A topology-oblivious routing protocol for NDN-VANETs

Vehicular Ad Hoc Networks (VANETs) are characterized by intermittent connectivity, which leads to failures of end-to-end paths between nodes. Named Data Networking (NDN) is a network paradigm that deals with such problems, since information is forwarded based on content and not on the location of the hosts. In this work, we propose an enhanced routing protocol of our previous topology-oblivious Multihop, Multipath, and Multichannel NDN for VANETs (MMM-VNDN) routing strategy that exploits several paths to achieve more efficient content retrieval. Our new enhanced protocol, i mproved MMM-VNDN (iMMM-VNDN), creates paths between a requester node and a provider by broadcasting Interest messages. When a provider responds with a Data message to a broadcast Interest message, we create unicast routes between nodes, by using the MAC address(es) as the distinct address(es) of each node. iMMM-VNDN extracts and thus creates routes based on the MAC addresses from the strategy layer of an NDN node. Simulation results show that our routing strategy performs better than other state of the art strategies in terms of Interest Satisfaction Rate, while keeping the latency and jitter of messages low

Complete Intersection Fibers in F-Theory

Global F-theory compactifications whose fibers are realized as complete intersections form a richer set of models than just hypersurfaces. The detailed study of the physics associated with such geometries depends crucially on being able to put the elliptic fiber into Weierstrass form. While such a transformation is always guaranteed to exist, its explicit form is only known in a few special cases. We present a general algorithm for computing the Weierstrass form of elliptic curves defined as complete intersections of different codimensions and use it to solve all cases of complete intersections of two equations in an ambient toric variety. Using this result, we determine the toric Mordell-Weil groups of all 3134 nef partitions obtained from the 4319 three-dimensional reflexive polytopes and find new groups that do not exist for toric hypersurfaces. As an application, we construct several models that cannot be realized as toric hypersurfaces, such as the first toric SU(5) GUT model in the literature with distinctly charged 10 representations and an F-theory model with discrete gauge group Z_4 whose dual fiber has a Mordell-Weil group with Z_4 torsion.Comment: 41 pages, 4 figures and 18 tables; added references in v

New Global F-theory GUTs with U(1) symmetries

We construct global F-theory GUTs with SU(5) x U(1) gauge group defined by specifying a fully resolved Calabi-Yau fourfold and consistent four-form G-flux. Its specific U(1) charged matter spectrum allows the desired Yukawa couplings, but forbids dangerous proton decay operators. The model we find: (1) does not follow from an underlying higgsed E8 gauge group (2) leaves the class of theories that can be analyzed with current split-spectral cover techniques. This avoids recently proposed no-go theorems for models with hypercharge flux, as required to break the GUT group. The appearance of additional fields is related geometrically to considering a more general class of sections and 4-1 splits. We show explicitly that the four-dimensional chiral matter index can still be computed using three-dimensional one-loop Chern-Simons terms.Comment: 24 pages, 2 figure

The Economic Integration of Forced Migrants: Evidence for Post-War Germany

The flight and expulsion of Germans from Eastern Europe during and after World War II constitutes one of the largest forced population movements in history. We analyze the economic integration of these forced migrants and their offspring in West Germany. The empirical results suggest that even a quarter of a century after displacement, first generation migrants and native West Germans that were comparable before the war perform strikingly different. Migrants have substantially lower incomes and are less likely to own a house or to be self-employed. Displaced agricultural workers, however, have significantly higher incomes. This income gain can be explained by faster transitions out of low-paid agricultural work. Differences in the labor market performance of second generation migrants resemble those of the first generation. We also find that displacement considerably weakens the intergenerational transmission of human capital between fathers and children, especially at the lower tail of the skill distribution.forced migration, economic integration, World War II, West Germany

Noncoder : a web interface for exon array-based detection of long non-coding RNAs

