Infrared laser ablation atmospheric pressure photoionization mass spectrometry

In this paper we introduce laser ablation atmospheric pressure photoionization (LAAPPI), a novel atmospheric pressure ion source for mass spectrometry. In LAAPPI the analytes are ablated from water-rich solid samples or from aqueous solutions with an infrared (IR) laser running at 2.94 μm wavelength. Approximately 12 mm above the sample surface, the ablation plume is intercepted with an orthogonal hot solvent (e.g., toluene or anisole) jet, which is generated by a heated nebulizer microchip and directed toward the mass spectrometer inlet. The ablated analytes are desolvated and ionized in the gas-phase by atmospheric pressure photoionization using a 10 eV vacuum ultraviolet krypton discharge lamp. The effect of operational parameters and spray solvent on the performance of LAAPPI is studied. LAAPPI offers ~300 μm lateral resolution comparable to, e.g., matrix-assisted laser desorption ionization. In addition to polar compounds, LAAPPI efficiently ionizes neutral and nonpolar compounds. The bioanalytical application of the method is demonstrated by the direct LAAPPI analysis of rat brain tissue sections and sour orange (Citrus aurantium) leaves.     

Polymeric dual-slab waveguide interferometer for biochemical sensing applications

A polymer based dual-slab waveguide Young's interferometer was demonstrated for biochemical sensing. Evanescent field is utilized for probing the binding events of biomolecules on the waveguide surface. Refractive index sensing in analyte and protein adsorption on the sensing surface were investigated with glucose de-ionized water solution and bovine serum albumin, immunoglobulin G solutions in phosphate buffered saline buffer. A detection limit of 10(-5) RIU and 4 pg/mm(2) was achieved for homogeneous and surface sensing, respectively. Also, the influence of water absorption inside the polymeric device on the measurement stability was evaluated. The results indicate that the waveguide polymer sensor fabricated with the spin coating technique can achieve a satisfactory sensitivity for homogeneous refractive index sensing and, as well, for monitoring molecular binding events on the surface.     

Comparison of calcium phosphate product values using measurement of plasma total calcium and serum ionized calcium

Calcium phosphate product (Ca x Pi) is a clinically relevant tool to estimate the cardiovascular risk of patients with renal failure. In reports, mostly total serum calcium has been used. As measurement of serum ionized calcium has some benefits and is being used increasingly, we estimated the respective levels of calcium phosphate product using both total (t-Ca x Pi) and ionized calcium (ion-Ca x Pi). Fifty-eight healthy individuals and 180 hemodialysis (HD) patients from 2 centers were studied. Diagnostic accuracies for corresponding values of the t-Ca x Pi and ion-Ca x Pi were calculated using a GraphROC program. Of HD patients, 64% had t-Ca x Pi <4.4 mmol(2)/L(2) regarded as a desirable goal, and 10% had values over 5.6 mmol(2)/L(2) associated with a high cardiovascular risk. Based on GraphROC analysis, t-Ca x Pi of 4.4 mmol(2)/L(2) corresponded to a value of 2.2 mmol(2)/L(2) of ion-Ca x Pi and, respectively, t-Ca x Pi of 5.6 mmol(2)/L(2) corresponded 2.8 mmol(2)/L(2) of ion-Ca x Pi. Owing to the good agreement between the results in the 2 centers, these values for risk levels can be used in both centers. When measurement of ionized calcium is used, Ca x Pi values of 2.2 and 2.8 mmol(2)/L(2) can be used instead of generally used values of 4.4 and 5.6 mmol(2)/L(2) with total calcium.     

Fabrication of optical inverted-rib waveguides using UV-imprinting

In this paper we introduce a fabrication process for polymer rib waveguides that uses UV-imprint lithography. In the structure of an inverted-rib waveguide, the lower cladding of the waveguide is patterned by UV-imprinting and the waveguiding layer is subsequently spin-coated. That makes the thickness of the formed slab layer on the rib waveguide controllable by tuning the spin-coating parameters. The fabrication process utilizes two steps of UV-imprinting. The first one is to form a rigid polymer mold from positive tone photoresist. The second one is to pattern the waveguide lower cladding with the formed polymer mold. Through the two steps of UV-imprinting, rib waveguides can be fabricated without an etching procedure. We demonstrated the proposed fabrication process by fabricating 2-μm-wide waveguides operating in single mode at 1310 nm. With TE-polarized light, the fabricated waveguides show an average transmission of 58.6% in a 30 mm long waveguide, corresponding to a loss of 2.3 dB.     

