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7. Coherent X-ray Scattering Reveals Nanoscale Fluctuations in Hydrated Proteins

Author

Bin, Maddalena, Reiser, Mario, Filianina, Mariia, Berkowicz, Sharon, Das, Sudipta, Timmermann, Sonja, Roseker, Wojciech, Bauer, Robert, Öström, Jonatan, Karina, Aigerim, Amann-Winkel, Katrin, Ladd-Parada, Marjorie, Westermeier, Fabian, Sprung, Michael, Möller, Johannes, Lehmkühler, Felix, Gutt, Christian, and Perakis, Fivos

Subjects
Condensed Matter - Soft Condensed Matter, Physics - Biological Physics, Physics - Chemical Physics
Abstract

Hydrated proteins undergo a transition in the deeply supercooled regime, which is attributed to rapid changes in hydration water and protein structural dynamics. Here, we investigate the nanoscale stress relaxation in hydrated lysozyme proteins stimulated and probed by X-ray Photon Correlation Spectroscopy (XPCS). This approach allows us to access the nanoscale dynamic response in the deeply supercooled regime (T = 180 K) which is typically not accessible through equilibrium methods. The relaxation time constants exhibit Arrhenius temperature dependence upon cooling with a minimum in the Kohlrausch-Williams-Watts exponent at T = 227 K. The observed minimum is attributed to an increase in dynamical heterogeneity, which coincides with enhanced fluctuations observed in the two-time correlation functions and a maximum in the dynamic susceptibility quantified by the normalised variance $\chi_T$. Our study provides new insights into X-ray stimulated stress relaxation and the underlying mechanisms behind spatio-temporal fluctuations in biological granular materials.

Published
2023
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8. The structure of ice under confinement in periodic mesoporous organosilicas (PMOs).

Author

Gießelmann, Niels C., Lenz, Philip, Meinert, Sophia-Marie, Simon, Tamás, Bauer, Robert P. C., Jo, Wonhyuk, Claas, Sarah, Köhn, Christian, Striker, Nele N., Fröba, Michael, and Lehmkühler, Felix

Subjects
ICE crystals, LATTICE constants, CROSS correlation, X-ray scattering, POROUS materials, ICE
Abstract

We investigated the structure of ice under nanoporous confinement in periodic mesoporous organosilicas (PMOs) with different organic functionalities and pore diameters between 3.4 and 4.9 nm. X-ray scattering measurements of the system were performed at temperatures between 290 and 150 K. We report the emergence of ice I with both hexagonal and cubic characteristics in different porous materials, as well as an alteration of the lattice parameters when compared to bulk ice. This effect is dependent on the pore diameter and the surface chemistry of the respective PMO. Investigations regarding the orientation of hexagonal ice crystals relative to the pore wall using x-ray cross correlation analysis reveal one or more discrete preferred orientation in most of the samples. For a pore diameter of around 3.8 nm, stronger correlation peaks are present in more hydrophilically functionalized pores and seem to be connected to stronger shifts in the lattice parameters. [ABSTRACT FROM AUTHOR]

Published
2024
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11. An Optimization-based Approach for Flow Table Capacity Bottleneck Mitigation in Software-Defined Networks

Author

Bauer, Robert and Zitterbart, Martina

Subjects
Computer Science - Networking and Internet Architecture
Abstract

Flow delegation is a flexible technique to mitigate flow table capacity bottlenecks in Software-defined Networks (SDN). Such bottlenecks occur when SDN switches provide insufficient flow table capacity which leads to performance degradation and network failures. Flow delegation addresses this problem by automatically relocating flow rules from a bottlenecked switch to neighboring switches with spare capacity. This paper introduces a new algorithm to efficiently perform flow delegation based on a novel delegation template abstraction and multi-period multi-objective optimization. Different from existing work, our approach can include estimated knowledge about future network situations and deal with different optimization criteria such as link and control overhead. We discuss the problem decomposition for the new algorithm and introduce an efficient two-step heuristic. Results show, that our approach performs significantly better than the simple greedy algorithm used in earlier work and is capable of handling flow delegation for networks with hundreds of switches., Comment: 14 pages, 9 figures

