Showing papers by "Technische Universität Darmstadt published in 2010"

Visualization and analysis of atomistic simulation data with OVITO–the Open Visualization Tool

Abstract: The Open Visualization Tool (OVITO) is a new 3D visualization software designed for post-processing atomistic data obtained from molecular dynamics or Monte Carlo simulations. Unique analysis, editing and animations functions are integrated into its easy-to-use graphical user interface. The software is written in object-oriented C++, controllable via Python scripts and easily extendable through a plug-in interface. It is distributed as open-source software and can be downloaded from the website http://ovito.sourceforge.net/.

Secrets of optical flow estimation and their principles

Abstract: The accuracy of optical flow estimation algorithms has been improving steadily as evidenced by results on the Middlebury optical flow benchmark. The typical formulation, however, has changed little since the work of Horn and Schunck. We attempt to uncover what has made recent advances possible through a thorough analysis of how the objective function, the optimization method, and modern implementation practices influence accuracy. We discover that “classical” flow formulations perform surprisingly well when combined with modern optimization and implementation techniques. Moreover, we find that while median filtering of intermediate flow fields during optimization is a key to recent performance gains, it leads to higher energy solutions. To understand the principles behind this phenomenon, we derive a new objective that formalizes the median filtering heuristic. This objective includes a nonlocal term that robustly integrates flow estimates over large spatial neighborhoods. By modifying this new term to include information about flow and image boundaries we develop a method that ranks at the top of the Middlebury benchmark.

Polymer-Derived Ceramics: 40 Years of Research and Innovation in Advanced Ceramics

Abstract: Preceramic polymers were proposed over 30 years ago as precursors for the fabrication of mainly Si-based advanced ceramics, generally denoted as polymer-derived ceramics (PDCs). The polymer to ceramic transformation process enabled significant technological breakthroughs in ceramic science and technology, such as the development of ceramic fibers, coatings, or ceramics stable at ultrahigh temperatures (up to 2000°C) with respect to decomposition, crystallization, phase separation, and creep. In recent years, several important advances have been achieved such as the discovery of a variety of functional properties associated with PDCs. Moreover, novel insights into their structure at the nanoscale level have contributed to the fundamental understanding of the various useful and unique features of PDCs related to their high chemical durability or high creep resistance or semiconducting behavior. From the processing point of view, preceramic polymers have been used as reactive binders to produce technical ceramics, they have been manipulated to allow for the formation of ordered pores in the meso-range, they have been tested for joining advanced ceramic components, and have been processed into bulk or macroporous components. Consequently, possible fields of applications of PDCs have been extended significantly by the recent research and development activities. Several key engineering fields suitable for application of PDCs include high-temperature-resistant materials (energy materials, automotive, aerospace, etc.), hard materials, chemical engineering (catalyst support, food- and biotechnology, etc.), or functional materials in electrical engineering as well as in micro/nanoelectronics. The science and technological development of PDCs are highly interdisciplinary, at the forefront of micro- and nanoscience and technology, with expertise provided by chemists, physicists, mineralogists, and materials scientists, and engineers. Moreover, several specialized industries have already commercialized components based on PDCs, and the production and availability of the precursors used has dramatically increased over the past few years. In this feature article, we highlight the following scientific issues related to advanced PDCs research: (1) General synthesis procedures to produce silicon-based preceramic polymers. (2) Special microstructural features of PDCs. (3) Unusual materials properties of PDCs, that are related to their unique nanosized microstructure that makes preceramic polymers of great and topical interest to researchers across a wide spectrum of disciplines. (4) Processing strategies to fabricate ceramic components from preceramic polymers. (5) Discussion and presentation of several examples of possible real-life applications that take advantage of the special characteristics of preceramic polymers. Note: In the past, a wide range of specialized international symposia have been devoted to PDCs, in particular organized by the American Ceramic Society, the European Materials Society, and the Materials Research Society. Most of the reviews available on PDCs are either not up to date or deal with only a subset of preceramic polymers and ceramics (e.g., silazanes to produce SiCN-based ceramics). Thus, this review is focused on a large number of novel data and developments, and contains materials from the literature but also from sources that are not widely available.

