Automated online preconcentration system for the determination of trace amounts of lead using Pb-selective resin and inductively coupled plasma-atomic emission spectrometry

An automated sequential-injection online preconcentration system was developed for the determination of lead by inductively coupled plasma - atomic emission spectrometry (ICP-AES). The preconcentration of lead was performed with a minicolumn containing a lead-selective resin, Analig Pb-01, which was installed between a selection and a switching valve. In an acidic condition ( pH 1), lead could be adsorbed on the resin. The concentrated lead was afterward eluted with 25 mu L of 0.06 M nitrilotriacetic acid (NTA) solution ( pH 9) and was subsequently transported into the nebulizer of ICP-AES for quantification. The selectivity of the resin toward lead was examined using a solution containing a mixture of 61 elements. When a sample volume of 5 mL was used, the quantitative collection of lead ( &#62;= 97%) was achieved, along with an enrichment factor of 19, a sampling frequency of 12 samples hr(-1), a detection limit of 70 pg mL(-1), and a lowest quantification limit of 100 pg mL(-1). The linear dynamic range was 0.1 to 5 ng mL(-1), and the relative standard deviation (n = 9) was 0.5% at a 5 ng mL(-1) Pb level. The detection limit of 30 pg mL(-1) and lowest quantification limit of 50 pg mL(-1) could be achieved when 10 mL of sample volume was used. The accuracy of the proposed method was validated by determining lead in the standard reference material of river water (SLRS-4), and its applicability to the determination of lead in environmental river water samples was demonstrated.</p

Hydrogen content in doped and undoped BaPrO3 and BaCeO3 by cold neutron prompt-gamma activation analysis

Proton uptake in undoped and Y-doped BaPrO3 has been measured by cold neutron prompt-gamma activation analysis, and compared to the proton uptake in Gd-doped BaCeO3, as determined by the same technique. The conventional proton incorporation model of perovskites in which oxygen ion vacancies, generated by the introduction of the trivalent dopant onto the tetravalent perovskite site, are filled with hydroxyl groups upon exposure of the sample to H2O containing atmospheres, predicts that the proton concentration in such materials should be no greater than the dopant concentration. In contradiction to this model, the proton concentration in BaPr1–xYxO3 after humidification is as much as three times greater than the dopant concentration, and even undoped samples contain a high concentration of protons. Moreover, x-ray photoemission spectra suggest that the Pr oxidation state is lowered upon hydration. In contrast, BaCe0.9Y0.1O3 shows a typical hydrogen concentration, of close to 90% of the yttrium concentration. The results are interpreted in terms of the variable valence of Pr, which can become reduced from the 4+ to the 3+ oxidation state upon exposure to water, and effectively behaves as a self-dopant within the structure

The foreclosure crisis in 2008: predatory lending or household overreaching?

At least early in the financial crisis, the high rate of foreclosures seemed to be due more to households' overreaching than to predatory lending. A disproportionate number of those being foreclosed on were well-educated, well-off and relatively young people.Foreclosure ; Mortgage loans ; Housing - Finance

Cultured Divergence of Consumption Values in Vacation Experience

The primary objective of this study is to identify and understand, from a cultural perspective, the departure of Chinese consumptive values from their U.S. counterparts on a vacation experience. Through analysis of travelogues by tourists from China and the U.S., three salient themes were identified. They are Scenery, Food and Mood. Although all three were emphasized by both Chinese and American tourists, a closer look revealed that they’re being valued quite differently. What is important to the overall satisfaction of an experience in fact differ for the two groups. These exhibited divergences are found to be underpinned by different cultural dispositions, which are pivotal in shaping and influencing distinctive values. The results allow meaningful understanding of the uniqueness of Chinese consumption values, which are buttressed by its complex cultural system

Similar dissection of sets

In 1994, Martin Gardner stated a set of questions concerning the dissection of a square or an equilateral triangle in three similar parts. Meanwhile, Gardner's questions have been generalized and some of them are already solved. In the present paper, we solve more of his questions and treat them in a much more general context. Let $D\subset \mathbb{R}^d$ be a given set and let $f_1,...,f_k$ be injective continuous mappings. Does there exist a set $X$ such that $D = X \cup f_1(X) \cup ... \cup f_k(X)$ is satisfied with a non-overlapping union? We prove that such a set $X$ exists for certain choices of $D$ and $\{f_1,...,f_k\}$. The solutions $X$ often turn out to be attractors of iterated function systems with condensation in the sense of Barnsley. Coming back to Gardner's setting, we use our theory to prove that an equilateral triangle can be dissected in three similar copies whose areas have ratio $1:1:a$ for $a \ge (3+\sqrt{5})/2$

Tumor necrosis factor-alpha (TNF-α) enhances functional thermal and chemical responses of TRP cation channels in human synoviocytes

<p>Abstract</p> <p>Background</p> <p>We have shown functional expression of several TRP channels on human synovial cells, proposing significance in known calcium dependent proliferative and secretory responses in joint inflammation. The present study further characterizes synoviocyte TRP expression and activation responses to thermal and osmotic stimuli after pre-treatment with proinflammatory mediator tumor necrosis factor alpha (TNF-α, EC50 1.3221 × 10^-10g/L).</p> <p>Results</p> <p>Fluorescent imaging of Fura-2 loaded human SW982 synoviocytes reveals immediate and delayed cytosolic calcium oscillations elicited by (1) TRPV1 agonists capsaicin and resiniferatoxin (20 – 40% of cells), (2) moderate and noxious temperature change, and (3) osmotic stress TRPV4 activation (11.5% of cells). TNF-alpha pre-treatment (1 ng/ml, 8 – 16 hr) significantly increases (doubles) capsaicin responsive cell numbers and [Ca2+]i spike frequency, as well as enhances average amplitude of temperature induced [Ca²⁺]_iresponses. With TNF-alpha pre-treatment for 8, 12, and 16 hr, activation with 36 or 45 degree bath solution induces bimodal [Ca²⁺]_iincrease (temperature controlled chamber). Initial temperature induced rapid transient spikes and subsequent slower rise reflect TRPV1 and TRPV4 channel activation, respectively. Only after prolonged TNF-alpha exposure (12 and 16 hr) is recruitment of synoviocytes observed with sensitized TRPV4 responses to hypoosmolarity (3–4 fold increase). TNF-alpha increases TRPV1 (8 hr peak) and TRPV4 (12 hr peak) immunostaining, mRNA and protein expression, with a TRPV1 shift to membrane fractions.</p> <p>Conclusion</p> <p>TNF-α provides differentially enhanced synoviocyte TRPV1 and TRPV4 expression and [Ca²⁺]_iresponse dependent on the TRP stimulus and time after exposure. Augmented relevance of TRPV1 and TRPV4 as inflammatory conditions persist would provide calcium mediated cell signaling required for pathophysiological responses of synoviocytes in inflammatory pain states.</p

Transformation Pathways of Silica under High Pressure

Concurrent molecular dynamics simulations and ab initio calculations show that densification of silica under pressure follows a ubiquitous two-stage mechanism. First, anions form a close-packed sub-lattice, governed by the strong repulsion between them. Next, cations redistribute onto the interstices. In cristobalite silica, the first stage is manifest by the formation of a metastable phase, which was observed experimentally a decade ago, but never indexed due to ambiguous diffraction patterns. Our simulations conclusively reveal its structure and its role in the densification of silica.Comment: 14 pages, 4 figure