Published
2021

20. Derivation of a homogenized bending--torsion theory for rods with micro-heterogeneous prestrain

Author

Bauer, Robert, Neukamm, Stefan, and Schäffner, Mathias

Subjects
Mathematics - Analysis of PDEs, 74B20, 74K10, 35B27, 74Q05
Abstract

In this paper we investigate rods made of nonlinearly elastic, composite--materials that feature a micro-heterogeneous prestrain that oscillates (locally periodic) on a scale that is small compared to the length of the rod. As a main result we derive a homogenized bending-torsion theory for rods as $\Gamma$-limit from 3D nonlinear elasticity by simultaneous homogenization and dimension reduction under the assumption that the prestrain is of the order of the diameter of the rod. The limit model features a spontaneous curvature-torsion tensor that captures the macroscopic effect of the micro-heterogeneous prestrain. We device a formula that allows to compute the spontaneous curvature-torsion tensor by means of a weighted average of the given prestrain. The weight in the average depends on the geometry of the composite and invokes correctors that are defined with help of boundary value problems for the system of linear elasticity. The definition of the correctors depends on a relative scaling parameter $\gamma$, which monitors the ratio between the diameter of the rod and the period of the composite's microstructure. We observe an interesting size-effect: For the same prestrain a transition from flat minimizers to curved minimizers occurs by just changing the value of $\gamma$. Moreover, in the paper we analytically investigate the microstructure-properties relation in the case of isotropic, layered composites, and consider applications to nematic liquid-crystal-elastomer rods and shape programming., Comment: Minor changes in introduction and bibliographiy. Pictures added

Published
2019

39. Improved Power for Characterizing Longitudinal Amyloid-β PET Changes and Evaluating Amyloid-Modifying Treatments with a Cerebral White Matter Reference Region

Author

Chen, Kewei, Roontiva, Auttawut, Thiyyagura, Pradeep, Lee, Wendy, Liu, Xiaofen, Ayutyanont, Napatkamon, Protas, Hillary, Luo, Ji Luo, Bauer, Robert, Reschke, Cole, Bandy, Daniel, Koeppe, Robert A, Fleisher, Adam S, Caselli, Richard J, Landau, Susan, Jagust, William J, Weiner, Michael W, and Reiman, Eric M

Subjects
Biomedical and Clinical Sciences, Clinical Sciences, Neurodegenerative, Alzheimer's Disease, Dementia, Neurosciences, Brain Disorders, Alzheimer's Disease including Alzheimer's Disease Related Dementias (AD/ADRD), Clinical Research, Biomedical Imaging, Acquired Cognitive Impairment, Aging, Neurological, Aged, Aged, 80 and over, Alzheimer Disease, Amyloid beta-Peptides, Aniline Compounds, Apolipoprotein E4, Brain, Brain Mapping, Cerebellum, Cerebrum, Cognition Disorders, Ethylene Glycols, Female, Humans, Image Processing, Computer-Assisted, Longitudinal Studies, Male, Middle Aged, Pons, Positron-Emission Tomography, Randomized Controlled Trials as Topic, Reference Values, Sample Size, Time Factors, White Matter, Alzheimer disease, florbetapir PET, biomarkers, image analysis, statistical power, clinical trial sample size, Alzheimer’s Disease Neuroimaging Initiative, Nuclear Medicine & Medical Imaging, Clinical sciences
Abstract

