TY  - JOUR
A1  - Haeger, Gerrit
A1  - Bongaerts, Johannes
A1  - Siegert, Petra
T1  - A convenient ninhydrin assay in 96-well format for amino acid-releasing enzymes using an air-stable reagent
JF  - Analytical Biochemistry
N2  - An improved and convenient ninhydrin assay for aminoacylase activity measurements was developed using the commercial EZ Nin™ reagent. Alternative reagents from literature were also evaluated and compared. The addition of DMSO to the reagent enhanced the solubility of Ruhemann's purple (RP). Furthermore, we found that the use of a basic, aqueous buffer enhances stability of RP. An acidic protocol for the quantification of lysine was developed by addition of glacial acetic acid. The assay allows for parallel processing in a 96-well format with measurements microtiter plates.
Y1  - 2022
U6  - http://dx.doi.org/10.1016/j.ab.2022.114819
SN  - 1096-0309
IS  - 624
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Topçu, Murat
A1  - Madabhushi, Gopal S.P.
A1  - Staat, Manfred
T1  - A generalized shear-lag theory for elastic stress transfer between matrix and fibres having a variable radius
JF  - International Journal of Solids and Structures
N2  - A generalized shear-lag theory for fibres with variable radius is developed to analyse elastic fibre/matrix stress transfer. The theory accounts for the reinforcement of biological composites, such as soft tissue and bone tissue, as well as for the reinforcement of technical composite materials, such as fibre-reinforced polymers (FRP). The original shear-lag theory proposed by Cox in 1952 is generalized for fibres with variable radius and with symmetric and asymmetric ends. Analytical solutions are derived for the distribution of axial and interfacial shear stress in cylindrical and elliptical fibres, as well as conical and paraboloidal fibres with asymmetric ends. Additionally, the distribution of axial and interfacial shear stress for conical and paraboloidal fibres with symmetric ends are numerically predicted. The results are compared with solutions from axisymmetric finite element models. A parameter study is performed, to investigate the suitability of alternative fibre geometries for use in FRP.
KW  - Natural fibres
KW  - Polymer-matrix composites
KW  - Biocomposites
KW  - Stress concentrations
KW  - Finite element analysis
Y1  - 2022
U6  - http://dx.doi.org/10.1016/j.ijsolstr.2022.111464
SN  - 0020-7683
VL  - 239–240
IS  - Art. No. 111464
PB  - Elsevier
CY  - New York, NY
ER  - 
TY  - JOUR
A1  - Baringhaus, Ludwig
A1  - Gaigall, Daniel
T1  - A goodness-of-fit test for the compound Poisson exponential model
JF  - Journal of Multivariate Analysis
N2  - On the basis of bivariate data, assumed to be observations of independent copies of a random vector (S,N), we consider testing the hypothesis that the distribution of (S,N) belongs to the parametric class of distributions that arise with the compound Poisson exponential model. Typically, this model is used in stochastic hydrology, with N as the number of raindays, and S as total rainfall amount during a certain time period, or in actuarial science, with N as the number of losses, and S as total loss expenditure during a certain time period. The compound Poisson exponential model is characterized in the way that a specific transform associated with the distribution of (S,N) satisfies a certain differential equation. Mimicking the function part of this equation by substituting the empirical counterparts of the transform we obtain an expression the weighted integral of the square of which is used as test statistic. We deal with two variants of the latter, one of which being invariant under scale transformations of the S-part by fixed positive constants. Critical values are obtained by using a parametric bootstrap procedure. The asymptotic behavior of the tests is discussed. A simulation study demonstrates the performance of the tests in the finite sample case. The procedure is applied to rainfall data and to an actuarial dataset. A multivariate extension is also discussed.
