@phdthesis{Balzer2018,
  author    = {Balzer, Christian},
  title     = {Adsorption-Induced Deformation of Nanoporous Materials — in-situ Dilatometry and Modeling},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-157145},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2018},
  abstract  = {The goal of this work is to improve the understanding of adsorption-induced deformation in nanoporous (and in particular microporous) materials in order to explore its potential for material characterization and provide guidelines for related technical applications such as adsorption-driven actuation. For this purpose this work combines in-situ dilatometry measurements with in-depth modeling of the obtained adsorption-induced strains. A major advantage with respect to previous studies is the combination of the dilatometric setup and a commercial sorption instrument resulting in high quality adsorption and strain isotherms. The considered model materials are (activated and thermally annealed) carbon xerogels, a sintered silica aerogel, a sintered hierarchical structured porous silica and binderless zeolites of type LTA and FAU; this selection covers micro-, meso- and macroporous as well as ordered and disordered model materials. All sample materials were characterized by scanning electron microscopy, gas adsorption and sound velocity measurements. In-situ dilatometry measurements on mesoporous model materials were performed for the adsorption of N2 at 77 K, while microporous model materials were also investigated for CO2 adsorption at 273 K, Ar adsorption at 77 K and H2O adsorption at 298 K. Within this work the available in-situ dilatometry setup was revised to improve resolution and reproducibility of measurements of small strains at low relative pressures, which are of particular relevance for microporous materials. The obtained experimental adsorption and strain isotherms of the hierarchical structured porous silica and a micro-macroporous carbon xerogel were quantitatively analyzed based on the adsorption stress model; this approach, originally proposed by Ravikovitch and Neimark, was extended for anisotropic pore geometries within this work. While the adsorption in silica mesopores could be well described by the classical and analytical theory of Derjaguin, Broekhoff and de Boer, the adsorption in carbon micropores required for comprehensive nonlocal density functional theory calculations. To connect adsorption-induced stresses and strains, furthermore mechanical models for the respective model materials were derived. The resulting theoretical framework of adsorption, adsorption stress and mechanical model was applied to the experimental data yielding structural and mechanical information about the model materials investigated, i.e., pore size or pore size distribution, respectively, and mechanical moduli of the porous matrix and the nonporous solid skeleton. The derived structural and mechanical properties of the model materials were found to be consistent with independent measurements and/or literature values. Noteworthy, the proposed extension of the adsorption stress model proved to be crucial for the correct description of the experimental data. Furthermore, it could be shown that the adsorption-induced deformation of disordered mesoporous aero-/xerogel structures follows qualitatively the same mechanisms obtained for the ordered hierarchical structured porous silica. However, respective quantitative modeling proved to be challenging due to the ill-shaped pore geometry of aero-/xerogels; good agreement between model and experiment could only be achieved for the filled pore regime of the adsorption isotherm and the relative pressure range of monolayer formation. In the intermediate regime of multilayer formation a more complex model than the one proposed here is required to correctly describe stress related to the curved adsorbate-adsorptive interface. Notably, for micro-mesoporous carbon xerogels it could be shown that micro- and mesopore related strain mechanisms superimpose one another. The strain isotherms of the zeolites were only qualitatively evaluated. The result for the FAU type zeolite is in good agreement with other experiments reported in literature and the theoretical understanding derived from the adsorption stress model. On the contrary, the strain isotherm of the LTA type zeolite is rather exceptional as it shows monotonic expansion over the whole relative pressure range. Qualitatively this type of strain isotherm can also be explained by the adsorption stress model, but a respective quantitative analysis is beyond the scope of this work. In summary, the analysis of the model materials' adsorption-induced strains proved to be a suitable tool to obtain information on their structural and mechanical properties including the stiffness of the nonporous solid skeleton. Investigations on the carbon xerogels modified by activation and thermal annealing revealed that adsorption-induced deformation is particularly suited to analyze even small changes of carbon micropore structures.},
  subject      = {Nanopor{\"o}ser Stoff},
  language  = {en}
}
@article{LiuHuNiemannetal.2013,
