Microspotting streptavidin and double-stranded DNA arrays on gold for high-throughput studies of protein-DNA interactions by surface plasmon resonance microscopy

We present two strategies for microspotting 10 x 12 arrays of double-stranded DNAs (dsDNAs) onto a gold-coated glass slide for high-throughput studies of protein-DNA interactions by surface plasmon resonance (SPR) microscopy. Both methods use streptavidin (SA) as a linker layer between a biotin-containing mixed self-assembled monolayer (SAM) and biotinylated dsDNAs to produce arrays with high packing density. The primary mixed SAM is produced from biotin- and oligo(ethylene glycol)-terminated thiols bonded as thiolates onto the gold surface. In the first method, a robotic microspotter is used to deliver nanoliter droplets of dsDNA solution onto a uniform layer of this SA ( approximately 2 x 10(12) SA/cm(2)). SPR microscopy shows a density of (5-6) x 10(11) dsDNA/cm(2) (0.2-0.3 dsDNA/SA) in the array elements. The second method uses instead a microspotted array of this SA linker layer, onto which the microspots of dsDNA are added with spatial registry. SPR microscopy before addition of the dsDNA shows a SA coverage of 2 x 10(12) SA/cm(2) within the spots and a dsDNA density of 8.5 +/- 3.5 x 10(11) dsDNA/cm(2) (0.3-0.7 dsDNA/SA, depending on the length of dsDNA) after dsDNA spotting. We demonstrate the ability to simultaneously monitor protein binding with the SPR microscope in many 200-microm spots with 1-s time resolution and sensitivity to <1 pg of protein.     

Diffusion of Hydrogen in Amorphous NiCrFeSiB Alloy

The diffusion of hydrogen in amorphous NiCrFeSiB alloy has been studied by electrochemicalmethod. In the temperature range of 20~50℃, diffusion coefficient of hydrogen in the alloy fol-lows the equation' D(cm2/s)= 9.27x10-8exp(-53.4 kJ/RT). At room temperature the diffusion.coefficient D and the solubility Co are 6.125x 10-12 cm2/s and 0.007 mol/cm3, respectively.When As2O3 is added into the cathodic solution or the charging current density is increased, thediffusion coefficient and solubility increase, and the difFusion activation energy decreases. Theinfluence of amorphous structure on diffusion and solution of hydrogen is discussed.     

Sooting behavior of ethanol droplet combustion at elevated pressures under microgravity conditions

Liquid ethanol is widely used in practical fuels as a means to extend petroleum-derived resources or as a fuel additive to reduce emissions of carbon monoxide from spark ignition engines. Recent research has also suggested that ethanol and other oxygenates could be added to diesel fuel to reduce particulate emissions. In this cursory study, the combustion of small ethanol droplets in microgravity environments was observed to investigate diffusion flame characteristics at higher ambient pressures and at various oxygen indices, all with nitrogen as the diluent species. At the NASA Glenn Research Center 2.2-second drop tower, free ethanol droplets were ignited in the Droplet Combustion Experiment (DCE) apparatus, and backlit and flame view data were collected to evaluate flame position and burning rate. Profuse sooting was noted above 3 atm ambient pressure. In experiments performed at the Japan Microgravity Center 10-second (JAMIC) drop shaft with Sooting Effects in Droplet Combustion (SEDC) apparatus, the first data that displayed a spherical sootshell for ethanol droplet combustion was obtained. Because of the strong sensitivity of soot formation to small changes in an easily accessible range of pressures, ethanol appears to be a simple liquid fuel suitable for fundamental studies of soot formation effects on spherical diffusion flames. The results impact discussions regarding the mechanism of particulate reduction by ethanol addition to fuels in high-pressure practical combustors.     

Temperature dependence of the Faraday effect in As-S glass fiber

Temperature dependence of the Faraday effect is investigated for As2S3 fiber at 3.39 microm, obtaining a Verdet constant V of 1.62 x 10(-2) min/cm x G at room temperature and a temperature-dependence term coefficient of 10.67 min x K/cm x G in the experiments. The V value obtained at 25 degrees C is consistent with the theoretical estimates based on the first derivative of known refractive indices with respect to the wavelength. The temperature-dependent term is also discussed theoretically.     

