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Global trends such as climate change and the scarcity of sustainable raw materials require adaptive, more flexible and resource-saving wastewater infrastructures for rural areas. Since 2018, in the community Reinighof, an isolated site in the countryside of Rhineland Palatinate (Germany), an autarkic, decentralized wastewater treatment and phosphorus recovery concept has been developed, implemented and tested. While feces are composted, an easy-to-operate system for producing struvite as a mineral fertilizer was developed and installed to recover phosphorus from urine. The nitrogen-containing supernatant of this process stage is treated in a special soil filter and afterwards discharged to a constructed wetland for grey water treatment, followed by an evaporation pond. To recover more than 90% of the phosphorus contained in the urine, the influence of the magnesium source, the dosing strategy, the molar ratio of Mg:P and the reaction and sedimentation time were investigated. The results show that, with a long reaction time of 1.5 h and a molar ratio of Mg:P above 1.3, constraints concerning magnesium source can be overcome and a stable process can be achieved even under varying boundary conditions. Within the special soil filter, the high ammonium nitrogen concentrations of over 3000 mg/L in the supernatant of the struvite reactor were considerably reduced. In the effluent of the following constructed wetland for grey water treatment, the ammonium-nitrogen concentrations were below 1 mg/L. This resource efficient decentralized wastewater treatment is self-sufficient, produces valuable fertilizer and does not need a centralized wastewater system as back up. It has high potential to be transferred to other rural communities.
Ultrasonic welding of titanium alloy Ti6Al4V to carbon fibre reinforced polymer (CFRP) at 20 kHz frequency requires suitable welding tools, so called sonotrodes. The basic function of ultrasonic welding sonotrodes is to oscillate with displacement amplitudes typically up to 50 µm at frequencies close to the eigenfrequency of the oscillation unit. Material properties, the geometry of the sonotrode, and the sonotrode tip topography together determine the longevity of the sonotrode. Durable sonotrodes for ultrasonic welding of high-strength joining partners, e.g., titanium alloys, have not been investigated so far. In this paper, finite element simulations were used to establish a suitable design assuring the oscillation of a longitudinal eigenmode at the operation frequency of the welding machine and to calculate local mechanical stresses. The primary aim of this work is to design a sonotrode that can be used to join high-strength materials such as Ti6Al4V by ultrasonic welding considering the longevity of the welding tools and high-strength joints. Material, sonotrode geometry, and sonotrode tip topography were designed and investigated experimentally to identify the most promising sonotrode design for continuous ultrasonic welding of Ti6AlV4 and CFRP. Eigenfrequency and modal shape were measured in order to examine the reliability of the calculations and to compare the performance of all investigated sonotrodes.
The analysis of benthic bacterial community structure has emerged as a powerful alternative to traditional microscopy-based taxonomic approaches to monitor aquaculture disturbance in coastal environments. However, local bacterial diversity and community composition vary with season, biogeographic region, hydrology, sediment texture, and aquafarm-specific parameters. Therefore, without an understanding of the inherent variation contained within community complexes, bacterial diversity surveys conducted at individual farms, countries, or specific seasons may not be able to infer global universal pictures of bacterial community diversity and composition at different degrees of aquaculture disturbance. We have analyzed environmental DNA (eDNA) metabarcodes (V3–V4 region of the hypervariable SSU rRNA gene) of 138 samples of different farms located in different major salmon-producing countries. For these samples, we identified universal bacterial core taxa that indicate high, moderate, and low aquaculture impact, regardless of sampling season, sampled country, seafloor substrate type, or local farming and environmental conditions. We also discuss bacterial taxon groups that are specific for individual local conditions. We then link the metabolic properties of the identified bacterial taxon groups to benthic processes, which provides a better understanding of universal benthic ecosystem function(ing) of coastal aquaculture sites. Our results may further guide the continuing development of a practical and generic bacterial eDNA-based environmental monitoring approach.
Spatial optical Fourier filtering is a widespread technique for in situ image or light
field processing. However, conventional fixed absorbing patterns or mechanical irises only allow
an inflexible, very restricted control. Thus, we present two electrochromic spatial filters with
ring-shaped or directional segments, which can be individually addressed and continuously tuned
in transmission resulting in up to 512 different filtering states. For realization of the electrochromic
devices, we overcome technical obstacles to realize seamless, gap-free electrochromic segments.
We describe this novel fabrication process and demonstrate the successful application in an
optical Fourier transform set-up.
