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Showing papers by "Leibniz University of Hanover published in 2008"


Journal ArticleDOI
TL;DR: In this article, the properties of entanglement in many-body systems are reviewed and both bipartite and multipartite entanglements are considered, and the zero and finite temperature properties of entangled states in interacting spin, fermion and boson model systems are discussed.
Abstract: Recent interest in aspects common to quantum information and condensed matter has prompted a flurry of activity at the border of these disciplines that were far distant until a few years ago. Numerous interesting questions have been addressed so far. Here an important part of this field, the properties of the entanglement in many-body systems, are reviewed. The zero and finite temperature properties of entanglement in interacting spin, fermion, and boson model systems are discussed. Both bipartite and multipartite entanglement will be considered. In equilibrium entanglement is shown tightly connected to the characteristics of the phase diagram. The behavior of entanglement can be related, via certain witnesses, to thermodynamic quantities thus offering interesting possibilities for an experimental test. Out of equilibrium entangled states are generated and manipulated by means of many-body Hamiltonians.

3,096 citations


Journal ArticleDOI
TL;DR: Magnesium and its alloys have been investigated recently by many authors as a suitable biodegradable biomaterial as mentioned in this paper, and the latest achievements and comment on the selection and use, test methods and the approaches to develop and produce magnesium alloys that are intended to perform clinically with an appropriate host response.
Abstract: Biodegradable metals are breaking the current paradigm in biomaterial science to develop only corrosion resistant metals. In particular, metals which consist of trace elements existing in the human body are promising candidates for temporary implant materials. These implants would be temporarily needed to provide mechanical support during the healing process of the injured or pathological tissue. Magnesium and its alloys have been investigated recently by many authors as a suitable biodegradable biomaterial. In this investigative review we would like to summarize the latest achievements and comment on the selection and use, test methods and the approaches to develop and produce magnesium alloys that are intended to perform clinically with an appropriate host response.

1,569 citations


Journal ArticleDOI
TL;DR: The remarkable progress made in the preparation and characterization of zeolite membranes during the last few years has stimulated several industrial R&D projects exploiting the shape-selectivity of ZO membranes in mass separation as mentioned in this paper.

665 citations


Proceedings ArticleDOI
26 Oct 2008
TL;DR: This paper is the first to present an in-depth study of tagging behavior for very different kinds of resources and systems - Web pages, music, and images - and compares the results with anchor text characteristics, and provides statistics on tag distributions in all three tagging environments.
Abstract: Collaborative tagging has become an increasingly popular means for sharing and organizing Web resources, leading to a huge amount of user generated metadata. These tags represent quite a few different aspects of the resources they describe and it is not obvious whether and how these tags or subsets of them can be used for search. This paper is the first to present an in-depth study of tagging behavior for very different kinds of resources and systems - Web pages (Del.icio.us), music (Last.fm), and images (Flickr) - and compares the results with anchor text characteristics. We analyze and classify sample tags from these systems, to get an insight into what kinds of tags are used for different resources, and provide statistics on tag distributions in all three tagging environments. Since even relevant tags may not add new information to the search procedure, we also check overlap of tags with content, with metadata assigned by experts and from other sources. We discuss the potential of different kinds of tags for improving search, comparing them with user queries posted to search engines as well as through a user survey. The results are promising and provide more insight into both the use of different kinds of tags for improving search and possible extensions of tagging systems to support the creation of potentially search-relevant tags.

350 citations


Journal ArticleDOI
TL;DR: In this paper, a family of template waveforms is proposed to model the inspiral, merger, and ring-down stages of the coalescence of nonspinning binary black holes that follow quasicircular inspiral.
Abstract: Gravitational waveforms from the inspiral and ring-down stages of the binary black-hole coalescences can be modeled accurately by approximation/perturbation techniques in general relativity. Recent progress in numerical relativity has enabled us to model also the nonperturbative merger phase of the binary black-hole coalescence problem. This enables us to coherently search for all three stages of the coalescence of nonspinning binary black holes using a single template bank. Taking our motivation from these results, we propose a family of template waveforms which can model the inspiral, merger, and ring-down stages of the coalescence of nonspinning binary black holes that follow quasicircular inspiral. This two-dimensional template family is explicitly parametrized by the physical parameters of the binary. We show that the template family is not only effectual in detecting the signals from black-hole coalescences, but also faithful in estimating the parameters of the binary. We compare the sensitivity of a search (in the context of different ground-based interferometers) using all three stages of the black-hole coalescence with other template-based searches which look for individual stages separately. We find that the proposed search is significantly more sensitive than other template-based searches for a substantial mass range, potentially bringing about remarkable improvement in the event rate of ground-based interferometers. As part of this work, we also prescribe a general procedure to construct interpolated template banks using nonspinning black-hole waveforms produced by numerical relativity.

