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61.
The corrected cathodoluminescence (CL) emission spectrum for undeformed MgO in the wavelength range 300–650nm consists of two overlapping bands with peaks at 425 nm (2.92 eV) and 488 nm (2.54 eV). After deformation one broad band at 466 nm (2.66 eV) of much higher intensity is observed. In the near IR part of the spectrum a further broad band occurs, consisting of a number of unresolved peaks the strongest of which is at 726 nm (1.71 eV). This band is unaffected by deformation and is thought to be due to iron impurities. Panchromatic and monochromatic SEM micrographs show that the enhanced 466 nm band luminescence comes from the slipped planes of the crystal. Shape analysis of the 466 nm emission band showed that it is a Gaussian form around the intensity maximum with an exponential high energy tail. 相似文献
62.
Holt Ashley Eugene Brunelle Herbert H. Moser 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1958,9(5-6):57-80
Zusammenfassung Es wird ein Beitrag geliefert zur Stützung der schon früher ge?usserten überzeugung, dass nichtstation?re Str?mungsanteile
das Schwingungsverhalten und die aeroelastische Stabilit?t von Helikopter-Drehflügeln wesentlich beeinflussen k?nnen. Die
Untersuchung betont besonders den D?mpfungsverlust, welcher sich aus den entlang der Spannweite eines schwebenden Drehflügels
schraubenf?rmig abgehenden Wirbeln ergibt.
Gem?ss dem Bedürfnis für verbesserte Mittel zur Behandlung nichtstation?rer aerodynamischer Vorg?nge werden zwei neue theoretische
Entwicklungen beschrieben und zum Berechnen von Luftkr?ften auf typische schwingende Drehflügel angewendet.
Die erste dieser Arbeiten erfasst auf zweidimensionaler Basis das Vorhandensein einer Bodenebene. Es wird angenommen, dass
die Wirbel im Abwinde des schwebenden Drehflügels durch die Bodenebene nicht zurückgeworfen, sondern schnell zerstreut werden.
Als Resultat zeigt sich, dass die einer spezifischen Schwingungsform entsprechende aerodynamische D?mpfung durch den Einfluss
des Bodens, der praktisch etwa zwei Drehflügel-Durchmesser hinaufreicht, im allgemeinen vergr?ssert wird.
Die zweite der vorgelegten Theorien betrifft die dreidimensionale Str?mung über ein schwingendes Flügelblatt, welches als
tragende Linie und unter Vernachl?ssigung der Krümmung seines Abwindes untersucht wird. Numerische Rechnungen sind ziemlich
mühsam, aber mittels Rechenmaschinen ohne weiteres durchführbar. In einem herausgegriffenen typischen Beispiele zeigte sich,
dass die Luftkr?fte bedeutend kleiner sind als die von der Streifentheorie angezeigten, dass aber die Phasendifferenz zwischen
Anstellwinkel und Luftkr?ften fast unver?ndert bleibt.
This investigation was performed under USAF Contract AF33(616)-3270 sponsored jointly by the US Army and Dynamics Branch of the Aircraft Laboratory, Wright Air Development Center. 相似文献
This investigation was performed under USAF Contract AF33(616)-3270 sponsored jointly by the US Army and Dynamics Branch of the Aircraft Laboratory, Wright Air Development Center. 相似文献
63.
64.
Abstract High temperature gas release from helium-implanted palladium has been investigated for He/Pd atom fractions from 5 × 10?6 to 5 × 10?2. The temperature required for 25 per cent He release increases with increasing dose to an atom fraction of 10?4, where a sudden reversal occurs for higher concentrations. The release is associated with dramatic changes in the surface features of the palladium. A qualitative physical model is presented to explain the data. 相似文献
65.
Scanning electron microscopy has been used to examine bulk phenomena of palladium samples annealed at 1200°C after implantation to a dose of 1017 He atoms/cm2 at 5 MeV. A 3μ deep porous layer was found at a depth of 10.9μ±0.3μ. Wide grain boundaries (microcracks) extended from this layer to the top surface of the sample. 相似文献
66.
