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1

Micro-ring resonators silicon-based modulator performance improvement  

NASA Astrophysics Data System (ADS)

Silicon-based electro-optic modulator is a key device that used to implement optical interconnections. The paper is attempt to analyze the Silicon-on-insulator (SOI ) structure characteristics of resonator, according to the transfer function. The spectra response of Single Micro-Ring (SMR) and Double Micro-Ring resonators (DMR) with a ridge cross section on silicon was discussed emphatically. The 3dB bandwidth and the coupling coefficient affection on it were calculated and compared. The relationship between the characteristics of resonators the coupling coefficient was analyzed. The commercial software Rsoft was used to simulate the figures of SMR and DMR respectively. The simulation results show that the 3dB bandwidth of DMR can be achieved much narrower than that of SMR through the optimization design of the structural parameters. And the filter response line is sheerer for the DMR.

Zhang, Yan; Xi, Gang; Hu, Ting; Zhang, Wen Qian

2010-11-01

2

Large refractive index change in silicone-based and non-silicone-based hydrogel polymers induced by femtosecond laser micro-machining  

Microsoft Academic Search

A Ti:Sapphire femtosecond laser with a pulse energy of 1.3 nJ at a 93 MHz repetition rate has been used to micro-machine optical gratings inside several silicone-based and non-silicone-based hydrogel polymers. By measuring the diffraction efficiency of the gratings at 632.8 nm, we find as large as 0.06± 0.005 average refractive index change within the irradiated area.

Li Ding; Richard Blackwell; Jay F. Kunzler; Wayne H. Knox

2006-01-01

3

Silicon-based bridge wire micro-chip initiators for bismuth oxide-aluminum nanothermite  

NASA Astrophysics Data System (ADS)

We present a micro-manufacturing process for fabricating silicon-based bridge wire micro-chip initiators with the capacity to liberate joules of chemical energy at the expense of micro joules of input electrical energy. The micro-chip initiators are assembled with an open material reservoir utilizing a novel 47 °C melting point solder alloy bonding procedure and integrated with a bismuth oxide-aluminum nanothermite energetic composite. The electro-thermal conversion efficiency of the initiators is enhanced by the use of a nanoporous silicon bed which impedes thermal coupling between the bridge wire and bulk silicon substrate while maintaining the structural integrity of the device. Electrical behaviors of the ignition elements are investigated to extract minimum input power and energy requirements of 382.4 mW and 26.51 µJ, respectively, both in the absence and presence of an injected bismuth oxide-aluminum nanothermite composition. Programmed combustion of bismuth oxide-aluminum nanothermite housed within these initiators is demonstrated with a success rate of 100% over a 30 to 80 µJ range of firing energies and ignition response times of less than 2 µs are achieved in the high input power operation regime. The micro-initiators reported here are intended for use in miniaturized actuation technologies.

Staley, C. S.; Morris, C. J.; Thiruvengadathan, R.; Apperson, S. J.; Gangopadhyay, K.; Gangopadhyay, S.

2011-11-01

4

Porous Silicon-Based Gas Sensors and Miniature Hydrogen Cells  

NASA Astrophysics Data System (ADS)

The current-voltage (I-V) characteristics of Au/porous silicon (PS)/Si Schottky-type structures in humid, CO, and H2S gas atmospheres were investigated. It was found that the gas atmosphere influences the I-V characteristics, particularly the reverse current in Au/PS/Si and Au/PS structures. The reverse current in the H2S atmosphere was 103 times larger than that in room-temperature (300 K) air [45% relative humidity (RH)]. The generation of an open-circuit voltage (up to 480 mV) at the Au/PS interface in humid, CO, and H2S atmospheres was detected. The humidity- and gas-stimulated effect of voltage generation in the Au/PS/Si structures was reversible with a response time of 60 s. The quite high sensitivities to humidity, CO, and H2S (about 9 mV/RH, 4 mV/ppm, and 2 mV/ppm, respectively) indicate the possibility of using the obtained Au/PS/Si structures as both gas sensors and miniature hydrogen fuel cells. The mechanism for the gas-stimulated generation of electricity in the Au/PS structures is discussed and is considered to be similar to that of the proton exchange membrane in hydrogen fuel cells.

Dzhafarov, Tayyar; Yuksel, Sureyya Aydin; Lus, Cigdem Oruc

2008-10-01

5

Hybrid polymer electrolyte membrane for silicon-based micro fuel cells integration  

Microsoft Academic Search

A novel approach for a hybrid polymer electrolyte membrane compatible with silicon-based fuel cells is proposed in this study. The membrane consists of a polymer matrix of polydimethylsiloxane (PDMS) filled with a proton-conducting polymer. The fabrication steps of the hybrid membrane as well as its electrochemical characterization are explained in detail. The obtained proton conductivities demonstrate the validity of the

J. P. Esquivel; N. Sabaté; A. Tarancón; N. Torres-Herrero; D. Dávila; J. Santander; I. Gràcia; C. Cané

2009-01-01

6

Porous silicon based orientation independent, self-priming micro direct ethanol fuel cell  

Microsoft Academic Search

The design, fabrication and testing of an orientation independent, self-priming micro direct ethanol fuel cell (DEFC) is presented. The electrodes of the fuel cell are fabricated using macro-porous silicon technology. The capillary force generated by the pores has the ability of “wicking” the fuel towards the electrode irrespective of the orientation of the cell, resulting in a uniform and regulated

Shyam Aravamudhan; Abdur Rub Abdur Rahman; Shekhar Bhansali

2005-01-01

7

An on-chip micro-friction tester for tribology research of silicon based MEMS devices  

Microsoft Academic Search

An on-chip micro-tribotester has been developed to investigate the friction and wear properties on side contacting surfaces\\u000a of single crystal silicon that is most widely used in usual microelectromechanical systems actuators. The device is fabricated\\u000a with standard bulk silicon process and bonding technology based on parameters that have been theoretically calculated to get\\u000a the stiffness and friction forces. In this

Zhanshe Guo; Yonggang Meng; Caijun Su; Hao Wu

2008-01-01

8

Micro-Raman spectroscopy of refractive index microstructures in silicone-based hydrogel polymers created by high-repetition-rate femtosecond laser micromachining  

Microsoft Academic Search

Micro-Raman spectroscopy was used to study silicone-based hydrogel polymers after being modified by 800 nm, 27 fs laser pulses from a Ti:sapphire oscillator at 93 MHz repetition rate. When the irradiation con- ditions were below the optical breakdown threshold of the polymers, no significant changes in the Raman spec- tra and background fluorescence were observed even when refractive index changes

Li Ding; Luiz Gustavo Cancado; Lukas Novotny; Wayne H. Knox; Neil Anderson; Dharmendra Jani; Jeffrey Linhardt; Richard I. Blackwell; Jay F. Künzler

2009-01-01

9

Aluminum-anode, silicon-based micro-cells for powering expendable MEMS and lab-on-a-chip devices  

Microsoft Academic Search

On-demand powering via micro-fluidic actuation of electrolyte in voltaic cells has been introduced as an alternative to power disposable MEMS-based sensor systems. Aluminum-anode cells activated with alkaline-hydrogen peroxide electrolyte mixtures are studied with the aim of achieving high energetic densities relative to the cells’ minute dimensions. Cells with two configurations are fabricated and their performance is investigated here. The cells

A. M. Cardenas-Valencia; J. Dlutowski; S. Knighton; C. J. Biver; J. Bumgarner; L. Langebrake

2007-01-01

10

Integration of a silicon-based microprobe into a gear measuring instrument for accurate measurement of micro gears  

NASA Astrophysics Data System (ADS)

The integration of silicon micro probing systems into conventional gear measuring instruments (GMIs) allows fully automated measurements of external involute micro spur gears of normal modules smaller than 1 mm. This system, based on a silicon microprobe, has been developed and manufactured at the Institute for Microtechnology of the Technische Universität Braunschweig. The microprobe consists of a silicon sensor element and a stylus which is oriented perpendicularly to the sensor. The sensor is fabricated by means of silicon bulk micromachining. Its small dimensions of 6.5 mm × 6.5 mm allow compact mounting in a cartridge to facilitate the integration into a GMI. In this way, tactile measurements of 3D microstructures can be realized. To enable three-dimensional measurements with marginal forces, four Wheatstone bridges are built with diffused piezoresistors on the membrane of the sensor. On the reverse of the membrane, the stylus is glued perpendicularly to the sensor on a boss to transmit the probing forces to the sensor element during measurements. Sphere diameters smaller than 300 µm and shaft lengths of 5 mm as well as measurement forces from 10 µN enable the measurements of 3D microstructures. Such micro probing systems can be integrated into universal coordinate measuring machines and also into GMIs to extend their field of application. Practical measurements were carried out at the Physikalisch-Technische Bundesanstalt by qualifying the microprobes on a calibrated reference sphere to determine their sensitivity and their physical dimensions in volume. Following that, profile and helix measurements were carried out on a gear measurement standard with a module of 1 mm. The comparison of the measurements shows good agreement between the measurement values and the calibrated values. This result is a promising basis for the realization of smaller probe diameters for the tactile measurement of micro gears with smaller modules.

Ferreira, N.; Krah, T.; Jeong, D. C.; Metz, D.; Kniel, K.; Dietzel, A.; Büttgenbach, S.; Härtig, F.

2014-06-01

11

Monolithically-integrated MicroChemLab for gas-phase chemical analysis.  

SciTech Connect

Sandia National Labs has developed an autonomous, hand-held system for sensitive/selective detection of gas-phase chemicals. Through the sequential connection of microfabricated preconcentrators (PC), gas chromatography columns (GC) and a surface acoustic wave (SAW) detector arrays, the MicroChemLab{trademark} system is capable of selective and sensitive chemical detection in real-world environments. To date, interconnection of these key components has primarily been achieved in a hybrid fashion on a circuit board modified to include fluidic connections. The monolithic integration of the PC and GC with a silicon-based acoustic detector is the subject of this work.

Kottenstette, Richard Joseph; Adkins, Douglas Ray; Manley, Robert George; Lewis, Patrick Raymond; Bauer, Joseph M.; Manginell, Ronald Paul; Okandan, Murat; Shul, Randy John; Sokolowski, Sara Suzette

2003-06-01

12

Environmental Barrier Coatings for Silicon-Based Ceramics.  

National Technical Information Service (NTIS)

Silicon-based ceramics, such as SiC fiber-reinforced SiC (SiC/SiC ceramic matrix composites (CMC) and monolithic silicon nitride (Si3N4), are prime candidates for hot section structural components of next generation gas turbine engines. Silicon-based cera...

K. N. Lee D. S. Fox R. C. Robinson N. P. Bansal

2001-01-01

13

Silicon based plasmonic coupler.  

PubMed

Plasmonics is a field in which the light matter interaction can be controlled at the nanoscale by patterning the material surface to achieve enhanced optical effects. Realisation of micron sized silicon based plasmonic devices will require efficient coupling of light from an optical fibre grating coupler into silicon compatible plasmonic waveguides. In this paper we have investigated a silicon based plasmonic coupler with a very short taper length, which confines and focuses light from a broad input fibre opening into a plasmonic waveguide at the apex of the structure. A simple transfer matrix model was also developed to analyse the transmission performance of the coupler with respect to its key physical parameters. The proposed plasmonic coupler was optimised with respect to its different structural parameters using finite element simulations. A maximum coupling efficiency of 72% for light coupling from a 6.2 ?m wide input opening into a 20 nm slit width was predicted. The simulated result also predicted an insertion loss of ? 2.0 dB for light coupling into a 300 nm single mode SOI waveguide from a plasmonic structure with a 10.4 ?m input opening width and a taper length of only 3.15 ?m. Furthermore, the application of the optimised plasmonic coupler as a splitter was investigated, in which the structure simultaneously splits and couples light with a predicted coupling efficiency of ? 37 % (or a total coupling efficiency of 73%) from a 6.22 ?m input opening into two 50 nm wide plasmonic waveguides. PMID:23037272

Thomas, Roney; Ikonic, Zoran; Kelsall, R W

2012-09-10

14

Capacitive blade tip clearance measurements for a micro gas turbine  

Microsoft Academic Search

The efficiency of a gas turbine has an inverse relationship with the clearance between the rotor blades and the casing. Recent efforts in miniaturization of micro gas turbine engines have created new challenge in tip clearance measurement. This paper describes the development of a tip clearance measurement system, based on capacitive measurement for a palm-top micro gas turbine engine. The

Tibor Fabian; Sangkyun Kang; F. Prinz

2002-01-01

15

Silicon-based nanoenergetic composites  

SciTech Connect

Fundamental combustion properties of silicon-based nano-energetic composites was studied by performing equilibrium calculations, 'flame tests', and instrumented burn-tube tests. That the nominal maximum flame temperature and for many Si-oxidizer systems is about 3000 K, with exceptions. Some of these exceptions are Si-metal oxides with temperatures ranging from 2282 to 2978 K. Theoretical maximum gas production of the Si composites ranged from 350-6500 cm{sup 3}/g of reactant with NH{sub 4}ClO{sub 4} - Si producing the most gas at 6500 cm{sup 3}/g and Fe{sub 2}O{sub 3} producing the least. Of the composites tested NH{sub 4}ClO{sub 4} - Si showed the fastest burning rates with the fastest at 2.1 km/s. The Si metal oxide burning rates where on the order of 0.03-75 mls the slowest of which was nFe{sub 2}O{sub 3} - Si.

Asay, Blaine [Los Alamos National Laboratory; Son, Steven [PURDUE UNIV; Mason, Aaron [PURDUE UNIV; Yarrington, Cole [PURDUE UNIV; Cho, K Y [PURDUE UNIV; Gesner, J [PSU; Yetter, R A [PSU

2009-01-01

16

1st European Conference on Gas Micro Flows (GasMems 2012)  

Microsoft Academic Search

The aim of the 1st European Conference on Gas Micro Flows is to advance research in Europe and worldwide in the field of gas micro flows as well as to improve global fundamental knowledge and to enable technological applications. Gas flows in microsystems are of great importance and touch almost every industrial field (e.g. fluidic microactuators for active control of

Arjan Frijns; Dimitris Valougeorgis; Stéphane Colin; Lucien Baldas

2012-01-01

17

ANN Modeling of Micro-Machined Gas Sensor Signals  

Microsoft Academic Search

In this paper, an integrated micro-machined gas sensor array, associated with pattern recognition (PARC) techniques, such as artificial neural networks (ANNs), is designed. The proposed sensor design use a number of different sensitive films such as SnO2, TiO2, ZnO, or organic sensitive films to detect different gases. The application of micro-machined Si-based gas sensors in air quality management and emission

Mohamed Gamal El-din; Walied A. Moussa

2005-01-01

18

Recent advancements in the gas-phase MicroChemLab  

NASA Astrophysics Data System (ADS)

Sandia's hand-held MicroChemLabTM system uses a micromachined preconcentrator (PC), a gas chromatography channel (GC) and a quartz surface acoustic wave array (SAW) detector for sensitive/selective detection of gas-phase chemical analytes. Requisite system size, performance, power budget and time response mandate microfabrication of the key analytical system components. In the fielded system hybrid integration has been employed, permitting optimization of the individual components. Recent improvements in the hybrid-integrated system, using plastic, metal or silicon/glass manifolds, is described, as is system performance against semivolatile compounds and toxic industrial chemicals. The design and performance of a new three-dimensional micropreconcentrator is also introduced. To further reduce system dead volume, eliminate unheated transfer lines and simplify assembly, there is an effort to monolithically integrate the silicon PC and GC with a suitable silicon-based detector, such as a magnetically-actuated flexural plate wave sensor (magFPW) or a magnetically-actuated pivot plate resonator (PPR).

Manginell, Ronald P.; Lewis, Patrick R.; Adkins, Douglas R.; Kottenstette, Richard J.; Wheeler, David; Sokolowski, Sara; Trudell, Dan; Byrnes, Joy; Okandan, Murat; Bauer, Joseph M.; Manley, Robert G.

2004-12-01

19

Microfabricated silicon gas chromatographic micro-channels: fabrication and performance  

SciTech Connect

Using both wet and plasma etching, we have fabricated micro-channels in silicon substrates suitable for use as gas chromatography (GC) columns. Micro-channel dimensions range from 10 to 80 {micro}m wide, 200 to 400 {micro}m deep, and 10 cm to 100 cm long. Micro-channels 100 cm long take up as little as 1 cm{sup 2} on the substrate when fabricated with a high aspect ratio silicon etch (HARSE) process. Channels are sealed by anodically bonding Pyrex lids to the Si substrates. We have studied micro-channel flow characteristics to establish model parameters for system optimization. We have also coated these micro-channels with stationary phases and demonstrated GC separations. We believe separation performance can be improved by increasing stationary phase coating uniformity through micro-channel surface treatment prior to stationary phase deposition. To this end, we have developed microfabrication techniques to etch through silicon wafers using the HARSE process. Etching completely through the Si substrate facilitates the treatment and characterization of the micro- channel sidewalls, which domminate the GC physico-chemical interaction. With this approach, we separately treat the Pyrex lid surfaces that form the top and bottom surfaces of the GC flow channel.

Matzke, C.M.; Kottenstette, R.J.; Casalnuovo, S.A.; Frye-Mason, G.C.; Hudson, M.L.; Sasaki, D.Y.; Manginell, R.P.; Wong, C.C.

1998-11-01

20

Information preservation methods for modeling micro-scale gas flows  

NASA Astrophysics Data System (ADS)

Micro-scale gas flow is a rapidly growing research field driven by microsystems technology. Experiments have shown that fluid mechanics of these flows are not the same as those experienced in the macroscopic world. However, theoretical analysis is difficult because those flows are generally in the slip or transitional flow regime, and it is hard to investigate the detailed flow fields experimentally due to the small physical dimensions of microsystems. There are several numerical approaches that can model some micro-scale gas flows. Generally, continuum-based methods are numerically efficient, but physically limited; kinetic-based methods are physically accurate, but numerically expensive. Hence, it is necessary to develop a general-purpose numerical approach to understand micro-scale gas flows. This dissertation is devoted to developing a numerical approach for modeling general micro-scale gas flows with reasonable efficiency and accuracy. In the first stage, a particle method called the information preservation (IP) method, proposed by Fan and Shen based on the direct simulation Monte Carlo (DSMC) method, is developed to simulate general micro-scale gas flows. The IP method greatly reduces the statistical scatter associated with particle methods by using macroscopic information preserved in microscopic particles to sample the flow field. Thus low-speed micro-scale gas flows can be simulated using the IP method with reasonable numerical cost. In the second stage, a hybrid approach is designed by coupling the IP method and a Navier-Stokes solver for modeling micro-scale gas flows with better numerical efficiency. The IP method and the Navier-Stokes solver are strongly coupled using an adaptive continuum/particle interface. Using the hybrid approach, we investigate gas flows over micro-scale flat plates. We find that the normalized drag coefficient CDM on a flat plate having zero thickness depends on Re/M0.8 when 1micro air vehicles.

Sun, Quanhua

21

Improved micro-flame detection method for gas chromatography  

Microsoft Academic Search

A previously developed micro-counter-current flame method is modified to provide both sensitive photometric and ionization detection for gas chromatography (GC). A stainless steel capillary (0.254mm i.d.) supplying oxygen functions as a burner, which supports a compact flame that burns in a counter-flowing excess of hydrogen. In the “micro-flame photometric detector” (?FPD) response mode, the background emission level is reduced by

Kevin B Thurbide; Taylor C Hayward

2004-01-01

22

Micro-structured reactors for gas phase reactions  

Microsoft Academic Search

This paper deals with reviewing on the application of micro-structured reactors for heterogeneously catalysed gas phase reactions. After a brief introduction covering some estimation criteria for the performance of micro-structured reactors, an overview of the work performed to date in the field is given. The reactors are classified by the type of catalyst applied (porous or non-porous) and according to

Gunther Kolb; Volker Hessel

2004-01-01

23

Gas detection with micro- and nano-engineered optical fibers  

NASA Astrophysics Data System (ADS)

This paper overviews recent development in gas detection with micro- and nano-engineered optical fibers, including hollow-core fibers, suspended-core fibers, tapered optical micro/nano fibers, and fiber-tip micro-cavities. Both direct absorption and photoacoustic spectroscopy based detection schemes are discussed. Emphasis is placed on post-processing stock optical fibers to achieve better system performance. Our recent demonstration of distributed methane detection with a ˜75-m long of hollow-core photonic bandgap fiber is also reported.

Jin, W.; Ho, H. L.; Cao, Y. C.; Ju, J.; Qi, L. F.

2013-12-01

24

Measuring micro-organism gas production  

NASA Technical Reports Server (NTRS)

Transducer, which senses pressure buildup, is easy to assemble and use, and rate of gas produced can be measured automatically and accurately. Method can be used in research, in clinical laboratories, and for environmental pollution studies because of its ability to detect and quantify rapidly the number of gas-producing microorganisms in water, beverages, and clinical samples.

Wilkins, J. R.; Pearson, A. O.; Mills, S. M.

1973-01-01

25

Micro-electro-mechanical systems (MEMS)-based micro-scale direct methanol fuel cell development  

Microsoft Academic Search

This paper describes a high-power density, silicon-based micro-scale direct methanol fuel cell (DMFC), under development at Carnegie Mellon. Major issues in the DMFC design include the water management and energy-efficient micro fluidic sub-systems. The air flow and the methanol circulation are both at a natural draft, while a passive liquid–gas separator removes CO2 from the methanol chamber. An effective approach

Shi-Chune Yao; Xudong Tang; Cheng-Chieh Hsieh; Yousef Alyousef; Michael Vladimer; Gary K. Fedder; Cristina H. Amon

2006-01-01

26

Microfabricated integrated sampler-injector (MISI) for micro gas chromatography  

Microsoft Academic Search

We present the design, fabrication, and preliminary performance testing of a microfabricated integrated sampler- injector (MISI) intended for use in a micro gas chromatography (?GC) system for the analysis of volatile organic compounds (VOCs). The MISI comprises a DRIE Si cavity with an integrated heater and temperature sensor that is packed with a graphitized carbon adsorbent and capped with a

Jung Hwan Seo; Sun Kyu Kim; Edward T. Zellers; Katsuo Kurabayashi

2011-01-01

27

A micro gas chromatography column with a micro thermal conductivity detector for volatile organic compound analysis  

NASA Astrophysics Data System (ADS)

In this paper, a micro gas chromatography (?GC) system contained a ?GC column and a micro thermal conductivity detector (?TCD) was proposed. In order to reduce the volume of the system, some micro heaters were integrated on the surface and backside of the GC column, which could provide a robust temperature programming capability and rapidly increase the temperature of the ?GC column. In addition, a silicon-glass ?TCD with four-thermistor thermal conductivity cells that can offer significant advantages over previously reported designs including low dead volume, good thermal isolation, and elimination of the thermal noise was proposed in this paper. Experimental results have indicated that the ?GC system with a detection limit of several ppm concentration levels separated and detected the benzene, toluene, and styrene in less than 3 min, and the ?GC system also exhibited a good linear response in the test range.

Sun, J. H.; Cui, D. F.; Chen, X.; Zhang, L. L.; Cai, H. Y.; Li, H.

2013-02-01

28

Silicon based microactuators for telerobotic tactile stimulation  

NASA Astrophysics Data System (ADS)

Silicon based microelectromechanical (MEM) devices using both surface and bulk micromachining have been realized to provide tactile stimulation. The bulk MEM devices utilize the bimorph principle and are fabricated in a complementary metal oxide semiconductor (CMOS) process through MOS implementation system (MOSIS). The surface MEM devices utilize the electrostatic principle and are fabricated in the multi-user MEM process (MUMPS) through MCNC. Eleven major designs are presented and tested to determine if they are suitable to provide tactile stimulation. The bimorph and electrostatic designs were tested using a probe station, a laser interferometer, and a force tester. Measurements were taken on the deflections, cutoff frequencies, and loaded operation of the devices. The bimorph designs fabricated in the CMOS process showed the most potential. The tests results indicate that the cantilever beam designs deflect over 30 microns. They operate at frequencies below 130 Hz. The devices operate under a load of approximately 5 microN. An endurance test was performed by actuating a device over 2.5 million times.

Read, Britton C., III

1994-12-01

29

Development of high-speed micro-gas bearings for three-dimensional micro-turbo machines  

Microsoft Academic Search

A micro-high-speed bearing test rig has been designed and fabricated to develop air bearings for a micro-machine gas turbine. The micro-machine gas turbine requires bearings of diameter 4 mm to operate stably at 870 000 rpm. Based on the preliminary analysis, it has been found that a large bearing gap and very high rotor balance are required to achieve low

Kousuke Isomura; Shuji Tanaka; Shin-ichi Togo; Masayoshi Esashi

2005-01-01

30

Fused silica capillary micro-packed columns in gas chromatography  

Microsoft Academic Search

Summary  Flexibility, strength and adsorption inertness of fused-silica capillaries permits their extensive application for the preparation\\u000a of micro-packed columns in gas chromatography. Decreasing the column diameter (from 0.5 to 0.15 mm) and the diameter of the\\u000a sorbent particles (from 100 to 5 ?m) results in a marked reduction of the height equivalent to a theoretical plate (HETP),\\u000a as well as in

A. Malik; V. G. Berezkin; V. S. Gavrichev

1984-01-01

31

PREFACE: 1st European Conference on Gas Micro Flows (GasMems 2012)  

NASA Astrophysics Data System (ADS)

The aim of the 1st European Conference on Gas Micro Flows is to advance research in Europe and worldwide in the field of gas micro flows as well as to improve global fundamental knowledge and to enable technological applications. Gas flows in microsystems are of great importance and touch almost every industrial field (e.g. fluidic microactuators for active control of aerodynamic flows, vacuum generators for extracting biological samples, mass flow and temperature micro-sensors, pressure gauges, micro heat-exchangers for the cooling of electronic components or for chemical applications, and micro gas analyzers or separators). The main characteristic of gas microflows is their rarefaction, which for device design often requires modelling and simulation both by continuous and molecular approaches. In such flows various non-equilibrium transport phenomena appear, while the role played by the interaction between the gas and the solid device surfaces becomes essential. The proposed models of boundary conditions often need an empirical adjustment strongly dependent on the micro manufacturing technique. The 1st European Conference on Gas Micro Flows is organized under the umbrella of the recently established GASMEMS network (www.gasmems.eu/) consisting of 13 participants and six associate members. The main objectives of the network are to structure research and train researchers in the fields of micro gas dynamics, measurement techniques for gaseous flows in micro experimental setups, microstructure design and micro manufacturing with applications in lab and industry. The conference takes place on June 6-8 2012, at the Skiathos Palace Hotel, on the beautiful island of Skiathos, Greece. The conference has received funding from the European Community's Seventh Framework Programme FP7/2007-2013 under grant agreement ITN GASMEMS no. 215504. It owes its success to many people. We would like to acknowledge the support of all members of the Scientific Committee and of all referees for their thorough reviews and evaluation of the full papers. Above all, we would like to sincerely thank all authors for their valuable contributions to these proceedings as well as all the participants for creating a stimulating atmosphere through their presentations and discussions and making this conference a great success. Dr Arjan Frijns Editor and Event Coordinator Prof. Dimitris Valougeorgis Local Organizer Prof. Stéphane Colin Network Coordinator Dr Lucien Baldas Assistant Network Coordinator The PDF also contains details of the Conference Organizers.

Frijns, Arjan; Valougeorgis, Dimitris; Colin, Stéphane; Baldas, Lucien

2012-05-01

32

Heat loss reduction and hydrocarbon combustion in ultra-micro combustors for ultra-micro gas turbines  

Microsoft Academic Search

For the development of ultra-micro combustors for Ultra-Micro Gas Turbines (UMGT), heat loss reduction and hydrocarbon fuel use are the key issues. An approach for reducing the effect of heat loss in ultra-micro combustors was proposed. The heat loss ratio (HLR), which was defined as the ratio of heat loss rate from a combustor to heat release rate in the

Takashi Sakurai; Saburo Yuasa; Taku Honda; Shoko Shimotori

2009-01-01

33

A gas bubble-based parallel micro manipulator: conceptual design and kinematics model  

NASA Astrophysics Data System (ADS)

The parallel mechanism has become an alternative solution when micro manipulators are demanded in the fields of micro manipulation and micro assembly. In this technical note, a three-degree-of-freedom (3-DOF) parallel micro manipulator is presented, which is directly driven by three micro gas bubbles. Since the micro gas bubbles are generated and maintained due to the surface tension between the gas and liquid media, the proposed novel system can be used in the liquid environment which allows for rotation about the X and Y axes and translation along the Z axis. In this technical note, the conceptual design of micro gas bubble-based parallel manipulator is introduced and the input/output characteristic of the actuator is analyzed in detail. The kinematics model of the parallel micro manipulator is also established, based on which the workspace and the system motion resolution are analyzed as a criterion and reference for future prototype development.

Dong, Wei; Gauthier, Michaël; Lenders, Cyrille; Lambert, Pierre

2012-05-01

34

Study on the micro-heater geometry in In,2O3 micro electro mechanical systems gas sensor platforms and effects on NO2 gas detecting performances.  

PubMed

Micro electro mechanical systems (MEMS) platforms for gas sensing devices with the co-planar type micro-heaters were designed, fabricated and its effects on the In2O3 gas sensors were investigated. Micro-heaters in MEMS gas sensor platforms were designed in the four-type heater patterns with different geometries. Electro-thermal characterizations showed that the designed platforms had highly thermal efficiency because the micro hot-plate structures were formed in the diaphragm and the thermal efficiencies were analyzed for all of 16 models and compared with each other, respectively. The designed micro-platforms were fabricated by MEMS process, and Indium oxide (In2O3) nanoparticles were synthesized by sol-gel process and dropped on the MEMS platforms for detecting the noxious oxide gas (NO2) Fabricated micro-platforms had a very low power consumption in the fabricated 16-type models, especially, the minimum power consumption was 41 mW at the operating temperature of 250 degrees C. After experiments on gas sensing characteristics to NO2 gases, fabricated In2O3 gas sensors had almost the same gas sensitivity (Rs) at the operation temperature of 250 degrees C. It is concluded that the micro-heater geometries, pattern shapes and sizes, can be influential on the power consumption of the devices and its gas sensing characteristics. PMID:22629914

Choi, Woo-Seok; Kim, Bum-Joon; Lee, Hoi-Jung; Choi, Jung-Woon; Kim, Si-Dong; Min, Nam-Ki

2012-02-01

35

Integrated Micro-Machined Hydrogen Gas Sensor. Final Report  

SciTech Connect

This report details our recent progress in developing novel MEMS (Micro-Electro-Mechanical Systems) based hydrogen gas sensors. These sensors couple novel thin films as the active layer on a device structure known as a Micro-HotPlate. This coupling has resulted in a gas sensor that has several unique advantages in terms of speed, sensitivity, stability and amenability to large scale manufacture. This Phase-I research effort was focused on achieving the following three objectives: (1) Investigation of sensor fabrication parameters and their effects on sensor performance. (2) Hydrogen response testing of these sensors in wet/dry and oxygen-containing/oxygen-deficient atmospheres. (3) Investigation of the long-term stability of these thin film materials and identification of limiting factors. We have made substantial progress toward achieving each of these objectives, and highlights of our phase I results include the demonstration of signal responses with and without oxygen present, as well as in air with a high level of humidity. We have measured response times of <0.5 s to 1% H{sub 2} in air, and shown the ability to detect concentrations of <200 ppm. These results are extremely encouraging and suggest that this technology has substantial potential for meeting the needs of a hydrogen based economy. These achievements demonstrate the feasibility of using micro-hotplates structures in conjunction with palladium+coated metal-hydride films for sensing hydrogen in many of the environments required by a hydrogen based energy economy. Based on these findings, they propose to continue and expand the development of this technology in Phase II.

Frank DiMeo, Jr.

2000-10-02

36

Development of a micro gas chromatograph for the analysis of hydrogen isotope gas mixtures in the fusion fuel cycle  

Microsoft Academic Search

Analysis of hydrogen isotopes is very important in the fuel cycle system of fusion reactors. Gas chromatography with a cryogenic separation column is one of the most extensively used methods for the analysis of hydrogen isotopes. Micro gas chromatograph (micro GC) with a cryogenic column is expected to improve the analysis time, that is a major disadvantage of conventional GC.

Yoshinori Kawamura; Satoshi Konishi; Masataka Nishi

2001-01-01

37

Development of Micro-Heaters with Optimized Temperature Compensation Design for Gas Sensors  

PubMed Central

One of the key components of a chemical gas sensor is a MEMS micro-heater. Micro-heaters are used in both semiconductor gas sensors and NDIR gas sensors; however they each require different heat dissipation characteristics. For the semiconductor gas sensors, a uniform temperature is required over a wide area of the heater. On the other hand, for the NDIR gas sensor, the micro-heater needs high levels of infrared radiation in order to increase sensitivity. In this study, a novel design of a poly-Si micro-heater is proposed to improve the uniformity of heat dissipation on the heating plate. Temperature uniformity of the micro-heater is achieved by compensating for the variation in power consumption around the perimeter of the heater. With the power compensated design, the uniform heating area is increased by 2.5 times and the average temperature goes up by 40 °C. Therefore, this power compensated micro-heater design is suitable for a semiconductor gas sensor. Meanwhile, the poly-Si micro-heater without compensation shows a higher level of infrared radiation under equal power consumption conditions. This indicates that the micro-heater without compensation is more suitable for a NDIR gas sensor. Furthermore, the micro-heater shows a short response time of less than 20ms, indicating a very high efficiency of pulse driving.

Hwang, Woo-Jin; Shin, Kyu-Sik; Roh, Ji-Hyoung; Lee, Dae-Sung; Choa, Sung-Hoon

2011-01-01

38

Gold Nanoparticle Chemiresistor Arrays for Micro-Gas Chromatography Applications  

NASA Astrophysics Data System (ADS)

Thiolate-monolayer-protected gold nanoparticle (MPN) chemiresistors were studied as the sensing devices for micro-gas chromatography (microGC) systems. Because transport through chemiresistors is dominated by tunneling, they are highly sensitive. In order to improve their limit of detection, their fundamental noise was studied. Chemiresistors exhibit 1/f type noise where noise scales inversely with frequency. Chemiresistor noise was found to scale inversely with MPN film thickness. We lowered the noise prefactor of a 50x60 microm2 chemiresistor by coating a thick rather than monolayer MPN film. Electron beam induced crosslinking (EBIX) of the MPN film slightly reduced chemiresistor noise. A technique for patterning chemiresistor arrays with MPN films using EBIX was developed, and an array with four distinct MPNs was fabricated in an area ˜600 microm 2. This is the smallest chemiresistor array reported to date. Chemiresistors were exposed to vapors and provided differential sensitivities comparable to those from larger uncrosslinked chemiresistors. Chemiresistors were studied to assess their long term stability. Chemiresistors exhibited decreases in resistance over time that is likely caused by loss of MPN ligands. Temperature dependent current-voltage measurements verified the resistance change was not due to changes in the size of the MPN core. While resistance could change by orders of magnitude, vapor sensitivity did not show significant changes. Heating increased the change in resistance, but chemiresistors remained responsive after being held at 80°C for a cumulative 400 hours. It was unknown whether tunneling in the MPN film is through the highest unoccupied molecular orbital (HOMO) or lowest unoccupied molecular orbital (LUMO). A new technique was explored to distinguish tunneling through the HOMO and LUMO by measuring the induced thermoelectric voltage caused by a temperature difference across the MPN film. For integration into a microGC system, we fabricated a chemiresistor array on the surface of a 2.2x2.2 mm2readout circuitry chip creating a monolithic sensor system. A model for determining the optimal sensor size for a microGC system is presented. While noise is inversely proportional to chemiresistor volume, the amount of analyte detectable is proportional to volume making smaller chemiresistors able to detect lesser amounts of analyte.

Covington, Elizabeth Laura

39

Micro Gas Preconcentrator Made of a Film of Single-Walled Carbon Nanotubes  

Microsoft Academic Search

The development of micro gas preconcentrators is crucial for the realization of miniaturized gas chromatography (micro-GC) systems which are expected to open up new applications such as breath analysis. One of the major problems with the reduction in the preconcentrator size by miniaturization is the availability of a sorbent material having high enough concentration factor. Single-walled carbon nanotubes (SWNTs) are

Shuji Takada; Takashi Nakai; Theerapol Thurakitseree; Junichiro Shiomi; Shigeo Maruyama; Hideki Takagi; Masaki Shuzo; Jean-Jacques Delaunay; Ichiro Yamada

2010-01-01

40

Distributed Gas Breather for Micro Direct Methanol Fuel Cell (micrometer-DMFC).  

National Technical Information Service (NTIS)

This paper introduces a distributed gas breather to remove the gas byproduct (CO2) from the micro direct methanol fuel cell (microDMFC). The concept and device configuration of 'distributed breathing' aim to improve the performance of the mDMFC by (1) dec...

C. Kim D. Meng J. Kim

2003-01-01

41

Development of Pressure-Sensitive Channel Chip for Micro Gas Flows  

NASA Astrophysics Data System (ADS)

Optical measurement techniques are useful for experimental studies on micro gas flows, which enable us to non-intrusively measure the flows with a high spatial resolution. The pressure-sensitive paint (PSP) technique, which is based on the emission of photons from luminophore, is a potential diagnostic tool for pressure measurement of micro gas flows. However, measurements by conventional PSPs are limited to the sub-millimeter order spatial resolution of ca. 200 ?m, indicating the difficulty of the micro scale measurements. The present study proposes pressure-sensitive channel chip (PSCC) which is a micro channel with the capability of measuring pressure. We focused on the poly (dimethylsiloxane) (PDMS) micro-molding technique, which is one of the most popular techniques to fabricate a micro channel easily. Moreover, PDMS is a polymer used as a binder in PSP because of high optical transparency, gas permeability, and gas diffusivity. Thus, we developed a micro channel by the PDMS micro-molding technique with mixing a pressure-sensitive luminophore into PDMS: i.e. a micro channel fabricated by PSP, which is named PSCC. A flow through a micro converging-diverging nozzle with the throat width of 120 ?m was demonstrated. The pressure distribution on the nozzle surface was successfully obtained by PSCC.

Matsuda, Yu; Yamaguchi, Hiroki; Niimi, Tomohide

2012-05-01

42

Fabrication of porous silicon-based biosensor  

Microsoft Academic Search

A porous silicon-based biosensor for detection of bacteria was fabricated. Silicon (0.01 ohm-cm, p-type) was anodized electrochemically in a hydrofluoric acid solution containing electrochemical cell using different current and time conditions ranging from 100 mA\\/cm2 for 30 sec to 2 mA\\/cm for 1 hr to produce sponge like porous layer of silicon. Anodizing conditions of 5 mA\\/cm2 for 1 hr

Finny P. Mathew; Evangelyn C. Alocilja

2003-01-01

43

[Importance of silicone bases in complete dentures].  

PubMed

The use of a silicone base under a total prosthesis makes possible the solution of certain problems of tolerance or maintenance of such denture. I.--Full denture in patients who have received radiotherapy. II.--Full denture with intolerant mucosa. III.--Following failure of classical prosthesis. IV--Prosthesis fitted following pre-prosthetic surgery. The technical problems associated with the fabrication of such prosthesis and possible adjustements are discussed. PMID:1058518

Cros, P; Achard, R; Brugirard, J

1975-01-01

44

Micro-miniature gas chromatograph column disposed in silicon wafers  

DOEpatents

A micro-miniature gas chromatograph column is fabricated by forming matching halves of a circular cross-section spiral microcapillary in two silicon wafers and then bonding the two wafers together using visual or physical alignment methods. Heating wires are deposited on the outside surfaces of each wafer in a spiral or serpentine pattern large enough in area to cover the whole microcapillary area inside the joined wafers. The visual alignment method includes etching through an alignment window in one wafer and a precision-matching alignment target in the other wafer. The two wafers are then bonded together using the window and target. The physical alignment methods include etching through vertical alignment holes in both wafers and then using pins or posts through corresponding vertical alignment holes to force precision alignment during bonding. The pins or posts may be withdrawn after curing of the bond. Once the wafers are bonded together, a solid phase of very pure silicone is injected in a solution of very pure chloroform into one end of the microcapillary. The chloroform lowers the viscosity of the silicone enough that a high pressure hypodermic needle with a thumbscrew plunger can force the solution into the whole length of the spiral microcapillary. The chloroform is then evaporated out slowly to leave the silicone behind in a deposit.

Yu, Conrad M. (Antioch, CA)

2000-01-01

45

Micro-miniature gas chromatograph column disposed in silicon wafers  

SciTech Connect

A micro-miniature gas chromatograph column is fabricated by forming matching halves of a circular cross-section spiral microcapillary in two silicon wafers and then bonding the two wafers together using visual or physical alignment methods. Heating wires are deposited on the outside surfaces of each wafer in a spiral or serpentine pattern large enough in area to cover the whole microcapillary area inside the joined wafers. The visual alignment method includes etching through an alignment window in one wafer and a precision-matching alignment target in the other wafer. The two wafers are then bonded together using the window and target. The physical alignment methods include etching through vertical alignment holes in both wafers and then using pins or posts through corresponding vertical alignment holes to force precision alignment during bonding. The pins or posts may be withdrawn after curing of the bond. Once the wafers are bonded together, a solid phase of very pure silicone is injected in a solution of very pure chloroform into one end of the microcapillary. The chloroform lowers the viscosity of the silicone enough that a high pressure hypodermic needle with a thumbscrew plunger can force the solution into the whole length of the spiral microcapillary. The chloroform is then evaporated out slowly to leave the silicone behind in a deposit.

Yu, C.M.

2000-05-30

46

Use of micro gas chromatography in the fuel cycle of fusion reactors  

Microsoft Academic Search

Various analytical techniques exist to determine the compositions of gases handled in the fuel cycle of future fusion machines. Gas chromatography was found to be the most appropriate method. The main disadvantages of conventional gas chromatography were the long retention times for the heavy hydrogen species of >30 min. Recent progress in the development of micro-gas chromatography has reduced these

R. Lässer; S. Grünhagen; Y. Kawamura

2003-01-01

47

The fabrication of all-silicon micro gas chromatography columns using gold diffusion eutectic bonding  

Microsoft Academic Search

Temperature programming of gas chromatography (GC) separation columns accelerates the elution rate of chemical species through the column, increasing the speed of analysis, and hence making it a favorable technique to speedup separations in microfabricated GCs (micro-GC). Temperature-programmed separations would be preferred in an all-silicon micro-column compared to a silicon-Pyrex® micro-column given that the thermal conductivity and diffusivity of silicon

A. D. Radadia; A. Salehi-Khojin; R. I. Masel; M. A. Shannon

2010-01-01

48

Silicon-Based Multiple Microsensors for Sensing Carbon Dioxide, Humidity and Temperature  

Microsoft Academic Search

A silicon based multiple microsensor for sensing carbon dioxide, humidity and temperature has been investigated. The carbon dioxide microsensor was designed based on gas permeable membrane and ion-sensing field effect transistor structures. The humidity microsensor was designed based on metal-oxide -semiconductor transistor with a polyimide sensing film. The temperature microsensor was also designed based on diode -sensing structure. The multiple

Hsing-Cheng Chang

1994-01-01

49

Thermostatted micro gas chromatography column with on-chip thermal conductivity detector for elevated temperature separation  

Microsoft Academic Search

We present the design, fabrication and experimental evaluation of the first thermostatted micro gas chromatography (?GC) column with an integrated micro thermal conductivity detector (?TCD). The chip contains on-chip sensors and heater on the backside to provide robust temperature programming capability. Our unique ?TCD offers many advantages over previously reported designs including low dead volume, elimination of flow restrictors, and

Shree Narayanan; Bassam Alfeeli; Masoud Agah

2010-01-01

50

Numerical study of micro-scale gas flow using finite volume method  

Microsoft Academic Search

Numerical studies of subsonic gas flow through micro-thruster as no-slip benchmark problem and high speed gas flow through short micro-channel with slip and temperature jump correction have been carried out by solving two dimensional compressible Navier-Stokes (NS) system of equations. A 2-D explicit finite volume (FV) flow solver has been developed using modified advection upwind splitting methods (AUSM+) to achieve

A. Chaudhuri; C. Guha; T. K. Dutta

2006-01-01

51

Design and simulations of SOI CMOS micro-hotplate gas sensors  

Microsoft Academic Search

This paper describes a new generation of integrated solid-state gas-sensors embedded in SOI micro-hotplates. The micro-hotplates lie on a SOI membrane and consist of MOSFET heaters that elevate the operating temperature, through self-heating, of a gas sensitive material. These sensors are fully compatible with SOI CMOS or BiCMOS technologies, offer ultra-low power consumption (under 100mW), high sensitivity, low noise, low

F. Udrea; J. W. Gardner; D. Setiadi; J. A. Covington; T. Dogaru; C. C. Lua; W. I. Milne

2001-01-01

52

In2O3-based micro gas sensor for detecting NO x gases  

NASA Astrophysics Data System (ADS)

In this study, NO x micro gas sensors for monitoring the indoor atmosphere of automobile were fabricated using MEMS (microelectromechanical system) technology and a sol-gel process. The sensing electrode and micro heater were designed to have a co-planar typed structure in a Pt thin film layer. The thermal characteristics of a micro heater array were analyzed using a finite element method (FEM). The chip size of the gas sensor was approximately 2 mm × 2 mm. Indium oxide as a sensing material for NO x gas was synthesized by a sol-gel process with indium isopropoxide as a precursor. Field emission Scanning electron microscopy and x-ray diffraction showed that particle size of the synthesized In2O3 was approximately 17-45 nm. The maximum gas sensitivity as the relative resistance ( R s = R gas / R air ) was observed at 275°C with a value of 8.0 at 1 ppm NO2 gas. The response (80% saturation) and recovery times were within 1 min. The sensing properties of NO2 gas exhibited linear behavior with increasing gas concentration. The sensing mechanism of the gas sensor was explained by the variations in the electron depletion layers and the adsorption of gas molecules on the In2O3 particle surface. These results suggest that in the future, MEMS-based gas sensors can be used as automotive-exhaust-gas sensors.

Kim, Bum-Joon; Song, In-Gyu; Kim, Jung-Sik

2014-03-01

53

Recognizing indoor formaldehyde in binary gas mixtures with a micro gas sensor array and a neural network  

NASA Astrophysics Data System (ADS)

Low-concentration formaldehyde (HCHO) together with ethanol/toluene/acetone/?-pinene (as an interference gas of HCHO) is detected with a micro gas sensor array, composed of eight tin oxide (SnO2) thin film gas sensors with Au, Cu, Pt or Pd metal catalysts. The characteristics of the multi-dimensional signals from the eight sensors are evaluated. A multilayer neural network with an error backpropagation (BP) learning algorithm, plus the principal component analysis (PCA) technique, is implemented to recognize these indoor volatile organic compounds (VOC). The results show that the micro gas sensor array, plus the multilayer neural network, is very effective in recognizing 0.06 ppm HCHO in single gas component and in binary gas mixtures, toluene/ethanol/?-pinene with small relative error.

Lv, Pin; Tang, Zhenan; Wei, Guangfen; Yu, Jun; Huang, Zhengxing

2007-09-01

54

Recognizing indoor formaldehyde in binary gas mixtures with a micro gas sensor array and a neural network  

Microsoft Academic Search

Low-concentration formaldehyde (HCHO) together with ethanol\\/toluene\\/acetone\\/alpha-pinene (as an interference gas of HCHO) is detected with a micro gas sensor array, composed of eight tin oxide (SnO2) thin film gas sensors with Au, Cu, Pt or Pd metal catalysts. The characteristics of the multi-dimensional signals from the eight sensors are evaluated. A multilayer neural network with an error backpropagation (BP) learning

Pin Lv; Zhenan Tang; Guangfen Wei; Jun Yu; Zhengxing Huang

2007-01-01

55

Polishing of silicon based advanced ceramics  

NASA Astrophysics Data System (ADS)

Silicon based advanced ceramics show advantages in comparison to other materials due to their extreme hardness, wear and creep resistance, low density and low coefficient of thermal expansion. As a matter of course, machining requires high efforts. In order to reach demanded low roughness for optical or tribological applications a defect free surface is indispensable. In this paper, polishing of silicon nitride and silicon carbide is investigated. The objective is to elaborate scientific understanding of the process interactions. Based on this knowledge, the optimization of removal rate, surface quality and form accuracy can be realized. For this purpose, fundamental investigations of polishing silicon based ceramics are undertaken and evaluated. Former scientific publications discuss removal mechanisms and wear behavior, but the scientific insight is mainly based on investigations in grinding and lapping. The removal mechanisms in polishing are not fully understood due to complexity of interactions. The role of, e.g., process parameters, slurry and abrasives, and their influence on the output parameters is still uncertain. Extensive technological investigations demonstrate the influence of the polishing system and the machining parameters on the stability and the reproducibility. It is shown that the interactions between the advanced ceramics and the polishing systems is of great relevance. Depending on the kind of slurry and polishing agent the material removal mechanisms differ. The observed effects can be explained by dominating mechanical or chemo-mechanical removal mechanisms. Therefore, hypotheses to state adequate explanations are presented and validated by advanced metrology devices, such as SEM, AFM and TEM.

Klocke, Fritz; Dambon, Olaf; Zunke, Richard; Waechter, D.

2009-05-01

56

A micro gas chromatography chip with an embedded non-cascaded thermal conductivity detector  

Microsoft Academic Search

We present the design, fabrication, and testing results of a single chip (2 cm×4 cm) micro gas separation column (?GC) with an embedded non-cascaded micro thermal conductivity detector (?TCD). Our unique design coupled with RIE-Lag enabled 3D etching technology offers several advantages over previously reported designs including simple 2-mask fabrication and operation (no flow restrictors needed), capability for different flow velocities for

Shree Narayanan; Bassam Alfeeli; Masoud Agah

2010-01-01

57

Gas transport by thermal transpiration in micro-channels -- A numerical study  

SciTech Connect

A reliable micro gas pump is an essential element to the development of many micro-systems for chemical gas analyses. At Sandia, the authors are exploring a different pumping mechanism, gas transport by thermal transpiration. Thermal transpiration refers to the rarefied gas dynamics developed in a micro-channel with a longitudinal temperature gradient. To investigate the potential of thermal transpiration for gas pumping in micro-systems, the authors have performed simulations and model analysis to design micro-devices and to assess their design performance before the fabrication process. The effort is to apply ICARUS (a Direct Simulation Monte Carlo code developed at Sandia) to characterize the fluid transport and evaluate the design performance. The design being considered has two plenums at different temperatures (hot and cold) separated by a micro-channel of 0.1 micron wide and 1 micron long. The temperature difference between the two plenums is 30 kelvin. ICARUS results, a quasi-steady analysis, predicts a net flow through the micro-channel with a velocity magnitude of about 0.4 m/s due to temperature gradient at the wall (thermal creep flow) at the early time. Later as the pressure builds up in the hot plenum, flow is reversed. Eventually when the system reaches steady state equilibrium, the net flow becomes zero. The thermal creep effect is compensated by the thermo-molecular pressure effect. This result demonstrates that it is important to include the thermo-molecular pressure effect when designing a pumping mechanism based on thermal transpiration. The DSMC technique can model this complex thermal transpiration problem.

Wong, C.C.; Hudson, M.L.; Potter, D.L.; Bartel, T.J.

1998-08-01

58

Environmental Barrier Coatings for Silicon-Based Ceramics  

NASA Technical Reports Server (NTRS)

Silicon-based ceramics, such as SiC fiber-reinforced SiC (SiC/SiC ceramic matrix composites (CMC) and monolithic silicon nitride (Si3N4), are prime candidates for hot section structural components of next generation gas turbine engines. Silicon-based ceramics, however, suffer from rapid surface recession in combustion environments due to volatilization of the silica scale via reaction with water vapor, a major product of combustion. Therefore, application of silicon-based ceramic components in the hot section of advanced gas turbine engines requires development of a reliable method to protect the ceramic from environmental attack. An external environmental barrier coating (EBC) is considered a logical approach to achieve protection and CP long-term stability. The first generation EBC consisted of two layers, mullite (3Al2O3-2SiO2) bond coat and yttria-stabilized zirconia (YSZ, ZrO2-8 Wt.% Y2O3) top coat. Second generation EBCs, with substantially improved performance compared with the first generation EBC, were developed in the NASA High Speed Research-Enabling Propulsion Materials (HSR-EPM) Program. The first generation EBC consisted of two layers, mullite (3Al2O3-2SiO2) bond coat and yttria-stabilized zirconia (YSZ, ZrO2-8 wt.% Y2O3) top coat. Second generation EBCs, with substantially improved performance compared with the first generation EBC, were developed in the NASA High Speed Research-Enabling Propulsion Materials (HSR-EPM) Program (5). They consist of three layers, a silicon first bond coat, a mullite or a mullite + BSAS (BaO(1-x)-SrO(x)-Al2O3-2SiO2) second bond coat, and a BSAS top coat. The EPM EBCs were applied on SiC/SiC CMC combustor liners in three Solar Turbines (San Diego, CA) Centaur 50s gas turbine engines. The combined operation of the three engines has accumulated over 24,000 hours without failure (approximately 1,250 C maximum combustor liner temperature), with the engine in Texaco, Bakersfield, CA, accumulating about 14,000 hours. As the commercialization of Si-based ceramic components in gas turbines is on the horizon, a major emphasis is placed on EBCs for two reasons. First, they are absolute necessity for the protection of Si-based ceramics from water vapor. Second, they can enable a major enhancement in the performance of gas turbines by creating temperature gradients with the incorporation of a low thermal conductivity layer. Thorough understanding of current state-of-the-art EBCs will provide the foundation upon which development of future EBCs will be based. Phase stability and thermal conductivity of EPM EBCs are published elsewhere. This paper will discuss the chemical/environmental durability and silica volatility of EPM EBCs and their impact on the coating's upper temperature limit.

