33 research outputs found

    A Nanonet-Enabled Li Ion Battery Cathode Material with High Power Rate, High Capacity, and Long Cycle Lifetime

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    The performance of advanced energy conversion and storage devices, including solar cells and batteries, is intimately connected to the electrode designs at the nanoscale. Consider a rechargeable Li ion battery, a prevalent energy storage technology, as an example. Among other factors, the electrode material design at the nanoscale is key to realizing the goal of measuring fast ionic diffusion and high electronic conductivity, the inherent properties that determine power rates, and good stability upon repeated charge and discharge, which is critical to the sustainable high capacities. Here we show that such a goal can be achieved by forming heteronanostructures on a radically new platform we discovered, TiSi<sub>2</sub> nanonets. In addition to the benefits of high surface area, good electrical conductivity, and superb mechanical strength offered by the nanonet, the design also takes advantage of how TiSi<sub>2</sub> reacts with O<sub>2</sub> upon heating. The resulting TiSi<sub>2</sub>/V<sub>2</sub>O<sub>5</sub> nanostructures exhibit a specific capacity of 350 Ah/kg, a power rate up to 14.5 kW/kg, and 78.7% capacity retention after 9800 cycles of charge and discharge. These figures indicate that a cathode material significantly better than V<sub>2</sub>O<sub>5</sub> of other morphologies is produced

    Self-care behaviors among patients who were aware of their hypertension in Beijing from 2005 to 2011.

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    <p>* Significant at <i>P</i> < 0.05.</p><p><sup>a</sup> Significant difference between genders within urban patients or suburban patients.</p><p><sup>b</sup> Significant difference between urban patients and suburban patients for each gender.</p><p><sup>c</sup> Cochran-Armitage trend test for each gender by urban or suburban group.</p><p><sup>d</sup> SE Standard error.</p><p>Self-care behaviors among patients who were aware of their hypertension in Beijing from 2005 to 2011.</p

    Functionalizing Titanium Disilicide Nanonets with Cobalt Oxide and Palladium for Stable Li Oxygen Battery Operations

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    Li oxygen (Li–O<sub>2</sub>) batteries promise high energy densities but suffer from challenges such as poor cycling lifetime and low round-trip efficiencies. Recently, the instability of carbon cathode support has been recognized to contribute significantly to the problems faced by Li–O<sub>2</sub> batteries. One strategy to address the challenge is to replace carbon materials with carbon-free ones. Here, we present titanium silicide nanonets (TiSi<sub>2</sub>) as such a new material platform for this purpose. Because TiSi<sub>2</sub> exhibits no oxygen reduction reaction (ORR) or oxygen evolution reaction (OER) activities, catalysts are required to promote discharge and recharge reactions at reduced overpotentials. Pd nanoparticles grown by atomic layer deposition (ALD) were observed to provide the bifunctionalities of ORR and OER. Their adhesion to TiSi<sub>2</sub> nanonets, however, was found to be poor, leading to drastic performance decay due to Pd detachments and aggregation. The problem was solved by adding another layer of Co<sub>3</sub>O<sub>4</sub>, also prepared by ALD. Together, the Pd/Co<sub>3</sub>O<sub>4</sub>/TiSi<sub>2</sub> combination affords the desired functionalities and stability. Li–O<sub>2</sub> test cells that lasted more than 126 cycles were achieved. The reversible formation and decomposition of Li<sub>2</sub>O<sub>2</sub> was verified by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), ferrocenium back-titration, and gas-chromatography and mass spectrometry (GC-MS). Our results provide a new material platform for detailed studies of Li–O<sub>2</sub> operations for better understanding of the chemistries involved, which is expected to help pave the way toward practical Li–O<sub>2</sub> battery realizations

    Prevalence, awareness, and control of hypertension among adults in Beijing from 2005 to 2011.