Sorption kinetics of polycyclic aromatic hydrocarbons removal using granular activated carbon: intraparticle diffusion coefficients

Granular activated carbon (GAC) was evaluated as a suitable sorbent for polycyclic aromatic hydrocarbons (PAHs) removal from aqueous solutions. For this purpose, kinetic measurements on the extraction of a family of six PAHs were taken. A morphology study was performed by means of a scanning electron microscopy (SEM) analysis of GAC samples. Analyses of the batch rate data for each PAH were carried out using two kinetic models: the homogenous particle diffusion model (HPDM) and the shell progressive model (SPM). The process was controlled by diffusion rate the solutes (PAHs) that penetrated the reacted layer at PAH concentrations in the range of 0.2-10 mg L(-1). The effective particle diffusion coefficients (D(eff)) derived from the two models were determined from the batch rate data. The Weber and Morris intraparticle diffusion model made a double contribution to the surface and pore diffusivities in the sorption process. The D(eff) values derived from both the HPMD and SPM equations varied from 1.1 x 10(-13) to 6.0 x 10(-14) m(2) s(-1). The simplest model, the pore diffusion model, was applied first for data analysis. The model of the next level of complexity, the surface diffusion model, was applied in order to gain a deeper understanding of the diffusion process. This model is able to explain the data, and the apparent surface diffusivities are in the same order of magnitude as the values for the sorption of functionalized aromatic hydrocarbons (phenols and sulphonates) that are described in the literature.     

Sn-Pb合金微粒的制备和微结构

采用均匀颗粒成型法(Uniform Droplet Spray—UDS)制备出Sn—5％Pb合金微粒，颗粒的粒度分布均匀，性能一致．用非绝热容量法测量了在N2—2％H2气氛下Sn—5％Pb微粒的焓，井分析了颗粒的显微结构，结果表明：Sn—5％Pb微粒具有较大的过冷度和亚稳态结构．     

Kinetics of degradation of sulphur mustard on impregnated carbons

Kinetics of degradation of sulphur mustard (HD) on the surface of NaOH/CrO3/C, NaOH/CrO3/EDA/C and RuCl3/C systems has been examined by using gas chromatography technique by extracting and analyzing the residual HD periodically. The carbons were prepared by impregnating activated carbon with 4% sodium hydroxide plus 3% Cr(VI) as CrO3 with and without 5% ethylene diamine (EDA) and 5% ruthenium chloride by using their aqueous solutions. Obtained carbons were characterized for surface area analysis by BET conventional method. Kinetic plots reveal that the observed reactions are fast at the initial stages, slow at the later stages and progress to a steady state indicating the first order behavior. Effect of moisture on kinetic rate is also observed. In the case of NaOH/CrO3/C system the rate constant is decreased from 13.36 to 5.53 x 10(-2) h(-1) and half life is increased from 5.2 to 12.54 h while moisture content is increased from 1.9% to 11.2%. Whereas, the rate constant of HD degradation reaction is decreased from 10.4 to 4.14 x 10(-2) h(-1) and half life is increased from 6.7 to 16.72 h while moisture content is increased from 2.1% to 10.8% on NaOH/CrO3/EDA/C. Reaction on RuCl3/C system also behaves in the similar manner. Extracted reaction products were characterized by GC/MS and it is found that on NaOH/CrO3/C, HD degrades to hemisulphur mustard, thiodiglycol and 1,4-oxathiane. Whereas, on NaOH/CrO3/EDA/C, HD is degraded to 1,4-thiazane and it is degraded to divinyl sulphone on RuCl3/C. All these investigations reveal that above mentioned carbons can be used in nuclear, biological and chemical (NBC) filtration systems for protection against sulphur mustard.     

