Frequency-stabilization to 6x10^-16 via spectral-hole burning

We demonstrate two-stage laser stabilization based on a combination of Fabry- Perot and spectral-hole burning techniques. The laser is first pre-stabilized by the Fabry-Perot cavity to a fractional-frequency stability of sigma_y(tau) < 10^-13. A pattern of spectral holes written in the absorption spectrum of Eu3+:Y2SiO5 serves to further stabilize the laser to sigma_y(tau) = 6x10^-16 for 2 s < tau < 8 s. Measurements characterizing the frequency sensitivity of Eu3+:Y2SiO5 spectral holes to environmental perturbations suggest that they can be more frequency stable than Fabry-Perot cavities

Continuous flow homogeneous catalysis: hydroformylation of alkenes in supercritical fluid-ionic liquid biphasic mixtures

Rhodium complexes of [1-propyl-3-methylimidazolium](2) [PhP(C6H4SO3-3)(2)] dissolved in the ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate catalyse the hydroformylation of oct-1-ene at a constant rate for &gt; 20 h in a continuous flow process in which the substrate, gases and products are transported in and out of the reactor dissolved in scCO(2); &lt;1 ppm rhodium is present in the collected product.</p

Ratio Spectra Derivative and Zero-Crossing Difference Spectrophotometric Determination of Olmesartan Medoxomil and Hydrochlorothiazide in Combined Pharmaceutical Dosage Form

Two simple, economical, rapid, precise, and accurate methods for simultaneous determination of olmesartan medoxomil and hydrochlorothiazide in combined tablet dosage form have been developed. The first method is based on ratio spectra derivative spectrophotometry, and the second method is zero-crossing difference spectrophotometry. The amplitudes in the first derivative of the corresponding ratio spectra at 231.0 and 271.0 nm were selected to determine olmesartan medoxomil and hydrochlorothiazide, respectively. Measurements of absorbance were carried out at zero-crossing wavelengths 257.8 and 240.2 nm for olmesartan medoxomil and hydrochlorothiazide by zero-crossing difference spectrophotometric method. Beer’s law is obeyed in the concentration range of 08–24 µg/mL for olmesartan medoxomil (OLM) and 05–15 µg/mL for hydrochlorothiazide (HCT) by ratio spectra derivative and 05–30 µg/mL for OLM and HCT by zero-crossing difference spectrophotometric method. The results of the assay were found to be 100.46 ± 0.95 for OLM and 100.4 ± 0.27 for HCT by ratio spectra derivative and 99.06 ± 1.14 for OLM and 100.05 ± 0.90 for HCT by zero-crossing difference spectrophotometric method. These methods passes F test and t test. Both methods were validated statistically and by performing recovery study

Organic potassium salts or fibers effects on mineral balance and digestive fermentations in rats adapted to an acidogenic diet

Background Fibers and potassium (K) organic salts in plant foods are liable to affect Ca and Mg balance at digestive and renal levels, respectively. K organic salts could counteract the acidifying effects of western diets and consequences of excess NaCl. Aim of the study To study this question, male rats were adapted to a basal acidifying low-K (LK) diet, or to diets supplemented with a fiber mix (LK/F), or K citrate (HK) or both (HK/F). Results HK and HK/F diets displayed a marked alkalinizing effect in urine and promoted citraturia, but this effect was not modulated by fibers. The effect of fibers on Ca digestive absorption was more potent than K citrate effect on Ca renal excretion. In contrast, K citrate effect on kidney Mg excretion was more effective than that of fibers on Mg digestive absorption, a maximal effect on Mg balance was observed in rats fed the HK/F diet. Digestive fermentations in rats fed the LK/F diet were characterized by high-propionic acid fermentations and succinate accumulation. In rats adapted to the HK/F diet, K citrate supplementation depressed succinate and increased butyrate concentrations. Conclusion Organic anions arising from digestive fermentations seem to be not directly involved in the alkalinizing effects of plant foods. Fibers and organic K salts exert distinct effects on Ca and Mg metabolism, but with interesting interactions as to Mg balance, digestive fermentations and urine pH

High-avidity IgA protects the intestine by enchaining growing bacteria

Vaccine-induced high-avidity IgA can protect against bacterial enteropathogens by directly neutralizing virulence factors or by poorly defined mechanisms that physically impede bacterial interactions with the gut tissues ('immune exclusion'). IgA-mediated cross-linking clumps bacteria in the gut lumen and is critical for protection against infection by non-typhoidal Salmonella enterica subspecies enterica serovar Typhimurium (S. Typhimurium). However, classical agglutination, which was thought to drive this process, is efficient only at high pathogen densities (≥10; 8; non-motile bacteria per gram). In typical infections, much lower densities (10; 0; -10; 7; colony-forming units per gram) of rapidly dividing bacteria are present in the gut lumen. Here we show that a different physical process drives formation of clumps in vivo: IgA-mediated cross-linking enchains daughter cells, preventing their separation after division, and clumping is therefore dependent on growth. Enchained growth is effective at all realistic pathogen densities, and accelerates pathogen clearance from the gut lumen. Furthermore, IgA enchains plasmid-donor and -recipient clones into separate clumps, impeding conjugative plasmid transfer in vivo. Enchained growth is therefore a mechanism by which IgA can disarm and clear potentially invasive species from the intestinal lumen without requiring high pathogen densities, inflammation or bacterial killing. Furthermore, our results reveal an untapped potential for oral vaccines in combating the spread of antimicrobial resistance