In cake filtration processes, where particles in a suspension are separated by forming a filter
cake on the filter medium, the resistances of filter cake and filter medium cause a specific pressure
drop which consequently defines the process energy effort. The micromechanics of the filter cake
formation (interactions between particles, fluid, other particles and filter medium) must be considered
to describe pore clogging, filter cake growth and consolidation correctly. A precise 3D modeling
approach to describe these effects is the resolved coupling of the Computational Fluid Dynamics with
the Discrete Element Method (CFD-DEM). This work focuses on the development and validation of a
CFD-DEM model, which is capable to predict the filter cake formation during solid-liquid separation
accurately. The model uses the Lattice-Boltzmann Method (LBM) to directly solve the flow equations
in the CFD part of the coupling and the DEM for the calculation of particle interactions. The developed
model enables the 4-way coupling to consider particle-fluid and particle-particle interactions. The
results of this work are presented in two steps. First, the developed model is validated with an
empirical model of the single particle settling velocity in the transition regime of the fluid-particle
flow. The model is also enhanced with additional particles to determine the particle-particle influence.
Second, the separation of silica glass particles from water in a pressurized housing at constant pressure
is experimentally investigated. The measured filter cake, filter medium and interference resistances
are in a good agreement with the results of the 3D simulations, demonstrating the applicability of the
resolved CFD-DEM coupling for analyzing and optimizing cake filtration processes.
Tumor emergence and progression is a complex phenomenon that assumes special molecular and cellular interactions. The hierarchical structuring and communication via feedback signaling of different cell types, which are categorized as the stem, progenitor, and differentiated cells in dependence of their maturity level, plays an important role. Under healthy conditions, these cells build a dynamical system that is responsible for facilitating the homeostatic regulation of the tissue. Generally, in this hierarchical setting, stem and progenitor cells are yet likely to undergo a mutation, when a cell divides into two daughter cells. This may lead to the development of abnormal characteristics, i.e. mutation in the cell, yielding an unrestrained number of cells. Therefore, the regulation of a stem cell’s proliferation and differentiation rate is crucial for maintaining the balance in the overall cell population. In this paper, a maturity based mathematical model with feedback regulation is formulated for healthy and mutated cell lineages. It is given in the form of coupled ordinary and partial differential equations. The focus is laid on the dynamical effects resulting from acquiring a mutation in the hierarchical structure of stem, progenitor and fully differentiated cells. Additionally, the effects of nonlinear feedback regulation from mature cells into both stem and progenitor cell populations have been inspected. The steady-state solutions of the model are derived analytically. Numerical simulations and results based on a finite volume scheme underpin various expected behavioral patterns of the homeostatic regulation and cancer evolution. For instance, it has been found that the mutated cells can experience significant growth even with a single somatic mutation, but under homeostatic regulation acquire a steady-state and thus, ensuing healthy cell population to either a steady-state or a lower cell concentration. Furthermore, the model behavior has been validated with different experimentally measured tumor values from the literature.
Study aim: To find out, without relying on gait-specific assumptions or prior knowledge, which parameters are most important for the description of asymmetrical gait in patients after total hip arthroplasty (THA).
Material and methods: The gait of 22 patients after THA was recorded using an optical motion capture system. The waveform data of the marker positions, velocities, and accelerations, as well as joint and segment angles, were used as initial features. The random forest (RF) and minimum-redundancy maximum-relevance (mRMR) algorithms were chosen for feature selection. The results were compared with those obtained from the use of different dimensionality reduction methods.
Results: Hip movement in the sagittal plane, knee kinematics in the frontal and sagittal planes, marker position data of the anterior and posterior superior iliac spine, and acceleration data for markers placed at the proximal end of the fibula are highly important for classification (accuracy: 91.09%). With feature selection, better results were obtained compared to dimensionality reduction.
Conclusion: The proposed approaches can be used to identify and individually address abnormal gait patterns during the rehabilitation process via waveform data. The results indicate that position and acceleration data also provide significant information for this task.
