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The phospholipid bilayers are the primary constituents of the membrane in living cells in which lipids are hold together in bilayer leaflets through a combination of different forces into the liquid crystalline (Lα) phase. Despite their thin fragile formations, the phospholipid bilayers are responsible for performing a variety of important tasks in the cells, some of which are carried out directly by the lipid bilayers and some by various integral proteins embedded within the bilayers. There have been continues efforts over the past decades to replicate the compound biophysical properties of living cell membranes in model lipid bilayers.
An important question remains unanswered: is it possible to replicate physical properties under “non-equilibrium” conditions as found in cell membranes in model lipid bilayers? In almost all previous studies, the model lipid bilayers were under static conditions – for instance, at zero lateral pressure. However, in living organisms, the cell membranes are involved in continuous (nonequilibrium) exchange and (or) transport of lipid species with the surrounding environment which consequently leads them to experience continuous lateral pressure variations. One suitable in vitro approach is to spatiotemporally control the model lipid bilayers over a time period during which they can be spatially stimulated at a level compatible to that found under in vivo conditions. This can be achieved with high spatiotemporal resolution by making lipids light-dependent through implementation of azobenzene photoswitch in their structures.
In this study, a specific azobenzene containing photolipid (AzoPC) is integrated into POPE:POPG bilayers (POPE: 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine, POPG: 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol)) at ~14 mol% to construct a photo responsive model bilayers entitled as photoliposomes. Magic angle spinning solid-state NMR spectroscopy (MAS-NMR) at high field (850 MHz) is the measurement technique of choice by which it is possible to pursue the dynamics (fluidity) of the bulk lipids within the photoliposomes at atomistic resolution. It is shown that the AzoPCs undergo an efficient trans-to-cis isomerization (~85%) within the photoliposomes as the result of UV light absorption, and thermally relax back to the trans state during a period of ~65 h under the MAS measurement conditions. The order parameter measurements based on the C−H dipolar couplings reveal that the non-equilibrium cis-to-trans thermal isomerization impact of AzoPC on the fluidity of the bulk lipid is highly localized – the fluidity perturbations originate from specific order parameter changes in the middle section of the bulk lipid acyl chains. Further 1H NOESY measurements confirm the hypothesis that the azoswitch topologies in either cis and trans conformer of the photolipid is the key parameter in localized alteration of the C−H order parameters along the bulk lipid acyl chains.
Diacylglycerol kinase (DgkA) from E. coli is an enzyme responsible for the phosphorylation of diacylglycerol to phosphatidic acid, at the expense of adenosine triphosphate. Structurally, DgkA is a homo oligomer composed of three symmetric 14 kDa protomers, each of which has three transmembrane helices and one surface helix. Upon embedding within the photoliposomes, it is shown that DgkA enhances the AzoPC localization impact on the fluidity of the bulk lipids. In this regard, the results of a series of statistical simulations of lipid lateral diffusions along the bilayer leaflets in presence and absence of embedded proteins are accompanied with those of experimentally measured based upon which it is justified that membrane proteins markedly limit lipid lateral diffusions in the bilayers. In case of the DgkA proteo-liposomes with lipid-to-protein ratio of 50, it is estimated that the diffusion coefficient of lipids is above 2-fold lower compared to that of the protein free liposomes.
The cis-to-trans AzoPC isomerization and its following consequence in localized alteration of the bulk lipid fluidity is further investigated on the structural dynamics and enzymatic functionality of the embedded DgkA within the proteo-photoliposomes. It is revealed that DgkA structural dynamics are perturbated in a multi-scale, complex manner. The dynamics of residues located in different regions of DgkA changes with the light-induced AzoPC isomerization, but their time courses differ from residue to residue. For example, 29Ala, a residue on the hinge between the surface helix and membrane helix-1, exhibits the steepest time-dependent cross peak intensity changes in time-resolved NCA spectra. The impact of the lasting membrane fluidity perturbation on the enzymatic functionality of the embedded DgkA is subsequently measured which demonstrates a significant variation under cis- and trans-AzoPC conformations within the proteo-photoliposomes.
The present work deals with photoionization in the realm of the absorption of one single photon. The formal treatment of one-photon ionization usually employs a semi-classical approach, where the electron’s initial and final states are described as quantum-mechanical wave functions but the photon is treated as a classical electromagnetic wave. In the calculation of photoionization cross sections with this semi-classical method, there is an often used approximation which is called the electric dipole approximation. Mathematically, the application of the dipole approximation corresponds to truncating the series expansion of an exponential after the leading term. Physically, this means neglecting the linear photon momentum and the spatial dependence of the light field. The dipole approximation is valid if the wavelength of the light is much larger than the spatial extent of the target and if the photon momentum is small compared to the momenta of the reaction products, which is generally the case for photon energies short above the electron binding energy.