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    <p>* Significant at <i>P</i> < 0.05.</p><p><sup>a</sup> Significant difference between suburban population and urban population within each survey.</p><p><sup>b</sup> Cochran-Armitage trend test for overall prevalence.</p><p><sup>c</sup> Cochran-Armitage trend test for prevalence within suburban participants or urban participants.</p><p><sup>d</sup> SE Standard error.</p><p><sup>e</sup> 298 participants with missing BP values were excluded.</p><p><sup>s</sup> Age and gender adjusted using the total population (n = 58985).</p><p>Prevalence, awareness, and control of hypertension among adults in Beijing from 2005 to 2011.</p

    Urban and Suburban Differences in Hypertension Trends and Self-Care: Three Population-Based Cross-Sectional Studies from 2005-2011

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    <div><p>Objectives</p><p>This study aimed to compare hypertension trends in the urban and suburban population, and to examine the use of several self-care behaviors among patients who were aware of their hypertension.</p><p>Methods</p><p>We examined the data from three cross-sectional adult populations obtained in 2005, 2008, and 2011, in Beijing.</p><p>Results</p><p>Our analyses indicated that from 2005 to 2011 the standardized rate of hypertension increased from 31.9% to 36.0% (<i>P</i> <0.001) among urban adults, and was relatively stable (40.8% -40.2%) among suburban adults (<i>P</i> = 0.02). About 10% of the patients reported having taken measures to control their weight for hypertension management. As compared to the other patients, the female patients in the urban areas reported the highest rate of regular BP measurement (52.6%). In addition, the patients who reported taking medication regularly increased among the males and females. Most of the women reported nonsmoking (≥95%) and alcohol abstinence (≥90%). The trend of nonsmoking decreased among the urban males. In contrast, the prevalence of nonsmoking increased among the suburban males, though the trend was not statistically significant (<i>P</i> = 0.055). Further, the patient-reported alcohol abstinence was found to exhibit a decreasing trend among the males.</p><p>Conclusions</p><p>We observed an increase in the hypertension prevalence from 2005 to 2011. The rates remained higher for suburban adults than for urban adults. Females generally had better self-care ability as compared to male patients. Further research is needed to promote self-care behaviors in hypertensive patients, especially for male patients.</p></div

    Characteristics of study participants in Beijing from 2005 to 2011.

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    <p>* Significant at <i>P</i> < 0.05.</p><p><sup>a</sup> Significant difference between suburban population and urban population within each survey.</p><p><sup>b</sup> Cochran-Armitage trend test for overall prevalence</p><p><sup>c</sup> Cochran-Armitage trend test for prevalence within suburban participants or urban participants</p><p>- Data were not available.</p><p><sup>d</sup> SE Standard error</p><p>Characteristics of study participants in Beijing from 2005 to 2011.</p

    Site-Selective Deposition of Twinned Platinum Nanoparticles on TiSi<sub>2</sub> Nanonets by Atomic Layer Deposition and Their Oxygen Reduction Activities

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    For many electrochemical reactions such as oxygen reduction, catalysts are of critical importance, as they are often necessary to reduce reaction overpotentials. To fulfill the promises held by catalysts, a well-defined charge transport pathway is indispensable. Presently, porous carbon is most commonly used for this purpose, the application of which has been recently recognized to be a potential source of concern. To meet this challenge, here we present the development of a catalyst system without the need for carbon. Instead, we focused on a conductive, two-dimensional material of a TiSi<sub>2</sub> nanonet, which is also of high surface area. As a proof-of-concept, we grew Pt nanoparticles onto TiSi<sub>2</sub> by atomic layer deposition. Surprisingly, the growth exhibited a unique selectivity, with Pt deposited only on the top/bottom surfaces of the nanonets at the nanoscale without mask or patterning. Pt {111} surfaces are preferably exposed as a result of a multiple-twinning effect. The materials showed great promise in catalyzing oxygen reduction reactions, which is one of the key challenges in both fuel cells and metal air batteries

    Visible-Light-Promoted Radical C–H Trifluoromethylation of Free Anilines

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    The trifluoromethyl-substituted anilines are biologically active compounds and useful building blocks. In this communication, we have developed the first visible-light-induced radical tri­fluoro­methyla­tion of free anilines with the commercially available and easily handled Togni reagent at room temperature. The resulting products were successfully transformed into a variety of valuable fluorine-containing molecules and heterocyclic compounds. This protocol provides an economical and powerful route to trifluoromethylated free anilines
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