Showing papers by "Leibniz University of Hanover published in 2012"

Functions of Macronutrients

Abstract: Publisher Summary This chapter focuses on the role played by various macronutrients such as nitrogen (N), sulfur (S), phosphorus (P), magnesium (Mg), calcium (Ca), and potassium (K) in plant metabolism and growth and describes the symptoms of deficiency and toxicity of these macronutrients. N is the most essential element required after carbon, and it plays a central role in plant metabolism as a constituent of proteins, nucleic acids, chlorophyll, coenzymes, phytohormones, and secondary metabolites. When it is taken as ammonium or nitrate, it is assimilated into amino acids either in the roots or shoots and within the plant, it is translocated as nitrate or amino acids. Sulfur is taken up as sulphate and assimilated into S-containing amino acids such as cysteine that are used to synthesize S-containing enzymes and coenzymes as well as secondary compounds such as phytochelatins (detoxification of metals) or aliins and glucosinolates (feeding deterrents). Phosphorus is a structural element in nucleic acids, and as a component of adenosine phosphates, it plays an important role in energy transfer, and it is also essential for transfer of carbohydrates in leaf cells. Magnesium is a component of chlorophyll, and it is required for photosynthesis and protein synthesis. Calcium is important for cell wall and membrane stabilization, osmoregulation, and as second messenger, thereby allowing plants to regulate developmental processes in response to environmental stimuli. The main role of K is osmoregulation, which is important for cell extension and stomata movement, and it affects loading of sucrose and the rate of mass flow-driven solute movement within the plant.

Why eve and mallory love android: an analysis of android SSL (in)security

Abstract: Many Android apps have a legitimate need to communicate over the Internet and are then responsible for protecting potentially sensitive data during transit. This paper seeks to better understand the potential security threats posed by benign Android apps that use the SSL/TLS protocols to protect data they transmit. Since the lack of visual security indicators for SSL/TLS usage and the inadequate use of SSL/TLS can be exploited to launch Man-in-the-Middle (MITM) attacks, an analysis of 13,500 popular free apps downloaded from Google's Play Market is presented. We introduce MalloDroid, a tool to detect potential vulnerability against MITM attacks. Our analysis revealed that 1,074 (8.0%) of the apps examined contain SSL/TLS code that is potentially vulnerable to MITM attacks. Various forms of SSL/TLS misuse were discovered during a further manual audit of 100 selected apps that allowed us to successfully launch MITM attacks against 41 apps and gather a large variety of sensitive data. Furthermore, an online survey was conducted to evaluate users' perceptions of certificate warnings and HTTPS visual security indicators in Android's browser, showing that half of the 754 participating users were not able to correctly judge whether their browser session was protected by SSL/TLS or not. We conclude by considering the implications of these findings and discuss several countermeasures with which these problems could be alleviated.

Carry Trades and Global Foreign Exchange Volatility

Abstract: We investigate the relation between global foreign exchange (FX) volatility risk and the cross-section of excess returns arising from popular strategies that borrow in low-interest rate currencies and invest in high-interest rate currencies, so-called `carry trades'. We find that high interest rate currencies are negatively related to innovations in global FX volatility and thus deliver low returns in times of unexpected high volatility, when low interest rate currencies provide a hedge by yielding positive returns. Our proxy for global FX volatility risk captures more than 90% of the cross-sectional excess returns in five carry trade portfolios. In turn, these results provide evidence that there is an economically meaningful risk-return relation in the FX market. Further analysis shows that liquidity risk also matters for expected FX returns, but to a lesser degree than volatility risk. Finally, exposure to our volatility risk proxy also performs well for pricing returns of other cross sections in foreign exchange, U.S. equity, and corporate bond markets.

Scientific objectives of Einstein Telescope

Abstract: The advanced interferometer network will herald a new era in observational astronomy. There is a very strong science case to go beyond the advanced detector network and build detectors that operate in a frequency range from 1 Hz to 10 kHz, with sensitivity a factor 10 better in amplitude. Such detectors will be able to probe a range of topics in nuclear physics, astronomy, cosmology and fundamental physics, providing insights into many unsolved problems in these areas.

