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Electromagnetic Waves in Crystals: The Presence of Exceptional Points
No full textAlthough the investigation of the propagation of electromagnetic waves in
crystals dates back to the 19th century, the presence of singular optic axes in
optically anisotropic materials has not been fully explored until now. Along such
an axis, either a left or a right circular polarized wave can propagate without
changing its polarization state. More generally, these singular optic axes belong
to exceptional points (EPs) in the momentum space and correspond to a
simultaneous degeneration of the eigenmodes and their propagation properties.
Herein, a comprehensive discussion on EPs in optically anisotropic materials,
their occurrence, and properties as well as the properties of the electromagnetic
waves propagating along such EPs is presented. The presence of such EPs, their
spatial and spectral distribution in bulk, and semi-infinite and finite crystals are
discussed. It is shown that the presence of interfaces has a strong impact on the
presence of the EPs and their spatial distribution. At an EP, the propagation of
an arbitrarily polarized wave cannot be described by a superposition of two
eigenmodes, as typically described in textbooks. This leads to singularities if the
reflection and transmission coefficients have to be calculated. Here, two
approaches are presented to overcome these limitations
Determiner Phrase Internal Agreement Asymmetries in Grassfields Bantu: A Morphological Approach
No full textA considerable number of Grassfields Bantu languages instantiate DP-internal re-ordering for modifier focus that, in turn, affects the spell out of noun class exponents. The dissertation provides a detailed description and analysis of this phenomenon in selected languages. It shows that Grassfields Bantu can be sorted into at least six different groups, based on the behaviour of noun class prefixes in modifier-focus contexts. In the first, focus has an effect on the spell out of the nominal prefix, in the sense that a possessive pronoun in information-structure-neutral context (post-nominal word order) requires the drop of the nominal prefix. In focus (pre-nominal word order), dropping it is not allowed (see, e.g., Aghem). The second contains languages in which the agreement prefix is affected in specific noun classes, and the new prefix does not realize any semantic information (e.g., Medumba and Ghomala’). In Shupamem-type languages, singular and plural agreement markers are always affected, as they become a single glide that is also not sensitive to the semantics of the head noun. In the fourth group, agreement prefixes are only affected in the singular, and the new prefixes reflect the animacy specification of the head noun
(e.g., Ngemba). Nweh belongs to the fifth group, as nominal and agreement prefixes are not affected, but extra agreeing particles (albeit with limited class distinctions) are required before the focused modifier. In the last group, no segmental changes are visible on nominal and agreement prefixes (e.g., Bafut, Limbum and Yemba).
The dissertation argues that a unified account of languages in which modifier focus affects the spell out of the agreement prefix (Medumba-type, Ngemba-type and Shupamem-type languages) is possible, in an approach that assumes that the relevant changes happen in the morphology. In the syntax, probes on agreeing modifiers always get the features they need to spell out regular class markers. In the morphology, however, the A-bar feature on the focus head triggers impoverishment rules in specific contexts and, as a result, give rise to the observed changes (see also Baier 2018b; Fongang 2025; Ershova To appear).
For Aghem-type languages – where modifier focus affects the spell out of the nominal
prefix – I first propose an account of class drop that relies on the idea that the phenomenon is an instance of haplological dissimilation (see Nevins 2012 for an overview) that is sensitive to strictly local repetition of identical phi-features. I propose that the repetition is avoided by obliterating (Arregi & Nevins, 2012) the head that spells out inherent class features. To derive the fact that prefix drop is not allowed in focus contexts, I show that modifier focus in Aghem involves two DPs, and one of the two is deleted for economy (c.f., Landau 2006). Prefix deletion is blocked because it would otherwise lead to a scenario where information about class membership is lost altogether.
For Nweh-type languages, I show – given a parallel with the clausal domain – that the
extra agreeing particles spell out the movement feature itself. Their surface form results from phi-feature-sensitive allomorphy rules
In Vivo Longitudinal Monitoring of Changes in the Corpus Callosum Integrity During Disease Progression in a Mouse Model of Alzheimer’s Disease
No full textOxygen Plasma Treatment to Enable Indium Oxide MESFET Devices
No full textMetal-semiconductor field-effect transistor (MESFET) devices based on
pulsed laser deposition (PLD) grown In2 O3 thin films with on–off ratios
exceeding 6 orders of magnitude and low sub-threshold swing values close to
the thermodynamic limit are reported. Oxygen plasma treatment and
compensation doping with Mg are utilized to suppress the accumulation of
electrons at the surface of In 2 O3 , which is a major obstacle for its use as an
active material in electronic devices. The influence of both methods is
investigated on the electrical properties of thin films as determined by Hall
effect measurements on samples of varying film thickness. Using the
performance of vertical Schottky barrier diodes as a benchmark, fundamental
plasma parameters such as input power and background gas pressure
are optimized
Probing Water Diffusion Inside Crystals of AlPO-5 by PFG NMR and IRM for Heat Storage Applications
No full textDiffusion of water in the aluminophosphates AlPO-5 is studied using a combination of pulsed field gradient NMR and IR microimaging. The concentration profiles measured by the latter allowed to visualize the process of water sorption and propagation into the crystals of AlPO-5. The self-diffusion coefficients obtained by NMR were one order of magnitude higher values compared to corrected ones from the IR microimaging study. The concentration profiles allowed to visualize the process of water sorption and propagation into the crystals of AlPO-5. The obtained results are compared with experimental and simulation data for the water/AlPO-5 system for the literature and discussed in the context of its potential use for heat storage applications
Phenotypic Heterogeneity, Bidirectionality, Universal Cues, Plasticity, Mechanics, and the Tumor Microenvironment Drive Cancer Metastasis
No full textTumor diseases become a huge problem when they embark on a path that advances to
malignancy, such as the process of metastasis. Cancer metastasis has been thoroughly investigated
from a biological perspective in the past, whereas it has still been less explored from a physical
perspective. Until now, the intraluminal pathway of cancer metastasis has received the most attention,
while the interaction of cancer cells with macrophages has received little attention. Apart from
the biochemical characteristics, tumor treatments also rely on the tumor microenvironment, which
is recognized to be immunosuppressive and, as has recently been found, mechanically stimulates
cancer cells and thus alters their functions. The review article highlights the interaction of cancer
cells with other cells in the vascular metastatic route and discusses the impact of this intercellular
interplay on the mechanical characteristics and subsequently on the functionality of cancer cells.
