A feasible approach to all-electronic digital labeling and readout for cell identification

We present two critical innovations that enable a unique, purely electronic approach to microfluidic whole-cell analysis, focusing on the problem of cell identification and sorting. We used fully-scalable lithographic techniques to microfabricate digital barcodes, providing a means for low-cost, large volume production. We have demonstrated molecular functionalization of the barcodes, using biotin-streptavidin, as well as human CD4 antibody, and we have successfully linked the barcodes to polystyrene beads using the biotin-streptavidin complex. This functionalization allows unique barcodes to be attached to specific cell types, based on phenotype. We have also implemented an electronic barcode readout scheme, using a radio frequency microsensor integrated in an elastomeric microfluidic channel, that can read individual barcodes at rates in excess of 1000 labels s(-1). The barcodes are biologically compatible, and coupled with the electronic sensing technology, provide a route to compact, inexpensive, disposable cell identification, sorting and purification.     

Optimization of CE-ESI-MS Parameters for the Analysis of Ecstasy and Derivatives in Urine

Capillary electrophoresis (CE) was interfaced with a quadrupole mass spectrometer, using pneumatically-assisted electrospray ionization (ESI) in order to analyze Ecstasy and derivatives in urine. The influence of the sheath liquid composition, including the type and the percentage of the organic solvent, as well as the nature of the conductive acid modifier, were examined in order to find optimal coupling conditions. A fractional factorial design was also used to optimize the electrospray experimental parameters, such as the nebulizing gas pressure, the electrospray voltage, the drying gas flow rate, the drying gas temperature, the skimmer voltage, and the sheath liquid flow rate. The separation conditions were optimized in terms of temperature, electrolyte concentration, percentage of organic modifier, as well as capillary type. Finally, the optimal CE-ESI-MS conditions were applied to the analysis of Ecstasy and other related amphetamines in urine samples, following a liquid-liquid extraction procedure.     

Evaluation of solid-phase microextraction desorption parameters for fast GC analysis of cocaine in coca leaves

By its simplicity and rapidity, solid-phase microextraction (SPME) appears as an interesting alternative for sample introduction in fast gas chromatography (fast GC). This combination depends on numerous parameters affecting the desorption step (i.e., the release of compounds from the SPME fiber coating to the GC column). In this study, different liner diameters, injection temperatures, and gas flow rates are evaluated to accelerate the thermal desorption process in the injection port. This process is followed with real-time direct coupling a split/splitless injector to a mass spectrometer by means of a short capillary. It is shown that an effective, quantitative, and rapid transfer of cocaine (COC) and cocaethylene (CE) is performed with a 0.75-mm i.d. liner, at 280 degrees C and 4 mL/min gas flow rate. The 7-microm polydimethylsiloxane (PDMS) coating is selected for combination with fast GC because the 100-microm PDMS fiber presents some limitations caused by fiber bleeding. Finally, the developed SPME-fast GC method is applied to perform in less than 5 min, the quantitation of COC extracted from coca leaves by focused microwave-assisted extraction. An amount of 7.6 +/- 0.5 mg of COC per gram of dry mass is found, which is in good agreement with previously published results.     

Strain state in bcc Fe films grown on Si(1 1 1)

The strain state of Fe films grown on Si(1 1 1) has been investigated by X-ray diffraction (XRD) in the thickness range between 11 and 304 monolayers. Fe grows tetragonally distorted with the orientation relationship Fe(1 1 1) // Si(1 1 1) . At low coverage, the films grow pseudomorphic. Above 15 monolayers the films are characterized by the coexistence of a pseudomorphic phase with another one which relaxes with the Fe thickness. This relaxation proceeds rapidly in the earlier stages then slowly with the film thickness. The XRD characterization allows one to obtain quantitative information on the in-plane and out-of-plane strains.     

High power all-fibered femtosecond master oscillator power amplifier at 1.56 μm

Direct amplification of output from chirped pulse oscillator (CPO) to 3.3?W of average power (pulse energy of 118?nJ in 20?ps pulse duration before compression) was achieved in a properly designed cladding pumped large mode area Er-doped fiber. Various configurations of CPO cavity with different FWHM of output spectrum and pulse duration were investigated. Fourier limit compression with 480?fs pulse duration and 32?kW peak power has been obtained for pulses with 14.8?nm FWHM spectrum. Subsequent nonlinear compression in a standard SMF-28 fiber yielded pulses as short as 145?fs.     