An International Comparison of Individual Tree Detection and Extraction Using Airborne Laser Scanning

Abstract: The objective of the “Tree Extraction” project organized by EuroSDR (European Spatial data Research) and ISPRS (International Society of Photogrammetry and Remote Sensing) was to evaluate the quality, accuracy, and feasibility of automatic tree extraction methods, mainly based on laser scanner data. In the final report of the project, Kaartinen and Hyyppa (2008) reported a high variation in the quality of the published methods under boreal forest conditions and with varying laser point densities. This paper summarizes the findings beyond the final report after analyzing the results obtained in different tree height classes. Omission/Commission statistics as well as neighborhood relations are taken into account. Additionally, four automatic tree detection and extraction techniques were added to the test. Several methods in this experiment were superior to manual processing in the dominant, co-dominant and suppressed tree storeys. In general, as expected, the taller the tree, the better the location accuracy. The accuracy of tree height, after removing gross errors, was better than 0.5 m in all tree height classes with the best methods investigated in this experiment. For forest inventory, minimum curvature-based tree detection accompanied by point cloud-based cluster detection for suppressed trees is a solution that deserves attention in the future.

The ISPRS benchmark on urban object classification and 3D building reconstruction

Abstract: . For more than two decades, many efforts have been made to develop methods for extracting urban objects from data acquired by airborne sensors. In order to make the results of such algorithms more comparable, benchmarking data sets are of paramount importance. Such a data set, consisting of airborne image and laserscanner data, has been made available to the scientific community. Researchers were encouraged to submit results of urban object detection and 3D building reconstruction, which were evaluated based on reference data. This paper presents the outcomes of the evaluation for building detection, tree detection, and 3D building reconstruction. The results achieved by different methods are compared and analysed to identify promising strategies for automatic urban object extraction from current airborne sensor data, but also common problems of state-of-the-art methods.

The transcriptome of the arbuscular mycorrhizal fungus Glomus intraradices (DAOM 197198) reveals functional tradeoffs in an obligate symbiont

Abstract: • The arbuscular mycorrhizal symbiosis is arguably the most ecologically important eukaryotic symbiosis, yet it is poorly understood at the molecular level. To provide novel insights into the molecular basis of symbiosis-associated traits, we report the first genome-wide analysis of the transcriptome from Glomus intraradices DAOM 197198. • We generated a set of 25,906 nonredundant virtual transcripts (NRVTs) transcribed in germinated spores, extraradical mycelium and symbiotic roots using Sanger and 454 sequencing. NRVTs were used to construct an oligoarray for investigating gene expression. • We identified transcripts coding for the meiotic recombination machinery, as well as meiosis-specific proteins, suggesting that the lack of a known sexual cycle in G. intraradices is not a result of major deletions of genes essential for sexual reproduction and meiosis. Induced expression of genes encoding membrane transporters and small secreted proteins in intraradical mycelium, together with the lack of expression of hydrolytic enzymes acting on plant cell wall polysaccharides, are all features of G. intraradices that are shared with ectomycorrhizal symbionts and obligate biotrophic pathogens. • Our results illuminate the genetic basis of symbiosis-related traits of the most ancient lineage of plant biotrophs, advancing future research on these agriculturally and ecologically important symbionts.

Observation of one-way Einstein–Podolsky–Rosen steering

Abstract: Recent theory predicts that Einstein–Podolsky–Rosen arguments enable an effect in which one party can steer the other but not the converse. Researchers have now demonstrated this one-way steering effect with two entangled Gaussian modes of light, potentially opening up a new field of applications in quantum information.

Meta-Synthesis of Qualitative Case Studies An Approach to Theory Building

Abstract: The purpose of this article is to provide the research design of a meta-synthesis of qualitative case studies. The meta-synthesis aims at building theory out of primary qualitative case studies that have not been planned as part of a unified multisite effect. By drawing on an understanding of research synthesis as the interpretation of qualitative evidence from a postpositivistic perspective, this article proposes eight steps of synthesizing existing qualitative case study findings to build theory. An illustration of the application of this method in the field of dynamic capabilities is provided. After enumerating the options available to meta-synthesis researchers, the potential challenges as well as the prospects of this research design are discussed.