KW  - Bootstrapping
KW  - Collective risk model
Y1  - 2022
U6  - http://dx.doi.org/10.1016/j.jmva.2022.105154
SN  - 0047-259X
SN  - 1095-7243
VL  - 195
IS  - Article 105154
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Uysal, Karya
A1  - Firat, Ipek Serat
A1  - Creutz, Till
A1  - Aydin, Inci Cansu
A1  - Artmann, Gerhard
A1  - Teusch, Nicole
A1  - Temiz Artmann, Aysegül
T1  - A novel in vitro wound healing assay using free-standing, ultra-thin PDMS membranes
JF  - membranes
N2  - Advances in polymer science have significantly increased polymer applications in life sciences. We report the use of free-standing, ultra-thin polydimethylsiloxane (PDMS) membranes, called CellDrum, as cell culture substrates for an in vitro wound model. Dermal fibroblast monolayers from 28- and 88-year-old donors were cultured on CellDrums. By using stainless steel balls, circular cell-free areas were created in the cell layer (wounding). Sinusoidal strain of 1 Hz, 5% strain, was applied to membranes for 30 min in 4 sessions. The gap circumference and closure rate of un-stretched samples (controls) and stretched samples were monitored over 4 days to investigate the effects of donor age and mechanical strain on wound closure. A significant decrease in gap circumference and an increase in gap closure rate were observed in trained samples from younger donors and control samples from older donors. In contrast, a significant decrease in gap closure rate and an increase in wound circumference were observed in the trained samples from older donors. Through these results, we propose the model of a cell monolayer on stretchable CellDrums as a practical tool for wound healing research. The combination of biomechanical cell loading in conjunction with analyses such as gene/protein expression seems promising beyond the scope published here.
Y1  - 2022
U6  - http://dx.doi.org/10.3390/membranes13010022
N1  - This article belongs to the Special Issue "Latest Scientific Discoveries in Polymer Membranes"
VL  - 2023
IS  - 13(1)
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Schwager, Christian
A1  - Flesch, Robert
A1  - Schwarzbözl, Peter
A1  - Herrmann, Ulf
A1  - Teixeira Boura, Cristiano José
T1  - Advanced two phase flow model for transient molten salt receiver system simulation
JF  - Solar Energy
N2  - In order to realistically predict and optimize the actual performance of a concentrating solar power (CSP) plant sophisticated simulation models and methods are required. This paper presents a detailed dynamic simulation model for a Molten Salt Solar Tower (MST) system, which is capable of simulating transient operation including detailed startup and shutdown procedures including drainage and refill. For appropriate representation of the transient behavior of the receiver as well as replication of local bulk and surface temperatures a discretized receiver model based on a novel homogeneous two-phase (2P) flow modelling approach is implemented in Modelica Dymola®. This allows for reasonable representation of the very different hydraulic and thermal properties of molten salt versus air as well as the transition between both. This dynamic 2P receiver model is embedded in a comprehensive one-dimensional model of a commercial scale MST system and coupled with a transient receiver flux density distribution from raytracing based heliostat field simulation. This enables for detailed process prediction with reasonable computational effort, while providing data such as local salt film and wall temperatures, realistic control behavior as well as net performance of the overall system. Besides a model description, this paper presents some results of a validation as well as the simulation of a complete startup procedure. Finally, a study on numerical simulation performance and grid dependencies is presented and discussed.
KW  - Molten salt solar tower
KW  - Molten salt receiver system
KW  - Dynamic simulation
KW  - Two-phase modelling
KW  - Transient flux distribution
Y1  - 2022
U6  - http://dx.doi.org/10.1016/j.solener.2021.12.065
SN  - 0038-092X (print)
SN  - 1471-1257 (online)
VL  - 232
SP  - 362
EP  - 375
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Zhantlessova, Sirina
A1  - Savitskaya, Irina
A1  - Kistaubayeva, Aida
A1  - Ignatova, Ludmila
A1  - Talipova, Aizhan
A1  - Pogrebnjak, Alexander
A1  - Digel, Ilya
T1  - Advanced “Green” prebiotic composite of bacterial cellulose/pullulan based on synthetic biology-powered microbial coculture strategy
JF  - Polymers
N2  - Bacterial cellulose (BC) is a biopolymer produced by different microorganisms, but in biotechnological practice, Komagataeibacter xylinus is used. The micro- and nanofibrillar structure of BC, which forms many different-sized pores, creates prerequisites for the introduction of other polymers into it, including those synthesized by other microorganisms. The study aims to develop a cocultivation system of BC and prebiotic producers to obtain BC-based composite material with prebiotic activity. In this study, pullulan (PUL) was found to stimulate the growth of the probiotic strain Lactobacillus rhamnosus GG better than the other microbial polysaccharides gellan and xanthan. BC/PUL biocomposite with prebiotic properties was obtained by cocultivation of Komagataeibacter xylinus and Aureobasidium pullulans, BC and PUL producers respectively, on molasses medium. The inclusion of PUL in BC is proved gravimetrically by scanning electron microscopy and by Fourier transformed infrared spectroscopy. Cocultivation demonstrated a composite effect on the aggregation and binding of BC fibers, which led to a significant improvement in mechanical properties. The developed approach for “grafting” of prebiotic activity on BC allows preparation of environmentally friendly composites of better quality.
