基于MEMS的医用雾化微喷研究

介绍了一种基于MEMS技术的雾化微喷的设计、仿真、加工和实验结果。该微喷以压电效应为驱动方式,通过压电片振动所产生的压力使液体从阵列微喷孔中喷出,所产生的液滴直径和速度分布集中,无热效应,不会破坏药液的物理和化学特性。通过有限元仿真分析了微喷液体腔内压力波的分布,并根据仿真结果优化了微喷孔的布置。实验结果表明,该微喷所产生的液滴平均直径15μm,平均速度3m/s。     

Enhancement of pneumatic nebulization efficiency through application of an electric field

A technique is described for reducing the size of aerosol droplets produced by a pneumatic nebulizer of the kind commonly used in flame or plasma spectrometry. The technique involves the application of an electric field to the tip of the nebulizer, resulting in an induced surface charge on the liquid being nebulized. In turn, the surface charge reduces the liquid's surface tension and results in the generation of a finer aerosol. In this study, the effect of the electric field is quantified in terms of the spatial dispersion and size distribution of aerosol droplets formed in the presence and absence of the field. Droplet size distributions, obtained using the MgO impression technique and analyzed using log-normal and upper-limit functions, reveal a 63% decrease in the volume mean droplet diameter in the field's presence. As a result, this system is expected to be useful in both flame and plasma spectrometry, where reduced droplet size can yield improved precision and freedom from interferences.     

An improved single crystal adsorption calorimeter for determining gas adsorption and reaction energies on complex model catalysts

A new ultrahigh vacuum microcalorimeter for measuring heats of adsorption and adsorption-induced surface reactions on complex single crystal-based model surfaces is described. It has been specifically designed to study the interaction of gaseous molecules with well-defined model catalysts consisting of metal nanoparticles supported on single crystal surfaces or epitaxial thin oxide films grown on single crystals. The detection principle is based on the previously described measurement of the temperature rise upon adsorption of gaseous molecules by use of a pyroelectric polymer ribbon, which is brought into mechanical∕thermal contact with the back side of the thin single crystal. The instrument includes (i) a preparation chamber providing the required equipment to prepare supported model catalysts involving well-defined nanoparticles on clean single crystal surfaces and to characterize them using surface analysis techniques and in situ reflectivity measurements and (ii) the adsorption∕reaction chamber containing a molecular beam, a pyroelectric heat detector, and calibration tools for determining the absolute reactant fluxes and adsorption heats. The molecular beam is produced by a differentially pumped source based on a multichannel array capable of providing variable fluxes of both high and low vapor pressure gaseous molecules in the range of 0.005-1.5 × 10(15) molecules?cm(-2)?s(-1) and is modulated by means of the computer-controlled chopper with the shortest pulse length of 150 ms. The calorimetric measurements of adsorption and reaction heats can be performed in a broad temperature range from 100 to 300 K. A novel vibrational isolation method for the pyroelectric detector is introduced for the reduction of acoustic noise. The detector shows a pulse-to-pulse standard deviation ≤15 nJ when heat pulses in the range of 190-3600 nJ are applied to the sample surface with a chopped laser. Particularly for CO adsorption on Pt(111), the energy input of 15 nJ (or 120 nJ?cm(-2)) corresponds to the detection limit for adsorption of less than 1.5 × 10(12) CO molecules?cm(-2) or less than 0.1% of the monolayer coverage (with respect to the 1.5 × 10(15) surface Pt atoms?cm(-2)). The absolute accuracy in energy is within ～7%-9%. As a test of the new calorimeter, the adsorption heats of CO on Pt(111) at different temperatures were measured and compared to previously obtained calorimetric data at 300 K.     

一种压电致动网孔式雾化器的设计

新型的压电致动网孔式雾化器基于微机械加工技术,具有雾滴直径小,功率小,效率高等优点.介绍了一种压电致动网孔式雾化器的原理,对主要部件换能器进行了符合设计要求的纵向振动有限元分析,并阐述了各个因数对换能器振动的影响,获得的结果为换能器的优化设计提供了参考.     