Due to recent technical developments, a high number of long non-coding RNAs (lncRNAs) have been discovered in mammals. Although it has been shown that lncRNAs are regulated differently among tissues and disease statuses, functions of these transcripts are still unknown in most cases. GeneChip Exon 1.0 ST Arrays (exon arrays) from Affymetrix, Inc. have been used widely to profile genome-wide expression changes and alternative splicing of protein-coding genes. Here, we demonstrate that re-annotation of exon array probes can be used to profile expressions of tens of thousands of lncRNAs. With this annotation, a detailed inspection of lncRNAs and their isoforms is possible. To allow for a general usage to the research community, we developed a user-friendly web interface called 'noncoder'. By uploading CEL files from exon arrays and with a few mouse clicks and parameter settings, exon array data will be normalized and analysed to identify differentially expressed lncRNAs. Noncoder provides the detailed annotation information of lncRNAs and is equipped with unique features to allow for an efficient search for interesting lncRNAs to be studied further. The web interface is available at http://noncoder.mpi-bn.mpg.de

2D-crystallization and 3D-structures of membrane channels and transporters

Membrane proteins are responsible for a broad spectrum of biological functions such as signal transduction, structural functions, energy conversion or transport of matter across the membranes. Around 30% of the protein-sequences encode membrane-proteins [88, 80]: Most of them are not directly involved in cell-housekeeping functions but are indispensable for multicellular life. Therefore, many of these proteins are of high importance in various medical relevant areas, such as neurobiology, cell-cycle controlling or immune response, just to mention a few of them. Malfunctions of these proteins can result in severe diseases such as Cystic Fibrosis. Other membrane-proteins, such as the multidrug resistance-pump, are responsible for major medical problems if they are present: Examples are the resistance of microbes against antibiotics or ineffective treatments of cancer patients due to resistance of the cancer cell against the chemotherapeutic agents. The medical relevance of these proteins was and is accompanied by a lack of structural information. However, significant progress was made in the last three years. Several leading structures were solved for some protein-families, mostly using large automated screening approaches. But others are still in the dark. Furthermore, the current structure exploration still fails in solving routinely the structure of specific membrane-proteins. More effort has to be put into the development of these methods for specifically crystallizing (in 2D or 3D) medically relevant proteins with the goal of bringing membrane protein structures to structural biology and medicine. 2D-crystallization is a promising approach for these difficult projects since the protein is reconstituted in its natural environment soon after purification. The protein can be kept under physiological conditions for the structural exploration. Some of the obtained 2D-crystals were reported to be still functional active such as the AQP1 crystals [92]. However, as with 3D-crystallization for X-ray crystallography, the 2Dcrystallization is still the bottle-neck in electron crystallography. Chapter 2 describes the attempts to 2D-crystallize a highly flexible multidrug-resistance protein LmrA from Lactococcus lactis. This ABC-transporter was subjected to a broad crystallization pre-screen to find stabilizing conditions for subsequent crystallization experiments: First, various detergents were tested for their ability to preserve LmrA in a healthy state. Since no functionality test for solubilized LmrA was known, indirect methods to test the integrity of the protein had to be used, such as solubilization tests, electron microscopy of solubilized LmrA or sucrose gradients. In the second part of the pre-screen the selected detergents were tested against various lipids for LmrA reconstitution. These reconstitution tests were done with the monolayer technique [41]. From these experiments we learned that the detergents C12E8, Triton X-100 and (with some restriction) DDM are most suitable for further crystallization tests. The lipidscreen revealed that synthetic lipids mimicking the membrane of Lactococcus lactis are better suitable for LmrA-reconstitution than other synthetic lipids (except DMPC). Especially the results for a POPG:cardiolipin mixture seemed to be promising. From the natural lipid-isolates, Escherichia coli -lipid, also containing cardiolipin has the ability to incorporate LmrA