519 research outputs found
The Δρομοδείχτης της Ελλάδος of 1824 and Athanasios Stageirites (Τίτλος περίληψης)
No full textσ. [281]-290Κείμενο στα ελληνικά με περίληψη στα αγγλικά με τον τίτλο: The Δρομοδείχτης της Ελλάδος of 1824 and Athanasios StageiritesThe article first examines the close relationship between the publication “Δρομοδείχτης της Ελλάδος” [1824] and the publication “Ηπειρωτικά” (1819) by Athanasios Stageirites and then suggests that Athanasios Stageirites is the likeliest author of the “Δρομοδείχτης της Ελλάδος”.Δωδώνη: Τεύχος Πρώτο: επιστημονική επετηρίδα του Τμήματος Ιστορίας και Αρχαιολογίας της Φιλοσοφικής Σχολής του Πανεπιστημίου Ιωαννίνων; Τόμ. 43-44 (2014-2015
On-target delivery of intense ultrafast laser pulses through hollow-core anti-resonant fibers
No full textWe report the flexible on-target delivery of 800 nm wavelength, 5 GW peak power, 40 fs duration laser pulses through an evacuated and tightly coiled 10 m long hollow-core nested anti-resonant fiber by positively chirping the input pulses to compensate for the anomalous dispersion of the fiber. Near-transform-limited output pulses with high beam quality and a guided peak intensity of 3 PW/cm² were achieved by suppressing plasma effects in the residual gas by pre-pumping the fiber with laser pulses after evacuation. This appears to cause a long-term removal of molecules from the fiber core. Identifying the fluence at the fiber core-wall interface as the damage origin, we scaled the coupled energy to 2.1 mJ using a short piece of larger-core fiber to obtain 20 GW at the fiber output. This scheme can pave the way towards the integration of anti-resonant fibers in mJ-level nonlinear optical experiments and laser-source development
Generation of deep ultra-violet pulses in hollow capillary fibres
No full textFemtosecond pulses in the deep ultraviolet region (DUV, 200-400 nm) are in high
demand for time-resolved studies in several fields of research such as quantum chemistry (UV photoelectron spectroscopy), material sciences (lithography in semiconductors, polymers) and biology (protein analysis, DNA sequencing, cell imaging). When
combined with external polarization control, they can provide excellent tools for chiral
molecule analysis and ultrafast magnetism studies.
A well-established route for the generation of linearly polarized pulses in the DUV has
been via frequency up-conversion in bulk materials such as nonlinear crystals or gases.
However, the former suffer from limited transmission range, narrow phase-matching bandwidths and low intensity damage thresholds while the latter require high-peak power and
provide low frequency up-conversion efficiencies. For circularly polarized pulses in the
DUV, an additional stage for polarization conversion is required, commonly implemented
by using phase retarders in the ultraviolet. This induces unwanted dispersion that compromises ultra-short duration and achromatic phase retardation.
This thesis focuses on the experimental generation of high-energy, ultrashort DUV
pulses with controlled polarization using two alternative frequency up-conversion techniques in hollow capillary fibres; four-wave mixing and resonant dispersive wave emission. Using the first technique, record-breaking energy conversion efficiency up to 50%
and large spectral bandwidths in the DUV with high pulse energy are demonstrated with
linear polarization. This scheme is then extended to achieve direct generation of DUV
pulses with circular polarization without the need for dispersive optics in the UV. Using
resonant dispersive wave emission, high energy, circularly polarized pulses tunable across
the DUV are generated when driven by circularly polarized 800 nm pulses.
These studies allow to experimentally verify the polarization-induced dynamics with
respect to fundamental science such as the angular momentum conservation and the energy scaling of nonlinearity. Although this work is focused on DUV generation, the same
techniques can be applied to other spectral regions such as the vacuum-ultraviolet (VUV,
100-200 nm) and the mid-infrared (mid-IR, 3-8 µm) by proper selection of the driving
frequencies, and can be scaled up in output energy using larger fibre systems
Dataset in support of the Southampton doctoral thesis 'The boatbuilding tradition of the Aegean during the Late Neolithic – Early Bronze Age periods. Typological classification, digital reconstruction and seakeeping assessment'
No full textDataset in support of the Southampton doctoral thesis 'The boatbuilding tradition of the Aegean during the Late Neolithic – Early Bronze Age periods. Typological classification, digital reconstruction and seakeeping assessment' Appendix D - Resistance data and Appendix C - Stability data.
This dataset is focused on two appendices:
Appendix D - Resistance data. D.1 Resistance data produced by the author via MAXSURF Resistance for this thesis.