Lee, Kang N.; Fox, Dennis S.; Robinson, Raymond C.; Bansal, Narottam P.

2001-01-01

59

Fast temperature programmed sensing for micro-hotplate gas sensors  

Microsoft Academic Search

We describe an operating mode of a gas sensor that greatly enhances the capability of the device to determine the composition of a sensed gas. The device consists of a micromachined hotplate with integrated heater, heat distribution plate, electrical contact pads, and sensing film. The temperature programmed sensing (TPS) technique uses millisecond timescale temperature changes to modify the rates for

R. E. Cavicchi; J. S. Suehle; K. G. Kreider; M. Gaitan; P. Chaparala

1995-01-01

60

A Micro Sample Introduction System for Gas Chromatography  

Microsoft Academic Search

AN ideal sample introduction system for gas chromatography suitable for use with a variety of columns and detection devices should possess the following characteristics: (1) the entire sample should be delivered to the inlet of the column as a vapour over a short time-interval to keep dilution of the sample with carrier gas at a minimum; (2) the samples delivered

Robert L. Bowman; Arthur Karmen

1958-01-01

61

The effect of microcolumn geometry on the performance of micro-gas chromatography columns for chip scale gas analyzers  

Microsoft Academic Search

Many microfabricated gas chromatography (micro-GC) column designs have been reported so far, but it is unclear how microcolumn design affects separation performance in the typical isothermal or temperature-programmed mode of operation. This paper compares the separation performance of microfabricated serpentine, circular-spiral and square-spiral columns in both modes of operation. Experimentally although all the geometries have similar gas permeability and unretained

A. D. Radadia; A. Salehi-Khojin; R. I. Masel; M. A. Shannon

2010-01-01

62

Feasibility of pulse combustion in micro gas turbines  

NASA Astrophysics Data System (ADS)

In gas turbines, a fast decrease of efficiency appears when the output decreases; the efficiency of a large gas turbine (20...30 MW) is in the order of 40 %, the efficiency of a 30 kW gas turbine with a recuperator is in the order of 25 %, but the efficiency of a very small gas turbine (2...6 kW) in the order of 4...6 % (or 8...12 % with an optimal recuperator). This is mainly a result of the efficiency decrease in kinetic compressors, due to the Reynolds number effect. Losses in decelerating flow in a flow passage are sensitive to the Reynolds number effects. In contrary to the compression, the efficiency of expansion in turbines is not so sensitive to the Reynolds number; very small turbines are made with rather good efficiency because the flow acceleration stabilizes the boundary layer. This study presents a system where the kinetic compressor of a gas turbine is replaced with a pulse combustor. The combustor is filled with a combustible gas mixture, ignited, and the generated high pressure gas is expanded in the turbine. The process is repeated frequently, thus producing a pulsating flow to the turbine; or almost a uniform flow, if several parallel combustors are used and triggered alternately in a proper way. Almost all the compression work is made by the temperature increase from the combustion. This gas turbine type is investigated theoretically and its combustor also experimentally with the conclusion that in a 2 kW power size, the pulse flow gas turbine is not as attractive as expected due to the big size and weight of parallel combustors and due to the efficiency being in the order of 8 % to 10 %. However, in special applications having a very low power demand, below 1000 W, this solution has better properties when compared to the conventional gas turbine and it could be worth of a more detailed investigation.

Honkatukia, Juha; Saari, Esa; Knuuttila, Timo; Larjola, Jaakko; Backman, Jari

2012-10-01

63

Physical effects in pure continuum-based laminar micro-convection due to variation of gas properties  

Microsoft Academic Search

The governing continuum-based conservation equations for laminar 2D (with axisymmetry) convective micro-tube-flow of gas are numerically solved. These equations comprehensively incorporate the physical effects of variations of gas density with pressure and temperature, and gas viscosity and thermal conductivity with temperature. Their non-dimensionalization reveals the significance of variations in gas properties in convective micro-flows, and the role of the dimensionless

Shripad P Mahulikar; Heinz Herwig

2006-01-01

64

Silicon based microfluidic cell for terahertz frequencies  

NASA Astrophysics Data System (ADS)

We present a detailed analysis of the design, fabrication and testing of a silicon based, microfluidic cell, for transmission terahertz time-domain spectroscopy. The sensitivity of the device is tested through a range of experiments involving primary alcohol/water mixtures. The dielectric properties of these solutions are subsequently extracted using a Nelder-Mead search algorithm, and are in good agreement with literature values obtained via alternative techniques. Quantities in the order of 2 ?mol can be easily distinguished for primary alcohols in solution, even with the subwavelength optical path lengths used. A further display of the device sensitivity is shown through the analysis of commercial whiskeys, where there are clear, detectable differences between samples. Slight absorption variations were identified between samples of the same commercial brand, owing to a 2.5% difference in their alcoholic content. Results from data taken on subsequent days after system realignment are also presented, confirming the robustness of the technique, and the data extraction algorithm used. One final experiment, showing the possible use of this device to analyze aqueous biological samples is detailed; where biotin, a molecule known for its specific terahertz absorptions, is analyzed in solution. The device sensitivity is once again displayed, where quantities of 3 nmol can be clearly detected between samples.

Baragwanath, A. J.; Swift, G. P.; Dai, D.; Gallant, A. J.; Chamberlain, J. M.

2010-07-01

65

The analysis of alkyl aryl sulfonates by micro desulfonation and gas chromatography  

Microsoft Academic Search

The structural analysis of micro quantities of alkyl aryl sulfonates by presently known chemical and spectroscopic techniques\\u000a has been an exceedingly difficult task. The formidable nature of such analyses is due largely to the essential nonvolatility\\u000a of the sulfonates, a fact which precludes the application of gas-liquid chromatography and mass spectrometric techniques.\\u000a \\u000a The present paper describes an approach wherein gas

E. A. Setzkorn; A. B. Carel

1963-01-01

66

Gas–liquid dynamics at low Reynolds numbers in pillared rectangular micro channels  

Microsoft Academic Search

Most heterogeneously catalyzed gas–liquid reactions in micro channels are chemically\\/kinetically limited because of the high\\u000a gas–liquid and liquid–solid mass transfer rates that can be achieved. This motivates the design of systems with a larger surface\\u000a area, which can be expected to offer higher reaction rates per unit volume of reactor. This increase in surface area can be\\u000a realized by using

S. R. A. de Loos; J. van der Schaaf; R. M. Tiggelaar; T. A. Nijhuis; J. C. Schouten

2010-01-01

67

Enhancement of gas response of ZnO micro-nano structured films through plasma treatment  

Microsoft Academic Search

Films of ZnO micro-nano structures were deposited on quartz substrates and subsequently plasma treated in O2, N2 and CF4. It was found that exposure to oxygen plasma enhanced gas response to ethanol vapor of the ZnO films by a factor 2. The effect of surface plasma treatments on the gas response of the ZnO films was discussed in reference to

Jean-Jacques Delaunay; Kazumasa Yanagisawa; Toshiki Nishino; Ichiro Yamada

2007-01-01

68

Propulsion and Power Rapid Response R&D Support. Delivery Order 0013: Micro Gas Chromatography Tradeoff Study.  

National Technical Information Service (NTIS)

This effort seeks to extend the effort of the Dec. 2002 DARPA workshop on Micro Gas Analyzers (MGAs) to focus on the application of a Micro Gas Chromatograph (MGC). The primary goal of this study is to project MGA capabilities in terms of goals for compac...

U. Bonne G. Eden G. Frye-Mason R. Sacks R. Synovec

2003-01-01

69

Sputtered alumina as a novel stationary phase for micro machined gas chromatography columns.  

PubMed

Silica and graphite sputtering have previously been reported as novel solid stationary phase deposition techniques for micro gas chromatography columns. As a conventional solid stationary phase in gas chromatography, compatible with sputtering yet so far unreported, alumina was evaluated in this study. Alumina sputtered semi-packed micro columns were fabricated (including an activation step) and proved able to separate a mixture of volatile alkanes (C1-C4 with isomers) in less than 1 min. Kinetic and a thermodynamic evaluation led to calculation of 4,500 theoretical plates for ethane in 1.1 m (HETPmin?=?250 ?m) and a Gibbs free energy for propane of 30.2 kJ mol(-1), making this stationary phase's properties very close to those observed with silica-sputtered micro columns. PMID:23989966

Haudebourg, R; Matouk, Z; Zoghlami, E; Azzouz, I; Danaie, K; Sassiat, P; Thiebaut, D; Vial, J

2014-02-01

70

The fabrication of all-silicon micro gas chromatography columns using gold diffusion eutectic bonding  

NASA Astrophysics Data System (ADS)

Temperature programming of gas chromatography (GC) separation columns accelerates the elution rate of chemical species through the column, increasing the speed of analysis, and hence making it a favorable technique to speedup separations in microfabricated GCs (micro-GC). Temperature-programmed separations would be preferred in an all-silicon micro-column compared to a silicon-Pyrex® micro-column given that the thermal conductivity and diffusivity of silicon is 2 orders of magnitude higher than Pyrex®. This paper demonstrates how to fabricate all-silicon micro-columns that can withstand the temperature cycling required for temperature-programmed separations. The columns were sealed using a novel bonding process where they were first bonded using a gold eutectic bond, then annealed at 1100 °C to allow gold diffusion into silicon and form what we call a gold diffusion eutectic bond. The gold diffusion eutectic-bonded micro-columns when examined using scanning electron microscopy (SEM), scanning acoustic microscopy (SAM) and blade insertion techniques showed bonding strength comparable to the previously reported anodic-bonded columns. Gas chromatography-based methane injections were also used as a novel way to investigate proper sealing between channels. A unique methane elution peak at various carrier gas inlet pressures demonstrated the suitability of gold diffusion eutectic-bonded channels as micro-GC columns. The application of gold diffusion eutectic-bonded all-silicon micro-columns to temperature-programmed separations (120 °C min-1) was demonstrated with the near-baseline separation of n-C6 to n-C12 alkanes in 35 s.

Radadia, A. D.; Salehi-Khojin, A.; Masel, R. I.; Shannon, M. A.

2010-01-01

71

Fabry-Pérot cavity sensors for multipoint on-column micro gas chromatography detection.  

PubMed

We developed and characterized a Fabry-Pérot (FP) sensor module based micro gas chromatography (microGC) detector for multipoint on-column detection. The FP sensor was fabricated by depositing a thin layer of metal and a layer of gas-sensitive polymer consecutively on the endface of an optical fiber, which formed the FP cavity. Light partially reflected from the metal layer and the polymer-air interface generated an interference spectrum, which shifted as the polymer layer absorbed the gas analyte. The FP sensor module was then assembled by inserting the FP sensor into a hole drilled in the wall of a fused-silica capillary, which can be easily connected to the conventional gas chromatography (GC) column through a universal quick seal column connector, thus enabling on-column real-time detection. We characterized the FP sensor module based microGC detector. Sensitive detection of various gas analytes was achieved with subnanogram detection limits. The rapid separation capability of the FP sensor module assembled with both single- and tandem-column systems was demonstrated, in which gas analytes having a wide range of polarities and volatilities were well-resolved. The tandem-column system obtained increased sensitivity and selectivity by employing two FP sensor modules coated with different polymers, showing great system versatility. PMID:20441156

Liu, Jing; Sun, Yuze; Howard, Daniel J; Frye-Mason, Greg; Thompson, Aaron K; Ja, Shiou-Jyh; Wang, Siao-Kwan; Bai, Mengjun; Taub, Haskell; Almasri, Mahmoud; Fan, Xudong

2010-06-01

72

A micro-strip gas counter test with the RD20 front-end  

Microsoft Academic Search

A micro-strip gas counter equipped with an RC-CR (? = 30 ns) VLSI preamplifier (the RD20 chip) has been tested with minimum ionizing particles. The measured pulse shape and the signal to noise ratio are presented. The time resolution of the detector has been studied as a function of the charge collected at the input of the preamplifier with an

J. F. Clergeau; D. Contardo; R. Haroutunian; G. Smadja

1995-01-01

73

Generation of micro gas bubbles of uniform diameter in an ultrasonic field  

Microsoft Academic Search

Consecutive images of the fragmentation of capillary waves in an ultrasonic field were obtained using a high-speed video camera through a microscope at a frame rate of 500000 frames per second. The images showed that micro bubbles of uniform diameter from 4 to 15mum were generated at a constant periodic rate when a small amount of gas was introduced (via

Toshinori Makuta; Fumio Takemura; Eiji Hihara; Yoichiro Matsumoto; Masahiro Shoji

2006-01-01

74

Preconcentration Modeling for the Optimization of a Micro Gas Preconcentrator Applied to Environmental Monitoring  

Microsoft Academic Search

This paper presents the complete modeling of the preconcentration cycle for the optimization of a Micro Gas Preconcentrator applied to atmospheric pollution monitoring. The particularity of this modeling is based on the fact that it includes all equations governing not only the adsorption and desorption phenomena but also the detection phase. Two different approaches based on kinetic equations were used

Hadji Malick CAMARA; Philippe Breuil; Christophe PIJOLAT

75

Correlated column micro gas chromatography instrumentation for the vapor detection of contraband drugs in cargo containers  

Microsoft Academic Search

We have developed an instrument based on Micro Gas Chromatography ((mu) GC) for rapid, handheld detection of vapor signatures from contraband drugs in cargo containers. For this application, a key requirement is the ability to distinguish the vapor signatures of contraband drugs against the highly variable chemical backgrounds encountered in cargo containers. To achieve this, we split the sample and

Paul M. Holland; Robert V. Mustacich; James F. Everson; William Foreman; Michael Leone; Ann H. Sanders; Walter J. Naumann

1994-01-01

76

Development of membrane extraction with a sorbent interface–micro gas chromatography system for field analysis  

Microsoft Academic Search

The commercially available portable gas chromatographs have a rather limited scope of applications, typically allowing analysis of gaseous samples only, and having relatively poor sensitivity. Combination of those instruments with modern sampling\\/sample preparation techniques can remedy these problems. A Chrompack micro-GC system equipped with a thermal conductivity detector has been coupled to membrane extraction with a sorbent interface (MESI). The

Alina Segal; Tadeusz Górecki; Phillippe Mussche; Jurgen Lips; Janusz Pawliszyn

2000-01-01

77

The effect of pillar array in semi-packed micro gas chromatography  

Microsoft Academic Search

Micro pillars within separation columns (SC) offer higher sample capacity but also promote fluidic eddy motion which unlike other applications has a negative effect on gas chromatography (GC). Three different semi-packed column (SPC) configurations have been evaluated with respect to pillar spacing along the flow direction and number of pillars across channel. The efficiencies of SPCs have been compared to

Bassam Alfeeli; Shree Narayanan; Mathew McMillan; Daniel Hirtenstein; Gary Rice; Masoud Agah

2011-01-01

78

First reconfigurable MEMS separation columns for micro gas chromatography  

Microsoft Academic Search

We present herein for the first time reconfigurable chromatographic separation columns by merging MEMS and nanotechnology using self-assembly of thiol compounds on an electrodeposited gold surface in MEMS columns. This coupling provides: 1) the ability to fabricate both polar and non-polar stationary phases, affording the separation of gas mixtures with a wide range of boiling points and polarities; and 2)

H. Shakeel; G. Rice; M. Agah

2012-01-01

79

Demonstration of motionless Knudsen pump based micro-gas chromatography featuring micro-fabricated columns and on-column detectors.  

PubMed

This paper reports the investigation of a micro-gas chromatography (?GC) system that utilizes an array of miniaturized motionless Knudsen pumps (KPs) as well as microfabricated separation columns and optical detectors. A prototype system was built to achieve a flow rate of 1 mL min(-1) and 0.26 mL min(-1) for helium and dry air, respectively, when they were used as carrier gas. This system was then employed to evaluate GC performance compromises and demonstrate the ability to separate and detect gas mixtures containing analytes of different volatilities and polarities. Furthermore, the use of pressure programming of the KP array was demonstrated to significantly shorten the analysis time while maintaining a high detection resolution. Using this method, we obtained a high resolution detection of 5 alkanes of different volatilities within 5 min. Finally, we successfully detected gas mixtures of various polarities using a tandem-column ?GC configuration by installing two on-column optical detectors to obtain complementary chromatograms. PMID:21869988

Liu, Jing; Gupta, Naveen K; Wise, Kensall D; Gianchandani, Yogesh B; Fan, Xudong

2011-10-21

80

Lifetime characteristics of MicroStrip Gas Chambers  

Microsoft Academic Search

Accelerated ageing tests were performed on four test chambers using high intensity 8 keV X-rays. The effects of varying the following chamber parameters were investigated: strip metal (aluminium, gold), substrate type (Schott S8900, Desag D263) and gas mixture (ArDME, NeDME). After initial poor ageing results from an MSGC fabricated with aluminium strips on an S8900 substrate, chambers consistently withstood total

I. P. Duerdoth; J. Freestone; N. Lumb; S. Snow; R. J. Thompson

1997-01-01

81

Fabrication of micro-gas chromatograph columns for fast chromatography  

Microsoft Academic Search

Gas chromatography (GC) is one of the most widespread techniques used in laboratories as a way to separate and analyze complex\\u000a mixtures of volatile and semi-volatile compounds. The main advantage of miniaturization of these systems is the increased\\u000a performance due to the reduced time for analysis and reduced fabrication cost of the complex pneumatic flow system. In this\\u000a paper advanced

Abhinav Bhushan; Dawit Yemane; Dan Trudell; Edward B. Overton; Jost Goettert

2007-01-01

82

Characteristics of electrostatic gas micro-pump with integrated polyimide passive valves  

NASA Astrophysics Data System (ADS)

We report on the fabrication and characterization of electrostatic gas micro-pumps integrated with polyimide check valves. Touch-mode capacitance actuation, enabled by a fixed silicon electrode and a metal/polyimide diaphragm, creates the suction and push-out of the ambient gas; the gas flow is rectified by the check valves located at the inlet and outlet of the pump. The fabricated pumps were tested with various actuation voltages at different frequencies and duty cycles; an emphasis was placed on investigating the effect of valve flow conductance on the gas pumping characteristics. The pump with higher valve conductance could increase the operating frequency of the pump and affect the pumping characteristics from a pulsating flow to a continuous flow, leading to a higher gas flow rate. This electrostatic pump has a flow control resolution of 1 µL min-1 it could generate a gas flow up to 106 µL min-1.

Han, Jeahyeong; Yeom, Junghoon; Mensing, Glennys; Flachsbart, Bruce; Shannon, Mark A.

2012-09-01

83

Micro-size gas turbines create market opportunities  

SciTech Connect

Power plants in the 25 to 250 kW-size range will enable utilities, IPPs and ESCOs to provide economic power for a variety of applications. Small, low-cost, highly efficient gas turbines provide the utility industry with a four-generation technology that features numerous benefits and potential applications. These include firm power to isolated communities, commercial centers and industries; peak shaving for utility systems to reduce the incremental cost of additional loads; peak shaving for large commercial and industrial establishments to reduce demand charges, as well as standby, emergency power and uninterruptible power supply (UPS).

Scott, W.G. [International Power and Light (United States)

1997-09-01

84

A SIMPLE SILICON BASED NITRIC OXIDE SENSOR  

Microsoft Academic Search

Nitric oxide (NO) is known to mediate many beneficial physiology processes, motivating its detection in vivo as well as in vitro. Electrochemical detection provides the required cellular level determination of NO among several other techniques. In this work, electrochemical micro-sensors for both types of detection, in vivo and in vitro, were developed, exploring the silicon planar technology, which presents high

Rogerio Furlan; Koiti Arakai; Jorge J. Santiago-Aviles

85

Fast carbon nanotube detectors for micro gas chromatographs  

NASA Astrophysics Data System (ADS)

Highly sensitive and completely reversible chemiresistor detectors based on carbon nanotubes (CNTs) were fabricated for multi-component chemical analysis. CNT detectors were used in a series configuration with a gas chromatography column and exposed to a mixture of nine different compounds. It is shown that CNT detectors were able to show parts per billion (pbb) sensitivity responses to each individual component of the mixture and detect nine distinct chemical compounds in roughly 210 s when the detector operates in current stimulated desorption (CSD) mode. This is the first demonstration of an uncoated CNT detector to analyze multi-component chemical mixtures providing an alternative yet simple sensing approach for online air quality control and health monitoring applications.

Salehi-Khojin, Amin; Lin, Kevin Y.; Field, Christopher R.; Masel, Richard I.

2011-08-01

86

Current-Voltage Characteristics of DC Discharge in Micro Gas Jet Injected into Vacuum Environment  

NASA Astrophysics Data System (ADS)

A current-voltage characteristic of direct current (DC) gas discharge operated in a micro gas jet injected into a secondary electron microscope (SEM) chamber is presented. Ar gas was injected through a 30 ?m orifice gas nozzle (OGN) and was evacuated by an additional pump to keep the high vacuum environment. Gas discharges were ignited between the OGN as anode and a counter electrode of Si wafer. The discharge was self-pulsating in most of the cases while it was stable at lower pressure, larger gap length, and larger time averaged current. The self-pulsating discharge was oscillated by the RC circuit consisting of a stray capacitor and a large ballast resistor. The real time plots of voltage and current during the pulsating was investigated using a discharge model.

Matra, K.; Furuta, H.; Hatta, A.

2013-06-01

87

SILICON-BASED NEUROMORPHIC OLFACTORY PATHWAY IMPLEMENTATION  

Microsoft Academic Search

This paper describes our efforts to implement the world's first silicon olfactory system in aVLSI\\/MEMs. To achieve this requires integration of a biologically constained neuronal model, chemical micro-sensor technology and aVLSI spiking neuromorphic circuits. Here we describe our progress towards this goal, by presenting an olfactory bulb model, a reduced 70 element broadly-tuned chemosensor array (25 different chem- sensor tunings),

Thomas J. Koickal; Carlo Fulvi-Mari; James A. Covington; Julian W. Gardner; Alister Hamilton

88

Transient Flow Dynamics in Optical Micro Well Involving Gas Bubbles  

NASA Technical Reports Server (NTRS)

The Lab-On-a-Chip Application Development (LOCAD) team at NASA s Marshall Space Flight Center is utilizing Lab-On-a-Chip to support technology development specifically for Space Exploration. In this paper, we investigate the transient two-phase flow patterns in an optic well configuration with an entrapped bubble through numerical simulation. Specifically, the filling processes of a liquid inside an expanded chamber that has bubbles entrapped. Due to the back flow created by channel expansion, the entrapped bubbles tend to stay stationary at the immediate downstream of the expansion. Due to the huge difference between the gas and liquid densities, mass conservation issues associated with numerical diffusion need to be specially addressed. The results are presented in terms of the movement of the bubble through the optic well. Bubble removal strategies are developed that involve only pressure gradients across the optic well. Results show that for the bubble to be moved through the well, pressure pulsations must be utilized in order to create pressure gradients across the bubble itself.

Johnson, B.; Chen, C. P.; Jenkins, A.; Spearing, S.; Monaco, L. A.; Steele, A.; Flores, G.

2006-01-01

89

Micro-flame ionization detector with a novel structure for portable gas chromatograph.  

PubMed

A micro-flame ionization detector (micro-FID) for portable gas chromatograph (GC) based on conventional mechanical fabrication techniques was developed and evaluated. Structure was redesigned and dimensions were optimized for best performance. Air is introduced from upper part of the detector, flowing downwards into the burning chamber along a narrow round gap between the collection electrode and the inner wall of the detector body, forming a uniform flow field around the burning jet. The lowest detection limit of the mu-FID was 5x10(-13)g/s for n-decane, with a linear response range of five orders of magnitude. The consumption of gases is only 10 ml/min for hydrogen, and 120 ml/min for air, that is about 1/3 of the gases required for conventional FIDs. A comparative study between the micro-FID and commercial FID was also performed that proved the advantages of the micro-FID. The micro-FID is simple in structure, low heating power, and low consumption of gases that not only decrease the cost of running, but also increase the portability of GC for filed applications. PMID:20678662

Wang, Jianwei; Wang, Hua; Duan, Chunfeng; Guan, Yafeng

2010-08-15

90

Micro structure of gas-hydrate sediment: in situ sub-sampling from pressured sedimental samples  

NASA Astrophysics Data System (ADS)

Porosity of gas-hydrate bearing sediment is a key of gas production efficient from natural gas-hydrate reservoir. Developable natural gas-hydrates by conventional gas/oil production apparatus almost exist in unconsolidated sedimental layer. Because in situ evaluation of porosity with hydrate in pores is difficult, porosity values were discussed from hydrate bearing sediment quenched by liquid nitrogen. In the case of quenched sample, sand matrix in GH sediments could have been changed by freezing water in pores. Therefore, porosity data in previous reports may be over estimated comparing with nature of sediments at in situ condition. We developed in situ sub-sampling system for pressured natural gas-hydrate sediments. A small sedimental piece can be sampled from pressured gas hydrate sediments without pressure-release to atmosphere by using the our developed apparatus. In this presentation, we demonstrated sub-sampling from an artificial gas-hydrate sediment and measured micro-scale structure of the sub-sampled gas-hydrate sedimental piece. This work was supported by funding from the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) planned by the Ministry of Economy, Trade and Industry (METI), Japan.

Jin, Y.; Konno, Y.; Yoneda, J.; Egawa, K.; Kida, M.; Ito, T.; Suzuki, K.; Nakatsuka, Y.; Nagao, J.

2013-12-01

91

X-ray Polarimetry with a Micro-Pattern Gas Detector  

NASA Technical Reports Server (NTRS)

Topics covered include: Science drivers for X-ray polarimetry; Previous X-ray polarimetry designs; The photoelectric effect and imaging tracks; Micro-pattern gas polarimeter design concept. Further work includes: Verify results against simulator; Optimize pressure and characterize different gases for a given energy band; Optimize voltages for resolution and sensitivity; Test meshes with 80 micron pitch; Characterize ASIC operation; and Quantify quantum efficiency for optimum polarization sensitivity.

Hill, Joe

2005-01-01

92

Heat recovery from a micro-gas turbine by vapour jet refrigeration systems  

Microsoft Academic Search

The coproduction of electrical, thermal and refrigerating power is a well-known strategy which can significantly improve the efficiency of energy systems. Often in such tri-generation systems the refrigerating power is obtained by means of absorption cycles. This paper deals with the potential use of ejector-powered refrigerating cycles for heat recovery from a micro-gas turbine. At first, ejector performance is analyzed

Costante Invernizzi; Paolo Iora

2005-01-01

93

Laminar gas micro-flow convection characteristics due to steep density gradients  

Microsoft Academic Search

We report numerical simulation of pure continuum-based laminar gas micro-flow convection with steep density gradients, which cause, for the case of heated air, flattening and rate of flattening of axial velocity profile. This flattening is similar to the characteristics in constant-properties slip flow, and high rate of flattening can cause hydrodynamic undevelopment of flow---the reverse process of hydrodynamic development. By

S. P. Mahulikar; H. Herwig; O. Hausner; F. Kock

2004-01-01

94

MICRO-HEAT ENGINES, GAS TURBINES, AND ROCKET ENGINES THE MIT MICROENGINE PROJECT  

Microsoft Academic Search

This is a report on work in progress on microelectrical and mechanical systems (MEMS)-based gas turbine en- gines, turbogenerators, and rocket engines currently un- der development at MIT. Fabricated in large numbers in parallel using semiconductor manufacturing techniques, these engines are based on micro-high speed rotating machinery with the same power density as that achieved in their more familiar, full-sized

A. H. Epstein; S. D. Senturia; O. Al-Midani; A. Ayon; K. Breuer; K-S Chen; F. E. Ehrich; E. Esteve; L. Frechette; G. Gauba; R. Ghodssi; C. Groshenry; S. Jacobson; J. L. Kerrebrock; J. H. Lang; J. Lopata; A. Mehra; J. O. Mur Miranda; S. Nagle; D. J. Orr; E. Piekos; M. A. Schmidt; G. Shirley; S. M. Spearing; C. S. Tan; I. A. Waitz

1997-01-01

95

Adaptable chip-level microfluidic packaging for a micro-scale gas chromatograph  

Microsoft Academic Search

In this paper, we present a robust and adaptable technique to integrate microfluidics with an on-chip thiolate-monolayer-protected gold nanoparticle coated chemiresistorarray for vapor analyte detection in a micro-scale gas chromatograph (?GC). The process involves mounting a sensing chip and capillary tubes within a silicon “extension carrier” (EC), capping the chemiresistor-array with a glass lid, and sealing the microfluidic package with

Nathan Wardl; Xiaoyi Mul; Gustavo Serrano; Elizabeth Covington; Cagliyan Kurdak; Edward T. Zellers; Andrew J. Masonl; Wen Lil

2012-01-01

96

High rate operation of micro-strip gas chambers on diamond-coated glass  

Microsoft Academic Search

Very high rate operation of micro-strip gas chambers can be achieved using slightly conducting substrates. We describe preliminary measurements realized with detectors manufactured on boro-silicate glass coated, before the photo-lithographic processing, with a diamond layer having a surface resistivity of around 1014 Omega\\/□. Stable medium-term operation, and a rate capability largely exceeding the one obtained with identical plates manufactured on

Roger Bouclier; M Capéans-Garrido; Gilbert Million; Leszek Ropelewski; Fabio Sauli; T. Temmel; R. A. Cooke; S. Donnel; S. A. Sastri; N. Sonderer

1996-01-01

97

Multiple-stage microfabricated preconcentrator-focuser for micro gas chromatography system  

Microsoft Academic Search

The design, fabrication, and characterization of a multiple-stage Si microfabricated preconcentrator-focuser (?PCF) for a micro gas chromatography (?GC) system that can provide real-time quantification and identification of complex organic vapor mixtures are presented. The ?PCF consists of a Si microheater loaded with Carbopack B, Carbopack X, and Carboxen 1000 carbon adsorbent granules, and a Si micromachined cover plate. Deep reactive

Wei-Cheng Tian; Helena K. L. Chan; Chia-Jung Lu; Stella W. Pang; Edward T. Zellers

2005-01-01

98

A Low-Power Pressure and Temperature-Programmable Micro Gas Chromatography Column  

Microsoft Academic Search

This paper presents the theory, fabrication, and experimental results for a high-performance low-power micro gas chromatography column. The suspended-dielectric 1-m-long column is split into two sections, permitting independent pressure and temperature programming. Integrated column heaters have a mean resistance of 16.8 kOmega and a temperature coefficient of resistance of 431 ppm\\/degC. The suspended column requires 11 mW to raise its

Joseph A. Potkay; Gordon Randall Lambertus; Richard D. Sacks; Kensall D. Wise

2007-01-01

99

High sensitivity three-stage microfabricated preconcentrator-focuser for micro gas chromatography  

Microsoft Academic Search

The results of a high sensitivity three-stage microfabricated preconcentrator-focuser (?PCF) for a micro gas chromatograph (?GC) that can provide real-time monitoring for a quantification and identification analysis of complex organic vapor mixtures are presented. The device consists of a thick Si microheater loaded with graphitized carbon adsorbents and sealed with a Si micromachined cover plate. This three-stage device has effectively

W.-C. Tian; H. K. L. Chan; S. W. Pang; C.-J. Lu; E. T. Zellers

2003-01-01

100

On-chip Fabry–Pérot interferometric sensors for micro-gas chromatography detection  

Microsoft Academic Search

We fabricated and characterized on-chip Fabry–Pérot (FP) vapor sensors for the development of on-column micro-gas chromatography (?GC) detectors. The FP sensors were made by coating a thin layer of polymer on a silicon wafer. The air–polymer and polymer–silicon interfaces form an FP cavity, whose resonance wavelengths change in response to the vapor absorption\\/desorption, thus allowing for rapid detection and quantification

Karthik Reddy; Yunbo Guo; Jing Liu; Wonsuk Lee; Maung Kyaw Khaing Oo; Xudong Fan

2011-01-01

101

A novel micropreconcentrator employing a laminar flow patterned heater for micro gas chromatography  

Microsoft Academic Search

A simple micromachined process based on one photomask is developed for a novel micropreconcentrator (µPCT) used in a micro gas chromatograph (µGC). Unique thick silver heating microstructures with a high surface area for microheater of µPCT are fabricated by combining the microfluidic laminar flow technique and the Tollens’ reaction within a microchannel. Silver deposition using this laminar flow patterning technique

W-C Tian; T H Wu; C-J Lu; W R Chen; H J Sheen

2012-01-01

102

Nanoscale chemiresistor arrays with patterned nanoparticle interface layers for micro gas chromatography  

Microsoft Academic Search

Chemiresistor (CR) arrays with nanoscale electrode features and crosslinked thiolate-monolayer-protected gold nanoparticle (MPN) sensing layers were fabricated and characterized. These arrays, intended for ultimate use as detectors in a micro-scale gas chromatograph, employ interdigital electrodes (10 mum finger length with 100 nm width and spacing) patterned by electron-beam lithography. Films of different MPNs were sequentially deposited on the electrodes and

F. I. Bohrer; E. Covington; C. Kurdak; E. T. Zellers

2009-01-01

103

Fabrication of a gas flow device consisting of micro-jet pump and flow sensor  

NASA Astrophysics Data System (ADS)

A gas-flow device consisting of a valveless micro jet pump and flow sensor has been designed and fabricated using a Si micromachining process. The valveless micro pump is composed of a piezoelectric lead zirconate titanate (PZT) diaphragm actuator and flow channels. The design of the valvless pump focuses on a crosss junction formed by the neck of the pump chamber and one outlet and two opposite inlet channnels. The structure allows differences in the fluidic resistance and fluidic momentum inside the channels during each pump vibration cycle, which leads to the gas flow being rectified without valves. Before the Si micro-pump was developed, a prototype of it was fabricated using polymethyl methacrylate (PMMA) and a conventional machining techinique, and experiments on it confirmed the working principles underlying the pump. The Si micro-pump was designed and fabricated based on these working principles. The Si pump was composed of a Si flow channel plate and top and botom covers of PMMA. The flow channels were easily fabricated by using a silicon etching process. To investigate the effects of the step nozzle structure on the gas flow rate, two types of pumps with different channel depths (2D- and 3D-nozzle structures) were designed, and flow simulations were done using ANSYS-Fluent software. The simulations and excperimental data revealed that the 3D-nozzle structure is more advantageous than the 2D-nozzle structure. A flow rate of 4.3 ml/min was obtained for the pump with 3D-nozzle structure when the pump was driven at a resonant frequency of 7.9 kHz by a sinusoidal voltage of 40Vpp. A hot wire was fabricated as a gas-flow sensor near the outlet port on the Si wafer.

Tanaka, Katsuhiko; Dau, Van T.; Otake, Tomonori; Dinh, Thien X.; Sugiyama, Susumu

2008-12-01

104

Formation of a single micro bubble by controlled acoustic gas pressure wave  

NASA Astrophysics Data System (ADS)

We have developed micro bubble generator which can control both bubble size and generation frequency independently and accurately, by using acoustic gas pressure wave. However, though, the mechanism of this generator has not been fully understood. We further investigated the role of the acoustic gas pressure wave and found the optimal pressure wave for a single micro bubble formation. We succeeded in forming a bubble, whose radius was ranging from 0.3 to 0.8 mm, with extremely small standard deviation of less than 1 micro meter. By analyzing images taken by high-speed photography, detachment of a bubble from a nozzle, especially shrinkage of a capillary bridge connecting a bubble and a nozzle, is investigated in detail. Force balance on a growing bubble is evaluated with the help of experimental data of time rate of both bubble radius and position of the center of mass of a bubble, by applying a spherical bubble formation model. As results, we find that with the decrease in gas pressure, the capillary bridge is sucked down into a nozzle and added mass force is exerted in the upward direction, both of which promote detachment of a bubble from a nozzle.

Watanabe, Masao; Shirota, Minori; Sanada, Toshiyuki

2006-11-01

105

Efficient gas sensitivity in mixed bismuth ferrite micro (cubes) and nano (plates) structures  

SciTech Connect

Graphical abstract: Display Omitted Highlights: ? Micro (cubes) structure embedded in nano (plates) of bismuth ferrite was prepared by a chemical method. ? These structures were characterized by XRD and SEM. ? LPG, CO{sub 2} and NH{sub 4} gases were exposed. ? Properties related to gas sensors were measured and reported. -- Abstract: Mixed micro (cubes) and nano (plates) structures of bismuth ferrite (BFO) have been synthesized by a simple and cost-effective wet-chemical method. Structural, morphological and phase confirmation characteristics are measured using X-ray diffraction, field-emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray analysis techniques. The digital FE-SEM photo-images of BFO sample confirmed an incubation of discrete micro-cubes into thin and regularly placed large number of nano-plates. The bismuth ferrite, with mixed structures, films show considerable performance when used in liquefied petroleum (LPG), carbon dioxide (CO{sub 2}) and ammonium (NH{sub 3}) gas sensors application. Different chemical entities in LPG have made it more efficient with higher sensitivity, recovery and response times compared to CO{sub 2} and NH{sub 3} gases. Furthermore, effect of palladium surface treatment on the gas sensitivity and the charge transfer resistances of BFO mixed structures is investigated and reported.

Waghmare, Shivaji D.; Jadhav, Vijaykumar V.; Gore, Shaym K. [Center for Nanomaterials and Energy Devices, School of Physical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431606, Maharashtra (India)] [Center for Nanomaterials and Energy Devices, School of Physical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431606, Maharashtra (India); Yoon, Seog-Joon; Ambade, Swapnil B. [Inorganic Nanomaterials Laboratory, Department of Chemistry, Hanyang University, Seoul 133-1791 (Korea, Republic of)] [Inorganic Nanomaterials Laboratory, Department of Chemistry, Hanyang University, Seoul 133-1791 (Korea, Republic of); Lokhande, B.J. [Department of Physics, Solapur University, Solapur (India)] [Department of Physics, Solapur University, Solapur (India); Mane, Rajaram S., E-mail: rsmane_2000@yahoo.com [Center for Nanomaterials and Energy Devices, School of Physical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431606, Maharashtra (India); Han, Sung-Hwan, E-mail: shhan@hanyang.ac.kr [Inorganic Nanomaterials Laboratory, Department of Chemistry, Hanyang University, Seoul 133-1791 (Korea, Republic of)] [Inorganic Nanomaterials Laboratory, Department of Chemistry, Hanyang University, Seoul 133-1791 (Korea, Republic of)

2012-12-15

106

Micro Gas Chromatography Sample Injector for the Analysis of Natural Gas  

Microsoft Academic Search

This paper reports on a gas sample injection system for gas chromatography, with the specificity of being potentially able to sustain the harsh environment of natural gas. This device integrates six low-leak microvalves made from polyetheretherketone (PEEK) membranes on silicon substrates. We report on the design, operation principle, fabrication, and intrinsic characteristics of the microinjector as well as its measured

Kinda Nachef; Frédéric Marty; Eric Donzier; Bertrand Bourlon; Kamran Danaie; Tarik Bourouina

2012-01-01

107

SOLID PHASE MICRO EXTRACTION AND GAS CHROMATOGRAPHY ANALYSIS OF BENZENE , TOLUENE , ETHYL BENZENE AND XYLENE FROM WATER  

Microsoft Academic Search

SUMMARY A rapid, reproducible method is presented in this paper which includes Solid- Phase Micro extraction on a Supelco Fiber coated with PDMS, followed by Gas Chromatography for analyzing benzene, toluene, ethyl-benzene and xylene from water

Vlad Agotici; Ionel Ciucanu

108

Hydrogenated amorphous silicon–germanium thin films with a narrow band gap for silicon-based solar cells  

Microsoft Academic Search

Hydrogenated amorphous silicon–germanium (a-SixGe1?x:H) thin films were grown using very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD, 27.13MHz). The films were used in a silicon-based thin film solar cell. The films were grown from a gas mixture of silane (SiH4) and tunable germane (GeH4) gas that was diluted in hydrogen (H2). The results show that the optical band gap

Chao-Chun Wang; Chueh-Yang Liu; Shui-Yang Lien; Ko-Wei Weng; Jung-Jie Huang; Chia-Fu Chen; Dong-Sing Wuu

2011-01-01

109

Pressure-driven diffusive gas flows in micro-channels: from the Knudsen to the continuum regimes  

Microsoft Academic Search

Despite the enormous scientific and technological importance of micro-channel gas flows, the understanding of these flows,\\u000a by classical fluid mechanics, remains incomplete including the prediction of flow rates. In this paper, we revisit the problem\\u000a of micro-channel compressible gas flows and show that the axial diffusion of mass engendered by the density (pressure) gradient\\u000a becomes increasingly significant with increased Knudsen

Nishanth Dongari; Ashutosh Sharma; Franz Durst

2009-01-01

110

Selective and reversible ammonia gas detection with nanoporous film functionalized silicon photonic micro-ring resonator.  

PubMed

Portable, low cost and real-time gas sensors have a considerable potential in various biomedical and industrial applications. For such applications, nano-photonic gas sensors based on standard silicon fabrication technology offer attractive opportunities. Deposition of high surface area nano-porous coatings on silicon photonic sensors is a means to achieve selective, highly sensitive and multiplexed gas detection on an optical chip. Here we demonstrate selective and reversible ammonia gas detection with functionalized silicon-on-insulator optical micro-ring resonators. The micro-ring resonators are coated with acidic nano-porous aluminosilicate films for specific ammonia sensing, which results in a reversible response to NH(3)with selectivity relative to CO(2). The ammonia detection limit is estimated at about 5 ppm. The detectors reach a steady response to NH(3) within 30 and return to their base level within 60 to 90 seconds. The work opens perspectives on development of nano-photonic sensors for real-time, non-invasive, low cost and light weight biomedical and industrial sensing applications. PMID:22714172

Yebo, Nebiyu A; Sree, Sreeprasanth Pulinthanathu; Levrau, Elisabeth; Detavernier, Christophe; Hens, Zeger; Martens, Johan A; Baets, Roel

2012-05-21

111

Simulation of gas avalanche in a micro pixel chamber using Garfield++  

NASA Astrophysics Data System (ADS)

A micro pixel chamber (?-PIC), the development of which started in 2000 as a type of a micro pattern gas detector, has a high gas gain greater than 6000 in stable operation, a large detection area of 900 cm2, and a fine position resolution of about 120 ?m. However, for its development, simulation verification has not been very useful, because conventional simulations explain only part of the experimental data. On the other hand, some ?-PIC applications require precise understanding of the fluctuation of the gas avalanche and signal waveform for their improvement; therefore, there is a need to update the ?-PIC simulation. Hence, we adopted Garfield++, which is developed for simulating a microscopic avalanche in an effort to explain experimental data. The simulated avalanche size was well consistent with the experimental gas gain. Moreover, we calculated a signal waveform and successfully explained the pulse height and time-over-threshold. These results clearly indicate that the simulation of ?-PIC applications will improve and that Garfield++ simulation will easily facilitate the ?-PIC development.

Takada, A.; Tanimori, T.; Kubo, H.; Parker, J. D.; Mizumoto, T.; Mizumura, Y.; Iwaki, S.; Sawano, T.; Nakamura, K.; Taniue, K.; Higashi, N.; Matsuoka, Y.; Komura, S.; Sato, Y.; Namamura, S.; Oda, M.; Sonoda, S.; Tomono, D.; Miuchi, K.; Kabuki, S.; Kishimoto, Y.; Kurosawa, S.

2013-10-01

112

Thermal-Optical Switching of a Silicon Based Interference Filter.  

National Technical Information Service (NTIS)

We report thermal-optical switching using a silicon based interference filter fabricated by plasma enhanced chemical vapor deposition. A five film structure using high index films of amorphous Si and low index films of SiO2 comprised the device which yiel...

B. H. Augustine S. T. Feng E. A. Irene

1993-01-01

113

Interaction of metals and alloys with silicon-based ceramics  

Microsoft Academic Search

Silicon-based ceramics have been found to interact chemically with a number of metals and alloys when the materials were placed in physical contact in air at temperatures in the vicinity of 1000‡ C. Among the reaction products found after 100 h were silicides, silicates and carbides and the severity of the interaction depended on the temperature and the ease of

R. L. Mehan; D. W. Mckee

1976-01-01

114

Optoelectrical Detection System Using Porous Silicon-Based Optical Multilayers  

Microsoft Academic Search

Porous silicon-based multilayer structures for optical sensors have been simulated, fabricated and tested. The proper- ties of optical sensors using porous silicon multilayers can be ad- justed by appropriate substrate material, morphology, process pa- rameters in the pore formation process and by surface treatment (thermal oxidation). Heavily and lightly doped p-doped substrates have been used to realize porous silicon layers

Andras Kovacs; Prasad Jonnalagadda; Ulrich Mescheder

2011-01-01

115

THETRIS: A MICRO-SCALE TEMPERATURE AND GAS RELEASE MODEL FOR TRISO FUEL  

SciTech Connect

The dominating mechanism in the passive safety of gas-cooled, graphite-moderated, high-temperature reactors (HTRs) is the Doppler feedback effect. These reactor designs are fueled with sub-millimeter sized kernels formed into TRISO particles that are imbedded in a graphite matrix. The best spatial and temporal representation of the feedback effect is obtained from an accurate approximation of the fuel temperature. Most accident scenarios in HTRs are characterized by large time constants and slow changes in the fuel and moderator temperature fields. In these situations a meso-scale, pebble and compact scale, solution provides a good approximation of the fuel temperature. Micro-scale models are necessary in order to obtain accurate predictions in faster transients or when parameters internal to the TRISO are needed. Since these coated particles constitute one of the fundamental design barriers for the release of fission products, it becomes important to understand the transient behavior inside this containment system. An explicit TRISO fuel temperature model named THETRIS has been developed and incorporated into the CYNOD-THERMIX-KONVEK suite of coupled codes. The code includes gas release models that provide a simple predictive capability of the internal pressure during transients. The new model yields similar results to those obtained with other micro-scale fuel models, but with the added capability to analyze gas release, internal pressure buildup, and effects of a gap in the TRISO. The analyses show the instances when the micro-scale models improve the predictions of the fuel temperature and Doppler feedback. In addition, a sensitivity study of the potential effects on the transient behavior of high-temperature reactors due to the presence of a gap is included. Although the formation of a gap occurs under special conditions, its consequences on the dynamic behavior of the reactor can cause unexpected responses during fast transients. Nevertheless, the strong Doppler feedback forces the reactor to quickly stabilize.

J. Ortensi; A.M. Ougouag

2011-12-01

116

Direct observations of gas-hydrate formation in natural porous media on the micro-scale  

NASA Astrophysics Data System (ADS)

Gas hydrates (GH) are crystalline, inclusion compounds consisting of hydrogen-bonded water network encaging small gas molecules such as methane, ethane, CO2, etc (Sloan and Koh 2008). Natural gas hydrates are found worldwide in marine sediments and permafrost regions as a result of a reaction of biogenic or thermogenic gas with water under elevated pressure. Although a large amount of research on GH has been carried out over the years, the micro-structural aspects of GH growth, and in particular the contacts with the sedimentary matrix as well as the details of the distribution remain largely speculative. The present study was undertaken to shed light onto the well-established but not fully understood seismic anomalies, in particular the unusual attenuation of seismic waves in GH-bearing sediments, which may well be linked to micro-structural features. Observations of in-situ GH growth have been performed in a custom-build pressure cell (operating pressures up to several bar) mounted at the TOMCAT beam line of SLS/ PSI. In order to provide sufficient absorption contrast between phases and reduce pressure requirements for the cell we have used Xe instead of CH4. To the best of our knowledge this represents the first direct observation of GH growth in natural porous media with sub-micron spatial resolution and gives insight into the nucleation location and growth process of GH. The progress of the formation of sI Xe-hydrate in natural quartz sand was observed with a time-resolution of several minutes; the runs were conducted with an excess of a free-gas phase and show that the nucleation starts at the gas-water interface. Initially, a GH film is formed at this interface with a typical thickness of several ?m; this film may well be permeable to gas as suggested in the past - which would explain the rapid transport of gas molecules for further conversion of water to hydrate, completed in less than 20 min. Clearly, initially the growth is directed mainly into the liquid (and not into the gas phase as sometimes suggested). The observations of the 2D slices after full transformation show for all systems studied that hydrates tend to concentrate in the center of pore spaces and do not adhere in a systematic manner to quartz grains. Whether or not a thin film of water remained at the quartz-GH interface after completion of the reaction is presently under investigation. Sloan, E.D., Koh, C.A., (2008) Clathrate hydrates of natural gases. CRC Press, Boca Raton, FL.

Chaouachi, M.; Sell, K.; Falenty, A.; Enzmann, F.; Kersten, M.; Pinzer, B.; Saenger, E. H.; Kuhs, W. F.

2013-12-01

117

Remote-Raman and Micro-Raman Studies of Solid CO2, CH4, Gas Hydrates and Ice  

NASA Astrophysics Data System (ADS)

In this work, we have evaluated feasibility of using remote Raman and micro-Raman spectroscopy as potential nondestructive and non-contact techniques for detecting solid CO_2, CH_4 gas, and gas hydrates as well as water-ice on planetary surfaces.

Sharma, S. K.; Misra, A. K.; Lucey, P. G.; Exarhos, G. J.; Windisch, C. F., Jr.

2004-03-01

118

Direct measurement of neutral gas heating in a radio-frequency electrothermal plasma micro-thruster  

NASA Astrophysics Data System (ADS)

Direct measurements and modelling of neutral gas heating in a radio-frequency (13.56 MHz) electrothermal collisional plasma micro-thruster have been performed using rovibrational band matching of the second positive system of molecular nitrogen (N2) for operating pressures of 4.5 Torr down to 0.5 Torr. The temperature measured with decreasing pressure for 10 W power input ranged from 395 K to 530 K in pure N2 and from 834 K to 1090 K in argon with 1% N2. A simple analytical model was developed which describes the difference in temperatures between the argon and nitrogen discharges.

Greig, A.; Charles, C.; Hawkins, R.; Boswell, R.

2013-08-01

119

Experimental Investigation of A Twin Shaft Micro Gas-Turbine System  

NASA Astrophysics Data System (ADS)

Due to the fast depletion of fossil fuels and its negative impact on the environment, more attention has been concentrated to find new resources, policies and technologies, which meet the global needs with regard to fuel sustainability and emissions. In this paper, as a step to study the effect of burning low calorific value fuels on gas-turbine performance; a 50 kW slightly pressurized non-premixed tubular combustor along with turbocharger based twin shaft micro gas-turbine was designed and fabricated. A series of tests were conducted to characterize the system using LPG fuel. The tests include the analysis of the temperature profile, pressure and combustor efficiency as well as air fuel ratio and speed of the second turbine. The tests showed a stable operation with acceptable efficiency, air fuel ratio, and temperature gradient for the single and twin shaft turbines.

Sadig, Hussain; Sulaiman, Shaharin Anwar; Ibrahim, Idris

2013-06-01

120

Investigation of the Frequency Shift of a SAD Circuit Loop and the Internal Micro-Cantilever in a Gas Sensor  

PubMed Central

Micro-cantilever sensors for mass detection using resonance frequency have attracted considerable attention over the last decade in the field of gas sensing. For such a sensing system, an oscillator circuit loop is conventionally used to actuate the micro-cantilever, and trace the frequency shifts. In this paper, gas experiments are introduced to investigate the mechanical resonance frequency shifts of the micro-cantilever within the circuit loop(mechanical resonance frequency, MRF) and resonating frequency shifts of the electric signal in the oscillator circuit (system working frequency, SWF). A silicon beam with a piezoelectric zinc oxide layer is employed in the experiment, and a Self-Actuating-Detecting (SAD) circuit loop is built to drive the micro-cantilever and to follow the frequency shifts. The differences between the two resonating frequencies and their shifts are discussed and analyzed, and a coefficient ? related to the two frequency shifts is confirmed.

Guan, Liu; Zhao, Jiahao; Yu, Shijie; Li, Peng; You, Zheng

2010-01-01

121

Quantitative measurement of gas pressure drop along T-shaped micro channels by interferometry  

NASA Astrophysics Data System (ADS)

The study of gas flows in microchannels has received considerably more attention in the literature from a simulation perspective than an experimental. The majority of the experimental work has emphasis on the global measurements at the inlet or exit of the microchannel instead locally along it. In this paper some efforts were made to measure the pressure drop along T-shaped micro channel by using interferometry. The two side channels were served as gas entrances and they were both open to air and the channel outlet was being vacuumed during experiments. A Mach-Zehnder interference microscopy was built for the measurement of gas pressure drop along the mixing channel. Some points along the mixing channel were selected for interferometric measurements. Simulations were first developed in unsteady condition by using Ansys Fluent to verify the nonexistence of transient phenomena of gas flow in the defined condition and then run again in steady condition to get the theoretical pressure drop that was would be used for comparison with experimental results.

Li, Y.; Joseph, S.; Colin, S.; Baldas, L.; Barrot, C.; Orieux, S.; Newport, D.; Brandner, J. J.

2012-05-01

122

Exchange in silicon-based quantum computer architecture.  