in lipid bilayers (see next paragraph). In parallel, reconstitution and crystallization experiments were performed: A major problem was the proper reconstitution of LmrA. Tests of different detergent removal methods revealed, that LmrA reconstitutes nicely in Escherichia coli -lipid by a stepwise detergent-removal with bio-beads [65, 64]. In these experiments, fungi-like structures were visible as spikes sticking out for 6 nm of thick double-membranes. These structures were interpreted as the soluble part of LmrA. The measured dimensions are compatible with the findings of Chang et al., 2001 [10] on MsbA, a LmrA homologue of Escherichia coli. Taken together, these results are a good starting point for further crystallization experiments, if the found conditions can be combined and the protein can be trapped in a specific confirmation using LmrA-inhibitors. In chapter 3 the successful 2D-crystallization of GlpF, the glycerol facilitator protein of Escherichia coli, is described. To assess the GlpF structure, recombinant histidine tagged protein was overexpressed, solubilized in octylglucoside (OG) and purified to homogeneity. Negative stain electron microscopy of solubilized GlpF protein revealed a tetrameric structure of approximately 80 °A sidelength. Scanning transmission electron microscopy (STEM) yielded a mass of 170 kDa corroborating the tetrameric nature of GlpF. These results are contradictory to previous speculations that GlpF is a monomer [9, 39]. However, the tetrameric architecture has been confirmed by the atomic structure of GlpF [23]. Reconstitution of GlpF in the presence of lipids produced highly ordered two dimensional crystals, which diffracted electrons to 3.6 °A resolution. Cryo electron microscopy provided a 3.7°Aprojection map exhibiting a unit cell comprised of two tetramers. In projection, GlpF is similar to AQP1, the erythrocyte water channel. However, the major density minimum within each monomer is distinctly larger in GlpF than in AQP1. This finding was confirmed with the comparison of the refined AQP1 model [14] and the x-ray structure of GlpF [23], see also figure 1.6 p. 12. To obtain the three dimensional (3D) structure of GlpF, the two-dimensional crystals were tilted up to 62� in the electron microscope to get the side-views of the protein. The resulting 6.9 °A density map showed the GlpF helices to be similar to those of AQP1, the erythrocyte water channel. While the helix arrangement of GlpF does not reflect the larger pore diameter as seen in the projection map, additional peripheral densities observed in GlpF are compatible with the 31 additional residues in loops C and E, which accordingly do not interfere with the inner channel construction. Therefore, the atomic structure of AQP1 was used as a basis for homology modeling of the GlpF channel, which was predicted to be free of bends, wider, and more vertically oriented than the AQP1 channel. Furthermore, the residues facing the GlpF channel exhibited an amphiphilic nature, being hydrophobic on one side and hydrophilic on the other side. This property was speculated to partially explain the contradiction of glycerol diffusion but limited water capacity. Both, the additional densities and the greasy slide similar to maltoporin [72] have also been observed in the atomic structure of GlpF [23]. The importance of the amphiphilic channel architecture is also corroborated by molecular dynamic calculations [35]

The Border Battle: North Dakota\u27s Suit Against Minnesota and the Future of the Next Generation Energy Act

Abstrac

The Economic Integration of Forced Migrants – Evidence for Post-War Germany

The fl ight and expulsion of Germans from Eastern Europe during and after World War II constitutes one of the largest forced population movements in history. We analyze the economic integration of these forced migrants and their off spring in West Germany. The empirical results suggest that even a quarter of a century after displacement, fi rst generation migrants and native West Germans that were comparable before the war perform strikingly diff erent. Migrants have substantially lower incomes and are less likely to own a house or to be self-employed. Displaced agricultural workers, however, have signifi cantly higher incomes. This income gain can be explained by faster transitions out of low-paid agricultural work. Diff erences in the labor market performance of second generation migrants resemble those of the fi rst generation. We also fi nd that displacement considerably weakens the intergenerational transmission of human capital between fathers and children, especially at the lower tail of the skill distribution.Forced migration; economic integration; World War II; West Germany