Spectral Estimates for Degenerate Critical Levels

We establish spectral estimates at a critical energy level for h-pseudo-differential operators. Via a trace formula, we compute the contribution of isolated (nonextremum) critical points under a condition of "real principal type." The main result holds for all dimensions, for a singularity of any finite order and can be invariantly expressed in terms of the geometry of the singularity. When the singularities are not integrable on the energy surface the results are significative since the order w.r.t. h of the spectral distributions are bigger than in the regular setting.     

Spectral Fluctuations of Schrödinger Operators Generated by Critical Points of the Potential

Starting from the spectrum of Schrödinger operators on ${\mathbb R}^nStarting from the spectrum of Schr?dinger operators on , we propose a method to detect critical points of the potential. We argue semi-classically on the basis of a mathematically rigorous version of Gutzwiller's trace formula which expresses spectral statistics in term of classical orbits. A critical point of the potential with zero momentum is an equilibrium of the flow and generates certain singularities in the spectrum. Via sharp spectral estimates, this fluctuation indicates the presence of a critical point and allows to reconstruct partially the local shape of the potential. Some generalizations of this approach are also proposed.     

Application of the J-walking formalism to the test particle method: adsorption isotherms for atomic monolayers

By implementing the J-walking formalism within the test particle method, adsorption isotherms for various Lennard-Jones systems were constructed. The method decreases the uncertainties in the average thermodynamic values by approximately one order of magnitude and substantially increases the percentage insertion of the ghost particle. The adsorption isotherms showed that at low temperatures the amount of adsorbed material seems to be independent of the vapour pressure of the gas if attractive forces dominate the system. On the other hand, systems dominated by repulsive forces show the usual type B behaviour for adsorption isotherms. The equation of state is used to confirm these results.     

Quantitative colorimetric analysis of aloe polysaccharides as a measure of Aloe vera quality in commercial products

Aloe vera inner leaf gel has been used as a medicinal remedy for many years. Yet some aloe products do not demonstrate beneficial effects, indicating that poor quality products are reaching the market. Therefore, an efficient and accurate method is needed to evaluate the quality of aloe products. This paper describes a quick, quantitative colorimetric assay that has been developed for the determination of glucomannan in aloe gel and products. With this method, interference by non-aloe polysaccharides or other extraneous components was absent or negligible. Data indicate that the glucomannan can be determined at parts per million (mg/L) in aqueous solutions with an accuracy of 100 +/- 5% at a 10 mg/L concentration. The correlation coefficient is 0.999, and linearity is from 0.9 to 72.7 mg/L in the test solution. The method is inexpensive, simple, sensitive, and reproducible. This method was applied to determine the polysaccharide content of commercial aloe products. Both qualitative and quantitative information can be obtained in about 5 min.     

Analysis of spectinomycin by liquid chromatography with pulsed electrochemical detection

Until now, no LC method is described to determine the purity and content of spectinomycin without prior derivatization. A reversed-phase ion-pair LC method using a base deactivated column and pulsed electrochemical detection is described. The mobile phase consisted of an aqueous solution containing 5.8 g/l pentafluoropropionic acid, 1.25 g/l potassium dihydrogen phosphate and 5.5 ml/l tetrahydrofuran. The pH was adjusted to 6.25 using dilute NaOH solution. An experimental design was used to optimize the chromatographic parameters and to check the robustness. The quality of separation was investigated on different stationary phases. The method allows the separation of spectinomycin from its related substances as well as some other components of unknown identity. The total time of analysis is 65 min. A number of commercial samples were examined using this method.     

Hepcidin in iron metabolism

Hepcidin, which has been recently identified both by biochemical and genomic approaches, is a 25 amino acid polypeptide synthesized mainly by hepatocytes and secreted into the plasma. Besides its potential activity in antimicrobial defense, hepcidin plays a major role in iron metabolism. It controls two key steps of iron bioavailability, likely through a hormonal action: digestive iron absorption by enterocytes and iron recycling by macrophages. In humans, this could explain that low levels of hepcidin found during juvenile haemochromatosis and HFE-1 genetic haemochromatosis are associated with an iron overload phenotype. Conversely, an increase of hepcidin expression is suspected to play a major role in the development of anemia of chronic inflammatory diseases. However, the regulatory mechanisms of hepcidin expression are multiple, including iron-related parameters, anemia, hypoxia, inflammation and hepatocyte function. Therefore, many physiological and pathological situations may modulate hepcidin expression and subsequently iron metabolism. A better knowledge of the biological effects of hepcidin and of its expression regulatory mechanisms will clarify the place of hepcidin in the diagnosis and treatment of iron-related diseases.     

