| 1. |
- Ihne-Schubert, Sandra Michaela, et al.
(author)
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Single German centre experience with patient journey and care-relevant needs in amyloidosis : The German AMY-NEEDS research and care program
- 2024
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In: PLoS ONE. - 1932-6203. ; 19:5 May
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Journal article (peer-reviewed)abstract
- Background Amyloidosis is a rare multi-system disorder associated with frequently delayed diagnosis, enormous disease burden and psychosocial distress. Methods Systematic assessment of needs was performed by a subtype-spanning questionnairebased survey within the AMY-NEEDS research and care program. Results 118 patients with proven amyloidosis (62.7% ATTR, 22.0% AL, 15.3% other forms) were included in August 2020 until February 2021 (mean age 71.2 ±11.3 years; 30% women). The median diagnostic delay between onset of symptoms and diagnosis was 9.0 (range: 2.5; 33.0) months. Local health care providers (HCPs) play a central role on the way to diagnosis. Diagnosis itself typically requires a clinical but not necessarily a university setting. In the treatment phase, the focus moves to the amyloidosis centre as primary contact and coordinator, with general practitioners (GPs) acting predominantly as a contact point in crisis and link to additional services. About half of patients reported impaired quality of life and one third suffering from anxiety and depressed mood, respectively. The majority of patients talk about their concerns with close caregivers and local HCPs. Advance care planning is a relevant, yet insufficiently met need. Conclusion The journey of patients with amyloidotic disease, their contact partners and needs at different stages were characterized in detail within the German health care system. An amyloidosis- specific care concept has to master the multitude of interfaces connecting the numerous treatment providers involved with the amyloidosis centre and GPs as key players. Telemedical approaches could be a promising and well-accepted option allowing optimal coordination and communication.
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| 2. |
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| 3. |
- Darakchieva, Vanya, 1971-, et al.
(author)
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Anisotropic strain and phonon deformation potentials in GaN
- 2007
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In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 75:19, s. 195217-
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Journal article (peer-reviewed)abstract
- We report optical phonon frequency studies in anisotropically strained c -plane- and a -plane-oriented GaN films by generalized infrared spectroscopic ellipsometry and Raman scattering spectroscopy. The anisotropic strain in the films is obtained from high-resolution x-ray diffraction measurements. Experimental evidence for splitting of the GaN E1 (TO), E1 (LO), and E2 phonons under anisotropic strain in the basal plane is presented, and their phonon deformation potentials c E1 (TO), c E1 (LO), and c E2 are determined. A distinct correlation between anisotropic strain and the A1 (TO) and E1 (LO) frequencies of a -plane GaN films reveals the a A1 (TO), b A1 (TO), a E1 (LO), and b E1 (LO) phonon deformation potentials. The a A1 (TO) and b A1 (TO) are found to be in very good agreement with previous results from Raman experiments. Our a A1 (TO) and a E1 (LO) phonon deformation potentials agree well with recently reported theoretical estimations, while b A1 (TO) and b E1 (LO) are found to be significantly larger than the theoretical values. A discussion of the observed differences is presented. © 2007 The American Physical Society.
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| 4. |
- Darakchieva, Vanya, et al.
(author)
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Assessment of phonon mode characteristics via infrared spectroscopic ellipsometry on a-plane GaN
- 2006
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In: Physica status solidi. B, Basic research. - : Wiley. - 0370-1972 .- 1521-3951. ; 243:7, s. 1594-1598
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Journal article (peer-reviewed)abstract
- Generalized infrared spectroscopic ellipsometry was applied to study the vibrational properties of anisotropically strained a-plane GaN films with different thicknesses. We have established a correlation between the phonon mode parameters and the strain, which allows the determination of the deformation potentials and strain-free frequency of the GaN A,(TO) mode. These results are compared with previous theoretical and experimental findings and discussed.
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| 5. |
- Darakchieva, Vanya, 1971-, et al.
(author)
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Deformation potentials of the E1 (TO) and E2 modes of InN
- 2004
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 84:18, s. 3636-3638
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Journal article (peer-reviewed)abstract
- The determination of deformation potentials of E1(TO) and E 2 modes of InN were discussed. The deformation potentials were evaluated for two sets of stiffness constants using x-ray diffraction, IR spectroscopic ellipsometry (IRSE), Raman scattering, and Grüneisen parameter values. The InN layer were grown on GaN buffer layers on (0001) sapphire by molecular beam epitaxy. It was found that the strain-free values of the InN E1(TO) mode was 477.9 cm-1 and 491.9 cm -1 for the E2 modes.
