Preparation and characterization of zinc sulfide nanoparticles under high-gravity environment

Nanosized ZnS particles were prepared under high-gravity environment generated by the rotating packed bed reactor (RPBR) using zinc nitrate solution and hydrogen sulfide gas as raw materials. The effects of experimental conditions such as reactant concentration, reaction temperature, rotating speed of the RPBR and aging time, on the preparation of nanosized ZnS particles were investigated. A set of suitable operating parameters (the aging time of 48 h, concentration of zinc nitrate of 0.1 mol/l, reaction temperature of 45 °C and rotating speed of the RPBR of 1500-1800 rotation/min) for the preparation of nanosized ZnS were recommended. Under these optimum conditions, well-dispersed ZnS nanoparticles was obtained. The crystal structure, optical properties, size and morphology of the product were also characterized by XRD, UV-Vis spectrophotometer, and TEM, respectively. Results indicate that the prepared ZnS has a good absorption for light in the wavelength range of 200-330 nm. XRD analysis also shows the prepared ZnS is in a sphalerite crystal phase. The process has great potential of commercialization.     

TREC chemical information retrieval - An initial evaluation effort for chemical IR systems

There is little need to emphasize the importance of chemoinformatics and chemical information retrieval. However, what seems to require a lot more effort in convincing members of the community is the need for standardized evaluation procedures and measures. How confident are we, as users, that the search tools we used have given us all the information that we were looking for? It is unrealistic to believe a marketing campaign which claims that a specific patent IR (information retrieval) system can find all relevant results for a search topic. And if we don’t trust marketing campaigns, how can we get an idea of what to expect from a patent search engine?One of the most prominent initiatives to work in this direction, of evaluating chemical IR tools, has started in 2009 with the support of NIST (National Institute for Standards and Technology): the TREC Chemical IR Track focuses on evaluation of search technologies for retrieval and knowledge discovery of digitally stored information on chemical patents and academic journal articles on chemistry. This paper describes our 2009 experience, presents the official results of the participating groups, and lays down the targets for 2010.     

Pressure-mediated doping in graphene

Exfoliated graphene and few layer graphene samples supported on SiO(2) have been studied by Raman spectroscopy at high pressure. For samples immersed on a alcohol mixture, an electron transfer of ?n/?P ～ 8 × 10(12) cm(-2) GPa(-1) is observed for monolayer and bilayer graphene, leading to giant doping values of n ～ 6 × 10(13) cm(-2) at the maximum pressure of 7 GPa. Three independent and consistent proofs of the doping process are obtained from (i) the evolution of the Raman G-band to 2D-band intensity ratio, (ii) the pressure coefficient of the G-band frequency, and (iii) the 2D band components splitting in the case of the bilayer sample. The charge transfer phenomena is absent for trilayer samples and for samples immersed in argon or nitrogen. We also show that a phase transition from a 2D biaxial strain response, resulting from the substrate drag upon volume reduction, to a 3D hydrostatic compression takes place when going from the bilayer to the trilayer sample. By model calculations we relate this transition to the unbinding of the graphene-SiO(2) system when increasing the number of graphene layers and as function of the surface roughness parameters. We propose that the formation of silanol groups on the SiO(2) substrate allows for a capacitance-induced substrate-mediated charge transfer.     

Simultaneous PIV/OH-PLIF, Rayleigh thermometry/OH-PLIF and stereo PIV measurements in a low-swirl flame

The diagnostic techniques for simultaneous velocity and relative OH distribution, simultaneous temperature and relative OH distribution, and three component velocity mapping are described. The data extracted from the measurements include statistical moments for inflow fluid dynamics, temperature, conditional velocities, and scalar flux. The work is a first step in the development of a detailed large eddy simulation (LES) validation database for a turbulent, premixed flame. The low-swirl burner used in this investigation has many of the necessary attributes for LES model validation, including a simplified interior geometry; it operates well into the thin reaction zone for turbulent premixed flames, and flame stabilization is based entirely on the flow field and not on hardware or pilot flames.     

Molecular beacon lighting up on graphene oxide

A molecular beacon (MB) is comprised of a fluorophore and a quencher linked by a DNA hairpin. MBs have been widely used for homogeneous DNA detection. In addition to molecular quenchers, many nanomaterials such as graphene oxide (GO) also possess excellent quenching efficiency. Most reported fluorescent sensors relied on DNA probes physisorbed by GO, which may suffer from nonspecific probe displacement and false positive signal. In this work, we report the preparation and characterization of a MB using graphene oxide (GO) as quencher, where an amino and FAM (6-carboxyfluorescein) dual labeled DNA was covalently attached to GO via an amide linkage. A major challenge was to remove noncovalently attached probes due to strong DNA adsorption by GO. While DNA desorption was favored at low salt, high pH, high temperature, and by using organic solvents, the cDNA was required to achieve complete desorption of noncovalently linked DNA probes. The DNA adsorption energy was measured using isothermal titration calorimetry, revealing the heterogeneous nature of GO. The covalent probe has a detection limit of 2.2 nM using a sample volume of 0.05 mL. With a 2 mL sample, the detection limit can reach 150 pM. The covalent probe is highly resistant to nonspecific probe displacement and will find applications in serum and cellular samples where high probe stability is demanded.     

