Steering in computational science: Mesoscale modelling and simulation

This paper outlines the benefits of computational steering for high performance computing applications. Lattice-Boltzmann mesoscale fluid simulations of binary and ternary amphiphilic fluids in two and three dimensions are used to illustrate the substantial improvements which computational steering offers in terms of resource efficiency and time to discover new physics. We discuss details of our current steering implementations and describe their future outlook with the advent of computational grids.     

Deposition of antibacterial of poly(1,3-bis-(p-carboxyphenoxy propane)-co-(sebacic anhydride)) 20:80/gentamicin sulfate composite coatings by MAPLE

We report on thin film deposition of poly(1,3-bis-(p-carboxyphenoxy propane)-co-sebacic anhydride)) 20:80 thin films containing several gentamicin concentrations by matrix assisted pulsed laser evaporation (MAPLE). A pulsed KrF* excimer laser was used to deposit the polymer-drug composite thin films. Release of gentamicin from these MAPLE-deposited polymer conjugate structures was assessed. Fourier transform infrared spectroscopy was used to demonstrate that the functional groups of the MAPLE-transferred materials were not changed by the deposition process nor were new functional groups formed. Scanning electron microscopy confirmed that MAPLE may be used to fabricate thin films of good morphological quality. The activity of gentamicin-doped films against Escherichia coli and Staphylococcus aureus bacteria was demonstrated using disk diffusion and antibacterial drop test. Our studies indicate that deposition of polymer-drug composite thin films prepared by MAPLE is a suitable technique for performing controlled drug delivery. Antimicrobial thin film coatings have several medical applications, including use for indwelling catheters and implanted medical devices.     

空气中激光烧蚀Cu产生等离子体发射光谱的研究

利用Q-开关Nd:YAG激光器产生的1.06 μm、10 ns的脉冲激光聚焦在空气中的Cu靶上,观测了激光诱导的Cu等离子体发射光谱.采用不同的激光能量,分析了波长范围为440 nm到540 nm的空间分辨发射光谱.在局部热力学平衡(LTE)条件近似下,根据谱线的相对强度,得到了等离子体电子温度约在104 K以上,给出了靶面附近电子温度的空间演化规律,并探讨了N(Ⅱ)500.52 nm谱线的谱线强度和半高全宽随激光能量的变化规律.     

Spectroscopic monitoring of NO traces in plants and human breath: applications and perspectives

Optical methods based on quantum cascade lasers (QCLs) are becoming popular in many life science applications. We report on two trace gas detection schemes based on continuous wave QCLs for on-line detection of nitric oxide (NO) at the sub-part-per-billion level by volume (ppbv, 1:10^?9), using wavelength modulation spectroscopy (WMS) and Faraday rotation spectroscopy (FRS) at 1894 cm^?1 and 1875.73 cm^?1, respectively. Several technical incremental steps are discussed to further improve the sensitivity of these methods. Examples are included to demonstrate the merits of WMS-based sensor: direct monitoring of NO concentrations in exhaled breath, and from plants under pathogen attack. A simple hand-held breath sampling device that allows single breath collection at various exhalation flows (15, 50, 100 and 300 mL/s, respectively) is developed for off-line measurements and validated in combination with the WMS-based sensor. Additionally, the capability of plants to remove environmental NO is presented.     

Quantum cascade laser-based carbon monoxide detection on a second time scale from human breath

We present three different detection schemes for measuring carbon monoxide (CO) in direct absorption using a thermoelectrically cooled, distributed-feedback pulsed quantum cascade (qc) laser operating between 2176 and 2183 cm^-1. The laser emission has overlap with the strong R(8)1 ro-vibrational transition in CO at 2176.2835 cm^-1. Firstly, by utilizing the frequency chirp of the qc-laser with long laser pulses, a minimal detectable absorption of 1.2×10^-5 cm^-1 is achieved at an acquisition rate of 3 Hz. Additionally, with short laser pulses and slow frequency scanning a minimal detectable absorption 8.2×10^-7 cm^-1 is reported, with an acquisition time of 60 s. Finally, a novel amplitude modulation technique is developed to facilitate real-time measurement of CO in exhaled air. The application of this detector to detection of CO in a single breath as a potential non-invasive diagnostic tool is shown. PACS 07.07.Df; 42.62.Be     

Laser deposition of cryoglobulin blood proteins thin films by matrix assisted pulsed laser evaporation

We report the first successful deposition of type II cryoglobulin blood protein thin films by matrix assisted pulsed laser evaporation (MAPLE) using a KrF^* excimer laser source (λ = 248 nm, τ_FWHM ≈ 20 ns) operated at a repetition rate of 10 Hz. We demonstrate by AFM and FTIR that MAPLE-deposited thin films consist of starting type II cryoglobulin only, maintaining its chemical structure and biological functionality, being properly collected and processed. The dependence on incident laser fluence of the induced surface morphology is presented. The presence of type II cryoglobulin was revealed as aggregates of globular material in the MAPLE-deposited thin films and confirmed by standard cryoglobulin tests.     

Continuous wave optical parametric oscillator for quartz-enhanced photoacoustic trace gas sensing

A continuous wave optical parametric oscillator, generating up to 300 mW idler output in the 3–4 μm wavelength region, and pumped by a fiber-amplified DBR diode laser is used for trace gas detection by means of quartz-enhanced photoacoustic spectroscopy (QEPAS). Mode-hop-free tuning of the OPO output over 5.2 cm^-1 and continuous spectral coverage exceeding 16.5 cm^-1 were achieved via electronic pump source tuning alone. Online monitoring of the idler wavelength, with feedback to the DBR diode laser, provided an automated closed-loop control allowing arbitrary idler wavelength selection within the pump tuning range and locking of the idler wavelength with a stability of 1.7×10^-3 cm^-1 over at least 30 min. Using this approach, we locked the idler wavelength at an ethane absorption peak and obtained QEPAS data to verify the linear response of the QEPAS signal at different ethane concentrations (100 ppbv-20 ppmv) and different power levels. The detection limit for ethane was determined to be 13 ppbv (20 s averaging), corresponding to a normalized noise equivalent absorption coefficient of 4.4×10^-7 cm^-1  W/Hz^1/2. PACS 42.55.Wd; 42.65.Yj; 42.62.Fi     

Coupling Between the Discharge Plasma Instability and the Laser Oscillation in a He—Cd Laser

The investigation of the output of a He–Cd laser with electrically floating hollow electrodes shows that the discharge plasma instability plays an important role in the generation of the population inversion. The experimental evidence is presented and a qualitative interpretation is given by considering the plasma instability as equivalent to a radio frequency component of the discharge voltage.