Cletus A D'Souza Vikramjit Chopra Richard Varhol Yuan-Yun Xie Slavita Bohacec Yongjun Zhao Lisa LC Lee Mikhail Bilenky Elodie Portales-Casamar An He Wyeth W Wasserman Daniel Goldowitz Marco A Marra Robert A Holt Elizabeth M Simpson Steven JM Jones 《BMC neuroscience》2008,9(1):1-14
Background
We have recorded responses from single neurons in murine visual cortex to determine the effectiveness of the input from the two murine cone photoreceptor mechanisms and whether there is any unique selectivity for cone inputs at this higher region of the visual system that would support the possibility of colour vision in mice. Each eye was stimulated by diffuse light, either 370 (strong stimulus for the ultra-violet (UV) cone opsin) or 505 nm (exclusively stimulating the middle wavelength sensitive (M) cone opsin), obtained from light emitting diodes (LEDs) in the presence of a strong adapting light that suppressed the responses of rods.Results
Single cells responded to these diffuse stimuli in all areas of striate cortex. Two types of responsive cells were encountered. One type (135/323 – 42%) had little to no spontaneous activity and responded at either the on and/or the off phase of the light stimulus with a few impulses often of relatively large amplitude. A second type (166/323 – 51%) had spontaneous activity and responded tonically to light stimuli with impulses often of small amplitude. Most of the cells responded similarly to both spectral stimuli. A few (18/323 – 6%) responded strongly or exclusively to one or the other spectral stimulus and rarely in a spectrally opponent manner.Conclusion
Most cells in murine striate cortex receive excitatory inputs from both UV- and M-cones. A small fraction shows either strong selectivity for one or the other cone mechanism and occasionally cone opponent responses. Cells that could underlie chromatic contrast detection are present but extremely rare in murine striate cortex. 相似文献67.
Carter J. Holt Katelyn J. Wentworth Richard P. Johnson 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(44):15940-15943
Triangulenes are of current interest for potential applications in molecular electronics. We describe here a three step synthesis of the 4,8,12‐trihydro[3]triangulenium cation by cascade cyclization of a tetra‐benzyl alcohol precursor in triflic acid solution. This stable carbocation is easily observed by NMR and optical spectroscopy and is highly fluorescent. Quenching of the cation into basic solutions or by hydride transfer from triethylsilane provides access to stable dihydro and tetrahydro[3]triangulenes. These neutral species interconvert with cations in a complex series of proton and hydride transfers. This route provides several important [3]triangulene precursors. Preliminary experiments designed to generate [3]triangulene in the solution phase provide evidence for its formation and rapid oligomerization. 相似文献
68.
H. Mkrtchyan P.E. Bosted G.S. Adams A. Ahmidouch T. Angelescu J. Arrington R. Asaturyan O.K. Baker N. Benmouna C. Bertoncini H.P. Blok W.U. Boeglin H. Breuer M.E. Christy S.H. Connell Y. Cui M.M. Dalton S. Danagoulian D. Day T. Dodario J.A. Dunne D. Dutta N. El Khayari R. Ent H.C. Fenker V.V. Frolov L. Gan D. Gaskell K. Hafidi W. Hinton R.J. Holt T. Horn G.M. Huber E. Hungerford X. Jiang M. Jones K. Joo N. Kalantarians J.J. Kelly C.E. Keppel V. Kubarovsky Y. Li Y. Liang S. Malace P. Markowitz E. McGrath P. McKee D.G. Meekins B. Moziak T. Navasardyan 《Physics letters. [Part B]》2008
69.
Dr. Lidia A. Maslovskaya Dr. Andrei I. Savchenko Prof. Elizabeth H. Krenske Dr. Sharon Chow Tina Holt Dr. Victoria A. Gordon Dr. Paul W. Reddell Carly J. Pierce Prof. Peter G. Parsons Prof. Glen M. Boyle Prof. Andrei G. Kutateladze Prof. Craig M. Williams 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(51):11862-11867
Structurally unique halimanes EBC-232 and EBC-323, isolated from the Australian rainforest plant Croton insularis, proved considerably difficult to elucidate. The two diastereomers, which consist an unusual oxo-6,7-spiro ring system fused to a dihydrofuran, were solved by unification and consultation of five in silico NMR elucidation and prediction methods [i.e., ACDLabs, olefin strain energy (OSE), DP4, DU8+ and TD DFT CD]. Structure elucidation challenges of this nature are prime test case examples for empowering future AI learning in structure elucidation. 相似文献
70.
Fatima Erragh Ali Boukhari Brahim Elouadi Elizabeth M. Holt 《Journal of chemical crystallography》1991,21(3):321-326
Na2CoP2O7 may be prepared in two allotropie forms:I, rose,M
r
=278.85, triclinic, P1,a=9.735(2),b=10.940(3),c=12.289(4) Å,=148.78,=121.76(1), =68.38(2)°,V=566.8(2) Å3,Z=4,D
meas=3.28(5) g cm–3,D
calc=3.267 g cm–3, (MoK)=0.71069 Å,=37.12 cm–1, F(000)=540,T=298 K,R=5.4% for 2911 observed reflections; andII, blue,M
r
=278.85, orthorhombic, P21cn,a=7.713(2) Å,b=10.271(4),c=15.378(6)°,V=1218.2(8) Å3,Z=8,D
meas=3.06(5) g cm–3,D
calc=3.040 g cm–1, (MoK
) Å,=34.55 cm–1, F(000)=1080,T=298 K,R=9.9% for 1450 observed reflections. Cobalt displays octahedral coordination to six oxygen atoms in the rose form whereas the metal coordination is tetrahedral in the blue form. 相似文献