Electromagnetic counterparts of compact object mergers powered by the radioactive decay of r‐process nuclei

Abstract: The most promising astrophysical sources of kHz gravitational waves (GWs) are the inspiral and merger of binary neutron star(NS)/black hole systems. Maximizing the scientific return of a GW detection will require identifying a coincident electromagnetic (EM) counterpart. One of the most likely sources of isotropic EM emission from compact object mergers is a supernova-like transient powered by the radioactive decay of heavy elements synthesized in ejecta from the merger. We present the first calculations of the optical transients from compact object mergers that self-consistently determine the radioactive heating by means of a nuclear reaction network; using this heating rate, we model the light curve with a one-dimensional Monte Carlo radiation transfer calculation. For an ejecta mass ~ 10 -2 M ⊙ (10 -3 M ⊙ ) the resulting light-curve peaks on a time-scale ~1 d at a V-band luminosity vL v ~ 3 x 10 41 (10 41 )erg s -1 [M V = -15(-14)]; this corresponds to an effective 'f' parameter ~3 × 10- 6 in the Li-Paczynski toy model. We argue that these results are relatively insensitive to uncertainties in the relevant nuclear physics and to the precise early-time dynamics and ejecta composition. Since NS merger transients peak at a luminosity that is a factor of ~10 3 higher than a typical nova, we propose naming these events 'kilo-novae'. Because of the rapid evolution and low luminosity of NS merger transients, EM counterpart searches triggered by GW detections will require close collaboration between the GW and astronomical communities. NS merger transients may also be detectable following a short-duration gamma-ray burst or 'blindly' with present or upcoming optical transient surveys. Because the emission produced by NS merger ejecta is powered by the formation of rare r-process elements, current optical transient surveys can directly constrain the unknown origin of the heaviest elements in the Universe.

Extracting dislocations and non-dislocation crystal defects from atomistic simulation data

Abstract: We describe a novel method for extracting dislocation lines from atomistic simulation data in a fully automated way. The dislocation extraction algorithm (DXA) generates a geometric description of dislocation lines contained in an arbitrary crystalline model structure. Burgers vectors are determined reliably, and the extracted dislocation network fulfills the Burgers vector conservation rule at each node. All remaining crystal defects (grain boundaries, surfaces, etc), which cannot be represented by one-dimensional dislocation lines, are output as triangulated surfaces. This geometric representation is ideal for visualization of complex defect structures, even if they are not related to dislocation activity. In contrast to the recently proposed on-the-fly dislocation detection algorithm (ODDA) Stukowski (2010 Modelling Simul. Mater. Sci. Eng. 18 015012) the new method is extremely robust. While the ODDA was designed for a computationally efficient on-the-fly analysis, the DXA method enables a detailed analysis of dislocation lines even in highly distorted crystal regions, as they occur, for instance, close to grain boundaries or in dense dislocation networks.

Quantum discord for two-qubit X states

Abstract: Quantum discord, a kind of quantum correlation, is defined as the difference between quantum mutual information and classical correlation in a bipartite system. In general, this correlation is different from entanglement, and quantum discord may be nonzero even for certain separable states. Even in the simple case of bipartite quantum systems, this different kind of quantum correlation has interesting and significant applications in quantum information processing. So far, quantum discord has been calculated explicitly only for a rather limited set of two-qubit quantum states and expressions for more general quantum states are not known. In this article, we derive explicit expressions for quantum discord for a larger class of two-qubit states, namely, a seven-parameter family of so called X states that have been of interest in a variety of contexts in the field. We also study the relation between quantum discord, classical correlation, and entanglement for a number of two-qubit states to demonstrate that they are independent measures of correlation with no simple relative ordering between them.

