Bifurcation Boundary Conditions for Switching DC-DC Converters Under Constant On-Time Control

Sampled-data analysis and harmonic balance analysis are applied to analyze switching DC-DC converters under constant on-time control. Design-oriented boundary conditions for the period-doubling bifurcation and the saddle-node bifurcation are derived. The required ramp slope to avoid the bifurcations and the assigned pole locations associated with the ramp are also derived. The derived boundary conditions are more general and accurate than those recently obtained. Those recently obtained boundary conditions become special cases under the general modeling approach presented in this paper. Different analyses give different perspectives on the system dynamics and complement each other. Under the sampled-data analysis, the boundary conditions are expressed in terms of signal slopes and the ramp slope. Under the harmonic balance analysis, the boundary conditions are expressed in terms of signal harmonics. The derived boundary conditions are useful for a designer to design a converter to avoid the occurrence of the period-doubling bifurcation and the saddle-node bifurcation.Comment: Submitted to International Journal of Circuit Theory and Applications on August 10, 2011; Manuscript ID: CTA-11-016

Pharmacokinetic/Pharmacodynamic Profiles of Tiamulin in an Experimental Intratracheal Infection Model of Mycoplasma gallisepticum

Mycoplasma gallisepticum is the most important pathogen in poultry among four pathogenic Mycoplasma species. Tiamulin is a pleuromutilin antibiotic that shows a great activity against M. gallisepticum and has been approved for use in veterinary medicine particularly for poultry. However, the pharmacokinetic/pharmacodynamics (PK/PD) profiles of tiamulin against M. gallisepticum are not well understood. Therefore, in the current studies, we investigated the in vivo PK/PD profiles of tiamulin using a well-established experimental intratracheal infection model of M. gallisepticum. The efficacy of tiamulin against M. gallisepticum was studied in 8-day-old chickens after intramuscular (i.m.) administration at 10 doses between 0-80 mg/kg. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to evaluate the PK parameters of tiamulin following i.m. administration at doses of 5, 40, and 80 mg/kg in Mycoplasma gallisepticum-infected neutropenic chickens. Real-time PCR (RT-PCR) was used for quantitative detection of M. gallisepticum. The MIC of tiamulin against M. gallisepticum strain S6 was 0.03 μg/mL. The PK/PD index, AUC24h/MIC, correlated well with the in vivo antibacterial efficacy. The in vivo data suggest that animal dosage regimens should supply AUC24h/MIC of tiamulin of 382.68 h for 2 log10 ccu equivalents M. gallisepticum reduction. To attain that goal, the administered dose is expected to be 45 mg/kg b.w. for treatment of M. gallisepticum infection with an MIC90 of 0.03 μg/mL

catena-Poly[[[aqua­(1,10-phenanthro­line)zinc(II)]-μ-3,3′-(p-phenyl­ene)di­acrylato] hemihydrate]

In the title compound, {[Zn(C12H8O4)(C12H8N2)(H2O)]·0.5H2O}n, each ZnII atom is six-coordinated by two N atoms from one 1,10-phenanthroline (phen), three carboxyl­ate O atoms from two different L ligands [H2 L = 3,3′-(p-phenyl­ene)diacrylic acid] and one water mol­ecule in a distorted octa­hedral environment. The two L dianions are situated across inversion centres and bridge neighbouring ZnII centres, yielding a chain propagating parallel to [100]. O—H⋯O hydrogen bonds between the coordinated water molecule, the solvent water molecule (half-occupied) and the carboxylate O atoms further stabilize the structure

Orange fluorescent proteins constructed from cyanobacteriochromes chromophorylated with phycoerythrobilin

Cyanobacteriochromes are a structurally and spectrally highly diverse class of phytochrome-related photosensory biliproteins. They contain one or more GAF domains that bind phycocyanobilin (PCB) auto-catalytically; some of these proteins are also capable of further modifying PCB to phycoviolobilin or rubins. We tested the chromophorylation with the non-photochromic phycoerythrobilin (PEB) of 16 cyanobacteriochrome GAFs from Nostoc sp. PCC 7120, of Slr1393 from Synechocystis sp. PCC 6803, and of Tlr0911 from Thermosynechococcus elongatus BP-1. Nine GAFs could be autocatalytically chromophorylated in vivo/in E. coli with PEB, resulting in highly fluorescent biliproteins with brightness comparable to that of fluorescent proteins like GFP. In several GAFs, PEB was concomitantly converted to phycourobilin (PUB) during binding. This not only shifted the spectra, but also increased the Stokes shift. The chromophorylated GAFs could be oligomerized further by attaching a GCN4 leucine zipper domain, thereby enhancing the absorbance and fluorescence of the complexes. The presence of both PEB and PUB makes these oligomeric GAF-''bundles'' interesting models for energy transfer akin to the antenna complexes found in cyanobacterial phycobilisomes. The thermal and photochemical stability and their strong brightness make these constructs promising orange fluorescent biomarkers