Electrical readouts of single and few molecule systems in metal-molecule-metal device structures

Electrical conduction through molecular junctions are measured in different local environments through two test beds that are ideal for single/few molecule and molecular monolayer systems. A technique has been developed to realize Au films with approximately 1.5 A surface roughness comparable to the best available techniques and suitable for formation of patterned device structures. The technique utilizes room temperature e-beam evaporated Au films over oxidized Si substrates silanized with (3-mercaptopropyl)trimethoxysilane (MPTMS). The lateral (single/few molecule) and vertical (many molecules) device structures are both enabled by the process for realizing ultraflat Au layer. Lateral metal-molecule-metal (M-M-M) device structures are fabricated by forming pairs of Au electrodes with nanometer separation (nano-gap) through an electromigration-induced break-junction (EIBJ) technique at room temperature and conductivity measurements are carried out for dithiol functionalized single molecules. We have used the flat Au layer (using the current technique) as the bottom contact in vertical M-M-M device structures. Here, molecular self-assembly are formed on the Au surface, and patterned (20 x 20 microm2) top Au contacts were successfully transferred on to the device using a stamping technique (where the Au is deposited on a polydimethylsiloxane (PDMS) pad and following a physical contact on the thiolated Au layer). The single molecular property of XYL, a highly conductive molecule and many molecular property of HS-C9-SH, an insulating molecule in its molecular monolayer form are measured. Observation of enhanced conduction following molecular deposition, and comparison of conductance-voltage characteristics to those predicted theoretically, confirms the success of trapping single/few molecules in the nano-gap. The observed approximately 10(2) less conductance through the molecular monolayer of HS-C9-SH compared to the estimation of a linear sum of single molecule conductances over large area indicate that either all the molecules are not in physical contact with the top stamping electrode or electrode-molecule coupling has a less broadening in presence of it own environment or both.     

Radon diffusion coefficients in 360 waterproof materials of different chemical composition

This paper summarises the results of radon diffusion coefficient measurements in 360 common waterproof materials available throughout Europe. The materials were grouped into 26 categories according to their chemical composition. It was found that the diffusion coefficients of materials used for protecting houses against radon vary within eight orders from 10(-15) to 10(-8) m(2) s(-1). The lowest values were obtained for bitumen membranes with an Al carrier film and for ethylene vinyl acetate membranes. The highest radon diffusion coefficient values were discovered for sodium bentonite membranes, rubber membranes made of ethylene propylene diene monomer and polymer cement coatings. The radon diffusion coefficients for waterproofings widely used for protecting houses, i.e. flexible polyvinyl chloride, high-, low-density polyethylene, polypropylene and bitumen membranes, vary in the range from 3 × 10(-12) to 3 × 10(-11) m(2) s(-1). Tests were performed which confirmed that the radon diffusion coefficient is also an effective tool for verifying the air-tightness of joints.     

The Control on Size and Density of InAs QDs by Droplet Epitaxy (April 2009)

We report on the ability to grow InAs quantum dots (QDs) by droplet epitaxy (DE) using solid-source molecular beam epitaxy (MBE). In particular, the control of the size and density of InAs QDs at near room temperatures are achieved as a function of substrate temperature and crystallization condition. For a typical range of QD density ( ~10⁹ to 10¹⁰ cm^-2), the growth window is revealed to be fairly narrow ( ~20degC). In droplets are extremely sensitive to surface diffusion and arsenic background pressure even at near room temperatures. As a result, a very careful fabrication procedure is required to crystallize In droplets in order to fabricate desired shape of InAs QDs. For this purpose, we developed a double-step crystallization process, in which As background recovery and high-temperature crystallization are introduced. In addition, the results by DE are compared with QDs fabricated by Stranski-Krastanow (S-K) growth approach in terms of size and density. The results can find applications in optoelectronics as the fabrication of QDs by DE approach has more flexibility over S-K approach, i.e., more freedom of size and density control.     