Tunable multifunctional topological insulators in ternary Heusler compounds

Abstract: Recently the quantum spin Hall effect was theoretically predicted and experimentally realized in quantum wells based on the binary semiconductor HgTe (refs 1-3). The quantum spin Hall state and topological insulators are new states of quantum matter interesting for both fundamental condensed-matter physics and material science. Many Heusler compounds with C1(b) structure are ternary semiconductors that are structurally and electronically related to the binary semiconductors. The diversity of Heusler materials opens wide possibilities for tuning the bandgap and setting the desired band inversion by choosing compounds with appropriate hybridization strength (by the lattice parameter) and magnitude of spin-orbit coupling (by the atomic charge). Based on first-principle calculations we demonstrate that around 50 Heusler compounds show band inversion similar to that of HgTe. The topological state in these zero-gap semiconductors can be created by applying strain or by designing an appropriate quantum-well structure, similar to the case of HgTe. Many of these ternary zero-gap semiconductors (LnAuPb, LnPdBi, LnPtSb and LnPtBi) contain the rare-earth element Ln, which can realize additional properties ranging from superconductivity (for example LaPtBi; ref. 12) to magnetism (for example GdPtBi; ref. 13) and heavy fermion behaviour (for example YbPtBi; ref. 14). These properties can open new research directions in realizing the quantized anomalous Hall effect and topological superconductors.

Elliptic Flow of Charged Particles in Pb-Pb Collisions at root s(NN)=2.76 TeV

Abstract: We report the first measurement of charged particle elliptic flow in Pb-Pb collisions at root s(NN) p = 2.76 TeV with the ALICE detector at the CERN Large Hadron Collider. The measurement is performed in the central pseudorapidity region (vertical bar eta vertical bar < 0.8) and transverse momentum range 0.2 < p(t) < 5.0 GeV/c. The elliptic flow signal v(2), measured using the 4-particle correlation method, averaged over transverse momentum and pseudorapidity is 0.087 +/- 0.002(stat) +/- 0.003(syst) in the 40%-50% centrality class. The differential elliptic flow v(2)(p(t)) reaches a maximum of 0.2 near p(t) = 3 GeV/c. Compared to RHIC Au-Au collisions at root s(NN) = 200 GeV, the elliptic flow increases by about 30%. Some hydrodynamic model predictions which include viscous corrections are in agreement with the observed increase.

The uncertainty principle in the presence of quantum memory

Abstract: The Heisenberg uncertainty principle bounds the uncertainties about the outcomes of two incompatible measurements on a quantum particle. This bound, however, changes if a memory device is involved that stores quantum information. New work now extends the uncertainty principle to include the case of quantum memories, and should provide a guide for quantum information applications.

Monocular 3D pose estimation and tracking by detection

Abstract: Automatic recovery of 3D human pose from monocular image sequences is a challenging and important research topic with numerous applications. Although current methods are able to recover 3D pose for a single person in controlled environments, they are severely challenged by real-world scenarios, such as crowded street scenes. To address this problem, we propose a three-stage process building on a number of recent advances. The first stage obtains an initial estimate of the 2D articulation and viewpoint of the person from single frames. The second stage allows early data association across frames based on tracking-by-detection. These two stages successfully accumulate the available 2D image evidence into robust estimates of 2D limb positions over short image sequences (= tracklets). The third and final stage uses those tracklet-based estimates as robust image observations to reliably recover 3D pose. We demonstrate state-of-the-art performance on the HumanEva II benchmark, and also show the applicability of our approach to articulated 3D tracking in realistic street conditions.

γH2AX foci analysis for monitoring DNA double-strand break repair: strengths, limitations and optimization

Abstract: DNA double-strand breaks (DSBs) represent an important radiation-induced lesion and impaired DSB repair provides the best available correlation with radiosensitivity. Physical techniques for monitoring DSB repair require high, non-physiological doses and cannot reliably detect subtle defects. One outcome from extensive research into the DNA damage response is the observation that H2AX, a variant form of the histone H2A, undergoes extensive phosphorylation at the DSB, creating gammaH2AX foci that can be visualized by immunofluorescence. There is a close correlation between gammaH2AX foci and DSB numbers and between the rate of foci loss and DSB repair, providing a sensitive assay to monitor DSB repair in individual cells using physiological doses. However, gammaH2AX formation can occur at single-stranded DNA regions which arise during replication or repair and thus does not solely correlate with DSB formation. Here, we present and discuss evidence that following exposure to ionizing radiation, gammaH2AX foci analysis can provide a sensitive monitor of DSB formation and repair and describe techniques to optimize the analysis. We discuss the limitations and benefits of the technique, enabling the procedure to be optimally exploited but not misused.