PubMed

The silicon-based quantum computer proposal has been one of the actively pursued ideas during the past three years. Here we calculate the donor electron exchange in silicon and germanium, and demonstrate an atomic-scale challenge for quantum computing in Si (and Ge), as the six (four) conduction-band minima in Si (Ge) lead to intervalley electronic interference, generating strong oscillations in the exchange splitting of two-donor two-electron states. Donor positioning with atomic-scale precision within the unit cell thus becomes a decisive factor in determining the strength of the exchange coupling-a fundamental ingredient for two-qubit operations in a silicon-based quantum computer. PMID:11801039

Koiller, Belita; Hu, Xuedong; Das Sarma, S

2002-01-14

123

Silicon Based Anodes for Li-Ion Batteries  

SciTech Connect

Silicon is environmentally benign and ubiquitous. Because of its high specific capacity, it is considered one of the most promising candidates to replace the conventional graphite negative electrode used in today's Li ion batteries. Silicon has a theoretical specific capacity of nearly 4200 mAh/g (Li21Si5), which is 10 times larger than the specific capacity of graphite (LiC6, 372 mAh/g). However, the high capacity of silicon is associated with huge volume changes (more than 300 percent) when alloyed with lithium, which can cause severe cracking and pulverization of the electrode and lead to significant capacity loss. Significant scientific research has been conducted to circumvent the deterioration of silicon based anode materials during cycling. Various strategies, such as reduction of particle size, generation of active/inactive composites, fabrication of silicon based thin films, use of alternative binders, and the synthesis of 1-D silicon nanostructures have been implemented by a number of research groups. Fundamental mechanistic research has also been performed to better understand the electrochemical lithiation and delithiation process during cycling in terms of crystal structure, phase transitions, morphological changes, and reaction kinetics. Although efforts to date have not attained a commercially viable Si anode, further development is expected to produce anodes with three to five times the capacity of graphite. In this chapter, an overview of research on silicon based anodes used for lithium-ion battery applications will be presented. The overview covers electrochemical alloying of the silicon with lithium, mechanisms responsible for capacity fade, and methodologies adapted to overcome capacity degradation observed during cycling. The recent development of silicon nanowires and nanoparticles with significantly improved electrochemical performance will also be discussed relative to the mechanistic understanding. Finally, future directions on the development of silicon based anodes will be considered.

Zhang, Jiguang; Wang, Wei; Xiao, Jie; Xu, Wu; Graff, Gordon L.; Yang, Zhenguo; Choi, Daiwon; Li, Xiaolin; Wang, Deyu; Liu, Jun

2012-06-15

124

Silicon-Based Plasmonics for On-Chip Photonics  

Microsoft Academic Search

Silicon-based photonic devices dissipate substantially less power and provide a significantly greater information bandwidth than electronic components. Unfortunately, large-scale integration of photonic devices has been limited by their large, wavelength-scale size and the weak optical response of Si. Surface plasmons may overcome these two limitations. Combining the high localization of electronic waves with the propagation properties of optical waves, plasmons

Jennifer A. Dionne; Luke A. Sweatlock; Matthew T. Sheldon; A. Paul Alivisatos; Harry A. Atwater

2010-01-01

125

Porous silicon-based biosensor for pathogen detection  

Microsoft Academic Search

A porous silicon-based biosensor for rapid detection of bacteria was fabricated. Silicon (0.01ohmcm, p-type) was anodized electrochemically in an electrochemical Teflon cell containing ethanoic hydrofluoric acid solution to produce sponge-like porous layer of silicon. Anodizing conditions of 5mA\\/cm2 for 85min proved best for biosensor fabrication. A single-tube chemiluminescence-based assay, previously developed, was adapted to the biosensor for detection of Escherichia

Finny P. Mathew; Evangelyn C. Alocilja

2005-01-01

126

Corrosion of silicon-based ceramics in combustion environments  

Microsoft Academic Search

Silicon-based ceramics and composites are prime candidates for heat engines and heat exchanger structural components. In such applications these materials are exposed to combustion gases and deposit-forming corrodents. In this paper combustion environments are defined for various applications. These environments lead to five main types of corrosive degradation: passive oxidation, deposit-induced corrosion, active oxidation, scale\\/substrate interactions, and scale volatility. Each

Nathan S. Jacobson

1993-01-01

127

Progress in silicon-based non-oxide structural ceramics  

Microsoft Academic Search

The progress in monolithic Si3N4 and SiC as well as in Si3N4\\/SiC-composites for structural applications is reviewed. The conventional processing including the powder synthesis, densification and microstructural design is discussed. The mechanical properties of the resulting silicon based non-oxide ceramics and their industrial applications as structural components are summarized. As an alternative route to fabricate Si3N4\\/SiC composites the hybrid processing

Wolfgang Dressler; Ralf Riedel

1997-01-01

128

Analytical estimation of neutron yield in a micro gas-puff X pinch  

SciTech Connect

In this paper, we present the basic concepts for developing a micro x pinch as a small-scale neutron source. For compact sources, these concepts offer repetitive function at higher yields and pulsing rates than competing methods. The uniqueness of these concepts arises from the use of microelectronic technology to reduce the size of the target plasma and to efficiently heat the target gas. The use of repetitive microelectromechanical systems (MEMs) gas puff technology, as compared to cryogenic wires or solid targets (for the beam-target alternatives), has the potential to be robust and have a long lifetime because the plasma is not created from solid surfaces. The modeling suggests that a 50 J at the wall plug pulse could provide >10{sup 5} tritium (DT) neutrons and 10{sup 3} deuterium (DD) neutrons at temperatures of a few keV. At 1 kHz, this would be >10{sup 8} and 10{sup 6} neutrons per second, DT and DD, respectively, with a 250 {mu}m anode-cathode gap. DT gas puff devices may provide >10{sup 12} neutrons/s operating at 1 kHz and requiring 100 kW. The MEMs approach offers potentially high pulse rates and yields.

Derzon, M. S.; Galambos, P. C. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Hagen, E. C. [NSTec, North Las Vegas, Nevada 89031 (United States)

2012-12-01

129

Development of Electron Tracking Compton Camera using micro pixel gas chamber for medical imaging  

NASA Astrophysics Data System (ADS)

We have developed the Electron Tracking Compton Camera (ETCC) with reconstructing the 3-D tracks of the scattered electron in Compton process for both sub-MeV and MeV gamma rays. By measuring both the directions and energies of not only the recoil gamma ray but also the scattered electron, the direction of the incident gamma ray is determined for each individual photon. Furthermore, a residual measured angle between the recoil electron and scattered gamma ray is quite powerful for the kinematical background rejection. For the 3-D tracking of the electrons, the Micro Time Projection Chamber (?-TPC) was developed using a new type of the micro pattern gas detector. The ETCC consists of this ?-TPC (10×10×8 cm 3) and the 6×6×13 mm 3 GSO crystal pixel arrays with a flat panel photo-multiplier surrounding the ?-TPC for detecting recoil gamma rays. The ETCC provided the angular resolution of 6.6° (FWHM) at 364 keV of 131I. A mobile ETCC for medical imaging, which is fabricated in a 1 m cubic box, has been operated since October 2005. Here, we present the imaging results for the line sources and the phantom of human thyroid gland using 364 keV gamma rays of 131I.

Kabuki, Shigeto; Hattori, Kaori; Kohara, Ryota; Kunieda, Etsuo; Kubo, Atsushi; Kubo, Hidetoshi; Miuchi, Kentaro; Nakahara, Tadaki; Nagayoshi, Tsutomu; Nishimura, Hironobu; Okada, Yoko; Orito, Reiko; Sekiya, Hiroyuki; Shirahata, Takashi; Takada, Atsushi; Tanimori, Toru; Ueno, Kazuki

2007-10-01

130

Novel device for calibration-free flow rate measurements in micro gas chromatographic systems  

NASA Astrophysics Data System (ADS)

Accurate knowledge of flow rate is critical when quantifying analytes in a chromatographic separation. Using the flow rate, the area of a peak and the response factor of a detector one can calculate the total quantity of the analyte being examined. To date, this quantification has not been possible since no in situ method for flow rate detection within a detector existed. We have developed and tested a novel device and method for measuring the linear flow rate in a micro-gas chromatography (GC) system. Our design utilizes a high-sensitivity micro thermal conductivity detector (?TCD), which is capable of replacing a traditional TCD and requires no calibration for the precise measurement of flow rates. Furthermore, this measurement occurs exactly where the solute elutes from the GC separation column, the point at which knowledge of flow rate is most critical for analyte quantification. To the best of our knowledge, no other method of measuring the flow rate directly at the sensor currently exists.

Kaanta, B. C.; Chen, H.; Zhang, X.

2010-09-01

131

Development of the scalable readout system for micro-pattern gas detectors and other applications  

NASA Astrophysics Data System (ADS)

Developed within RD51 Collaboration for the Development of Micro-Pattern Gas Detectors Technologies, the Scalable Readout System (SRS) is intended as a general purpose multi-channel readout solution for a wide range of detector types and detector complexities. The scalable architecture, achieved using multi-Gbps point-to-point links with no buses involved, allows the user to tailor the system size to his needs. The modular topology enables the integration of different front-end ASICs, giving the user the possibility to use the most appropriate front-end for his purpose or to build a heterogeneous experimental apparatus which integrates different front-ends into the same DAQ system. Current applications include LHC upgrade activities, geophysics or homeland security applications as well as detector R&D. The system architecture, development and running experience will be presented, together with future prospects, ATCA implementation options and application possibilities.

Martoiu, S.; Muller, H.; Tarazona, A.; Toledo, J.

2013-03-01

132

Novel micro-optical collector design for a gas chromatographic detector based on atomic emission spectroscopy  

NASA Astrophysics Data System (ADS)

We report a novel micro-optical systems approach for gas chromatographic detection based on plasma excitation of the eluate and subsequent emission spectroscopic evaluation. Specifically, we propose a detector architecture that integrates a microhollow cathode setup and an optical collector system on a common planar microsystems platform. The collector consists of an array of identical imaging systems that surround the microplasma and couple the emitted light side-on into fibers via which it can be fed into a spectrometer. Elliptically shaped reflector profiles ensure nearly aberration-free achromatic imaging and hence a high coupling efficiency. This is confirmed by ray-tracing simulations. An experimental demonstration of the detector module is assembled. The elliptical profiles are milled out of aluminium with diamond tools on an ultraprecision machining center. Experimental tests with a He plasma prove that a higher optical coupling efficieny than with the traditional end-on signal pickup scheme can be achieved.

Gruber, Matthias; Bohling, Michael; Winkelmann, Holger; Knuppertz, Hans

2010-12-01

133

Rapid, sensitive, and multiplexed on-chip optical sensors for micro-gas chromatography.  

PubMed

We developed and characterized a rapid, sensitive and integrated optical vapor sensor array for micro-gas chromatography (?GC) applications. The sensor is based on the Fabry-Pérot (FP) interferometer formed by a micrometre-thin vapor-sensitive polymer layer coated on a silicon wafer. The thickness and the refractive index of the polymer vary in response to the vapor analyte, resulting in a change in the reflected intensity of the laser impinged on the sensor. In our study, four different polymers were coated on four wells pre-etched on a silicon wafer to form a spatially separated sensor array. A CMOS imager was employed to simultaneously monitor the polymers' response, thus enabling multiplexed detection of a vapor analyte passing through the GC column. A sub-second detection time was demonstrated. In addition, a sub-picogram detection limit was achieved, representing orders of magnitude improvement over the on-chip vapor sensors previously reported. PMID:22245960

Reddy, Karthik; Guo, Yunbo; Liu, Jing; Lee, Wonsuk; Oo, Maung Kyaw Khaing; Fan, Xudong

2012-03-01

134

Determination of priority organic micro-pollutants in water by gas chromatography coupled to triple quadrupole mass spectrometry  

Microsoft Academic Search

A multiclass method has been developed for screening, quantification and confirmation of organic micro-pollutants in water by gas chromatography coupled to mass spectrometry with a triple quadrupole analyzer. The work has been focused on the determination of more than 50 compounds belonging to different chemical families: 19 organochlorine and organophosphorus insecticides, 6 herbicides, 7 polychlorinated biphenyls, 16 polycyclic aromatics hydrocarbons,

E. Pitarch; C. Medina; T. Portolés; F. J. López; F. Hernández

2007-01-01

135

Studies of Air-Sea Gas Transfer and Micro Turbulence at the Ocean Surface using Passive Thermography  

Microsoft Academic Search

Knowledge about the mechanisms of mass transfer across the aqueous boundary layer is still marginal because of the lack of suitable experimental techniques. We present a new technique to measure the air-water gas transfer rate and the spatial structure of the micro turbulence at the ocean surface using passive thermography. We make use of the fact that due to radiative

U. Schimpf; H. Hauecker; B. Jahne

136

Simultaneous determination of chlorinated organic compounds from environmental samples using gas chromatography coupled with a micro electron capture detector and micro-plasma atomic emission detector  

NASA Astrophysics Data System (ADS)

Water and sediment samples were screened simultaneously for the presence of polychlorinated organic compounds using gas chromatography (GC) coupled with an micro electron capture detector (?-ECD) and a newly developed helium plasma based on a micro-atomic emission detector (?-AED). The GC column effluent was split 15:85 between two detectors. In this way, two chromatograms, one obtained by ?-ECD and another by ?-AED, were recorded simultaneously. ?-, ?-hexachlorocyclohexane and p, p'-DDE were detected. RSDs of the monitoring results from the two detection methods were <20% for the three compounds. A detection limit of 8.5 pg and at least 3 orders of magnitude of linear range for ?-AED was observed.

Quan, Xie; Chen, Shuo; Platzer, Bernhard; Chen, Jingwen; Gfrerer, Marion

2002-01-01

137

X-ray Polarization Measurements with a Micro-pattern Gas Polarimeter  

NASA Technical Reports Server (NTRS)

The benefits of Astrophysical X-ray polarization measurements have been discussed in the literature for decades and with respect to a variety of detectors. Despite this, a dedicated polarimeter for the measurement of Astrophysical sources has not flown since the 1970's, when the definitive measurement of the Crab Nebula was made. More recently, an indirect measurement of the polarization of two gamma-ray bursts has been extracted from BATSE data, re-emphasizing the importance of polarization measurements in constraining a physical model. We describe a sensitive and, and extremely versatile, photoelectric polarimeter using a micro-pattern gas detector, with an 80micron pixel ASIC anode, to image the primary photoelectron track. The detector can be optimized to a preferred energy range between 1 keV and 50 keV. We present measurements of polarized 4.5 keV X-rays and unpolarized 6 keV X-rays obtained with a prototype detector using Carbon Dioxide gas.

Hill, J. E.; Black, J. K.; Deines-Jones, P.; Jahoda, K.; Bellazzini, R.; Brez, A.; Costa, E.; Kaaret, P.; Minuti, M.; Spandre, G.; Swank, J. H.

2006-01-01

138

A novel micropreconcentrator employing a laminar flow patterned heater for micro gas chromatography  

NASA Astrophysics Data System (ADS)

A simple micromachined process based on one photomask is developed for a novel micropreconcentrator (µPCT) used in a micro gas chromatograph (µGC). Unique thick silver heating microstructures with a high surface area for microheater of µPCT are fabricated by combining the microfluidic laminar flow technique and the Tollens’ reaction within a microchannel. Silver deposition using this laminar flow patterning technique provides a higher deposition rate and easier microfabrication compared to conventional micromachined technologies for thick metal microstructures (>200 µm). An amorphous and porous carbon film that functions as an adsorbent is grown on microheaters inside the microchannel. The µPCT can be heated to >300 °C rapidly by applying a constant electrical power of ˜1 W with a heating rate of 10 °C s-1. Four volatile organic compounds, acetone, benzene, toluene and xylene, are collected through the proposed novel µPCTs and separated successfully using a 17 m long gas chromatography column. The peak widths at half height (PWHHs) of the four compounds are relatively narrow (<6 s), and the minimum PWHH of 3.75 s is obtained for acetone. The preconcentration factors are >38 000 for benzene and toluene.

Tian, W.-C.; Wu, T. H.; Lu, C.-J.; Chen, W. R.; Sheen, H. J.

2012-06-01

139

Enhancement of gas response of ZnO micro-nano structured films through plasma treatment  

NASA Astrophysics Data System (ADS)

Films of ZnO micro-nano structures were deposited on quartz substrates and subsequently plasma treated in O2, N2 and CF4. It was found that exposure to oxygen plasma enhanced gas response to ethanol vapor of the ZnO films by a factor 2. The effect of surface plasma treatments on the gas response of the ZnO films was discussed in reference to surface morphology observed by high-magnification SEM and surface chemical state determined by XPS. SEM observation revealed that O2 plasma treatment induced less surface roughening than N2 and CF4 plasmas, in agreement with the view that O2 plasma should reduce preferential sputtering. Deconvolution of the O 1s X-ray photoelectron peak indicated an increase in the Zn-O bond surface density relatively to O-H bond density for the O2 plasma treated surface, whereas the O-H bond surface density was increased relatively to the Zn-O bond density for the N2 and CF4 plasma treated films. The O2 plasma was found to partially clean the surface from hydroxyl groups and to expose more Zn cations, which might have caused the enhancement of sensor response by increasing the density of active sites for oxidation/reduction reactions.

Delaunay, Jean-Jacques; Yanagisawa, Kazumasa; Nishino, Toshiki; Yamada, Ichiro

2007-03-01

140

Mass flow rate prediction of pressure-temperature-driven gas flows through micro/nanoscale channels  

NASA Astrophysics Data System (ADS)

In this paper, we study mass flow rate of rarefied gas flow through micro/nanoscale channels under simultaneous thermal and pressure gradients using the direct simulation Monte Carlo (DSMC) method. We first compare our DSMC solutions for mass flow rate of pure temperature-driven flow with those of Boltzmann-Krook-Walender equation and Bhatnagar-Gross-Krook solutions. Then, we focus on pressure-temperature-driven flows. The effects of different parameters such as flow rarefaction, channel pressure ratio, wall temperature gradient and flow bulk temperature on the thermal mass flow rate of the pressure-temperature-driven flow are examined. Based on our analysis, we propose a correlated relation that expresses normalized mass flow rate increment due to thermal creep as a function of flow rarefaction, normalized wall temperature gradient and pressure ratio over a wide range of Knudsen number. We examine our predictive relation by simulation of pressure-driven flows under uniform wall heat flux (UWH) boundary condition. Walls under UWH condition have non-uniform temperature distribution, that is, thermal creep effects exist. Our investigation shows that developed analytical relation could predict mass flow rate of rarefied pressure-driven gas flows under UWH condition at early transition regime, that is, up to Knudsen numbers of 0.5.

Akhlaghi, Hassan; Roohi, Ehsan

2014-01-01

141

Demonstration of a silicon-based quantum cellular automata cell  

NASA Astrophysics Data System (ADS)

We report on the demonstration of a silicon-based quantum cellular automata (QCA) unit cell incorporating two pairs of metallically doped (n+) phosphorus-implanted nanoscale dots, separated from source and drain reservoirs by nominally undoped tunnel barriers. Metallic cell control gates, together with Al-AlOx single electron transistors for noninvasive cell-state readout, are located on the device surface and capacitively coupled to the buried QCA cell. Operation at subkelvin temperatures was demonstrated by switching of a single electron between output dots, induced by a driven single electron transfer in the input dots. The stability limits of the QCA cell operation were also determined.

Mitic, M.; Cassidy, M. C.; Petersson, K. D.; Starrett, R. P.; Gauja, E.; Brenner, R.; Clark, R. G.; Dzurak, A. S.; Yang, C.; Jamieson, D. N.

2006-07-01

142

Coating Silicon-Based Ceramics With Durable Mullite  

NASA Technical Reports Server (NTRS)

Improved plasma-spraying process deposits mullite on silicon carbide substrates. Prevents formation of amorphous mullite by maintaining high temperature of sprayed deposite to allow crystallization to occur. Deposited mullite adheres to substrate and exhibits little or no cracking during thermal cycling. Provides substantially greater resistance to oxidation in dry air and corrosion by molten salt. Process expected useful in depositing mullite on substrates made of other silicon-based ceramics and other ceramic substrates having coefficients of thermal expansion similar to those of mullite.

Miller, Robert A.; Jacobson, Nathan S.; Lee, Kang N.

1996-01-01

143

Characteristics analysis and dynamic responses of micro-gas-lubricated journal bearings with a new slip model  

NASA Astrophysics Data System (ADS)

In this paper, a new slip model based on kinetic theory of gases for gas-lubricated journal bearings in micro-electro-mechanical systems (MEMS) is applied using a physical approach. The corresponding modified governing equation and mathematic model are presented and the flow rate is plotted versus the inverse Knudsen number. Pressure distributions along the gas bearing at various Knudsen numbers and bearing numbers are plotted and the load carrying capacities are also obtained. A numerical analysis of a rigid rotor supported by gas-lubricated journal bearings is presented for dynamic behaviour. The slip flow effect on the properties, including pressure distribution, load carrying capacity and dynamic coefficients, of the micro-gas-lubricated journal bearings and dynamic responses of the micro rotor-bearing system are estimated and analysed in detail. It is shown that the dynamic coefficients increase with increasing bearing number except for two damping coefficients and the rotor-bearing system runs at a much higher rotating speed to keep stable when slip flow occurs. Moreover, the oscillation period of the rotor operating with the slip model is longer than that with the continuum flow. In addition, the whirl frequency is reduced from 0.422 to 0.079 under the slip effect. Therefore, the results of this study contribute to a further understanding of the characteristics and nonlinear dynamics of gas-film rotor-bearing systems in MEMS.

Zhang, Wen-Ming; Meng, Guang; Huang, Hai; Zhou, Jian-Bin; Chen, Jie-Yu; Chen, Di

2008-08-01

144

Thermal/environmental barrier coating system for silicon-based materials  

NASA Technical Reports Server (NTRS)

A coating system for a substrate containing a silicon-based material, such as silicon carbide-containing ceramic matrix materials containing silicon carbide and used to form articles exposed to high temperatures, including the hostile thermal environment of a gas turbine engine. The coating system includes a layer of barium strontium aluminosilicate (BSAS) as a bond coat for a thermal-insulating top coat. As a bond coat, the BSAS layer serves to adhere the top coat to a SiC-containing substrate. The BSAS bond coat exhibits sufficient environmental resistance such that, if the top coat should spall, the BSAS bond coat continues to provide a level of environmental protection to the underlying SiC-containing substrate.

Spitsberg, Irene T. (Inventor); Wang, Hongyu (Inventor)

1999-01-01

145

Spectroscopic and electric characterization of an atmospheric pressure segmented gas discharge with micro hollow electrodes  

NASA Astrophysics Data System (ADS)

We present the results of an optical emission spectroscopy and electric study of segmented micro hollow gas discharge source (SMHGD) operating at atmospheric pressure in DC regime. This microdischarge source with 1 mm discharge channel consists of five metal discs separated by alumina. Three central discs are made of copper while stainless steel was used for the cathode and anode. In order to perform side on measurements, 1.5 mm diameter side hole was drilled through central copper disc. The electron temperature ( T e ), gas temperature ( T g ) and electron number density ( N e ) were measured in argon, argon-hydrogen and helium SMHGDs operating in the voltage range (220 to 475) V and currents 40 mA, 60 mA and 80 mA. Boltzmann plots of relative Ar I and He I line intensities were used to measure T e = (3700-5500) K in argon and (2500-2800) K in helium SMHGDs. Same technique is applied to N2 ( C 3 ? u- B 3 ? g ) band to measure T g in the range (700-900) K in Ar and He and (1400-1600) K in Ar-H2 mixture. Line profiles of hydrogen the H ? line in argon and the ratio of He I 447.1 nm line intensity and its forbidden component in helium are employed to determine N e ? (2-4) × 1014 cm-3 in the center of SMHGD. By measuring SMHGD disc voltages, the longitudinal distribution of plasma potential and electric field strength are determined.

Jovovi?, Jovica; Konjevi?, Nikola

2014-03-01

146

Micro-machined planar field asymmetric ion mobility spectrometer as a gas chromatographic detector  

NASA Technical Reports Server (NTRS)

A planar high field asymmetric waveform ion mobility spectrometer (PFAIMS) with a micro-machined drift tube was characterized as a detector for capillary gas chromatography. The performance of the PFAIMS was compared directly to that of a flame ionization detector (FID) for the separation of a ketone mixture from butanone to decanone. Effluent from the column was continuously sampled by the detector and mobility scans could be obtained throughout the chromatographic analysis providing chemical inforrmation in mobility scans orthogonal to retention time. Limits of detection were approximately I ng for measurement of positive ions and were comparable or slightly better than those for the FID. Direct comparison of calibration curves for the FAIMS and the FID was possible over four orders of magnitude with a semi-log plot. The concentration dependence of the PFAIMS mobility scans showed the dependence between ion intensity and ion clustering, evident in other mobility spectrometers and atmospheric pressure ionization technologies. Ions were identified using mass spectrometry as the protonated monomer and the proton bound dimer of the ketones. Residence time for column effluent in the PFAIMS was calculated as approximately 1 ms and a 36% increase in extra-column broadening versus the FID occurred with the PFAIMS.

Eiceman, G. A.; Nazarov, E. G.; Miller, R. A.; Krylov, E. V.; Zapata, A. M.

2002-01-01

147

Cycle Analysis of Micro Gas Turbine-Molten Carbonate Fuel Cell Hybrid System  

NASA Astrophysics Data System (ADS)

A hybrid system based on a micro gas turbine (µGT) and a high-temperature fuel cell, i.e., molten carbonate fuel cell (MCFC) or solid oxide fuel cell (SOFC), is expected to achieve a much higher efficiency than conventional distributed power generation systems. In this study, a cycle analysis method and the performance evaluation of a µGT-MCFC hybrid system, of which the power output is 30kW, are investigated to clarify its feasibility. We developed a general design strategy in which a low fuel input to a combustor and higher MCFC operating temperature result in a high power generation efficiency. A high recuperator temperature effectiveness and a moderate steam-carbon ratio are the requirements for obtaining a high material strength in a turbine. In addition, by employing a combustor for complete oxidation of MCFC effluents without additional fuel input, i.e., a catalytic combustor, the power generation efficiency of a µGT-MCFC is achieved at over 60%(LHV).

Kimijima, Shinji; Kasagi, Nobuhide

148

Low dead volume integrated separation columns and Fabry-Pérot sensors for micro-gas chromatography  

NASA Astrophysics Data System (ADS)

We developed a monolithic subsystem that integrates a micro-gas chromatography (?GC) separation column and on-column, non-destructive Fabry-Pérot (FP) vapor sensors on a single silicon chip. The device was fabricated using deep reactive ion etching of silicon to create fluidic channels and polymers were deposited on the same silicon chip to act as a stationary phase or an FP sensor, thus avoiding dead volumes caused by the interconnects between the column and sensor traditionally used in ?GC. Two integration designs were studied. In the first design, the ?GC column was coated with a layer of polymer that served as both the stationary phase and the FP sensor, which has the greatest level of integration. In the second design, a FP sensor array spray-coated with different vapor sensing polymers was integrated with the ?GC column, which significantly improves the system flexibility and detection sensitivity. With this design, we show that the FP sensors have a detection limit on the order of tens of picograms with a sub-second response time. Furthermore, FP sensor array are shown to respond to a mixture of analytes separated by the integrated separation channel, allowing for the construction of response patterns, which, along with retention time, can be used as a basis of analyte identification.

Reddy, Karthik; Liu, Jing; Khaing Oo, Maung Kyaw; Fan, Xudong

2013-03-01

149

Effectiveness of a Micro Gas Turbine Cogeneration System using in a Residential Area  

NASA Astrophysics Data System (ADS)

For energy conservation and CO2 reduction, cogeneration systems may be useful. This paper shows the effectiveness of the cogeneration system, used in a residential area and designed to supply heat by hot water pipelines. The cogeneration system consists of a micro gas turbine (MGT) generator and a boiler. Entire heat load is supplied by the MGT or boiler, while an electric load may be supplied by an electric power company. Optimal diameter of the hot water pipeline becomes large when the load density becomes low. Total heat supply loss is less then 10% for moderate temperature region. However, it exceeds 20% for a sparse load in the cold region. The MGT should generates heat just required by the load for the primary energy or cost minimum operation. In the moderate temperature region, primary energy reduction ratio is positive in almost all cases, while it becomes negative in the cold region. On the other hand, CO2 emission almost always decreases in some extent. In the warm or moderate temperature region, MGT cogeneration systems are effective for energy conservation. They are also effective for CO2 reduction in almost all cases.

Kawamoto, Teru; Yamada, Masahiro

150

Silicon-Based Optical Modulator with Ferroelectric Layer  

NASA Technical Reports Server (NTRS)

According to a proposal, a silicon dioxide layer in a high-speed, low-power, silicon- based electro-optical modulator would be replaced by a layer of lead zirconate titanate or other ferroelectric oxide material. The purpose of this modification is to enhance the power performance and functionality of the modulator. In its unmodified form, the particular silicon- based electro-optical modulator is of an advanced design that overcomes the speed limitation of prior silicon-based electro- optical modulators. Whereas modulation frequencies of such devices had been limited to about 20 MHz, this modulator can operate at modulation frequencies as high as 1 GHz. This modulator can be characterized as a silicon-waveguide-based metal oxide/semiconductor (MOS) capacitor phase shifter in which modulation of the index of refraction in silicon is obtained by exploiting the free-charge-carrier-plasma dispersion effect. As shown in the figure, the modulator includes an n-doped crystalline silicon slab (the silicon layer of a silicon- on-insulator wafer) and a p-doped polycrystalline silicon rib with a gate oxide layer (the aforementioned silicon dioxide layer) sandwiched between them. Under accumulation conditions, the majority charge carriers in the silicon waveguide modify the index of refraction so that a phase shift is induced in the optical mode propagating in the waveguide. The advantage of using an MOS capacitor phase shifter is that it is possible to achieve high modulation speed because there are no slow carrier-generation or -recombination processes involved in the accumulation operation. The main advantage of the proposed substitution of a ferroelectric oxide layer for the silicon dioxide layer would arise from the spontaneous polarization effect of the ferroelectric layer: This spontaneous polarization would maintain accumulation conditions in the absence of applied voltage. Consequently, once the device had been switched to a given optical state, it would remain in that state, even in the absence of applied voltage (in other words, even with power turned off). A secondary advantage is that because the ferroelectric layer would have an index of refraction larger than that of silicon dioxide, there could be some reduction of optical losses attributable to fabrication of the modulator

Sheldon, Douglas

2006-01-01

151

Low-pressure micro-strip gas chamber and a search for a high-efficiency secondary-electron emitter  

SciTech Connect

The test beam performance of a low-pressure micro-strip gas chamber with a thick CsI secondary-electron emitting surface as the source of primary ionization is presented. A study of the secondary-electron yield of CsI and KCl coated surfaces are discussed, as well as a promising new technique, CsI-treated CVD diamond films.

Anderson, D.F.; Kwan, S. [Fermi National Accelerator Lab., Batavia, IL (United States). Particle Detector Group; Sbarra, C. [INFN-Pisa (Italy)

1994-11-01

152

Patterning of thin tin oxide film with nano-size particle for two-dimensional micro-gas sensor array  

Microsoft Academic Search

Thin tin oxide film with nano-size particle was prepared on silicon substrate by hydrothermal synthetic method and successive sol–gel spin coating method. The fabrication method of tin oxide film with ultrafine nano-size crystalline structure was tried to be applied to fabrication of micro-gas sensor array on silicon substrate. The tin oxide film on silicon substrate was well patterned by chemical

Wan-Young Chung; Jun-Woo Lim

2003-01-01

153

Determination of petroleum contamination in shellfish using solid phase micro-extraction with gas chromatography-mass spectrometry  

Microsoft Academic Search

Headspace solid phase micro-extraction (HS-SPME) has been applied as a sampling technique for the determination of petroleum contamination in shellfish using capillary gas chromatography-mass spectrometry (GC-MS). A poly(dimethylsiloxane) fused silica fibre (100 µm thickness) was found to be satisfactory for the extraction of a range of aliphatic hydrocarbons (HCs) from homogenised shellfish tissues. The SPME conditions, including temperature, salt content,

Mary A. Stack; Sharon O'Connell; Kevin J. James

2002-01-01

154

Determination of benzene, toluene, ethylbenzene and xylenes in air by solid phase micro-extraction\\/gas chromatography\\/mass spectrometry  

Microsoft Academic Search

The aim of the study was to analyse BTEX compounds (benzene, toluene, ethylbenzene, xylenes) in air by solid phase micro-extraction\\/gas chromatography\\/mass spectrometry (SPME\\/GC\\/MS), and this article presents the features of the calibration method proposed. Examples of real-world air analysis are given. Standard gaseous mixtures of BTEX in air were generated by dynamic dilution. SPME sampling was carried out under non-equilibrium

Simonetta Tumbiolo; Jean-François Gal; Pierre-Charles Maria; Orfeo Zerbinati

2004-01-01

155

Reliability characterization of silicon-based germanium waveguide photodetectors  

NASA Astrophysics Data System (ADS)

A silicon-based germanium waveguide photodetector was demonstrated and its reliability related items were investigated. For different reverse biases, the slopes of the dark current increment versus stress time curves were first found to be the same, which made the lifetime extrapolation feasible. The lifetime of the photodetector under different bias was predicted by using a simple extrapolation method. In order to maintain the 10-year lifetime of the photodetector, the bias voltage should be kept lower than -3 V. For the first time, the degradation mechanism under stress biases was analyzed in detail by the reaction-diffusion (RD) model. The experimental results agree well with the theoretical derivation based on RD model.

Tu, Zhijuan; Zhou, Zhiping; Wang, Xingjun

2014-05-01

156

Silicon-based counterpart of alpha-graphyne  

NASA Astrophysics Data System (ADS)

We present the first principles density functional calculations of electronic structure and energetics of silicon-based counterpart of ?-graphyne, labeled as ?-silicyne. Both LDA and GGA functionals are applied for exchange–correlation potentials. We show that graphyne-like silicon in 2D buckled structure (equilibrium buckling ?z?0.73 and ?z?1.45Å) has ?2.33eV and ?1.96eV lower energies than planar geometry for GGA and LDA functionals, respectively. The single and triple bond lengths of silicon are consistent with previously reported values. As a different case from graphyne, which is semimetallic, the electronic band structures of buckled ?-silicyne do not show Dirac fermion indicating a metallic nature. The metallic character of the system is largely determined by p-electronic states of the triple bonded silicon atoms.

Aktürk, E.; Göko?lu, G.

2014-03-01

157

Solidphase micro-extraction–gas chromatography–mass spectrometry and headspace-gas chromatography of tetrahydrocannabinol, amphetamine, methamphetamine, cocaine and ethanol in saliva samples  

Microsoft Academic Search

In the present work, a method was developed aiming at the serial detection of tetrahydrocannabinol (THC), amphetamine, methamphetamine, cocaine and ethanol in saliva. Saliva samples were submitted to an initial headspace procedure for ethanol determination by gas chromatography\\/flame ionization detector (GC–FID). After this step, two consecutive solid-phase micro-extractions (SPME) were carried out: THC was extracted by submersing a polydimethylsiloxane fiber

Mauricio Yonamine; Nadia Tawil; Regina Lucia de Moraes Moreau; Ovandir Alves Silva

2003-01-01

158

Fabrication and properties of PZT micro cantilevers using isotropic silicon dry etching process by XeF 2 gas for release process  

Microsoft Academic Search

Fabrication processes of PZT micro cantilevers using isotropic silicon dry etching process by XeF2 gas of front side were newly proposed and investigated. The purpose of study was to compare the proposed processes using only front side for release process of PZT micro cantilevers with conventional processes using bulk silicon micromachining of backside, and so on. In case of the

Joon-Shik Park; Hyo-Derk Park; Sung-Goon Kang

2005-01-01

159

In-situ formation of nanoparticles within a silicon-based matrix  

DOEpatents

A method for encapsulating nanoparticles with an encapsulating matrix that minimizes aggregation and maintains favorable properties of the nanoparticles. The matrix comprises silicon-based network-forming compounds such as ormosils and polysiloxanes. The nanoparticles are synthesized from precursors directly within the silicon-based matrix.

Thoma, Steven G. (Albuquerque, NM); Wilcoxon, Jess P. (Albuquerque, NM); Abrams, Billie L. (Albuquerque, NM)

2008-06-10

160

Silicon-based solar cell system with a hybrid PV module  

Microsoft Academic Search

Silicon-based solar cell technology has come into a stage where there is currently a big increase in its production and application. However, its installation on large scale is still obstructed due to its high installation cost. Here, we propose a silicon-based solar cell system for small PV energy systems. This system includes a hybrid solar cell module, which consists of

Linzhang Wu; Wei Tian; Xiaotao Jiang

2005-01-01

161

Microfabricated thermal modulator for comprehensive two-dimensional micro gas chromatography: design, thermal modeling, and preliminary testing.  

PubMed

In comprehensive two-dimensional gas chromatography (GC x GC), a modulator is placed at the juncture between two separation columns to focus and re-inject eluting mixture components, thereby enhancing the resolution and the selectivity of analytes. As part of an effort to develop a microGC x microGC prototype, in this report we present the design, fabrication, thermal operation, and initial testing of a two-stage microscale thermal modulator (microTM). The microTM contains two sequential serpentine Pyrex-on-Si microchannels (stages) that cryogenically trap analytes eluting from the first-dimension column and thermally inject them into the second-dimension column in a rapid, programmable manner. For each modulation cycle (typically 5 s for cooling with refrigeration work of 200 J and 100 ms for heating at 10 W), the microTM is kept approximately at -50 degrees C by a solid-state thermoelectric cooling unit placed within a few tens of micrometres of the device, and heated to 250 degrees C at 2800 degrees C s(-1) by integrated resistive microheaters and then cooled back to -50 degrees C at 250 degrees C s(-1). Thermal crosstalk between the two stages is less than 9%. A lumped heat transfer model is used to analyze the device design with respect to the rates of heating and cooling, power dissipation, and inter-stage thermal crosstalk as a function of Pyrex-membrane thickness, air-gap depth, and stage separation distance. Experimental results are in agreement with trends predicted by the model. Preliminary tests using a conventional capillary column interfaced to the microTM demonstrate the capability for enhanced sensitivity and resolution as well as the modulation of a mixture of alkanes. PMID:20556268

Kim, Sung-Jin; Reidy, Shaelah M; Block, Bruce P; Wise, Kensall D; Zellers, Edward T; Kurabayashi, Katsuo

2010-07-01

162

Fabrication of plastic microlens array using gas-assisted micro-hot-embossing with a silicon mold  

NASA Astrophysics Data System (ADS)

This paper reports an innovative method for fabrication of plastic microlens arrays. By using gas pressure to press the plastic film onto silicon mold of holes array, microlens array can be directly fabricated. A machine with closed chamber for gas-assisted micro-hot-embossing was constructed and tested. The 300 × 300 plastic microlens array with a diameter of 150 ?m and a pitch of 200 ?m were successfully produced. Under the condition of 150 °C, 10-40 kgf/cm 2 gas pressure and 30-90 s duration, the microlens with uniform and strong focusing function were formed on the polycarbonate film. The shape and height of microlens can be changed by adjusting the processing temperature, pressure and duration. This technique shows great potential for fabricating microlens array on large plastic films with high productivity and low cost.

Chang, C.-Y.; Yang, S.-Y.; Huang, L.-S.; Chang, J.-H.

2006-06-01

163

Root canal hydrophobization by dentinal silanization: improvement of silicon-based endodontic treatment tightness.  

PubMed

A new strategy to improve silicon-based endodontic treatment tightness by dentine hydrophobization is presented in this work: root dentine was silanized to obtain a hydrophobic dentine-sealer interface that limits fluid penetration. This strategy was based on the grafting of aliphatic carbon chains on the dentine through a silanization with the silane end groups [octadecyltrichlorosilane (OTS) and octadecyltriethoxysilane]. Dentine surface was previously pretreated, applying ethylenediaminetetraacetic acid and sodium hypochlorite, to expose hydroxyl groups of collagen for the silane grafting. Collagen fibers exposure after pretreatment was visible with scanning electron microscopy, and Fourier transform infrared (FTIR) spectroscopy showed their correct exposition for the silanization (amide I and II, with 1630, 1580, and 1538 cm?¹ peaks corresponding to the vibration of C=O and C--N bonds). The grafting of aliphatic carbon chains was confirmed by FTIR (peaks at 2952 and 2923 cm?¹ corresponding to the stretching of C--H bonds) and by the increasing of the water contact angle. The most efficient hydrophobization was obtained with OTS in ethyl acetate, with a water contact angle turning from 51° to 109°. Gas and liquid permeability tests showed an increased seal tightness after silanization: the mean gas and water flows dropped from 2.02 × 10?? to 1.62 × 10?? mol s?¹ and from 10.8 × 10?³ to 5.4 × 10?³ µL min?¹, respectively. These results show clear evidences to turn hydrophilic dentine surface into a hydrophobic surface that may improve endodontic sealing. PMID:23359546

Collart Dutilleul, Pierre-Yves; Fonseca, Cesar Gaitán; Zimányi, László; Romieu, Olivier; Pozos-Guillén, Amaury J; Semetey, Vincent; Cuisinier, Frédéric; Pérez, Elías; Levallois, Bernard

2013-07-01

164

Current-day employment of the micro-bore open-tubular capillary column in the gas chromatography field.  

PubMed

The present contribution is focused on the exploitation of the micro-bore (MB) open-tubular column (ID?0.18 mm), in current-day gas chromatography. The vast majority of GC methods involve the use of MB columns, from a variety of one-dimensional techniques (conventional and high speed), to different forms of heart-cutting and comprehensive multidimensional methodologies. Various aspects related to the use of MB open-tubular capillaries will be described and critically discussed, along with a series of pertinent applications. A series of works from the past have also been cited, essentially because many approaches today-applied, derive from the ideas of the past. Obviously, the present contribution does not review the entire history of the micro-bore capillary (more than one book would be necessary); rather, it intends to portray the great contribution that such analytical tools provide in enhancing two fundamental GC features, namely separation power and speed. PMID:22749360

Tranchida, Peter Quinto; Mondello, Luigi

2012-10-26

165

A beam test of prototype time projection chamber using micro-pattern gas detectors at KEK  

NASA Astrophysics Data System (ADS)

We conducted a series of beam tests of prototype TPCs for the international linear collider (ILC) experiment, equipped with an MWPC, a MicroMEGAS, or GEMs as a readout device. The prototype operated successfully in a test beam at KEK under an axial magnetic field of up to 1 T. The analysis of data is now in progress and some of the preliminary results obtained with GEMs and MicroMEGAS are presented along with our interpretation. Also given is the extrapolation of the obtained spatial resolution to that of a large TPC expected as the central tracker of the ILC experiment.

Kobayashi, Makoto

2007-12-01

166

Fabrication of micro/nano-structures using focused ion beam implantation and XeF2 gas-assisted etching  

NASA Astrophysics Data System (ADS)

A micro/nano-structure fabrication method is developed using focused ion beam implantation (FIBI) and FIB XeF2 gas-assisted etching (FIB-GAE). Firstly, the FIB parameters' influence on the FIBI depth is studied by SEM observation of the FIBI cross-section cutting by FIB. Nanoparticles with 10-15 nm diameter are found to be evenly distributed in the FIBI layer, which can serve as a XeF2-assisted etching mask when the ion dose is larger than 1.4 × 1017 ions cm-2. The FIBI layers being used as the etching mask for the subsequent FIB-GAE process are explored to create different micro/nano-structures such as nano-gratings, nano-electrode and sinusoidal microstructures. It is found that the method of combining FIBI with subsequent FIB-GAE is efficient and flexible in micro/nano-structuring, and it can effectively remove the redeposition effect compared with the FIB milling method.

Xu, Z. W.; Fang, F. Z.; Fu, Y. Q.; Zhang, S. J.; Han, T.; Li, J. M.

2009-05-01

167

Micro-fabricated semi-packed column for gas chromatography by using functionalized parylene as a stationary phase  

NASA Astrophysics Data System (ADS)

The conformal coating of effective stationary phases onto micro-fabricated columns having complex geometries such as semi-packed columns poses a real challenge. Here, we report for the first time the conformal coating of a semi-packed column with amino-functionalized parylene diX-AM (poly-aminomethyl-[2,2]-paracyclophane), which was found to be an effective stationary-phase material for the chromatography of short-retention-time compounds. A semi-packed column (consisting of a zigzag array of 30 µm square micro-pillars in a 1.0 m long, 180 µm wide and 230 µm deep channel) and an open tubular column (1.0 m long, 160 µm wide and 230 µm deep channel) used for comparison purposes were micro-fabricated on silicon that was subsequently coated with diX-AM parylene and thermally bonded. The chromatograms recorded on a commercial gas chromatograph demonstrated the usefulness of the conformal diX-AM coating as a stationary phase for semi-packed columns. The separation efficiency of the semi-packed column was found to be more than ten times that of the open tubular column.

Nakai, T.; Nishiyama, S.; Shuzo, M.; Delaunay, J.-J.; Yamada, I.

2009-06-01

168

Silicon based affinity biochips viewed with imaging ellipsometry  

NASA Astrophysics Data System (ADS)

In this paper we report on the fabrication of an affinity biochip with a matrix of 900 targets for detection with imaging ellipsometry. Two methods of fabrication of chips are shown: one based on wet etching of a silicon surface and the other on the preparation of so-called tension wells on the silicon surface. The dispensing of reagents and ligands was performed using a pipetting robot equipped with a micro-capillary, a syringe pump and micro-stepping motors. Measurements were performed on the chips in real time with carbohydrate model substances selected for six common lectins. Affinity binding was shown for three of the tested model substances.

van Noort, Danny; Rumberg, Jens; Jager, Edwin W. H.; Mandenius, Carl-Fredrik

2000-06-01

169

MEMS silicon-based resistojet micro-thruster for attitude control of nano-satellites  

Microsoft Academic Search

This paper presents a miniaturized resistojet thruster device with an integrated thin-film heater, capable of delivering thrusts in the micronewton–millinewton range. Its small size (25 mm × 5 mm × 1 mm), low mass (162 mg), low power and propellant consumption make it very attractive for attitude control of nano-satellites (mass 1-10 kg). Based on the pressure measurements with the

M. Mihailovic; T. V. Mathew; J. F. Creemer; B. T. C. Zandbergen; P. M. Sarro

2011-01-01

170

Micro-fabricated membrane gas valves with a non-stiction coating deposited by C4F8/Ar plasma  

NASA Astrophysics Data System (ADS)

Micro-fabricated gas valves with C4F8/Ar treatment at the sealing interface are designed, fabricated and characterized to passively control gases in a micro gas analysis system. The check valves form a seal between a polished Si/SiO2 substrate and a smooth polyimide (PI) membrane. The smooth PI membrane touches the SiO2 surface, giving rise to relatively strong van der Waals adhesion, and under humid conditions hydrogen-bonded stiction can occur at the interface between PI and SiO2. To prevent stiction from dominating adhesion, the valve-seat surface was treated with a hydrophobic CFn thin film, which was formed by exposing the surface to C4F8/Ar inductively coupled plasma (ICP) at low power. The valves without a non-stiction coating did not open with inlet pressures up to 210 kPa. With a non-stiction coating, the valves showed an average initial opening pressure of 59.25 kPa. In order to further reduce the opening pressure, 40% of the valve-seat area is reduced. After modification, the average opening pressure is reduced to 32.5 kPa. After the initial opening, the average in-use opening pressure was 16.9 kPa before area modification, and 13.1 kPa after the modification. The valve has been tested up to 10 000 open/close cycles under dry N2 gas flow, and an additional 3000 open/close cycles under humid N2 gas flow. The average forward flow conductance of the valves before modification was 1.1 sccm kPa-1, and the conductance after modification was 1.41 sccm kPa-1. The measured leakage is between 0.0003 and 0.004 sccm up to 35 kPa reverse pressure.

Han, Jeahyeong; Flachsbart, Bruce; Masel, Rich I.; Shannon, Mark A.

2008-09-01

171

Thermal analysis and design of a micro-hotplate for integrated gas-sensor applications  

Microsoft Academic Search

The application of commercial mechanical computer-aided engineering (MCAE) software to the design and analysis of micro-hotplate (MHP) structures is presented. The simulation provides an estimation of heating efficiency and temperature distribution on the hotplate. The analysis is applied to a newly proposed MHP structure during layout design. Novel design results in a hotplate with high heating efficiency, good temperature uniformity

Samuel K. H Fung; Zhenan Tang; Philip C. H Chan; Johnny K. O Sin; Peter W Cheung

1996-01-01

172

Higher stability of silicon-based thin-film solar cell fabricated by LAPECVD  

Microsoft Academic Search

Silicon-based thin-film solar cells were deposited using novel designed LAPECVD system. The conversion efficiency degradation of the Staebler-Wronski Effect (SWE) was effectively improved due to the microcrystalline structure and the lower hydrogen bonds concentration.

Chih-Hsiang Chang; Ching-Ting Lee

2011-01-01

173

Silicon nanoporous pillar array: template for fabricating silicon-based nanocomposites with enhanced physical properties  

NASA Astrophysics Data System (ADS)

A triple hierarchical structure, silicon nanoporous pillar array (Si-NPA), was formed on silicon wafers by a hydrothermal method. The structure of Si-NPA is characterized by the regular array of micron-sized silicon pillars, quasi-identical nanopores densely distributing over each pillar, and silicon nanocrystalllites composing the walls of the nanopores. Utilizing the excellent structural regularity and high chemical reactivity of Si-NPA, patterned nanocomposites of CdS, carbon nanotubes (CNTs), Au, and Fe3O4/Si-NPA were fabricated. Their element compositions, morphologies and microstructures were characterized. Ideal physical properties of I-V curve in CdS/Si-NPA heterojunction, field emission in Si-NPA, CNTs/Si- NPA, Au/Si-NPA, and humidity/gas sensitivity in Fe3O4/Si-NPA were observed and the corresponding mechanisms were analyzed. These results indicate that Si-NPA could be employed as an ideal template to assembly silicon-based functional nanosystems, and might find multiple applications in fabricating novel electronic devices.

Li, Xin Jian; Fu, Xiao Nan; Xu, Hai Jun; Jiang, Wei Feng

2006-03-01

174

Silicon nanoporous pillar array: template for fabricating silicon-based nanocomposites with enhanced physical properties  

NASA Astrophysics Data System (ADS)

A triple hierarchical structure, silicon nanoporous pillar array (Si-NPA), was formed on silicon wafers by a hydrothermal method. The structure of Si-NPA is characterized by the regular array of micron-sized silicon pillars, quasi-identical nanopores densely distributing over each pillar, and silicon nanocrystalllites composing the walls of the nanopores. Utilizing the excellent structural regularity and high chemical reactivity of Si-NPA, patterned nanocomposites of CdS, carbon nanotubes (CNTs), Au, and Fe3O4/Si-NPA were fabricated. Their elemental compositions, morphologies and microstructures were characterized. Ideal physical properties of I-V curve in CdS/Si-NPA heterojunction, field emission in Si-NPA, CNTs/Si-NPA, Au/Si-NPA, and humidity/gas sensitivity in Fe3O4/Si-NPA were observed and the corresponding mechanisms were analyzed. These results indicate that Si-NPA could be employed as an ideal template to assembly silicon-based functional nanosystems, and might find multiple applications in fabricating novel electronic devices.

Li, Xin Jian; Fu, Xiao Nan; Xu, Hai Jun; Jiang, Wei Fen

2007-03-01

175

Improved gas chromatography methods for micro-volume analysis of haloacetic acids in water and biological matrices.  

PubMed

A fast headspace solid-phase microextraction gas chromatography method for micro-volume (0.1 mL) samples was optimized for the analysis of haloacetic acids (HAAs) in aqueous and biological samples. It includes liquid-liquid microextraction (LLME), derivatization of the acids to their methyl esters using sulfuric acid and methanol after evaporation, followed by headspace solid-phase microextraction with gas chromatography and electron capture detection (SPME-GC-ECD). The derivatization procedure was optimized to achieve maximum sensitivity using the following conditions: esterification for 20 min at 80 degrees C in 10 microL methanol, 10 microL sulfuric acid and 0.1 g anhydrous sodium sulfate. Multi-point standard addition method was used to determine the effect of the sample matrix by comparing with internal standard method. It was shown that the effect of the matrix for urine and blood samples in this method is insignificant. The method detection limits are in the range of 1 microg L(-1) for most of the HAAs, except for monobromoacetic acid (MBAA) (3 microg L(-1)) and for monochloroacetic acid (MCAA) (16 microg L(-1)). The optimized procedure was applied to the analysis of HAAs in water, urine and blood samples. All nine HAAs can be separated in < 13 min for biological samples and < 7 min for drinking water samples, with total sample preparation and analysis time < 50 min. Analytical uncertainty can increase dramatically as the sample volume decreases; however, similar precision was observed with our method using 0.1 mL samples as with a standard method using 40 mL samples. PMID:12430602

Wu, Fengwu; Gabryelski, Wojciech; Froese, Kenneth

2002-10-01

176

Recent Research on One-Dimensional Silicon-Based Semiconductor Nanomaterials: Synthesis, Structures, Properties and Applications  

Microsoft Academic Search

The field of silicon nanowires (SiNWs) and silicon-based 1D nanostructured heterostructures represent one of the most important research subjects within the nanomaterials family. A series of synthesis approaches of SiNWs and silicon-based 1D nanostructured heterostructures have been developed, and have garnered the greatest attention in the past decades for a variety of applications. This article provides an overview on recent

Zhenyu Zhang; Rujia Zou; Li Yu; Junqing Hu

2011-01-01

177

Next Generation Silicon Based Detector Characterization in the LASI Lab at Arizona State University  

Microsoft Academic Search

We present preliminary results of comprehensive characterization we performed on a Cassini flight spare 1024 x 1024 silicon based CCD, to ensure that our methods are accurate, and a 1024 x 1024 NIR\\/Red optimized delta-doped, anti-reflection coated silicon based CCD provided by the Nanoscience and Advanced Detector Arrays Group at JPL. We also present here a new facility for CCD

Todd Veach; P. Scowen; S. Nikzad

2007-01-01

178

Photocatalytic oxidation of aqueous trichloroethylene using dye sensitized buoyant photocatalyst monitored via micro-headspace solid-phase microextration gas chromatography\\/electron capture detection and mass spectrometry  

Microsoft Academic Search

Trichloroethylene (TCE), a useful industrial agent which unfortunately exhibits carcinogenic properties, has become an extremely prevalent environmental contaminant. As such, new rapid, sensitive, and cost effective detection methods are needed for the identification of potential point sources of contamination. A new analytic micro-headspace method is described, utilizing solid phase micro-extraction (SPME) fibers and routine gas chromatography\\/electron capture detection (GC\\/ECD) for

Matt V. Alexander; Jeffrey J. Rosentreter

2008-01-01

179

Rapid tandem-column micro-gas chromatography based on optofluidic ring resonators with multi-point on-column detection  

Microsoft Academic Search

We demonstrated a novel tandem-column micro-gas chromatography (mGC) based on optofluidic ring resonator (OFRR). The OFRR is a thin-walled fused silica capillary whose interior surface is coated with a polymeric stationary phase. The circular cross section of the OFRR forms the micro-ring resonator and supports whispering gallery modes (WGMs). Via tapered optical fibers in contact with the OFRR, the WGM

Yuze Sun; Jing Liu; Daniel J. Howard; Greg Frye-Mason; Aaron K. Thompson; Shiou-Jyh Ja; Xudong Fan

2010-01-01

180

Efficient and scalable single mode waveguide coupling on silicon based substrates  

NASA Astrophysics Data System (ADS)

One of the key challenges in Silicon based optical interconnect system remains to be the efficient coupling of optical signals from the submicron size on-chip waveguides to standard single mode (SM) fibers with low insertion loss (IL) and relaxed alignment tolerance. Large optical alignment tolerance allows optical connectors to be attached to on-chip waveguides passively using standard semiconductor pick-and-place assembly tools that have placement accuracies of 10- 15?m. To facilitate the assembly, optical fiber coupling elements need to be modular and compact. They have to also have low profile to avoid blocking air flow or mechanical interference with other elements of the package. In this paper we report the development of a two-dimensional (2D) SM optical fiber coupling architecture that consists of Si based photonic lightwave circuit (PLC) substrate and a high-density micro-lensed fiber optic connector. The system is compact, efficient and has large optical alignment tolerance. At 1300nm an insertion loss of 2.4dB and 1.5dB was measured for the PLC module and the fiber optic connector, respectively. When the PLC module and connector was aligned together, a total insertion loss of 7.8dB was demonstrated with x,y alignment tolerance of 40?m for 1dB optical loss. The SM optical coupling architecture presented here is scalable, alignment tolerant and has the potential to be manufactured in high volume. To our knowledge, such a system has not been reported in the literature so far.