For the present work, we experimentally investigated nondipolar photoionization, i.e., one-photon ionization at high photon energies where the dipole approximation breaks down. In our experiments, we irradiated single atoms and molecules with such high-energetic photons and measured the three-dimensional momentum distributions of the reaction fragments to uncover the effects of the linear photon momentum and the spatially-dependent light field on photoionization. Our observations allow the first profound insight into photoionization that reveals all photon properties, i.e., photon energy, spin, linear momentum, and the speed of light. Hopefully, our efforts make a constructive contribution to the understanding and the further exploration of light-matter interaction.
This work is about resumptive and non-resumptive relative clauses (RCs) in the three big Ibero-Romance languages: Spanish, Portuguese, and Catalan. In (1), the examined structures are exemplified for Spanish: (1a.) No conozco el hombre que viste _ ayer. “I don’t know the man that you saw yesterday.” (1b.) Es este el hombre que le enviaron el libro. “This is the man to whom they sent the book.” (1c.) Es este el hombre a quien le enviaron el libro. “This is the man to whom they sent the book.”
(1a.) displays a non-resumptive, or canonical, RC, which is characterized by the canonical use of a relativizing operator and a gap in the subordinate’s object position, a piece of evidence which has induced most of the generative literature to assume wh-movement of the relative operator in the sense of Chomsky (1977). The last two decades, however, have seen a big debate regarding the exact derivational analysis, starting with Kayne’s (1994) antisymmetry theory and the following focus on reconstruction and anti-reconstruction effects in RCs. This search for the correct starting site of the RC’s head noun has dismissed the original Head External Analysis (HEA) (Chomsky 1965, 1977) and led to the development of a Head Raising Analysis (RA) (Kayne 1994, Bianchi 1999, a.o.) and a Matching Analysis (MA) (Munn 1994, Sauerland 1998, a.o.). The discussion in this work argues that the data on reconstruction and anti-reconstruction effects are not sufficiently clear and reliable in order to adopt one of the head-internal analyses, i.e. a HEA or a MA. Instead, the work follows a variant of the HEA proposed for Portuguese by Rinke & Aßmann (2017), which adheres to standard assumptions about Romance syntax, and avoids the empirical problems that the other proposals have to face. Arguing that the HEA holds for all Ibero-Romance languages, this work also takes a stance in the debate around the categorical status of the relativizing element que and argues that it is always a D-element, and never of category C, i.e. there is no such thing as a relativizing complementizer (cf. also Kayne 2010, Kato & Nunes 2008, Poletto & Sanfelici 2018).
The work argues that wh-movement in a HEA fashion is the correct analysis also for resumptive relative clauses as in (1b., c.), which crucially lack a gap in argument position but show a resumptive pronominal element instead. Furthermore, it takes advantage of the fact that the choice of such genetically closely related languages like Spanish, Portuguese, and Catalan enables research to address the phenomenon under consideration from a microcomparative perspective, which is “the closest we can come … to a controlled experiment in comparative syntax” (Kayne 2005: 281-282). The descriptive literature suggests that, at least for Spanish and Catalan, there are two types of a resumptive RC structure available: a simple resumption as in (1b.), including mere que, and a complex resumption structure which displays a more complex relativizer like a quien in combination with a resumptive pronoun (1c.). However, a corpus study carried out for this work reveals that speakers of the three languages behave alike insofar as the only resumptive RC used in spontaneous speech is a simple-resumption structure, while complex resumption never occurs. Additionally, a multivariate analysis shows that in all three languages, grammatical case is the most important factor when it comes to the possibility of a resumptive structure in RCs: with a dative argument, simple resumption is obligatory, while for accusative and nominative arguments, resumption is optional. The discussion concludes that simple and complex resumption constitute different phenomena also on a structural level: the latter one is argued to be a subcase of clitic doubling, and therefore, receives an analysis along the lines of Pineda (2016), who argues against a dative alternation in Romance languages and locates the (non-)realisation of the dative clitic in a transitive clitic-doubling structure outside of syntax, it being a case of silent variation along the lines of Sigurðsson (2004) and Kayne (2005). From this perspective, it follows naturally that in Portuguese, complex resumption structures are ungrammatical. Simple resumption, on the other hand, which is a possible structure in all three languages, is argued to represent the phonological counterpart of “scattered deletion”, i.e. the preferred interpretation for an A’-chain according to Chomsky (2003): in the operator position SpecCP, every feature except for the operator feature is deleted, resulting in the phonological outcome que, while in the variable position, everything but the operator is interpreted, resulting in a pronominal element according to the argument’s phi-features.
This work takes a stance in the latest topics on generative analyses for relative clauses. Using not only theoretical considerations but conclusions drawn from empirical data on three languages, it offers a new perspective on pending questions and proposes to take a fresh look on supposedly outdated analyses.