340 citations


Journal ArticleDOI
TL;DR: A major advantage of the developed evaporation model is that it does not refer to intrinsic details of the interface-capturing scheme, but relies on continuum-field quantities that can be computed by virtually any CFD approach.

286 citations


Journal ArticleDOI
TL;DR: The first comprehensive set of stable Cr isotope data for the major igneous silicate Earth reservoirs, Cr(III)-rich ores and minerals, and hydrothermal chromates were determined by MC-ICP-MS using a double spike technique as discussed by the authors.

278 citations


Journal ArticleDOI
TL;DR: In this article, the authors argue for the inclusion of an analysis of industry clusters when making decisions about global or local sourcing and support the view that resources which enable a firm to achieve sustainable competitive advantages can be located beyond its legal boundaries.

247 citations


Journal ArticleDOI
TL;DR: It is found that Web browsing is a rapid activity even for pages with substantial content, which calls for page designs that allow for cursory reading and characteristic usage patterns for different types of Web sites emphasize the need for more adaptive and customizable Web browsers.
Abstract: In the past decade, the World Wide Web has been subject to dramatic changes. Web sites have evolved from static information resources to dynamic and interactive applications that are used for a broad scope of activities on a daily basis. To examine the consequences of these changes on user behavior, we conducted a long-term client-side Web usage study with twenty-five participants. This report presents results of this study and compares the user behavior with previous long-term browser usage studies, which range in age from seven to thirteen years. Based on the empirical data and the interview results, various implications for the interface design of browsers and Web sites are discussed.A major finding is the decreasing prominence of backtracking in Web navigation. This can largely be attributed to the increasing importance of dynamic, service-oriented Web sites. Users do not navigate on these sites searching for information, but rather interact with an online application to complete certain tasks. Furthermore, the usage of multiple windows and tabs has partly replaced back button usage, posing new challenges for user orientation and backtracking. We found that Web browsing is a rapid activity even for pages with substantial content, which calls for page designs that allow for cursory reading. Click maps provide additional information on how users interact with the Web on page level. Finally, substantial differences were observed between users, and characteristic usage patterns for different types of Web sites emphasize the need for more adaptive and customizable Web browsers.

244 citations


Journal ArticleDOI
TL;DR: In this paper, a multiscale aggregating discontinuity (MAD) method is proposed to compute an equivalent discontinuity at the coarser scale, including both the direction of the discontinuity and the magnitude of the jump.
Abstract: New methods for the analysis of failure by multiscale methods that invoke unit cells to obtain the subscale response are described. These methods, called multiscale aggregating discontinuities, are based on the concept of ‘perforated’ unit cells, which exclude subdomains that are unstable, i.e. exhibit loss of material stability. Using this concept, it is possible to compute an equivalent discontinuity at the coarser scale, including both the direction of the discontinuity and the magnitude of the jump. These variables are then passed to the coarse-scale model along with the stress in the unit cell. The discontinuity is injected at the coarser scale by the extended finite element method. Analysis of the procedure shows that the method is consistent in power and yields a bulk stress–strain response that is stable. Applications of this procedure to crack growth in heterogeneous materials are given. Copyright © 2007 John Wiley & Sons, Ltd.

236 citations


Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate that nearly dry melt inclusions from Galapagos Plateau basalt can gain up to 2.5 wt.% of water if they are placed for 2 days in a water-bearing melt at 200 MPa and 1140 °C.

Journal ArticleDOI
TL;DR: The results prove that impaired binding of TLR-ligands from the pathogenic S. aureus strain are not the cause for the inadequate mammary immune response elicited by this pathogen, and the pathogen causing subclinical mastitis impairs NF-kappaB activation in MEC thereby severely weakening the immune response in the udder.

Journal ArticleDOI
TL;DR: In this article, high-resolution urban large-eddy simulation (LES) studies are performed using the urban version of the parallelized LES model PALM, which is in line with experimental and previous LES results, i.e. superior to the faster/cheaper conventional Reynolds-averaged (RANS) models.

