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61.
Microprojectile methods of genetic engineering sometimes employ a macroprojectile which launches the microprojectiles when it hits a stopping plate. A study has been made of the relationship between the velocities of the macroprojectile and the microprojectile it launches. Macroprojectile velocities were measured using a beam blanking method and the microprojectile velocities were measured with a laser Doppler anemometer. Particles of tungsten, titanium dioxide and silicon carbide were investigated as microprojectiles. The microprojectile velocity was found to depend not only on the macroprojectile velocity but also on the microprojectile size and material, the bond strength with the macroprojectile and the gas flow that develops ahead of the macroprojectile. On average the microprojectile launch velocity was similar to the macroprojectile velocity. However, some tungsten particles had velocities twice this value. Experimental evidence suggests that these higher velocities were caused by early break-way of particles from the macroprojectile followed by further acceleration by aerodynamic drag arising from the gas flow ahead of the macroprojectile.We are especially grateful for the advice of Dr. M. Gharib on the use of the HSI color system. John Lyons provided expert help in the laboratory and materials for and advice on photography. We thank the staff of the SIO Hydraulics Laboratory for making the wind-wave channel available for our use, and the staff of UCSD library for enabling us to use the Barneyscanner photometer-digitizer. We thank an anonymous reviewer who pointed out a numerical error and improved the clarity of the text. 相似文献
62.
It has been reported that the introduction of a dielectric barrier between adjacent digits of an interdigitated electrode array can improve the sensitivity of the array as an electrochemical impedance biosensor. Here we present an in‐depth analysis of the impedance in planar interdigitated electrodes and 3‐D interdigitated electrodes (with dielectric barriers). The analysis indicates that the planar geometry not only provides lower impedance but also a higher change impedance as a result of molecular immobilization on the electrode array surface. 相似文献
63.
Edwards HG Herschy B Page K Munshi T Scowen IJ 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(1):191-195
The aim of this work is to investigate the viability and potential of three groups of organic compounds as biomarkers in a future robotic analytical exploration of Mars. The three compounds have been identified as suitable candidates for potential biomarkers for extant or extinct life from the terrestrial fossil record. The three groups of compound were all similar in structure, being either tetra- or penta-cyclic compounds. The limits of detection for a sample were also tested to estimate what concentrations it would still be amenable to Raman spectroscopic investigation. This was investigated using both solid mixtures and liquid solutions. The spectra of these compounds are characterised so that they can be added to the Raman database for future Mars missions. This involved identifying functional group characteristics, assigning peaks for each individual sample and characteristic features which would categorise the samples. 相似文献
64.
R.-D. Herzberg N. Amzal J.E. Bastin F. Becker P.M.T. Brew P.A. Butler A.J.C. Chewter J.F.C. Cocks O. Dorvaux K. Eskola J. Gerl P.T. Greenlees N.J. Hammond K. Hauschild K. Helariutta F. Heßberger M. Houry A. Hürstel R.D. Humphreys G.D. Jones P.M. Jones R. Julin S. Juutinen H. Kankaanpää H. Kettunen T.L. Khoo W. Korten P. Kuusiniemi Y. Le Coz M. Leino A.P. Leppänen C.J. Lister R. Lucas M. Muikku P. Nieminen R.D. Page T. Page P. Rahkila P. Reiter Ch. Schlegel C. Scholey G. Sletten O. Stezowski Ch. Theisen W.H. Trzaska J. Uusitalo H.J. Wollersheim 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):205-208
In-beam conversion electron spectroscopy experiments have been performed on the transfermium nuclei 253, 254No using the conversion electron spectrometer SACRED in nearly collinear geometry in conjunction with the gas-filled separator
RITU at the University of Jyv?skyl?. The experimental setup is discussed and the spectra are compared to Monte Carlo simulations.
The implications for the ground-state configuration of 253No are discussed.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: rdh@ns.ph.liv.ac.uk
RID="b"
ID="b"Present address: GANIL, F-14021 Caen, France.
RID="c"
ID="c"Permanent address: IReS Strasbourg, IN2P3-CNRS, F-67037-Strasbourg, France.
RID="d"
ID="d"Present address: CEA/DIF DCRE/SDE/LDN F-91680 Bruyeres-le-Chatel.
RID="e"
ID="e"Present address: Daresbury Laboratory, Daresbury WA4 4AD, UK.
RID="f"
ID="f"Permanent address: IPN Lyon, IN2P3-CNRS, F-69037 Lyon, France. 相似文献
65.
Extensive studies have been carried out on the optical conversion of F and F-aggregate colour centres produced in lithium
fluoride single crystal on gamma irradiation. Using 308 nm XeCl laser it has been shown that significantly large population
build-up of F
3
+
centre and reduction in the population of undesirable F2 centres can be achieved in gamma irradiated crystal at room temperature due to multistep photoionization processes. These
and other investigations have provided a scheme for possible laser action based on F
3
+
colour centres in LiF crystal at room temperature. 相似文献
66.
Philip C. Bulman Page Genna A. Parkes Harry Heaney J. Steven Wailes 《Tetrahedron letters》2008,49(49):6951-6954
A number of oxazolidines derived from ketones and aminoalcohols have been prepared in excellent yields using microwave irradiation. In most cases, conventional reflux failed to provide any of the desired products. 相似文献
67.
It is shown how the invariance of the Born—Oppenheimer potential energy to overall translations and rotations of a molecule can be used to reduce the computational labor required for derivative evaluations at various orders. 相似文献
68.
69.
Numerical solutions have been obtained for the exact equations describing the propagation of periodic axisymmetric waves in a rigid cylindrical tube. Results were obtained for air over a range of conditions corresponding to shear wave numbers (s = R √?ω/μ) from 0·2 to 5000 and reduced frequencies (k = ωR/a) from 0·01 to 6. For conciseness and convenient application, the results for the attenuation and phase shift coefficients are given in the form of simple polynomials for the ranges 5 ? s ? 5000 and 0·01 ? k ? 6. This range covers virtually all values of tube diameter and sound frequency likely to be met in practical situations that are consistent with a continuum gas model. 相似文献
70.