The book deals with a comprehensive constellation of narrative and visual, often counterposed representations of the causes, course, and results of the assault on the Palace of Justice of Colombia by a guerrilla commando and the immediate counterattack launched by state security forces on November 6, 1985, as well as with the local memorial traditions in which the production, circulation and reproduction of these representations have taken place between 1985 and 2020. The research on which it is based was grounded in the method and perspective of classical anthropology, in as much as qualitative fieldwork and the search for the perspective of the actors involved have played a central role. Within that context, memory entrepreneurs belonging to diverse sectors, from the far-right to the human rights movement, were followed through multisited fieldwork in various locations of Colombia, as well as in various countries of America and Europe. The analyses of fieldwork data, documental sources, and visual representations that constitute the core of the argument are framed in the field of memory studies and mainly based on theoretical and methodological resources from Pierre Bourdieu’s Field Theory, Jeffrey Alexander’s theory of social trauma, and Ernst Gombrich’s characterization of iconological analysis.
The book is composed of four chapters preceded by an introduction and followed by the conclusions and documental appendices, and substantiates three main theses. The first is that the Palace of Justice events were a radio- and television-broadcasted dispersed tragedy that affected the lives of actors from different social sectors and regions of Colombia, who have launched since 1985 multiple memorial initiatives in different fields of culture, thereby contributing to the formation and intergenerational transmission of a widespread cultural trauma. The second is that the narrative and visual representations at the core of that trauma express a vast universe of local representational traditions that can be traced at least until the early 20th century, and therefore preexists the so-called Colombian “memory boom”, dated to the mid-1990s. As an example of the preexistence and longstanding impact of these traditions, the local usage of the figure of “holocaust” for representing the effects of politically motivated violence is analyzed regarding the Palace of Justice events, but also traced to other representations emerged in the decade of 1920. The third thesis is that analyzing the diverse, frequently counterposed accounts of political violence elaborated within these traditions provides an opportunity to explore a wide variety of understandings of the causes and characteristics of the longstanding Colombian social and armed conflict.
Keywords: Political violence, Cultural trauma, Collective Memory, Iconology, Holocaust, Colombia.
This thesis examines the referential properties of prenominal possessive modifiers in Serbian. The focus of the investigation is on the configurations that have been claimed to violate Binding Principles B and C: lexical or pronominal possessives modifying a noun in subject position binding a pronoun or an R-expression in object position. Such constructions have been claimed to be ungrammatical in Serbian due to the alleged adjectival status of the possessive and its respective syntactic position as NP-adjoined (Despić 2013).
The present thesis takes up the ongoing debate about the categorial status of Serbian possessives as adjectives or determiners. Based on several arguments, such as word order, binding of anaphora, coordination, and the fact that they are typically represented by either nouns or pronouns, it is concluded that possessives rather behave like full noun phrases than adjectives. Therefore, I analyse possessives as DPs from a categorial point of view.
In a second step, the syntactic position of the possessives within the Serbian noun phrase has been investigated. Based on theoretical arguments (cf. Bašić 2004) and empirical evidence, I propose a structural position that would accommodate the binding facts and the referential possibilities in these configurations. In line with Kayne (1994), Bernstein and Tortora (2005) and Alexiadou et al. (2007), I assume that possessives occupy SpecAgrP in Serbian, where they move from their base position (SpecPossP). Thirdly, I question the (im)possibility of coreference with possessives in comparison to ‘typical’ binding constructions without possessives by providing empirical evidence from three experimental studies, showing that coreference between possessive modifiers and objects is indeed available in Serbian.
The results from Experiment 1 (a picture selection task) have shown that coreference between a lexical possessive and a (clitic or strong) pronoun is allowed in Serbian. Further, there is a tendency that the coreferential reading is preferred with clitics, while the disjoint reference is preferred with strong pronouns. The fact that coreference is possible, does not necessarily mean that it is always available as the only interpretation, but can be influenced by other (pragmatic) factors. The same is observed in Experiments 2 and 3 as coreference was chosen between pronominal possessives modifying a noun in subject position and R-expressions but rejected between pronouns and R-expressions in a forced-choice task, suggesting a structural difference – no c-command – in the former case. The results from the self-paced reading task corroborate this finding.
Importantly, the experimental results provide evidence that possessive configurations are not violating Binding Principles B and C. This implies that Serbian possessive constructions do not c-command out of the noun phrase, as predicted by the proposed syntactic analysis.
The findings from all experiments contribute to the bigger picture concerning the nature and behaviour of Serbian possessives and cast doubt on the cross-linguistic DG/AG parameter. Instead, the theoretical arguments and the empirical results from the experiments rather speak for a parallel structure of possessive noun phrases in Serbian and English and ultimately in favour of the Universal DP Hypothesis.