Mohammed, E.; Tseng, R.; Rawlings, B.; Liff, S.; Ban, I.; McFarlane, W.; Reshotko, M.; Chang, P.

2014-03-01

181

Batch Assembly Micro-Ball Lens Array for Si-Based Optical Coupling Platform in Free Space  

Microsoft Academic Search

The paper presents novel concepts of batch fabrication of micro-ball lens array technology integrated on the silicon-based wafer which can improve the appropriate distance for optical fiber coupling. The silicon-based optical coupling platform consists of a self-parking framework (including flat-topped mesa and intersection of two v-grooves) and micro-ball lens array for optical fiber coupling purposes. The structure of optical coupling

Sheng-Chih Shen; Cheng-Tang Pan; Hwai-Pwu Chou; Min-Chieh Chou; Kun L. Lin; Yang Jauh Jung

2001-01-01

182

Recent Progress in Silicon-Based MEMS Field Emission Thrusters  

NASA Astrophysics Data System (ADS)

The Indium Field Emission Thruster (In-FET) is a highly characterized and space-proven device based on space-qualified liquid metal ion sources. There is also extensive experience with liquid metal ion sources for high-brightness semiconductor fabrications and inspection Like gridded ion engines, In-FETs efficiently accelerate ions through a series of high voltage electrodes. Instead of a plasma discharge to generate ions, which generates a mixture of singly and doubly charged ions as well as neutrals, indium metal is melted (157°C) and fed to the tip of a capillary tube where very high local electric fields perform more-efficient field emission ionization, providing nearly 100% singly charged species. In-FETs do not have the associated losses or lifetime concerns of a magnetically confined discharge and hollow cathode in ion thrusters. For In-FETs, propellant efficiencies ~100% stipulate single-emitter currents <=10?A, perhaps as low as 5?A of current. This low emitter current results in <=0.5 W/emitter. Consequently, if the In-FET is to be used for future Human and Robotic missions under President Bush's Exploration plan, a mechanism to generate very high power levels is necessary. Efficient high-power operation requires many emitter/extractor pairs. Conventional fabrication techniques allow 1-10 emitters in a single module, with pain-staking precision required. Properly designed and fabricated In-FETs possess electric-to-jet efficiency >90% and a specific mass <0.25 kg/kWe. MEMS techniques allow reliable batch processing with ~160,000 emitters in a 10×10-cm array. Developing a 1.5kW 10×10-cm module is a necessary stepping-stone for >500 kWe systems where groups of 9 or 16 modules, with a single PPU/feed system, form the building blocks for even higher-power exploration systems. In 2003, SNL and ARCS produced a MEMS-based In-FET 5×5 emitter module with individually addressable emitter/extractor pairs on a 15×15mm wafer. The first MEMS thruster prototype has already been tested to demonstrate the proof-of-concept in laboratory-scale testing. In this paper we discuss progress that has been achieved in the past year on fabricating silicon-based MEMS In-FETs.

Lenard, Roger X.; Kravitz, Stanley H.; Tajmar, Martin

2005-02-01

183

Surface tension effects on adiabatic gas–liquid flow across micro pillars  

Microsoft Academic Search

The effect of surface tension on adiabatic two-phase flow across a bank of 100?m diameter staggered circular micro pillars, 100?m long with pitch-to-diameter ratio of 1.5, for Reynolds number between 5 and 50, was investigated. Experiments with ethanol were performed and compared to results with water. Flow maps revealed similar flow patterns, but the transition lines were different for the

Santosh Krishnamurthy; Yoav Peles

2009-01-01

184

Variations in gas properties in laminar micro-convection with entrance effect  

Microsoft Academic Search

The present work investigates the influence of property variations of air in laminar forced convection with entrance effect. Two-dimensional micro-sized geometry (with axisymmetry) with constant wall heat flux boundary condition is considered to predict flow behaviour and thermal development. The continnum-based conservation equations are numerically solved to account for non-rarefaction scaling effects due to variations in fluid properties. At the

Nitin P. Gulhane; Shripad P. Mahulikar

2009-01-01

185

50 nm thick AlN resonant micro-cantilever for gas sensing application  

Microsoft Academic Search

We present the fabrication and characterization of a 90?m × 40?m × 885nm piezoelectric micro-cantilever resonator containing a 50nm thick Aluminum Nitride (AlN) piezoelectric film for transduction. Material characterizations demonstrate that our AlN deposition technique enables the fabrication of ultra-thin films with high piezoelectric coefficient e31 = 0.78C.m-2. Fully electrical actuation and detection of the cantilever resonance behavior is evidenced

P. Ivaldi; J. Abergel; G. Arndt; P. Robert; P. Andreucci; H. Blanc; S. Hentz; E. Defay

2010-01-01

186

Nanoparticle metal-oxide films for micro-hotplate-based gas sensor systems  

Microsoft Academic Search

We report on the use of either reactive magnetron sputtering or screen printing to deposit tin and tungsten-oxide gas-sensitive layers onto integrated micromachined arrays. The procedures allow the deposition of the sensing layers before membranes have been etched, which leads to gas microsensors with an excellent fabrication yield. The microstructure of the sensitive films is analyzed by means of SEM

Peter Ivanov; Mariana Stankova; Eduard Llobet; Xavier Vilanova; Jesús Brezmes; Isabel Gràcia; Carles Cané; Josep Calderer; Xavier Correig

2005-01-01

187

Nanostructure Engineered Chemical Sensors for Hazardous Gas and Vapor Detection.  

National Technical Information Service (NTIS)

A nanosensor technology has been developed using nanostructures, such as single walled carbon nanotubes (SWNTs) and metal oxides nanowires or nanobelts, on a pair of interdigitated electrodes (IDE) processed with a silicon based microfabrication and micro...

J. Li Y. Lu

2005-01-01

188

DETERMINATION OF CHLOROETHENES IN ENVIRONMENTAL BIOLOGICAL SAMPLES USING GAS CHROMATOGRAPHY COUPLED WITH SOLID PHASE MICRO EXTRACTION  

EPA Science Inventory

An analytical method has been developed to determine the chloroethene series, tetrachloroethene (PCE), trichloroethene (TCE),cisdichloroethene (cis-DCE) andtransdichloroethene (trans-DCE) in environmental biotreatment studies using gas chromatography coupled with a solid phase mi...

189

Optimum Operation Condition on Distributed Power Supply System with Micro Gas Turbine/Solid Oxide Fuel Cell  

NASA Astrophysics Data System (ADS)

In order to find the optimum operation condition of a distributed power supply system of 30kW class micro gas turbine (MGT) and solid oxide fuel cell (SOFC) hybrid system with the combination of line electric power and supplied gas, a system analysis has been performed. In this study, an absorption chiller and a boiler were mounted to utilize the exhausted heat from the MGT/SOFC system. The time variation of energy consumption in 24 hours for house and market models was taken into consideration for the calculation of the energy saving ratio of the present system. The operation ratio defined with the ratio of power supply of MGT/SOFC system to the power required at the peak load was changed as a parameter. From the comparison with the system using line power and gas, it is found that the present system shows high energy saving ratio around 0.4 of the operation ratio, but the energy saving ratio severely decreases in the range of high operation ratio. In this study, it is revealed that the thermal storage system effectively improves the energy saving ratio especially for the house model in winter season.

Suzuki, Hiroshi; Yamada, Miki; Usui, Hiromoto; Komoda, Yoshiyuki

190

Remote-Raman and Micro-Raman Studies of Solid CO2, CH4, Gas Hydrates and Ice  

NASA Technical Reports Server (NTRS)

It is well known that on Mars CO2 is the principal constituent of the thin atmosphere and on a seasonal basis CO2 snow and frost coats the polar caps. Also over 25% of the Martian atmosphere freezes out and sublimes again each year. The Mars Odyssey Emission Imaging system (THEMIS) has discovered water ice exposed near the edge of Mars southern perennials cap. In recent years, it has been suggested that in Martian subsurface CO2 may exist as gas hydrate (8CO2 + 44 H2O) with melting temperature of 10C. Since the crust of Mars has been stable for enough time there is also a possibility that methane formed by magmatic processes and/or as a byproduct of anaerobic deep biosphere activity to have raised toward the planet s surface. This methane would have been captured and stored as methane hydrate, which concentrates methane and water. Determination of abundance and distribution of these ices on the surface and in the near surface are of fundamental importance for understanding Martian atmosphere, and for future exploration of Mars. In this work, we have evaluated feasibility of using remote Raman and micro-Raman spectroscopy as potential nondestructive and non-contact techniques for detecting solid CO2, CH4 gas, and gas hydrates as well as water-ice on planetary surfaces.

Sharma, S. K.; Misra, A. K.; Lucey, P. G.; Exarhos, G. J.; Windisch, C. F., Jr.

2004-01-01

191

Gas Sensing Character of Polyaniline with Micro-/Nano-Fiber Network Structure  

NASA Astrophysics Data System (ADS)

By directly chemical oxidative polymerization of aniline on Au electrode treated with Au nanoparticles (Au-NPs) deposition and 4-aminothiophenol (ATP) modification, polyaniline (PANI) fibers were obtained in-situ in micro-/nano- size with two dimensional network structures. It was found that the ATP modification played an important role for the formation of fibrous network and in the decrease in the contact resistance between the PANI film and the electrode surface. The PANI film showed a rapid response upon the exposure to various gases with low detection limit, which indicated that the developed PANI sensor could be applied in the high sensitive detection of hazardous gases.

Liu, Chuanjun; Hayashi, Kenshi; Toko, Kiyoshi

2009-05-01

192

Theoretical tools for predicting optimal cross-sectional shapes in micro-gas chromatography.  

PubMed

It is meaningful to explore the possibility of improving the micro-GC column performance by adjusting the column cross-sectional shape. The objective of this study was to seek the column cross-sectional shape that results in larger plate number per meter than other shapes with the same cross-sectional area and the same flow resistance coefficient. We applied a model based on the volume averaging method to derive the expression of plate height for columns with arbitrary cross-sectional shapes, and conducted the shape optimization by combining the model and an optimization tool. By varying flow resistance coefficient, we obtained a series of optimal shapes. It is found that, the optimal shape with larger flow resistance coefficient is shallower and the related plate number per meter is larger. We predicted and optimized the performance of a micro-GC column reported in literature. The prediction agrees reasonably with experimental data. More than twice the plate number per meter of the original column was predicted by using a hypothetical column with one optimal cross-sectional shape. PMID:23436398

Yan, Xiaohong; Yang, Jian; Wang, Qiuwang; Liu, Yongzhong

2013-05-01

193

GEANT4 Simulation of a Cosmic Ray Muon Tomography System With Micro-Pattern Gas Detectors for the Detection of High Materials  

Microsoft Academic Search

Muon tomography (MT) based on the measurement of multiple scattering of atmospheric cosmic ray muons traversing shipping containers is a promising candidate for identifying threatening high-Z materials. Since position-sensitive detectors with high spatial resolution should be particularly suited for tracking muons in a MT application, we propose to use compact micro-pattern gas detectors, such as gas electron multipliers (GEMs), for

Marcus Hohlmann; Patrick Ford; Kondo Gnanvo; Jennifer Helsby; David Pena; Richard Hoch; Debasis Mitra

2009-01-01

194

Solidphase micro-extraction–gas chromatography–(tandem) mass spectrometry as a tool for pesticide residue analysis in water samples at high sensitivity and selectivity with confirmation capabilities  

Microsoft Academic Search

Gas chromatography–mass spectrometry (GC–MS) has been widely applied for pesticide monitoring because of its high sensitivity and specificity and for the potential of multi-residue and multi-class analysis. An analytical procedure was developed for the determination of pesticide multi-residues in water samples combining solid-phase micro-extraction (SPME) and gas chromatography–ion trap mass spectrometry. For SPME extraction a poly(dimethylsiloxane)–divinylbenzene coated fibre was selected

C Gonçalves; M. F Alpendurada

2004-01-01

195

Simultaneous micro steam distillation\\/solvent extraction for the isolation of semivolatile flavor compounds from cinnamon and their separation by series coupled-column gas chromatography  

Microsoft Academic Search

Simultaneous micro steam distillation\\/solvent extraction is an efficient method of extracting semivolatile flavor and fragrance compounds from cinnamon for subsequent separation by series coupled-column gas chromatography. With pentane as the extraction solvent and an extraction time of 1.5 h clean extracts requiring no further sample preparation prior to gas Chromatographic analysis are obtained. It is shown that adulteration of cinnamon

Arya Jayatilaka; Salwa K. Poole; Colin F. Poole; Tina M. P. Chichila

1995-01-01

196

A multi-phase, micro-dispersion reactor for the continuous production of methane gas hydrate  

SciTech Connect

A continuous-jet hydrate reactor originally developed to generate a CO2 hydrate stream has been modified to continuously produce CH4 hydrate. The reactor has been tested in the Seafloor Process Simulator (SPS), a 72-L pressure vessel available at Oak Ridge National Laboratory. During experiments, the reactor was submerged in water inside the SPS and received water from the surrounding through a submersible pump and CH4 externally through a gas booster pump. Thermodynamic conditions in the hydrate stability regime were employed in the experiments. The reactor produced a continuous stream of CH4 hydrate, and based on pressure values and amount of gas injected, the conversion of gas to hydrate was estimated. A conversion of up to 70% was achieved using this reactor.

Taboada Serrano, Patricia L [ORNL; Ulrich, Shannon M [ORNL; Szymcek, Phillip [ORNL; McCallum, Scott [Oak Ridge Associated Universities (ORAU); Phelps, Tommy Joe [ORNL; Palumbo, Anthony Vito [ORNL; Tsouris, Costas [ORNL

2009-01-01

197

Smart multi-channel two-dimensional micro-gas chromatography for rapid workplace hazardous volatile organic compounds measurement.  

PubMed

We developed a novel smart multi-channel two-dimensional (2-D) micro-gas chromatography (?GC) architecture that shows promise to significantly improve 2-D ?GC performance. In the smart ?GC design, a non-destructive on-column gas detector and a flow routing system are installed between the first dimensional separation column and multiple second dimensional separation columns. The effluent from the first dimensional column is monitored in real-time and decision is then made to route the effluent to one of the second dimensional columns for further separation. As compared to the conventional 2-D ?GC, the greatest benefit of the smart multi-channel 2-D ?GC architecture is the enhanced separation capability of the second dimensional column and hence the overall 2-D GC performance. All the second dimensional columns are independent of each other, and their coating, length, flow rate and temperature can be customized for best separation results. In particular, there is no more constraint on the upper limit of the second dimensional column length and separation time in our architecture. Such flexibility is critical when long second dimensional separation is needed for optimal gas analysis. In addition, the smart ?GC is advantageous in terms of elimination of the power intensive thermal modulator, higher peak amplitude enhancement, simplified 2-D chromatogram re-construction and potential scalability to higher dimensional separation. In this paper, we first constructed a complete smart 1 × 2 channel 2-D ?GC system, along with an algorithm for automated control/operation of the system. We then characterized and optimized this ?GC system, and finally employed it in two important applications that highlight its uniqueness and advantages, i.e., analysis of 31 workplace hazardous volatile organic compounds, and rapid detection and identification of target gas analytes from interference background. PMID:23303462

Liu, Jing; Seo, Jung Hwan; Li, Yubo; Chen, Di; Kurabayashi, Katsuo; Fan, Xudong

2013-03-01

198

Determination of benzodiazepines in human urine and plasma with solvent modified solid phase micro extraction and gas chromatography; rationalisation of method development using experimental design strategies  

Microsoft Academic Search

Solid phase micro extraction (SPME) and gas chromatographic analysis was used for the analysis of several benzodiazepines (oxazepam, diazepam, nordiazepam, flunitrazepam and alprazolam) in human urine and plasma. Several factors likely to affect the analyte recovery were screened in a fractional factorial design in order to examine their effect on the extraction recovery. Parameters found significant in the screening were

Karianne Johansen Reubsaet; Hans Ragnar Norli; Peter Hemmersbach; Knut E Rasmussen

1998-01-01

199

Gas flows in rectangular microchannels and a capacitive micro flow sensor using differential pressure  

Microsoft Academic Search

Flows often behave differently at small length scales than macroscopic intuition. These behavior changes can have serious implications for microfluidic devices. In gas flows, these differences are rarefaction and compressibility, among others. The goal of this thesis is to derive the theoretical mass flow rate and pressure distribution in rectangular microchannels considering those differences. These results are applied to designing

Jaesung Jang

2004-01-01

200

MACRO- MICRO-PURGE SOIL GAS SAMPLING METHODS FOR THE COLLECTION OF CONTAMINANT VAPORS  

EPA Science Inventory

Purging influence on soil gas concentrations for volatile organic compounds (VOCs), as affected by sampling tube inner diameter and sampling depth (i.e., dead-space purge volume), was evaluated at different field sites. A macro-purge sampling system consisted of a standard hollo...

201

Modeling Transport in Gas Chromatography Columns for the Micro-ChemLab.  

National Technical Information Service (NTIS)

The gas chromatography (GC) column is a critical component in the microsystem for chemical detection (pChemLabTM) being developed at Sandia. The goal is to etch a 'meter-long' GC column onto a l-cm2 silicon chip while maintaining good chromatographic perf...

Adkins Frye-Mason Hudson Kottenstette Matzke

1999-01-01

202

Compatibility of RPECVD silicon dioxide with depletion gate materials for silicon-based nanostructures  

NASA Astrophysics Data System (ADS)

The focus of this work has been upon deposited oxide and gate materials suitable for use in silicon-based nanostructures. The latter use e-beam patterned depletion gates in order to create three-dimensional confinement of electrons in the 2-dimensional electron gas of a metal-oxide-semiconductor field effect transistor (MOSFET) inversion layer. Remote Plasma Enhanced chemical Vapor Deposition (RPECVD) silicon dioxide was selected as the deposited oxide. The deposition process was optimized using statistical techniques. Typically, low temperature deposited oxide is annealed in order to achieve device quality. The behavior of the oxide as a function of deposition and annealing temperature was characterized in order to understand the advantages of the anneal and the thermal budget required to accomplish the objectives of the MOSFET gate oxide quality oxide. Bulk oxide was assessed using etch rates in HF containing solutions, infrared absorption data, refractive index, and AFM measurements of surface roughness. The interface quality was examined using C-V measurements. Breakdown measurements were performed. The impact of the oxide deposition process on a thermally established Si/SiOsb2 interface was explored. Three materials were investigated for the role of depletion gates that might tolerate a high temperature aneal: cobalt silicide, cobalt and chrome. Their thermal stability was tested, sandwiched between a thermal oxide and a deposited oxide, for annealing temperatures of 700, 800 and 900 C by Auger electron spectroscopy and cross-sectional transmission electron spectroscopy. The impact of the oxide deposition process on the depletion gates was significant and so this has been studied as well.

Rack, Mary Jo

203

Development of High Precision Metal Micro-Electro-Mechanical-Systems Column for Portable Surface Acoustic Wave Gas Chromatograph  

NASA Astrophysics Data System (ADS)

In the field of environmental measurement and security, a portable gas chromatograph (GC) is required for the on-site analysis of multiple hazardous gases. Although the gas separation column has been downsized using micro-electro-mechanical-systems (MEMS) technology, an MEMS column made of silicon and glass still does not have sufficient robustness and a sufficiently low fabrication cost for a portable GC. In this study, we fabricated a robust and inexpensive high-precision metal MEMS column by combining diffusion-bonded etched stainless-steel plates with alignment evaluation using acoustic microscopy. The separation performance was evaluated using a desktop GC with a flame ionization detector and we achieved the high separation performance comparable to the best silicon MEMS column fabricated using a dynamic coating method. As an application, we fabricated a palm-size surface acoustic wave (SAW) GC combining this column with a ball SAW sensor and succeeded in separating and detecting a mixture of volatile organic compounds.

Iwaya, Takamitsu; Akao, Shingo; Sakamoto, Toshihiro; Tsuji, Toshihiro; Nakaso, Noritaka; Yamanaka, Kazushi

2012-07-01

204

Plane Poiseuille-Couette problem in micro-electro-mechanical systems applications with gas-rarefaction effects  

NASA Astrophysics Data System (ADS)

Rarefied gas flows in micro-electro-mechanical systems (MEMS) devices, calculated from the linearized Bhatnagar-Gross-Krook model equation [P. L. Bhatnagar, E. P. Gross, and M. Krook, Phys. Rev. 94, 511 (1954)], are studied in a wide range of Knudsen numbers. Both plane Poiseuille and Couette flows are investigated numerically by extending a finite difference technique first introduced by Cercignani and Daneri [J. Appl. Phys. 34, 3509 (1963)]. Moreover, a variational approach, applied to the integrodifferential form of the linearized Boltzmann equation [C. Cercignani, J. Stat. Phys. 1, 297 (1969)], is used to solve in a unified manner the plane Poiseuille-Couette problem by means of the computation of only one functional. General boundary conditions of Maxwell's type have been considered, assuming both symmetric and nonsymmetric molecular interaction between gas-solid interfaces, in order to take into account possible differences in the accommodation coefficients on the walls of MEMS devices. Based on the analysis presented in this paper, an accurate database valid in the entire Knudsen regime can be created for the Poiseuille-Couette problem, to be used in micromechanical applications.

Cercignani, Carlo; Lampis, Maria; Lorenzani, Silvia

2006-08-01

205

Investigation of Isotope Effects in the Gas Streams Supplied by a 1:1 ITER Storage Bed Using a Micro Gas Chromatography  

SciTech Connect

In the present design of the Storage and Delivery System of the ITER Tritium Plant deuterium, tritium and their mixtures are stored in hydrogen storage beds with a storage capacity of 100 g. During plasma operation it is required that deuterium-tritium gases with well defined ratios of D/T are supplied by the different hydrogen storage beds. Due to the isotope effects the composition of the hydrogen gas mixture supplied by the getter bed may be different from the one absorbed in the getter and may even change during unloading of the bed depending on the variation of the isotope effect with the actual amount of hydrogen isotopes stored in the bed.At the Forschungszentrum Karlsruhe a 1:1 prototype of ITER hydrogen storage bed with a capacity of 100 g tritium and a target supply rate of up to 200 Pam3s-1 was designed and manufactured. The getter bed is currently filled with zirconium-cobalt and is installed in an experimental rig coupled with a micro gas chromatograph in order to perform texts under different operation conditions and to characterize the possible isotope effects. In this work a first data on the isotope effect during loading and unloading of the getter bed with the different hydrogen-deuterium mixtures is presented.

Beloglazov, S.; Glugla, M.; Wagner, R.; Fanghaenel, E.; Gruenhagen, S. [Forschungszentrum Karlsruhe (Germany)

2005-07-15

206

A programmable palm-size gas analyzer for use in micro-autonomous systems  

NASA Astrophysics Data System (ADS)

Gas analysis systems having small size, low power, and high selectivity are badly needed for defense (detection of explosives and chemical warfare agents), homeland security, health care, and environmental applications. This paper presents a palm-size gas chromatography system having analysis times of 5-50sec, detection limits less than 1ppb, and an average power dissipation less than one watt. It uses no consumables. The three-chip fluidic system consists of a preconcentrator, a 25cm-3m separation column, and a chemi-resistive detector and is supported by a microcomputer and circuitry for programmable temperature control. The entire system, including the mini-pump and battery, occupies less than 200cc and is configured for use on autonomous robotic vehicles.

Gordenker, Robert J. M.; Wise, Kensall D.

2012-05-01

207

Micro and nanoscale non-ideal gas Poiseuille flows in a consistent Boltzmann algorithm model  

Microsoft Academic Search

The direct simulation Monte Carlo method in the consistent Boltzmann algorithm model has been developed and expanded for non-ideal gas predictions. The enhanced collision rate factor is determined by considering the excluded molecular volume and shadowing\\/screening effects based on the Enskog theory. The parameter for the attraction strength is also determined by comparison with the classical thermodynamics theory. Different pressure-driven

Moran Wang; Zhixin Li

2004-01-01

208

Morphology and structure of micro- and nanosize polytetrafluoroethylene powders prepared by the gas-phase method  

Microsoft Academic Search

Formation of fluoropolymer nanoaerosols and micropowders in the gas products of polytetrafluoroethylene pyrolysis and the\\u000a hierarchical self-organization of ultradispersed powders were revealed. The features of the molecular and supramolecular structures\\u000a of powders were analyzed. Low- and high-molecular-weight fractions of the fluoropolymers, constituting the powder particles\\u000a were identified, and a method for their partitioning was proposed.

V. M. Buznik; V. G. Kuryavyi

2009-01-01

209

Two-Port Static Coated Micro Gas Chromatography Column With an Embedded Thermal Conductivity Detector  

Microsoft Academic Search

This paper reports a microfabricated 2$\\\\,\\\\times\\\\,$4 cm gas chromatography chip to separate and detect gases in a two-port structure by embedding a microthermal conductivity detector $(\\\\mu{\\\\rm TCD})$ within a separation column. A circular on-chip heater is placed on the backside of the monolithic device enabling temperature programming and consequently faster analysis of the heavier components. A unique process enhanced by

Shree Narayanan; Bassam Alfeeli; Masoud Agah

2012-01-01

210

Micro-CT imaging of rat lung ventilation using continuous image acquisition during xenon gas contrast enhancement.  

PubMed

We measured ventilation (V) in seven anesthetized, mechanically ventilated, supine Wistar rats. Images of the whole lung were continuously acquired using a dynamic, flat-panel volumetric micro-computed tomography (micro-CT) scanner during ventilation with a xenon/oxygen (Xe-O(2)) gas mixture. Forty time-resolved volumes consisting of eighty 0.45-mm-thick slices (covering the entire lung) were acquired in 40 s, using a gantry rotation rate of one rotation per second. The animals were ventilated at a respiratory rate of 60 breaths/min, matching the gantry rotation rate, and imaged without suspending ventilation. A previously published theoretical model was modified slightly and used to calculate the whole lung ventilation from volumes of interest generated by seeded region growing. Linear regression of calculated whole lung ventilation volumes vs. expected tidal volumes yielded a slope of 1.12 +/- 0.11 (slope +/- SE) and a y-intercept of -1.56 +/- 0.42 ml (y-intercept +/- SE) with 95% confidence intervals of 0.83 to 1.40 and -2.6 to -0.5 ml, respectively. The same model was used to calculate the regional ventilation in axial slices for each animal. Voxels were fit to the model to yield a map of V, which displayed an anterior/posterior gravitational gradient of (-3.9 +/- 1.8) x 10(-6) mlxs(-1)xcm(-1) for slices immediately superior to the diaphragm and (-6.0 +/- 2.4) x 10(-6) mlxs(-1)xcm(-1) for slices at the midlevel of the heart (mean +/- SD). Thus continuous Xe-enhanced computed tomography enables the noninvasive determination of regional V with the temporal and spatial resolution necessary for rats. PMID:17690202

Lam, Wilfred W; Holdsworth, David W; Du, Louise Y; Drangova, Maria; McCormack, David G; Santyr, Giles E

2007-11-01

211

Influence of Surface Roughness on Micro-Scale Rarefied Gas Flows  

NASA Astrophysics Data System (ADS)

Efficient numerical methods are an important tool to study the interaction of rarefied gas flows with a rough surface. In earlier work, the near-free-molecular approach was applied to the study of external flows [1-8]. Here, we extend and adapt the computational methods in [1-8] for the case of internal flows in channels and nozzles. The transformation of the scattering function due to roughness is characterized by the roughness operator. We derive a representation of the roughness operator that is convenient to use both in numerical DSMC methods and in analytical investigations.

Aksenova, O. A.; Khalidov, L. A.

2008-12-01

212

Toward a Micro Gas Chromatograph/Mass Spectrometer (GC/MS) System  

NASA Technical Reports Server (NTRS)

Miniature mass filters (e.g., quadrupoles, ion traps) have been the subject of several miniaturization efforts. A project is currently in progress at JPL to develop a miniaturized Gas Chromatograph/Mass Spectrometer (GC/MS) system, incorporating and/or developing miniature system components including turbomolecular pumps, scroll type roughing pump, quadrupole mass filter, gas chromatograph, precision power supply and other electronic components. The preponderance of the system elements will be fabricated using microelectromechanical systems (MEMS) techniques. The quadrupole mass filter will be fabricated using an X-ray lithography technique producing high precision, 5x5 arrays of quadrupoles with pole lengths of about 3 mm and a total volume of 27 cubic mm. The miniature scroll pump will also be fabricated using X-ray lithography producing arrays of scroll stages about 3 mm in diameter. The target detection range for the mass spectrometer is 1 to 300 atomic mass units (AMU) with are solution of 0.5 AMU. This resolution will allow isotopic characterization for geochronology, atmospheric studies and other science efforts dependant on the understanding of isotope ratios of chemical species. This paper will discuss the design approach, the current state-of-the art regarding the system components and the progress toward development of key elements. The full system is anticipated to be small enough in mass, volume and power consumption to allow in situ chemical analysis on highly miniaturized science craft for geochronology, atmospheric characterization and detection of life experiments applicable to outer planet roadmap missions.

Wiberg, D. V.; Eyre, F. B.; Orient, O.; Chutjian, A.; Garkarian, V.

2001-01-01

213

An integrated approach for optimal design of micro gas turbine combustors  

NASA Astrophysics Data System (ADS)

The present work presents an approach for the optimized design of small gas turbine combustors, that integrates a 0-D code, CFD analyses and an advanced game theory multi-objective optimization algorithm. The output of the 0-D code is a baseline design of the combustor, given the required fuel characteristics, the basic geometry (tubular or annular) and the combustion concept (i.e. lean premixed primary zone or diffusive processes). For the optimization of the baseline design a simplified parametric CAD/mesher model is then defined and submitted to a CFD code. Free parameters of the optimization process are position and size of the liner hole arrays, their total area and the shape of the exit duct, while different objectives are the minimization of NOx emissions, pressure losses and combustor exit Pattern Factor. A 3D simulation of the optimized geometry completes the design procedure. As a first demonstrative example, the integrated design process was applied to a tubular combustion chamber with a lean premixed primary zone for a recuperative methane-fuelled small gas turbine of the 100 kW class.

Fuligno, Luca; Micheli, Diego; Poloni, Carlo

2009-06-01

214

Hybrid preconcentrator/focuser module for determinations of explosive marker compounds with a micro-scale gas chromatograph.  

PubMed

This article describes the development and characterization of a partially selective preconcentrator/focuser (PCF) module for a field-portable micro-scale gas chromatograph (?GC) designed to rapidly determine trace levels of two vapor-phase markers of the explosive trinitrotoluene (TNT): 2,3-dimethyl-2,3-dinitrobutane (DMNB) and 2,4-dinitrotoluene (2,4-DNT). The PCF module has three primary components. The first is a high-volume sampler, comprising a resistively-heated 6-cm long stainless steel tube packed with tandem beds of the graphitized carbons Carbopack B (C-B, 30 mg) and Carbopack Y (C-Y, 15 mg), which traps the markers but permits more volatile interferences to pass through largely unretained. The second component is a microfocuser (?F), comprising a 4.2×9.8 mm Si chip containing a deep-reactive-ion-etched (DRIE) cavity packed with 2mg of C-B, a Pyrex cap, integrated heaters, and etched fluidic channels. The third component is a commercial polymer-membrane filter used as a pre-trap to remove particles and adsorbed low volatility interferences. Markers captured in the sampler are thermally desorbed and transferred to the ?F, and then thermally desorbed/injected from the ?F into a downstream separation (micro)column and detected. Scrubbed ambient air is used as carrier gas. The adsorbent capacities, baseline temperatures, sampling and desorption flow rates, and heating profiles were optimized for each PCF module component while minimizing the analysis time. An overall transfer efficiency of 86% was achieved at marker concentrations of ~0.2-2.6 ppb. In the final configuration the PCF module requires just 60s to collect a 1-L sample (3 L/min), focus (40 mL/min), and inject the markers (3 mL/min), producing half-maximum injection peak widths of ~2 and 5 s, and preconcentration factors of 4500 and 1800, for DMNB and 2,4-DNT, respectively. PMID:23357747

Serrano, Gustavo; Sukaew, Thitiporn; Zellers, Edward T

2013-03-01

215

Silicon Carbide Micro-devices for Combustion Gas Sensing under Harsh Conditions  

SciTech Connect

A sensor based on the wide bandgap semiconductor, silicon carbide (SiC), has been developed for the detection of combustion products in power plant environments. The sensor is a catalytic gate field effect device that can detect hydrogen-containing species in chemically reactive, high temperature environments. For fast and stable sensor response measurements, a gate activation process is required. Activation of all sensors took place by switching back and forth between oxidizing (1.0% oxygen in nitrogen) and reducing (10% hydrogen in nitrogen) gases for several hours at a sensor temperature {ge}620 C. All 52 devices on the sensor chip were activated simultaneously by flooding the entire chip with gas. The effects of activation on surface morphology and structure of Pt gates before and after activation were investigated. The optical images obtained from Pt gates demonstrated a clear transition from a smooth and shiny surface to a grainy and cloudy surface morphology. XRD scans collected from Pt gates suggest the presence of an amorphous layer and species other than Pt (111) after activation. The reliability of the gate insulator of our metal-oxide-SiC sensors for long-term device operation at 630 C was studied. We find that the dielectric is stable against breakdown due to electron injection from the substrate with gate leakage current densities as low at 5nA/cm{sup 2} at 630 C. We also designed and constructed a new nano-reactor capable of high gas flow rates at elevated pressure. Our reactor, which is a miniature version of an industrial reactor, is designed to heat the flowing gas up to 700 C. Measurements in ultrahigh vacuum demonstrated that hydrogen sulfide readily deposits sulfur on the gate surface, even at the very high hydrogen/hydrogen sulfide ratios (10{sup 3}-10{sup 5}) expected in applications. Once deposited, the sulfur adversely affects sensor response, and could not be removed by exposure to hydrogen at the temperatures and pressures accessible in the ultrahigh vacuum experiments. Oxygen exposures, however, were very effective at removing sulfur, and the device performance after sulfur removal was indistinguishable from performance before exposure to H{sub 2}S.

Ruby N. Ghosh; Reza Loloee; Roger G. Tobin; Yung Ho Kahng

2006-04-01

216

Hydrogenated microcrystalline silicon germanium: A bottom cell material for amorphous silicon-based tandem solar cells  

Microsoft Academic Search

We have developed hydrogenated microcrystalline silicon germanium, which exhibits a red-shifted absorption spectrum relative to hydrogenated microcrystalline silicon, as a candidate material for the bottom cell of amorphous silicon-based tandem solar cells. Optical absorption, x-ray diffraction, and Raman scattering spectra are presented in addition to optoelectronic properties and light-induced changes.

G. Ganguly; T. Ikeda; T. Nishimiya; K. Saitoh; M. Kondo; A. Matsuda

1996-01-01

217

Design, Fabrication, Testing and Simulation of Porous Silicon Based Smart MEMS Pressure Sensor  

Microsoft Academic Search

Porous silicon based piezoresistive pressure sensor has been designed, fabricated and tested in the range of 0 to 1 bar and temperature range of 20°C to 80°C. A suitable signal conditioning analog circuit consisting of constant current generator and an offset adjustable low noise instrumentation amplifier has been designed and tested. The analog output is then digitized through an ADC

C. Pramanik; T. Islam; H. Saha; J. Bhattacharya; S. Banerjee; Sagnik Dey

2005-01-01

218

Sequential Processes in Palladium-Catalyzed Silicon-Based Cross-Coupling  

PubMed Central

Although developed somewhat later, silicon-based cross-coupling has become a viable alternative to the more conventional Suzuki-Miyaura, Stille-Kosugi-Migita, and Negishi cross-coupling reactions because of its broad substrate scope, high stability of silicon-containing reagents, and low toxicity of waste streams. An empowering and yet underappreciated feature unique to silicon-based cross-coupling is the wide range of sequential processes available. In these processes, simple precursors are first converted to complex silicon-containing cross-coupling substrates, and the subsequent silicon-based cross-coupling reaction affords an even more highly functionalized product in a stereoselective fashion. In so doing, structurally simple and inexpensive starting materials are quickly transformed into value-added and densely substituted products. Therefore, sequential processes are often useful in constructing the carbon backbones of natural products. In this review, studies of sequential processes involving silicon-based cross-coupling are discussed. Additionally, the total syntheses that utilize these sequential processes are also presented.

Denmark, Scott E.; Liu, Jack H.-C.

2012-01-01

219

Fabrication of silicon based through-wafer interconnects for advanced chip scale packaging  

Microsoft Academic Search

This paper presents a fabrication method to achieve through-wafer interconnects (TWIs) by etching, filling and grinding in sequence. Based on this method, advanced chip scale packaging (CSP) is performed. Compared to flip-chip technology, silicon based sensors or actuators, especially large scale detector arrays, can be assembled into a system with the sensing surface upwards, and electrical signals can then be

Fan Ji; Seppo Leppävuori; Ismo Luusua; Kimmo Henttinen; Simo Eränen; Iiro Hietanen; Mikko Juntunen

2008-01-01

220

Preparation of rich handles soft cellulosic fabric using amino silicone based softener, part II: Colorfastness properties  

Microsoft Academic Search

The preparation of amino silicone based softeners with different emulsifiers was carried out and adsorbed onto the surfaces of cotton and blends of cotton\\/polyester fabrics. The softened fabrics have high surface area, so poorly performance in washing and rubbing fastness. It is obvious from the results of colorfastness to rubbing and washing that some of the samples of the dyed

Mohammad Zuber; Khalid Mahmood Zia; Shazia Tabassum; Tahir Jamil; Syed Barkaat-ul-Hasin; Muhammad Kaleem Khosa

2011-01-01

221

Characterization of porous silicon based optical sensor system for biosensor applications  

Microsoft Academic Search

Porous silicon based multilayer structures for optical sensors have been simulated, fabricated and tested. The properties of optical sensors using porous silicon multilayer can be adjusted by appropriate substrate material, morphology, process parameters in the pore formation process and by surface treatment (thermal oxidation). Heavily and lightly doped p-doped substrates have been used to realize porous silicon layers with different

A. Kovacs; P. Jonnalagadda; X. Y. Meng; U. Mescheder

2009-01-01

222

Measurement of Thermoelectric Properties of Amorphous Silicon Based Thin Films  

NASA Astrophysics Data System (ADS)

It is important to understand thermal transport behavior in materials for technological and fundamental physics applications. Many efforts have been made in the past for explaining thermal conduction in solids. It has been observed that thermal transport properties may change with reducing size of the sample, especially as sample size approaches the nanoscale regime. The deviation in these properties, mainly in thermal conductivity, may change the choice of the material for different applications such as thermoelectricity. Thermoelectric materials are a possible source of sustainable energy and can play an important role in the fight against the present energy crisis. Recently, better thermoelectric materials have become available in bulk form as compared to thin film form, with higher figure of merit (ZT = alpha2sigma T=k). ZT is a dimensionless quantity which is used to characterize the performance of thermoelectric materials in terms of the efficiency. Figure of merit (ZT) depends on three fundamental properties including thermal conductivity (k) which is challenging to measure for thin films. This is due to several reasons such as large or more than one background contribution and radiation heating above 100 K. Precise measurements of thermopower (alpha) also become critical for thin films in order to calculate ZT and the efficiency. For devices which rely on thin film technology it is important to have an accurate knowledge of how a material behaves as a thin film in a wide range of temperature. All three of these properties are a function of charge carrier concentration as well as of temperature. In my thesis, I will present novel experimental techniques and measurements of thermoelectric properties in amorphous based thin films over a wide range of temperature. Amorphous Si alloys are expected to have high efficiency for thermoelectric purposes because of their low thermal conductivity and the fact that we can control the charge carrier concentration for optimized thermopower(alpha) and electrical conductivity(sigma) by controlling the dopant concentration. Thermal properties of pure amorphous thin films are also potentially useful in micro- or nano fabrication techniques such as electrically insulating integrated devices. ii

Sultan, Rubina

223

Fabrication and characterization of microelectromechanical systems-based gas chromatography column with embedded micro-posts for separation of environmental carcinogens.  

PubMed

In this paper, a micro gas chromatography (?GC) column with embedded micro-posts was developed for increasing overall surface area of the columns which is able to support more of the stationary phase and reducing the effective width of the column, leading to higher separation efficiency. The proposed columns have a higher sample capacity as the overall surface area is about 3 times larger than that of open columns with the same dimensions. In order to achieve an even flow velocity in the channels, the location of the micro-posts in the linear channels and the configuration of curved channels were optimized by numerical simulation. The results have indicated that the proposed column separated 5 environmental carcinogens in less than 50s, achieved a separation efficiency of about 9500plates/m and eluted highly symmetrical Gaussian peaks. PMID:23601549

Sun, Jianhai; Cui, Dafu; Chen, Xing; Zhang, Lulu; Cai, Haoyuan; Li, Hui

2013-05-24

224

Silicon Carbide Micro-devices for Combustion Gas Sensing under Harsh Conditions  

SciTech Connect

A sensor based on the wide bandgap semiconductor, silicon carbide (SiC), has been developed for the detection of combustion products in power plant environments. The sensor is a catalytic gate field effect device, Pt/SiO{sub 2}/SiC that can detect hydrogen-containing species in chemically reactive, high temperature (600 C) environments. We demonstrate that the device can be used as a hydrogen monitor in syngas applications of common interferants as well as sulfur and water vapor. These measurements were made in the Catalyst Screening Unit at NETL, Morgantown under atmospheric conditions. The sensor response to hydrogen gas at 350 C is 240 mV/decade, this is significantly higher than the device response to room temperature gas or that predicted from vacuum chamber studies. The enhanced catalytic activity of the platinum sensing film under energy plant operating conditions was investigated via AFM, x-ray diffraction, TEM and x-ray photoelectron spectroscopy. Our characterization indicated that exposure to high temperature gases significantly modifies the morphology of the Pt catalytic film and the Pt/SiO{sub 2} interfacial region, which we tentatively attribute to the enhanced hydrogen sensitivity of the sensing film. A model for the hydrogen/oxygen response of the SiC device under atmospheric conditions was developed. It is based on two independent phenomena: a chemically induced shift in the metal-semiconductor work function difference and the passivation/creation of charged states at the SiO{sub 2}-SiC interface. The optimum operating set point for the SiC sensor with respect to response time and long term reliability was determined to be close to mid-gap. Ultrahigh vacuum (UHV) techniques were used to investigate the effects of sulfur contamination on the Pt gate. Exposure to hydrogen sulfide, even in the presence of hydrogen or oxygen at partial pressures of 20-600 times greater than the H2S level, rapidly coated the gate with a monolayer of sulfur. Although hydrogen exposure could not remove the adsorbed sulfur, oxygen was effective at removing sulfur with no evidence of irreversible changes in device behavior. The role of oxygen in the functioning of the SiC sensors was also investigated. All of the results are consistent with oxygen acting through its surface reactions with hydrogen, including the need for oxygen to reset the device to a fully hydrogen-depleted state and competition between hydrogen oxidation and hydrogen diffusion to metal/oxide interface sites. A strong sensor response to the unsaturated linear hydrocarbon propene (C{sub 3}H{sub 6}) was observed.

Ruby Ghosh; Reza Loloee; Roger Tobin

2008-09-30

225

Determination of petroleum contamination in shellfish using solid phase micro-extraction with gas chromatography-mass spectrometry.  

PubMed

Headspace solid phase micro-extraction (HS-SPME) has been applied as a sampling technique for the determination of petroleum contamination in shellfish using capillary gas chromatography-mass spectrometry (GC-MS). A poly(dimethylsiloxane) fused silica fibre (100 microm thickness) was found to be satisfactory for the extraction of a range of aliphatic hydrocarbons (HCs) from homogenised shellfish tissues. The SPME conditions, including temperature, salt content, extraction time and desorption temperature, were optimised for a range of aliphatic HCs (C9-C20). A methyl silicone column GC (12 m x 0.20 mm, 0.33 microm layer thickness) was used with a temperature programme from 40 to 260 degrees C and the HCs were determined within a mass range of m/ z=50-550 in electron impact mode. Calibration range was from 10 to 5000 ng/g with linear correlation coefficients ( r(2)) of 0.982 for nonane to 0.997 for octadecane. Detection limits for aliphatic HCs, spiked into shellfish (mussel) tissues, varied from 3.6 ng/g (tetradecane) to 51 ng/g (eicosane) and relative standard deviation (% RSD) values ranged from 1.4% (hexadecane) to 24.3%(eicosane). PMID:12043016

Stack, Mary A; O'Connell, Sharon; James, Kevin J

2002-06-01

226

Performance expectations for a Tomography System using cosmic ray muons and micro pattern gas detectors for the detection of nuclear contraband  

Microsoft Academic Search

We present results from a detailed GEANT4 simulation of a proposed Muon Tomography System that employs compact Micro Pattern Gas Detectors with high spatial resolution. A basic Point-Of-Closest-Approach algorithm is applied to reconstructed muon tracks for forming 3D tomographic images of interrogated targets. Criteria for discriminating materials by Z and discrimination power achieved by the technique for simple scenarios are

Kondo Gnanvo; Patrick Ford; Jennifer Helsby; Richie Hoch; Debasis Mitra; Marcus Hohlmann

2008-01-01

227

Development and validation of a solid phase micro-extraction–gas chromatography–mass spectrometry method for the determination of furan in baby-food  

Microsoft Academic Search

An efficient and simple method for the determination of furan in baby-food (vegetables and fruits) by solid phase micro-extraction–gas chromatography–mass spectrometry (SPME–GC–MS) was developed and validated. Experimental design was used to investigate the effects of temperature and time of extraction. The calculated regression model was used to find the experimental conditions providing the optimal SPME extraction yield. Validation was carried

Federica Bianchi; Maria Careri; Alessandro Mangia; Marilena Musci

2006-01-01

228

Application of micro-scale sealed vessel thermal desorption–gas chromatography–mass spectrometry for the organic analysis of airborne particulate matter: linearity, reproducibility and quantification  

Microsoft Academic Search

Micro-scale sealed vessel thermal desorption–gas chromatography–mass spectrometry (MSSV-TD–GC–MS) has been applied to the analysis of airborne particulate matter using the US NIST Standard Reference Material (SRM1649a) urban dust. We make qualitative comparisons with open system desorption and illustrate that caution should be used when using the technique without an open system comparison. We report linear responses over the same particulate

Daniel Waterman; Brian Horsfield; Keith Hall; Steve Smith

2001-01-01

229

Differential thermal analysis, thermal gravimetric analysis, and solid phase micro-extraction gas chromatography analysis of water and fuel absorption in diesel soot  

Microsoft Academic Search

An experimental investigation was conducted to analyze the absorption characteristics of deposited diesel soot by differential thermal analysis, thermal gravimetric analysis, and solid phase micro-extraction gas chromatography analysis. The results showed that dry diesel soot contained 2–3%w (percent by weight) of water and a maximum of 5%w hydrocarbons. Water wetted soot contained up to 40%w water, while diesel wetted soot

C. Ayrault; J. S. Chang; D. Ewing; J. S. Cotton; I. E. Gerges; J. Burgers

2010-01-01

230

Headspace solid-phase micro-extraction gas chromatography–mass detection method for the determination of butyltin compounds in wines  

Microsoft Academic Search

Butyltin compounds are widespread contaminants which have also been found in some wines, determined by liquid–liquid extraction followed by alkylation with a Grignard reagent and gas chromatography–mass spectrometric (GC–MS) analysis. A promising alternative to this extraction\\/derivatization method is the one-step tetraethylborate in situ ethylation\\/solid-phase micro-extraction (SPME) method. In this work, a SPME–GC–MS method for the determination of butyltin compounds in

Manuel Azenha; Maria Teresa Vasconcelos

2002-01-01

231

Determination of odorous mixed chloro-bromoanisoles in water by solid-phase micro-extraction and gas chromatography–mass detection  

Microsoft Academic Search

A headspace–solid-phase micro-extraction (HS–SPME) and gas chromatography–mass spectrometry (GC–MS) method has been proposed for the simultaneous determination of odorous trihalogenated anisoles in water. Parameters affecting efficiency of HS–SPME procedure, such as the selection of the SPME coating, extraction time, temperature and ionic strength were optimized. The commercially available polydimethylsiloxane (PDMS 100?m) fiber appears to be the most suitable for the

Alfredo Díaz; Francesc Ventura; M Galceran

2005-01-01

232

Headspace solid-phase micro-extraction and gas chromatography-ion trap tandem mass spectrometry method for butyltin analysis in sediments: Optimization and validation  

Microsoft Academic Search

In this work, headspace solid-phase micro-extraction (SPME) combined with gas chromatography-mass spectrometry (GC-MS) method for analysis of butyltin compounds in sediment samples was upgraded by the introduction of tandem mass spectrometry (MS\\/MS). Optimization and validation of this method based on an one step procedure, tetraethylborate in situ ethylation with simultaneous extraction by headspace SPME, combined with tandem mass spectrometry is

Pedro N. Carvalho; Luiz F. Pinto; M. Clara P. Basto; M. Teresa S. D. Vasconcelos

2007-01-01

233

Vapor sensors using porous silicon-based optical interferometers  

NASA Astrophysics Data System (ADS)

The ability to detect or monitor various gases is important for many applications. Smaller, more portable, lower power, and less expensive gas sensors are needed. Porous silicon (PS) has attracted attention for use in such devices due to its unique optical and electronic properties and its large surface area. This thesis describes the preparation and characteristics of vapor sensors using thin PS Fabry-Perot films. The average refractive index of the PS layer increases when the PS film is exposed to analyte vapors, causing the optical fringes to shift to longer wavelengths. Two methods for monitoring the shifts in these optical fringes are explored in this thesis. The first technique measures the reflection spectrum using a white light source, and the second measures the intensity of reflected light using a low-power red diode laser source. The latter method offers a simple, low-cost and reliable transduction mechanism for vapor sensing. A vapor sensor with a detection limit of 250 ppb and a wide dynamic range (five orders of magnitude) is demonstrated. The effect of the PS film thickness and porosity on sensitivity are systematically studied. A model based on the Bruggeman approximation and capillary condensation is proposed to explain this sensing behavior. Two approaches to improve the sensitivity of the PS sensors are explored. In the first, porous Si is chemically modified and the investigation shows that the sensing response varies with different surface properties. In a second study, thin polymer layers are coated on the porous Si substrate to selectively filter solvent vapors. This bi-layer approach is also applied to porous Si layers that have luminescent quantum structures. These latter structures sense adsorbates based on quenching of luminescence from the quantum-confined silicon nanostructures. In the course of this thesis, an anomalous response of ozone-oxidized PS films to water vapor was discovered. The effect was studied by optical interferometry, isotope studies, and in-situ Fourier transform infrared spectroscopy. It is concluded that in some porous Si films, water forms a strongly hydrogen bonded network that results in compression of the porous Si layer.

Gao, Ting

234

Miniaturized GC/MS instrumentation for in situ measurements: micro gas chromatography coupled with miniature quadrupole array and paul ion trap mass spectrometers  

NASA Technical Reports Server (NTRS)

Miniaturized chemical instrumentation is needed for in situ measurements in planetary exploration and other spaceflight applications where factors such as reduction in payload requirements and enhanced robustness are important. In response to this need, we are 'continuing to develop miniaturized GC/MS instrumentation which combines chemical separations by gas chromatography (GC) with mass spectrometry (MS) to provide positive identification of chemical compounds in complex mixtures of gases, such as those found in the International Space Station's cabin atmosphere. Our design approach utilizes micro gas chromatography components coupled with either a miniature quadrupole mass spectrometer array (QMSA) or compact, high-resolution Paul ion trap.

Holland, P.; Chutjian, A.; Darrach, M.; Orient, O.