The ALICE TPC, a large 3-dimensional tracking device with fast readout for ultra-high multiplicity events

Abstract: The design, construction, and commissioning of the ALICE Time-Projection Chamber (TPC) is described. It is the main device for pattern recognition, tracking, and identification of charged particles in the ALICE experiment at the CERN LHC. The TPC is cylindrical in shape with a volume close to 90 m(3) and is operated in a 0.5T solenoidal magnetic field parallel to its axis. In this paper we describe in detail the design considerations for this detector for operation in the extreme multiplicity environment of central Pb-Pb collisions at LHC energy. The implementation of the resulting requirements into hardware (field cage, read-out chambers, electronics), infrastructure (gas and cooling system, laser-calibration system), and software led to many technical innovations which are described along with a presentation of all the major components of the detector, as currently realized. We also report on the performance achieved after completion of the first round of stand-alone calibration runs and demonstrate results close to those specified in the TPC Technical Design Report. (C) 2010 CERN for the benefit of the ALICE collaboration. Published by Elsevier B.V. All rights reserved. (Less)

New features and insights for pedestrian detection

Abstract: Despite impressive progress in people detection the performance on challenging datasets like Caltech Pedestrians or TUD-Brussels is still unsatisfactory. In this work we show that motion features derived from optic flow yield substantial improvements on image sequences, if implemented correctly — even in the case of low-quality video and consequently degraded flow fields. Furthermore, we introduce a new feature, self-similarity on color channels, which consistently improves detection performance both for static images and for video sequences, across different datasets. In combination with HOG, these two features outperform the state-of-the-art by up to 20%. Finally, we report two insights concerning detector evaluations, which apply to classifier-based object detection in general. First, we show that a commonly under-estimated detail of training, the number of bootstrapping rounds, has a drastic influence on the relative (and absolute) performance of different feature/classifier combinations. Second, we discuss important intricacies of detector evaluation and show that current benchmarking protocols lack crucial details, which can distort evaluations.

Modulation of protein properties in living cells using nanobodies

Abstract: Protein conformation is critically linked to function and often controlled by interactions with regulatory factors. Here we report the selection of camelid-derived single-domain antibodies (nanobodies) that modulate the conformation and spectral properties of the green fluorescent protein (GFP). One nanobody could reversibly reduce GFP fluorescence by a factor of 5, whereas its displacement by a second nanobody caused an increase by a factor of 10. Structural analysis of GFP-nanobody complexes revealed that the two nanobodies induce subtle opposing changes in the chromophore environment, leading to altered absorption properties. Unlike conventional antibodies, the small, stable nanobodies are functional in living cells. Nanobody-induced changes were detected by ratio imaging and used to monitor protein expression and subcellular localization as well as translocation events such as the tamoxifen-induced nuclear localization of estrogen receptor. This work demonstrates that protein conformations can be manipulated and studied with nanobodies in living cells.

Better Key Sizes (and Attacks) for LWE-Based Encryption.

Abstract: We analyze the concrete security and key sizes of theoretically sound lattice-based encryption schemes based on the “learning with errors” (LWE) problem. Our main contributions are: (1) a new lattice attack on LWE that combines basis reduction with an enumeration algorithm admitting a time/success tradeoff, which performs better than the simple distinguishing attack considered in prior analyses; (2) concrete parameters and security estimates for an LWE-based cryptosystem that is more compact and efficient than the well-known schemes from the literature. Our new key sizes are up to 10 times smaller than prior examples, while providing even stronger concrete security levels.

