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131.
H. Preier M. Bleicher W. Riedel H. Pfeiffer H. Maier 《Applied Physics A: Materials Science & Processing》1977,12(3):277-281
PbS−PbSe−PbS double-heterostructure lasers have been pulse-operated at about 200 K mounted on 4 stage thermoelectric coolers.
Emitting at a wavelength of about 5.5 μm they could be used for NO gas spectroscopy. Operation temperatures of up to 230 K
have been achieved with structures consisting ofn-type PbS substrates and epitaxial layers ofn-type PbSe and Tl dopedp-type PbS. The temperature dependence of the threshold current density and the emission wavelength of these DH-lasers was
compared with PbSe-homojunction lasers. The use of a germanium etalon for a quick evaluation of the spectral quality of the
emitted radiation is described. 相似文献
132.
133.
Juha?M.?Saarela Torbj?rn?L?fqvist Kerstin?Ramser Per?Gren Erik?Olson Jan?Niemi Mikael?Sj?dahl 《Central European Journal of Physics》2010,8(2):235-241
This study is focused on exploring the feasibility of an all-optic surface scanning method in determining the size and position
of a submerged, laser generated, optoacoustic (OA) source. The optoacoustic effect in this case was generated when the absorption
of a short electromagnetic pulse in matter caused a dielectric breakdown, a plasma emission flash and a subsequent acoustic
wave. In the experiment, a laser pulse with λ = 1064 nm and 12 ns pulse length was aimed at a volume of deionized water. When
the laser beam was focused by a f = 16 mm lens, a single dielectric breakdown spot occurred. When a f = 40 mm was used several breakdowns in a row were induced. The breakdowns were photographed using a double shutter camera.
The acoustic wave generated by the dielectric breakdowns were detected at a point on the water surface using a laser Doppler
vibrometer (LDV). First, the LDV signal was used to calculate the speed of sound with an accuracy of 10 m/s. Secondly, the
location and length of the dielectric breakdown was calculated with an accuracy of 1 mm. The calculated position matched the
breakdown location recorded by a camera. The results show that it is possible to use LDV surface measurements from a single
spot to determine both the position and length of the OA source as well as the speed of sound in the medium. Furthermore,
the LDV measurements also show a secondary peak that originates from the OA source. To unravel the origin and properties of
this interesting feature, further investigations are necessary 相似文献
134.
Background
Infections with respiratory viruses can activate the innate immune response - an important host defence mechanism in the early stage of viral infection. Interferon (IFN) release, triggered by virus infection, is an important factor in establishing an antiviral state, where IFN activation occurs prior to the onset of the adaptive immune response. 相似文献135.
Martin M Lastapis M Riedel D Dujardin G Mamatkulov M Stauffer L Sonnet P 《Physical review letters》2006,97(21):216103
At low temperature (5 K), a single biphenyl molecule adsorbed on a Si(100) surface behaves as a bistable device which can be reversibly switched by electronic excitation with the scanning tunneling microscope tip. Density functional theory suggests that the biphenyl molecule is adsorbed with one dissociated hydrogen atom bonded to a neighbor surface silicon atom. By desorbing this hydrogen atom with the STM tip, the interaction of the molecule with the surface is modified such that it becomes transformed into a multistable device with four stable states having switching yields increased by almost 2 orders of magnitude. 相似文献
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138.
The velocity distribution of liquid flowing in a commercial micromixer has been determined directly by using pulsed-field gradient NMR. Velocity maps with a spatial resolution of 29 microm x 43 microm were obtained by combining standard imaging gradient units with a homebuilt rectangular surface coil matching the mixer geometry. The technique provides access to mixers and reactors of arbitrary shape regardless of optical transparency. Local heterogeneities in the signal intensity and the velocity pattern were found and serve to investigate the quality and functionality of a micromixer, revealing clogging and inhomogeneous flow distributions. 相似文献
139.
Ghasparian A Moehle K Linden A Robinson JA 《Chemical communications (Cambridge, England)》2006,(2):174-176
A crystal structure is reported of the peptide Ac-Ala-Asn-Pro-Asn-Ala-NH2, representing the immunodominant region of the major surface protein on the malaria parasite; the NPNA motif adopts a type-I beta-turn, which is stabilized by hydrogen bonding between the CO of Asn2 and the NH of Ala5 as well as between the O(delta) of Asn2 and the NH of Asn4. 相似文献
140.