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1.
The mid-infrared (1500-3800 cm−1) absorption spectrum of gaseous nitric oxide has been studied at low temperature (99 K) with a long absorption path (160 m) in order to observe weak combination, difference, and overtone bands of the NO dimer. About ten new bands were assigned with greater or lesser certainty. Combined with previous results, they lead to a set of 12 secure and 7 tentative vibrational term values for (NO)2, essentially doubling our knowledge of NO dimer vibrational states. The strongest non-fundamental bands in this region, other than the ν1 (symmetric N-O stretch) + ν5 (asymmetric N-O stretch) overtone, involve combinations of ν5 with ν3 (intermolecular stretch). Excitation of ν5 results in increased frequencies for the intermolecular modes ν2, ν3, and ν4. A new value of 155.5 cm−1 was obtained for ν4, the elusive infrared-inactive out-of-plane fundamental vibration. 相似文献
2.
A variety of dolphin sonar discrimination experiments have been conducted, yet little is known about the cues utilized by dolphins in making fine target discriminations. In order to gain insights on cues available to echolocating dolphins, sonar discrimination experiments were conducted with human subjects using the same targets employed in dolphin experiments. When digital recordings of echoes from targets ensonified with a dolphinlike signal were played back at a slower rate to human subjects, they could also make fine target discriminations under controlled laboratory conditions about as well as dolphins under less controlled conditions. Subjects reported that time-separation-pitch and duration cues were important. They also reported that low-amplitude echo components 32 dB below the maximum echo component were usable. The signal-to-noise ratio had to be greater than 10 dB above the detection threshold for simple discrimination and 30 dB for difficult discrimination. Except for two cases in which spectral cues in the form of "click pitch" were important, subjects indicated that time-domain rather than frequency-domain processing seemed to be more relevant in analyzing the echoes. 相似文献
3.
By means of our proposed method for Hückel theory calculation, we have calculated the electronic structures of dihedral (D5h, D5d, D6h, D6d) fullerences, which are generated from icosahedral C20, C60, C80, C180, C240 and C540, respectively. From the calculated results of 1224 fullerence molecules, certain rules on the stability and chemical reactivity have been drawn for such types of dihedral fullerenes. 相似文献
4.
Žydrė Šaltienė Natalija Jatulienė Mudis Šalkauskas Daiva Brukštienė Asta Ruzgytė Aušra Tarasevičiūtė Julius Kalibatas 《Accreditation and quality assurance》2005,10(8):444-451
The estimation scheme of uncertainty of determination of 1-hydroxypyrene (1-OHP) in urine was developed analysing the main
stages of the analytical procedure: (1) preparation of 1-OHP standards, (2) creation of the calibration curve for the high
performance liquid chromatography (HPLC) analysis method with the evaluation of recovery, (3) measuring procedure of aliquot
of urine, (4) adjusting the pH of aliquot and hydrolysis with enzyme, (5) solid phase extraction, (6) concentration of the
extract, (7) injection of the extract to chromatograph and analysing by the HPLC method, (8) calculation of 1-OHP mass from
the calibration curve, (9) calculation of 1-OHP concentration in urine. The evaluation of the uncertainty is based on quantification
of individual components. Combined uncertainty was calculated using the law of propagation of uncertainties according to the
EURACHEM/CITAC guidelines. Level dependence of the uncertainty arises from the calibration curve.
The limits of detection and quantification were found to be equal to 0.03 and 0.1 ng/mL, respectively. The calculated expanded
level-dependent uncertainty covers 47–27–25% within the concentration range 0.03–0.1–0.4 ng/mL with the materials and equipment
used. These parameters could easily be recalculated according to the proposed scheme if there are some changes in the analysis
procedure. 相似文献
5.