A study on conformational changes by electron charges in viologen single molecules by using STM

The topography of self-assembled viologen derivatives (VC(8)SH, VC(10)SH, HSC(8)VC(8)SH, and HSC(10)VC(10)SH) molecules on an octanethiol (C(8)) self-assembled monolayer (SAM) modified gold surface was measured using ultrahigh-vacuum scanning tunneling microscopy (UHV-STM). We demonstrate here a novel matrix SAM appropriate for isolation of the viologen molecules. The C(8) was used for a matrix SAM, in which the VC(8)SH, VC(10)SH, HSC(8)VC(8)SH, and HSC(10)VC(10)SH were inserted at molecular lattice defects. The isolated single molecules of viologen derivatives inserted in the matrix SAM were observed as protrusions in STM topography using a constant current mode. We measured the topographic heights (VC(8)SH: 1.53nm, VC(10)SH: 2.01nm, HSC(8)VC(8)SH: 2.71nm, and HSC(10)VC(10)SH: 3.3nm) of the molecular protrusions using STM. Also, changes in the central axis of viologen molecules were observed as VC(8)SH (0.5-0.73nm), VC(10)SH (0.4-0.74nm), HSC(8)VC(8)SH (0.67-0.84nm), and HSC(10)VC(10)SH (0.67-0.99nm), respectively.     

The application of X-ray analysis in the transmission electron analytical microscope (T.E.A.M.) to the quantitative bulk analysis of biological microsamples

This paper describes: (a) methods for the high and low temperature ashing of biological tissue samples about 10^?4–10^?5 g in weight; (b) a method of spraying the solubilized ash on to specimen grids which produces droplets of a size convenient for their quantitative analysis in a transmission electron analytical microscope (T.E.A.M.), but without the need to know the actual volume of individual droplets; (c) the construction of standard curves for determining the absolute concentration of Na, Mg, P, S, K, and Ca simultaneously in a given sample. For most of the elements the error in analysis was about 5% or less. It was proposed that the technique is useful for detecting local element-compartments in complex tissues, and thus may be an important aid in the interpretation of the results of point analyses performed on sections taken from adjacent micro-volumes.     

Pulsed rotating supersonic source for merged molecular beams

We describe a pulsed rotating supersonic beam source, evolved from an ancestral device [M. Gupta and D. Herschbach, J. Phys. Chem. A 105, 1626 (2001)]. The beam emerges from a nozzle near the tip of a hollow rotor which can be spun at high-speed to shift the molecular velocity distribution downward or upward over a wide range. Here we consider mostly the slowing mode. Introducing a pulsed gas inlet system, cryocooling, and a shutter gate eliminated the main handicap of the original device in which continuous gas flow imposed high background pressure. The new version provides intense pulses, of duration 0.1-0.6 ms (depending on rotor speed) and containing ～10(12) molecules at lab speeds as low as 35 m/s and ～10(15) molecules at 400 m∕s. Beams of any molecule available as a gas can be slowed (or speeded); e.g., we have produced slow and fast beams of rare gases, O(2), Cl(2), NO(2), NH(3), and SF(6). For collision experiments, the ability to scan the beam speed by merely adjusting the rotor is especially advantageous when using two merged beams. By closely matching the beam speeds, very low relative collision energies can be attained without making either beam very slow.     

Near-field effects in single molecule emission

We present the first experimental proof of the influence of a nearby nano-sized metal object on the angular photon emission by a single molecule. A novel angular sensitive detection scheme is implemented in an existing near-field scanning optical microscope (NSOM). The positioning accuracy (∼1 nm) of the NSOM allows a systematic investigation of the intensity ratio between two different half-spaces as a function of the position of the metal–glass interfaces of the probe with respect to the single emitter. The observed effects are shown to be particularly strong for molecules that are excited mainly below the rims of the aperture. An excellent agreement is found between experiments and numerical simulations for these molecules. The observed angular redistribution of the angular emission of a single molecule could explain the alteration of the emission polarization observed for certain molecules in earlier experiments (Veerman et al. (1999) J. Microsc. 194 , 477–482).     