2002-01-01

235

A contribution to spectroscopic diagnostics and cathode sheath modeling of micro-hollow gas discharge in argon  

SciTech Connect

In this paper, the hydrogen Balmer beta line shape from a micro-hollow gas discharge (MHGD) in argon with traces of hydrogen is used for simultaneous diagnostics of plasma and cathode sheath (CS) parameters. For this purpose, a simple model of relevant processes responsible for the line broadening is introduced and applied to the Balmer beta profile recorded from a MHGD generated in the microhole (diameter 100 {mu}m at narrow side and 130 {mu}m at wider side) of a gold-alumina-gold sandwich in the pressure range (100-900 mbar). The electron number density N{sub e} in the range (0.4-4.5) x 10{sup 20} m{sup -3} is determined from the width of the central part of the Balmer beta line profile, while, from the extended wings of the Balmer beta profile, induced by dc Stark effect, the next three parameters are determined: the average value E{sub a} of electric field strength in the CS in the range (16-95 kV/cm), the electric field strength E{sub 0} at the cathode surface in the range (32-190 kV/cm), and the CS thickness z{sub g} in the range (18-70 {mu}m). All four MHGD parameters, N{sub e}, E{sub a}, E{sub 0}, and z{sub g}, compare reasonably well with results of the modeling experiment by M. J. Kushner [J. Phys. D: Appl. Phys. 38, 1633 (2005)]. The results for N{sub e} are compared with other emission experiments.

Cvejic, M.; Spasojevic, Dj.; Sisovic, N. M.; Konjevic, N. [Faculty of Physics, University of Belgrade, P.O. Box 368, Belgrade 11001 (Serbia)

2011-08-01

236

Some recent advances in multi-material micro- and nano-manufacturing  

Microsoft Academic Search

The increasing demand for micro-products and components can be met only partly by the lithography-based micro-electromechanical\\u000a systems fabrication processes that originated from the silicon-based microelectronics revolution of the late twentieth century.\\u000a In particular, such processes have limitations when applied to new micro-devices which require the use of a variety of materials\\u000a and complex 3D microstructures with high aspect ratios. In

E. B. Brousseau; S. S. Dimov; D. T. Pham

2010-01-01

237

Simulated thermal conductivity of silicon-based random multilayer thin films  

NASA Astrophysics Data System (ADS)

Reverse nonequilibrium molecular dynamics simulations have been used to quantify the impact of randomly placed mass-altered atomic planes, such as those produced in pseudomorphically grown heterostructures, on the thermal conductivity of silicon. The results indicate that the room temperature thermal conductivity of these silicon-based structures can be reduced to values below 0.050 W/m-K. These values are significantly less than those found in random alloy or superlattice structures containing the same percentage of mass-altered atoms and are attributed to Anderson localization of phonons. Such low lattice thermal conductivity in these silicon-based structures could dramatically improve the thermoelectric efficiency of this earth abundant material.

Frachioni, Anthony; White, B. E.

2012-07-01

238

Nanoscale phosphorus atom arrays created using STM for the fabrication of a silicon based quantum computer.  

SciTech Connect

Quantum computers offer the promise of formidable computational power for certain tasks. Of the various possible physical implementations of such a device, silicon based architectures are attractive for their scalability and ease of integration with existing silicon technology. These designs use either the electron or nuclear spin state of single donor atoms to store quantum information. Here we describe a strategy to fabricate an array of single phosphorus atoms in silicon for the construction of such a silicon based quantum computer. We demonstrate the controlled placement of single phosphorus bearing molecules on a silicon surface. This has been achieved by patterning a hydrogen mono-layer 'resist' with a scanning tunneling microscope (STM) tip and exposing the patterned surface to phosphine (PH3) molecules. We also describe preliminary studies into a process to incorporate these surface phosphorus atoms into the silicon crystal at the array sites. Keywords: Quantum computing, nanotechriology scanning turincling microscopy, hydrogen lithography

O'Brien, J. L. (Jeremy L.); Schofield, S. R. (Steven R.); Simmons, M. Y. (Michelle Y.); Clark, R. G. (Robert G.); Dzurak, A. S. (Andrew S.); Curson, N. J. (Neil J.); Kane, B. E. (Bruce E.); McAlpine, N. S. (Neal S.); Hawley, M. E. (Marilyn E.); Brown, G. W. (Geoffrey W.)

2001-01-01

239

Analysis of silicon-based optical racetrack resonator for acceleration sensing  

NASA Astrophysics Data System (ADS)

Silicon based racetrack resonator are demonstrated as highly sensitive acceleration sensor. The sensor consists of a straight waveguide coupled with a racetrack resonator, and a crossbeam seismic mass serving as the vibration unit. The resonant wavelength, which depends on the optical phase change per round trip, is sensitive to external accelerations due to the waveguide increment and stress-optic effect. With a 30-dB signal-to-noise ratio measurement system, the detection limit and dynamic range are theoretically obtained as high as 4.8×10-4 g under the frequency of acceleration below 200 Hz. The new silicon-based accelerometer will have great potential in seismic prospecting due to its high sensitivity, light weight and immunity to electromagnetic interference.

Mo, Wenqin; Wu, Huaming; Gao, Dingshan; Zhou, Zhiping

2010-05-01

240

Syngas generation from n-butane with an integrated MEMS assembly for gas processing in micro-solid oxide fuel cell systems.  

PubMed

An integrated system of a microreformer and a carrier allowing for syngas generation from liquefied petroleum gas (LPG) for micro-SOFC application is discussed. The microreformer with an overall size of 12.7 mm × 12.7 mm × 1.9 mm is fabricated with micro-electro-mechanical system (MEMS) technologies. As a catalyst, a special foam-like material made from ceria-zirconia nanoparticles doped with rhodium is used to fill the reformer cavity of 58.5 mm(3). The microreformer is fixed onto a microfabricated structure with built-in fluidic channels and integrated heaters, the so-called functional carrier. It allows for thermal decoupling of the cold inlet gas and the hot fuel processing zone. Two methods for heating the microreformer are compared in this study: a) heating in an external furnace and b) heating with the two built-in heaters on the functional carrier. With both methods, high butane conversion rates of 74%-85% are obtained at around 550 °C. In addition, high hydrogen and carbon monoxide yields and selectivities are achieved. The results confirm those from classical lab reformers built without MEMS technology (N. Hotz et al., Chem. Eng. Sci., 2008, 63, 5193; N. Hotz et al., Appl. Catal., B, 2007, 73, 336). The material combinations and processing techniques enable syngas production with the present MEMS based microreformer with high performance for temperatures up to 700 °C. The functional carrier is the basis for a new platform, which can integrate the micro-SOFC membranes and the gas processing unit as subsystem of an entire micro-SOFC system. PMID:23044760

Bieberle-Hütter, A; Santis-Alvarez, A J; Jiang, B; Heeb, P; Maeder, T; Nabavi, M; Poulikakos, D; Niedermann, P; Dommann, A; Muralt, P; Bernard, A; Gauckler, L J

2012-11-21

241

Effect of different surface treatments on tensile bond strength of silicone-based soft denture liner  

Microsoft Academic Search

Failure of the bond between the acrylic resin and resilient liner material is commonly encountered in clinical practice. The\\u000a purpose of this study was to investigate the effect of different surface treatments (sandblasting, Er:YAG, Nd:YAG, and KTP\\u000a lasers) on tensile bond strength of silicone-based soft denture liner. Polymethyl methacrylate test specimens were fabricated\\u000a and each received one of eight surface

Hakan Akin; Faik Tugut; Burcu Mutaf; Gulsah Akin; A. Kemal Ozdemir

242

Electrical Properties of Isotropic Conductive Adhesives Composed of Silicone-Based Elastomer Binders Containing Ag Particles  

Microsoft Academic Search

The electrical properties of isotropic conductive adhesives (ICAs) with two different types of silicone-based binder containing\\u000a Ag particles were examined. The ICAs were printed on glass substrates in order to prepare specimens for evaluating the electrical\\u000a properties. In the case of adhesives containing a denatured silicone binder, both the curing and cooling steps in the isothermal\\u000a curing process generated electrical

Masahiro Inoue; Hiroaki Muta; Shinsuke Yamanaka; Katsuaki Suganuma

2009-01-01

243

Hydrogenated microcrystalline silicon germanium: A bottom cell material for amorphous silicon-based tandem solar cells  

SciTech Connect

We have developed hydrogenated microcrystalline silicon germanium, which exhibits a red-shifted absorption spectrum relative to hydrogenated microcrystalline silicon, as a candidate material for the bottom cell of amorphous silicon-based tandem solar cells. Optical absorption, x-ray diffraction, and Raman scattering spectra are presented in addition to optoelectronic properties and light-induced changes. {copyright} {ital 1996 American Institute of Physics.}

Ganguly, G.; Ikeda, T.; Nishimiya, T.; Saitoh, K.; Kondo, M.; Matsuda, A. [Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba-shi, Ibaraki 305 (Japan)] [Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba-shi, Ibaraki 305 (Japan)

1996-12-01

244

Enhanced performance of silicon based photodetectors using silicon\\/germanium nanostructures  

Microsoft Academic Search

We have studied the influence of nanoscaled lateral silicon\\/silicon–germanium layers and three-dimensional germanium quantum dots on the performance of silicon based infrared detectors in the wavelength range between 2 and 10 ?m and solar cells for space applications. The SiGe heterostructures were grown by molecular-beam epitaxy (MBE) on ?100?-Si substrates allowing it to tailor the photoresponse and cut-off wavelength for

J. Konle; H. Presting; H. Kibbel; K. Thonke; R. Sauer

2001-01-01

245

Effect of Substrate Parasitic Inductance on Silicon-Based Transmission Lines and On-Chip Inductors  

Microsoft Academic Search

We demonstrate that, in addition to the conventional high-order parasitic effects such as skin and proximity effect, as well as substrate coupling, a novel term of substrate parasitic inductance needs to be introduced in the equivalent circuit for silicon-based transmission lines and on-chip spiral inductors in order to fully describe the nonlinear features of substrate-characteristic functions at a high frequency.

Fengyi Huang; Jingxue Lu; Yufeng Zhu; Nan Jiang; Xianchao Wang; Yusong Chi

2007-01-01

246

Porous silicon based extended-bandwidth rugate filters for mid-infrared application  

NASA Astrophysics Data System (ADS)

Porous silicon-based rugate filters operating in the mid-infrared spectral range are fabricated by electrochemical etching of bulk silicon wafers. The rugate filter has a high reflectivity stop-band at 5 ?m with no higher-order harmonics and very small sidelobes. Furthermore, broadband high pass filter having the cutoff wavelength in a mid-infrared range is demonstrated by combining five rugate structures.

Ishikura, Nobuyuki; Fujii, Minoru; Nishida, Kohei; Hayashi, Shinji; Diener, Joachim

2010-07-01

247

Single-Crystalline Silicon-Based Heterojunction Photodiode Arrays on Flexible Plastic Substrates  

Microsoft Academic Search

A silicon-based photodiode array was fabricated on a flexible polyethylene terephthalate substrate using a trans- fer printing technique. A heterojunction structure composed of a 15-nm-thick highly doped hydrogenated amorphous-silicon (n + a-Si:H) layer and a 3-µm-thick p-type single-crystal silicon (p c-Si) membrane layer was adopted as the active layer of the flexible photodiode. The highly ordered photodiode array formed on

Sangwook Lee; Juree Hong; Ja Hoon Koo; Seulah Lee; Kwanghyun Lee; Seongil Im; Taeyoon Lee

2011-01-01

248

Field emission studies of tungsten-coated silicon-based field emitters  

Microsoft Academic Search

Tungsten-coated silicon-based field emitters with a sandwich structure consisting of a cathode tip–insulator–metal gate, were fabricated using microfabrication technology. The radii of the tungsten-coated tips were approximately 30 nm. Each field emitter had a volcano-shaped metal gate aperture with a cathode tip protruding out in the center. The diameter of the smallest metal gate aperture was approximately 1?m. The silicon

L Chen; M. M El-Gomati

1999-01-01

249

A silicon-based tactile sensor for finger-mounted applications  

Microsoft Academic Search

Presents a silicon-based force sensor packaged in a flexible package and describes the sensors performance on human subjects. The sensing element consists of a circular silicon diaphragm (200-?m thick with a 2-mm radius) over a 10-?m sealed cavity with a solid Torlon dome providing force-to-pressure transduction to the diaphragm. Two dome heights (0.5 and 1.5 mm) were compared. The sensor

David J. Beebe; Denice D. Denton; Robert G. Radwin; John G. Webster

1998-01-01

250

Cross-linked silicon based polymer nano-wire formation by high energy charged particles  

Microsoft Academic Search

High energy charged particles penetrating into silicon based polymer materials cause non-homogeneous cross-linking in the nanospace along the particle trajectories, giving nano-gels (nano-wires) of polymers with cylindrical structures of regular length and thickness. Polycarbosilanes with a variety of molecular weights were used as the target polymer materials in the present study, and the preparation of nano-wires based on cross-linked polycarbosilanes

S. Seki; S. Tsukuda; S. Tagawa; M. Sugimoto

2007-01-01

251

Optimization of optical properties of silicon-based anti-reflective spin-on hardmask materials  

Microsoft Academic Search

In the current semiconductor industry, hardmasks have become essential for successful patterning in many applications. Silicon-based anti-reflective spin-on hardmask (Si-SOH), which can be built by spin-on coating, is desirable in terms of mass production throughput and cost of ownership. As the design rule shrinks, the thickness of photoresist also becomes thinner, which forces the thickness of Si-SOH to be thinner

Sang Kyun Kim; Hyeon Mo Cho; Changsoo Woo; Sang Ran Koh; Mi-Young Kim; Hui Chan Yoon; Woojin Lee; Seung-Wook Shin; Jong-Seob Kim; Tuwon Chang

2008-01-01

252

An ellipsometry study of a hydrogenated amorphous silicon based n-i structure  

Microsoft Academic Search

Spectroscopic ellipsometry measurements have been used as a probe to provide information on the structure of a hydrogenated amorphous silicon based n-i two-layer system. The n-i structure is prepared under the same conditions as an a-Si:H p-i-n cell with a thin (?150 A?) n layer deposited in a glow discharge from a mixture of SiF4, SiH4, H2, and PH3 on

R. W. Collins; A. H. Clark; S. Guha; C.-Y. Huang

1985-01-01

253

High-speed silicon-based integrated optical modulators for optical-fiber telecommunications  

NASA Astrophysics Data System (ADS)

A monolithically integrated silicon-based optical modulator is reviewed with respect to design and high-speed performance. The integrated silicon-based optical modulator consists of nested in-phase/quadrature Mach-Zehnder modulator operated in quadrature phase-shift keying formats. Design and performance of high-speed silicon ribwaveguide phase shifters and high-frequency coplanar-waveguide traveling-wave electrode are presented as key modulator elements which allow high-speed zero-chirp operation of the integrated optical modulator in the quadrature phase-shift keying formats. Transmission performance of the integrated optical modulator in differential quadrature phase-shift keying format is characterized in direct-detection constellation-diagram and bit-error-rate measurements towards 44.6-Gbit/s optical-fiber transmission. High-speed quadrature phase-shift keying operation is characterized in coherent-detection constellation-diagram measurements in C and L bands, and QPSK at bit rates up to 64-Gbit/s is presented. A partial-rib-waveguide polarization rotator, which is essential for 128-Gbit/s small-footprint silicon-based optical modulator for digital coherent communication, is described and high-extinction ratio low-loss polarization conversion over C and L bands is evidenced.

Ogawa, Kensuke

2014-03-01

254

Silicon-based microfabricated tin oxide gas sensor incorporating use of Hall effect measurement  

Microsoft Academic Search

Characterization of a microfabricated sol-gel derived nano-particle tin oxide thin film on a silicon substrate, through simultaneous measurement of conductivity, Hall mobility and electron density, had not been accomplished before this study. Conductivity is a function of carrier density and Hall mobility. Therefore, a full understanding of the sensing mechanism of tin oxide requires knowledge of the sensor conductivity, electron

Joseph Wilson Hammond

2000-01-01

255

Quantifying the loss of methane through secondary gas mass transport (or 'slip') from a micro-porous membrane contactor applied to biogas upgrading.  

PubMed

Secondary gas transport during the separation of a binary gas with a micro-porous hollow fibre membrane contactor (HMFC) has been studied for biogas upgrading. In this application, the loss or 'slip' of the secondary gas (methane) during separation is a known concern, specifically since methane possesses the intrinsic calorific value. Deionised (DI) water was initially used as the physical solvent. Under these conditions, carbon dioxide (CO2) and methane (CH4) absorption were dependent upon liquid velocity (V(L)). Whilst the highest CO2 flux was recorded at high V(L), selectivity towards CO2 declined due to low residence times and a diminished gas-side partial pressure, and resulted in slip of approximately 5.2% of the inlet methane. Sodium hydroxide was subsequently used as a comparative chemical absorption solvent. Under these conditions, CO2 mass transfer increased by increasing gas velocity (VG) which is attributed to the excess of reactive hydroxide ions present in the solvent, and the fast conversion of dissolved CO2 to carbonate species reinitiating the concentration gradient at the gas-liquid interface. At high gas velocities, CH4 slip was reduced to 0.1% under chemical conditions. Methane slip is therefore dependent upon whether the process is gas phase or liquid phase controlled, since methane mass transport can be adequately described by Henry's law within both physical and chemical solvents. The addition of an electrolyte was found to further retard CH4 absorption via the salting out effect. However, their applicability to physical solvents is limited since electrolytic concentration similarly impinges upon the solvents' capacity for CO2. This study illustrates the significance of secondary gas mass transport, and furthermore demonstrates that gas-phase controlled systems are recommended where greater selectivity is required. PMID:23726705

McLeod, Andrew; Jefferson, Bruce; McAdam, Ewan J

2013-07-01

256

An electrochemical micro actuator  

Microsoft Academic Search

In this paper an investigation of the feasibility of a new electrochemical micro actuator is presented. The actuator is fabricated using silicon micro-machining techniques. A gas pressure is generated by electrolysis of an aqueous electrolyte solution. The build up pressure is used to change the deflection of a membrane. The actuator has three states: the electrolysis state, in which the

M. W. Hamberg; C. R. Neagu; J. G. E. Gardeniers; D. J. Ijntema; M. C. Elwenspoek

1995-01-01

257

Gas anti-solvent precipitation assisted salt leaching for generation of micro- and nano-porous wall in bio-polymeric 3D scaffolds.  

PubMed

The mass transport through biocompatible and biodegradable polymeric 3D porous scaffolds may be depleted by non-porous impermeable internal walls. As consequence the concentration of metabolites and growth factors within the scaffold may be heterogeneous leading to different cell fate depending on spatial cell location, and in some cases it may compromise cell survival. In this work, we fabricated polymeric scaffolds with micro- and nano-scale porosity by developing a new technique that couples two conventional scaffold production methods: solvent casting-salt leaching and gas antisolvent precipitation. 10-15 w/w solutions of a hyaluronic benzyl esters (HYAFF11) and poly-(lactic acid) (PLA) were used to fill packed beds of 0.177-0.425 mm NaCl crystals. The polymer precipitation in micro and nano-porous structures between the salt crystals was induced by high-pressure gas, then its flushing extracted the residual solvent. The salt was removed by water-wash. Morphological analysis by scanning electron microscopy showed a uniform porosity (~70%) and a high interconnectivity between porous. The polymeric walls were porous themselves counting for 30% of the total porosity. This wall porosity did not lead to a remarkable change in compressive modulus, deformation, and rupture pressure. Scaffold biocompatibility was tested with murine muscle cell line C2C12 for 4 and 7 days. Viability analysis and histology showed that micro- and nano-porous scaffolds are biocompatible and suitable for 3D cell culture promoting cell adhesion on the polymeric wall and allowing their proliferation in layers. Micro- and nano-scale porosities enhance cell migration and growth in the inner part of the scaffold. PMID:24364970

Flaibani, Marina; Elvassore, Nicola

2012-08-01

258

Experimental verification of the feasibility of a 100 W class micro-scale gas turbine at an impeller diameter of 10 mm  

NASA Astrophysics Data System (ADS)

The feasibility of a 100 W class micro-scale gas turbine with a centrifugal impeller of 10 mm diameter has been studied by experimentally verifying the four major component performance requirements found from cycle analysis. The rotor is required to rotate at 870 000 rpm to generate the compressor pressure ratio 3, and it has successfully been achieved by using hydroinertia gas bearings. A compressor efficiency higher than that required by the target cycle has been measured. After correcting the effect of the heat leakage, approximately 65% of the compressor adiabatic efficiency is estimated to be achievable. The combustor has achieved stable self-sustained combustion at a combustion efficiency higher than 99.9%. The heat conduction analysis based on measured data showed that it is possible to keep the compressor below 170 °C when the turbine inlet temperature is 1050 °C. All four requirements are proven to be achievable, and hence, the feasibility of the micro-scale gas turbine at an impeller of 10 mm diameter has successfully been proven at component level.

Isomura, Kousuke; Murayama, Motohide; Teramoto, Susumu; Hikichi, Kousuke; Endo, Yuki; Togo, Shinichi; Tanaka, Shuji

2006-09-01

259

Influence of gas pressure and applied voltage on Xe excimer radiation from a micro dielectric barrier discharge for plasma display panel  

SciTech Connect

We present the influence of gas pressure and applied voltage on Xe excimer radiation from a microdielectric barrier discharge (micro-DBD) in Ne/Xe gas mixture for plasma display panel. Measurements show that the excimer radiation with the 172 nm band lines is strongly observed in the afterglow, and drastically increases with an increase in gas pressure and applied voltage. It is also found that for high gas pressure and low voltage, excimer molecule (Xe{sub 2}{sup *}) is efficiently produced because of less infrared emission from Xe excited atom. The reaction processes of Xe metastable atom (Xe{sub 1s5}{sup *}), which is a precursor for Xe{sub 2}{sup *}, are theoretically analyzed using a one-dimensional fluid model. Increasing gas pressure results in large excimer radiation due to the enhancement of the following three processes, i.e., the conversion process from Xe{sub 1s5}{sup *} to Xe{sub 2}{sup *}, the direct electron impact excitation from ground state to Xe{sub 1s5}{sup *}, and the collisional de-excitation process from upper level (Xe{sup **}) to Xe{sub 1s5}{sup *}. The simulation analytical result shows that for lower voltage, Xe{sub 1s5}{sup *} is efficiently produced due to the increase in the ratio of direct excitation to Xe{sub 1s5}{sup *} from ground state and the suppression of the stepwise ionization from Xe{sub 1s5}{sup *} by electron collisions. While for high voltage operation of micro-DBD, the recombination process with Xe molecular ion (Xe{sub 2}{sup +}) and electron contributes to the total excimer radiation, which can be responsible for the large excimer radiation observed in experiment.

Uchida, Giichiro; Kajiyama, Hiroshi; Shinoda, Tsutae [Graduate School of Advanced Science of Matter, Hiroshima University, Higashi-Hiroshima 739-8530 (Japan); Uchida, Satoshi [Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji 192-0397 (Japan)

2009-10-01

260

Evaluation of solid-phase micro-extraction coupled to gas chromatography–mass spectrometry for the headspace analysis of volatile compounds in cocoa products  

Microsoft Academic Search

The aroma profile of cocoa products was investigated by headspace solid-phase micro-extraction (HS-SPME) combined with gas chromatography–mass spectrometry (GC–MS). SPME fibers coated with 100?m polydimethylsiloxane coating (PDMS), 65?m polydimethylsiloxane\\/divinylbenzene coating (PDMS-DVB), 75?m carboxen\\/polydimethylsiloxane coating (CAR-PDMS) and 50\\/30?m divinylbenzene\\/carboxen on polydimethylsiloxane on a StableFlex fiber (DVB\\/CAR-PDMS) were evaluated. Several extraction times and temperature conditions were also tested to achieve optimum recovery.

Sylvie Ducki; Javier Miralles-Garcia; Albert Zumbé; Antonio Tornero; David M. Storey

2008-01-01

261

An investigation of micro-scale sealed vessel thermal extraction-gas chromatography-mass spectrometry (MSSV-GC-MS#) and micro-scale sealed vessel pyrolysis-gas chromatography-mass spectrometry applied to a standard reference material of an urban dust\\/organics  

Microsoft Academic Search

Sealed vessel thermal extraction and micro-scaled sealed vessel pyrolysis coupled to gas chromatography-mass spectrometry (TH-GC-MS and MSSV-GC-MS) were qualitatively applied to a standard reference material of suspended urban dust\\/organics (NIST Standard Reference Material 1649). Equal amounts of organic compounds and similar concentrations of the most volatile components were produced by both the thermal extract and MSSV techniques. However, the MSSV

P. A. Hall; A. F. R. Watson; G. V. Garner; K. Hall; S. Smith; D. Waterman; B. Horsfield

1999-01-01

262

Humidity Dependence of Charge Transport through DNA Revealed by Silicon-Based Nanotweezers Manipulation  

PubMed Central

The study of the electrical properties of DNA has aroused increasing interest since the last decade. So far, controversial arguments have been put forward to explain the electrical charge transport through DNA. Our experiments on DNA bundles manipulated with silicon-based actuated tweezers demonstrate undoubtedly that humidity is the main factor affecting the electrical conduction in DNA. We explain the quasi-Ohmic behavior of DNA and the exponential dependence of its conductivity with relative humidity from the adsorption of water on the DNA backbone. We propose a quantitative model that is consistent with previous studies on DNA and other materials, like porous silicon, subjected to different humidity conditions.

Yamahata, Christophe; Collard, Dominique; Takekawa, Tetsuya; Kumemura, Momoko; Hashiguchi, Gen; Fujita, Hiroyuki

2008-01-01

263

Monolithic silicon-based 16-QAM modulator using two plasmonic phase shifters  

NASA Astrophysics Data System (ADS)

We propose a compact silicon-based modulator for 16-point quadrature amplitude modulation (16-QAM) with a simple structure using two phase shifters. The phase shifters employ low-loss hybrid plasmon waveguide, consisting of a conductor-gap-dielectric structure filled with polymer. Combining the strong optical confinement ability of the plasmonic waveguide with the highly nonlinear characteristic of the polymer, the proposed 16-QAM modulator can achieve a compact footprint, high-speed operation, and low power consumption, potentially allowing for high-density on-chip integration and broadband long-haul optical transmission.

Li, Fei; Xu, Mu; Hu, Xiaofeng; Wu, Jiayang; Wang, Tao; Su, Yikai

2013-01-01

264

Gas chromatography mass spectrometry determination of acaricides from honey after a new fast ultrasonic-based solid phase micro-extraction sample treatment.  

PubMed

A method is reported for the determination of acaricides (amitraz, bromopropylate, coumaphos and fluvalinate) from honey by gas chromatography mass spectrometry after a new fast solid phase micro-extraction, SPME, procedure. Six different fibers were assessed for micro-extraction purpose studying the following variables: (i) SPME coating, (ii) extraction temperature, (iii) extraction time, (iv) desorption conditions and (v) agitation conditions. The new ultrasonic bath technology providing different sonication frequencies (35 and 130kHz) and different working modes (Sweep, Standard and Degas) was studied and optimized for speeding up the acaricide micro-extraction. The best extraction results were achieved with the polyacrylate fiber. The extraction process was done in 30min using the ultrasonic bath at 130kHz in the Standard mode. Quality parameters of the proposed method show a good precision (<11%) and detection and quantitation limits lower than 6 and 15ng/g, respectively, except for fluvalinate. Eleven Portuguese commercial honey samples were analyzed with the developed method in order to assess the performance of the method with real samples and to determine whether the concentration of acaricides in honey exceed their maximum residue levels (MRLs). Acaricide residues detected were lower than those established by the legislation. PMID:19071541

Rial-Otero, R; Gaspar, E M; Moura, I; Capelo, J L

2007-03-30

265

GEANT4 Simulation of a Cosmic Ray Muon Tomography System With Micro-Pattern Gas Detectors for the Detection of High-Z Materials  

NASA Astrophysics Data System (ADS)

Muon Tomography (MT) based on the measurement of multiple scattering of atmospheric cosmic ray muons traversing shipping containers is a promising candidate for identifying threatening high-Z materials. Since position-sensitive detectors with high spatial resolution should be particularly suited for tracking muons in an MT application, we propose to use compact micro-pattern gas detectors, such as Gas Electron Multipliers (GEMs), for muon tomography. We present a detailed GEANT4 simulation of a GEM-based MT station for various scenarios of threat material detection. Cosmic ray muon tracks crossing the material are reconstructed with a Point-Of-Closest-Approach algorithm to form 3D tomographic images of the target material. We investigate acceptance, Z-discrimination capability, effects of placement of high-Z material and shielding materials inside the cargo, and detector resolution effects for such a MT station.

Hohlmann, Marcus; Ford, Patrick; Gnanvo, Kondo; Helsby, Jennifer; Pena, David; Hoch, Richard; Mitra, Debasis

2009-06-01

266

iGC2: an architecture for micro gas chromatographs utilizing integrated bi-directional pumps and multi-stage preconcentrators  

NASA Astrophysics Data System (ADS)

This paper reports an integrated micro gas chromatography (µGC) architecture which utilizes a bi-directional micropump. Four integral components-–the bi-directional Knudsen pump (KP2), a two-stage preconcentrator-focuser (PCF2), a separation column, and a gas detector-–are integrated in a 4.3 cm3 stack, forming a serial flow path. All four components are fabricated using the same three-mask process. Compared to the conventional approach used with multi-stage preconcentrators, in which valves are used to reverse flow between the sampling phase and the separation phase, this µGC architecture reduces the overall complexity. In this architecture, the vapors being sampled are drawn through the detector and column before reaching the PCF2. The microsystem operation is experimentally validated by quantitative analyses of benzene, toluene, and xylene vapors ranging in concentration from 43–1167 mg m?3.

Qin, Yutao; Gianchandani, Yogesh B.

2014-06-01

267

Measurement of trihalomethanes in potable and recreational waters using solid phase micro extraction with gas chromatography-mass spectrometry  

Microsoft Academic Search

Solid phase micro extraction (SPME) was applied to the determination of selected trihalomethanes (THMs), chloroform, bromodichloromethane, dibromochloromethane, bromoform, in potable and recreational waters. The selected samples were environmentally significant due to mandatory limits imposed by regulatory agencies. Extraction of the analytes was performed using headspace SPME (fused silica fibre with a 100 ?m poly(dimethylsiloxane coating) followed by thermal desorption at

Mary A. Stack; Gillian Fitzgerald; Sharon O'Connell; Kevin J. James

2000-01-01

268

UV Photoactivation of Nano\\/Micro Porous Plant-Derived Carbon and Application to CO2 Gas Adsorption  

Microsoft Academic Search

Activated nano\\/micro-porous carbon was prepared by UV and chemical treatment of plant precursors (Erandmule, Ricinus communis, powder of the roots of the plant; Jawas seeds, Linum usitatissimum; Puffed Rice; Neem roots powder, Azadirachta indica) for use in adsorbing greenhouse gases such as CO2. Zinc chloride was used to increase the interlayer spacing of the carbon materials, and UV irradiation was

Kavita Kulkarni; K. J. Kunte; S. H. Sonawane; A. B. Pandit

2011-01-01

269

Novel multilayered porous silicon-based immunosensor for determining Hydroxysafflor yellow A  

NASA Astrophysics Data System (ADS)

External random factors have a great influence on the fabrication of accurate photonic crystal, especially porous silicon-based photonic crystals. Compared with the binary photonic crystal, polybasic structure photonic crystal shows more stability and smaller effect of the random fluctuation. In this paper, we have fabricated a novel simple porous silicon polybasic Bragg's mirror combined with excellent specific antigen-antibody inmunoreaction as an immunosensor for determining Hydroxysafflor yellow A (HSYA), which is the main chemical component of Carthamus tinctorius L. The binding of HSYA and the polyclonal anti-HSYA antibodies causes red shifts in the reflection spectrum of the sensor, and the red shift was proportional to the HSYA concentration with linear relationship ranging from 1 to 3 ?g mL -1 with a detection limit of 0.78 ng mL -1. Importantly, this research offers hope for development of a commercial porous silicon-based immunosensor for component determination of C. tinctorius L. or other antigens.

Lv, Xiaoyi; Mo, Jiaqing; Jiang, Tao; Zhong, Furu; Jia, Zhenhong; Li, Jiangwei; Zhang, Fuchun

2011-01-01

270

Next Generation Silicon Based Detector Characterization in the LASI Lab at Arizona State University  

NASA Astrophysics Data System (ADS)

We present preliminary results of comprehensive characterization we performed on a Cassini flight spare 1024 x 1024 silicon based CCD, to ensure that our methods are accurate, and a 1024 x 1024 NIR/Red optimized delta-doped, anti-reflection coated silicon based CCD provided by the Nanoscience and Advanced Detector Arrays Group at JPL. We also present here a new facility for CCD calibration and testing at the Laboratory of Astronomical and Space Instrumentation (LASI) at Arizona State University. The current process includes calibration from the optical to near-infrared with future considerations to calibrate into the ultraviolet. We measure several important CCD characterization parameters including, but not limited to; the quantum efficiency, optimum operating temperature, read noise, dark current, gain, linearity and reproducibility. A unique feature of the calibration is the coplanar positioning of the photodiode and CCD. The CCD is stabilized at optimum operating temperature while the photodiode is held at the equilibrium ambient temperature inside an Infrared Laboratories ND-5 Series Dewar. FITS image acquisition is done using the Voodoo software provided with the LEACH controller while control of the monochrometer is done using LABVIEW. All of the image processing is done using an IDL and LABVIEW interface. This work is supported by the Jet Propulsion Laboratory under Award Number 1275804.

Veach, Todd; Scowen, P.; Nikzad, S.

2007-05-01

271

Silicon-based filters, resonators and acoustic channels with phononic crystal structures  

NASA Astrophysics Data System (ADS)

This paper discusses the phenomenon of phononic crystal silicon-based filters, resonators and acoustic channels structured in geometrical periodic arrays created by a single silicon material. Component structured geometrical periodic array refers to a structure of square stubbed rods arranged in repeated arrays on a silicon plate. The study discovered that the band gap of the phononic crystal structure can be modulated under different heights and rotational angles of periodically arrayed square stubbed rods. In addition to band gap modulation, we used the finite element method (FEM) and supercell techniques to analyse the resonance characteristics of defect-containing phononic crystal structures with a larger band gap size design. In addition, the paper also investigated the effects on acoustic channels. Previous studies have already analysed defect-containing resonator and channel phenomenon by the plane-wave expansion method with supercell techniques. However, the FEM can solve numerical issues of extreme difficulty to reach convergence. The results of this study elaborated on the manufacturing feasibility of silicon-based acoustic resonance and filter devices under a complementary metal-oxide-semiconductor synchronization process.

Huang, Zi-Gui

2011-06-01

272

Optimization of optical properties of silicon-based anti-reflective spin-on hardmask materials  

NASA Astrophysics Data System (ADS)

In the current semiconductor industry, hardmasks have become essential for successful patterning in many applications. Silicon-based anti-reflective spin-on hardmask (Si-SOH), which can be built by spin-on coating, is desirable in terms of mass production throughput and cost of ownership. As the design rule shrinks, the thickness of photoresist also becomes thinner, which forces the thickness of Si-SOH to be thinner resulting in a tighter thickness margin. In this case, controlling of optical properties of Si-SOH is important in order to obtain low reflectivity in the exposure process. Previously, we reported papers on silicon-based anti-reflective spin-on hardmask materials for 193 nm lithography and immersion ArF lithography. In this paper, the technique for optimization of optical properties, especially n and k values, of Si-SOH is described. To control n and k values, several chromophores were screened and the ratio among them was optimized. Although the amount of chromophores increased and the silicon contents decreased, our etch resistance enhancement technique allowed Si-SOH to have sufficient etch resistance. Characterization of this Si-SOH and lithographic performance using these materials are described in detail.

Kim, Sang Kyun; Cho, Hyeon Mo; Woo, Changsoo; Koh, Sang Ran; Kim, Mi-Young; Yoon, Hui Chan; Lee, Woojin; Shin, Seung-Wook; Kim, Jong-Seob; Chang, Tuwon

2008-11-01

273

A silicon-based electrochemical sensor for highly sensitive, specific, label-free and real-time DNA detection  

NASA Astrophysics Data System (ADS)

We herein present a new kind of silicon-based electrochemical sensor using a gold nanoparticles-decorated silicon wafer (AuNPs@Si) as a high-performance electrode, which is facilely prepared via in situ AuNPs growth on a silicon wafer. Particularly significantly, the resultant electrochemical sensor is efficacious for label-free DNA detection with high sensitivity due to the unique merits of the prepared silicon-based electrode. Typically, DNA at remarkably low concentrations (1-10 fM) could be readily detected without requiring additional signal-amplification procedures, which is better than or comparable to the lowest DNA concentration ever detected via well-studied signal-amplification-assisted electrochemical sensors. Moreover, the silicon-based sensor features high specificity, allowing unambiguous discrimination of single-based mismatches. We further show that real-time DNA assembly is readily monitored via recording the intensity changes of current signals due to the robust thermal stability of the silicon-based electrode. The unprecedented advantages of the silicon-based electrochemical sensor would offer new opportunities for myriad sensing applications.

Guo, Yuanyuan; Su, Shao; Wei, Xinpan; Zhong, Yiling; Su, Yuanyuan; Huang, Qing; Fan, Chunhai; He, Yao

2013-11-01

274

Micro-scratch analysis and mechanical properties of plasma-deposited silicon-based coatings on polymer substrates  

Microsoft Academic Search

Advanced optical applications require multifunctional coatings with specific mechanical properties, such as resistance to damage and good adhesion to different types of substrates, including polymers. In the present study we deposited amorphous hydrogenated silicon nitride (SiN1.3) and oxide (SiO2) films on polycarbonate and on silicon substrates by plasma enhanced chemical vapor deposition (PECVD), using a dual-mode microwave\\/radio frequency plasma system.

D. Rats; V Hajek; L Martinu

1999-01-01

275

Detection of ethanol in human body fluids by headspace solid-phase micro extraction (SPME)\\/capillary gas chromatography  

Microsoft Academic Search

Ethanol has been found extractable from human whole blood and urine samples by headspace solid-phase micro extraction (SPME) with a Carbowax\\/divinylbenzene-coated fiber. After heating a vial containing the body fluid sample with ethanol, and isobutanol as internal standard (IS) at 70°C in the presence of (NH4)2SO4, a Carbowax\\/divinylbenzene-coated SPME fiber was exposed in the headspace of the vial to allow

T. Kumazawal; H. Seno; X.-P. Lee; A. Ishii; O. Suzuki; K. Sato

1996-01-01

276

Silicon-based reproducible and active surface-enhanced Raman scattering substrates for sensitive, specific, and multiplex DNA detection  

NASA Astrophysics Data System (ADS)

Silicon-based active and reproducible surface-enhanced Raman scattering (SERS) substrate, i.e., silver nanoparticles decorated-silicon wafers (AgNPs@Si), is employed for constructing high-performance sensors. Significantly, the AgNPs@Si, facilely prepared via in situ AgNPs growth on silicon wafers, features excellent SERS reproducibility and high enhancement factor. Our experiment further demonstrates such resultant silicon-based SERS substrate is efficacious for multiplex, sensitive, and specific DNA detection. In particular, single-base mismatched DNA with low concentrations is readily discriminated by using the AgNPs@Si. Moreover, the silicon-based sensor exhibits adequate multiplexing capacity, enabling unambiguous identification of the dual-target DNA detection.

Jiang, Z. Y.; Jiang, X. X.; Su, S.; Wei, X. P.; Lee, S. T.; He, Y.

2012-05-01

277

Micro\\/nanotribological characterization of PDMS and PMMA used for BioMEMS\\/NEMS applications  

Microsoft Academic Search

Tribology is the primary cause of concern for various micro\\/nano-electromechanical systems (MEMS\\/NEMS) and biological applications of MEMS\\/NEMS (BioMEMS\\/NEMS) due to failures resulting from high adhesion and friction. Polymers are gaining significant importance due to their myriad advantages over conventional silicon-based components and the related micromachining techniques. Micro\\/nanotribological characterization of polymers is therefore essential. Adhesion and friction of single crystal silicon

Nikhil S. Tambe; Bharat Bhushan

2005-01-01

278

Improved performance of micro-fabricated preconcentrators using silica nanoparticles as a surface template.  

PubMed

A new approach of enhancing the adsorption capability of the widely used polymer adsorbent Tenax TA poly(2,6-diphenylene oxide) through its deposition on a nano-structured template is reported. The modified Tenax TA-coated silica nanoparticles (SNP) are incorporated as an adsorbent bed in silicon based micro-thermal preconcentrator (?TPC) chips with an array of square microposts embedded inside the cavity and sealed with a Pyrex cover. The interior surface of the chip is first modified by depositing SNP using a layer-by-layer self-assembly technique followed by coating with Tenax TA. The adsorption capacity of the SNP-Tenax TA ?TPC is enhanced by as much as a factor of three compared to the one coated solely with thin film Tenax TA for the compounds tested. The increased adsorption ability of the Tenax TA is attributed to the higher surface area provided by the underlying porous SNP coating and the pores between SNPs affecting the morphology of deposited Tenax TA film by bringing nano-scale features into the polymer. In addition, the adsorption ability of the SNP coating as a pseudo-selective inorganic adsorption bed for polar compounds was also observed. The modified Tenax TA-coated SNP ?TPC is a promising development toward integrated micro-gas chromatography systems. PMID:24268363

Akbar, Muhammad; Wang, Dong; Goodman, Ryan; Hoover, Ashley; Rice, Gary; Heflin, James R; Agah, Masoud

2013-12-27

279

Volatile composition of hybrids Citrus juices by headspace solid-phase micro extraction\\/gas chromatography\\/mass spectrometry  

Microsoft Academic Search

The volatile compounds of Citrus juices have been extracted by headspace solid-phase microextraction (HS-SPME) and analysed by gas chromatography (GC) and gas chromatography\\/mass spectrometry (GC\\/MS). This work deals with the analysis of 65 cross pollinated hybrid fruits and their parents: mandarin (Citrus reticulata Blanco var. Willow Leaf) and clementine (Citrus reticulata×Citrus sinensis var. Commune). Among the 44 components identified which

Toussaint Barboni; François Luro; Nathalie Chiaramonti; Jean-Marie Desjobert; Alain Muselli; Jean Costa

2009-01-01

280

Silicon-based photonic crystals fabricated using proton beam writing combined with electrochemical etching method.  

PubMed

A method for fabrication of three-dimensional (3D) silicon nanostructures based on selective formation of porous silicon using ion beam irradiation of bulk p-type silicon followed by electrochemical etching is shown. It opens a route towards the fabrication of two-dimensional (2D) and 3D silicon-based photonic crystals with high flexibility and industrial compatibility. In this work, we present the fabrication of 2D photonic lattice and photonic slab structures and propose a process for the fabrication of 3D woodpile photonic crystals based on this approach. Simulated results of photonic band structures for the fabricated 2D photonic crystals show the presence of TE or TM gap in mid-infrared range. PMID:22824206

Dang, Zhiya; Breese, Mark Bh; Recio-Sánchez, Gonzalo; Azimi, Sara; Song, Jiao; Liang, Haidong; Banas, Agnieszka; Torres-Costa, Vicente; Martín-Palma, Raúl José

2012-01-01

281

Silicon-based photonic crystals fabricated using proton beam writing combined with electrochemical etching method  

NASA Astrophysics Data System (ADS)

A method for fabrication of three-dimensional (3D) silicon nanostructures based on selective formation of porous silicon using ion beam irradiation of bulk p-type silicon followed by electrochemical etching is shown. It opens a route towards the fabrication of two-dimensional (2D) and 3D silicon-based photonic crystals with high flexibility and industrial compatibility. In this work, we present the fabrication of 2D photonic lattice and photonic slab structures and propose a process for the fabrication of 3D woodpile photonic crystals based on this approach. Simulated results of photonic band structures for the fabricated 2D photonic crystals show the presence of TE or TM gap in mid-infrared range.

Dang, Zhiya; Breese, Mark BH; Recio-Sánchez, Gonzalo; Azimi, Sara; Song, Jiao; Liang, Haidong; Banas, Agnieszka; Torres-Costa, Vicente; Martín-Palma, Raúl José

2012-07-01

282

Multifunctional silicon-based light emitting device in standard complementary metal—oxide—semiconductor technology  

NASA Astrophysics Data System (ADS)

A three-terminal silicon-based light emitting device is proposed and fabricated in standard 0.35 ?m complementary metal—oxide—semiconductor technology. This device is capable of versatile working modes: it can emit visible to near infra-red (NIR) light (the spectrum ranges from 500 nm to 1000 nm) in reverse bias avalanche breakdown mode with working voltage between 8.35 V—12 V and emit NIR light (the spectrum ranges from 900 nm to 1300 nm) in the forward injection mode with working voltage below 2 V. An apparent modulation effect on the light intensity from the polysilicon gate is observed in the forward injection mode. Furthermore, when the gate oxide is broken down, NIR light is emitted from the polysilicon/oxide/silicon structure. Optoelectronic characteristics of the device working in different modes are measured and compared. The mechanisms behind these different emissions are explored.

Wang, Wei; Huang, Bei-Ju; Dong, Zan; Chen, Hong-Da

2011-01-01

283

High-contrast and accurate high-speed simulation of silicon-based modulators  

NASA Astrophysics Data System (ADS)

Silicon-based optical modulator devices have experienced dramatic improvements over the last decade with data rates up to 50Gbps for On-Off-Keying (OOK) consuming ultra low power in fJ/bit [1-3]. The ability to fully understand the performances of these plasma dispersion effect-based devices from a simulation standpoint could be further improved especially in the coupling of high-speed electrical and optical effects. Here, we report an accurate methodology to study high-speed eye diagrams from the electrical and optical simulation data of individual silicon modulators. In particular, we demonstrate the capacity of this simulation methodology by applying it to the current state-of-the-art experimental demonstrated silicon optical modulator using OOK at 50Gbps [3].

Png, Ching Eng; Sun, Min Jie; Lim, Soon Thor; Thomson, David

2014-03-01

284

Silicon-based photonic crystals fabricated using proton beam writing combined with electrochemical etching method  

PubMed Central

A method for fabrication of three-dimensional (3D) silicon nanostructures based on selective formation of porous silicon using ion beam irradiation of bulk p-type silicon followed by electrochemical etching is shown. It opens a route towards the fabrication of two-dimensional (2D) and 3D silicon-based photonic crystals with high flexibility and industrial compatibility. In this work, we present the fabrication of 2D photonic lattice and photonic slab structures and propose a process for the fabrication of 3D woodpile photonic crystals based on this approach. Simulated results of photonic band structures for the fabricated 2D photonic crystals show the presence of TE or TM gap in mid-infrared range.

2012-01-01

285

CMOS compatible silicon-based Mach-Zehnder optical modulators with improved extinction ratio  

NASA Astrophysics Data System (ADS)

Improved Extinction Ratio of 25 dB was demonstrated in silicon based optical modulators on CMOS platform in China. The measurement results agree with the simulation, followed by a discussion about the effects of both propagation loss in Mach-Zehnder arms and power ratio at beam splitters and combiners. The analyses indicate that many considerations have to be taken into design and development of the compatible fabrication of these integrated silicon photonics, especially for the improved extinction ratio of optical modulators. In this summary, we propose the integrated optical modulators in SOI by use of the compatible CMOS processes under the modern CMOS foundry in Chinese homeland. And the measured results were shown, the fast response modulator with the data transmission rate of 10 Gbps.

Li, Zhiyong; Zhou, Liang; Hu, Yingtao; Xiao, Xi; Yu, Yude; Yu, Jinzhong

2011-11-01

286

Silicon-based thin-film transistors with a high stability  

NASA Astrophysics Data System (ADS)

Thin-Film Transistors (TFTs) are widely applied as pixel-addressing devices in large-area electronics, such as active-matrix liquid-crystal displays (AMLCDs) or sensor arrays. Hydrogenated amorphous silicon (a-Si:H) and silicon nitride (a-SiNx:H) are generally used as the semiconductor and the insulator layers, respectively. Commonly, Plasma-Enhanced Chemical Vapor Deposition (PECVD) is used to deposit such films on large glass or plastic substrates at rather low substrate temperatures of 200 - 300oC. Even though TFTs are nowadays used in commercial applications, they need further improvement with respect to a number of issues: Firstly, the stability upon prolonged application of a gate voltage results in a shift of the TFT transfer characteristics. This is explained with the metastability of a-Si:H, namely the defect creation in the amorphous channel. This effect hampers the application of TFTs e.g. in the peripheral driver circuitry of AMLCDs and in the addressing matrix of Organic Light-Emitting Diode (OLED) displays. Secondly, the low deposition rate of the silicon limits the throughput in display fabrication. For a further reduction of the production costs higher deposition rates are crucial. This thesis addresses the development and the study of silicon-based TFTs with a high stability. Therefore, a-Si:H and a-SiNx:H films have been deposited with new techniques, alternative to the commonly used PECVD at a discharge frequency of 13.56 MHz. For Very High Frequency (VHF) PECVD we used frequencies in the range of 13.56 - 70 MHz. Furthermore, we deposited layers by Hot-Wire Chemical Vapor Deposition (HWCVD), utilizing heated tantalum or tungsten filaments to decompose the source-gas molecules catalytically. Hot-wire deposited a-SiNx:H layers were developed to be applied as gate insulator. Furthermore, they are promising for passivation purposes, since no surface damaging ion bombardment is present during the deposition. A proof-of-concept for an "All-Hot-Wire TFT" with both the a-Si:H and the a-SiNx:H deposited by HWCVD is presented, yielding a considerable field-effect mobility of 0.3 cm2/Vs. The stability of various a-Si:H TFTs with either plasma a-SiNx:H or thermally grown SiO2 as the gate insulator was investigated by applying constant gate-bias stress of 25 V at temperatures of 20 - 110oC and durations of 10 - 105s. We determined the kinetics of defect-creation in the amorphous silicon by measuring the threshold-voltage shift and merging the data obtained at different stressing temperatures and times to one data set as a function of the "thermalization energy". This scheme was described by Deane et al.. The kinetics follow a stretched hyperbola, which results from dispersive defect creation with an exponential distribution of activation energies. A least-squares fit yields two parameters: kBT0 is the slope of the barrier distribution, with values of (65 ? 3) meV for all TFTs in this stability study. The second parameter, Ea, is interpreted as the "mean activation energy for defect creation". We used it for a comparison of the stability of various TFTs. For VHF-PECVD a-Si:H TFTs, values for Ea were around 0.92 eV and are found to be correlated with the mechanical stress in silicon films: A high value for Ea, thus a high stability, is related to a low compressive stress. For HWCVD a-Si:H the stability clearly increases with increasing deposition temperatures. The highest value being around 1.03 eV is obtained for het-Si:H, deposited at 510?C. From these results we concluded that the stability of a-Si:H is determined by the grade of network relaxation. Higher deposition temperatures result in a more efficient relaxation of the amorphous network. This can be associated with a higher medium-range order. In the case of the plasma-deposited a-Si:H films deposited at one temperature, the relation between Ea and mechanical stress may be a secondary effect, with the mechanical stress being related to the network ordering. In conclusion, HWCVD appears to be an ideal method to deposit highly stab

Stannowski, Bernd

2002-02-01

287

Corrosion-Prevention Capabilities of a Water-Borne, Silicone-Based, Primerless Coating  

NASA Technical Reports Server (NTRS)

Comparative tests have been performed to evaluate the corrosion-prevention capabilities of an experimental paint of the type described in Water-Borne, Silicone-Based, Primerless Paints, NASA Tech Briefs, Vol. 26, No. 11 (November 2002), page 30. To recapitulate: these paints contain relatively small amounts of volatile organic solvents and were developed as substitutes for traditional anticorrosion paints that contain large amounts of such solvents. An additional desirable feature of these paints is that they can be applied without need for prior application of primers to ensure adhesion. The test specimens included panels of cold-rolled steel, stainless steel 316, and aluminum 2024-T3. Some panels of each of these alloys were left bare and some were coated with the experimental water-borne, silicone-based, primerless paint. In addition, some panels of aluminum 2024-T3 and some panels of a fourth alloy (stainless steel 304) were coated with a commercial solvent-borne paint containing aluminum and zinc flakes in a nitrile rubber matrix. In the tests, the specimens were immersed in an aerated 3.5-weight-percent aqueous solution of NaCl for 168 hours. At intervals of 24 hours, the specimens were characterized by electrochemical impedance spectroscopy (EIS) and measurements of corrosion potentials. The specimens were also observed visually. As indicated by photographs of specimens taken after the 168-hour immersion (see figure), the experimental primerless silicone paint was effective in preventing corrosion of stainless steel 316, but failed to protect aluminum 2024-T3 and cold-rolled steel. The degree of failure was greater in the case of the cold-rolled steel. On the basis of visual observations, EIS, and corrosion- potential measurements, it was concluded that the commercial aluminum and zinc-filled nitrile rubber coating affords superior corrosion protection to aluminum 2024-T3 and is somewhat less effective in protecting stainless steel 304.

Calle, Luz Marina; MacDowell, Louis G.; Vinje, Rubie D.

2005-01-01

288

Effectiveness of a silicon-based root canal sealer for filling of simulated lateral canals.  