Appendix C - Stability data
C1. Stability data – STIX and ISO criteria, produced by the author via MAXSURF Stability software for his thesis
This research was funded by Southampton Marine and Maritime Institute (SMMI), Vice-Chancellor's Scholarship, Greek Archaeological Committee UK (GACUK)
</span
Peak power reduction algorithms in asymmetric digital subscriber line modems
No full textThesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.Includes bibliographical references (leaves 94-96).This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.This thesis investigates peak-to-average ratio (PAR) reduction techniques for multicarrier modulation systems, such as discrete multitone (DMT) modems and orthogonal frequency-division multiplexed (OFDM) terrestrial broadcast transmitters. Through simulation and test implementation on a state-of-the-art programmable ADSL development platform, this thesis pursues a suitable solution for minimizing PAR given the resources of a programmable platform. This solution is integrated as a prototype implementation into a fully-functional ADSL modem and optimized for maximum PAR reduction performance within modem complexity constraints.by Athanasios Dimitri Dousis.M.Eng
Broadband Ultraviolet Generation with 50% Conversion Efficiency in Hollow Capillary Fibers
No full textWe demonstrate broadband wavelength up-conversion (240–320 nm) based on a seeded four-wave mixing scheme in gas-filled stretched hollow-capillary fibers with 50% conversion efficiency. Our technique is scalable in energy from the nJ to mJ level
Homophobic Statements, a Bishop, and the Limits of Freedom of Expression. An In-Depth Commentary on ECtHR 31.08.2023, Amvrosios-Athanasios Lenis v. Greece, no. 47833/20
No full textDichiarazioni omofobe, un vescovo e i limiti della libertà di espressione. Un commento approfondito su CEDU 31.08.2023, Amvrosios-Athanasios Lenis v. Greece, no. 47833/20.
ABSTRACT: The decision of the ECtHR of 31.08.2023, Amvrosios-Athanasios Lenis v. Greece (no. 47833/20), is a further step toward an increasingly dense jurisprudence on “hate speech” and the limits of freedom of expression. The public proclamation of religious doctrines that are in conflict with the values of the contracting States enshrined in the ECHR is protected to a certain extent by the fundamental right of freedom of religion and belief. However, the qualification of a statement as religious does not justify “hate speech.” The AUTHOR shows the tension between freedom of religion, freedom of expression, and protection against discrimination, and analyzes the decision against the backdrop of Article 17 of the ECHR (prohibition of abuse of rights).
SOMMARIO: 1. Preliminary Remarks - 2. The Concept of Hate Speech - 3. The Facts of the Case - 4. The Procedure and Reasoning of the Court - 4.1 The ECtHR’s Preliminary Considerations on Fundamental Rights - 4.2 Legal assessment - 4.3 Some Remarks on (the Non-Invoked) Article 9 of the ECHR - 5. Concluding Remarks
La tomba III di Haghios Athanasios e il valore semantico dell'incarnato
No full textThe tomb III at Haghios Athanasios stands out among the Macedonian tombs for the exceptional painted decoration of the temple-like façade. Excavated in the '90s by M. Tsimbidou-Avloniti it has been published by the scholar in full detail and the iconographic program of the monument has been the object of many publications. This article re-examines the different ways of reproducing the skin color (το ανδρείκελον) in the figures of the miniature frieze and in the megalographic figures beside the door. The realistic rendering of the megalographic figures of armed men in Macedonian attire, showing their sorrow for the lost of an etairos, is contrasting with the pale color of the participants to the symposion in the frieze above the door, a scene whose illusionistic overtone has been yet perceived by the critics. This symposion is articulated in three scenes and it can be interpeted as a necrodeipnon, but in the same time as a celebration of the Macedonian banquet style, centered on the royal court. The author suggests that the first figure on the right of the frieze, related to the group of armed men looking towards the banqueters feasting in the center of the frieze, can be read as the dead himself, for the particular rendering of his ανδρείκελον, showing the typical ochròtes or necròdes face color, according to the contemporary medical lexicon. The pathetic stance assumed by the same figure, the sole in the group which is not bearing arms, seems to confirm his role in the context of the scene
Generation of broadband circularly polarized deep-ultraviolet pulses in hollow capillary fibers
No full textWe demonstrate an efficient scheme for the generation of broadband, high-energy, circularly polarized femtosecond laser pulses in the deep ultraviolet through seeded degenerate four-wave mixing in stretched gas-filled hollow capillary fibers. Pumping and seeding with circularly polarized 35 fs pulses centered at 400 nm and 800 nm, respectively, we generate idler pulses centered at 266 nm with 27 µJ of energy and over 95% spectrally averaged ellipticity. Even higher idler energies and broad spectra (27 nm bandwidth) can be obtained at the cost of reduced ellipticity. Our system can be scaled in average power and used in different spectral regions, including the vacuum ultraviolet.</p
Strong and weak seeded four-wave mixing in stretched gas-filled hollow capillary fibers
No full textWe report a remarkably efficient experimental scheme for the generation of high energy ultra-short pulses by means of four-wave mixing in long stretched hollow capillary fibers filled with helium. We thoroughly investigate the role of strong and weak seeding fields in a degenerate up-conversion scheme to the deep ultraviolet. In the weak seed regime we demonstrate the tunable emission of up to 30 μJ in ultrashort pulses (~8 fs) in the 250-300 nm range, corresponding to pump energy conversion of up to 30%, from pump pulses with energies readily available from high-average power lasers. In the strong seed regime, we obtain higher pump conversion efficiencies, up to 42%, together with a spectral bandwidth supporting few femtosecond pulses and a record high deep-ultraviolet pulse energy exceeding 70 μJ. The energy can be further scaled by using stretched hollow-core fibers with larger core diameters
- …