Removal of submicron aerosol particles and bioaerosols using carbon fiber ionizer assisted fibrous medium filter media

This paper reports the installation of a carbon fiber ionizer in front of a fibrous medium filter to enhance the removal of submicron aerosol particles and bioaerosols. Test particles (KCl) were classified with a size range of 50–600 nm using a differential mobility analyzer (DMA). The number concentration of the test particles was measured using a condensation particle counter (CPC). The average charge per particle was estimated by current measurements using an aerosol electrometer. At the face velocity of 0.5 m/s, the particle removal efficiency was 31.4% (for d_p=100 nm) when the ionizers were not operating but increased to 35.7% and 46.9% at 1.6×10¹¹ions/s and 6.4×10¹²ions/s with the ionizers, respectively. For the antibacterial tests, the test bioaerosols (E. coli) were aerosolized using a nebulizer and were deposited on the filter media for 5 minutes. After the deposited bioaerosols were exposed to unipolar air ions, they were incubated for 12 hours. The survival efficiency of E. coli was measured using a colony counting method. The survival fractions of E. coli exposed to positive air ions for 1, 5 and 10 minutes were 61.7%, 45.4% and 25.2%, respectively. This paper was presented at the 7th JSME-KSME Thermal and Fluids Engineering Conference, Sapporo, Japan, October 2008. Jungho Hwang received his B.S. and M.S. degree in Department of Mechanical Engineering from Seoul National University, South Korea, in 1983 and 1985, respectively. He received his Ph.D. degree from UC Berkeley in 1991. Dr. Hwang is currently a Professor at the School of Mechanical Engineering at Yonsei University in Seoul, Korea. Dr. Hwang’s research interests include aerosols, air cleaning and thermal environmental engineering.     

基于纳米锥森林的三维SERS基底检测miRNA

表面增强拉曼散射(SERS)是一种从存在于不同化学或生物环境中的分子中获取振动信息的强大技术。本文提出了一种基于纳米锥森林结构的三维SERS基底。制备基板采用等离子体处理技术,这项技术是一种简单、快速和高通量的方法。制备的基于纳米锥森林的SERS基底具有很高的灵敏度。实验表明,该基底可以检测到浓度低至10-10 M的miRNA。同时,所制备的SERS基底在大面积上表现出高度的均匀性。这些实验结果表明该3D SERS基底在广泛应用中的巨大潜力。     

Effect of Black Sea bream extracts on cytokine production in lipopolysaccharide-induced inflammation

We investigated the effect of black sea bream extracts on changes in pro-inflammatory and anti-inflammatory cytokines induced by lipopolysaccharide (LPS) in murine splenocytes. The levels of pro-inflammatory cytokines [interleukin (IL)-6, tumor necrosis factor-α (TNF-α), IL-12/IL-23(p40) and IL-17A] and anti-inflammatory cytokines [IL-4, IL-10 and interferon-γ (IFN-γ)] were assessed. Incubation of murine splenocytes with acetone+methylene chloride (A+M) and methanol (MeOH) extracts significantly decreased LPS-induced IL-6, IL-12/IL-23(p40) and IL-17A productions after 6 h incubation (p < 0.05). The A+M and MeOH extracts significantly increased LPS-induced IL-4 and IFN-γ productions at 48 and 72 h incubation (p < 0.05). Treatment with A+M extract resulted in significantly higher IL-10 production in splenocytes after 72 h (p < 0.05). Conclusively, black sea bream extracts were shown to be efficient in falling several pro-inflammatory cytokines while rising anti-inflammatory cytokines. Thus our results suggest that black sea bream extracts selectivity modulate immune events.     