UnlabelledIn this article, we describe an image analysis strategy with improved power for tracking longitudinal amyloid-β (Aβ) PET changes and evaluating Aβ-modifying treatments.MethodsOur aims were to compare the power of template-based cerebellar, pontine, and cerebral white matter reference regions to track 24-mo florbetapir standardized uptake value (SUV) ratio (SUVR) changes; to relate those changes to 24-mo clinical declines; and to evaluate Aβ-modifying treatments in Aβ-positive (Aβ+) and Aβ-negative (Aβ-) patients with probable Alzheimer dementia (pAD), in patients with mild cognitive impairment (MCI), in cognitively normal controls (NCs), and in cognitively normal apolipoprotein E4 (APOE4) carriers and noncarriers. We used baseline and follow-up (∼24 mo) florbetapir PET scans from 332 Aβ+ and Aβ- subjects participating in the multicenter Alzheimer's Disease Neuroimaging Initiative. Each of the proposed analyses included 31 pAD patients, 187 MCI patients, and 114 NCs. Cerebral-to-white matter, cerebellar, and pontine SUVRs were characterized in terms of their longitudinal variability; their power to track longitudinal fibrillar Aβ increases in Aβ+ and Aβ- subgroups and cognitively normal APOE4 carriers and noncarriers; the sample sizes needed to detect attenuated accumulation of or clearance of fibrillar Aβ accumulation in randomized clinical trials; and their ability to relate 24-mo fibrillar Aβ increases to clinical declines.ResultsAs predicted, cerebral-to-white matter SUVR changes were significantly less variable and had significantly greater power to detect 24-mo fibrillar Aβ increases and evaluate Aβ-modifying treatment effects in Aβ+ pAD, MCI, and NC subjects and cognitively normal APOE4 carriers. They were also distinguished by the ability to detect significant associations between 24-mo Aβ increases and clinical declines.ConclusionA cerebral white matter reference region may improve the power to track longitudinal fibrillar Aβ increases, to characterize their relationship to longitudinal clinical declines, and to evaluate Aβ-modifying treatments in randomized clinical trials.

Published
2015

42. Genetic and Epigenetic Fine Mapping of Complex Trait Associated Loci in the Human Liver

Author

Çalışkan, Minal, Manduchi, Elisabetta, Rao, H. Shanker, Segert, Julian A., Beltrame, Marcia Holsbach, Trizzino, Marco, Park, YoSon, Baker, Samuel W., Chesi, Alessandra, Johnson, Matthew E., Hodge, Kenyaita M., Leonard, Michelle E., Loza, Baoli, Xin, Dong, Berrido, Andrea M., Hand, Nicholas J., Bauer, Robert C., Wells, Andrew D., Olthoff, Kim M., Shaked, Abraham, Rader, Daniel J., Grant, Struan F.A., and Brown, Christopher D.

Published
2019
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44. Brain imaging measurements of fibrillar amyloid-β burden, paired helical filament tau burden, and atrophy in cognitively unimpaired persons with two, one, and no copies of the APOE ε4 allele

Author

Ghisays, Valentina, Goradia, Dhruman D., Protas, Hillary, Bauer, Robert J., III, Devadas, Vivek, Tariot, Pierre N., Lowe, Val J., Knopman, David S., Petersen, Ronald C., Jack, Clifford R., Jr., Caselli, Richard J., Su, Yi, Chen, Kewei, and Reiman, Eric M.

Published
2019
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45. Khintchine-Pollaczek formula for random walks whose steps have one geometric tail

Author

Bauer, Robert O.

Subjects
Mathematics - Probability, 60B05, 28C20
Abstract

We derive a Khinchine-Pollaczek formula for random walks whose steps have a geometric left tail. The construction rests on the memory-less property of the geometric distribution. An example from a tandem queue modeling dynamic instability in microtubules is given.

Published
2011

46. A simple construction of Werner measure from chordal SLE$_{8/3}$

Author

Bauer, Robert O.

Subjects
Mathematics - Probability, Mathematics - Complex Variables, 60B05, 28C20
Abstract

We give a direct construction of the conformally invariant measure on self-avoiding loops in Riemann surfaces (Werner measure) from chordal $\text{SLE}_{8/3}$. We give a new proof of uniqueness of the measure and use Schramm's formula to construct a measure on boundary bubbles encircling an interior point. After establishing covariance properties for this bubble measure, we apply these properties to obtain a measure on loops by integrating measures on boundary bubbles. We calculate the distribution of the conformal radius of boundary bubbles encircling an interior point and deduce from it explicit upper and lower bounds for the loop measure.

Published
2009

47. Einfluss des Füllstoffgehaltes auf 3-D-gedruckte provisorische Restaurationsmaterialien.

Author

BAUER, ROBERT, ZACHER, JULIAN, STRASSER, THOMAS, SCHMID, ALOIS, and ROSENTRITT, MARTIN

Subjects
FILLER materials, SURVIVAL rate
Abstract

Copyright of Quintessenz der Zahntechnik is the property of Quintessenz Verlags GmbH and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Published
2024

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