Effect and mechanism of exogenous selenium on selenium content and quality of fresh tea leaves

To study the effect and mechanism of selenium sources on the selenium content and quality of fresh tea leaves, tea seedlings (Camellia sinensis (L.) O. Kuntze) were the research object. A solution of 100 mg/L sodium selenate (Na2SeO4), sodium selenite (Na2SeO3), and selenium yeast (selenium yeast) were applied on the leaves surface of 5-week-old tea plants, and the selenium levels in the leaves, roots, and stems were determined at 20 weeks of age. The effects of different selenium sources on the mineral nutrient content, antioxidant enzyme activity, and quality parameters content in leaves were analyzed. The mechanism was analyzed by detecting the expression levels of related genes. The results showed that the three selenium sources can increase the growth of tea seedlings and the selenium content in leaves and stems, and the selenium yeast treatment had the most significant effect. Selenium spraying promoted the absorption of mineral nutrients such as nitrogen, phosphorus, and potassium, but had no significant impact on the absorption of calcium and magnesium. Spraying the three selenium sources dramatically increased the activities of APX, POD, and SOD antioxidant enzymes, among which the selenium yeast treatment had the most significant effect. However, there was no significant impact on the MDA level in this study. Selenium sources markedly increased leaves total amino acid levels, accompanied by up-regulation the genes of amino acid synthetic enzymes (CsGS, CsGOGAT, and CsGDH). Leaves glucose, tea polyphenol, total soluble protein, catechin, flavonoid contents, and sucrose were higher in selenium sources treatments than in control treatment seedlings. Moreover, selenium sources up-regulated expression of CsHMGR, CsAPX, and CsTCS1 genes. selenium yeast had the best comprehensive effect of the three selenium sources. These results confirmed that selenium sources play a positive role on the selenium content and quality of tea by increasing the antioxidant capacity of leaves, the absorption rate of mineral nutrients, and regulating expression of related genes in Camellia sinensis

Combination therapy strategies against multiple-resistant streptococcus suis

<p>Streptococcus suis is a major swine pathogen, an emerging zoonotic agent responsible for meningitis, endocarditis and septicaemia followed by deafness in humans. The development of antimicrobial resistance in S. suis increases the risk for therapeutic failure in both animals and humans. In this study, we report the synergism of combination therapy against multi-resistant S. suis isolates from swine. Twelve antibiotic profiles were determined against 11 S. suis strains. To investigate their synergistic/antagonistic activity, checkerboard assay was performed for all the possible combinations. In-vitro killing curves and in-vivo treatment trials were used to confirm the synergistic activity of special combinations against S. suis dominant clones. In this study, 11 S. suis isolates were highly resistant to erythromycin, clindamycin, trimethoprim/sulfamethoxazole, and tetracycline with ratios of 80–100%, and the resistance percentages to enrofloxacin, florfenicol, and spectinomycin were ~50%. The checkerboard data identified two combination regimens, ampicillin plus apramycin and tiamulin plus spectinomycin which gave the greatest level of synergism against the S. suis strains. In-vitro kill-curves showed a bacterial reduction of over 3-logCFU with the use of combination treatments, whilst the application of mono-therapies achieve less than a 2-logCFU cell killing. In-vivo models confirm that administration of these two combinations significantly reduced the number of bacterial cells after 24 h of treatment. In conclusions, the combinations of ampicillin plus apramycin and tiamulin plus spectinomycin showed the greatest synergism and may be potential strategies for treatment of multi-resistant S. suis in animal.</p

Effects of whole cigarette smoke on human beta defensins expression and secretion by oral mucosal epithelial cells

Background Cigarette smoke a recognized risk factor for many systemic diseases and also oral diseases. Human beta defensins (HBDs), a group of important antimicrobial peptides expressed by the epithelium, are crucial for local defense and tissue homeostasis of oral cavity. The aim of this study was to evaluate potential effects of whole cigarette smoke (WCS) exposure on the expression and secretion of HBDs by oral mucosal epithelial cells. Methods Immortalized human oral mucosal epithelial (Leuk-1) cells were exposed to WCS for various time periods. HBD-1, -2 and -3 expression and subcellular localization were detected by real time qPCR, immunofluorescence assay and confocal microscopy. According to the relative fluorescent intensity, the expression levels of HBD-1, -2 and -3 were evaluated by digital image analysis system. The alteration of HBD-1, -2 and -3 secretion levels was measured by the Enzyme-Linked Immunosorbent Assay. Results WCS exposure remarkably attenuated HBD-1 expression and secretion while clearly enhanced HBD-2, -3 expression levels and HBD-2 secretion by Leuk-l cells. It appeared that there was no significant effect of WCS exposure on HBD-3 secretion. Conclusions WCS exposure could modulate expression and secretion of HBDs by oral mucosal epithelial cells, establishing a link between cigarette smoke and abnormal levels of antimicrobial peptides. The present results may give a new perspective to investigate smoking-related local defense suppression and oral disease occurrence