Methods for determining the composition of nasal fluid by X-ray microanalysis

The nasal fluid is an easily accessible form of airway surface liquid. The objective of this study was to find a technically easy and reproducible method for sampling and analysis of this fluid. In a pilot study, several methods to carry out X-ray microanalysis of sub-microliter droplets were compared. Acceptable results were obtained with several of these methods (pipeting on filter paper or analysis of frozen-hydrated droplets at low temperature). Nasal fluid was collected from the inferior turbinate with a micropipette after occlusion of a nostril for 5-10 minutes. Ion concentrations in nasal fluid from six control subjects were (in mM, mean +/- standard error): sodium (Na) 127 +/- 6, chloride (Cl) 140 +/- 7, potassium (K) 27 +/- 3, and calcium (Ca) 5 +/- 1. This sampling method proved difficult to apply to cystic fibrosis (CF) patients because of the viscous quality of their nasal secretion. Therefore, an alternative method was devised. Sephadex G-25, ion exchange beads were mounted on double-sided tape, which was stuck on a filter paper as support. The filter paper was applied for 10 minutes to the nostril of a subject, and kept loosely in place. During the exposure period, the nasal fluid equilibrates with the beads. After removal of the filter paper with the beads from the nostril, the beads were rinsed with a hydrophobic volatile silicone oil to remove excess nasal fluid, dried, and analyzed. This method of collection is not cumbersome for the subject and gives results similar to those obtained by the direct collection method: Na 142 +/- 28 mM, Cl 150 +/- 36 mM, K 43 +/- 10 mM (mean and standard error of four determinations). Small differences between the filter method and the bead method can be explained by the fact that the filter method measured total nasal fluid, whereas the bead method measures predominantly the fluid component. Subjects suffering from mild respiratory illness or rhinitis had higher values for Na, K, and Cl in their nasal fluid.     

Single molecular conductance measurements of molecular junction of Au/1,4-phenylenediamine/Au

It was reported recently that the diamine-terminated molecules show two sets of single molecular conductance peaks in the conductance histogram. Although we found another set of conductance value of 1,4-diaminobutane in a lower current range, it was difficult to determine the conductivity definitely because the compound has different conformations with different gauche contents within its molecular chain. To make it easier to determine and analyze a single molecular conductance we measured here the conductance of 1,4-phenylenediamine, whose conformation cannot be changed in terms of the gauche contents. As a result, new sets of conductance other than those reported recently [L. Venkataraman, J.E. Klare, C. Nuckolls, M.S. Hybertsen, M.L. Steigerwald, Nature 442 (2006) 904] were observed.     

A study on the contact angles of a water droplet on smooth and rough solid surfaces

We investigated the wetting characteristics such as contact angle, wetting radius and topography of water droplets on smooth and random solid surfaces. Molecular dynamic simulation is employed to analyze the wetting behavior of water droplets on smooth and rough surfaces by considering different potential energy models of bond, angle, Lennard-Jones and Coulomb to calculate the interacting forces between water molecules. The Lennard-Jones potential energy model is adopted as an interaction model between water molecules and solid surface atoms. The randomly rough surface is generated by changing the standard deviation of roughness height from 1 Å to 3 Å with the fixed autocorrelation length. The size of water droplet considered is in the range from 2,000 to 5,000 molecules. The contact angles increase generally with increasing number of water molecules. For a hydrophobic surface whose characteristic energy is 0.1 kcal/mol, the contact angles depend rarely on the standard deviation of the roughness height. However, when the surface energy is 0.5 and 1.0 kcal/mol, the contact angles depend on both the roughness height of surfaces and droplet size.     

A compact setup to study homogeneous nucleation and condensation

An experiment is presented to study homogeneous nucleation and the subsequent droplet growth at high temperatures and high pressures in a compact setup that does not use moving parts. Nucleation and condensation are induced in an adiabatic, stationary expansion of the vapor and an inert carrier gas through a Laval nozzle. The adiabatic expansion is driven against atmospheric pressure by pressurized inert gas its mass flow carefully controlled. This allows us to avoid large pumps or vacuum storage tanks. Because we eventually want to study the homogeneous nucleation and condensation of zinc, the use of carefully chosen materials is required that can withstand pressures of up to 10(6) Pa resulting from mass flow rates of up to 600 l(N) min(-1) and temperatures up to 1200 K in the presence of highly corrosive zinc vapor. To observe the formation of droplets a laser beam propagates along the axis of the nozzle and the light scattered by the droplets is detected perpendicularly to the nozzle axis. An ICCD camera allows to record the scattered light through fused silica windows in the diverging part of the nozzle spatially resolved and to detect nucleation and condensation coherently in a single exposure. For the data analysis, a model is needed to describe the isentropic core part of the flow along the nozzle axis. The model must incorporate the laws of fluid dynamics, the nucleation and condensation process, and has to predict the size distribution of the particles created (PSD) at every position along the nozzle axis. Assuming Rayleigh scattering, the intensity of the scattered light can then be calculated from the second moment of the PSD.     

