In situ observation of synthesized nanoparticles in ultra-dilute aerosols via X-ray scattering

In-air epitaxy of nanostructures (Aerotaxy) has recently emerged as a viable route for fast, large-scale production. In this study, we use small-angle X-ray scattering to perform direct in-flight characterizations of the first step of this process, i.e., the engineered formation of Au and Pt aerosol nanoparticles by spark generation in a flow of N₂ gas. This represents a particular challenge for characterization because the particle density can be extremely low in controlled production. The particles produced are examined during production at operational pressures close to atmospheric conditions and exhibit a lognormal size distribution ranging from 5–100 nm. The Au and Pt particle production and detection are compared. We observe and characterize the nanoparticles at different stages of synthesis and extract the corresponding dominant physical properties, including the average particle diameter and sphericity, as influenced by particle sintering and the presence of aggregates. We observe highly sorted and sintered spherical Au nanoparticles at ultra-dilute concentrations (< 5 × 10⁵ particles/cm³) corresponding to a volume fraction below 3 × 10^–10, which is orders of magnitude below that of previously measured aerosols. We independently confirm an average particle radius of 25 nm via Guinier and Kratky plot analysis. Our study indicates that with high-intensity synchrotron beams and careful consideration of background removal, size and shape information can be obtained for extremely low particle concentrations with industrially relevant narrow size distributions.

     

Applications and limitations of the colloid titration method for measuring activated sludge surface charges

Surface charge quantification of polymer solutions and sludge suspensions were investigated by the colloid titration technique and compared to charge densities obtained by pH-titration. The colloid titration technique worked well for polymer samples. The charge quantity of humic acid and activated sludge extracellular polymers (EPS) was estimated to be -1.51 and -0.42 meq/g, respectively. These values are reasonable when compared to pH-titration results. The surface charge of activated sludge particles appears to be below the limit of detection. However, surface charge estimates are obtained, when the reactant doses and sample concentration are increased. It is suggested that such estimates are not correct, but artefacts of the non-stoichiometric precipitation of the polymeric reactants at high doses. It appears that the colloid titration method is limited to conditions of low reactant doses and valid for charge determination of extracted sludge polymers, whereas the method is not valid for charge determination of whole sludge.     

Quantifying inequality in health in the absence of a natural reference group

When quantifying inequality in health, the excess fraction (i.e. the proportional reduction in the outcome in question that would occur if all groups had the same, lowest, risk rate) is an appealing measure. If the population contains a natural, healthiest reference group, the excess fraction is straightforward to estimate. In the absence of an a priori reference group, calculating the excess fraction requires reflection, since using the group with the lowest observed risk rate as reference can lead to erroneous conclusions. This paper proposes a simple simulation procedure for calculating the excess fraction, without fixing a reference group.     

Riboflavin-mediated delivery of a macromolecule into cultured human cells

The effects of perivascular nerve stimulation and phenylephrine on osmolyte release were studied in the intact perfused rat liver and isolated liver parenchymal cells (PC) and nonparenchymal cells. In the perfused liver, electrical stimulation of perivascular nerves (20 Hz/2 ms/20 V) led to a phentolamine-sensitive increase of cell hydration by 6.5% +/- 1.2% (n = 3) and a transient phentolamine-sensitive stimulation of taurine and inositol, but not betaine, release. These nerve effects were mimicked by phenylephrine, but not prostaglandin F2alpha, and were not affected by sodium nitroprusside (SNP) or ibuprofen. Nerve stimulation-induced taurine, but not inositol, release was inhibited by 4, 4'-di-isothiocyanatostilbene-2,2'-disulphonic acid (DIDS) (50 micromol/L). Single-cell fluorescence studies with isolated liver PC, Kupffer cells (KC), sinusoidal endothelial cells (SEC), and hepatic stellate cells (HSC) revealed that phenylephrine induced an increase in cytosolic free Ca2+ only in PC and HSC, but not in KC and SEC, whereas extracellular uridine triphosphate (UTP) produced Ca2+ transients/oscillations in all liver cell types studied. Phenylephrine had no effect on osmolyte release from isolated KC and SEC, but increased taurine (but not inositol) release from PC and inositol (but not taurine) efflux from HSC. The data suggest that: 1) liver cell hydration and-consecutively-osmolyte content are modulated by hepatic nerves via an alpha-adrenergic mechanism, which does not involve eicosanoids or hemodynamic changes; 2) that PC and HSC are the primary targets for nerve-dependent alpha-adrenergic activation, whereas 3) KC and SEC probably do not express alpha-adrenoceptors coupled to Ca2+ mobilization or osmolyte efflux.     