PubMed

The purpose of this in vitro study was to evaluate the ability of a silicon-based root canal sealer, compared to zinc oxide and eugenol and an epoxy resin-based sealers, for filling of simulated lateral canals. Thirty extracted single-rooted human teeth were selected, conventional access was made and the working length was established 1 mm from the apical foramen. Three simulated lateral canals, one in each root third (coronal, middle and apical) were prepared in both the mesial and distal surfaces of each tooth using a size 15 reamer adapted to a low-speed handpiece. Each root canal was instrumented using ProTaper rotary files up to file F3 at the working length, and then irrigated with 2.5% NaOCl followed by EDTA. The teeth were assigned to 3 groups (n=10), according to the root canal sealer: Roeko Seal (Group 1), Sealer 26 (group 2) and Grossman's sealer (Group 3). Gutta-percha cold lateral condensation technique was performed in all groups. Postoperative radiographs were taken and the images were projected for evaluation of the quality of lateral canal filling. Data were submitted to statistical analysis by Kruskal Wallis test at 5% significance level. The results showed that Grossman's sealer filled a larger number of lateral canals than Roeko Seal (p<0.05) and Sealer 26 (p<0.01). It may be concluded that Roeko Seal silicone-based root canal sealer was not as effective as the Grossman's sealer for filling of simulated lateral canals. The lateral canals localized in the apical third of the root were more difficult to be filled. PMID:17639195

Barbizam, João Vicente Baroni; Souza, Matheus; Cecchin, Doglas; Dabbel, Jakob

2007-01-01

289

Development of a bar adsorptive micro-extraction-large-volume injection-gas chromatography-mass spectrometric method for pharmaceuticals and personal care products in environmental water matrices.  

PubMed

The combination of bar adsorptive micro-extraction using activated carbon (AC) and polystyrene-divinylbenzene copolymer (PS-DVB) sorbent phases, followed by liquid desorption and large-volume injection gas chromatography coupled to mass spectrometry, under selected ion monitoring mode acquisition, was developed for the first time to monitor pharmaceutical and personal care products (PPCPs) in environmental water matrices. Assays performed on 25 mL water samples spiked (100 ng L(-1)) with caffeine, gemfibrozil, triclosan, propranolol, carbamazepine and diazepam, selected as model compounds, yielded recoveries ranging from 74% to 99% under optimised experimental conditions (equilibrium time, 16 h (1,000 rpm); matrix characteristics: pH 5, 5% NaCl for AC phase; LD: methanol/acetonitrile (1:1), 45 min). The analytical performance showed good precision (RSD < 18%), convenient detection limits (5-20 ng L(-1)) and excellent linear dynamic range (20-800 ng L(-1)) with remarkable determination coefficients (r(2) > 0.99), where the PS-DVB sorbent phase showed a much better efficiency. By using the standard addition methodology, the application of the present analytical approach on tap, ground, sea, estuary and wastewater samples allowed very good performance at the trace level. The proposed method proved to be a suitable sorption-based micro-extraction alternative for the analysis of priority pollutants with medium-polar to polar characteristics, showing to be easy to implement, reliable, sensitive and requiring a low sample volume to monitor PPCPs in water matrices. PMID:22076312

Neng, N R; Nogueira, J M F

2012-01-01

290

MEMS monocrystalline-silicon based thermal devices for chemical and microfluidic applications  

Microsoft Academic Search

This thesis explores the employment of monocrystalline silicon in microsystems as an active material for different thermal functions, such as heat generation and heat transfer by conduction.\\u000aIn chapter 1 applications that need thermal micro devices, micro heaters and micro heat exchangers, are briefly introduced. The shortcomings of commonly used materials are listed, and monocrystalline silicon is identified as an

M. Mihailovic

2011-01-01

291

Speciation analysis of organotin compounds in human urine by headspace solid-phase micro-extraction and gas chromatography with pulsed flame photometric detection.  

PubMed

A new headspace solid-phase micro-extraction (HS-SPME) method followed by gas chromatography with pulsed flame photometric detection (GC-PFPD) analysis has been developed for the simultaneous determination of 11 organotin compounds, including methyl-, butyl-, phenyl- and octyltin derivates, in human urine. The methodology has been validated by the analysis of urine samples fortified with all analytes at different concentration levels, and recovery rates above 87% and relative precisions between 2% and 7% were obtained. Additionally, an experimental-design approach has been used to model the storage stability of organotin compounds in human urine, demonstrating that organotins are highly degraded in this medium, although their stability is satisfactory during the first 4 days of storage at 4 °C and pH=4. Finally, this methodology was applied to urine samples collected from harbor workers exposed to antifouling paints; methyl- and butyltins were detected, confirming human exposure in this type of work environment. PMID:24840433

Valenzuela, Aníbal; Lespes, Gaëtane; Quiroz, Waldo; Aguilar, Luis F; Bravo, Manuel A

2014-07-01

292

Simple and rapid assay method for simultaneous quantification of urinary nicotine and cotinine using micro-extraction by packed sorbent and gas chromatography-mass spectrometry.  

PubMed

A simple and rapid method for determination of nicotine and cotinine levels in urine was developed using samples prepared by micro-extraction by packed sorbent (MEPS) and subjected to gas chromatography-mass spectrometry (GC-MS) analysis. This method provided good reproducibility, as well as good linearity of calibration curves in the range of 1-100 and 50-1000 ng/mL for quality control samples spiked with nicotine and cotinine, respectively. The detection limit of nicotine and cotinine was as low as 0.25 and 20 ng/mL, respectively. An evaporation procedure is not suitable for nicotine determination, thus an advantage of the present MEPS assay method is direct testing with GC-MS without the need for evaporation to a dry solvent. Our findings show that it may be useful for determining nicotine levels in various types of research studies. PMID:24640182

Iwai, Masae; Ogawa, Tadashi; Hattori, Hideki; Zaitsu, Kei; Ishii, Akira; Suzuki, Osamu; Seno, Hiroshi

2013-08-01

293

Pore scale distribution of gas hydrates in sediments by micro X-ray Computed Tomography (X-CT)  

NASA Astrophysics Data System (ADS)

A dedicated apparatus was developed to observe in-situ pore scale distribution of gas hydrate directly during hydrate formation in artificial cores. The high-resolution X-ray Computed Tomography (type: GE Sensing & Inspection Technologies GmbH Phoenix x-ray V/tomex/s) was used and the effective resolution for observing gas hydrate bearing sediments can up to about 18?m. Methane gas hydrate was formed in 0.425-0.85mm sands under a pressure of 6MPa and a temperature of 3°C. During the process, CT scanning was conducted if there's a pressure drop (the scanning time is 66 minutes each time), so that the hydrate morphology could be detected. As a result, five scanning CT images of the same section during gas hydrate formation (i.e. hydrate saturation at 3.9%, 24.6%, 35.0%, 51.4% and 97.0%) were obtained. The result shows that at each hydrate saturation level, hydrate morphology models are complicated. The occurrence of 'floating model' (i.e. hydrate floats in pore fluid), 'contact model' (i.e. hydrate contact with the sediment particle), and the 'cementing model' (i.e. hydrates cement the sediment particles) can be found at the same time (Fig. 1). However, it shows that at different hydrate formation stages, the dominant hydrate morphology are not the same. For instance, at the first stage of hydrate formation, although there are some hydrates floating in the pore fluid, most hydrates connect the sediment particles. Consequently, the hydrate morphology at this moment can be described as a cementing model. With this method, it can be obtained that at the higher level of saturation (e.g., hydrate saturation at 24.6% and 35.0%), hydrates are mainly grow as a floating model. As hydrate saturation is much higher (e.g. after hydrate saturation is more than 51.4%), however, the floating hydrates coalesce with each other and the hydrates cement the sediment particle again. The direct observed hydrate morphology presented here may have significant impact on investigating acoustic properties of gas hydrate bearing sediments. The pore scale distribution of gas hydrate may also provide important information for the future study of gas hydrate petroleum system. Fig. 1. Pore scale distribution of gas hydrates in sediments by X-CT. [A] Hydrate saturation (Sh)=3.9%, [B] Sh=24.6%, [C] Sh=35.0%, [D] Sh= 51.4% .

Hu, G.; Li, C.; Ye, Y.; Liu, C.; Best, A. I.

2013-12-01

294

Effects of nonlocal plasmons in gapped graphene micro-ribbon array and two-dimensional electron gas on near-field electromagnetic response in the deep subwavelength regime.  

PubMed

A self-consistent theory involving Maxwell's equations and a density-matrix linear-response theory is solved for an electromagnetically coupled doped graphene micro-ribbon array (GMRA) and a quantum well (QW) electron gas sitting at an interface between a half-space of air and another half-space of a doped semiconductor substrate, which supports a surface-plasmon mode in our system. The coupling between a spatially modulated total electromagnetic (EM) field and the electron dynamics in a Dirac-cone of a graphene ribbon, as well as the coupling of the far-field specular and near-field higher-order diffraction modes, are included in the derived electron optical-response function. Full analytical expressions are obtained with nonlocality for the optical-response functions of a two-dimensional electron gas and a graphene layer with an induced bandgap, and are employed in our numerical calculations beyond the long-wavelength limit (Drude model). Both the near-field transmissivity and reflectivity spectra, as well as their dependence on different configurations of our system and on the array period, ribbon width, graphene chemical potential of QW electron gas and bandgap in graphene, are studied. Moreover, the transmitted E-field intensity distribution is calculated to demonstrate its connection to the mixing of specular and diffraction modes of the total EM field. An externally tunable EM coupling among the surface, conventional electron-gas and massless graphene intraband plasmon excitations is discovered and explained. Furthermore, a comparison is made between the dependence of the graphene-plasmon energy on the ribbon's width and chemical potential in this paper and the recent experimental observation given by [Nat. Nanotechnol.6, 630-634 (2011)] for a GMRA in the terahertz-frequency range. PMID:23385917

Huang, Danhong; Gumbs, Godfrey; Roslyak, Oleksiy

2013-02-01

295

Development of dielectric and amorphous-silicon-based thin film coatings for room- and cryogenic temperature applications  

Microsoft Academic Search

This paper reports on the development of dielectric and amorphous silicon-based thin film stacks for applications at room and liquid nitrogen (LN) cryogenic temperatures. The deposition process was performed using assisted energetic evaporation processes such as Reactive Low Voltage Ion Plating (RLVIP) and Ion Assisted Deposition (IAD). Dielectric coatings produced by RLVIP exhibited fairly good stability at LN temperature. Indeed,

Michel Poirier; Samir Ilias; Simon Thibault; Patrice Topart; Hubert Jerominek

2004-01-01

296

Optimized temperature-pulse sequences for the enhancement of chemically specific response patterns from micro-hotplate gas sensors  

Microsoft Academic Search

Microfabricated solid-state gas sensors have been of continuing interest because of the potential for arrays of devices with low power consumption. Devices based on a micromachined ‘hotplate’ offer the additional advantage of a wide operating temperature range with a rapid thermal time constant of order 1 ms. By operating the device in a temperature-programmed mode, reaction kinetics on the sensing

R. E. Cavicchi; J. S. Suehle; K. G. Kreider; M. Gaitan; P. Chaparala

1996-01-01

297

Design and characterization of temperature-robust piezoresistive micro-pressure sensor with double-Wheatstone-bridge structure  

Microsoft Academic Search

This study presents a silicon-based micro-pressure sensor in which the piezoresistive patches on the polysilicon membrane are configured in the form of two concentric Wheatstone bridge circuits. The sensors in the central circuit measure the membrane deflection caused by the combined effects of the pressure and the ambient temperature, respectively, while those in the outer circuit measure the deflection induced

Hsun-Heng Tsai; Chi-Chang Hsieh; Cheng-Wen Fan; Young-Chang Chen; Wei-Te Wu

2009-01-01

298

Evaluation of micro-bubble size and gas hold-up in two-phase gas–liquid columns via scattered light measurements  

Microsoft Academic Search

In this paper, potential use of an elliptically polarized light scattering (EPLS) method to monitor both bubble size and gas hold-up in a bubble-laden medium is explored. It is shown that with the use of the new EPLS system, normalized scattering matrix elements (Mij's) measured at different side and back-scattering angles can be used to obtain the desired correlations between

Mustafa M. Aslan; Czarena Crofcheck; Daniel Tao; M. Pinar Mengüç

2006-01-01

299

Dispersive micro solid-phase extraction for the rapid analysis of synthetic polycyclic musks using thermal desorption gas chromatography-mass spectrometry.  

PubMed

A simple and solvent-free method for the rapid analysis of five synthetic polycyclic musks in water samples is described. The method involves the use of dispersive micro solid-phase extraction (D-?-SPE) coupled with direct thermal desorption (TD) gas chromatography-mass spectrometry (GC-MS) operating in the selected-ion-storage (SIS) mode. The parameters affecting the extraction efficiency of the target analytes from water sample and the thermal desorption conditions in the GC injection-port were optimized using a central composite design method. The optimal extraction conditions involved immersing 3.2mg of a typical octadecyl (C18) bonded silica adsorbent (i.e., ENVI-18) in a 10mL water sample. After extraction by vigorously shaking for 1.0min, the adsorbents were collected and dried on a filter. The adsorbents were transferred to a micro-vial, which was directly inserted into GC temperature-programmed injector, and the extracted target analytes were then thermally desorbed in the GC injection-port at 337°C for 3.8min. The limits of quantitation (LOQs) were determined to be 1.2-3.0ng/L. Precision, as indicated by relative standard deviations (RSDs), was less than 9% for both intra- and inter-day analysis. Accuracy, expressed as the mean extraction recovery, was between 74 and 90%. A preliminary analysis of the river water samples revealed that galaxolide (HHCB) and tonalide (AHTN) were the two most common synthetic polycyclic musks present. Using a standard addition method, their concentrations were determined to in the range from 11 to 140ng/L. PMID:23932027

Chung, Wu-Hsun; Tzing, Shin-Hwa; Ding, Wang-Hsien

2013-09-13

300

NOTE: Measurement of skin dose variations produced by a silicon-based protective dressing in radiotherapy  

NASA Astrophysics Data System (ADS)

Variations in skin dose caused by a silicon-based burn dressing used in radiotherapy during treatment have been investigated. Measurement of these variations in skin dose has been achieved using thermoluminescent dosimeters (TLDs) and Gafchromic film. For a 6 MV x-ray beam results have shown that an approximately 0.4 mm thick silicon mesh dressing increases the average surface dose by approximately 12.5% to 14% of the maximum and average dose at 1 mm depth and by 4% to 6% of the maximum for field sizes ranging from 5 cm × 5 cm up to 40 cm × 40 cm at 100 cm source to surface distance (SSD). The radiation effective thickness of the silicon dressing was calculated to be 0.5 mm +/- 0.05 mm water equivalent. TLDs of various thicknesses provide point-dose assessment and Gafchromic film can provide a detailed two-dimensional dose map with a high spatial resolution. Results have shown that a large variation in skin dose is delivered under the dressing depending on the amount of material directly above it as defined by the silicon mesh outline.

Butson, Martin J.; Cheung, Tsang; Yu, Peter K. N.; Metcalfe, Peter

2002-06-01

301

On-Wafer Measurement of a Silicon-Based CMOS VCO at 324 GHz  

NASA Technical Reports Server (NTRS)

The world s first silicon-based complementary metal oxide/semiconductor (CMOS) integrated-circuit voltage-controlled oscillator (VCO) operating in a frequency range around 324 GHz has been built and tested. Concomitantly, equipment for measuring the performance of this oscillator has been built and tested. These accomplishments are intermediate steps in a continuing effort to develop low-power-consumption, low-phase-noise, electronically tunable signal generators as local oscillators for heterodyne receivers in submillimeter-wavelength (frequency > 300 GHz) scientific instruments and imaging systems. Submillimeter-wavelength imaging systems are of special interest for military and law-enforcement use because they could, potentially, be used to detect weapons hidden behind clothing and other opaque dielectric materials. In comparison with prior submillimeter- wavelength signal generators, CMOS VCOs offer significant potential advantages, including great reductions in power consumption, mass, size, and complexity. In addition, there is potential for on-chip integration of CMOS VCOs with other CMOS integrated circuitry, including phase-lock loops, analog- to-digital converters, and advanced microprocessors.

Samoska, Lorene; Man Fung, King; Gaier, Todd; Huang, Daquan; Larocca, Tim; Chang, M. F.; Campbell, Richard; Andrews, Michael

2008-01-01

302

PREFACE: Coordination Action on Defects Relevant to Engineering Silicon-Based Devices  

NASA Astrophysics Data System (ADS)

This issue contains a selection of papers presented at the First International Workshop of the European project entitled Coordination Action on Defects Relevant to Engineering Silicon-Based Devices (CADRES) held in Catania, Sicily, 26--28 September 2004. The CADRES project is sponsored by the European Commission in the Framework 6 IST programme. The Workshop was attended by about 107 delegates, from many European countries, who heard presentations from speakers prominent in their fields from all over the world, plus several excellent student presentations. Over the three days there were opportunities for very focussed discussion, and all who attended could benefit from new collaboration and training opportunities available as a result of this meeting. I would like to thank the local organizers, Professor Francesco Priolo and his students for the smooth running of the workshop, and Professor Bengt Svensson for acting as the Programme Chairman. I would also like to thank Professors Svensson and Priolo for their help with the selection of papers for the workshop and with the Proceedings.

Evans-Freeman, Jan

2005-06-01

303

Silicon-based optoelectronic integrated circuit for label-free bio/chemical sensor.  

PubMed

We demonstrate a silicon-based optoelectronic integrated circuit (OEIC) for label-free bio/chemical sensing application. Such on-chip OEIC sensor system consists of optical grating couplers for vertical light coupling into silicon waveguides, a thermal-tunable microring as a tunable filter, an exposed microring as an optical label-free sensor, and a Ge photodetector for a direct electrical readout. Different from the conventional wavelength-scanning method, we adopt low-cost broadband ASE light source, together with the on-chip tunable filter to generate sliced light source. The effective refractive index change of the sensing microring induced by the sensing target is traced by scanning the supplied electrical power applied onto the tracing microring, and the detected electrical signal is read out by the Ge photodetector. For bulk refractive index sensing, we demonstrate using such OEIC sensing system with a sensitivity of ~15 mW/RIU and a detection limit of 3.9 ?-RIU, while for surface sensing of biotin-streptavidin, we obtain a surface mass sensitivity of S(m) = ~192 µW/ng?mm(-2) and a surface detection limit of 0.3 pg/mm(2). The presented OEIC sensing system is suitable for point-of-care applications. PMID:23938665

Song, Junfeng; Luo, Xianshu; Kee, Jack Sheng; Han, Kyungsup; Li, Chao; Park, Mi Kyoung; Tu, Xiaoguang; Zhang, Huijuan; Fang, Qing; Jia, Lianxi; Yoon, Yong-Jin; Liow, Tsung-Yang; Yu, Mingbin; Lo, Guo-Qiang

2013-07-29

304

A silicon-based, three-dimensional neural interface: manufacturing processes for an intracortical electrode array.  

PubMed

A method has been developed for the manufacture of a "three-dimensional" electrode array geometry for chronic intracortical stimulation. This silicon based array consists of a 4.2 x 4.2 x 0.12 mm thick monocrystalline substrate, from which project 100 conductive, silicon needles sharpened to facilitate cortical penetration. Each needle is electrically isolated from the other needles, and is about 0.09 mm thick at its base and 1.5 mm long. The sharpened end of each needle is coated with platinum to facilitate charge transfer into neural tissue. The following manufacturing processes were used to create this array. 1) Thermomigration of 100 aluminum pads through an n-type silicon block. This creates trails of highly conductive p+ silicon isolated from each other by opposing pn junctions. 2) A combination of mechanical and chemical micromachining which creates individual penetrating needles of the p+ silicon trails. 3) Metal deposition to create active electrode areas and electrical contact pads. 4) Array encapsulation with polyimide. The geometrical, mechanical, and electrical properties of these arrays should make them well suited as interfaces to cortical tissue. PMID:1937509

Campbell, P K; Jones, K E; Huber, R J; Horch, K W; Normann, R A

1991-08-01

305

Nanostructural defects evidenced in failing silicon-based NMOS capacitors by advanced failure analysis techniques  

NASA Astrophysics Data System (ADS)

An experimental methodology compliant with industrial constraints was deployed to uncover the origin of soft breakdown events in large planar silicon-based NMOS capacitors. Complementary advanced failure analysis techniques were advantageously employed to localize, isolate and observe structural defects at nanoscale. After an accurate localization of the failing area by optical beam-induced resistance change (OBIRCH), focused ion beam (FIB) technique enabled preparing thin specimens adequate for transmission electron microscopy (TEM). Characterization of the gate oxide microstructure was performed by highresolution TEM imaging and energy-filtered spectroscopy. A dedicated experimental protocol relying on iterative FIB thinning and TEM observation enabled improving the quality of electron imaging of defects at atom scale. In that way, the gate oxide integrity was evaluated and an electrical stress-induced silicon epitaxy was detected concomitantly to soft breakdown events appearing during constant voltage stress. The growth of silicon hillocks enables consuming a part of the breakdown energy and may prevent the soft breakdown event to evolve towards a hard breakdown that is catastrophic for device functionality.

Faivre, Emilie; Llido, Roxane; Putero, Magali; Fares, Lahouari; Muller, Christophe

2014-04-01

306

Characterization of Pt-doped SnO2 catalyst for a high-performance micro gas sensor.  

PubMed

The atomic scale structure and its dependence on Pt concentration of a Pt-doped SnO2 (Pt-SnO2) thin film produced by a sputter-deposition method was investigated, which showed high-performance as a methane gas sensor. Extended X-ray absorption fine structure (EXAFS) and X-ray diffraction (XRD) analyses showed that Pt-SnO2 has a rutile structure similar to SnO2 crystals at less than 10 at% Pt where the Pt ion was located at the Sn position in the rutile structure. There was no evidence that Pt metal clusters were formed in the Pt-SnO2 films. The Pt-SnO2 structure became amorphous at greater than 11 at% Pt. We found a good correlation between the methane activity and local structure of Pt. PMID:24045584

Murata, Naoyoshi; Suzuki, Takuya; Kobayashi, Makoto; Togoh, Fumiaki; Asakura, Kiyotaka

2013-11-01

307

Moment tensor inversion for two micro-earthquakes occurring inside the Háje gas storage facilities, Czech Republic  

NASA Astrophysics Data System (ADS)

Broadband data from the P?íbram seismological network was used to investigate the source of two earthquakes, with magnitudes M w = 0.2 and 0.4 respectively, occurring in the period of October-November 2009 in the Háje natural gas storage area (Czech Republic). Both events were located inside the limits of the storage area and at depths similar to those of the underground caverns where the gas is stored. We applied an inversion technique using the software ISOLA for moment tensor retrieval in order to assess the source process of both events and recognize whether a significant isotropic component existed that could be interpreted as a possible cavern collapse. We also performed an uncertainty analysis so as to confirm the reliability of the focal mechanism solutions and we controlled the consistency between the inverted focal mechanisms and those calculated using the P-waves first motions. Our results showed that the nodal plane orientation, the centroid depth, and the magnitude remained stable. Furthermore, we calculated synthetic waveforms for collapse-type ruptures and compared them with the original records. The match between the synthetic and the original data was very poor supporting the interpretation of the shear character of the events. The combination of the inversion results, which indicated significant double-couple components and of the synthetic tests, which supported the inexistence of an isotropic component at the source, led to the conclusion that the possibility of rocks falling from the ceiling of the caverns or a cavern collapse is highly unlikely.

Benetatos, Christoforos; Málek, Ji?í; Verga, Francesca

2013-04-01

308

Monitoring the emission of volatile organic compounds from flowers of Jasminum sambac using solid-phase micro-extraction fibers and gas chromatography with mass spectrometry detection.  

PubMed

Solid-phase micro-extraction (SPME) was studied as a solvent free alternative method for the extraction and characterization of volatile compounds in intact and plucked flowers of Jasminum sambac at different day time intervals using gas chromatography (GC-FID) and gas chromatography-quadrupole mass spectrometry. The analytes identified included alcohols, esters, phenolic compounds, and terpenoids. The main constituents identified in the flower aroma using different fibers were cis-3-hexenyl acetate, (E)-beta-ocimene, linalool, benzyl acetate, and (E,E)-alpha-farnesene. The benzyl acetate proportion decreased from morning to afternoon and then increased in evening collections. PDMS fiber showed a high proportion of (E,E)-alpha-farnesene in jasmine floral aroma. Among other constituents identified, cis-3-hexenyl acetate, linalool, and benzyl acetate were major aroma contributors in plucked and living flowers extracts using PDMS/DVB, Carboxen/PDMS, and DVB/Carboxen/PDMS fibers. PDMS/DVB recorded the highest emission for benzyl acetate while the (E)-beta-ocimene proportion was highest in DVB/Carboxen/PDMS when compared with the rest. The highest linalool content, with increasing proportion from morning to noon, was found using mixed coating fibers. Almost negligible volatile adsorption was recorded for the polyacrylate fiber for intact flower aroma, whereas it was most effective for benzyl acetate, followed by indole under plucked conditions. Moreover, the highest amounts extracted, evaluated from the sum of peak areas, were achieved using Carboxen/PDMS, and DVB/Carboxen/PDMS. Introduction of a rapid, and solvent free SPME method for the analysis of multicomponent volatiles can be successfully employed to monitor the extraction and characterization of flower aroma constituents. PMID:21941909

Pragadheesh, Vppalayam Shanmugam; Yadav, Anju; Chanotiya, Chandan Singh; Rout, Prasanta Kumar; Uniyal, Girish Chandra

2011-09-01

309

A Silicone-Based Wire-Reinforced Tracheal Tube with a Hemispherical Bevel Reduces Nasal Morbidity for Nasotracheal Intubation  

Microsoft Academic Search

We tested the hypothesis that a silicone-based wire- reinforced tracheal tube with a hemispherical bevel is su- perior to a polyvinyl chloride (PVC)-based precurved tube with a conventional diagonal bevel for nasotracheal intubation. Eighty anesthetized paralyzed adults (ASA physical status I-II) requiring nasotracheal intubation for tonsillectomy were randomly allocated into two equal- sized groups for airway management with the silicone

Shinichi Kihara; Tetsuya Komatsuzaki; Joseph R. Brimacombe; Yuichi Yaguchi; Noriko Taguchi; Seiji Watanabe

2003-01-01

310

Formation of Silicon-Based Thin Films Prepared by Catalytic Chemical Vapor Deposition (Cat-CVD) Method  

Microsoft Academic Search

This paper is a review of the catalytic chemical vapor deposition (Cat-CVD) method and properties of silicon-based thin films, such as amorphous-silicon (a-Si), polycrystalline-silicon (p-Si) and silicon nitride (SiNx) films, prepared by the Cat-CVD method. In the Cat-CVD method, also known as the hot-wire CVD (HWCVD) method, deposition gases are decomposed by catalytic cracking reactions with a heated catalyzer placed

Hideki Matsumura

1998-01-01

311

Release of markers from the inner water phase of W \\/ O \\/ W emulsions stabilized by silicone based polymeric surfactants  

Microsoft Academic Search

Silicone based surfactants were used as stabilizers for W\\/O\\/W double emulsions with unusual mechanical stability. W\\/O\\/ W multiple emulsions containing several markers were prepared. The entrapped markers were: (1) halide salts, (2) a typical drug, ephedrine hydrochloride, and (3) KNO3 (water soluble fertilizer).Good solute trapping (95% yield of preparation) with slow release rates through the liquid oil membrane (60% release

Y. Sela; S. Magdassi; N. Garti

1995-01-01

312

On-chip mode-control in active silicon-based photonic molecule by complete photon confinement  

Microsoft Academic Search

We have demonstrated an efficient way to build on-chip active silicon-based photonic molecules in complete photonic bandgap confinement [1]. Due to the conformal deposition processes on square patterns, the luminescent layers are naturally confined in three-dimensional photonic bandgap materials. The confined optical modes in photonic molecules exhibit very similar energy level structure as in chemical molecules. In this paper, the

Bo Qian; Kunji Chen; San Chen; Wei Li; Xiangao Zhang; Jun Xu; Xinfan Huang; Chunping Jiang

2011-01-01

313

High-separation efficiency micro-fabricated multi-capillary gas chromatographic columns for simulants of the nerve agents and blister agents.  

PubMed

To achieve both high speed and separation efficiency in the separation of a mixture of nerve and blister agent simulants, a high-aspect-ratio micro-fabricated multi-capillary column (MCC, a 50-cm-long, 450-?m-deep, and 60-?m-wide four-capillary column) was fabricated by the application of the microelectromechanical system (MEMS) techniques. Mixtures of chemical warfare agent (CWA) simulants - dimethyl methylphosphonate (DMMP), triethyl phosphate (TEP), and methyl salicylate - were used as samples. The fabricated MCC allowed for the separation of all the components of the gaseous mixture within 24 s, even when the difference in boiling point was 4°C, as in the case of TEP and methyl salicylate. Furthermore, interfering agents - dichloromethane, ethanol, and toluene - were also included in the subsequent gaseous mixture samples. The boiling point of these six components ranged from 78°C to 219°C. All six components were clearly separated within 70 s. This study is the first to report the clear separation of gas mixtures of components with close boiling points. The column efficiency was experimentally determined to be 12,810 plates/m. PMID:24899869

Li, Yi; Du, Xiaosong; Wang, Yang; Tai, Huiling; Qiu, Dong; Lin, Qinghao; Jiang, Yadong

2014-01-01

314

Performance Analysis and Optimum Operation Planning of Distributed Energy System Based on Micro Gas Turbine-Solid Oxide Fuel Cell Hybrid Power Generation  

NASA Astrophysics Data System (ADS)

In this paper, the economical and energy saving advantages of the distributed energy system, which consists of a micro gas turbine-solid oxide fuel cell hybrid power generation system, waste heat recovery devices and air-conditioning equipments, are investigated. Firstly, the thermodynamical performance evaluation of the hybrid system with the heat recovery devices is discussed to estimate the energy conversion efficiency of the whole system. Secondly, by using 1inear programming technique, the optimum operation planning of the cogeneration plant based on the hybrid system is discussed to predict the reduction of the primary fuel consumption and utility cost. Throughout detailed investigation, it is found that the energy conversion efficiency, which includes the waste heat utilization, reaches over 80% (LHV). In addition, the optimum operation of the hybrid system, of which power generation capacity is appropriate for the energy demand, achieve the highly effective energy saving against the traditional energy supply scheme, that is, the fuel reduction reaches around 40% to the conventional value.

Morita, Aina; Kimijima, Shinji

315

Rapid analysis of tile industry gaseous emissions by ion mobility spectrometry and comparison with solid phase micro-extraction/gas chromatography/mass spectrometry.  

PubMed

The present paper reports on a rapid method for the analysis of gaseous emissions from ceramic industry, based on ion mobility spectrometry (IMS) as a means for on-site monitoring of volatile organic compounds (VOCs) produced during tile baking. IMS was calibrated with a set of reference compounds (i.e. ethyl acetate, ethanol, ethylene glycol, diethylene glycol, acetaldehyde, formaldehyde, 2-methyl-1,3-dioxolane, 2,2-dimethyl-1,3-dioxolane, 1,3-dioxolane, 1,4-dioxane, benzene, toluene, cyclohexane, acetone, acetic acid) via air-flow permeation. The technique was tested on a laboratory-scale kiln and tiles prepared with selected glycol- and resin-based additives. Finally, the analytical method was applied to emissions from two industries in the Modena (Italy) ceramic area. The results of all experimental phases were compared to those obtained by solid phase micro-extraction/gas chromatography/mass spectrometry (SPME/GC/MS). IMS showed potential as a real-time monitoring device for quality assessment in ceramic industry emissions. IMS spectra, SPME/GC/MS data, relationship between additives/baking conditions and produced VOCs and advantages and limitations of both techniques will be discussed. PMID:17133278

Pozzi, R; Bocchini, P; Pinelli, F; Galletti, G C

2006-12-01

316

High-separation efficiency micro-fabricated multi-capillary gas chromatographic columns for simulants of the nerve agents and blister agents  

NASA Astrophysics Data System (ADS)

To achieve both high speed and separation efficiency in the separation of a mixture of nerve and blister agent simulants, a high-aspect-ratio micro-fabricated multi-capillary column (MCC, a 50-cm-long, 450-?m-deep, and 60-?m-wide four-capillary column) was fabricated by the application of the microelectromechanical system (MEMS) techniques. Mixtures of chemical warfare agent (CWA) simulants - dimethyl methylphosphonate (DMMP), triethyl phosphate (TEP), and methyl salicylate - were used as samples. The fabricated MCC allowed for the separation of all the components of the gaseous mixture within 24 s, even when the difference in boiling point was 4°C, as in the case of TEP and methyl salicylate. Furthermore, interfering agents - dichloromethane, ethanol, and toluene - were also included in the subsequent gaseous mixture samples. The boiling point of these six components ranged from 78°C to 219°C. All six components were clearly separated within 70 s. This study is the first to report the clear separation of gas mixtures of components with close boiling points. The column efficiency was experimentally determined to be 12,810 plates/m.

Li, Yi; Du, Xiaosong; Wang, Yang; Tai, Huiling; Qiu, Dong; Lin, Qinghao; Jiang, Yadong

2014-05-01

317

Sensitive and robotic determination of bromate in sea water and drinking deep-sea water by headspace solid-phase micro extraction and gas chromatography-mass spectrometry.  

PubMed

A robotic method has been established for the determination of bromate in sea water and drinking deep-sea water. Bromate in water was converted into volatile derivative, which was measured with headspace solid-phase micro extraction and gas chromatography-mass spectrometry (HS-SPME GC-MS). Derivatization reagent and the HS-SPME parameters (selection of fibre, extraction/derivatization temperature, heating time and; the morality of HCl) were optimized and selected. Under the established conditions, the detection and the quantification limits were 0.016 ?g L(-1) and 0.051 ?g L(-1), respectively, and the intra- and inter-day relative standard deviation was less than 7% at concentrations of 1.0 and 10.0 ?g L(-1). The calibration curve showed good linearity with r(2)=0.9998. The common ions Cl(-), NO(3)(-), SO(4)(2-), HPO(4)(2-), H(2)PO(4)(-), K(+), Na(+), NH(4)(+), Ca(2+), Mg(2+), Ba(2+), Mn(4+), Mn(2+), Fe(3+) and Fe(2+) did not interfere even when present in 1000-fold excess over the active species. The method was successfully applied to the determination of bromate in sea water and drinking deep-sea water. PMID:22840702

Lim, Hyun-Hee; Shin, Ho-Sang

2012-09-01

318

Determination of Se using a solid-phase micro-extraction device coupled to a graphite furnace and detection by gas chromatography-mass spectrometry.  

PubMed

A solid-phase micro-extraction (SPME) method using an SPME fiber device and graphite furnace (GF) for extracting Se compounds was proposed. Various factors affecting the derivatization and extraction of Se(IV) by SPME-GF were evaluated, including the effect of acid (type and concentration), the concentration of the derivatizing agent, the derivatization temperature, the extraction and derivatization times and the extraction temperature. After optimizing these conditions, the quantification of Se(IV) was performed by Gas Chromatography-Mass Spectrometry (GC-MS). The limit of detection was 0.37 ?g L(-1) for Se(IV). The method was successfully applied to the total Se determination in certified reference materials (BCR-414 and SRM 1643e). A recovery of 97% was obtained for water (SRM 1643e). After microwave oven decomposition and the reduction of selenium using a mixture of 2 mol L(-1) HCl and 1% (w/v) KBr, a recovery of 101% and a relative standard deviation of 3.5% were attained for plankton (BCR-414). The SPME-GF method combined with GC-MS was also applied to the determination of the total selenium in a drug sample (selenium chelate). PMID:22760433

Gomes da Silva, Elidiane; Augusto, Fabio; Arruda, Marco Aurélio Zezzi

2012-08-21

319

Forensic analysis of a single particle of partially burnt gunpowder by solid phase micro-extraction-gas chromatography-nitrogen phosphorus detector.  

PubMed

Solid phase micro-extraction (SPME) was adopted to extract organic gun shot residues (OGSRs) from a single particle of partially burnt gunpowder. The partially burnt particle samples were collected from gun shot residue (GSR) deposited near the target areas. OGSRs, such as diphenylamine (DPA), methyl centralite (MC), ethyl centralite (EC), from only one single particle of partially burnt gunpowder were successfully extracted by SPME and analyzed by a gas chromatography coupled to a nitrogen phosphorus detector (GC-NPD). The results confirmed that the new extraction procedure is capable of extracting trace amount of MC and EC as signature molecules for the identification of GSR. The method represents a solvent-free extraction as a complementary analytical procedure for the forensic analysis of GSR-related evidences. The new extraction scheme with the capability of analyzing single particle of partially burnt gunpowder can also be applied to the identification of explosive residues, such as in post-blast investigations of improvised explosive devices. PMID:19375082

Burleson, Garrett Lee; Gonzalez, Brittney; Simons, Kelsie; Yu, Jorn C C

2009-05-29

320

Headspace, solid-phase micro-extraction, gas chromatographic-mass spectrometric analysis of terpenoids in the latex of Euphorbia species.  

PubMed

The volatile and semi-volatile terpenoids in the latex of Euphorbia amygdaloides, E. exigua, E. helioscopia, and E. peplus were analyzed by headspace, solid-phase micro-extraction (HS-SPME), coupled with gas chromatography-mass spectrometry. The volatiles were extracted using a 100 microm polydimethylsiloxane SPME fiber under optimized extraction conditions. The compounds detected encompassed a range of chemical classes, but only terpenoids were evaluated. Only sesquiterpene hydrocarbons were detected in the tested samples of E. exigua, E. helioscopia, and E. peplus, with beta-caryophyllene being the major one, but were never recorded in latex samples of E. amygdaloides, in which only the diterpene hydrocarbon kaur-16-ene was detected. Alpha-Humulene was consistently found in samples of E. helioscopia, and E. peplus, but never in those of the other two species. These preliminary results show that the developed procedure is suitable for the analysis of small samples of Euphorbia latex and that, for each individual species, there is very little qualitative difference between samples, regardless of either place or date of collection. PMID:23472461

Patel, Asmita V; Sumner, Stephen; Thompson, H Leslie; Blunden, Gerald; Wright, David; Liu, Jun-Feng; Zan, Jun-Feng

2013-01-01

321

High-separation efficiency micro-fabricated multi-capillary gas chromatographic columns for simulants of the nerve agents and blister agents  

PubMed Central

To achieve both high speed and separation efficiency in the separation of a mixture of nerve and blister agent simulants, a high-aspect-ratio micro-fabricated multi-capillary column (MCC, a 50-cm-long, 450-?m-deep, and 60-?m-wide four-capillary column) was fabricated by the application of the microelectromechanical system (MEMS) techniques. Mixtures of chemical warfare agent (CWA) simulants - dimethyl methylphosphonate (DMMP), triethyl phosphate (TEP), and methyl salicylate - were used as samples. The fabricated MCC allowed for the separation of all the components of the gaseous mixture within 24 s, even when the difference in boiling point was 4°C, as in the case of TEP and methyl salicylate. Furthermore, interfering agents - dichloromethane, ethanol, and toluene - were also included in the subsequent gaseous mixture samples. The boiling point of these six components ranged from 78°C to 219°C. All six components were clearly separated within 70 s. This study is the first to report the clear separation of gas mixtures of components with close boiling points. The column efficiency was experimentally determined to be 12,810 plates/m.

2014-01-01

322

Dispersive micro-solid phase extraction combined with gas chromatography-chemical ionization mass spectrometry for the determination of N-nitrosamines in swimming pool water samples.  

PubMed

A simple sample pretreatment technique, dispersive micro-solid phase extraction, was applied for the extraction of N-nitrosodimethylamine (NDMA) and other four N-nitrosamines (NAs) from samples of swimming pool water. The parameters affecting the extraction efficiency were systematically investigated. The best extraction conditions involved immersing 75 mg of carbon molecular sieve, Carboxen™ 1003 (as an adsorbent), in a 50-mL water sample (pH 7.0) containing 5% sodium chloride in a sample tube. After 20 min of extraction by vigorous shaking, the adsorbent was collected on a filter and the NAs desorbed by treatment with 150 ?L of dichloromethane. A 10-?L aliquot was then directly determined by large-volume injection gas chromatography with chemical ionization mass spectrometry using the selected ion storage mode. The limits of quantitation were <0.9 ng/L. The precision for these analytes, as indicated by relative standard deviations, were <8% for both intra- and inter-day analyses. Accuracy, expressed as the mean extraction recovery, was between 62% and 109%. A preliminary analysis of swimming pool water samples revealed that NDMA was present in the highest concentration, in the range from n.d. to 100 ng/L. PMID:22222914

Fu, Ssu-Chieh; Tzing, Shin-Hwa; Chen, Hsin-Chang; Wang, Yu-Chen; Ding, Wang-Hsien

2012-02-01

323

Angular dependence of the magnetoresistance effect in a silicon based p-n junction device  

NASA Astrophysics Data System (ADS)

We report a pronounced angular dependence of the magnetoresistance (MR) effect in a silicon based p-n junction device at room temperature by manipulating the space charge region of the p-n junction under a magnetic field. For the p-n junction device with various space charge region configurations, we find that all the angular dependence of the MR effect is proportional to sin2(?), where the ? is the angle between the magnetic field and the driving current. With increasing the magnetic field and driving current, the anisotropic MR effect is obviously improved. At room temperature, under a magnetic field 2 T and driving current 20 mA, the MR ratio is about 50%, almost one order of amplitude larger than that in the magnetic material permalloy. Our results reveal an interpretation of the MR effect in the non-magnetic p-n junction in terms of the Lorentz force and give a new way for the development of future magnetic sensors with non-magnetic p-n junctions.We report a pronounced angular dependence of the magnetoresistance (MR) effect in a silicon based p-n junction device at room temperature by manipulating the space charge region of the p-n junction under a magnetic field. For the p-n junction device with various space charge region configurations, we find that all the angular dependence of the MR effect is proportional to sin2(?), where the ? is the angle between the magnetic field and the driving current. With increasing the magnetic field and driving current, the anisotropic MR effect is obviously improved. At room temperature, under a magnetic field 2 T and driving current 20 mA, the MR ratio is about 50%, almost one order of amplitude larger than that in the magnetic material permalloy. Our results reveal an interpretation of the MR effect in the non-magnetic p-n junction in terms of the Lorentz force and give a new way for the development of future magnetic sensors with non-magnetic p-n junctions. Electronic supplementary information (ESI) available: S1(a) shows the I-V characteristics of the p-n junction device for various magnetic field orientations in the x-z plane at room temperature. S1(b) shows the corresponding anisotropic MR curves at specific current I = 20 mA. S2 shows the I-V characteristics of the p-n junction device while the magnetic field is applied in the x-y plane. S3 shows the I-V curves at negative bias with various magnetic fields. S4(a) shows the I-V curves of the sample in various electrodes without a magnetic field. The size of the sample is 2.9 mm × 2.26 mm, and the thickness is 0.14 mm. S4(b) shows the Hall voltage in the sample's n region for the current I = 0.01 mA. See DOI: 10.1039/c3nr04077a

Wang, Tao; Si, Mingsu; Yang, Dezheng; Shi, Zhong; Wang, Fangcong; Yang, Zhaolong; Zhou, Shiming; Xue, Desheng

2014-03-01

324

Interaction of silicon-based quantum dots with gibel carp liver: oxidative and structural modifications  

PubMed Central

Quantum dots (QDs) interaction with living organisms is of central interest due to their various biological and medical applications. One of the most important mechanisms proposed for various silicon nanoparticle-mediated toxicity is oxidative stress. We investigated the basic processes of cellular damage by oxidative stress and tissue injury following QD accumulation in the gibel carp liver after intraperitoneal injection of a single dose of 2 mg/kg body weight Si/SiO2 QDs after 1, 3, and 7 days from their administration. QDs gradual accumulation was highlighted by fluorescence microscopy, and subsequent histological changes in the hepatic tissue were noted. After 1 and 3 days, QD-treated fish showed an increased number of macrophage clusters and fibrosis, while hepatocyte basophilia and isolated hepatolytic microlesions were observed only after substantial QDs accumulation in the liver parenchyma, at 7 days after IP injection. Induction of oxidative stress in fish liver was revealed by the formation of malondialdehyde and advanced oxidation protein products, as well as a decrease in protein thiol groups and reduced glutathione levels. The liver enzymatic antioxidant defense was modulated to maintain the redox status in response to the changes initiated by Si/SiO2 QDs. So, catalase and glutathione peroxidase activities were upregulated starting from the first day after injection, while the activity of superoxide dismutase increased only after 7 days. The oxidative damage that still occurred may impair the activity of more sensitive enzymes. A significant inhibition in glucose-6-phosphate dehydrogenase and glutathione-S-transferase activity was noted, while glutathione reductase remained unaltered. Taking into account that the reduced glutathione level had a deep decline and the level of lipid peroxidation products remained highly increased in the time interval we studied, it appears that the liver antioxidant defense of Carassius gibelio does not counteract the oxidative stress induced 7 days after silicon-based QDs exposure in an efficient manner.

2013-01-01

325

Broadband and highly efficient grating couplers for silicon-based horizontal slot waveguides  

NASA Astrophysics Data System (ADS)

Optical nonlinear effects have been widely studied in III-V semiconductor photonics. However, nonlinear performance in silicon photonics is still inefficient. An alternative silicon-based waveguide configuration, which is known as slot waveguide, has been recently proposed to improve the nonlinear performance in a very efficient way. In the slot waveguide, the fundamental mode light is highly confined in a very small region, which is called slot, of a low index contrast material between two silicon high index contrast layers. This enables the introduction of new silicon photonic devices in which the characteristics of active optical materials can be efficiently exploited for modulation, switching, sensing, and other applications. Horizontal and vertical slot waveguides for optimum nonlinear performance have been recently proposed. However, the horizontal slot waveguide is more feasible for nonlinear applications. To increase nonlinear performance in the horizontal slot region, silicon nanocrystals (Si-nc) embedded in silica (SiO2) have been proposed to fill the slot region between the two silicon layers. It is achievable nonlinear performance in the horizontal slot region for down to 50nm thick slots. However, the lower the slot thickness is, the more difficult the coupling to fiber results. One of the most developed silicon photonics efficient vertical coupling techniques is the grating coupler. We demonstrate grating couplers for efficient coupling between horizontal slot waveguides and standard single mode fibers. Broadband and highly efficient horizontal slot waveguide grating couplers have been obtained by means of simulations. These grating couplers configuration are suitable for nonlinear performance in silicon photonics. It is achieved 61% maximum coupling efficiency for ?=1550 nm and TM polarization. Furthermore, a 35 nm 1dB-bandwidth is achievable for the designed grating couplers.

Galan, J. V.; Sanchis, P.; Blasco, J.; Martí, J.

2008-05-01

326

Novel large-area thermal neutron imaging detectors comprising 157 Gd CsI-convertors and micro-strip gas detectors with low-pressure, two-stage amplification and delay line readout  

Microsoft Academic Search

A novel large-area (0.5 × 0.5 m2) two-dimensional position-sensitive detector for thermal and sub-thermal neutrons is being developed comprising 157GdCsI multilayer convertor foils and two fourfold segmented micro-strip gas detector (MSGC) planes for electron multiplication on either side of the convertor. The MSGC operates in low-pressure, two-stage amplification mode; their novel design is optimized for that mode and for obtaining

B. Gebauer; Ch. Schulz; Th. Wilpert

1997-01-01

327

Simultaneous determination of bisphenol A and bisphenol B in beverages and powdered infant formula by dispersive liquid–liquid micro-extraction and heart-cutting multidimensional gas chromatography-mass spectrometry  

Microsoft Academic Search

The purpose of this study was to establish a reliable, cost-effective, fast and simple method to quantify simultaneously both bisphenol A (BPA) and bisphenol B (BPB) in liquid food matrixes such as canned beverages (soft drinks and beers) and powdered infant formula using dispersive liquid–liquid micro-extraction (DLLME) with in-situ derivatisation coupled with heart-cutting gas chromatography-mass spectrometry (GC-MS). For the optimisation

S. C. Cunha; C. Almeida; E. Mendes; J. O. Fernandes

2011-01-01

328

An automated method for the analysis of phenolic acids in plasma based on ion-pairing micro-extraction coupled on-line to gas chromatography\\/mass spectrometry with in-liner derivatisation  

Microsoft Academic Search

A new method is presented for the analysis of phenolic acids in plasma based on ion-pairing ‘Micro-extraction in packed sorbent’ (MEPS) coupled on-line to in-liner derivatisation-gas chromatography–mass spectrometry (GC–MS). The ion-pairing reagent served a dual purpose. It was used both to improve extraction yields of the more polar analytes and as the methyl donor in the automated in-liner derivatisation method.

Sonja Peters; Erwin Kaal; Iwan Horsting; Hans-Gerd Janssen

2012-01-01

329

Measurement of Toluene Concentrations in the Blood of Fetuses of Pregnant Rats Exposed to Low Concentration Toluene Using Headspace-Solid Phase Micro Extraction-Gas Chromatography-Mass Spectrometry  

Microsoft Academic Search

In order to measure the level of toluene in the blood of fetuses of pregnant rats exposed to toluene, application of headspace-solid phase micro extraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) was studied. Pregnant rats from gestational day 15 (GD15) to GD19 were subjected to inhalational exposure to toluene for 90 min per day. They were obtained by Cesarean section on the fifth

Daisuke Nakajima; Shinji Tsukahara; Rieko Hojo; Shiho Kageyama; Sumio Goto; Hiroaki Shiraishi; Fujio Shiraishi; Hidekazu Fujimakia

2009-01-01

330

Development, validation and application of a methodology based on solid-phase micro extraction followed by gas chromatography coupled to mass spectrometry (SPME\\/GC–MS) for the determination of pesticide residues in mangoes  

Microsoft Academic Search

A method was developed for the simultaneous analysis of 14 pesticide residues (clofentezine, carbofuran, diazinon, methyl parathion, malathion, fenthion, thiabendazole, imazalil, bifenthrin, permethrin, prochloraz, pyraclostrobin, difenoconazole and azoxystrobin) in mango fruit, based on solid-phase micro extraction (SPME) coupled to gas chromatography–mass spectrometry (GC–MS). Different parameters of the method were evaluated, such as fiber type, extraction mode (direct immersion and headspace),

Adalberto Menezes Filho; Fábio Neves dos Santos; Pedro Afonso de Paula Pereira

2010-01-01

331

Silicon-Based Optical Waveguide Modulators and Mode-Locked TITANIUM:SAPPHIRE Laser Dynamics.  

NASA Astrophysics Data System (ADS)

Single-mode deeply-etched silicon-germanium/silicon (SiGe/Si) rib waveguides have been fabricated and characterized with low propagation losses and strong guiding. Such a waveguide structure is suitable for bent waveguide devices and provides efficient field overlapping, which is needed for devices requiring strong nonlinear coupling. Using the deeply-etched waveguide technique, we have fabricated Si/SiGe/Si Mach-Zehnder modulators, which show strong single-mode waveguiding but only small electro -optic modulation has been observed so far. Another Si modulator is a Fabry-Perot interferometer. We have demonstrated all-optical modulation at 1.3 ?m and 1.5 ?m in the reflection mode of the asymmetric Si Fabry-Perot interferometer by a control light beam at 0.85 mum. Both switching -on and switching-off operations are demonstrated by transversely moving the etalon. In addition, we have analyzed that silicon carbide (SiC) waveguides exhibit low loss for fundamental modes and high loss for higher-order modes at wavelengths from 0.6 to 1.6 mum. Electro-optic modulation is analyzed with a SiC-on-SiO_2 waveguide structure. Such modulators are potential candidates for high-speed electro-optic modulation for silicon-based optoelectronic devices. Furthermore, we studied the dynamics of a Kerr -lens self-mode-locked Ti:sapphire laser, generating 40 -fs pulses and tunable from 750 nm to 920 nm. A moving mirror was first proposed as a starting mechanism for self -mode locking and the starting dynamics is studied in detail. In addition, periodic pulse-train amplitude modulations have been observed and studied. The observation of the amplitude modulation further confirms the dynamic Kerr-lens self -focusing model of self-mode locking in Ti:sapphire lasers and helps us better understand the laser performance. Furthermore, dual-wavelength mode locking is observed over a broad tuning range, which would be very useful for two-wavelength subpicosecond optical sampling, such as pump-probe experiments that require different wavelengths for pumping and probing.

Liu, Yanming

332

Investigation of the Biodegradation of Chlorinated Ethenes at the Pore-Scale Using Silicon- Based Micromodels  

NASA Astrophysics Data System (ADS)

Groundwater contamination by chlorinated ethenes is a matter of serious concern in industrialized countries due to the hazardous nature of these solvents. Biodegradation of these contaminants has proved to be the most cost-effective remediation technology to solve this problem. One of the most common degradation pathways is anaerobic reductive dechlorination, in which chlorinated ethenes are successively reduced from PCE to TCE to DCE to Vinyl chloride and finally to ethene, an environmentally benign substance. The success rates of this degradation with batch cultures are not often repeatable in column or field scale experiments due to the complexities associated with the heterogeneous porous medium. Hence it is important to understand degradation phenomena at the pore-scale in order to devise successful remediation techniques at a larger scale. In this study, 1 cm2 silicon based micromodels were used to simulate the subsurface at the pore-scale. The microbial culture used was Dehalospirillum multivorans. A solution of PCE (0.2 mM) and lactate (1 mM) was fed continuously into the micromodel at a rate of 0.001ml/min, which translated to a Darcy velocity in the porous matrix of 9.6m/day. Micromodels were observed with epi-fluorescence and DIC microscopy with a microscope equipped with an automated stage, CCD camera and an image analysis system. Activity within the micromodel was verified by the presence of cis-DCE in the effluent, which indicated that 95% of the PCE had been degraded. Visible biomass was also observed within a few weeks of starting PCE feeding both by DIC and fluorescence microscopy. The active and inactive zones of degradation were identified by the use of pH sensitive fluorescent dyes. The aggregates of cell biomass were quantified based on their area and perimeter in the images. These measurements indicated that after a few weeks, the biomass had reached a steady-state with new cells growing at the same rate as the sloughing of old biomass. This is the first time an anaerobic organism had been successfully grown in a micromodel. Further experiments are being planned to conduct biodegradation experiments with mixed cultures in the presence of competing electron acceptors and with PCE as a separate phase in the micromodel.