DNA-directed synthesis of zinc oxide nanowires on carbon nanotube tips

This paper describes a class of three component hybrid nanowires templated by DNA directed self-assembly. Through the modification of carbon nanotube (CNT) termini with synthetic DNA oligonucleotides, gold nanoparticles are delivered, via DNA hybridization, to CNT tips that then serve as growth sites for zinc oxide (ZnO) nanowires. The structures we have generated using DNA templating represent an advance toward building higher order sequenced one dimensional nanostructures with rational control.     

Optical gain and stimulated emission in periodic nanopatterned crystalline silicon

Persistent efforts have been made to achieve efficient light emission from silicon in the hope of extending the reach of silicon technology into fully integrated optoelectronic circuits, meeting the needs for high-bandwidth intrachip and interchip connects. Enhanced light emission from silicon is known to be theoretically possible, enabled mostly through quantum-confinement effects. Furthermore, Raman-laser conversion was demonstrated in silicon waveguides. Here we report on optical gain and stimulated emission in uniaxially nanopatterned silicon-on-insulator using a nanopore array as an etching mask. In edge-emission measurements, we observed threshold behaviour, optical gain, longitudinal cavity modes and linewidth narrowing, along with a collimated far-field pattern, all indicative of amplification and stimulated emission. The sub-bandgap 1,278 nm emission peak is attributed to A-centre mediated phononless direct recombination between trapped electrons and free holes. The controlled nanoscale silicon engineering, combined with the low material loss in this sub-bandgap spectral range and the long electron lifetime in such A-type trapping centres, gives rise to the measured optical gain and stimulated emission and provides a new pathway to enhance light emission from silicon.     

Dry Coupling Ultrasonic High Frequency (10–100 MHz) Sensors for Detection of Surface and Tribological Properties at a Submicrometric Scale

Acoustic plane sensors adequately pressed against materials are suitable to measure elastic constants from flight-time measurement, without any coupling fluid for high temperature, with longitudinal and transverse acoustic waves in the megacycle range. Soft delay lines are generally used to match the sample roughness and to make mechanical play correction easier. At the opposite, our sensors use a hard delay line with a mirror-polished end surface. An experimental set-up is presented to perform acoustic reflection measurement in various contact conditions by increasing the applied mechanical load. The frequency dependence of this parameter is also measured in the 10- to 100-MHz range. Reproducibility tests are presented to validate this experimental set-up, but the main results concern the surprising ability of this technique to detect surface property modifications limited to thickness less than 1 m. Indeed, surface modification induced by different solvents on glass substrates has been detected by this means. This technique has also been used to detect surface property modifications of lixiviated glasses. In this case, atomic force microscopy and inductively coupled plasma analyses have demonstrated that the earlier stage of the surface damage had been detected whereas the thickness altered by ionic diffusion was less than 100 nm with almost no roughness variation. Similarly, tests on mechanically scratched glasses have shown that samples with an average roughness, respectively, of 4 and 120 nm were easily identified from their reflection coefficient versus load curves. Moreover, the pressure dependence of the acoustic reflection is used to estimate the contact stiffness and the contact area between the sensor and the material as a function of the applied compressive stress for contact, adhesion, and friction investigations.     

Pharmacologic management of common lower respiratory tract disorders in women

In a primary care setting, nurse-midwives will collaboratively manage common lower respiratory conditions that require pharmacologic therapy. As such, they must maintain up-to-date knowledge about the indications, use, and potential side effects of these medications. This article reviews the drugs most commonly used for the out-patient treatment of pneumonia, asthma, tuberculosis, and bronchitis (both acute and chronic). Differences among common oral antibiotics recommended by the American Thoracic Society are described. Inhaled bronchodilator and anti-inflammatory medications are covered, as well as systemic corticosteroids. The use of isoniazid preventive therapy for latent tuberculous infection is described in detail, with brief mention made of other drugs used for active tuberculosis. Adjunct treatments including immunotherapy, vaccines, oxygen supplementation, and nicotine replacement for smoking cessation also are discussed.