Extracting Opinion Targets in a Single and Cross-Domain Setting with Conditional Random Fields

Abstract: In this paper, we focus on the opinion target extraction as part of the opinion mining task. We model the problem as an information extraction task, which we address based on Conditional Random Fields (CRF). As a baseline we employ the supervised algorithm by Zhuang et al. (2006), which represents the state-of-the-art on the employed data. We evaluate the algorithms comprehensively on datasets from four different domains annotated with individual opinion target instances on a sentence level. Furthermore, we investigate the performance of our CRF-based approach and the baseline in a single- and cross-domain opinion target extraction setting. Our CRF-based approach improves the performance by 0.077, 0.126, 0.071 and 0.178 regarding F-Measure in the single-domain extraction in the four domains. In the cross-domain setting our approach improves the performance by 0.409, 0.242, 0.294 and 0.343 regarding F-Measure over the baseline.

Privilege escalation attacks on android

Abstract: Android is a modern and popular software platform for smartphones. Among its predominant features is an advanced security model which is based on application-oriented mandatory access control and sandboxing. This allows developers and users to restrict the execution of an application to the privileges it has (mandatorily) assigned at installation time. The exploitation of vulnerabilities in program code is hence believed to be confined within the privilege boundaries of an application's sandbox. However, in this paper we show that a privilege escalation attack is possible. We show that a genuine application exploited at runtime or a malicious application can escalate granted permissions. Our results immediately imply that Android's security model cannot deal with a transitive permission usage attack and Android's sandbox model fails as a last resort against malware and sophisticated runtime attacks.

Mutations in GRIN2A and GRIN2B encoding regulatory subunits of NMDA receptors cause variable neurodevelopmental phenotypes.

Abstract: N-methyl-D-aspartate (NMDA) receptors mediate excitatory neurotransmission in the mammalian brain. Two glycine-binding NR1 subunits and two glutamate-binding NR2 subunits each form highly Ca²(+)-permeable cation channels which are blocked by extracellular Mg²(+) in a voltage-dependent manner. Either GRIN2B or GRIN2A, encoding the NMDA receptor subunits NR2B and NR2A, was found to be disrupted by chromosome translocation breakpoints in individuals with mental retardation and/or epilepsy. Sequencing of GRIN2B in 468 individuals with mental retardation revealed four de novo mutations: a frameshift, a missense and two splice-site mutations. In another cohort of 127 individuals with idiopathic epilepsy and/or mental retardation, we discovered a GRIN2A nonsense mutation in a three-generation family. In a girl with early-onset epileptic encephalopathy, we identified the de novo GRIN2A mutation c.1845C>A predicting the amino acid substitution p.N615K. Analysis of NR1-NR2A(N615K) (NR2A subunit with the p.N615K alteration) receptor currents revealed a loss of the Mg²(+) block and a decrease in Ca²(+) permeability. Our findings suggest that disturbances in the neuronal electrophysiological balance during development result in variable neurological phenotypes depending on which NR2 subunit of NMDA receptors is affected.

Plant diversity effects on soil microorganisms support the singular hypothesis.

Abstract: The global decline in biodiversity has generated concern over the consequences for ecosystem functioning and services. Although ecosystem functions driven by soil microorganisms such as plant productivity, decomposition, and nutrient cycling are of particular importance, interrelationships between plant diversity and soil microorganisms are poorly understood. We analyzed the response of soil microorganisms to variations in plant species richness (1-60) and plant functional group richness (1-4) in an experimental grassland system over a period of six years. Major abiotic and biotic factors were considered for exploring the mechanisms responsible for diversity effects. Further, microbial growth characteristics were assessed following the addition of macronutrients. Effects of plant diversity on soil microorganisms were most pronounced in the most diverse plant communities though differences only became established after a time lag of four years. Differences in microbial growth characteristics indicate successional changes from a disturbed (zymogeneous) to an established (autochthonous) microbial community four years after establishment of the experiment. Supporting the singular hypothesis for plant diversity, the results suggest that plant species are unique, each contributing to the functioning of the belowground system. The results reinforce the need for long-term biodiversity experiments to fully appreciate consequences of current biodiversity loss for ecosystem functioning.