Formate modulated solvothermal synthesis of ZIF-8 investigated using time-resolved in situ X-ray diffraction and scanning electron microscopy

Abstract: Time-resolved investigations using in situ energy-dispersive X-ray diffraction in tandem with ex situscanning electron microscopy revealed that solvothermal crystallisation of ZIF-8 in methanol solvent and in the presence of sodium formate as a simple monodentate ligand (modulator) is a rapid process yielding big, high-quality single crystals in short time (<4 h). Kinetic analysis of crystallisation curves was performed by applying the Avrami–Erofe'ev and Gualtieri models. The analyses revealed that the weakly basic formate modulator acts as a base in deprotonation equilibria (deprotonation of the bridging 2-methylimidazole ligand) rather than as a competitive ligand in coordination equilibria at the metal (Zn2+) centres. This is in contrast to the coordination modulation function of formate in ZIF-8 synthesis at room temperature. Crystal shape evolves with time in the presence of formate from cubes with truncated edges to rhombic dodecahedra. The latter shape represents most likely the stable equilibrium morphology of ZIF-8.

Continuous variable quantum key distribution: finite-key analysis of composable security against coherent attacks.

Abstract: We provide a security analysis for continuous variable quantum key distribution protocols based on the transmission of two-mode squeezed vacuum states measured via homodyne detection. We employ a version of the entropic uncertainty relation for smooth entropies to give a lower bound on the number of secret bits which can be extracted from a finite number of runs of the protocol. This bound is valid under general coherent attacks, and gives rise to keys which are composably secure. For comparison, we also give a lower bound valid under the assumption of collective attacks. For both scenarios, we find positive key rates using experimental parameters reachable today.

19%‐efficient and 43 µm‐thick crystalline Si solar cell from layer transfer using porous silicon

Abstract: We present a both-sides-contacted thin-film crystalline silicon (c-Si) solar cell with a confirmed AM1.5 efficiency of 19.1% using the porous silicon layer transfer process. The aperture area of the cell is 3.98 cm2. This is the highest efficiency ever reported for transferred Si cells. The efficiency improvement over the prior state of the art (16.9%) is achieved by implementing recent developments for Si wafer cells such as surface passivation with aluminum oxide and laser ablation for contacting. The cell has a short-circuit current density of 37.8 mA cm−2, an open-circuit voltage of 650 mV, and a fill factor of 77.6%. Copyright © 2011 John Wiley & Sons, Ltd.

Kinetics and mechanisms of charge transfer processes in photocatalytic systems: A review

Abstract: Charge carrier transfer processes are very important and play a vital role in photocatalytic reactions. A fundamental understanding of the kinetics and mechanisms of these charge transfer processes is crucial from the viewpoint of developing efficient photocatalysis systems for large-scale industrialization. In this work, recent efforts concerning the understanding of the kinetics and the mechanisms of the charge transfer in photocatalytic processes have been reviewed. Fundamental aspects involved in these charge transfer processes, such as charge generation, charge trapping, charge recombination, and electron and hole transfer are primarily discussed. Moreover, some recent studies focusing on enhancing the photocatalytic efficiency by improving the charge transfer and separation are also reviewed.

Intralymphatic immunotherapy for cat allergy induces tolerance after only 3 injections

Abstract: Background Subcutaneous allergen-specific immunotherapy frequently causes allergic side effects and requires 30 to 80 injections over 3 to 5 years. Objective We sought to improve immunotherapy by using intralymphatic allergen administration (intralymphatic immunotherapy [ILIT]) and by targeting allergen to the MHC class II pathway. Methods Recombinant major cat dander allergen Fel d 1 was fused to a translocation sequence (TAT) and to part of the human invariant chain, generating a modular antigen transporter (MAT) vaccine (MAT–Fel d 1). In a randomized double-blind trial ILIT with MAT–Fel d 1 in alum was compared with ILIT with placebo (saline in alum) in allergic patients (ClinicalTrials.gov NCT00718679). Results ILIT with MAT–Fel d 1 elicited no adverse events. After 3 placebo injections within 2 months, nasal tolerance increased less than 3-fold, whereas 3 intralymphatic injections with MAT–Fel d 1 increased nasal tolerance 74-fold ( P P = .026 vs placebo) and increased cat dander–specific IgG 4 levels by 5.66-fold ( P = .003). The IgG 4 response positively correlated with IL-10 production ( P Conclusion In a first-in-human clinical study ILIT with MAT–Fel d 1 was safe and induced allergen tolerance after 3 injections.