KW  - coculture
KW  - pullulan
KW  - exopolysaccharides
KW  - prebiotic
KW  - bacterial cellulose
Y1  - 2022
U6  - http://dx.doi.org/10.3390/polym14153224
SN  - 2073-4360
N1  - This article belongs to the Special Issue "Cellulose Based Composites"
VL  - 14
IS  - 15
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Mandekar, Swati
A1  - Holland, Abigail
A1  - Thielen, Moritz
A1  - Behbahani, Mehdi
A1  - Melnykowycz, Mark
T1  - Advancing towards Ubiquitous EEG, Correlation of In-Ear EEG with Forehead EEG
JF  - Sensors
N2  - Wearable EEG has gained popularity in recent years driven by promising uses outside of clinics and research. The ubiquitous application of continuous EEG requires unobtrusive form-factors that are easily acceptable by the end-users. In this progression, wearable EEG systems have been moving from full scalp to forehead and recently to the ear. The aim of this study is to demonstrate that emerging ear-EEG provides similar impedance and signal properties as established forehead EEG. EEG data using eyes-open and closed alpha paradigm were acquired from ten healthy subjects using generic earpieces fitted with three custom-made electrodes and a forehead electrode (at Fpx) after impedance analysis. Inter-subject variability in in-ear electrode impedance ranged from 20 kΩ to 25 kΩ at 10 Hz. Signal quality was comparable with an SNR of 6 for in-ear and 8 for forehead electrodes. Alpha attenuation was significant during the eyes-open condition in all in-ear electrodes, and it followed the structure of power spectral density plots of forehead electrodes, with the Pearson correlation coefficient of 0.92 between in-ear locations ELE (Left Ear Superior) and ERE (Right Ear Superior) and forehead locations, Fp1 and Fp2, respectively. The results indicate that in-ear EEG is an unobtrusive alternative in terms of impedance, signal properties and information content to established forehead EEG.
KW  - in-ear EEG
KW  - correlation
KW  - forehead EEG
KW  - impedance spectroscopy
KW  - biopotential electrodes
Y1  - 2022
U6  - http://dx.doi.org/10.3390/s22041568
SN  - 1424-8220
VL  - 22
IS  - 4
SP  - 1
EP  - 19
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Maurischat, Andreas
T1  - Algebraic independence of the Carlitz period and its hyperderivatives
JF  - Journal of Number Theory
KW  - Drinfeld modules
KW  - Periods
KW  - t-modules
KW  - Transcendence
KW  - Higher derivations
Y1  - 2022
U6  - http://dx.doi.org/10.1016/j.jnt.2022.01.006
SN  - 0022-314X
VL  - 240
SP  - 145
EP  - 162
PB  - Elsevier
CY  - Orlando, Fla.