Evaluation of biochemical changes during in vivo erythrocyte senescence in the dog

One hypothesis to explain the age-dependent clearance of red blood cells (RBCs) from circulation proposes that denatured/oxidized hemoglobin (hemichromes) arising late during an RBC's life span induces clustering of the integral membrane protein, band 3. In turn, band 3 clustering generates an epitope on the senescent cell surface leading to autologous IgG binding and consequent phagocytosis. Because dog RBCs have survival characteristics that closely resemble those of human RBCs (ie, low random RBC loss, approximately 115-day life span), we decided to test several aspects of the above hypothesis in the canine model, where in vivo aged cells of defined age could be evaluated for biochemical changes. For this purpose, dog RBCs were biotinylated in vivo and retrieved for biochemical analysis at various later dates using avidin-coated magnetic beads. Consistent with the above hypothesis, senescent dog RBCs were found to contain measurably elevated membrane-bound (denatured) globin and a sevenfold enhancement of surface-associated autologous IgG. Interestingly, dog RBCs that were allowed to senesce for 115 days in vivo also suffered from compromised intracellular reducing power, containing only 30% of the reduced glutathione found in unfractionated cells. Although the small quantity of cells of age >/=110 days did not allow direct quantitation of band 3 clustering, it was nevertheless possible to exploit single-cell microdeformation methods to evaluate the fraction of band 3 molecules that had lost their normal skeletal linkages and were free to cluster in response to hemichrome binding. Importantly, band 3 in RBCs >/=112 days old was found to be 25% less restrained by skeletal interactions than band 3 in control cells, indicating that the normal linkages between band 3 and the membrane skeleton had been substantially disrupted. Interestingly, the protein 4.1a/protein 4.1b ratio, commonly assumed to reflect RBC age, was found to be maximal in RBCs isolated only 58 days after labeling, implying that while this marker is useful for identifying very young populations of RBCs, it is not a very sensitive marker for canine senescent RBCs. Taken together, these data argue that several of the readily testable elements of the above hypothesis implicating band 3 in human RBC senescence can be validated in an appropriate canine model.     

The Gyricon rotating ball display

Abstract— The Gyricon display consists of hemispherical black and white (bichromal) balls contained in individual liquid-filled cavities and disposed to orient in an electrical field. This bistable reflective light display currently has a diffuse reflectance of more than 18% and a contrast ratio of more than 6:1. The viewing angle approaches that of paper. A new method of fabricating the bichromal balls has enabled practical realization of large-area high-quality displays.     

PEDB: the Prostate Expression Database

Naloxone is generally considered to be a pure antagonist, but it may produce several behavioral effects, such as hyperalgesia or stimulation of respiration. We studied the effect of naloxone on gastric emptying and gastrointestinal transit in rats. Six to eight Wistar rats (200-250 g) were used for each experiment. Either saline or naloxone (0.01-10 mg/kg) was injected intraperitoneally at 0 min. At 30 min, radiolabeled saline or milk 1 mL was infused into the stomach. At 60 min, gastric emptying and gastrointestinal transit were calculated by measuring the radioactivity in the gastrointestinal tract. Naloxone significantly inhibited gastric emptying of saline (P = 0.002) and of milk (P < 0.05), but not the gastrointestinal transit of either (P > 0.05). Gastric emptying of saline showed a significant peak (P < 0.05) in the dose-response curve at 0.7 mg/kg. Therefore, naloxone significantly inhibits gastric emptying of saline and milk, but not the gastrointestinal transit of either. IMPLICATIONS: Although naloxone is generally considered to be a pure opioid receptor antagonist, it delays gastric emptying of saline or milk, as does morphine in the rat. However, it is uncertain from our results whether naloxone inhibited gastric emptying by antagonizing the effects of endogenous opioids.     

Differential reactivity of the rat S100A4(p9Ka) gene to sodium bisulfite is associated with differential levels of the S100A4 (p9Ka) mRNA in rat mammary epithelial cells

Elevated intracellular levels of S100A4, an S100-related calcium-binding protein, induce metastatic capability in benign mammary tumor-derived epithelial cells and in transgenic mice bearing oncogene-induced benign mammary tumors. The S100A4(p9Ka) gene in rat mammary epithelial cells expressing low levels of S100A4 yields a reduced number of fragments upon digestion with the methylation-sensitive restriction enzyme, HpaII, compared with the gene from high S100A4-expressing cells. Genomic sequencing of two potential regulatory elements in the S100A4 gene, an intronic enhancer and TATA box region, revealed that in low S100A4-expressing cells, most cytosine bases exhibited high levels of resistance to conversion to thymine by sodium bisulfite. In derivative cell lines, which express high levels of S100A4, only a small number of cytosine bases were resistant to treatment with sodium bisulfite. In contrast, cytosine bases in the DNA surrounding an upstream regulatory region, which binds inhibitory GC factor in the low-expressing cell lines, are sensitive to conversion to thymine by sodium bisulfite in both low- and high-expressing cell lines. The results suggest that the rat S100A4 gene is maintained in a different state in the low-expressing cell lines and that this state might be a consequence of the pattern of methylation in this regulated gene that does not contain a CpG island.     

Binding of polyphenols to plant cell wall analogues – Part 2: Phenolic acids

Bacterial cellulose and cellulose–pectin composites were used as well-defined model plant cell wall (PCW) systems to study the interaction between phenolic acids (PA) derived from purple carrot juice concentrate (PCJC) and PCW components. Significant PA depletion from solution occurred, with pure cellulose initially (30 s–1 h) absorbing more than cellulose–pectin composites in the first hour (ca 20% cf 10–15%), but with all composites absorbing similar levels (ca 30%) after several days. Individual PAs bound to different relative extents with caffeic acid > chlorogenic acid > ferulic acid. Extrapolation of data for these model systems to carrot puree suggests that nutritionally-significant amounts of PAs could bind to cell walls, potentially restricting bioavailability in the small intestine and, as a consequence, delivering PAs to the large intestine for fermentation and metabolism by gut bacteria.