Electrospray Encapsulation of Hydrophilic and Hydrophobic Drugs in Poly(L‐lactic acid) Nanoparticles

An electrospray method is developed for preparation of beclomethasone‐dipropionate‐ and salbutamol‐sulfate‐loaded biodegradable poly(L ‐lactic acid) nanoparticles. Different set‐up parameters for electrospraying are examined on particle size, and preparation conditions are optimized for producing spherical‐drug‐loaded nanoscale particles by controllable processing parameters. Polylactide (PLA)–drug nanoparticles with average diameters of around 200 nm are achieved in a stable cone‐jet mode with a flow rate of 4 µL min^?1, polymer concentration of 1%, and ammonium hydroxide content of 0.05%. Morphology and size of the drug–polymer nanoparticles are analyzed by scanning electron microscopy and transmission electron microscopy. Changes in the crystallinity of the PLA polymer and the model drugs are detected by X‐ray powder diffraction, and the absence of molecular interactions are confirmed by thermal analyses. The results indicate clearly that electrospraying is a potential method for producing polymeric nanoparticles and for encapsulating both hydrophilic and hydrophobic drugs efficiently into the nanoparticles.     

Simple coupling of gas chromatography to electrospray ionization mass spectrometry

A simple method for direct coupling of gas chromatography (GC) with electrospray ionization mass spectrometry (ESI/MS) has been developed. The outlet of the GC capillary column was placed between the ESI needle and the atmospheric pressure ionization (API) source of a mass spectrometer. The ionization occurs via dissolution of neutral compounds into the charged ESI droplet followed by ion evaporation or via a gas-phase proton transfer reaction between a protonated solvent molecule and an analyte. The mass spectra of organic volatile compounds showed abundant protonated molecules with little fragmentation, being very similar to those produced by normal liquid ESI. The quantitative performance of the system was evaluated by determining the limit of detection (LOD), linearity ( r (2)), and repeatability (RSD). The GC-ESI/MS method was shown to be stable, providing high sensitivity and good quantitative performance.     

Transmit Diversity in the WCDMA System

This document presents the transmit diversityconcept adopted for the FDD mode of the thirdgenerationWCDMA system in ETSI in 1998. The open-loop mode isbased on the space-time block code attaining full diversity order with two transmit antennas.Different feedback modes are specified. They all utilizeterminal measurements in controlling the transmitweighting in the transmit antennas. The concept is described in detail for two transmit antennas.It is shown that very limited feedback from the terminalto the base, as defined for the FDD mode, can increasedownlink performance significantly when compared to single-antenna transmission.     

Drying of Solid Furl Particlbs in Hot Gases

Drying of solid fuel particles in hot gases ( 50-200c) is studied both theoretically and experimentally. The measurements are carried out by using a thermobalance reactor constructed for drying and pyrolysis studies of particles up to 30 mm by diameter. The model is based on the solution of the conservation equations for mass and energy. The drying is considered to consist of three successive periods: a short initial heating period, period of constant rate of drying and period of falling rate of drying. It is assumed that the particle moisture distribution is uniform during the constant rate of drying. Shrinking core model is assumed for the falling rate period. esides fuel particles, the model is applicable also for other solid particle drying processes. Model calculations are compared to measurements for wood chips. The model can predict the efFect of the main parameters reasonably well. These main parameters affecting the drying rate are: particle size, particle shape, initial particle moisture content, gas temperature and gas moisture content, emperature of the reactor walls and slip velocity. The irregular shape of practical fuel particles can approximately be simulated as one-dimensional case ( plate, cylinder, sphere) by using an equivalent volumc to surface area ratio.     

Calculation of constrained equilibria by Gibbs energy minimization

The Gibbs energy minimization encompasses active use of the chemical potentials (partial molar Gibbs energies) of the constituents of the system. Usually, these appear at their equilibrium values as a result of the minimization calculation, the mass balance constraints being the necessary subsidiary conditions. Yet, there are several such physico-chemical circumstances where the system is also constrained by other factors, such as surface effects, potential fields or even by chemical reaction kinetics. In this paper a particular method is presented by which constrained chemical potentials can be applied in a multi-phase Gibbs energy minimization. The constrained potentials arise typically from work-related thermodynamic displacements in the system. When Gibbs energy minimization is performed by the Lagrange method, these constraints appear as additional Lagrangian multipliers. Examples of the constrained potential method are presented in terms of the electrochemical Donnan equilibria in aqueous systems containing semi-permeable interfaces, the phase formation in surface-energy controlled systems and in systems with affinities controlled by chemical reaction kinetics. The methods have been applied successfully in calculating distribution coefficients for metal ions together with pH-values in pulp suspensions, in the calculation of surface tension of alloys, and in thermochemical process modeling involving chemical reaction rates.