Crystal chemistry and thermal behavior of metal salts and complexes of unsaturated dicarboxylic acids: aquabis(hydrogen itaconato)barium(II), [Ba(C5H5O4)2(OH2)]

[Ba(C₅H₅O₄)₂(OH₂)] is monoclinic, C2/c, with a = 4.472(1), b = 13.312(3), c = 22.236(5) Å, = 92.90(1)°, Z = 4, and D _m = 2.06 g cm^–3. The barium atom is 10-coordinate with Ba—O distances in the range 2.749(2)–2.989(2) Å. The material suffers a complex decomposition process upon heating at temperatures between 25 and 600°C in dynamic nitrogen and static air atmospheres. FT-IR and gas chromatography analyses indicate that water, CO, CO₂, methane, ethane, ethylene, propane, propylene, and butane, are evolved during the heating process, leaving a residue of BaCO₃. ¹H-NMR spectra of a sample heated at 200°C, showed isomerization of barium itaconate to barium methylmaleate.     

New flux systems for the LPE growth of thin garnet films

A new flux system is presented for the growth of bismuth substituted iron garnet thin films by liquid phase epitaxy. The fluxes do not contain lead and are based on the system Bi₂O₃, RO₂ where R = Si, Ge, Ti or Ce. Data is presented that shows the viscosities of these melts are below 16 cp at temperatures ∽800°C when the eutectic compositions are chosen and that they have low freezing points. The growth conditions and melt compositions are given for the growth of various rare-earth iron garnets with high bismuth substitutions. Results of measurements of optical and magnetic properties of some of the from Pb containing fluxes. Thus these materials are more promising for use in magnetic bubble displays. It is also shown that the uniaxial anisotropy was also less in the films grown from the new system than those grown from Pb containing fluxes.     

Active control of strong plasmon–exciton coupling in biomimetic pigment–polymer antenna complexes grown by surface-initiated polymerisation from gold nanostructures

Plexcitonic antenna complexes, inspired by photosynthetic light-harvesting complexes, are formed by attachment of chlorophylls (Chl) to poly(cysteine methacrylate) (PCysMA) scaffolds grown by atom-transfer radical polymerisation from gold nanostructure arrays. In these pigment–polymer antenna complexes, localised surface plasmon resonances on gold nanostructures are strongly coupled to Chl excitons, yielding hybrid light–matter states (plexcitons) that are manifested in splitting of the plasmon band. Modelling of the extinction spectra of these systems using a simple coupled oscillator model indicates that their coupling energies are up to twice as large as those measured for LHCs from plants and bacteria. Coupling energies are correlated with the exciton density in the grafted polymer layer, consistent with the collective nature of strong plasmon–exciton coupling. Steric hindrance in fully-dense PCysMA brushes limits binding of bulky chlorophylls, but the chlorophyll concentration can be increased to ∼2 M, exceeding that in biological light-harvesting complexes, by controlling the grafting density and polymerisation time. Moreover, synthetic plexcitonic antenna complexes display pH- and temperature-responsiveness, facilitating active control of plasmon–exciton coupling. Because of the wide range of compatible polymer chemistries and the mild reaction conditions, plexcitonic antenna complexes may offer a versatile route to programmable molecular photonic materials.

Excitons in pigment–polymer antenna complexes formed by attachment of chlorophyll to surface grafted polymers are coupled strongly to plasmon modes, with coupling energies twice those for biological light-harvesting complexes and active control of plasmon–exciton coupling.     

Using Microfluidic Set-Up to Determine the Adsorption Rate of Sporosarcina pasteurii Bacteria on Sandstone

Transport in Porous Media - Microbial-induced carbonate precipitation (MICP) in porous media is a two-step procedure: First, the suspension of bacteria is injected and some of the bacteria get...