A hybrid approach for efficient Web service composition with end-to-end QoS constraints

Abstract: Dynamic selection of Web services at runtime is important for building flexible and loosely-coupled service-oriented applications. An abstract description of the required services is provided at design-time, and matching service offers are located at runtime. With the growing number of Web services that provide the same functionality but differ in quality parameters (e.g., availability, response time), a decision needs to be made on which services should be selected such that the user's end-to-end QoS requirements are satisfied. Although very efficient, local selection strategy fails short in handling global QoS requirements. Solutions based on global optimization, on the other hand, can handle global constraints, but their poor performance renders them inappropriate for applications with dynamic and realtime requirements. In this article we address this problem and propose a hybrid solution that combines global optimization with local selection techniques to benefit from the advantages of both worlds. The proposed solution consists of two steps: first, we use mixed integer programming (MIP) to find the optimal decomposition of global QoS constraints into local constraints. Second, we use distributed local selection to find the best Web services that satisfy these local constraints. The results of experimental evaluation indicate that our approach significantly outperforms existing solutions in terms of computation time while achieving close-to-optimal results.

Search for gravitational waves from low mass compact binary coalescence in LIGO's sixth science run and Virgo's science runs 2 and 3

Abstract: We report on a search for gravitational waves from coalescing compact binaries using LIGO and Virgo observations between July 7, 2009, and October 20, 2010. We searched for signals from binaries with total mass between 2 and 25M(circle dot); this includes binary neutron stars, binary black holes, and binaries consisting of a black hole and neutron star. The detectors were sensitive to systems up to 40 Mpc distant for binary neutron stars, and further for higher mass systems. No gravitational-wave signals were detected. We report upper limits on the rate of compact binary coalescence as a function of total mass, including the results from previous LIGO and Virgo observations. The cumulative 90% confidence rate upper limits of the binary coalescence of binary neutron star, neutron star-black hole, and binary black hole systems are 1.3 x 10(-4), 3.1 x 10(-5), and 6.4 x 10(-6) Mpc(-3) yr(-1), respectively. These upper limits are up to a factor 1.4 lower than previously derived limits. We also report on results from a blind injection challenge.

The Model of Educational Reconstruction A Framework for improving teaching and learning science

Abstract: To improve instructional practices – in schools, universities and in out of school settings has been a major concern of science education research and development. The intensive international debate on scientific literacy in the 1990s and the series of international monitoring studies like TIMSS and PISA in the 1990s and in the 2000s have fuelled this debate substantially. Various strands of science education research contribute to the stock of knowledge on more efficient means of teaching and learning science. The Model of Educational Reconstruction (MER) presented in this chapter provides a conception of science education research that is relevant for improving instructional practice and teacher professional development programs. The model is based on European Didaktik and Bildung (formation) traditions – with a particular emphasis on the German tradition. A key concern of the model is that science subject matter issues as well as student learning needs and capabilities have to be given equal attention in attempts to improve the quality of teaching and learning

Tunable ion-photon entanglement in an optical cavity

Abstract: Proposed quantum networks require both a quantum interface between light and matter and the coherent control of quantum states. A quantum interface can be realized by entangling the state of a single photon with the state of an atomic or solid-state quantum memory, as demonstrated in recent experiments with trapped ions, neutral atoms, atomic ensembles and nitrogen-vacancy spins. The entangling interaction couples an initial quantum memory state to two possible light-matter states, and the atomic level structure of the memory determines the available coupling paths. In previous work, the transition parameters of these paths determined the phase and amplitude of the final entangled state, unless the memory was initially prepared in a superposition state (a step that requires coherent control). Here we report fully tunable entanglement between a single (40)Ca(+) ion and the polarization state of a single photon within an optical resonator. Our method, based on a bichromatic, cavity-mediated Raman transition, allows us to select two coupling paths and adjust their relative phase and amplitude. The cavity setting enables intrinsically deterministic, high-fidelity generation of any two-qubit entangled state. This approach is applicable to a broad range of candidate systems and thus is a promising method for distributing information within quantum networks.