Transparent Conducting Oxides for Photovoltaics: Manipulation of Fermi Level, Work Function and Energy Band Alignment

Abstract: Doping limits, band gaps, work functions and energy band alignments of undoped and donor-doped transparent conducting oxides Zn0, In2O3, and SnO2 as accessed by X-ray and ultraviolet photoelectron spectroscopy (XPS/UPS) are summarized and compared. The presented collection provides an extensive data set of technologically relevant electronic properties of photovoltaic transparent electrode materials and illustrates how these relate to the underlying defect chemistry, the dependence of surface dipoles on crystallographic orientation and/or surface termination, and Fermi level pinning.

A Monolingual Tree-based Translation Model for Sentence Simplification

Abstract: In this paper, we consider sentence simplification as a special form of translation with the complex sentence as the source and the simple sentence as the target. We propose a Tree-based Simplification Model (TSM), which, to our knowledge, is the first statistical simplification model covering splitting, dropping, reordering and substitution integrally. We also describe an efficient method to train our model with a large-scale parallel dataset obtained from the Wikipedia and Simple Wikipedia. The evaluation shows that our model achieves better readability scores than a set of baseline systems.

What helps where – and why? Semantic relatedness for knowledge transfer

Abstract: Remarkable performance has been reported to recognize single object classes. Scalability to large numbers of classes however remains an important challenge for today's recognition methods. Several authors have promoted knowledge transfer between classes as a key ingredient to address this challenge. However, in previous work the decision which knowledge to transfer has required either manual supervision or at least a few training examples limiting the scalability of these approaches. In this work we explicitly address the question of how to automatically decide which information to transfer between classes without the need of any human intervention. For this we tap into linguistic knowledge bases to provide the semantic link between sources (what) and targets (where) of knowledge transfer. We provide a rigorous experimental evaluation of different knowledge bases and state-of-the-art techniques from Natural Language Processing which goes far beyond the limited use of language in related work. We also give insights into the applicability (why) of different knowledge sources and similarity measures for knowledge transfer.

53BP1-dependent robust localized KAP-1 phosphorylation is essential for heterochromatic DNA double-strand break repair

Abstract: DNA double-strand breaks (DSBs) trigger ATM (ataxia telangiectasia mutated) signalling and elicit genomic rearrangements and chromosomal fragmentation if misrepaired or unrepaired. Although most DSB repair is ATM-independent, ~15% of ionizing radiation (IR)-induced breaks persist in the absence of ATM-signalling1. 53BP1 (p53-binding protein 1) facilitates ATM-dependent DSB repair but is largely dispensable for ATM activation or checkpoint arrest. ATM promotes DSB repair within heterochromatin by phosphorylating KAP-1 (KRAB-associated protein 1, also known as TIF1β, TRIM28 or KRIP-1; ref. 2). Here, we show that the ATM signalling mediator proteins MDC1, RNF8, RNF168 and 53BP1 are also required for heterochromatic DSB repair. Although KAP-1 phosphorylation is critical for 53BP1-mediated repair, overall phosphorylated KAP-1 (pKAP-1) levels are only modestly affected by 53BP1 loss. pKAP-1 is transiently pan-nuclear but also forms foci overlapping with γH2AX in heterochromatin. Cells that do not form 53BP1 foci, including human RIDDLE (radiosensitivity, immunodeficiency, dysmorphic features and learning difficulties) syndrome cells, fail to form pKAP-1 foci. 53BP1 amplifies Mre11–NBS1 accumulation at late-repairing DSBs, concentrating active ATM and leading to robust, localized pKAP-1. We propose that ionizing-radiation induced foci (IRIF) spatially concentrate ATM activity to promote localized alterations in regions of chromatin otherwise inhibitory to repair.

