TY  - JOUR
A1  - Kotliar, Konstantin
A1  - Nagel, Edgar
A1  - Vilser, Walthard
A1  - Seidova, Seid-Fatima
A1  - Lanzl, Ines
T1  - Microstructural alterations of retinal arterial blood column along the vessel axis in systemic hypertension
JF  - Investigative Ophthalmology & Visual Science, IOVS
N2  - Purpose: Image analysis by the retinal vessel analyzer (RVA) observes retinal vessels in their dynamic state online noninvasively along a chosen vessel segment. It has been found that high-frequency diameter changes in the retinal artery blood column along the vessel increase significantly in anamnestically healthy volunteers with increasing age and in patients with glaucoma during vascular dilation. This study was undertaken to investigate whether longitudinal sections of the retinal artery blood column are altered in systemic hypertension.

Methods: Retinal arteries of 15 untreated patients with essential arterial hypertension (age, 50.9 ± 11.9 years) and of 15 age-matched anamnestically healthy volunteers were examined by RVA. After baseline assessment, a monochromatic luminance flicker (530–600 nm; 12.5 Hz; 20 s) was applied to evoke retinal vasodilation. Differences in amplitude and frequency of spatial artery blood column diameter change along segments (longitudinal arterial profiles) of 1 mm in length were measured and analyzed using Fourier transformation.

Results: In the control group, average reduced power spectra (ARPS) of longitudinal arterial profiles did not differ when arteries changed from constriction to dilation. In the systemic hypertension group, ARPS during constriction, baseline, and restoration were identical and differed from ARPS during dilation (P < 0.05). Longitudinal arterial profiles in both groups showed significant dissimilitude at baseline and restoration (P < 0.05).