Nambi, I. M.; Werth, C. J.; Sanford, R. A.

2001-05-01

333

Identification of metabolites from liquid chromatography-coulometric array detection profiling: Gas chromatography-mass spectrometry and refractionation provide essential information orthogonal to LC-MS/microNMR.  

PubMed

Liquid chromatography-coulometric array detection (LC-EC) is a sensitive, quantitative, and robust metabolomics profiling tool that complements the commonly used mass spectrometry (MS) and nuclear magnetic resonance (NMR)-based approaches. However, LC-EC provides little structural information. We recently demonstrated a workflow for the structural characterization of metabolites detected by LC-EC profiling combined with LC-electrospray ionization (ESI)-MS and microNMR. This methodology is now extended to include (i) gas chromatography (GC)-electron ionization (EI)-MS analysis to fill structural gaps left by LC-ESI-MS and NMR and (ii) secondary fractionation of LC-collected fractions containing multiple coeluting analytes. GC-EI-MS spectra have more informative fragment ions that are reproducible for database searches. Secondary fractionation provides enhanced metabolite characterization by reducing spectral overlap in NMR and ion suppression in LC-ESI-MS. The need for these additional methods in the analysis of the broad chemical classes and concentration ranges found in plasma is illustrated with discussion of four specific examples: (i) characterization of compounds for which one or more of the detectors is insensitive (e.g., positional isomers in LC-MS, the direct detection of carboxylic groups and sulfonic groups in (1)H NMR, or nonvolatile species in GC-MS), (ii) detection of labile compounds, (iii) resolution of closely eluting and/or coeluting compounds, and (iv) the capability to harness structural similarities common in many biologically related, LC-EC-detectable compounds. PMID:24657819

Gathungu, Rose M; Bird, Susan S; Sheldon, Diane P; Kautz, Roger; Vouros, Paul; Matson, Wayne R; Kristal, Bruce S

2014-06-01

334

Measurement of non-enteric emission fluxes of volatile fatty acids from a California dairy by solid phase micro-extraction with gas chromatography/mass spectrometry  

NASA Astrophysics Data System (ADS)

Dairies are a major source of volatile organic compounds (VOCs) in California's San Joaquin Valley; a region that experiences high ozone levels during summer. Short-chain carboxylic acids, or volatile fatty acids (VFAs), are believed to make up a large fraction of VOC emissions from these facilities, although there are few studies to substantiate this. In this work, a method using a flux chamber coupled to solid phase micro-extraction (SPME) fibers followed by analysis using gas chromatography/mass spectrometry was developed to quantify emissions of six VFAs (acetic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid and 3-methyl butanoic acid) from non-enteric sources. The technique was then used to quantify VFA fluxes from a small dairy located on the campus of California State University Fresno. Both animal feed and animal waste are found to be major sources of VFAs, with acetic acid contributing 70-90% of emissions from the sources tested. Measured total acid fluxes during spring (with an average temperature of 20 °C) were 1.84 ± 0.01, 1.06 ± 0.08, (1.3 ± 0.5) × 10 -2, (1.7 ± 0.2) × 10 -2 and (1.2 ± 0.5) × 10 -2 g m -2 h -1 from silage, total mixed rations, flushing lane, open lot and lagoon sources, respectively. VFA emissions from the sources tested total 390 ± 80 g h -1. The data indicate high fluxes of VFAs from dairy facilities, but differences in the design and operation of dairies in the San Joaquin Valley as well as seasonal variations mean that additional measurements must be made to accurately determine emissions inventories for the region.

Alanis, Phillip; Sorenson, Mark; Beene, Matt; Krauter, Charles; Shamp, Brian; Hasson, Alam S.

335

Elemental analyses of hypervelocity micro-particle impact sites on interplanetary dust experiment sensor surfaces  

Microsoft Academic Search

The Interplanetary Dust Experiment (IDE) had over 450 electrically active ultra-high purity metal-oxide-silicon impact detectors located on the six primary sides of the Long Duration Exposure Facility (LDEF). Hypervelocity micro-particles that struck the active sensors with enough energy to breakdown the 0.4 to 1.0 micron thick SiO2 insulator layer separating the silicon base (the negative electrode), and the 1000 A

Charles G. Simon; J. L. Hunter; D. P. Griffis; V. Misra; D. R. Ricks; Jim J. Wortman

1992-01-01

336

Micro-machined resonator  

DOEpatents

A micro-machined resonator, typically quartz, with upper and lower micro-machinable support members, or covers, having etched wells which may be lined with conductive electrode material, between the support members is a quartz resonator having an energy trapping quartz mesa capacitively coupled to the electrode through a diaphragm; the quartz resonator is supported by either micro-machined cantilever springs or by thin layers extending over the surfaces of the support. If the diaphragm is rigid, clock applications are available, and if the diaphragm is resilient, then transducer applications can be achieved. Either the thin support layers or the conductive electrode material can be integral with the diaphragm. In any event, the covers are bonded to form a hermetic seal and the interior volume may be filled with a gas or may be evacuated. In addition, one or both of the covers may include oscillator and interface circuitry for the resonator.

Godshall, Ned A. (Albuquerque, NM); Koehler, Dale R. (Albuquerque, NM); Liang, Alan Y. (Albuquerque, NM); Smith, Bradley K. (Albuquerque, NM)

1993-01-01

337

Self-assembly micro optical filter  

NASA Astrophysics Data System (ADS)

Optical communication and sensor industry face critical challenges in manufacturing for system integration. Due to the assembly complexity and integration platform variety, micro optical components require costly alignment and assembly procedures, in which many required manual efforts. Consequently, self-assembly device architectures have become a great interest and could provide major advantages over the conventional optical devices. In this paper, we discussed a self-assembly integration platform for micro optical components. To demonstrate the adaptability and flexibility of the proposed optical device architectures, we chose a commercially available MEMS fabrication foundry service - MUMPs (Multi-User MEMS Process). In this work, polysilicon layers of MUMPS are used as the 3-D structural material for construction of micro component framework and actuators. However, because the polysilicon has high absorption in the visible and near infrared wavelength ranges, it is not suitable for optical interaction. To demonstrate the required optical performance, hybrid integration of materials was proposed and implemented. Organic compound materials were applied on the silicon-based framework to form the required optical interfaces. Organic compounds provide good optical transparency, flexibility to form filters or lens and inexpensive manufacturing procedures. In this paper, we have demonstrated a micro optical filter integrated with self-assembly structures. We will discuss the self-assembly mechanism, optical filter designs, fabrication issues and results.

Zhang, Ping; Le, Kevin; Malalur-Nagaraja-Rao, Smitha; Hsu, Lun-Chen; Chiao, J.-C.

2006-01-01

338

Liquid-crystal-on-silicon-based optical add/drop multiplexer for orbital-angular-momentum-multiplexed optical links.  

PubMed

We designed an optical add/drop multiplexer for orbital-angular-momentum (OAM)-multiplexed data links by taking advantage of the ring-shaped intensity profile of OAM beams. We demonstrated adding/dropping a single OAM beam from three multiplexed OAM beams using liquid-crystal-on-silicon-based diffraction optical elements. For multiplexed OAM beams carrying 100 Gbit/s quadrature phase-shift-keying data, a power penalty of <2 dB is observed to achieve a bit-error rate of 2.0×10(-3) for each channel of the add/drop multiplexer. PMID:24281530

Huang, Hao; Yue, Yang; Yan, Yan; Ahmed, Nisar; Ren, Yongxiong; Tur, Moshe; Willner, Alan E

2013-12-01

339

Preparation of 2,3-Disubstituted Indoles by Sequential Larock Heteroannulation and Silicon-Based Cross-Coupling Reactions  

PubMed Central

A simple and convergent synthesis of 2,3-disubstituted indoles has been developed using a sequential Larock indole synthesis and silicon-based, cross-coupling reaction. Substituted 2-iodoanilines reacted with an alkynyldimethylsilyl tert-butyl ether to afford indole-2-silanols under the Larock heteroannulation conditions after hydrolysis. The corresponding sodium 2-indolylsilanolate salts successfully engaged in cross-coupling with aryl bromides and chlorides to afford multi-substituted indoles. The development of an alkynyldimethylsilyl tert-butyl ether as a masked silanol equivalent enabled a smooth heteroannulation process and the identification of a suitable catalyst/ligand combination provided for a facile cross-coupling reaction.

Baird, John D.

2009-01-01

340

Gas Producing Micro-Reaction  

NSDL National Science Digital Library

In this chemistry activity, learners use common chemicals and metals to examine reactions that produce gaseous substances. Learners will identify the gases produced and write a balanced equation for each reaction. Use this activity to also introduce learners to single displacement and double displacement reactions, two types of chemical reactions.

House, The S.

2014-01-28

341

Design and evaluation of a low nitrogen oxides natural gas-fired conical wire-mesh duct burner for a micro-cogeneration unit  

NASA Astrophysics Data System (ADS)

A novel low NOx conical wire-mesh duct burner was designed, built and tested in the present research. This thesis documents the design process and the in-depth evaluation of this novel duct burner for the development of a more efficient micro-cogeneration unit. This duct burner provides the thermal energy necessary to raise the microturbine exhaust gases temperature to increase the heat recovery capability. The duct burner implements both lean-premixed and surface combustion techniques to achieve low NOx and CO emissions. The design of the duct burner was supported by a qualitative flow visualization study for the duct burner premixer to provide insight into the premixer flow field (mixing process). Different premixer geometries were used to control the homogeneity of the fuel-oxidant mixture at the exit of the duct burner premixer. Laser sheet illumination (LSI) technique was used to capture images of the mixing process, for each configuration studied. A quasi-quantitative analysis technique was developed to rank the different premixer geometries in terms of mixing effectiveness. The premixer geometries that provided better mixing were selected and used for the combustion tests. The full-scale gas-fired duct burner was installed in the exhaust duct of a micro-cogeneration unit for the evaluation. Three wire-mesh burners with different pressure drops were used. Each burner has a conical shape made from FeCrAL alloy mat and was designed based on a heat release per unit area of 2500 kW/m2 and a total heat release of 240kW at 100 percent excess air. The local momentum of the gaseous mixture introduced through the wire-mesh was adjusted so that the flame stabilized outside the burner mesh (surface combustion). Cold flow tests (i.e., the duct burner was off, but the microturbine was running) were conducted to measure the effect of different duct burner geometrical parameters on flow split between the combustion zone and the bypass channel, and on pressure drop across the duct burner. A considerable amount of detailed parametric experimental data was collected to investigate the performance characteristics of the duct burner. The variables studied (firing rate, mass flow ratio, conical burner pressure drop, blockage ratio, conical burner shield length, premixer geometry and inlet conditions) were all found to play an important role on emissions (NOx and CO), overall duct burner pressure drop and flame stability. The range of firing rates at which surface combustion was maintained for the duct burner was defined by direct observation of the burner surface and monitoring of the temperature in the combustion zone. Flame images were captured for qualitative assessment. The combustion tests results presented in this thesis proved that the design procedures that were implemented to design this novel microturbine conical wire-mesh duct burner were successful. During the course of the combustion tests, the duct burner displayed stable, low emissions operation throughout the surface firing rate range of 148 kW to 328 kW (1574 kW/m 2 to 3489 kW/m2). Emissions of less than 5 ppm (corrected to 15 percent 02) for NOx and CO emissions were recorded, while the duct burner successfully raised the microturbine exhaust gases temperature from about 227°C to as high as 700°C. The overall duct burner pressure drop throughout was consistently below the design limit of 249 Pa.

Ramadan, Omar Barka Ab

342

Micro-structured electrode arrays  

Microsoft Academic Search

Micro-structured electrode (MSE) arrays allow to generate large-area uniform glow discharges over a wide pressure range up to atmospheric pressure. The electrode dimensions in the ?m-range realized by means of modern micro-machining and galvanic techniques are small enough to generate sufficiently high electric field strengths to ignite gas discharges applying only moderate radio frequency (RF, 13.56MHz) voltages (80–390V in Ne,

Lutz Baars-Hibbe; Christian Schrader; Philipp Sichler; Thorben Cordes; Karl-Heinz Gericke; Stephanus Büttgenbach; Siegfried Draeger

2004-01-01

343

Micro-Analysis of Gases  

Microsoft Academic Search

KROGH'S micro-analysis method as originally described,1 for small bubbles of from 50 to 100 cubic millimetres and containing oxygen, carbon dioxide, and nitrogen, is limited to bubbles which have been in contact with a fluid, because the lower cup of the micro-apparatus must be filled with some of the same fluid with which the gas bubble has been in equilibrium,

J. Argyll Campbell

1932-01-01

344

Biocompatibility Assessment of Si-based Nano- and Micro-particles  

PubMed Central

Silicon is one of the most abundant chemical elements found on the Earth. Due to its unique chemical and physical properties, silicon based materials and their oxides (e.g. silica) have been used in several industries such as building and construction, electronics, food industry, consumer products and biomedical engineering/medicine. This review summarizes studies on effects of silicon and silica nano- and micro-particles on cells and organs following four main exposure routes, namely, intravenous, pulmonary, dermal and oral. Further, possible genotoxic effects of silica based nanoparticles are discussed. The review concludes with an outlook on improving and standardizing biocompatibility assessment for nano- and micro-particles.

Jaganathan, Hamsa; Godin, Biana

2012-01-01

345

Biocompatibility assessment of Si-based nano- and micro-particles.  

PubMed

Silicon is one of the most abundant chemical elements found on the Earth. Due to its unique chemical and physical properties, silicon based materials and their oxides (e.g. silica) have been used in several industries such as building and construction, electronics, food industry, consumer products and biomedical engineering/medicine. This review summarizes studies on effects of silicon and silica nano- and micro-particles on cells and organs following four main exposure routes, namely, intravenous, pulmonary, dermal and oral. Further, possible genotoxic effects of silica based nanoparticles are discussed. The review concludes with an outlook on improving and standardizing biocompatibility assessment for nano- and micro-particles. PMID:22634160

Jaganathan, Hamsa; Godin, Biana

2012-12-01

346

Formation of Silicon-Based Thin Films Prepared by Catalytic Chemical Vapor Deposition (Cat-CVD) Method  

NASA Astrophysics Data System (ADS)

This paper is a review of the catalytic chemical vapor deposition (Cat-CVD) method and properties of silicon-based thin films, such as amorphous-silicon (a-Si), polycrystalline-silicon (p-Si) and silicon nitride (SiNx) films, prepared by the Cat-CVD method. In the Cat-CVD method, also known as the hot-wire CVD (HWCVD) method, deposition gases are decomposed by catalytic cracking reactions with a heated catalyzer placed near the substrates, so that films are deposited at low substrate temperatures around 300°C without any help from the plasma. After explaining the deposition system and deposition mechanism, the properties of Cat-CVD a-Si, p-Si and SiNx films are described and the results are compared with those obtained by the conventional plasma CVD (PCVD) method. The superiority of the Cat-CVD method over the PCVD method is demonstrated.

Matsumura, Hideki

1998-06-01

347

Study of acoustic wave behavior in silicon-based one-dimensional phononic-crystal plates using harmony response analysis  

NASA Astrophysics Data System (ADS)

We promote an efficient method named harmony response analysis (HRA) as a comparison with transient response analysis and supercell plane wave expansion (supercell PWE) to study the behavior of Lamb wave in silicon-based one-dimensional composite plates. To implement HRA for dealing with Lamb waves in phononic-crystal plates, the viscous-spring artificial boundaries are employed to eliminate the boundary reflection in maximum. With the calculation of displacement field, the propagations of elastic waves under different frequency loads (inside/outside the completed band gap) are investigated in details. The method is then applied in plates both with and without substrate. We further study the plates with quasiperiodicity (generalized Fibonacci systems and double-period system) and investigate the change in band gaps induced by the quasiperiodicity.

Zhu, Xuefeng; Xu, Tao; Liu, Shengchun; Cheng, Jianchun

2009-11-01

348

Development of dielectric and amorphous-silicon-based thin film coatings for room- and cryogenic temperature applications  

NASA Astrophysics Data System (ADS)

This paper reports on the development of dielectric and amorphous silicon-based thin film stacks for applications at room and liquid nitrogen (LN) cryogenic temperatures. The deposition process was performed using assisted energetic evaporation processes such as Reactive Low Voltage Ion Plating (RLVIP) and Ion Assisted Deposition (IAD). Dielectric coatings produced by RLVIP exhibited fairly good stability at LN temperature. Indeed, as compared to room temperature, a spectral shift of ??0.5 = -2.9 nm at half maximum was obtained for a 3-cavity bandpass filter centered at 1570 nm. Amorphous silicon and silicon dioxide stacks deposited by IAD processes were tested for optical applications. Amorphous silicon thin films showed good mechanical stability at LN temperature. The influence of deposition parameters and operating temperature on the electrical, mechanical and optical properties of amorphous Si films was investigated.

Poirier, Michel; Ilias, Samir; Thibault, Simon; Topart, Patrice; Jerominek, Hubert

2004-02-01

349

Oxidation resistant high temperature thermal cycling resistant coatings on silicon-based substrates and process for the production thereof  

DOEpatents

An oxidation resistant, high temperature thermal cycling resistant coated ceramic article for ceramic heat engine applications is disclosed. The substrate is a silicon-based material, i.e. a silicon nitride- or silicon carbide-based monolithic or composite material. The coating is a graded coating of at least two layers: an intermediate AlN or Al[sub x]N[sub y]O[sub z] layer and an aluminum oxide or zirconium oxide outer layer. The composition of the coating changes gradually from that of the substrate to that of the AlN or Al[sub x]N[sub y]O[sub z] layer and further to the composition of the aluminum oxide or zirconium oxide outer layer. Other layers may be deposited over the aluminum oxide layer. A CVD process for depositing the graded coating on the substrate is also disclosed.

Sarin, V.K.

1990-08-21

350

Oxidation resistant high temperature thermal cycling resistant coatings on silicon-based substrates and process for the production thereof  

DOEpatents

An oxidation resistant, high temperature thermal cycling resistant coated ceramic article for ceramic heat engine applications. The substrate is a silicon-based material, i.e. a silicon nitride- or silicon carbide-based monolithic or composite material. The coating is a graded coating of at least two layers: an intermediate AlN or Al.sub.x N.sub.y O.sub.z layer and an aluminum oxide or zirconium oxide outer layer. The composition of the coating changes gradually from that of the substrate to that of the AlN or Al.sub.x N.sub.y O.sub.z layer and further to the composition of the aluminum oxide or zirconium oxide outer layer. Other layers may be deposited over the aluminum oxide layer. A CVD process for depositing the graded coating on the substrate is also disclosed.

Sarin, Vinod K. (Lexington, MA)

1990-01-01

351

DNA Lesions in Medaka (O. latipes): Development of a Micro-Method for Tissue Analysis Using Gas Chromatography-Mass Spectrometry.  

National Technical Information Service (NTIS)

We have reached a point where substantial reductions have been made in the amount of tissue required for GC-MS analysis. In the future, we will analyze the tissues from a number of normal and exposed organisms using the micro method to hopefully validate ...

D. C. Malins

1993-01-01

352

Forensic analysis of a single particle of partially burnt gunpowder by solid phase micro-extraction–gas chromatography-nitrogen phosphorus detector  

Microsoft Academic Search

Solid phase micro-extraction (SPME) was adopted to extract organic gun shot residues (OGSRs) from a single particle of partially burnt gunpowder. The partially burnt particle samples were collected from gun shot residue (GSR) deposited near the target areas. OGSRs, such as diphenylamine (DPA), methyl centralite (MC), ethyl centralite (EC), from only one single particle of partially burnt gunpowder were successfully

Garrett Lee Burleson; Brittney Gonzalez; Kelsie Simons; Jorn C. C. Yu

2009-01-01

353

Local Heating of Discrete Droplets Using Magnetic Porous Silicon-Based Photonic Crystals  

PubMed Central

This paper describes a method for local heating of discrete micro-liter scale liquid droplets. The droplets are covered with magnetic porous Si microparticles, and heating is achieved by application of an external alternating electromagnetic field. The magnetic porous Si microparticles consist of two layers: the top layer contains a photonic code and it is hydrophobic, with surface-grafted dodecyl moieties. The bottom layer consists of a hydrophilic Si oxide host layer that is infused with Fe3O4 nanoparticles. The amphiphilic microparticles spontaneously align at the interface of a water droplet immersed in mineral oil, allowing manipulation of the droplets by application of a magnetic field. Application of an oscillating magnetic field (338 kHz, 18A RMS current in a coil surrounding the experiment) generates heat in the superparamagnetic particles that can raise the temperature of the enclosed water droplet to >80 °C within 5 min. A simple microfluidics application is demonstrated: combining complementary DNA strands contained in separate droplets and then thermally inducing dehybridization of the conjugate. The complementary oligonucleotides were conjugated with the cyanine dye fluorophores Cy3 and Cy5 to quantify the melting/re-binding reaction by fluorescence resonance energy transfer (FRET). The magnetic porous Si microparticles were prepared as photonic crystals, containing spectral codes that allowed the identification of the droplets by reflectivity spectroscopy. The technique demonstrates the feasibility of tagging, manipulating, and heating small volumes of liquids without the use of conventional microfluidic channel and heating systems.

Park, Ji-Ho; Derfus, Austin M.; Segal, Ester; Vecchio, Kenneth S.; Bhatia, Sangeeta N.; Sailor, Michael J.

2012-01-01

354

Direct quantitative analysis of phthalate esters as micro-contaminants in cleanroom air and wafer surfaces by auto-thermal desorption–gas chromatography–mass spectrometry  

Microsoft Academic Search

This study established an analytical method for the trace analyses of two phthalate esters, including diethyl phthalate (DEP) and di-n-butyl phthalate (DBP), known as the major constituents of cleanroom micro-contamination detrimental to the reliability of semiconductor devices. Using thermal desorption coupled with a GC–MS system, standard tubes were prepared by delivering liquid standards pre-vaporized by a quasi-vaporizer into Tenax GR

Yuhao Kang; Walter Den; Hsunling Bai; Fu-Hsiang Ko

2005-01-01

355

Design and evaluation of a low nitrogen oxides natural gas-fired conical wire-mesh duct burner for a micro-cogeneration unit  

Microsoft Academic Search

A novel low NOx conical wire-mesh duct burner was designed, built and tested in the present research. This thesis documents the design process and the in-depth evaluation of this novel duct burner for the development of a more efficient micro-cogeneration unit. This duct burner provides the thermal energy necessary to raise the microturbine exhaust gases temperature to increase the heat

Omar Barka Ab Ramadan

2008-01-01

356

Application of porous membrane protected micro-solid-phase-extraction combined with gas chromatography–mass spectrometry for the determination of estrogens in ovarian cyst fluid samples  

Microsoft Academic Search

A cost effective and environmentally friendly extraction technique using porous membrane protected micro-solid phase extraction (?-SPE) is described for the extraction of estrogens in cyst fluid samples obtained from cancer patients. A sorbent (ethylsilane (C2) modified silica) (20mg) was packed in a porous polypropylene envelope (2cm×1.5cm) whose edges were heat sealed to secure the contents. The ?-SPE device was conditioned

Sivarajan Kanimozhi; Chanbasha Basheer; Kothandaraman Narasimhan; Lin Liu; Stephen Koh; Feng Xue; Mahesh Choolani; Hian Kee Lee

2011-01-01

357

Isoporous micro/nanoengineered membranes.  

PubMed

Isoporous membranes are versatile structures with numerous potential and realized applications in various fields of science such as micro/nanofiltration, cell separation and harvesting, controlled drug delivery, optics, gas separation, and chromatography. Recent advances in micro/nanofabrication techniques and material synthesis provide novel methods toward controlling the detailed microstructure of membrane materials, allowing fabrication of membranes with well-defined pore size and shape. This review summarizes the current state-of-the-art for isoporous membrane fabrication using different techniques, including microfabrication, anodization, and advanced material synthesis. Various applications of isoporous membranes, such as protein filtration, pathogen isolation, cell harvesting, biosensing, and drug delivery, are also presented. PMID:23442009

Warkiani, Majid Ebrahimi; Bhagat, Ali Asgar S; Khoo, Bee Luan; Han, Jongyoon; Lim, Chwee Teck; Gong, Hai Qing; Fane, Anthony Gordon

2013-03-26

358

Direct quantitative analysis of phthalate esters as micro-contaminants in cleanroom air and wafer surfaces by auto-thermal desorption--gas chromatography--mass spectrometry.  

PubMed

This study established an analytical method for the trace analyses of two phthalate esters, including diethyl phthalate (DEP) and di-n-butyl phthalate (DBP), known as the major constituents of cleanroom micro-contamination detrimental to the reliability of semiconductor devices. Using thermal desorption coupled with a GC-MS system, standard tubes were prepared by delivering liquid standards pre-vaporized by a quasi-vaporizer into Tenax GR tubes for calibration. This method was capable of achieving detection limits of 0.05 microg m(-3) for 0.1 m3 air samples and 0.03 ng cm(-2) for 150-mm wafer surface density. Actual samples collected from a semiconductor cleanroom showed that the concentration of DBP in a polypropylene wafer box (0.45 microg m(-3)) was nearly four times higher than that in the cleanroom environment (0.12 microg m(-3)). The surface contamination of DBP was 0.67 ng cm(-2) for a wafer stored in the wafer box for 24 h. Furthermore, among the three types of heat-resistant O-ring materials tested, Kalrez was found to be particularly suitable for high-temperature processes in semiconductor cleanrooms due to their low emissions of organic vapors. This analytical procedure should serve as an effective monitoring method for the organic micro-contamination in cleanroom environments. PMID:15861797

Kang, Yuhao; Den, Walter; Bai, Hsunling; Ko, Fu-Hsiang

2005-04-01

359

An algorithm for selection and design of hybrid power supplies for MEMS with a case study of a micro-gas chromatograph system  

NASA Astrophysics Data System (ADS)

The Wireless Integrated Microsystems (WIMS)-environmental monitor testbed (EMT) is a multi-component microelectromechanical system (MEMS), incorporating complementary metal oxide semiconductor (CMOS) materials for high-precision circuits used for integrated sensors such as micro-g accelerometers, micro-gyroscopes, and pressure sensors. The WIMS-EMT duty cycle, like many autonomous MEMS systems, has low-power standby periods for sensing, and high-power pulses for R/F transmission and reception. In this paper, we present results of three strategies for providing power to this system, including (1) specification of a single, aggregate power supply, resulting in a single battery electrochemistry and cell size; (2) specification of several power supplies, by a priori division of power sources by power range; and (3) specification of an arbitrary number of power "bundles," based on available space in the device. The second approach provided the best results of mass (0.032 kg) and volume (0.028 L) among the three approaches. The second and third approaches provided the best battery lifetime results; both systems produced lifetimes in excess of 2E3 h. Future work will incorporate CMOS operational amplifier (op-amp) technologies to accommodate large voltage fluxes in many MEMS devices, and implementation of our approaches into a user-friendly code.

Cook, K. A.; Sastry, A. M.

360

High volume methane gas hydrate deposits in fine grained sediments from the Krishna-Godavari Basin: Analysis from Micro CT scanning  

NASA Astrophysics Data System (ADS)

The Indian National Gas Hydrate Program (NGHP) Expedition 1, of 2006, investigated several methane gas hydrate deposits on the continental shelf around the coast of India. Using pressure coring techniques (HYACINTH and PCS), intact gas-hydrate bearing, fine-grained sediment cores were recovered during the expedition. Once recovered, these cores were rapidly depressurized and submerged in liquid nitrogen, therefore preserving the structure and form of the hydrate within the host sediment. High resolution X-Ray CT scanning was later employed to image the internal structure of the gas hydrate, analyze the trends in vein orientation, and collect volumetric data. A scanning resolution of 0.08mm allowed for a detailed view of the three-dimensional distribution of the hydrate within the sediment from which detailed analysis of vein orientation could be made. Two distinct directions of vein growth were identified in each core section studied, which suggested the presence of a specific stress regime in the Krishna-Godavari basin during hydrate formation. In addition, image segmentation of gas hydrate from the sediment allowed for volumetric analysis of the hydrate content within each core section. Results from this analysis showed that high volumes of gas hydrate, up to approximately 70% of the pore space, were present. This high volume of methane gas hydrate can have a significant impact on the stability of the host sediment if dissociation of the hydrate were to occur in-situ, through the development of excess pore pressure, increase in water content and change in salinity of the host sediment.

Rees, E. V.; Clayton, C.; Priest, J.; Schultheiss, P. J.

2009-12-01

361

Silicon based light emitters utilizing radiation from dislocations; electric field induced shift of the dislocation-related luminescence  

NASA Astrophysics Data System (ADS)

Dislocation rich regions can be controllably formed at a certain location inside a silicon wafer. We studied the light emission properties of such regions located in an electric field of a p-n junction under different excitation conditions. It was found that the luminescence spectra of the dislocations are significantly influenced by the presence of the junction. The dislocation-related luminescence peak position appears red-shifted due to the built-in electric field. A suppression of that field by photo-generation of carriers or by applying a forward bias voltage at the junction leads to a gradual decrease in the energy position of the peaks. The dependence of the peak position on the electric field was found to be a quadratic function, similar to that observed for semiconductor nanostructures. We show that the shift of the peak position is due to the Stark effect on dislocation-related excitonic states. The characteristic constant of the shift, obtained by fitting the data with the quadratic Stark effect equation, was 0.0186 meV/(kV/cm) 2. The observed effect opens new possibilities for integration of a silicon based light emitter, combining the radiation from dislocations with a Stark effect based modulator.

Arguirov, T.; Mchedlidze, T.; Kittler, M.; Reiche, M.; Wilhelm, T.; Hoang, T.; Holleman, J.; Schmitz, J.

2009-05-01

362

Silicon Based System for Single-Nucleotide-Polymorphism Detection: Chip Fabrication and Thermal Characterization of Polymerase Chain Reaction Microchamber  

NASA Astrophysics Data System (ADS)

A single nucleotide polymorphism (SNP) is a difference in the DNA sequence of one nucleotide only. We recently proposed a lab-on-a-chip (LoC) system which has the potentiality of fast, sensitive and highly specific SNP detection. Most of the chip components are silicon based and fabricated within a single process. In this paper, the newly developed fabrication method for the silicon chip is presented. The robust and reliable process allows etching structures on the same chip with very different aspect ratios. The characterization of a crucial component to the LoC SNP detector, the microreactor where DNA amplification is performed, is also detailed. Thanks to innovative design and fabrication methodologies, the microreactor has an excellent thermal isolation from the surrounding silicon substrate. This allows for highly localized temperature control. Furthermore, the microreactor is demonstrated to have rapid heating and cooling rates, allowing for rapid amplification of the target DNA fragments. Successful DNA amplification in the microreactor is demonstrated.

Majeed, Bivragh; Jones, Ben; Tezcan, Deniz S.; Tutunjyan, Nina; Haspeslagh, Luc; Peeters, Sara; Fiorini, Paolo; Beeck, Maaike Op de; Hoof, Chris Van; Hiraoka, Maki; Tanaka, Hiroyuki; Yamashita, Ichiro

2012-04-01

363

Nonlinear distortion of optical pulses by self-produced free carriers in short or highly lossy silicon-based waveguides.  

PubMed

An explicit analytical solution for the asymmetric attenuation of optical pulses by self-produced free carriers in silicon waveguides is derived. It allows us to quantify the pulse distortion and to calculate explicitly the free-carrier density and the nonlinear phase shifts caused by the Kerr effect and by free-carrier refraction. We show that omitting two-photon absorption (TPA) as a cause of attenuation and accounting only for free-carrier absorption (FCA) as done in the derivation appropriately models the pulse propagation in short or highly lossy silicon-based waveguides such as plasmonic waveguides with particular use for high-energy input pulses. Moreover, this formulation is also aimed at serving as a tool in discussing the role of FCA in its competition with TPA when used for continuum generation or pulse compression in low-loss silicon waveguides. We show that sech-shaped intensity pulses maintain their shape independently of the intensity or pulse width and self-induced FCA may act as an ideal limiter on them. Pulse propagation under self-induced free-carrier absorption exhibits some features of superluminal propagation such as fast or even backward travelling. We find that input pulses need to have a sufficiently steep front slope to be compressible at all and illustrate this with the FCA-induced pulse broadening for Lorentzian-shaped input pulses. PMID:23187390

Renner, Hagen

2012-11-01

364

In Vivo Validation of Custom-Designed Silicon-Based Microelectrode Arrays for Long-Term Neural Recording and Stimulation  

PubMed Central

We developed and validated silicon-based neural probes for neural stimulating and recording in long-term implantation in the brain. The probes combine the deep reactive ion etching process and mechanical shaping of their tip region, yielding a mechanically sturdy shank with a sharpened tip to reduce insertion force into the brain and spinal cord, particularly, with multiple shanks in the same array. The arrays’ insertion forces have been quantified in vitro. Five consecutive chronically-implanted devices were fully functional from 3 to 18 months. The microelectrode sites were electroplated with iridium oxide, and the charge injection capacity measurements were performed both in vitro and after implantation in the adult feline brain. The functionality of the chronic array was validated by stimulating in the cochlear nucleus and recording the evoked neuronal activity in the central nucleus of the inferior colliculus. The arrays’ recording quality has also been quantified in vivo with neuronal spike activity recorded up to 566 days after implantation. Histopathology evaluation of neurons and astrocytes using immunohistochemical stains indicated minimal alterations of tissue architecture after chronic implantation.

Manoonkitiwongsa, Panya S.; Wang, Cindy X.; McCreery, Douglas B.

2012-01-01

365

Freeform fabrication of superalloy objects by 3D micro welding  

Microsoft Academic Search

3D Micro welding (3DMW) is a newly developed rapid prototyping method for metals. It is a combination of micro tungsten inert gas (micro-TIG) welding and a layered manufacturing method. The tip of a thin metal wire is melted by a micro-TIG welder to form a small metal bead. By building up metal beads layer by layer under computer control, a

Toshihide Horii; Soshu Kirihara; Yoshinari Miyamoto

2009-01-01

366

Ultrasonic assisted headspace single drop micro-extraction and gas chromatography with nitrogen-phosphorus detector for determination of organophosphorus pesticides in soil.  

PubMed

This work describes optimization of headspace single drop micro-extraction for extraction of five organophosphorus pesticides; thionazin, sulfotep, dimethoate, disulfoton and parathion in soil. Ultrasound has also been used successfully to improve and accelerate the extraction of the analytes from the sample. The optimized extraction performance was obtained when the experimental parameters were set as follows; 3.0 ?L of octanol as extraction solvent, high ionic strength (20% sodium chloride), 1:1 (w/v) sample dilution with water, extraction temperature at 60 °C for 30 min; applying ultrasound and without any pH adjustment. The optimized method was linear over the calibration range (5-200 and 10-300 for different analytes) with limits of detection of 0.1-2.0 ng g(-1). The enrichment factor for OPPs was 1.4-12.7 and the method was also reproducible with the relative standard deviations (RSD%) of 2.1-6.9%. PMID:23498130

Salemi, Amir; Rasoolzadeh, Reihaneh; Nejad, Massumeh Mohebbi; Vosough, Maryam

2013-03-26

367

Critical evaluation of ex vivo restoration of carious equine maxillary cheek teeth infundibulae following high-pressure gas and micro-particle abrasion.  

PubMed

Infundibular caries of the equine maxillary cheek teeth is an important disorder that can lead to dental fracture or apical infection. Treatment by removing food debris and carious dental tissue from affected infundibulae using high-pressure abrasion with aluminium hydroxide micro-particles, followed by filling the cleaned defect with endodontic restorative materials is a recommended treatment. However, although anecdotally considered a successful treatment option, there is currently no objective evidence to support this claim. Forty maxillary cheek teeth (CT) that contained 55 infundibulae with caries (mainly grade 2) were extracted post-mortem from 21 adult horses. Five of the CT were sectioned prior to treatment to facilitate visual examination of the carious infundibulae. The remaining carious infundibulae were cleaned using high-pressure abrasion with aluminium hydroxide particles and five CT were sectioned to assess the efficacy of this cleaning process. The remaining 30 CT containing 39 carious infundibulae were then filled with a composite restorative material. The efficacy of this restoration was assessed by computed tomography imaging followed by direct visual examination after sectioning the teeth. Only 46% (18/39) of restored infundibulae, all with shallow (mean 9.6?mm deep) defects, were fully cleaned of food debris and carious material, and filled with restorative material to their full depth. Of these 18, 11 had peripheral defects around the restoration, leaving just 18% (7/39) of restorations without any gross defects. The remaining 54% (21/39) of infundibulae (mean depth of infundibular caries defect, 18.3?mm) still contained food debris and/or carious material in more apical locations, with infundibulae with the deepest caries defects being the least effectively cleaned. The findings of this study indicate that high-pressure micro-particle abrasion is only effective in cleaning food debris from shallow, carious CT infundibulae and consequently, the majority of subsequent infundibular restorations are imperfect. PMID:24792205

Dixon, P M; Savill, D; Horbyl, A; Reardon, R J M; Liuti, T

2014-06-01

368

Miniaturized GC\\/MS instrumentation for in situ measurements: micro gas chromatography coupled with miniature quadrupole array and Paul ion trap mass spectrometers  

Microsoft Academic Search

Miniaturized chemical instrumentation is needed for in situ measurements in planetary exploration and other spaceflight applications where factors such as reduction in payload requirements and enhanced robustness are important. In response to this need, we are continuing to develop miniaturized GC\\/MS instrumentation which combines chemical separations by gas chromatography (GC) with mass spectrometry (MS) to provide positive identification of chemical

Paul M. Holland; Ara Chutjian; Murray R. Darrach; Otto J. Orient

2003-01-01

369

iHWG-?NIR: a miniaturised near-infrared gas sensor based on substrate-integrated hollow waveguides coupled to a micro-NIR-spectrophotometer.  

PubMed

A miniaturised gas analyser is described and evaluated based on the use of a substrate-integrated hollow waveguide (iHWG) coupled to a microsized near-infrared spectrophotometer comprising a linear variable filter and an array of InGaAs detectors. This gas sensing system was applied to analyse surrogate samples of natural fuel gas containing methane, ethane, propane and butane, quantified by using multivariate regression models based on partial least square (PLS) algorithms and Savitzky-Golay 1(st) derivative data preprocessing. The external validation of the obtained models reveals root mean square errors of prediction of 0.37, 0.36, 0.67 and 0.37% (v/v), for methane, ethane, propane and butane, respectively. The developed sensing system provides particularly rapid response times upon composition changes of the gaseous sample (approximately 2 s) due the minute volume of the iHWG-based measurement cell. The sensing system developed in this study is fully portable with a hand-held sized analyser footprint, and thus ideally suited for field analysis. Last but not least, the obtained results corroborate the potential of NIR-iHWG analysers for monitoring the quality of natural gas and petrochemical gaseous products. PMID:24867650

Rohwedder, J J R; Pasquini, C; Fortes, P R; Raimundo, I M; Wilk, A; Mizaikoff, B

2014-06-16

370

Microstructure of amorphous-silicon-based solar cell materials by small-angle x-ray scattering. Annual subcontract report, 6 April 1994--5 April 1995  

SciTech Connect

The general objective of this research is to provide detailed microstructural information on the amorphous-silicon-based, thin-film materials under development for improved multijunction solar cells. The experimental technique used is small-angle x-ray scattering (SAXS) providing microstructural data on microvoid fractions, sizes, shapes, and their preferred orientations. Other microstructural features such as alloy segregation, hydrogen-rich clusters and alloy short-range order are probed.

Williamson, D.L. [Colorado School of Mines, Golden, CO (United States)

1995-08-01

371

The Response of the silicon-based Linear Energy Transfer Spectrometer (RRMD-III) to Protons from 1 to 70 MeV  

Microsoft Academic Search

Experiments have been performed to measure the response of the silicon-based linear energy transfer (LET) spectrometer (RRMD-III) to protons with energies ranging from 1 to 70 MeV. The beam energies incident upon RRMD-III were obtained using plastic polycarbonate degraders with mono-energetic proton beams that were extracted at 70, 40 and 25 MeV from a cyclotron. The energy loss in the

Kazuhiro Terasawa; Thomas B. Borak; Tadayoshi Doke; Tetsuhito Fuse; Ken-ichiro Hara; Jun Kikuchi; Hisashi Kitamura; Satoshi Suzuki; Yukio Uchihori

2005-01-01

372

Design of on-chip Transient Voltage Suppressor in a silicon-based transceiver IC to meet IEC system-level ESD specification  

Microsoft Academic Search

The on-chip Transient Voltage Suppressor (TVS) embedded in the silicon based transceiver IC has been proposed in this paper by using 0.8 ?m Bipolar-CMOS-DMOS (BCD) process. The structure of the on-chip TVS is a high voltage Dual Silicon-Controlled-Rectifier (DSCR) with ±19V of high holding voltage (Vh) under the evaluation of 100ns pulse width of the Transmission Line Pulsing (TLP) system.

Ryan Hsin-Chin Jiang; Tang-Kuei Tseng; Chi-Hao Chen; Che-Hao Chuang

2011-01-01

373

Preparation and characterisation of silicone-based coatings filled with carbon nanotubes and natural sepiolite and their application as marine fouling-release coatings  

Microsoft Academic Search

This article reports on the preparation and partial characterisation of silicone-based coatings filled with low levels of either synthetic multiwall carbon nanotubes (MWCNTs) or natural sepiolite (NS). The antifouling and fouling-release properties of these coatings were explored through laboratory assays involving representative soft-fouling (Ulva) and hard-fouling (Balanus) organisms. The bulk mechanical properties of the coatings appeared unchanged by the addition

Alexandre Beigbeder; Philippe Degee; Sheelagh L. Conlan; Robert J. Mutton; Anthony S. Clare; Michala E. Pettitt; Maureen E. Callow; James A. Callow; Philippe Dubois

2008-01-01

374

Silicon-based anti-reflective spin-on hardmask materials for 45 nm pattern of immersion ArF lithography  

Microsoft Academic Search

In current semiconductor manufacturing processes, hardmasks have become more prevalent in patterning of small features. A silicon-containing hardmask, which can be spun onto wafers, is desirable in terms of mass production throughput and cost of ownership. Previously, we reported a paper on silicon-based anti-reflective spin-on hardmask materials for 193 nm lithography. In this paper, hardmask materials for 45 nm pattern

Sang Kyun Kim; Hyeon Mo Cho; Sang Ran Koh; Mi-young Kim; Hui Chan Yoon; Yong-jin Chung; Jong Seob Kim; Tuwon Chang

2008-01-01

375

An automated method for the analysis of phenolic acids in plasma based on ion-pairing micro-extraction coupled on-line to gas chromatography/mass spectrometry with in-liner derivatisation.  

PubMed

A new method is presented for the analysis of phenolic acids in plasma based on ion-pairing 'Micro-extraction in packed sorbent' (MEPS) coupled on-line to in-liner derivatisation-gas chromatography-mass spectrometry (GC-MS). The ion-pairing reagent served a dual purpose. It was used both to improve extraction yields of the more polar analytes and as the methyl donor in the automated in-liner derivatisation method. In this way, a fully automated procedure for the extraction, derivatisation and injection of a wide range of phenolic acids in plasma samples has been obtained. An extensive optimisation of the extraction and derivatisation procedure has been performed. The entire method showed excellent repeatabilities of under 10% and linearities of 0.99 or better for all phenolic acids. The limits of detection of the optimised method for the majority of phenolic acids were 10ng/mL or lower with three phenolic acids having less-favourable detection limits of around 100 ng/mL. Finally, the newly developed method has been applied in a human intervention trial in which the bioavailability of polyphenols from wine and tea was studied. Forty plasma samples could be analysed within 24h in a fully automated method including sample extraction, derivatisation and gas chromatographic analysis. PMID:22099223

Peters, Sonja; Kaal, Erwin; Horsting, Iwan; Janssen, Hans-Gerd

2012-02-24

376

Development, validation and application of a method to analyze phenols in water samples by solid phase micro extraction-gas chromatography-flame ionization detector  

Microsoft Academic Search

In this work the development, validation and application of method using Solid Phase Microexctration (SPME) for the analyses of five pollutants (phenol, 2-nitrophenol, 2,4-dimethylphenol, 2,4-dichlorophenol and 4-chloro, 3-methyl phenol) in supplying water, using gas chromatography (GC) with flame ionization detector (FID) is described. The optimal conditions obtained for SPME were: fiber type: Poliacrylate (PA); extraction time: 40 minutes; extraction temperature:

Fernando M. Lanças; Igor R. B. Olivares; Priscila M. Alves

2007-01-01

377

Determination of malondialdehyde in human blood by headspace-solid phase micro-extraction gas chromatography–mass spectrometry after derivatization with 2,2,2-trifluoroethylhydrazine  

Microsoft Academic Search

Malondialdehyde (MDA) has been proposed as a useful biomarker of lipoperoxidation in biological samples, and more developed analytical methods are necessary. A simple and sensitive gas chromatography–mass spectrometry (HS-SPME-GC–MS) was described for the determination of malondialdehyde (MDA) in blood. Acetone-d6 was used as internal standard. MDA and acetone d6 in blood reacted for 40min at 50°C with 2,2,2-trifluoroethylhydrazine in headspace

Ho-Sang Shin

2009-01-01

378

Improved determination of flavour compounds in butter by solid-phase (micro)extraction and comprehensive two-dimensional gas chromatography  

Microsoft Academic Search

The practicability and potential of comprehensive two-dimensional gas chromatography (GC×GC) coupled to both conventional flame ionisation (FID) and time-of-flight mass spectrometric (TOF-MS) detection, were compared with those of conventional one-dimensional (1D) GC, with the determination of flavour compounds in butter as an application. For polar flavour compounds, which were collected from the aqueous fraction of butter by means of solid-phase

Mohamed Adahchour; Jaap Wiewel; Ramon Verdel; René J. J. Vreuls; Udo A. Th. Brinkman

2005-01-01

379

A method to detect diphenylamine contamination of apple fruit and storages using headspace solid phase micro-extraction and gas chromatography/mass spectroscopy.  

PubMed

Analysis of headspace concentrations of diphenylamine using solid phase micro-extraction (SPME) was examined for its suitability to detect DPA contamination and off-gassing in apple (Malus domestica) fruit, storage rooms and storage materials. Four SPME fibre coatings including polydimethylsiloxane (PDMS, 100 ?m), PDMS/divinylbenzene (PDMS/DVB), Polyacrylate (PA) and PDMS 7 ?m were evaluated. The average limits of detection and of quantification for head space DPA ranged from 0.13 to 0.72 ?g L(-1) and 0.42 to 2.35 ?g L(-1), respectively. Polyacrylate was identified to be the most suitable and compatible fibre for DPA analysis in apple samples, because of its high sensitivity to DPA and low fruit volatile interferences. SPME techniques were further applied to study contamination of DPA in apples, storage rooms and packaging materials. DPA was found in the air of storage rooms containing apples that were not treated with DPA. Wood and plastic bin material, bin liners, and foam insulation all adsorbed and off-gassed DPA and could be potential sources of contamination of untreated apples. PMID:24799236

Song, Jun; Forney, Charles F; Jordan, Michael A

2014-10-01

380

Silicon Based Waveguides  

NASA Astrophysics Data System (ADS)

Optical waveguide based devices are key to the operation of many modern optical communication systems. The following chapter outlines the design and application of optical waveguides of the Silicon On Insulator (SOI) type. The important properties of these waveguides are described, the design choices that must be made and their implications are highlighted. The interfacing of silicon waveguides to single mode optical fibres by the use of mode transforming tapers is described and the design methodology behind the production of adiabatic tapers is discussed. Finally the design of Arrayed Waveguide Gratings (AWGs) and Variable Optical Attenuators (VOAs) in silicon waveguide technology is outlined.

Bozeat, Robert J.; Day, S.; Hopper, F.; Payne, F. P.; Roberts, S. W.; Asghari, M.

381

Fluid flow in micro-channels  

Microsoft Academic Search

We consider the problem of liquid and gas flow in micro-channels under conditions of a small Knudsen and Mach numbers, that correspond to continuum model. Data from the literature on pressure drop in circular, rectangle, triangular and trapezoidal micro-channels with hydrodynamic diameter ranging from 1.01?m to 4010?m are analyzed. The Reynolds number at transition from laminar to turbulent flow is

G. Hetsroni; A. Mosyak; E. Pogrebnyak; L. P. Yarin

2005-01-01

382

[Determination of ten photoinitiators in fruit juices and tea beverages by solid-phase micro-extraction coupled with gas chromatography/mass spectrometry].  

PubMed

A method for the determination of ten photoinitiators (PIs), benzophenone, ethyl 4-dimethylaminobenzoate, 1-hydroxycyclohexyl-phenylketone, 4-methylbenzophenone, 2-ethylhexyl-4-dimethylaminobenzoate, 4-chlorobenzophenone, 2-chlorothioxanthone, 2-isopropylthio-xanthone, 2,2-dimethoxy-2-phenylacetophenone, methyl 2-benzoylbenzoate, in 13 kinds of fruit juice and 3 kinds of tea beverage has been established, using solid-phase micro-extraction (SPME) combined with chromatography/mass spectrometry (GC/MS). At first, the major factors of SPME, extraction time and temperature, were studied through orthogonal experiment. Then the optimal operation conditions were obtained via the refinement of various factors. After the sample was extracted by SPME, it was desorbed for target analytes in sampling inlet for 3 min, and separated on an HP-5MS column, then detected by MS in selected ion monitoring mode, and quantified through calibration curve. The working curves were obtained using sample matrix in order to eliminate the matrix interference. The linear range was from 0.3 microg/L to 60 microg/L and the detection limit range was from 3 ng/L to 16 ng/L. The samples were determined five times with four different spiked levels individually and the relative standard deviations of all the samples were less than 14.5%. This determination method was applied in 16 kinds of packed beverages with different brands and different species. Benzophenone had been detected from all the samples. 4-Methylbenzophenone, 2-ethylhexyl-4-dimethylaminobenzoate, 2-isopropylthioxanthone, 1-hydroxycyclohexyl-phenylketone and 2-chlorothioxanthone had been detected from a portion of samples. Simultaneous determination was achieved for the ten PIs. These results provide a reference to determine the PIs migrated from packing materials in beverage. This method is simple, high sensitive and non-polluting. PMID:24669718

Liu, Pengyan; Chen, Yanjie; Zhao, Chunxia; Tian, Lei

2013-12-01

383

Turbine Airfoil With CMC Leading-Edge Concept Tested Under Simulated Gas Turbine Conditions.  

National Technical Information Service (NTIS)

Silicon-based ceramics have been proposed as component materials for gas turbine engine hot-sections. When the Navy's Harrier fighter experienced engine (Pegasus F402) failure because of leading-edge durability problems on the second-stage high-pressure t...

R. C. Robinson K. S. Hatton

2000-01-01

384

Micro-machined thermo-conductivity detector  

DOEpatents

A micro-machined thermal conductivity detector for a portable gas chromatograph. The detector is highly sensitive and has fast response time to enable detection of the small size gas samples in a portable gas chromatograph which are in the order of nanoliters. The high sensitivity and fast response time are achieved through micro-machined devices composed of a nickel wire, for example, on a silicon nitride window formed in a silicon member and about a millimeter square in size. In addition to operating as a thermal conductivity detector, the silicon nitride window with a micro-machined wire therein of the device can be utilized for a fast response heater for PCR applications.

Yu, Conrad (Antioch, CA)

2003-01-01

385

Development of conceptual proposal for a nuclear facility with the gas cooled fast reactor BGR-1000 using coated micro-fuel and technologies of light water reactors  

SciTech Connect

The paper presents the status in elaboration of a reactor facility with a Gas Cooled Fast Reactor named BGR-1000 on the initial stage of developments. In the present time, general formulation of the concept is given and analysis of possible design decisions for the active core and first circuit equipment is performed. The design of a reactor facility with the fast helium cooled reactor 1000 MWe is based on the active core with fuel assemblies containing the fixed bed of coated fuel microparticles directly cooled by cross flow of helium coolant with moderate (750 deg. C) outlet temperature. The neutron-physics characteristics of this reactor and their connection with the parameters of the core layout and fuel cycle options are preliminary evaluated. Preliminary assessments are performed for thermal-hydraulic characteristics, fuel behavior analysis, etc. (authors)

Alekseev, P. N.; Balanin, A. L.; Fomichenko, P. A.; Grishanin, E. I.; Ivanov, E. A.; Ponomarev, A. S.; Zakharko, Y. A. [Russian Research Center Kurchatov Inst., Inst. of Nuclear Reactors, Kurchatov sq.1, 123182, Moscow (Russian Federation)

2006-07-01

386

Evanescent straight tapered-fiber coupling of ultra-high Q optomechanical micro-resonators in a low-vibration helium-4 exchange-gas cryostat  

NASA Astrophysics Data System (ADS)

We developed an apparatus to couple a 50-?m diameter whispering-gallery silica microtoroidal resonator in a helium-4 cryostat using a straight optical tapered-fiber at 1550 nm wavelength. On a top-loading probe specifically adapted for increased mechanical stability, we use a specifically-developed ``cryotaper'' to optically probe the cavity, allowing thus to record the calibrated mechanical spectrum of the optomechanical system at low temperatures. We then demonstrate excellent thermalization of a 63-MHz mechanical mode of a toroidal resonator down to the cryostat's base temperature of 1.65 K, thereby proving the viability of the cryogenic refrigeration via heat conduction through static low-pressure exchange gas. In the context of optomechanics, we therefore provide a versatile and powerful tool with state-of-the-art performances in optical coupling efficiency, mechanical stability, and cryogenic cooling.

Rivière, R.; Arcizet, O.; Schliesser, A.; Kippenberg, T. J.

2013-04-01

387

Evanescent straight tapered-fiber coupling of ultra-high Q optomechanical micro-resonators in a low-vibration helium-4 exchange-gas cryostat.  