We present a study of optoelectronically active Ga(As)As quantum dots (QDs) on Al-rich AlxGa1-xAs layers with Al concentrations
up to x=90%. So far, however, it has not been possible to grow optoelectronically active Ga(As)As QDs epitaxially
directly on and in between Al-rich barrier layers in the AlGaInAsSb material system. A QD morphology might appear on the
growth front, but the QD-like entities will not luminesce. Here, we use photoluminescence (PL) measurements to show that thin
Al-free capsule layers between Al-rich barrier layers and the QD layers can solve this problem; this way, the QDs become
optoelectronically active; that is, the dots become QDs. We consider antimonide QDs, that is, Ga(As)Sb QDs, either on GaAs for
comparison or on AlxGa1-xAs barriers (x >10%) with GaAs capsule layers in between. We also discuss the influence of QD
coupling both due to stress/strain from neighboring QDs and quantum-mechanically on the wavelength of the photoluminescence
peak. Due to their mere existence, the capsule layers alter the barriers by becoming part of them. Quantum dots
applications such as QD semiconductor lasers for spectroscopy or QDs as binary storage cells will profit from this additional
degree of design freedom.
Reflectance anisotropy spectroscopy (RAS), which was originally invented to monitor
epitaxial growth, can—as we have previously shown—also be used to monitor the reactive ion
etching of III/V semiconductor samples in situ and in real time, as long as the etching rate is not
too high and the abrasion at the etch front is not totally chaotic. Moreover, we have proven that—
using RAS equipment and optical Fabry-Perot oscillations due to the ever-shrinking thickness of the
uppermost etched layer—the in situ etch-depth resolution can be as good as +/-0.8 nm, employing a
Vernier-scale type measurement and evaluation procedure. Nominally, this amounts to +/-1.3 lattice
constants in our exemplary material system, AlGaAsSb, on a GaAs or GaSb substrate. In this
contribution, we show that resolutions of about +/-5.6 nm can be reliably achieved without a Vernier
scale protocol by employing thin doped layers or sharp interfaces between differently doped layers
or quantum-dot (QD) layers as etch-stop indicators. These indicator layers can either be added
to the device layer design on purpose or be part of it incidentally due to the functionality of the
device. For typical etch rates in the range of 0.7 to 1.3 nm/s (that is, about 40 to 80 nm/min), the RAS
spectrum will show a distinct change even for very thin indicator layers, which allows for the precise
termination of the etch run.
Synaptic transmission is controlled by re-uptake systems that reduce transmitter concentrations in the synaptic cleft and recycle the transmitter into presynaptic terminals. The re-uptake systems are thought to ensure cytosolic concentrations in the terminals that are sufficient for reloading empty synaptic vesicles (SVs). Genetic deletion of glycine transporter 2 (GlyT2) results in severely disrupted inhibitory neurotransmission and ultimately to death. Here we investigated the role of GlyT2 at inhibitory glycinergic synapses in the mammalian auditory brainstem. These synapses are tuned for resilience, reliability, and precision, even during sustained high-frequency stimulation when endocytosis and refilling of SVs probably contribute substantially to efficient replenishment of the readily releasable pool (RRP). Such robust synapses are formed between MNTB and LSO neurons (medial nucleus of the trapezoid body, lateral superior olive). By means of patch-clamp recordings, we assessed the synaptic performance in controls, in GlyT2 knockout mice (KOs), and upon acute pharmacological GlyT2 blockade. Via computational modeling, we calculated the reoccupation rate of empty release sites and RRP replenishment kinetics during 60-s challenge and 60-s recovery periods. Control MNTB-LSO inputs maintained high fidelity neurotransmission at 50 Hz for 60 s and recovered very efficiently from synaptic depression. During 'marathon-experiments' (30,600 stimuli in 20 min), RRP replenishment accumulated to 1,260-fold. In contrast, KO inputs featured severe impairments. For example, the input number was reduced to ~1 (vs. ~4 in controls), implying massive functional degeneration of the MNTB-LSO microcircuit and a role of GlyT2 during synapse maturation. Surprisingly, neurotransmission did not collapse completely in KOs as inputs still replenished their small RRP 80-fold upon 50 Hz | 60 s challenge. However, they totally failed to do so for extended periods. Upon acute pharmacological GlyT2 inactivation, synaptic performance remained robust, in stark contrast to KOs. RRP replenishment was 865-fold in marathon-experiments, only ~1/3 lower than in controls. Collectively, our empirical and modeling results demonstrate that GlyT2 re-uptake activity is not the dominant factor in the SV recycling pathway that imparts indefatigability to MNTB-LSO synapses. We postulate that additional glycine sources, possibly the antiporter Asc-1, contribute to RRP replenishment at these high-fidelity brainstem synapses.