Conclusions: The retinal artery blood column demonstrates microstructural alterations in systemic hypertension and is less irregular along the vessel axis during vessel dilation. These microstructural changes may be an indication of alterations in vessel wall rigidity, vascular endothelial function, and smooth muscle cells in this disease, leading to impaired perfusion and regulation.
Y1  - 2010
U6  - http://dx.doi.org/10.1167/iovs.09-3649
SN  - 0146-0404
VL  - 51
IS  - 4
SP  - 2165
EP  - 2172
PB  - ARVO
CY  - Rockville, Md.
ER  - 
TY  - JOUR
A1  - Steinseifer, Ulrich
A1  - Kashefi, Ali
A1  - Hormes, Marcus
A1  - Schoberer, Mark
A1  - Orlikowsky, Thorsten
A1  - Behbahani, Mehdi
A1  - Behr, Marek
A1  - Schmitz-Rode, Thomas
T1  - Miniaturization of ECMO Systems : Engineering Challenges and Methods
JF  - Artificial Organs. 33 (2009), H. 5
Y1  - 2009
SN  - 1525-1594
N1  - Fifth International Conference on Pediatric Mechanical Circulatory Support Systems and Pediatric Cardiopulmonary Perfusion Abstracts <May 28, 2009>
SP  - A55
EP  - A55
ER  - 
TY  - JOUR
A1  - Dachwald, Bernd
T1  - Minimum Transfer Times for Nonperfectly Reflecting Solar Sailcraft
JF  - Journal of Spacecraft and Rockets. 41 (2004), H. 4
Y1  - 2004
SN  - 0022-4650
N1  - 2. ISSN: 1533-6794
SP  - 693
EP  - 695
ER  - 
TY  - JOUR
A1  - Dachwald, Bernd
A1  - Wurm, Patrick
T1  - Mission analysis and performance comparison for an Advanced Solar Photon Thruster
JF  - Advances in Space Research
Y1  - 2011
SN  - 0273-1177
VL  - 48
IS  - 11
SP  - 1858
EP  - 1868
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - CHAP
A1  - Dachwald, Bernd
A1  - Wurm, P.
T1  - Mission analysis for an advanced solar photon thruster
T2  - 60th International Astronautical Congress 2009, IAC 2009
N2  - The so-called "compound solar sail", also known as "Solar Photon Thruster" (SPT), is a solar sail design concept, for which the two basic functions of the solar sail, namely light collection and thrust direction, are uncoupled. In this paper, we introduce a novel SPT concept, termed the Advanced Solar Photon Thruster (ASPT). This model does not suffer from the simplified assumptions that have been made for the analysis of compound solar sails in previous studies. We present the equations that describe the force, which acts on the ASPT. After a detailed design analysis, the performance of the ASPT with respect to the conventional flat solar sail (FSS) is investigated for three interplanetary mission scenarios: An Earth-Venus rendezvous, where the solar sail has to spiral towards the Sun, an Earth-Mars rendezvous, where the solar sail has to spiral away from the Sun, and an Earth-NEA rendezvous (to near-Earth asteroid 1996FG3), where a large orbital eccentricity change is required. The investigated solar sails have realistic near-term characteristic accelerations between 0.1 and 0.2mm/s2. Our results show that a SPT is not superior to the flat solar sail unless very idealistic assumptions are made.
KW  - Interplanetary flight
Y1  - 2009
SN  - 978-161567908-9
N1  - 60th International Astronautical Congress 2009, IAC 2009; Daejeon; South Korea; 12 October 2009 through 16 October 2009
VL  - Vol. 8
SP  - 6838
EP  - 6851
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Maiwald, Volker
A1  - Dachwald, Bernd
T1  - Mission Design for a Multiple-Rendezvous Mission to Jupiter's Trojans
Y1  - 2010
N1  - COSPAR 2010 ; 38th COSPAR Scientific Assembly. Held 18-25 July 2010 in Bremen, Germany [Abstract]
SP  - 3
ER  - 
TY  - CHAP
A1  - Borggräfe, Andreas
A1  - Dachwald, Bernd
T1  - Mission performance evaluation for solar sails using a refined SRP force model with variable optical coefficients
T2  - 2nd International Symposium on Solar Sailing
N2  - Solar sails provide ignificant advantages over other low-thrust propulsion systems because they produce thrust by the momentum exchange from solar radiation pressure (SRP) and thus do not consume any propellant.The force exerted on a very thin sail foil basically depends on the light incidence angle. Several analytical SRP force models that describe the SRP force acting on the sail have been established since the 1970s. All the widely used models use constant optical force coefficients of the reflecting sail material. In 2006,MENGALI et al. proposed a refined SRP force model that takes into account the dependancy of the force coefficients on the light incident angle,the sail’s distance from the sun (and thus the sail emperature) and the surface roughness of the sail material [1]. In this paper, the refined SRP force model is compared to the previous ones in order to identify the potential impact of the new model on the predicted capabilities of solar sails in performing low-cost interplanetary space missions. All force models have been implemented within InTrance, a global low-thrust trajectory optimization software utilizing evolutionary neurocontrol [2]. Two interplanetary rendezvous missions, to Mercury and the near-Earth asteroid 1996FG3, are investigated. Two solar sail performances in terms of characteristic acceleration are examined for both scenarios, 0.2 mm/s2 and 0.5 mm/s2, termed “low” and “medium” sail performance. In case of the refined SRP model, three different values of surface roughness are chosen, h = 0 nm, 10 nm and 25 nm. The results show that the refined SRP force model yields shorter transfer times than the standard model.
Y1  - 2010
N1  - 2nd International Symposium on Solar Sailing, ISSS 2010, 2010-07-20 - 2010-07-22. New York City College of Technology of the City University of New York, USA
SP  - 1
EP  - 6
ER  - 
TY  - CHAP
A1  - Carzana, Livio
A1  - Dachwald, Bernd
A1  - Noomen, Ron
T1  - Model and trajectory optimization for an ideal laser-enhanced solar sail
T2  - 68th International Astronautical Congress
N2  - A laser-enhanced solar sail is a solar sail that is not solely propelled by solar radiation but additionally by a laser beam that illuminates the sail. This way, the propulsive acceleration of the sail results from the combined action of the solar and the laser radiation pressure onto the sail. The potential source of the laser beam is a laser satellite that coverts solar power (in the inner solar system) or nuclear power (in the outer solar system) into laser power. Such a laser satellite (or many of them) can orbit anywhere in the solar system and its optimal orbit (or their optimal orbits) for a given mission is a subject for future research. This contribution provides the model for an ideal laser-enhanced solar sail and investigates how a laser can enhance the thrusting capability of such a sail. The term ”ideal” means that the solar sail is assumed to be perfectly reflecting and that the laser beam is assumed to have a constant areal power density over the whole sail area. Since a laser beam has a limited divergence, it can provide radiation pressure at much larger solar distances and increase the radiation pressure force into the desired direction. Therefore, laser-enhanced solar sails may make missions feasible, that would otherwise have prohibitively long flight times, e.g. rendezvous missions in the outer solar system. This contribution will also analyze exemplary mission scenarios and present optimial trajectories without laying too much emphasis on the design and operations of the laser satellites. If the mission studies conclude that laser-enhanced solar sails would have advantages with respect to ”traditional” solar sails, a detailed study of the laser satellites and the whole system architecture would be the second next step
Y1  - 2017
N1  - 68th International Astronautical Congress: Unlocking Imagination, Fostering Innovation and Strengthening Security, IAC 2017, 2017-09-25 → 2017-09-29, Adelaide, Australia
ER  - 
TY  - JOUR
A1  - Kotliar, Konstantin
A1  - Bauer, S. M.
A1  - Zamuraev, L. A.
T1  - Model of the transversely isotropic spherical layer for estimation of intraocular pressure changes after intravitreal injections / Bauer, S. M. ; Zamuraev, L. A. ; Kotliar, K. E.
JF  - Rossiiskii zhurnal biomekhaniki = Russian Journal of biomechanics. 10 (2006), H. 2
Y1  - 2006
SN  - 1812-5123
SP  - 41
EP  - 47
PB  - -
ER  - 
TY  - JOUR
A1  - Behbahani, Mehdi
A1  - Tran, L.
A1  - Waluga, C.
A1  - Behr, M.
A1  - Oedekoven, B.
A1  - Mottaghy, K.
T1  - Model-based Numerical Analysis of Platelet Adhesion, Thrombus Growth and Aggregation for Assist Devices
JF  - The International Journal of Artificial Organs. 32 (2009), H. 7
Y1  - 2009
SN  - 0391-3988
N1  - Abstracts - Oral Presentations: XXXVI Annual ESAO Congress, 2-5 September 2009, Compiègne - France; European Society of Artificial Organs (ESAO), Compiegne, France, September 2-5, 2009
SP  - 398
EP  - 398
ER  -