of PCBs in shallow groundwater in regions where PCB-containing equipment is disassembled, 19 shallow groundwater samples were collected from a recycling area for waste capacitors and electrical transformers in southeastern China. The I 21 pound PCBs in shallow groundwater had a large variation ranging from 6.22 to 97.3 ng L-1, with a mean of 31.6 ng L-1 and low chlorinated PCBs (3-5 chlorinated biphenyls) were predominant homologs in majority groundwater samples. The United States Environmental Protection Agency (US EPA) toxic equivalents of 6 shallow groundwater samples with detectable dioxin-like PCBs varied greatly from 0.29 to 650 pg L-1, and all of them posing serious cancer risk (> 1 x 10(-6)) to children and adults. Much attention should be paid to the vertical migration of low chlorinated PCBs and the cancer risk of dioxin-like PCBs in the study area and similar e-waste recycling areas.The improper disassembly of polychlorinated biphenyl (PCB)-containing equipments such as capacitor and electrical transformer can lead to PCB pollution. To investigate the levels and patterns of PCBs in shallow groundwater in regions where PCB-containing equipment is disassembled, 19 shallow groundwater samples were collected from a recycling area for waste capacitors and electrical transformers in southeastern China. The I 21 pound PCBs in shallow groundwater had a large variation ranging from 6.22 to 97.3 ng L-1, with a mean of 31.6 ng L-1 and low chlorinated PCBs (3-5 chlorinated biphenyls) were predominant homologs in majority groundwater samples. The United States Environmental Protection Agency (US EPA) toxic equivalents of 6 shallow groundwater samples with detectable dioxin-like PCBs varied greatly from 0.29 to 650 pg L-1, and all of them posing serious cancer risk (> 1 x 10(-6)) to children and adults. Much attention should be paid to the vertical migration of low chlorinated PCBs and the cancer risk of dioxin-like PCBs in the study area and similar e-waste recycling areas
Determination of low levels of polycyclic aromatic hydrocarbons in soil by high performance liquid chromatography with tandem fluorescence and diode-array detectors
No full textRisk assessment of polycyclic aromatic hydrocarbons (PAHs) contaminated soil and source apportionment require accurate analysis of the concentration of each PAH congener in the soil. However, determination of low level PAH congeners in soil is difficult because of similarity in the chemical properties of 16 PAHs and severe matrix interferences due to complex composition of soils. It is therefore imperative to develop a sensitive and accurate method for determination of low level PAHs in soil. In this work, high performance liquid chromatography equipped with fluorescence and diode-array detectors (HPLC-FLD-DAD) was used to determine the concentration of 16 PAHs in soil. The separation of the 16 PAHs was achieved by optimization of the mobile phase gradient elution program and FLD wavelength switching program. Qualitative analysis of the 16 PM-Is was based on the retention time (RT) and each PAH specific spectrum obtained from DAD. In contrast, the quantitative analysis of individual PAH congeners was based on the peak areas at the specific wavelength with DAD and FLD. Under optimal conditions the detection limit was in the range 1.0-9.5 mu g L-1 for 16 PAHs with DAD and 0.01-0.1 mu g L-1 for 15 PAHs with FLD, and the RSD of PAHs was less than 5% with DAD and 3% with FLD. The spiked recoveries were in the range 61-96%, with the exception of NaP (<40%). The results show that HPLC-FLD-DAD can provide more accurate and reliable analysis of low level PAH congeners in soil samples. (C) 2013 Elsevier Ltd. All rights reserved
Sensitive Detection of Polycyclic Aromatic Molecules: Surface Enhanced Raman Scattering via π–π Stacking
No full textWe report silver nanoparticles (Ag
NPs) with high stability, sensitivity,
and no surface enhanced Raman scattering (SERS) background. The Ag
NPs were synthesized via a one-step process with polysodium styrenesulfonate
(PSSS) templates, and they could efficiently adsorb polycyclic aromatic
molecules via π–π stacking. The adsorption mechanisms
and applicability were systematically studied by experimental measurements
and theoretical simulations. When the polycyclic aromatic analytes
were adsorbed on the PSSS-templated Ag NPs, the vibrations of π–π
stacking-bound moieties were attenuated, yet those of the other unbound
aromatic moieties increased. Most importantly, when the analytes had
more than two π–π stacking binding sites, the PSSS-templated
Ag NPs could trap the analytes by focusing through the optical force
induced or via the simultaneously formed analyte–Ag NPs aggregates.
This afforded high SERS intensity and very low detection limits
Factors associated with menopausal symptoms among middle-aged registered nurses in Beijing
No full textObjective: To determine factors related to menopause symptoms among middle-aged registered nurses in Beijing. Methods: Self-administered questionnaires that included closed-ended questions on many factors possibly related to menopausal symptoms were distributed to 2100 registered nurses aged 40-55 at 20 hospitals in Beijing, China. Results: Menopausal status was most associated with menopausal symptoms (p < 0.01), including hot flashes and sweating, paresthesiae, insomnia, arthralgia/myalgia, palpitations, skin formication and an unsatisfactory sexual life. The odds ratios (ORs) were highest for hot flashes and sweating. Upsetting events in the past year and being pessimistic were significantly inversely correlated with almost all the symptoms analyzed. Hot flashes and sweating (p < 0.01), paresthesiae (p < 0.01), unsatisfactory sexual life (p < 0.01), irritability (p < 0.05), depression or suspicion (p < 0.05) and dizziness (p < 0.05) were negatively correlated with the frequency of sexual activity. Conclusion: Many factors may influence symptoms of the menopause. We found that menopausal status was most strongly associated with most menopausal symptoms, especially hot flashes and sweating. Psychosocial factors also played an important role. A higher frequency of sexual activity negatively correlated with most menopausal symptoms.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000348205900008&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Endocrinology & MetabolismObstetrics & GynecologySCI(E)[email protected]; [email protected]