ER  - 
TY  - JOUR
A1  - Stäudle, Benjamin
A1  - Seynnes, Olivier
A1  - Laps, Guido
A1  - Brüggemann, Gert-Peter
A1  - Albracht, Kirsten
T1  - Altered gastrocnemius contractile behavior in former achilles tendon rupture patients during walking
JF  - Frontiers in Physiology
N2  - Achilles tendon rupture (ATR) remains associated with functional limitations years after injury. Architectural remodeling of the gastrocnemius medialis (GM) muscle is typically observed in the affected leg and may compensate force deficits caused by a longer tendon. Yet patients seem to retain functional limitations during—low-force—walking gait. To explore the potential limits imposed by the remodeled GM muscle-tendon unit (MTU) on walking gait, we examined the contractile behavior of muscle fascicles during the stance phase. In a cross-sectional design, we studied nine former patients (males; age: 45 ± 9 years; height: 180 ± 7 cm; weight: 83 ± 6 kg) with a history of complete unilateral ATR, approximately 4 years post-surgery. Using ultrasonography, GM tendon morphology, muscle architecture at rest, and fascicular behavior were assessed during walking at 1.5 m⋅s–1 on a treadmill. Walking patterns were recorded with a motion capture system. The unaffected leg served as control. Lower limbs kinematics were largely similar between legs during walking. Typical features of ATR-related MTU remodeling were observed during the stance sub-phases corresponding to series elastic element (SEE) lengthening (energy storage) and SEE shortening (energy release), with shorter GM fascicles (36 and 36%, respectively) and greater pennation angles (8° and 12°, respectively). However, relative to the optimal fascicle length for force production, fascicles operated at comparable length in both legs. Similarly, when expressed relative to optimal fascicle length, fascicle contraction velocity was not different between sides, except at the time-point of peak series elastic element (SEE) length, where it was 39 ± 49% lower in the affected leg. Concomitantly, fascicles rotation during contraction was greater in the affected leg during the whole stance-phase, and architectural gear ratios (AGR) was larger during SEE lengthening. Under the present testing conditions, former ATR patients had recovered a relatively symmetrical walking gait pattern. Differences in seen AGR seem to accommodate the profound changes in MTU architecture, limiting the required fascicle shortening velocity. Overall, the contractile behavior of the GM fascicles does not restrict length- or velocity-dependent force potentials during this locomotor task.
KW  - tendon rupture
KW  - muscle fascicle behavior
KW  - walking gait
KW  - force generation
KW  - ultrasound imaging
Y1  - 2022
U6  - http://dx.doi.org/10.3389/fphys.2022.792576
SN  - 1664-042X
VL  - 13
PB  - Frontiers Research Foundation
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Kotliar, Konstantin
A1  - Ortner, Marion
A1  - Conradi, Anna
A1  - Hacker, Patricia
A1  - Hauser, Christine
A1  - Günthner, Roman
A1  - Moser, Michaela
A1  - Muggenthaler, Claudia
A1  - Diehl-Schmid, Janine
A1  - Priller, Josef
A1  - Schmaderer, Christoph
A1  - Grimmer, Timo
T1  - Altered retinal cerebral vessel oscillation frequencies in Alzheimer's disease compatible with impaired amyloid clearance
JF  - Neurobiology of Aging
N2  - Retinal vessels are similar to cerebral vessels in their structure and function. Moderately low oscillation frequencies of around 0.1 Hz have been reported as the driving force for paravascular drainage in gray matter in mice and are known as the frequencies of lymphatic vessels in humans. We aimed to elucidate whether retinal vessel oscillations are altered in Alzheimer's disease (AD) at the stage of dementia or mild cognitive impairment (MCI). Seventeen patients with mild-to-moderate dementia due to AD (ADD); 23 patients with MCI due to AD, and 18 cognitively healthy controls (HC) were examined using Dynamic Retinal Vessel Analyzer. Oscillatory temporal changes of retinal vessel diameters were evaluated using mathematical signal analysis. Especially at moderately low frequencies around 0.1 Hz, arterial oscillations in ADD and MCI significantly prevailed over HC oscillations and correlated with disease severity. The pronounced retinal arterial vasomotion at moderately low frequencies in the ADD and MCI groups would be compatible with the view of a compensatory upregulation of paravascular drainage in AD and strengthen the amyloid clearance hypothesis.
KW  - Alzheimer's disease
KW  - Retinal vessel analysis
KW  - Vasomotions
KW  - Pulsations
KW  - Mild cognitive impairment
Y1  - 2022
U6  - http://dx.doi.org/10.1016/j.neurobiolaging.2022.08.012
SN  - 0197-4580
VL  - 120
SP  - 117
EP  - 127
PB  - Elsevier
CY  - Amsterdam
ER  -