| 1. |
- Wiesner, M., et al.
(author)
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The electron-phonon interaction at deep Bi 2 Te3-semiconductor interfaces from Brillouin light scattering
- 2017
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 7:1
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Journal article (peer-reviewed)abstract
- It is shown that the electron-phonon interaction at a conducting interface between a topological insulator thin film and a semiconductor substrate can be directly probed by means of high-resolution Brillouin light scattering (BLS). The observation of Kohn anomalies in the surface phonon dispersion curves of a 50 nm thick Bi2Te3 film on GaAs, besides demonstrating important electron-phonon coupling effects in the GHz frequency domain, shows that information on deep interface electrons can be obtained by tuning the penetration depth of optically-generated surface phonons so as to selectively probe the interface region, as in a sort of quantum sonar.
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| 2. |
- Bonato, Maud, et al.
(author)
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Predicting ejaculate quality and libido in male ostriches: Effect of season and age.
- 2014
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In: Animal Reproduction Science. - : Elsevier BV. - 1873-2232 .- 0378-4320. ; 151:1-2, s. 49-55
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Journal article (peer-reviewed)abstract
- The success of artificial breeding program depends largely on the reproductive performance of males. Male performance can vary with season and age impacting on quality and quantity of semen collected for artificial insemination purposes and therefore fertility of inseminated females. We examined variation in semen output and male libido of seven male ostriches (aged 2-5 years) over a period of 24 months. We collected ejaculates using a dummy female and measured semen characteristics (ejaculate volume, sperm concentration, number of spermatozoa per ejaculate, sperm motility and morphology) and male libido (willingness to mount the dummy). A total of 1006 ejaculates were collected. Across months, the volume of semen (mean±SEM) ranged from 1.03±0.12mL to 1.85±0.07mL, the sperm concentration from 3.21±0.12×10(9)/mL to 4.16±0.74×10(9)/mL, and the number of spermatozoa from 3.42±0.28×10(9) to 7.66±0.47×10(9). The largest volume of ejaculates and the highest number of sperm were collected in spring. Ejaculates with higher number of normal sperm were also collected in spring-early summer, whereas ejaculates with higher numbers of live abnormal and dead sperm were collected in winter. Sperm motility was relatively constant over months, despite a reduction in summer (January-February), while male libido peaked in winter (June-July) and spring (October-November). Furthermore, we observed high individual variation between males for all variables tested, except for motility. These results indicate that collections conducted in spring yield higher number of spermatozoa, when the libido of males is also at a maximum. Therefore in this species seasonal variation in semen quality should be considered in breeding programmes by artificial insemination to maximise fertility.
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| 3. |
- Bonato, Maud, et al.
(author)
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The effect of temperature and pH on the motility and viability of ostrich sperm
- 2012
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In: Animal Reproduction Science. - : Elsevier BV. - 1873-2232 .- 0378-4320. ; 133:1-2, s. 123-128
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Journal article (peer-reviewed)abstract
- As the chemical environment of semen diluents can have a profound effect on sperm quality, we examined the effect of temperature and pH on the motility and viability of sperm in the ostrich. Semen was collected from four males, each male being replicated three times. Ejaculates were diluted and incubated for 10 min at 20 degrees C and 40 degrees C in four different buffers, temperature adjusted at pH 6, 7, 8 and 9 respectively. Average path velocity (VAP), curvilinear velocity (VCL), straight-line velocity (VSL), linearity (LIN), beat cross frequency (BCF) and amplitude of lateral displacement (ALH) were then recorded for each sample using CASA. The viability of sperm was assessed using nigrosin-eosin staining. Sperm incubated at 40 degrees C had higher motility parameters, except for ALH. At 40 degrees C, VAP, VSL and LIN increased with pH while VCL, BCF and ALH were higher for lower pHs. The viability of sperm was not affected by temperature but decreased at pH values > 7. A pH in the neutral range appeared to yield higher quality sperm after in vitro storage at 20 degrees C. However, the effect of different pH levels and temperatures on sperm longevity needs to be investigated further to develop viable ostrich specific diluents. (C) 2012 Elsevier B.V. All rights reserved.
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| 4. |
- Trzaskowska, A., et al.
(author)
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Dispersion of the surface phonons in semiconductor/topological insulator Si/Bi 2 Te 3 heterostructure studied by high resolution Brillouin spectroscopy
- 2021
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In: Ultrasonics. - : Elsevier BV. - 0041-624X. ; 117
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Journal article (peer-reviewed)abstract
- The dynamics and dispersion of surface phonons in heterostructure semiconductor/ topological insulator Si/Bi2Te3 was investigated using high resolution Brillouin light scattering method in the GHz frequency range. Both Rayleigh and Sezawa surface acoustic waves have been observed for wave vectors ranging from 0.006 to 0.023 nm−1. Anomaly in dispersion relations ω(q) for both surface waves were detected for the wave vector q = 0.016 nm−1. The finite element method (FEM) was used to simulate the observed shapes of ω(q) and to find the deformation profiles of surface acoustic waves. We attribute the observed changes to the coupling between low energy electrons and surface phonons. The coupling between helical Dirac states and surface phonons is discussed in the frame of accessible theoretical models.
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