  author    = {Liu, Dan and Hu, Kai and Niemann, Markus and Herrmann, Sebastian and Cikes, Maja and St{\"o}rk, Stefan and Beer, Meinrad and Gaudron, Philipp Daniel and Morbach, Caroline and Knop, Stefan and Geissinger, Eva and Ertl, Georg and Bijnens, Bart and Weidemann, Frank},
  title     = {Impact of Regional Left Ventricular Function on Outcome for Patients with AL Amyloidosis},
  series = {PLoS ONE},
  volume    = {8},
  journal   = {PLoS ONE},
  number    = {3},
  doi       = {10.1371/journal.pone.0056923},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-130293},
  pages     = {e56923},
  year      = {2013},
  abstract  = {Objectives The aim of this study was to explore the left ventricular (LV) deformation changes and the potential impact of deformation on outcome in patients with proven light-chain (AL) amyloidosis and LV hypertrophy. Background Cardiac involvement in AL amyloidosis patients is associated with poor outcome. Detecting regional cardiac function by advanced non-invasive techniques might be favorable for predicting outcome. Methods LV longitudinal, circumferential and radial peak systolic strains (Ssys) were assessed by speckle tracking imaging (STI) in 44 biopsy-proven systemic AL amyloidosis patients with LV hypertrophy (CA) and in 30 normal controls. Patients were divided into compensated (n = 18) and decompensated (n = 26) group based on clinical assessment and followed-up for a median period of 345 days. Results Ejection fraction (EF) was preserved while longitudinal Ssys (LSsys) was significantly reduced in both compensated and decompensated groups. Survival was significantly reduced in decompensated group (35\% vs. compensated 78\%, P = 0.001). LSsys were similar in apical segments and significantly reduced in basal segments between two patient groups. LSsys at mid-segments were significantly reduced in all LV walls of decompensated group. Patients were further divided into 4 subgroups according to the presence or absence of reduced LSsys in no (normal), only basal (mild), basal and mid (intermediate) and all segments of the septum (severe). This staging revealed continuously worse prognosis in proportion to increasing number of segments with reduced LSsys (mortality: normal 14\%, mild 27\%, intermediate 67\%, and severe 64\%). Mid-septum LSsys<11\% suggested a 4.8-fold mortality risk than mid-septum LSsys≥11\%. Multivariate regression analysis showed NYHA class and mid-septum LSsys were independent predictors for survival. Conclusions Reduced deformation at mid-septum is associated with worse prognosis in systemic amyloidosis patients with LV hypertrophy.},
  language  = {en}
}
@article{LiuHuStoerketal.2014,
  author    = {Liu, Dan and Hu, Kai and St{\"o}rk, Stefan and Herrmann, Sebastian and Kramer, Bastian and Cikes, Maja and Gaudron, Philipp Daniel and Knop, Stefan and Ertl, Georg and Bijnens, Bart and Weidemann, Frank},
  title     = {Predictive Value of Assessing Diastolic Strain Rate on Survival in Cardiac Amyloidosis Patients with Preserved Ejection Fraction},
  series = {PLOS ONE},
  volume    = {9},
  journal   = {PLOS ONE},
  number    = {12},
  issn      = {1932-6203},
  doi       = {10.1371/journal.pone.0115910},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-118024},
  year      = {2014},
  abstract  = {Objectives: Since diastolic abnormalities are typical findings of cardiac amyloidosis (CA), we hypothesized that speckle-tracking-imaging (STI) derived longitudinal early diastolic strain rate (LSRdias) could predict outcome in CA patients with preserved left ventricular ejection fraction (LVEF >50\%). Background: Diastolic abnormalities including altered early filling are typical findings and are related to outcome in CA patients. Reduced longitudinal systolic strain (LSsys) assessed by STI predicts increased mortality in CA patients. It remains unknown if LSRdias also related to outcome in these patients. Methods: Conventional echocardiography and STI were performed in 41 CA patients with preserved LVEF (25 male; mean age 65±9 years). Global and segmental LSsys and LSRdias were obtained in six LV segments from apical 4-chamber views. Results: Nineteen (46\%) out of 41 CA patients died during a median of 16 months (quartiles 5-35 months) follow-up. Baseline mitral annular plane systolic excursion (MAPSE, 6±2 vs. 8±3 mm), global LSRdias and basal-septal LSRdias were significantly lower in non-survivors than in survivors (all p<0.05). NYHA class, number of non-cardiac organs involved, MAPSE, mid-septal LSsys, global LSRdias, basal-septal LSRdias and E/LSRdias were the univariable predictors of all-cause death. Multivariable analysis showed that number of non-cardiac organs involved (hazard ratio [HR] = 1.96, 95\% confidence interval [CI] 1.17-3.26, P = 0.010), global LSRdias (HR = 7.30, 95\% CI 2.08-25.65, P = 0.002), and E/LSRdias (HR = 2.98, 95\% CI 1.54-5.79, P = 0.001) remained independently predictive of increased mortality risk. The prognostic performance of global LSRdias was optimal at a cutoff value of 0.85 S-1 (sensitivity 68\%, specificity 67\%). Global LSRdias <0.85 S-1 predicted a 4-fold increased mortality in CA patients with preserved LVEF. Conclusions: STI-derived early diastolic strain rate is a powerful independent predictor of survival in CA patients with preserved LVEF.},
  language  = {en}
}