Constraints on Neutron Star Radii Based on Chiral Effective Field Theory Interactions

Abstract: We show that microscopic calculations based on chiral effective field theory interactions constrain the properties of neutron-rich matter below nuclear densities to a much higher degree than is reflected in commonly used equations of state. Combined with observed neutron star masses, our results lead to a radius $R=9.7--13.9\text{ }\text{ }\mathrm{km}$ for a $1.4{M}_{\ensuremath{\bigodot}}$ star, where the theoretical range is due, in about equal amounts, to uncertainties in many-body forces and to the extrapolation to high densities.

Carbohydrates as Organic Raw Materials

Abstract: In view of the impending transition of chemical industry from depleting fossil raw materials to renewable feedstocks — the end of cheap oil is predicted around 2040 — this account gives an overview on chemically and enzymatically transforming carbohydrates, by far the major part of the annually regrowing biomass, into products with versatile industrial application profiles and the potential to eventually replace those presently derived from petrochemical sources. The article contains sections titled: 1. Introduction 2. Availability of Carbohydrates 3. Current Nonfood Industrial Products from Sugars 3.1. Ethanol 3.2. Furfural 3.3 d-Sorbitol 3.4 Lactic Acid and Polylactic Acid (PLA) 3.5. Sugar-Based Surfactants 3.5.1. ‘Sorbitan’ Esters 3.5.2. N-Methyl-N-acyl-glucamides (NMCA) 3.5.3. Alkylpolyglucosides (APG) 3.5.4. Sucrose Fatty Acid Monoesters 3.6. Pharmaceuticals and Vitamins 4. Toward Further Sugar-based Chemicals: Potential Development Lines 4.1. Furan Compounds 4.1.1. 5-Hydroxymethylfurfural (HMF) 4.1.2. 2,5-Dimethylfuran (DMF) 4.1.3. Furans with a Tetrahydroxybutyl Side Chain 4.2. Dihydropyrones 4.3. Sugar-Derived Unsaturated Nitrogen Heterocycles 4.3.1. Pyrroles 4.3.2. Pyrazoles 4.3.3. Imidazoles 4.3.4. 3-Pyridinols 4.4. Toward Sugar-Based Aromatic Chemicals 4.5. Microbial Conversion of Six-Carbon-Sugars into Simple Carboxylic Acids and Alcohols 4.5.1. Carboxylic Acids 4.5.2. Potential Sugar-Based Alcohol Commodities by Microbial Conversions 4.6. Chemical Conversion of Sugars into Carboxylic Acids 4.7. Biopolymers from Polymerizable Sugar Derivatives 4.7.1. Synthetic Biopolyesters 4.7.2. Microbial Polyesters 4.7.3. Polyamides 5. Outlook 6. References

Sterically demanding trialkylphosphines for palladium-catalyzed cross coupling reactions—alternatives to PtBu3

Abstract: The strong electron-donation and the steric bulk of trialkylphosphines renders them as very useful ligands for palladium-catalyzed cross coupling reactions. This critical review reports on the synthesis of two families of trialkylphosphines (diadamantylalkylphosphines, fluorenyldialkylphosphines) and the properties of the respective palladium complexes in various cross coupling reactions, which evolved as alternatives to the classical Pd/PtBu3 system. In contrast to the latter phosphine the new classes of ligands are characterized by a highly flexible ligand design, which allows the fine tuning of catalytic properties to the specific needs of certain substrates and also enables the attachment of additional tags to impart certain useful properties onto the respective phosphines (179 references).

Chiral three-nucleon forces and neutron matter

Abstract: We calculate the properties of neutron matter and highlight the physics of chiral three-nucleon forces. For neutrons, only the long-range $2\ensuremath{\pi}$-exchange interactions of the leading chiral three-nucleon forces contribute, and we derive density-dependent two-body interactions by summing the third particle over occupied states in the Fermi sea. Our results for the energy suggest that neutron matter is perturbative at nuclear densities. We study in detail the theoretical uncertainties of the neutron matter energy, provide constraints for the symmetry energy and its density dependence, and explore the impact of chiral three-nucleon forces on the $S$-wave superfluid pairing gap.