Adam D. Martin Jonathan P. Wojciechowski Eric Y. Du Aditya Rawal Holly Stefen Carol G. Au Liming Hou Charles G. Cranfield Thomas Fath Lars M. Ittner Pall Thordarson 《Chemical science》2020,11(5):1375
Peptide-based nanofibres are a versatile class of tunable materials with applications in optoelectronics, sensing and tissue engineering. However, the understanding of the nanofibre surface at the molecular level is limited. Here, a series of homologous dilysine–diphenylalnine tetrapeptides were synthesised and shown to self-assemble into water-soluble nanofibres. Despite the peptide nanofibres displaying similar morphologies, as evaluated through atomic force microscopy and neutron scattering, significant differences were observed in their ability to support sensitive primary neurons. Contact angle and labelling experiments revealed that differential presentation of lysine moieties at the fibre surface did not affect neuronal viability; however the mobility of phenylalanine residues at the nanofibre surface, elucidated through solid- and gel-state NMR studies and confirmed through tethered bilayer lipid membrane experiments, was found to be the determining factor in governing the suitability of a given peptide as a scaffold for primary neurons. This work offers new insights into characterising and controlling the nanofibre surface at the molecular level.The mobility of hydrophobic moieties at a peptide nanofibre surface determines its suitability as a scaffold for sensitive primary cells. 相似文献
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8.
Structures of the double perovskites Ba2M(II)M ′(VI)O6 (M=Ca, Sr, M′=Te, W, U) at room temperature have been investigated by the Rietveld method using X-ray and neutron powder diffraction data. For double perovskites with M=Sr, the observed space groups are I2/m (M′ =W) and (M′=Te), respectively. In the case of M=Ca, the space groups are either monoclinic P21/n (M′=U) or cubic (M′=W and Te). The tetragonal and orthorhombic symmetry reported earlier for Ba2SrTeO6 and Ba2CaUO6, respectively, were not observed. In addition, non-ambient X-ray diffraction data were collected and analyzed for Ba2SrWO6 and Ba2CaWO6 in the temperature range between 80 and 723 K. It was found that the rhombohedral structure exists in Ba2SrWO6 above room temperature between the monoclinic and the cubic structure, whereas the cubic Ba2CaWO6 undergoes a structural phase transition at low temperature to the tetragonal I4/m structure. 相似文献
9.
Ce0.6Zr0.35Y0.05O2和Pr0.6Zr0.35Y0.05O2催化剂表面上CO氧化和18O-16O交换反应的研究 总被引:5,自引:0,他引:5
测定了在Ce0.6Zr0.4O2,Ce0.6Zr0.35Y0.05O2,Pr0.6Zr0.4O2和Pr0.6Zr0.35Y0.05O2 (分别表示为CZ,CYZ,PZ和PYZ)样品表面上的CO氧化反应和18O-16O 同位素交换反应.结果表明: 在CZ和PZ系列固熔中掺杂Y3 离子可以改善晶格氧的迁移速度;PZ和PZY的晶格氧比CZ 和CZY 的晶格氧具有更高的氧化反应活性.其原因是将Y3 掺杂到Ce0.6Zr0.4O2 或Pr0.6Zr0.4O2晶格中,增加了样品的氧空位浓度,从而提高了晶格氧的迁移性质,而PrOx比CeO2具有更低温度的氧化还原性质,因此PZ和PZY的晶格氧比CZ 和CZY 的晶格氧具有更高的氧化反应活性. 相似文献
10.
在Al-P-Ti-Si-O催化剂上由甲醇和邻苯二酚合成愈创木酚的研究 总被引:7,自引:0,他引:7
采用非均匀沉淀法制备了Al1P1.30TiaSib(a=0-0.51,b=0-0.90)复合催化剂,研究了邻苯二酚与甲醇在该催化剂上的气相o-甲基化反应。结果表明,催化剂组成、相结构和表面性质对催化剂的活性和选择性有很大影响。其中Al1P1.30Ti0.30si0.17催化剂的愈创木酚收率最高,在反应温度为553K时,邻苯二酚转化率和愈创木酚收率分别为92%和86%。 相似文献