Modeling of micro-perforated panels in a complex vibro-acoustic environment using patch transfer function approach

A micro-perforated panel (MPP) with a backing cavity is a well known device for efficient noise absorption. This configuration has been thoroughly studied in the experimental conditions of an acoustic tube (Kundt tube), in which the MPP is excited by a normal incident plane wave in one dimension. In a more practical situation, the efficiency of MPP may be influenced by the vibro-acoustic behavior of the surrounding systems as well as excitation. To deal with this problem, a vibro-acoustic formulation based on the patch transfer functions (PTF) approach is proposed to model the behavior of a micro-perforated structure in a complex vibro-acoustic environment. PTF is a substructuring approach, which allows assembling different vibro-acoustic subsystems through coupled surfaces. Upon casting micro-perforations and the flexibility of the MPP under transfer function framework, the proposed PTF formulation provides explicit representation of the coupling between subsystems and facilitates physical interpretation. As an illustration example, application to a MPP with a backing cavity located in an infinite baffle is demonstrated. The proposed PTF formulation is finally validated through comparison with experimental measurements available in the literature.     

Rapid separation of basic drugs by nonaqueous capillary electrophoresis

Summary Nonaqueous capillary electrophoresis (NACE) has been used to achieve rapid separations of basic drugs. A high electric field was obtained by using short capillaries. Baseline separations of basic drugs, including amphetamines, tropane alkaloids and local anesthetics, were achieved in 1 min by selection of the appropriate organic solvent and electrolyte composition. Thus, high-throughput analyses can be performed. Peak efficiency up to 9154 theoretical plates s⁻¹ was achieved in a separation performed at 923V cm⁻¹. No discernible loss in resolution was observed when a conventional capillary (64.5cm) was replaced by a short (32.5 cm) capillary.     

Injection and flow control system for microchannels

In spite of considerable efforts, flow control in micro-channels remains a challenge owing to the very small ratio of channel/supply-system volumes, as well as the induction of spurious flows by extremely small pressure or geometry changes. We present here an inexpensive and robust system for flow control in a microchannel system, based on a dynamic control of reservoir pressures at the end of each channel. This system allows flow equilibration with a time constant smaller than one second, and is also able to maintain stable flux from stopped flow to many microl min(-1) range over several hours. It is robust to changes in ambient pressure and temperature. This system further includes a feature for sub-microliter sample injection during the experiment. We quantify flow control in elastomer and thermoplastic channels, and demonstrate the impact on one application of the system, namely the reproducible, automated separation of large DNA by electrophoresis in a self-organized magnetic bead matrix in a microchannel.     

Spectroscopic characterization of microscopic hydrogen-bonding disparities in supercritical water

The local hydrogen-bonding environment in supercritical water (380 degrees C, 300 bars, density 0.54 gcm3) was studied by x-ray Raman scattering at the oxygen K edge. The spectra are compared to those of the gas phase, liquid surface, bulk liquid, and bulk ice, as well as to calculated spectra. The experimental model systems are used to assign spectral features and to quantify specific local hydrogen-bonding situations in supercritical water. The first coordination shell of the molecules is characterized in more detail with the aid of the calculations. Our analysis suggests that approximately 65% of the molecules in supercritical water are hydrogen bonded in configurations that are distinctly different from those in liquid water and ice. In contrast to liquid water the bonded molecules in supercritical water have four intact hydrogen bonds and in contrast to ice large variations of bond angles and distances are observed. The remaining approximately 35% of the molecules exhibit two free O-H bonds and are thus either not involved in hydrogen bonding at all or have one or two hydrogen bonds on the oxygen side. We determine an average O-O distance of 3.1+/-0.1 A in supercritical water for the H bonded molecules at the conditions studied here. This and the corresponding hydrogen bond lengths are shown to agree with neutron- and x-ray-diffraction data at similar conditions. Our results on the local hydrogen-bonding environment with mainly two disparate hydrogen-bonding configurations are consistent with an extended structural model of supercritical water as a heterogeneous system with small patches of bonded molecules in various tetrahedral configurations and surrounding nonbonded gas-phase-like molecules.     

Sur la ribosylation de divers mercapto-2 benzoazoles

A comparative study of the ribosylation reaction of various 2-mercaptobenzazoles using the three more usual techniques was performed: acid-catalyzed fusion, reaction of the silylated aglycones with 1-acetoxy and 1-halogeno sugars, respectively. For all the various 2-mercaptobenzazoles the N-nucleosides were obtained and fully characterized. The reactivity of 2-mercapto-benzimidazole is quite particular as we have noticed the formation of the corresponding N₁, N₃-diriboside and of an unusual 2-2-anhydro nueleoside.