Impregnated silica nanoparticles for the reactive removal of sulphur mustard from solutions

High surface area (887.3m(2)/g) silica nanoparticles were synthesized using aerogel route and thereafter, characterized by N(2)-Brunauer-Emmet-Teller (BET), SEM and TEM techniques. The data indicated the formation of nanoparticles of silica in the size range of 24-75 nm with mesoporous characteristics. Later, these were impregnated with reactive chemicals such as N-chloro compounds, oxaziridines, polyoxometalates, etc., which have already been proven to be effective against sulphur mustard (HD). Thus, developed novel mesoporous reactive sorbents were tested for their self-decontaminating feature by conducting studies on kinetics of adsorptive removal of HD from solution. Trichloroisocyanuric acid impregnated silica nanoparticles (10%, w/w)-based system was found to be the best with least half-life value (t(1/2)=2.8 min) among prepared systems to remove and detoxify HD into nontoxic degradation products. Hydrolysis, dehydrohalogenation and oxidation reactions were found to be the route of degradation of HD over prepared sorbents. The study also inferred that 10% loading of impregnants over high surface area and low density silica nanoparticles enhances the rate of reaction kinetics and seems to be useful in the field of heterogeneous reaction kinetics.     

Quantum Tunneling of D(H) Atoms and 2 – in Solid Hydrogen

This paper contains three results. First, the rate constants for the tunneling reaction HD + D H + D ₂ in solid HD increase steeply with increasing temperature above 5 K, while they are almost independent of temperature below 5 K. A mechanism of a vacancy–assisted tunneling reaction is proposed to account for this temperature dependence. Second, a hydrogen atom and a hydrogen molecule form a van der Waals complex in the Ar matrix at 20 K, where the tunneling reaction HD + D H + D ₂ takes place in this complex. The analysis of well–resolved ESR spectra of the complex determined the distance between a hydrogen atom and a hydrogen molecule as 2.3 – 2.5 Å. Third, the decay rate constants of anions in solid parahydrogen decrease with decreasing temperature below 6.6 K, attain the minimum value at 5 K, and then increase with decreasing temperature in the range of 5 2.7 K. The abnormal temperature dependence of the decay rate constants below 5 K is ascribed to a phonon–scattering process of quantum diffusion.     

A study of the extracorporeal rate of blood flow and blood pressure during hemodialysis

Hemodynamic instability is a common problem during hemodialysis (HD). The effect of blood flow rate (BFR) on blood pressure (BP) during HD has not been previously evaluated. Subjects receiving HD for the treatment of renal failure were enrolled (n=34). For each patient, during the last hour of 2 consecutive HD sessions the BFR was set at 200 mL/min for 30 min and at 400 mL/min for 30 min, during which period the fluid removal rate was kept constant. The order of the BFR alterations was randomized. The study procedure was repeated during the next HD session but with reversal of the order of the altered BFR. During each 30-min period, BP was recorded at baseline and subsequently every 10 min. During the BFR of 400 mL/min, subjects had a higher systolic BP by an average of 4.1 mmHg compared with the BFR of 200 mL/min (95% confidence interval [CI] 0.22-7.98; p=0.038). Similarly, during the BFR of 400 mL/min, subjects had a higher diastolic BP by an average of 3.04 mmHg compared with the BFR of 200 mL/min (95% CI 0.55-5.53; p=0.017). Likewise, during the BFR of 400 mL/min, subjects had a higher mean arterial pressure by an average of 3.44 mmHg (95% CI 0.77-6.11; p=0.012). The findings suggest that during HD, BPs are maintained higher at higher BFRs as compared with lower BFRs.     