Photo-induced hydrophilicity and self-cleaning: models and reality

Abstract: Self-cleaning coatings, with benefits to environment, energy and labor saving, have attracted great attention due to their potential application in many aspects of human's daily life. In this perspective article, the recent efforts to understand and improve photo-induced hydrophilicity and self-cleaning properties of TiO2 are reviewed. Particular attention is paid to the fundamental aspects and mechanism of the photo-induced hydrophilicity effect. The challenges that need to be addressed over the coming years to improve the efficiency and extend the application are also presented.

Effect of grazing on carbon stocks and assimilate partitioning in a Tibetan montane pasture revealed by 13CO2 pulse labeling

Abstract: Since the late 1950s, governmental rangeland policies have changed the grazing management on the Tibetan Plateau (TP). Increasing grazing pressure and, since the 1980s, the privatization and fencing of pastures near villages has led to land degradation, whereas remote pastures have recovered from stronger overgrazing. To clarify the effect of moderate grazing on the carbon (C) cycle of the TP, we investigated differences in below-ground C stocks and C allocation using in situ 13CO2 pulse labeling of (i) a montane Kobresia winter pasture of yaks, with moderate grazing regime and (ii) a 7-year-old grazing exclosure plot, both in 3440 m asl. Twenty-seven days after the labeling, 13C incorporated into shoots did not differ between the grazed (43% of recovered 13C) and ungrazed (38%) plots. In the grazed plots, however, less C was lost by shoot respiration (17% vs. 42%), and more was translocated below-ground (40% vs. 20%). Within the below-ground pools, <2% of 13C was incorporated into living root tissue of both land use types. In the grazed plots about twice the amount of 13C remained in soil (18%) and was mineralized to CO2 (20%) as compared to the ungrazed plots (soil 10%; CO2 9%). Despite the higher contribution of root-derived C to CO2 efflux, total CO2 efflux did not differ between the two land use types. C stocks in the soil layers 05 and 515 cm under grazed grassland were significantly larger than in the ungrazed grassland. However, C stocks below 15 cm were not affected after 7 years without grazing. We conclude that the larger below-ground C allocation of plants, the larger amount of recently assimilated C remaining in the soil, and less soil organic matter-derived CO2 efflux create a positive effect of moderate grazing on soil C input and C sequestration.

Adaptation of Plants to Adverse Chemical Soil Conditions

Abstract: Publisher Summary This chapter focuses on the various constraints faced by plants in adverse soil conditions such as acidity, poor aeration, alkalinity, and salinity. The low-external input high-efficiency involving adapted genotypes that efficiently uses the nutrients from soil reserves and fertilizer can lead to yields that are only 10–20% below the maximum. Two components that contribute to overall nutrient efficiency include uptake efficiency, which is the amount of nutrient absorbed, and utilization efficiency, which characterizes the efficiency with which the absorbed nutrients are utilized to produce yield. Both of them primarily depend on the nutrient supply by the soil and fertilizers. The main constraints to plant growth in flooded or submerged soils are the low oxygen availability, Fe and Mn toxicity and toxic metabolites of anaerobic decomposition. Adaptation to flooded soils includes aerenchyma formation to transport oxygen to the roots, efficient generation and use of energy and carbohydrate conservation. Plant growth in alkaline or calcareous soils is inhibited by low availability of Fe, Zn, Mn and B and tolerance to such soils is achieved by mobilization of Fe and Zn via exudation of chelating compounds such as organic acid anions in Strategy I plants and phytosiderophores in Strategy II plants. The main constraints to plant growth in saline soils are low osmotic potential and ion toxicity (Na, Cl, sulphate) as well as ion imbalances (low K/Na ratio). The salt tolerance mechanisms can be divided into salt exclusion (reduced uptake, increased efflux) and salt inclusion (compartmentation into the vacuole, release of salts via salt glands, and salt-tolerant enzymes).