PubMed

We developed an apparatus to couple a 50-?m diameter whispering-gallery silica microtoroidal resonator in a helium-4 cryostat using a straight optical tapered-fiber at 1550 nm wavelength. On a top-loading probe specifically adapted for increased mechanical stability, we use a specifically-developed "cryotaper" to optically probe the cavity, allowing thus to record the calibrated mechanical spectrum of the optomechanical system at low temperatures. We then demonstrate excellent thermalization of a 63-MHz mechanical mode of a toroidal resonator down to the cryostat's base temperature of 1.65 K, thereby proving the viability of the cryogenic refrigeration via heat conduction through static low-pressure exchange gas. In the context of optomechanics, we therefore provide a versatile and powerful tool with state-of-the-art performances in optical coupling efficiency, mechanical stability, and cryogenic cooling. PMID:23635182

Rivière, R; Arcizet, O; Schliesser, A; Kippenberg, T J

2013-04-01

388

Development, validation and application of a method to analyze phenols in water samples by solid phase micro extraction-gas chromatography-flame ionization detector.  

PubMed

In this work the development, validation and application of method using Solid Phase Microexctration (SPME) for the analyses of five pollutants (phenol, 2-nitrophenol, 2,4-dimethylphenol, 2,4-dichlorophenol and 4-chloro, 3-methyl phenol) in supplying water, using gas chromatography (GC) with flame ionization detector (FID) is described. The optimal conditions obtained for SPME were: fiber type: Poliacrylate (PA); extraction time: 40 minutes; extraction temperature: 70 degrees C; amount of salt added to sample (NaCl): 15%; desorption temperature: 8 minutes. The parameters studied in the method validation were: limit of detection (0.3 and 3.5 microg.L(- 1)); precision, measured by the variation coefficient (between 2.1 and 8.8%); calibration curve and linearity, by using the external standardization method (between 1 and 50 50 microg.L(- 1)). After the methodology development, samples of water collected in Atibaia River (São Paulo - Brazil) were analyzed, using the optimized methodology. Three water samples collected in the rain season showed a peak with retention time close to 4-chloro, 3 methyl phenol further analyzed by Gas Chromatography-Mass Spectrometry for the identity confirmation. In spite of the fact that none target compounds were found in the river water samples analyzed, the presence of two phenols different from those investigated (p-terc butyl phenol; butylated hydroxytoluene) were detected. These results together with the results of the limit of detection (that showed to be lower than the maximum concentration of phenols demanded by different environment control agencies), and the results of the validation, indicate the applicability of this method for the analysis of selected phenols in river water samples. PMID:17562456

Lanças, Fernando M; Olivares, Igor R B; Alves, Priscila M

2007-01-01

389

Micro Gas Turbines (Micro turbines a gaz) (CD-ROM).  

National Technical Information Service (NTIS)

Portable equipment as well as propulsion of small airplanes (UAV) and robots have enhanced the need for portable power supplies of large energy density (kwh/kg). The need for high performance and the specific problems resulting from the miniaturization of...

2005-01-01

390

Determination of volatile N-nitrosamines in meat products by microwave-assisted extraction coupled with dispersive micro solid-phase extraction and gas chromatography--chemical ionisation mass spectrometry.  

PubMed

A sensitive procedure, microwave-assisted extraction (MAE) coupled dispersive micro solid-phase extraction (D-?-SPE), was developed to extract N-nitrosodimethylamine (NDMA) and other six volatile N-nitrosamines (NAms) from meat products. Parameters affecting the efficiency of MAE and D-?-SPE were systematically investigated. For MAE, 5-g of a homogenised meat sample was extracted with 30 mL of a sodium hydroxide (0.025 M) solution at 100 °C for 10 min. The optimum D-?-SPE conditions were immersing 100mg of Carboxen™ 1000 adsorbent in the MAE extract. After vigorously shaking for 30 min, the NAms were then desorbed by treatment with 200 ?L of dichloromethane. A 10 ?L aliquot was determined by gas chromatography with chemical ionisation mass spectrometry (GC-CI-MS) using the selected-ion-storage (SIS) mode. The limits of quantitation (LOQs) were 0.03-0.36 ng/g. Preliminary results revealed that NDMA was present in the highest concentration, ranging from 0.8 to 3.2 ng/g. PMID:23265481

Huang, Man-Chun; Chen, Hsin-Chang; Fu, Ssu-Chieh; Ding, Wang-Hsien

2013-05-01

391

Integrated Microfluidic Gas Sensors for Water Monitoring  

NASA Technical Reports Server (NTRS)

A silicon-based microhotplate tin oxide (SnO2) gas sensor integrated into a polymer-based microfluidic system for monitoring of contaminants in water systems is presented. This device is designed to sample a water source, control the sample vapor pressure within a microchannel using integrated resistive heaters, and direct the vapor past the integrated gas sensor for analysis. The sensor platform takes advantage of novel technology allowing direct integration of discrete silicon chips into a larger polymer microfluidic substrate, including seamless fluidic and electrical interconnects between the substrate and silicon chip.

Zhu, L.; Sniadecki, N.; DeVoe, D. L.; Beamesderfer, M.; Semancik, S.; DeVoe, D. L.

2003-01-01

392

Response to simulated typical daily outdoor irradiation conditions of thin-film silicon-based triple-band-gap, triple-junction solar cells  

Microsoft Academic Search

We studied the response to various realistic outdoor conditions of thin-film silicon-based triple-band-gap, triple-junction cells that were made in house. The triple-junction cells consist of a stack of proto-Si:H\\/proto-SiGe:H\\/nanocrystalline (nc)-Si:H cells in an n–i–p configuration, fabricated using hot-wire chemical vapour deposition (CVD). Current matching was determined for modeled spectra of four different days of the year that are typical for

P. Krishnan; J. W. A. Schüttauf; B. Houshyani Hassanzadeh; W. G. J. H. M. van Sark; R. E. I. Schropp

2009-01-01

393

Invited article: A materials investigation of a phase-change micro-valve for greenhouse gas collection and other potential applications.  

PubMed

The deleterious consequences of climate change are well documented. Future climate treaties might mandate greenhouse gas (GHG) emissions measurement from signatories in order to verify compliance. The acquisition of atmospheric chemistry would benefit from low cost, small size/weight/power of microsystems. In this paper, we investigated several key materials science aspects of a phase-change microvalve (PC?V) technology with low power/size/weight/cost for ubiquitous GHG sampling. The novel design, based on phase-change material low-melting-point eutectic metal alloys (indium-bismuth, InBi and tin-lead, SnPb), could be actuated at temperatures as low as 72 °C. Valve manufacturing was based on standard thick and thin-film processes and solder technologies that are commonly used in industry, enabling low-cost, high-volume fabrication. Aging studies showed that it was feasible to batch fabricate the PC?Vs and store them for future use, especially in the case of SnPb alloys. Hermetic sealing of the valve prototypes was demonstrated through helium leak testing, and Mil spec leak rates less than 1 × 10(-9) atm cm(3)/s were achieved. This confirms that the sample capture and analysis interval can be greatly expanded, easing the logistical burdens of ubiquitous GHG monitoring. Highly conservative and hypothetical CO(2) bias due to valve actuation at altitude in 1 cm(3) microsamplers would be significantly below 1.0 and 2.2 ppmv for heat-treated InBi and SnPb solders, respectively. The CO(2) bias from the PC?V scales well, as a doubling of sampler volume halved the bias. We estimated the shelf life of the SnPb PC?Vs to be at least 2.8 years. These efforts will enable the development of low cost, low dead volume, small size/weight microsystems for monitoring GHGs and volatile organic compounds. PMID:22462899

Manginell, Ronald P; Moorman, Matthew W; Rejent, Jerome A; Vianco, Paul T; Grazier, Mark J; Wroblewski, Brian D; Mowry, Curtis D; Achyuthan, Komandoor E

2012-03-01

394

Novel applications for micro-SOFCs  

NASA Astrophysics Data System (ADS)

The application of micro-solid oxide fuels cells in small systems is discussed. Two types of application are examined, namely, leisure CHP systems and micro-hybrid vehicles. A unique triple layer catalyst-SOFC-catalyst system has been designed utilising propane/butane fuel. The system consists of a co-generating gas burner with a pre-reforming catalyst, a micro-SOFC stack and an oxidation catalyst. The pre-reforming catalyst comprising of Ru metal on Saffil® ceramic wool, was used to partially reform the propane/butane gas prior to entering the fuel cell, preventing carbon formation. The micro-SOFCs were YSZ tubes (Adelan, UK) with nickel/YSZ cermet anodes on the outside and strontium-doped lanthanum manganite cathodes on the inside. Final oxidation was provided by a cordierite honeycomb coated with platinum combustion catalyst producing most of the heat for the fuel cell operation. Initial performance results were obtained and it was shown that a co-generating system could be achieved using a propane/butane fuel supply, piezoelectric ignition system and air supply for the triple catalyst system. The application of this micro-SOFC system for leisure and micro-hybrid vehicles, such as golf trolleys and power-assisted bicycles, is described.

Tompsett, G. A.; Finnerty, C.; Kendall, K.; Alston, T.; Sammes, N. M.

395

Micro-ejector to supply fuel–air mixture to a micro-combustor  

Microsoft Academic Search

Micro-ejectors to supply fuel–air mixture to micro-combustors were fabricated and tested. The ejector sucks air using the jet of vaporized liquid gas ejected from a nozzle by its own vapor pressure, and needs no moving part and electric power supply. A tapered nozzle and a Laval nozzle were fabricated by the deep reactive ion etching of silicon. Using the Laval

Daisuke Satoh; Shuji Tanaka; Kazushi Yoshida; Masayoshi Esashi

2005-01-01

396

Investigation of bonding properties of denture bases to silicone-based soft denture liner immersed in isobutyl methacrylate and 2-hydroxyethyl methacrylate  

PubMed Central

PURPOSE The purpose of this study was to investigate the bonding properties of denture bases to silicone-based soft denture liners immersed in isobutyl methacrylate (iBMA) and 2-hydroxyethyl methacrylate (HEMA) for various lengths of time. MATERIALS AND METHODS Polymethyl methacrylate (PMMA) test specimens were fabricated (75 mm in length, 12 mm in diameter at the thickest section, and 7 mm at the thinnest section) and then randomly assigned to five groups (n=15); untreated (Group 1), resilient liner immersed in iBMA for 1 minute (Group 2), resilient liner immersed in iBMA for 3 minutes (Group 3), resilient liner immersed in HEMA for 1 minute (Group 4), and resilient liner immersed in HEMA for 3 minutes (Group 5). The resilient liner specimens were processed between 2 PMMA blocks. Bonding strength of the liners to PMMA was compared by tensile test with a universal testing machine at a crosshead speed of 5 mm/min. Data were evaluated by 1-way ANOVA and post hoc Tukey-Kramer multiple comparisons tests (?=0.05). RESULTS The highest mean value of force was observed in Group 3 specimens. The differences between groups were statistically significant (P<.05), except between Group 1 and Group 4 (P=.063). CONCLUSION Immersion of silicone-based soft denture liners in iBMA for 3 minutes doubled the tensile bond strength between the silicone soft liner and PMMA denture base materials compared to the control group.

Tugut, Faik; Mutaf, Burcu; Guney, Umit

2014-01-01

397

Effect of 5.25 % sodium hypochlorite on color stability of acrylic and silicone based soft liners and a denture base acrylic resin.  

PubMed

The purpose of the current study was to investigate the effect of a chemical disinfectant (sodium hypochlorite 5.25 %) on color stability of a denture base acrylic resin and two processed soft denture lining materials of two different types (acrylic-based and silicone-based). Ten specimens from each type of materials tested were made (2 × 20 × 20 mm). All specimens were immersed in sodium hypochlorite (5.25 %). Colorimetric measurements for each specimen were taken before immersion, and after 24 h and 7 days of immersion. Color changes were evaluated using the CIE L*a*b* colorimetric system. Data were statistically analyzed with one-way analysis of variance (ANOVA) (? = 0.05). ANOVA was followed by Bonferroni test to determine which groups differed from each other. ?E and ?L* of the silicone-based liner at the 1st and 7th days of immersion were significantly more than of denture base acrylic resin and acrylic-based liner. Change in ?L* values of denture base acrylic resin and acrylic-based liner was small and statistically insignificant after 24 h of its immersion. However, the increase in ?L* values of the acrylic-based liner after 7 days of immersion was considerably more than of denture base acrylic resin. Color changes in denture base acrylic resin and soft denture liners tended to increase with longer immersion times, and the color stability of the soft denture liners was influenced by its chemical type. PMID:24757356

Salloum, Alaa'a M

2014-06-01

398

Freeform fabrication of titanium metal by 3D micro welding  

Microsoft Academic Search

A novel freeform fabrication method named 3D micro welding (3DMW) has been developed. It is a combined process of the freeform fabrication method with TIG (tungsten inert gas) welding. The titanium micro beads were investigated with respect to the diameter, height, and contact angle to the titanium substrate as functions of arc discharge current and two different shielding gases. The

M. Terakubo; Janghwan Oh; S. Kirihara; Y. Miyamoto; K. Matsuura; M. Kudoh

2005-01-01

399

Design and fabrication of a cross flow micro heat exchanger  

Microsoft Academic Search

A cross flow micro heat exchanger was designed to maximize heat transfer from a liquid (water-glycol) to a gas (air) for a given frontal area while holding pressure drop across the heat exchanger of each fluid to values characteristic of conventional scale heat exchangers. The predicted performance for these plastic, ceramic, and aluminum micro heat exchangers are compared with each

Chad Harris; Mircea Despa; Kevin Kelly

2000-01-01

400

Method and Device for Creating a Micro Plasma Jet.  

National Technical Information Service (NTIS)

A microhollow cathode discharge assembly capable of generating a low temperature, atmospheric pressure plasma micro jet is disclosed. The microhollow assembly has at two electrodes: an anode and a cathode separated by a dielectric. A microhollow gas passa...

A. A. H. Mohamed J. F. Kolb K. H. Schoenbach

2005-01-01

401

Carbon Residue Studies with a Micro Carbon Residue Tester.  

National Technical Information Service (NTIS)

A test procedure for the coking propensity of gas turbine lubricants was developed using the 'Micro Carbon Residue Tester-100' (MCRT-100). The MCRT-1009, a microprocessor controlled heating unit, was evaluated for its ability to determine carbon residue i...

W. Bochartz

1986-01-01

402

Fabrication of a Flexible Micro CO Sensor for Micro Reformer Applications  

PubMed Central

Integration of a reformer and a proton exchange membrane fuel cell (PEMFC) is problematic due to the presence in the gas from the reforming process of a slight amount of carbon monoxide. Carbon monoxide poisons the catalyst of the proton exchange membrane fuel cell subsequently degrading the fuel cell performance, and necessitating the sublimation of the reaction gas before supplying to fuel cells. Based on the use of micro-electro-mechanical systems (MEMS) technology to manufacture flexible micro CO sensors, this study elucidates the relation between a micro CO sensor and different SnO2 thin film thicknesses. Experimental results indicate that the sensitivity increases at temperatures ranging from 100–300 °C. Additionally, the best sensitivity is obtained at a specific temperature. For instance, the best sensitivity of SnO2 thin film thickness of 100 nm at 300 °C is 59.3%. Moreover, a flexible micro CO sensor is embedded into a micro reformer to determine the CO concentration in each part of a micro reformer in the future, demonstrating the inner reaction of a micro reformer in depth and immediate detection.

Lee, Chi-Yuan; Chang, Chi-Chung; Lo, Yi-Man

2010-01-01

403

Fabrication of a flexible micro CO sensor for micro reformer applications.  

PubMed

Integration of a reformer and a proton exchange membrane fuel cell (PEMFC) is problematic due to the presence in the gas from the reforming process of a slight amount of carbon monoxide. Carbon monoxide poisons the catalyst of the proton exchange membrane fuel cell subsequently degrading the fuel cell performance, and necessitating the sublimation of the reaction gas before supplying to fuel cells. Based on the use of micro-electro-mechanical systems (MEMS) technology to manufacture flexible micro CO sensors, this study elucidates the relation between a micro CO sensor and different SnO2 thin film thicknesses. Experimental results indicate that the sensitivity increases at temperatures ranging from 100-300 °C. Additionally, the best sensitivity is obtained at a specific temperature. For instance, the best sensitivity of SnO2 thin film thickness of 100 nm at 300 °C is 59.3%. Moreover, a flexible micro CO sensor is embedded into a micro reformer to determine the CO concentration in each part of a micro reformer in the future, demonstrating the inner reaction of a micro reformer in depth and immediate detection. PMID:22163494

Lee, Chi-Yuan; Chang, Chi-Chung; Lo, Yi-Man

2010-01-01

404

Determination of acrylamide in Chinese traditional carbohydrate-rich foods using gas chromatography with micro-electron capture detector and isotope dilution liquid chromatography combined with electrospray ionization tandem mass spectrometry.  

PubMed

The present study developed two analytical methods for quantification of acrylamide in complex food matrixes, such as Chinese traditional carbohydrate-rich foods. One is based on derivatization with potassium bromate and potassium bromide without clean-up prior to gas chromatography with micro-electron capture detector (GC-MECD). Alternatively, the underivatized acrylamide was detected by high-performance liquid chromatography coupled to quadrupole tandem mass spectrometry (HPLC-MS/MS) in the positive electrospray ionization mode. For both methods, the Chinese carbohydrate-rich samples were homogenized, defatted with petroleum ether and extracted with aqueous solution of sodium chloride. Recovery rates for acrylamide from spiked Chinese style foods with the spiking level of 50, 500 and 1000 microg kg(-1) were in the range of 79-93% for the GC-MECD including derivatization and 84-97% for the HPLC-MS/MS method. Typical quantification limits of the HPLC-MSMS method were 4 microg kg(-1) for acrylamide. The GC-MECD method achieved quantification limits of 10 microg kg(-1) in Chinese style foods. Thirty-eight Chinese traditional foods purchased from different manufacturers were analyzed and compared with four Western style foods. Acrylamide contaminant was found in all of samples at the concentration up to 771.1 and 734.5 microg kg(-1) detected by the GC and HPLC method, respectively. The concentrations determined with the two different quantitative methods corresponded well with each other. A convenient and fast pretreatment procedure will be optimized in order to satisfy further investigation of hundreds of samples. PMID:17386622

Zhang, Yu; Ren, Yiping; Zhao, Hangmei; Zhang, Ying

2007-02-19

405

Development, validation and application of a methodology based on solid-phase micro extraction followed by gas chromatography coupled to mass spectrometry (SPME/GC-MS) for the determination of pesticide residues in mangoes.  

PubMed

A method was developed for the simultaneous analysis of 14 pesticide residues (clofentezine, carbofuran, diazinon, methyl parathion, malathion, fenthion, thiabendazole, imazalil, bifenthrin, permethrin, prochloraz, pyraclostrobin, difenoconazole and azoxystrobin) in mango fruit, based on solid-phase micro extraction (SPME) coupled to gas chromatography-mass spectrometry (GC-MS). Different parameters of the method were evaluated, such as fiber type, extraction mode (direct immersion and headspace), temperature, extraction and desorption times, stirring velocities and ionic strength. The best results were obtained using polyacrylate fiber and direct immersion mode at 50 degrees C for 30 min, along with stirring at 250 rpm and desorption for 5 min at 280 degrees C. The method was validated using mango samples spiked with pesticides at concentration levels ranging from 33.3 to 333.3 microg kg(-1). The average recoveries (n=3) for the lowest concentration level ranged from 71.6 to 117.5%, with relative standard deviations between 3.1 and 12.3%, respectively. Detection and quantification limits ranged from 1.0 to 3.3 microg kg(-1) and from 3.33 to 33.33 microg kg(-1), respectively. The optimized method was then applied to 16 locally purchased mango samples, all of them containing the pesticides bifenthrin and azoxystrobin in concentrations of 18.3-57.4 and 12.7-55.8 microg kg(-1), respectively, although these values were below the MRL established by Brazilian legislation. The method proved to be selective, sensitive, and with good precision and recovery rates, presenting LOQ below the MRL admitted by Brazilian legislation. PMID:20188930

Menezes Filho, Adalberto; dos Santos, Fábio Neves; Pereira, Pedro Afonso de Paula

2010-04-15

406

Micro-fabricated electrolytic micro-bubblers  

Microsoft Academic Search

Rectangular node electrodes were developed with micro-fabrication techniques in order to produce an electrolytic micro-bubbler which, while subjected to a convective flow, can generate bubbles of nearly uniform size with mean diameters of 50?m or less. The devices were fabricated and placed in both a quiescent tap water chamber and a water channel operating at laminar flow rates. The effect

S. Lee; W. Sutomo; C. Liu; E. Loth

2005-01-01

407

Micro-cantilevers for gas sensing  

Microsoft Academic Search

Cantilevers fabricated from a SOI wafers using bulk micromachining are used in combination with polymer deposition to detect down to 25 ppm of toluene concentration in synthetic air. The cantilevers proposed are thermoelectrically actuated and the movement detection is done by piezoresistance in a Wheatstone bridge configuration.

M. Morata; J. Amirola; E. Figueras; L. Fonseca; J. Santander; I. Gracia; M. Dominguez; A. Rodriguez; M. C. Horrillo; C. Cane

2005-01-01

408

MicroSight Optics  

ScienceCinema

MicroSight is an innovative gunsight technology that allows a marksman's eye to focus on both the front gunsight and the intended target. The MicroSight improves both firearm safety and performance by imaging two objects at different focal distances. The MicroSight was developed at Idaho National Laboratory, and has been licensed by Apollo Optical Systems. You can learn more about INL's research programs at http://www.facebook.com/idahonationallaboratory.

None

2013-05-28

409

MicroSight Optics  

SciTech Connect

MicroSight is an innovative gunsight technology that allows a marksman's eye to focus on both the front gunsight and the intended target. The MicroSight improves both firearm safety and performance by imaging two objects at different focal distances. The MicroSight was developed at Idaho National Laboratory, and has been licensed by Apollo Optical Systems. You can learn more about INL's research programs at http://www.facebook.com/idahonationallaboratory.

None

2010-01-01

410

Adhesion forces reduction for micro manipulation based on micro physics  

Microsoft Academic Search

Micro manipulation is required for assembling and maintenance of micro machines and their parts. As the handling objects are miniaturized, interactive forces such as van der Waals force, surface tension force and electrostatic force between micro particles and gripper surface become dominant in the air. We cannot neglect such adhesion forces in micro manipulation. We should consider the Micro Physics

Fumihito ARAI; Daisuke ANDOU; Toshio FUKUDA

1996-01-01

411

A lithium-ion sulfur battery based on a carbon-coated lithium-sulfide cathode and an electrodeposited silicon-based anode.  

PubMed

In this paper, we report a lithium-ion battery employing a lithium sulfide cathode and a silicon-based anode. The high capacity of the silicon anode and the high efficiency and cycling rate of the lithium sulfide cathode allowed optimal full cell balance. We show in fact that the battery operates with a very stable capacity of about 280 mAh g(-1) at an average voltage of 1.4 V. To the best of our knowledge, this battery is one of the rare examples of lithium-metal-free sulfur battery. Considering the high theoretical capacity of the employed electrodes, we believe that the battery here reported may be of potential interest as high-energy, safe, and low-cost power source for electric vehicles. PMID:24559093

Agostini, Marco; Hassoun, Jusef; Liu, Jun; Jeong, Moongook; Nara, Hiroki; Momma, Toshiyuki; Osaka, Tetsuya; Sun, Yang-Kook; Scrosati, Bruno

2014-07-23

412

Improved sensing performance of polycrystalline-silicon based dual-gate ion-sensitive field-effect transistors using high-k stacking engineered sensing membrane  

NASA Astrophysics Data System (ADS)

Improved sensing performance, larger pH sensitivity that breaches the Nernst response limit with excellent stability, was realized on polycrystalline silicon based dual-gate (DG) ion-sensitive field-effect transistors. The capacitive coupling between the top and bottom gate oxides for a DG operation amplified its sensitivity to as high as 325.8 mV/pH. In particular, the SiO2/HfO2/Al2O3 (OHA) layer, proposed as an engineered sensing membrane, significantly reinforced the sensing margin of devices as well as the chemical stability for long-term use. The sensing characteristics of the OHA and conventional SiO2 layer were evaluated for single gate and DG operation modes, respectively.

Jang, Hyun-June; Bae, Tae-Eon; Cho, Won-Ju

2012-06-01

413

Microstructure of amorphous-silicon-based solar cell materials by small-angle x-ray scattering. Annual technical report, April 6, 1995--April 5, 1996  

SciTech Connect

The objective of this project is to provide detailed microstructural information on the amorphous silicon based thin film materials under development for improved multijunction solar cells. Correlation of microstructure with opto-electrical properties and device performance is an integral part of the research. During this second phase of our three-year program we have obtained information on the microstructure of materials relevant to the Low-, Mid-, and High-bandgap Teams and the results are appropriately divided into these three types of material as presented below. The experimental methods, data analysis, and interpretation procedures are the same as those described in detail in the phase-one report and in the review paper published last year.

Williamson, D.L. [Colorado School of Mines, Golden, CO (United States)

1996-08-01

414

A progress report on the LDRD project entitled {open_quotes}Microelectronic silicon-based chemical sensors: Ultradetection of high value molecules{close_quotes}  

SciTech Connect

This work addresses a new kind of silicon based chemical sensor that combines the reliability and stability of silicon microelectronic field effect devices with the highly selective and sensitive immunoassay. The sensor works on the principle that thin SiN layers on lightly doped Si can detect pH changes rapidly and reversibly. The pH changes affect the surface potential, and that can be quickly determined by pulsed photovoltage measurements. To detect other species, chemically sensitive films were deposited on the SiN where the presence of the chosen analyte results in pH changes through chemical reactions. A invention of a cell sorting device based on these principles is also described. A new method of immobilizing enzymes using Sandia`s sol-gel glasses is documented and biosensors based on the silicon wafer and an amperometric technique are detailed.

Hughes, R.C.

1996-09-01

415

Sensitive detection of protein and miRNA cancer biomarkers using silicon-based photonic crystals and a resonance coupling laser scanning platform.  

PubMed

Enhancement of the fluorescent output of surface-based fluorescence assays by performing them upon nanostructured photonic crystal (PC) surfaces has been demonstrated to increase signal intensities by >8000×. Using the multiplicative effects of optical resonant coupling to the PC in increasing the electric field intensity experienced by fluorescent labels ("enhanced excitation") and the spatially biased funneling of fluorophore emissions through coupling to PC resonances ("enhanced extraction"), PC enhanced fluorescence (PCEF) can be adapted to reduce the limits of detection of disease biomarker assays, and to reduce the size and cost of high sensitivity detection instrumentation. In this work, we demonstrate the first silicon-based PCEF detection platform for multiplexed biomarker assay. The sensor in this platform is a silicon-based PC structure, comprised of a SiO2 grating that is overcoated with a thin film of high refractive index TiO2 and is produced in a semiconductor foundry for low cost, uniform, and reproducible manufacturing. The compact detection instrument that completes this platform was designed to efficiently couple fluorescence excitation from a semiconductor laser to the resonant optical modes of the PC, resulting in elevated electric field strength that is highly concentrated within the region <100 nm from the PC surface. This instrument utilizes a cylindrically focused line to scan a microarray in <1 min. To demonstrate the capabilities of this sensor-detector platform, microspot fluorescent sandwich immunoassays using secondary antibodies labeled with Cy5 for two cancer biomarkers (TNF-? and IL-3) were performed. Biomarkers were detected at concentrations as low as 0.1 pM. In a fluorescent microarray for detection of a breast cancer miRNA biomarker miR-21, the miRNA was detectable at a concentration of 0.6 pM. PMID:23963502

George, Sherine; Chaudhery, Vikram; Lu, Meng; Takagi, Miki; Amro, Nabil; Pokhriyal, Anusha; Tan, Yafang; Ferreira, Placid; Cunningham, Brian T

2013-10-21

416

Design and prototyping of micro centrifugal compressor  

NASA Astrophysics Data System (ADS)

In order to establish the design methodology of ultra micro centrifugal compressor, which is the most important component of ultra micro gas turbine unit, a 10 times of the final target size model was designed, prototyped and tested. The problems to be solved for downsizing were examined and 2-dimensional impeller was chosen as the first model due to its productivity. The conventional 1D prediction method, CFD and the inverse design were attempted. The prototyped compressor was driven by using a turbocharger and the performance characteristics were measured.

Mizuki, Shimpei; Minorikawa, Gaku; Hirano, Toshiyuki; Asaga, Yuichiro; Yamaguchi, Naoki; Ohta, Yutaka; Outa, Eisuke

2003-02-01

417

Simultaneous determination of bisphenol A and bisphenol B in beverages and powdered infant formula by dispersive liquid-liquid micro-extraction and heart-cutting multidimensional gas chromatography-mass spectrometry.  

PubMed

The purpose of this study was to establish a reliable, cost-effective, fast and simple method to quantify simultaneously both bisphenol A (BPA) and bisphenol B (BPB) in liquid food matrixes such as canned beverages (soft drinks and beers) and powdered infant formula using dispersive liquid-liquid micro-extraction (DLLME) with in-situ derivatisation coupled with heart-cutting gas chromatography-mass spectrometry (GC-MS). For the optimisation of the DLLME procedure different amounts of various extractive and dispersive solvents as well as different amounts of the derivative reagent were compared for their effects on extraction efficiency and yields. The optimised procedure consisted of the injection of a mixture containing tetrachloroethylene (extractant), acetonitrile (dispersant) and acetic anhydride (derivatising reagent) directly into an aliquot of beverage samples or into an aqueous extract of powdered milk samples obtained after a pretreatment of the samples. Given the compatibility of the solvents used, and the low volumes involved, the procedure was easily associated with GC-MS end-point determination, which was accomplished by means of an accurate GC dual column (heart-cutting) technique. Careful optimisation of heart-cutting GC-MS conditions, namely pressure of front and auxiliary inlets, have resulted in a good analytical performance. The linearity of the matrix-matched calibration curves was acceptable, with coefficients of determination (r2) always higher than 0.99. Average recoveries of the BPA and BPB spiked at two concentration levels into beverages and powdered infant formula ranged from 68% to 114% and the relative standard deviation (RSD) was <15%. The limits of detection (LOD) in canned beverages were 5.0 and 2.0 ng l(-1) for BPA and BPB, respectively, whereas LOD in powdered infant formula were 60.0 and 30.0 ng l(-1), respectively. The limits of quantification (LOQ) in canned beverages were 10.0 and 7.0 ng l-1 for BPA and BPB, respectively, whereas LOQ in powdered infant formula were 200.0 and 100.0 ng l(-1), respectively. BPA was detected in 21 of 30 canned beverages (ranging from 0.03 to 4.70 µg l(-1)) and in two of seven powdered infant formula samples (0.23 and 0.40 µg l(-1)) collected in Portugal. BPB was only detected in canned beverages being positive in 15 of 30 samples analysed (ranging from 0.06 to 0.17 µg l(-1)). This is the first report about the presence of BPA and BPB in canned beverages and powdered infant formula in the Portuguese market. PMID:21240700

Cunha, S C; Almeida, C; Mendes, E; Fernandes, J O

2011-04-01

418

Process for the deposition of high temperature stress and oxidation resistant coatings on silicon-based substrates  

DOEpatents

A process is disclosed for depositing a high temperature stress and oxidation resistant coating on a silicon nitride- or silicon carbide-based substrate body. A gas mixture is passed over the substrate at about 900--1500 C and about 1 torr to about ambient pressure. The gas mixture includes one or more halide vapors with other suitable reactant gases. The partial pressure ratios, flow rates, and process times are sufficient to deposit a continuous, fully dense, adherent coating. The halide and other reactant gases are gradually varied during deposition so that the coating is a graded coating of at least two layers. Each layer is a graded layer changing in composition from the material over which it is deposited to the material of the layer and further to the material, if any, deposited thereon, so that no clearly defined compositional interfaces exist. The gases and their partial pressures are varied according to a predetermined time schedule and the halide and other reactant gases are selected so that the layers include (a) an adherent, continuous intermediate layer about 0.5-20 microns thick of an aluminum nitride or an aluminum oxynitride material, over and chemically bonded to the substrate body, and (b) an adherent, continuous first outer layer about 0.5-900 microns thick including an oxide of aluminum or zirconium over and chemically bonded to the intermediate layer.

Sarin, V.K.

1991-07-30

419

Process for the deposition of high temperature stress and oxidation resistant coatings on silicon-based substrates  

DOEpatents

A process for depositing a high temperature stress and oxidation resistant coating on a silicon nitride- or silicon carbide-based substrate body. A gas mixture is passed over the substrate at about 900.degree.-1500.degree. C. and about 1 torr to about ambient pressure. The gas mixture includes one or more halide vapors with other suitable reactant gases. The partial pressure ratios, flow rates, and process times are sufficient to deposit a continuous, fully dense, adherent coating. The halide and other reactant gases are gradually varied during deposition so that the coating is a graded coating of at least two layers. Each layer is a graded layer changing in composition from the material over which it is deposited to the material of the layer and further to the material, if any, deposited thereon, so that no clearly defined compositional interfaces exist. The gases and their partial pressures are varied according to a predetermined time schedule and the halide and other reactant gases are selected so that the layers include (a) an adherent, continuous intermediate layer about 0.5-20 microns thick of an aluminum nitride or an aluminum oxynitride material, over and chemically bonded to the substrate body, and (b) an adherent, continuous first outer layer about 0.5-900 microns thick including an oxide of aluminum or zirconium over and chemically bonded to the intermediate layer.

Sarin, Vinod K. (Lexington, MA)

1991-01-01

420

Fluid inclusion volatile analysis by gas chromatography with photoionization micro-thermal conductivity detectors: Applications to magmatic MoS 2 and other H 2O-CO 2 and H 2O-CH 4 fluids  

NASA Astrophysics Data System (ADS)

Eighteen fluid inclusion volatile peaks have been detected and identified from 1-2 g samples (quartz) by gas chromatography using heated (~105°C) on-line crushing, helium carrier gas, a single porous polymer column (HayeSep R; 10' × 1/8?: 100/120#; Ni alloy tubing), two temperature programme conditions for separate sample aliquots, micro-thermal conductivity (TCD) and photoionization detectors (PID; 11.7 eV lamp), and off-line digital peak processing. In order of retention time these volatile peaks are: N 2, Ar, CO, CH 4, CO 2, C 2H 4, C 2H 6, C 2H 2, COS, C 3H 6, C 3H 8, C 3H 4 (propyne), H 2O (22.7 min at 80°C), SO 2, ± iso- C4H10 ± C4H8 (1-butene) ± CH3SH, C 4H 8 (iso-butylene), (?) C 4H 6 (1,3 butadiene) and ± n- C4H10 ± C4H8 (trans-2-butene) (80 and -70°C temperature programme conditions combined). H 2O is analysed directly. O 2 can be analysed cryogenically between N 2 and Ar, but has not been detected in natural samples to date in this study. H 2S, SO 2, NH 3, HCl, HCN, and H 2 ca nnot be analysed at present. Blanks determined by crushing heat-treated Brazilian quartz (800-900°C/4 h) are zero for 80°C temperature programme conditions, except for a large, unidentified peak at ~64 min, but contain H 2O, CO 2, and some low molecular weight hydrocarbons at -70°C temperature conditions due to cryogenic accumulation from the carrier gas and subsequent elution. TCD detection limits are ~30 ppm molar in inclusions; PID detection limits are ~ 1 ppm molar in inclusions and lower for unsaturated hydrocarbons (e.g., ~0.2 ppm for C 2H 4; ~ 1 ppb for C 2H 2; ~0.3 ppb for C 3H 6). Precisions (1?) are ~ ±1-2% and ~ ± 13% for H 2O in terms of total moles detected; the latter value is equivalent to ±0.6 mol% at the 95 mol% H 2O level. Major fluid inclusion volatile species have been successfully analysed on a ~50 mg fluid inclusion section chip (~7 mm × ~10 mm × ~100 ?m). Initial inclusion volatile analyses of fluids of interpreted magmatic origin from the Cretaceous Boss Mtn. monzogranite stock-related MoS 2 deposit, central British Columbia of ~97 mol% H 2O, ~3% CO 2, ~ 140-150 ppm N 2, and ~16-39 ppm CH 4 (~300-350°C) are reasonable in comparison with high temperature (~400-900°C) volcanic gas analyses from four, active calc-alkaline volcanoes; e.g., the H 2O contents of volcanic gases from the White Island (New Zealand), Mount St. Helens (Washington, USA), Merapi (Bali, Indonesia), and Momotombo (Nicaragua) volcanoes are 88-95%, >90% (often >95%), 88-95% and ~93%, respectively; CO 2 contents are ~3-10%, 1-10%, 3-8%, and ~3.5%. CO 2/N 2 ratios for the Boss Mtn. MoS 2 fluids of ~ 190-220 are in the range for known volcanic gas ratios (e.g., ~ 150- 240; White Island). The ?S content of the Boss Mtn. MoS 2 fluid prior to S loss by sulphide precipitation may have been ~2 mol% since CO 2/?S molar ratios of analysed high-temperature volcanic gases are ~ 1.5. This estimate is supported by ?S contents for White Island, Merapi and Momotombo volcanic gases of ~2%, ~0.5-2.5%, and ~2%. COS has been determined in H 2O-CO 2 fluid inclusions of interpreted magmatic origin from the Boss Mtn. MoS 2 deposit and the Tanco zoned granitic pegmatite, S.E. Manitoba at ~50-100 ppm molar levels, which are consistent with levels in volcanic gases. It appears that low, but significant, concentrations of C 2-C 4 alkanes (~ 1-20 ppm), C 2-C 4 alkenes (~ 1-480 ppb) and alkynes (e.g., C 3H 4) have been detected in magmatically derived fluids (Boss Mtn. MoS 2 deposit; Tanco granitic pegmatite). Significantly higher, low molecular weight hydrocarbon concentrations have been determined in a CH 4-rich (~ 2%), externally derived fluid of possible metamorphic or deep crustal origin trapped as inclusions in metasomatic wall-rock tourmaline adjacent to the Tanco pegmatite (e.g., 300/470 ppm C 2H 6; 50/90 ppm C 3H 8; 3-60 ppm C 2H 4/C 3H 6 n-C 4H 10).

Bray, C. J.; Spooner, E. T. C.

1992-01-01

421

Microcrystalline silicon germanium: An attractive bottom-cell material for thin-film silicon-based tandem-solar-cells  

SciTech Connect

The authors have prepared hydrogenated microcrystalline silicon germanium by plasma enhanced CVD of a mixture of silane and germane gas diluted with hydrogen. The growth conditions have been systematically controlled to obtain large ({approximately}400{angstrom}) crystallites of silicon-germanium as observed using Raman scattering and x-ray diffraction. The dangling bond (germanium) density has been reduced to <5 x 10{sup 16} cm{sup {minus}3} at low substrate temperatures ({approximately}150 C). The optical absorption spectra of the 50% Ge containing material is red-shifted compared to microcrystalline silicon, consistent with a reduction of the indirect optical gap to 0.9 eV. Schottky type cells fabricated using Au on an n{sup +} crystalline silicon substrate confirm that the long wavelength response is remarkably enhanced in this material.

Ganguly, Gautam; Ikeda, Toru; Kajiwara, Kei; Matduda, Akihisa

1997-07-01

422

Advanced Hot Gas Filter Development.  

National Technical Information Service (NTIS)

This report describes the fabrication and testing of continuous fiber ceramic composite (CFCC) based hot gas filters. The fabrication approach utilized a modified filament winding method that combined both continuous and chopped fibers into a novel micros...

R. A. Wagner

1998-01-01

423

Enhancement of silicon using micro-patterned surfaces of thin films.  

PubMed

Micro-textured biomaterials might enhance cytocompatibility of silicon-based micro-electro-mechanical system (bio-MEMS) dummies. Photolithography-physical vapour deposition was used to produce diamond-like carbon (DLC) or Ti squares and circles on silicon, and also their inverse replicas; then DLC and Ti were compared for their guiding potential, using a SaOS-2 cell model. Scanning electron microscopy at 48 hours indicated cells were well-spread on large-sized patterns (several cells on one pattern) and assumed the geometrical architecture of underlying features. Medium-sized patterns (slightly smaller than solitary indicator cells) were inhabited by singular cells, which stretched from one island to another, assuming longitudinal or branching morphologies. On small-sized patterns (much smaller than individual cells;rpar; cells covered large micro-textured areas, but cellular filopodia bypassed the bare silicon. Immunofluorescence and confocal laser scanning microscopy indicated that the actin cytoskeleton and vinculin-containing adhesion junctions were present on the patterned areas, but not on the bare silicon. Cell density/coverage disclosed a 3.4-3.7-fold preference for the biomaterial patterns over silicon substrate (p 0.001). Differences in the cellular response between materials were lost at 120 hours when cells were confluent. The working hypothesis was proven; enhancement by micro-patterning depends on the pattern size, shape and material and can be used to improve biocompatibility during the initial integration phase of the device. PMID:20379964

Kaivosoja, Emilia; Myllymaa, Sami; Kouri, Vesa-Petteri; Myllymaa, Katja; Lappalainen, Reijo; Konttinen, Yrjö T

2010-01-01

424

Breakdown study of dc silicon micro-discharge devices  

NASA Astrophysics Data System (ADS)

The influence of geometrical and operating parameters on the electrical characteristics of dc microcavity discharges provides insight into their controlling physics. We present here results of such a study on silicon-based microcavity discharge devices carried out in helium at pressure ranging from 100 to 1000 Torr. Different micro-reactor configurations were measured. The differences include isolated single cavities versus arrays of closely spaced cavities, various cavity geometries (un-etched as well as isotropically and anisotropically etched), various dimensions (100 or 150 µm cavity diameter and 0-150 µm depth). The electrode gap was kept constant in all cases at approximately 6 µm. The applied electric field reaches 5 × 107 V m-1 which results in current and power densities up to 2 A cm-2 and 200 kW cm-3, respectively. The number of microcavities and the microcavity depth are shown to be the most important geometrical parameters for predicting breakdown and operation of microcavity devices. The probability of initiatory electron generation which is volume dependent and the electric field strength which is depth dependent are, respectively, considered to be responsible. The cavity shape (isotropic/anisotropic) and diameter had no significant influence. The number of micro-discharges that could be ignited depends on the rate of voltage rise and pressure. Larger numbers ignite at lower frequency and pressure. In addition, the voltage polarity has the largest influence on the electrical characteristics of the micro-discharge of all parameters, which is due to both the asymmetric role of electrodes as electron emitter and the non-uniformity of the electric field resulting in different ionization efficiencies. The qualitative shape of all breakdown voltage versus pressure curves can be explained in terms of the distance over which the discharge breakdown effectively occurs as long as one understand that this distance can depend on pressure.

Schwaederlé, L.; Kulsreshath, M. K.; Overzet, L. J.; Lefaucheux, P.; Tillocher, T.; Dussart, R.

2012-02-01

425

Micro-elastohydrodynamic lubrication  

NASA Technical Reports Server (NTRS)

Conventional elastohydrodynamics, which is based on assumption of smooth surfaces, is reviewed to show its insufficiency for explaining the failure processes in these contacts. For conditions approaching failure, lubrication breakdown occurs locally at asperity contacts where the lubrication behavior is controlled by microelastohydrodynamic lubrication (micro-EHL). The film formation mechanisms in micro-EHL conjunctions is described. The level of film thickness due to normal approach and sliding of a single asperity and due to asperity-asperity collision between two asperities is assessed. Possible influence of the micro-EHL to incipient scuffing failure, surface crack propagation and wear are discussed.

Cheng, H. S.

1984-01-01

426

Micro electrochemical milling  

NASA Astrophysics Data System (ADS)

In this paper, electrochemical machining (ECM) for fabricating micro structures is presented. By applying ultra short pulses, dissolution of a workpiece can be restricted to the region very close to an electrode. Using this method, 3D micro structures were machined on stainless steel. Good surface quality of the structures was obtained in the low concentration electrolyte, 0.1 M H2SO4. In ECM, when the machining depth increases, structures taper. To reduce the taper, a disc-type electrode is introduced. By electrochemical milling, various 3D micro structures including a hemisphere with 60 µm diameter were fabricated.

Kim, Bo Hyun; Ryu, Shi Hyoung; Choi, Deok Ki; Chu, Chong Nam

2005-01-01

427

Development of a Silicon-Based Electron Beam Transmission Window for Use in a KrF Excimer Laser System  

SciTech Connect

Princeton Plasma Physics Laboratory, in collaboration with the Naval Research Laboratory, is currently investigating various novel materials (single-crystal silicon, <100>, <110>, and <111>) for use as electron beam transmission windows in a krypton fluoride (KrF) excimer laser system. The primary function of the window is to isolate the active medium (excimer gas) from the excitation mechanism (field-emission diodes). The chosen window geometry must accommodate electron energy transfer >80% (750 keV) while maintaining the structural integrity during the mechanical load (1.3- to 2.0-atm base pressure differential, {approx}0.5-atm cyclic pressure amplitude, 5-Hz repetition rate) and the thermal load across the entire hibachi area ({approx}0.9 Wcm{sup -2}. In addition, the window must be chemically resistant to attack by fluorine free radicals (hydrofluoric acid, secondary). In accordance with these structural, functional, and operational parameters, a 22.4-mm square silicon prototype window, coated with 500-nm thin-film silicon nitride (Si{sub 3}N{sub 4}), has been fabricated. The window consists of 81 square panes 0.019 and plusmn; 0.001 mm thick. The stiffened (orthogonal) sections are 0.065 mm wide and 0.500 mm thick (approximate). Assessment of silicon (and silicon nitride) material properties and computer-aided design modeling/analysis of the window design suggest that silicon may be a viable solution to inherent parameters and constraints.

Gentile, C.A. [Princeton Plasma Physics Laboratory (United States); Fan, H.M. [Princeton Plasma Physics Laboratory (United States); Hartfield, J.W. [Princeton Plasma Physics Laboratory (United States); Hawryluk, R.J. [Princeton Plasma Physics Laboratory (United States); Heitzenroeder, P.J. [Princeton Plasma Physics Laboratory (United States); Jun, C.H. [Princeton Plasma Physics Laboratory (United States); Ku, L.P. [Princeton Plasma Physics Laboratory (United States); LaMarche, P.H. [Princeton Plasma Physics Laboratory (United States); Myers, M.C. [Naval Research Laboratory (United States); Parker, J.J. [Princeton Plasma Physics Laboratory (United States); Parsells, R.F. [Princeton Plasma Physics Laboratory (United States); Payen, M. [Princeton Plasma Physics Laboratory (United States); Raftopoulos, S. [Princeton Plasma Physics Laboratory (United States); Sethian, J.D. [Naval Research Laboratory (United States); Hegeler, F

2003-05-15

428

Micro electrochemical machining for complex internal micro features  

Microsoft Academic Search

In this paper, the application of micro electrochemical machining (ECM) for the micromachining of internal features is investigated. By controlling pulse conditions and machining time, micro features are machined on the side wall of a micro hole. These methods can easily machine a micro hole with larger internal diameters than the entrance diameter, which is very difficult to do by

Chan Hee Jo; Bo Hyun Kim; Chong Nam Chu

2009-01-01

429

Micro Electrochemical Machining for Complex Internal Micro Features  

Microsoft Academic Search

Micromachining of internal features by electrochemical machining (ECM) is investigated. By controlling pulse conditions and using a customized tool electrode, micro features were machined on the side wall of a micro hole. In micro ECM, longer pulse on-time enlarges the side gap. A reverse tapered hole and a barrel-shape hole were fabricated through pulse duration control. Micro cavity was machined

Chan Hee Jo; Bo Hyun Kim; Hong Shik Shin; Do Kwan Chung; Min Ho Kwon; Chong Nam Chu

2008-01-01

430

Analysis of Membrane Lipids of Airborne Micro-Organisms  

NASA Technical Reports Server (NTRS)

A method of characterization of airborne micro-organisms in a given location involves (1) large-volume filtration of air onto glass-fiber filters; (2) accelerated extraction of membrane lipids of the collected micro-organisms by use of pressurized hot liquid; and (3) identification and quantitation of the lipids by use of gas chromatography and mass spectrometry. This method is suitable for use in both outdoor and indoor environments; for example, it can be used to measure airborne microbial contamination in buildings ("sick-building syndrome"). The classical approach to analysis of airborne micro-organisms is based on the growth of cultureable micro-organisms and does not provide an account of viable but noncultureable micro-organisms, which typically amount to more than 90 percent of the micro-organisms present. In contrast, the present method provides an account of all micro-organisms, including cultureable, noncultureable, aerobic, and anaerobic ones. The analysis of lipids according to this method makes it possible to estimate the number of viable airborne micro-organisms present in the sampled air and to obtain a quantitative profile of the general types of micro-organisms present along with some information about their physiological statuses.

MacNaughton, Sarah

2006-01-01

431

Development of a Silicon Based Electron Beam Transmission Window for Use in a KrF Excimer Laser System  

SciTech Connect

The Princeton Plasma Physics Laboratory (PPPL), in collaboration with the Naval Research Laboratory (NRL), is currently investigating various novel materials (single crystal silicon, <100>, <110> and <111>) for use as electron-beam transmission windows in a KrF excimer laser system. The primary function of the window is to isolate the active medium (excimer gas) from the excitation mechanism (field-emission diodes). Chosen window geometry must accommodate electron energy transfer greater than 80% (750 keV), while maintaining structural integrity during mechanical load (1.3 to 2.0 atm base pressure differential, approximate 0.5 atm cyclic pressure amplitude, 5 Hz repetition rate) and thermal load across the entire hibachi area (approximate 0.9 W {center_dot} cm superscript ''-2''). In addition, the window must be chemically resistant to attack by fluorine free-radicals (hydrofluoric acid, secondary). In accordance with these structural, functional, and operational parameters, a 22.4 mm square silicon prototype window, coated with 500 nm thin-film silicon nitride (Si{sub 3}N{sub 4}), has been fabricated. The window consists of 81 square panes with a thickness of 0.019 mm {+-} 0.001 mm. Stiffened (orthogonal) sections are 0.065 mm in width and 0.500 mm thick (approximate). Appended drawing (Figure 1) depicts the window configuration. Assessment of silicon (and silicon nitride) material properties and CAD modeling and analysis of the window design suggest that silicon may be a viable solution to inherent parameters and constraints.

C.A. Gentile; H.M. Fan; J.W. Hartfield; R.J. Hawryluk; F. Hegeler; P.J. Heitzenroeder; C.H. Jun; L.P. Ku; P.H. LaMarche; M.C. Myers; J.J. Parker; R.F. Parsells; M. Payen; S. Raftopoulos; J.D. Sethian

2002-11-21

432

Idaho Micro Hydro Handbook.  

National Technical Information Service (NTIS)

This handbook addresses the development of micro-hydroelectric systems. An overview of microhydro systems, methods for determining site feasibility and guidance in system design are provided. The technology is well developed and equipment is available fro...

J. Volkman B. Eastlake

1983-01-01

433

Micro electrochemical milling  

Microsoft Academic Search

In this paper, electrochemical machining (ECM) for fabricating micro structures is presented. By applying ultra short pulses, dissolution of a workpiece can be restricted to the region very close to an electrode. Using this method, 3D micro structures were machined on stainless steel. Good surface quality of the structures was obtained in the low concentration electrolyte, 0.1 M H2SO4. In

Bo Hyun Kim; Shi Hyoung Ryu; Deok Ki Choi; Chong Nam Chu

2005-01-01

434

Micro ammonia sensor  

SciTech Connect

A micro ammoniasensor, consisting of an ISFET covered with a dry membrane which is made from nonactin and substituted poly-..gamma..-methyl-L-glutamate (PMG) is described. The gate output voltage of the micro ammonia sensor increased with NH/sub 4/OH addition. The response time of the sensor was 2 min at 30/sup 0/C, and the sensor exhibited superior selectivity for NH/sub 4//sup +/ compared to a pH sensitive ISFET.

Kubo, I.; Karube, I.; Moriizumi, T.

1986-01-01

435

Externally-resonated linear micro vibromotor for micro assembly  

Microsoft Academic Search

A new design of a linear micro vibromotor for on-substrate ne positioning of micro-scale components is presented where a micro linear slider is actuated by vibratory impacts exerted by micro cantilever impacters. These micro cantilever impacters are selectively resonated by shaking the entire substrate with a piezoelectric vibrator, requiring no need for built-in driving mechanisms such as electrostatic comb actuators

Kazuhiro Saitoua; Soungjin J. Wou

1998-01-01

436

Electrohydrodynamically augmented micro heat pipes  

Microsoft Academic Search

For high power density dissipation, micro heat pipes and micro grooves have demonstrated much promise. Several experimental investigations were conducted to evaluate the potential benefits of electrohydrodynamic (EHD) forces on the operation of micro heat pipes. In these experiments, electric fields were used to orient and guide the flow of the dielectric liquid within the micro heat pipes from the

Zhiquan Yu

2001-01-01

437

Thermal characterisation of micro-hotplates used in sensor structures  

NASA Astrophysics Data System (ADS)

Micro-hotplates operated at elevated temperature form the basic element in several sensor devices, such as integrated calorimetric or Taguchi-type gas sensors and flow-rate sensors. In all of these applications thermal properties of the sensing elements play a determining role in functional operation, therefore, their accurate characterisation is essential. The micro-hotplates investigated were developed by one side porous silicon micro-machining technology, forming Pt micro-filaments embedded in non-stoichiometric silicon nitride, and suspended across a cavity. This work is dealing with the accurate temperature detection in the micro-scale by different measurement methods for the deduction of steady state and transient thermal properties from the results. Transient properties of the structure were investigated by application of a simplified thermal equivalent circuit model.

Fürjes, P.; Dücs?, Cs.; Ádám, M.; Zettner, J.; Bársony, I.

2004-03-01