MALDI-TOF-MS analysis of droplets prepared in an electrodynamic balance: "wall-less" sample preparation

Methodology enabling mass spectral analysis of the composition of droplet(s) prepared in an electrodynamic balance (EDB) by matrix-assisted laser desorption/ionization (MALDI) is described. The dc field surrounding the electrodynamic balance was manipulated to eject single droplets at a time from the EDB thereby causing their deposition onto a MALDI sample plate precoated with matrix. When the laser was directed onto the droplet(s) and held stationary, marked gains in the signal-to-noise and signal-to-background ratios were realized with each subsequent mass spectrum due to the suppression of matrix cluster ion formation. Optical microscopy of the plate, after 1024 laser shots were fired at eight droplets that had been deposited one on top of the other, revealed a residual island of droplet matter (area approximately 3.1 x 10(-9) m2) inside the region where the crystalline matrix had been ablated away within the laser spot (area approximately 1.6 x 10(-8) m2). Removing the predried crystalline matrix layer and, instead, adding matrix into the starting solution was found to be a more effective means of suppressing matrix cluster ion formation. The chemical composition of the droplet(s) prepared in the EDB is discussed with regard to sample preconcentration, the images of the laser spot after MALDI, matrix cluster ion suppression, and the possibility for improved quantitation and detection limits by MALDI-TOF-MS.     

Theoretical study of stable dropwise condensation on an inclined micro/nano-structured tube

In this paper, a numerical model for dropwise condensation on a micro/nano-structured inclined tube is developed based on previous theoretical and experimental studies for flat plates. Thermal resistances consisting of conduction through a droplet, vapor–liquid interfacial resistance, droplet curvature, promoter layer, and micro/nano-pillars are included into the model and incorporated in calculating the heat transfer rate across an individual droplet. Droplet morphologies (Wenzel, Cassie, and partially wetting) are considered in the model. Effects of various parameters are investigated on single droplets behaviors and total heat transfer. Results show that average droplets radii on a horizontal tube are higher than on a vertical tube; consequently, vertical tubes have better heat transfer rate. For example, vertical tubes have five times higher overall heat flux than horizontal tubes in some cases. In addition, partially wetting droplets have higher heat transfer rates in comparison with Wenzel or Cassie state in all configurations.     

Aerosol counterflow two-jets unit for continuous measurement of the soluble fraction of atmospheric aerosols

A new type of aerosol collector employing a liquid at laboratory temperature for continuous sampling of atmospheric particles is described. The collector operates on the principle of a Venturi scrubber. Sampled air flows at high linear velocity through two Venturi nozzles "atomizing" the liquid to form two jets of a polydisperse aerosol of fine droplets situated against each other. Counterflow jets of droplets collide, and within this process, the aerosol particles are captured into dispersed liquid. Under optimum conditions (air flow rate of 5 L/min and water flow rate of 2 mL/min), aerosol particles down to 0.3 microm in diameter are quantitatively collected in the collector into deionized water while the collection efficiency of smaller particles decreases. There is very little loss of fine aerosol within the aerosol counterflow two-jets unit (ACTJU). Coupling of the aerosol collector with an annular diffusion denuder located upstream of the collector ensures an artifact-free sampling of atmospheric aerosols. Operation of the ACTJU in combination with on-line detection devices allows in situ automated analysis of water-soluble aerosol species (e.g., NO2-, NO3-)with high time resolution (as high as 1 s). Under the optimum conditions, the limit of detection for particulate nitrite and nitrate is 28 and 77 ng/m(3), respectively. The instrument is sufficiently rugged for its application at routine monitoring of aerosol composition in the real time.     

High-performance nitrate-selective electrodes containing immobilized amino acid betaines as sensors

Ten nitrate-selective electrodes based upon rubbery membranes containing various betaine salts as sensors covalently bound to a cross-linked polystyrene-block-polybutadiene-block-polystyrene (SBS) polymer have been produced. The membranes were robust, highly selective, and effective over a pH range of 2-8. The best nitrate-selective electrode fabricated contained 10% m/m dicumyl peroxide, 40% 2-nitrophenyloctyl ether, 6.5% triallyl leucine betaine chloride and 43.5% SBS. The characteristics of this electrode were a linear Nernstian range of 1 x 10(-1) to 5 x 10(-6) mol dm(-3) NO3-, a limit of detection of 3.4 x 10(-7) mol dm(-3) NO3-, and a selectivity coefficient for nitrate against chloride, K(NO3-,Cl-)pot, of 3.4 x 10(-3). These figures represent a significant improvement on current commercial nitrate sensors. Response times were 1 min or less; stability of response and electrode lifetime in continuous use was also very satisfactory.     