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| 6. |
- Darakchieva, Vanya, et al.
(author)
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Generalized infrared ellipsometry study of thin epitaxial AlN layers with complex strain behavior
- 2003
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Conference paper (peer-reviewed)abstract
- The effect of film thickness on the strain and structural properties of thin epitaxial AlN films has been investigated, and a sub-layer model of the degree of strain and related defects for all films is suggested. The vibrational properties of the films have been studied by generalized infrared spectroscopic ellipsometry. The proposed sub-layer model has been successfully applied to the analysis of the ellipsometry data trough model calculations of the infrared dielectric function. © 2003 Elsevier B.V. All rights reserved.
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| 7. |
- Darakchieva, Vanya, et al.
(author)
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Infrared ellipsometry and Raman studies of hexagonal InN films : Correlation between strain and vibrational properties
- 2004
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In: Superlattices and Microstructures. - : Elsevier BV. - 0749-6036 .- 1096-3677. ; 36:4-6, s. 573-580
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Journal article (peer-reviewed)abstract
- The vibrational properties of InN films with different strain have been studied using Infrared ellipsometry and Raman scattering spectroscopy. We have established a correlation between the phonon mode parameters and the strain, which allows the determination of the deformation potentials and the strain-free frequencies of the InN E1(TO) and E2 modes. The LO phonons and their coupling to the free-carrier plasmon excitations are also discussed in relation to the carrier concentration in the films. © 2004 Elsevier Ltd. All rights reserved.
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| 8. |
- Darakchieva, Vanya, 1971-, et al.
(author)
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Optical phonons in a-plane GaN under anisotropic strain
- 2008. - 1
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In: Group-III nitrides with nonpolar surfaces: growth, properties and devices. - : Wiley. - 9783527407682 ; , s. 219-253
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Book chapter (other academic/artistic)abstract
- This is the first monograph to discuss in detail the current stage of development of nonpolar nitrides, with specific emphasis on the three main topics of crystal growth, properties and device studies. World–class researchers summarize their own recent achievements in their respective fields of expertise, covering both nonpolar and semipolar nitride materials. The bulk of the discussion in each chapter is related to the physical properties of the material obtained by the respective technique, in particular, defect density and properties of the defects in nonpolar nitrides. In addiiton, the optical and vibrational properties are also addressed in several chapters, as is progress in heterostructures, quantum wells and dots based on the AlGaN/GaN and the InGaN/GaN systems. Finally, an outlook of the application areas of the differently grown materials is presented in most chapters, together with the capabilities and limitations of the respective growth approaches used.
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| 9. |
- Darakchieva, Vanya, 1971-, et al.
(author)
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Phonon mode behavior in strained wurtzite AlN/GaN superlattices
- 2005
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In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 71:11, s. 115329-
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Journal article (peer-reviewed)abstract
- We have studied phonons in AlN/GaN superlattices with different periods but a constant well-to-barrier ratio using a combination of infrared spectroscopic ellipsometry and Raman scattering spectroscopy. The strain evolution in the superlattice structures is assessed by high-resolution x-ray diffraction and reciprocal space mapping. We have identified E1(TO), A 1(LO) and E2 localized, and E1(LO) and A 1(TO) delocalized superlattice modes. The dependencies of their frequencies on in-plane strain are analyzed and discussed, and the strain-free frequencies of the superlattice modes are estimated. A good agreement between theory and experiment is found in the case of GaN localized modes, while large deviations between theoretically estimated and experimentally determined frequency shifts are observed for the AlN localized modes. The delocalization effect on the A1(TO) and E1(LO) phonons, as well as the free-carrier effect on the E1(LO) phonon are also discussed. ©2005 The American Physical Society.
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| 10. |
- Darakchieva, Vanya, et al.
(author)
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Residual strain in HVPE GaN free-standing and re-grown homoepitaxial layers
- 2003
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In: Physica status solidi. A, Applied research. - : Wiley. - 0031-8965 .- 1521-396X. ; 195:3, s. 516-522
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Journal article (peer-reviewed)abstract
- The lattice parameters of as-grown hydride vapor phase epitaxy GaN layers on sapphire, free-standing layers after the substrate lift-off, and homoepitaxial layers grown on the free-standing layers are measured. The in-plane and out-of-plane strains are calculated. It is found that the substrate removal leads to strain relaxation in the crack-free GaN free-standing layers to a certain extent. A small increase of the strain in the GaN homoepitaxial layers compared to the free-standing layers is observed. Cathodoluminescence (CL) spectroscopy and imaging, photoluminescence (PL) and Raman measurements are used as complementary tools in the residual strain analysis.
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