Performance of a Dual Sample Introduction System with Conventional Concentric Nebulizers for Simultaneous Determination of Hydride and Non-Hydride Forming Elements by ICP-OES

Abstract

A dual sample introduction system that combines the benefits of nebulization and vapour generation in a single device is described. It consists of two commercial conventional concentric nebulizers coupled to a modified cyclonic chamber. The effect(s) of the solvent load produced by the amount of liquid carried for the system by the two nebulizer assemblies is investigated. Better sensitivities, similar precision and DL's (with the exception of hydride forming elements) were obtained compared with those obtained with the system working in single mode. Long term stability was less than 7% with the dual mode, being 2% and 6% for the non-hydride and hydride forming elements, respectively, in the single mode operation. DL's obtained are of the same order of magnitude as those reported by several authors, with the exception of Se whose conditions were in compromise with the optimal reached for the rest of the elements. Accuracy of the dual system was proved by analyzing NIST 1648, urban particulate matter, with satisfactory results.     

基于AFM的微滴检测装置悬臂长度对检测信号的影响

利用原子力显微镜（AFM）具有纳米级高分辨率的特点，采用聚酯悬臂感应微小液滴重量所产生的挠度，从而达到实时检测微滴量的目的。通过单片机控制CMOS管的方法产生正脉宽只有8～10的脉冲，来实现利盟（LEXMARK）喷墨头的可控喷射，从而产生检测所需的可控微滴。最后试验检测系统的信噪比，实验不同悬臂长度对检测信号的影响。     

Localization of soluble major histocompatibility class II-peptide complexes on T cell surface

Affinity purified major histocompatibility (MHC)-peptide complexes are heterodimeric cell surface glycoproteins and are known to recognize antigen-specific CD4(+) T cell receptors (TCRs). In general, the affinity of MHC-peptide complexes to TCRs are considered very low with a K(D) of 5 x 10(-5) M and, therefore, stabilization of these complexes on T cell surface was not reported earlier. This could be due to (1) incomplete occupancy of MHC molecules with antigenic peptides, (2) variability of the binding constant of peptides to MHC molecules, (3) presence of endogenously bound peptides in MHC preparations, or (4) a combination of these. Using well-characterized HLA-DR2 complex loaded with a high affinity immunodominant epitope analog from human myelin basic protein (MBP), which shows release of gamma-IFN by specific stimulation of transformed human T cell clone (SS8T). The present report demonstrates a method for the localization of bound MHC class II-peptide complexes on T cell surface by backscatter electron imaging using in-lens Field Emission Scanning Electron Microscopy (FESEM). The localization is specific to the complex recognized by the TCR on MHC class II (DR2) and MBP peptide restricted human T cells.     

Combining optical tweezers and scanning probe microscopy to study DNA-protein interactions

We present the first results obtained with a new instrument designed and built to study DNA-protein interactions at the single molecule level. This microscope combines optical tweezers with scanning probe microscopy and allows us to locate DNA-binding proteins on a single suspended DNA molecule. A single DNA molecule is stretched taut using the optical tweezers, while a probe is scanned along the molecule. Interaction forces between the probe and the sample are measured with the optical tweezers. The instrument thus enables us to correlate mechanical and functional properties of bound proteins with the tension within the DNA molecule. The typical friction force between a micropipette used as probe and a naked DNA molecule was found to be <1 pN. A 16 micro m DNA molecule with approximately 10-15 digoxygenin (DIG) molecules located over a 90 nm range in the middle of the DNA was used as a model system. By scanning with an antidigoxygenin (alpha-DIG) antibody-coated pipette we were able to localize these sites by exploiting the high binding affinity between this antibody-antigen pair. The estimated experimental resolution assuming an infinitesimally thin and rigid probe and a single alpha-DIG/DIG bond was 15 nm.