The effects of Au surface diffusion to formation of Au droplets/clusters and nanowire growth on GaAs substrate using VLS method

Using VLS method with the separated 220 nm thick Au catalyst circles/stripes configurations sputtered onto GaAs substrate surface, this paper investigated the effects of the Au droplets/clusters formation as well as the nanowires growth process inside and outside the Au circles/stripes configurations. The Au surface outward diffusion from the Au layer edge up to several tens of micrometers has strongly dominated. The effects of Au surface diffusion to formation of Au droplets/cluster and to the nanowires growth on GaAs semiconductor substrate in the region outside the Au layers have been shown. The mechanism of the droplets/clusters formation outside the Au layer could explained by the surface cluster diffusion, meanwhile the nanowires have grown simultaneously during the Au outward diffusion. The growth could explain by the diffusion of Ga and As atoms into the diffusing Au droplets/clusters via dissociative mechanism to form nanowire seeds inside for nanowires growth. The Au droplets/clusters formation and nanowires growth on GaAs substrate outside Au layer could be applied for making nanodevices blocks outside the Au layer. Unfortunately if this Au surface diffusion phenomenon is occurring on the GaAs semiconductor containing the Au stripes interconnections in micro/nanocircuits this could also cause the short-circuits phenomenon, even at thin Au layer.     

Chip-based on-line nanospray MS method enabling study of the kinetics of isocyanate derivatization reactions

The reaction of propyl isocyanate (2), benzyl isocyanate (3), and toluene-2,4-diisocyanate (4) with 4-nitro-7-piperazino-2,1,3-benzoxadiazole (1) to yield the corresponding urea derivatives 5 was carried out in a continuous flow glass microfluidics chip. Real-time monitoring of the derivatization reactions was done by electrospray ionization mass spectrometry, making use of a recently reported modular chip-MS interface. Rate constants of 1.5 x 10(4), 5.2 x 10(4), and 2.4 x 10(4) M(-1) min(-1) were determined for 2, 3, and 4, respectively. Using macroscale batch conditions, the rate constants are 3-4 times lower. The faster on-chip kinetics is attributed to the more efficient molecular diffusion in the micrometer-sized channel.     

Chronoamperometry at micropipet electrodes for determination of diffusion coefficients and transferred charges at liquid/liquid interfaces

Chronoamperometry was carried out at liquid/liquid interfaces supported at the tip of micropipet electrodes for direct determination of the diffusion coefficient of a species in the outer solution. The diffusion coefficient was used for subsequent determination of the transferred charges per species from the diffusion-limited steady-state current. A large tip resistance of the micropipets causes prolonged charging current so that the faradic current can be measured accurately only at a long-time regime (typically t > 5 ms). At the same time, the long-time current response at the interfaces surrounded by a thin glass wall of the pipets is enhanced by diffusion of the species from behind the pipet tip. Therefore, numerical simulations of the long-time chronoamperometric response were carried out using the finite element method for accurate determination of diffusion coefficients. Validity of the simulation results was confirmed by studying simple transfer of tetraethylammonium ion. The technique was applied for transfer/adsorption reactions of the natural polypeptide protamine and also for Ca2+ and Mg2+ transfers facilitated by ionophore ETH 129. With the diffusion coefficient of protamine determined to be (1.2 +/- 0.1) x 10(-6) cm(2)/s, the ionic charge transferred by each protamine molecule was obtained as +20 +/- 1, which is close to the excess positive charge of protamine. Also, the diffusion coefficient of ETH 129 was determined to demonstrate that each ionophore molecule transfers +0.67 and +1 charge per Ca2+ and Mg2+ transfer, respectively, which corresponds to formation of 1:3 and 1:2 complexes with the respective ions.