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Jun 2008

Volume 79, Issue 6, Articles (06xxxx)

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Rev. Sci. Instrum. 79, 061301 (2008); http://dx.doi.org/10.1063/1.2938864 (11 pages)

John Melcher, Shuiqing Hu, and Arvind Raman

VEDA: Virtual Environment for Dynamic Atomic Force Microscopy, is a web-based suite of tools for the mathematical simulation of tip-sample interactions, probe dynamics, imaging instabilities and feedback control in the Atomic Force Microscope. The tools are freely accessible from the portal http://www.nanohub.org.

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A new photolysis laser-induced fluorescence instrument for the detection of H2O and HDO in the lower stratosphere

J. M. St. Clair, T. F. Hanisco, E. M. Weinstock, E. J. Moyer, D. S. Sayres, F. N. Keutsch, J. H. Kroll, J. N. Demusz, N. T. Allen, J. B. Smith, J. R. Spackman, and J. G. Anderson

Rev. Sci. Instrum. 79, 064101 (2008); http://dx.doi.org/10.1063/1.2940221 (14 pages) | Cited 5 times

Online Publication Date: 16 June 2008

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We present a new instrument, Hoxotope, for the in situ measurement of H2O and its heavy deuterium isotopologue (HDO) in the upper troposphere and lower stratosphere aboard the NASA WB-57. Sensitive measurements of δD are accomplished through the vacuum UV photolysis of water followed by laser-induced fluorescence detection of the resultant OH and OD photofragments. The photolysis laser-induced fluorescence technique can obtain S/N>20 for 1 ppbv HDO and S/N>30 for 5 ppmv H2O for 10 s data, providing the sensitivity required for δD measurements in the tropopause region. The technique responds rapidly to changing water concentrations due to its inherently small sampling volume, augmented by steps taken to minimize water uptake on instrument plumbing. Data from the summer 2005 Aura Validation Experiment Water Isotope Intercomparison Flights (AVE-WIIF) out of Houston, TX show agreement for H2O between Hoxotope and the Harvard water vapor instrument and for HDO between Hoxotope and the Harvard ICOS water isotope instrument, to within stated instrument uncertainties. The successful intercomparison validates Hoxotope as a credible source of δD data in the upper troposphere and lower stratosphere.
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93.90.+y Other topics in geophysical observations, instrumentation, and techniques (restricted to new topics in section 93)
92.60.hd Stratospheric composition and chemistry
92.60.hf Tropospheric composition and chemistry, constituent transport and chemistry
92.60.Jq Water in the atmosphere

A new instrument for automated microcontact printing with stamp load adjustment

Elie Bou Chakra, Benjamin Hannes, Gilles Dilosquer, Colin D. Mansfield, and Michel Cabrera

Rev. Sci. Instrum. 79, 064102 (2008); http://dx.doi.org/10.1063/1.2936259 (9 pages) | Cited 9 times

Online Publication Date: 30 June 2008

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An instrument for automated microcontact printing (μCP) on microscope slides is described. The movement of the stamp, which is actuated by a computer controlled pneumatic actuator, is precisely guided until it makes contact with the substrate. As a consequence, the absolute position of the microprinted patterns is reproducible over a series of substrates with 1 μm standard deviation. Exchange of substrates and stamps is a quick and simple procedure. This makes possible the microprinting of adjacent or superimposable patterns, with different products, in a reproducible manner. Furthermore, a novel approach is described for adjusting the load on the stamp during contact. Two adjustable screws are set up so that their length (with reference to the substrate holder) limits the stamp compression during contact. The load on the stamp is proportional to the stamp compression and from the experimental point of view, this is controlled by the operator adjusting the screws. This makes possible the μCP with stamps incorporating large surface features as well as stamps with isolated features raised on the surface. For proof of concept, automated μCP of a single parallelepiped polydimethylsiloxane feature, with a surface of 2 cm×30 μm and a height of 25 μm, is demonstrated inside a microfluidic channel without roof collapse. A second example is provided with a single cross feature, possessing an overall surface of 140×140 μm2 and a height of 14 μm. Potential applications of this versatile, inexpensive and compact instrument are discussed. The machine’s potential for high throughput also makes it suitable for mass production applications.
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85.40.Hp Lithography, masks and pattern transfer
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
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