For instance, macrophages can guide cancer cells on their intravascular route of cancer metastasis,
whereby they can help to circumvent the adverse conditions within blood or lymphatic vessels.
Macrophages induce microchannel tunneling that can possibly avoid mechanical forces during
extra- and intravasation and reduce the forces within the vascular lumen due to vascular flow. The
review article highlights the vascular route of cancer metastasis and discusses the key players in this
traditional route. Moreover, the effects of flows during the process of metastasis are presented, and
the effects of the microenvironment, such as mechanical influences, are characterized. Finally, the
increased knowledge of cancer metastasis opens up new perspectives for cancer treatment
Modeling membrane geometries implicitly in Rosetta
No full textInteractions between membrane proteins (MPs) and lipid bilayers are critical
for many cellular functions. In the Rosetta molecular modeling suite, the
implicit membrane energy function is based on a “slab” model, which repre-
sent the membrane as a flat bilayer. However, in nature membranes often have
a curvature that is important for function and/or stability. Even more preva-
lent, in structural biology research MPs are reconstituted in model membrane
systems such as micelles, bicelles, nanodiscs, or liposomes. Thus, we have
modified the existing membrane energy potentials within the RosettaMP
framework to allow users to model MPs in different membrane geometries.
We show that these modifications can be utilized in core applications within
Rosetta such as structure refinement, protein–protein docking, and protein
design. For MP structures found in curved membranes, refining these struc-
tures in curved, implicit membranes produces higher quality models with
structures closer to experimentally determined structures. For MP systems
embedded in multiple membranes, representing both membranes results in
more favorable scores compared to only representing one of the membranes.
Modeling MPs in geometries mimicking the membrane model system used in
structure determination can improve model quality and model discrimination
Synthesis, structures and optical properties of mononuclear La, Eu and Tb complexes supported by calix[4]arene ligands bearing three pendant salicylaldiminato arms
No full textThe synthesis and complexation behaviour of a new calix[4]arene ligand H4L3 bearing three pendant salicylaldimine arms towards selected lanthanide ions has been investigated. Reaction of H4L3 with Ln(NO3)3⋅6H2O in MeOH in the presence of NEt3 provides monomeric complexes of composition [Ln(HL3)] (Ln=La3+ (4), Eu3+ (5), Tb3+ (6)). An X-ray crystallographic analysis for 4 reveals that only two of the three ligand arms are involved in the coordination of the lanthanide ions, to give eight-coordinated Ln3+ ions in a distorted square-antiprismatic N2O6 environment. UV-vis spectrophotometric titrations show that such monomeric species prevail in CH2Cl2/MeOH (1/1 v/v) solution. The apparent stability constants determined by UV-vis spectrophotometric titration are log K=6.8(2) for 5 and log K=5.8(1) for 6. The Eu and Tb complexes luminesce only weakly at 77 K with luminescence lifetimes of 0.469 and 0.306 s
Spatial Patterns of Vegetation Activity Related to ENSO in Northern South America
No full textInterannual variability of vegetation activity (i.e., photosynthesis) is strongly correlated with El Niño Southern Oscillation (ENSO). Globally, a reduction in carbon uptake by terrestrial ecosystems has been observed during the ENSO warm phase (El Niño) and the opposite during the cold phase (La Niña). However, this global perspective obscures the heterogeneous impacts of ENSO at regional scales. Particularly, ENSO has contrasting impacts on climate in northern South America (NSA) depending on the ENSO phase and geographical location, which in turn affect the activity of vegetation. Furthermore, changes of vegetation activity during multiple ENSO events are not well understood yet. In this study, we investigated the spatial and temporal differences in vegetation activity associated with ENSO variability and its three phases (El Niño, La Niña, Neutral) to identify hotspots of ENSO impacts in NSA, a region dominated by rainforest and savannas. To achieve this, we investigated time series of vegetation variables from 2001 to 2014 at moderate spatial resolution (0.0083°). Data were aggregated through dimensionality reduction analysis (i.e., Global Principal Component Analysis). The leading principal component served as a proxy of vegetation activity (VAC). We calculated the cross-correlation between VAC and the multivariate ENSO index separately for each ENSO phase. Our results show that El Niño phase has a stronger impact on vegetation activity both in intensity and duration than La Niña phase. Moreover, seasonally dry ecoregions were more susceptible to El Niño impacts on vegetation activity. Understanding these differences is key for regional adaptation and differentiated management of ecosystems