Journal ArticleDOI
TL;DR: In this article, a new deterministic approach is presented for determining the lower bound of the buckling load of thin-walled cylindrical composite shells, which is derived from phenomenological test data.
Abstract: Thin-walled shell structures like circular cylindrical shells are prone to buckling. Imperfections, which are defined as deviations from perfect shape and perfect loading distributions, can reduce the buckling load drastically compared to that of the perfect shell. Design criteria monographs like NASA-SP 8007 recommend that the buckling load of the perfect shell shall be reduced by using a knock-down factor. The existing knock-down factors are very conservative and do not account for the structural behaviour of composite shells. To determine an improved knock-down factor, several authors consider realistic shapes of shells in numerical simulations using probabilistic methods. Each manufacturing process causes a specific imperfection pattern; hence for this probabilistic approach a large number of test data is needed, which is often not available. Motivated by this lack of data, a new deterministic approach is presented for determining the lower bound of the buckling load of thin-walled cylindrical composite shells, which is derived from phenomenological test data. For the present test series, a single pre-buckle is induced by a radial perturbation load, before the axial displacement controlled loading starts. The deformations are measured using the prototype of a high-speed optical measurement system with a frequency up to 3680 Hz. The observed structural behaviour leads to a new reasonable lower bound of the buckling load. Based on test results, the numerical model is validated and the shell design is optimized by virtual testing. The results of test and numerical analysis indicate that this new approach has the potential to provide an improved and less conservative shell design in order to reduce weight and cost of thin-walled shell structures made from composite material.

Journal ArticleDOI
TL;DR: In this article, the impact of axial and tangential feed on process forces and borehole quality is shown, where the axial feed is used to generate boreholes by means of a milling tool being operated on a helical path into the workpiece.
Abstract: Helical milling is used to generate boreholes by means of a milling tool being operated on a helical path into the workpiece. The bore diameter can be adjusted through the diameter of the helical path. In comparison to conventional drilling operations this process often results in lower burr formation and fiber delamination. Therefore helical milling is used in the aircraft industry for cutting composites and composite-metal compounds. One of these compounds, which is regarded as difficult to machine, is a layer compound consisting of unidirectional carbon fiber reinforced plastic (CFRP) and TiAl6V4. This paper presents the impact of the axial and tangential feed during helical milling on process forces and borehole quality is shown.

Journal ArticleDOI
TL;DR: Hydrogen is gaining more and more attention because it is regarded as an important future fuel and recently several new processes, such as photovoltaic–photoelectrochemical water splitting and one-step or multistep thermochemical water splitting based on focused solar or nuclear heat, have been developed.
Abstract: Hydrogen is gaining more and more attention because it is regarded as an important future fuel. Today, hydrogen is mainly produced from nonrenewable natural gas and petroleum. With concerns over worldwide energy demands and global climate change, alternative sources must be found. Obviously, water is recommended as the ideal source for the generation of large amounts of hydrogen. In addition to electrolysis, recently several new processes, such as photovoltaic–photoelectrochemical water splitting and one-step or multistep thermochemical water splitting 6] based on focused solar or nuclear heat, have been developed. Although water dissociation into oxygen and hydrogen is conceptually simple [Eq. (1)], efficient hydrogen production

Book ChapterDOI
TL;DR: In this paper, the employment effects of job-creation schemes (JCS) on the participating individuals in Germany are evaluated and the overall results are rather discouraging, since employment effects are negative or insignificant for most of the analysed groups.
Abstract: In this chapter, we evaluate the employment effects of job-creation schemes (JCS) on the participating individuals in Germany. JCS are a major element of active labour market policy in Germany and are targeted at long-term unemployed and other hard-to-place individuals. Access to very informative administrative data of the Federal Employment Agency justifies the application of a matching estimator and allows us to account for individual (group-specific) and regional effect heterogeneity. We extend previous studies for Germany in four directions. First, we are able to evaluate the effects on regular (unsubsidised) employment. Second, we observe the outcomes of participants and non-participants for nearly three years after the programme starts and can therefore analyse medium-term effects. Third, we test the sensitivity of the results with respect to various decisions that have to be made during implementation of the matching estimator. Finally, we check if a possible occurrence of a specific form of ‘unobserved heterogeneity’ distorts our interpretation. The overall results are rather discouraging, since the employment effects are negative or insignificant for most of the analysed groups. One exception are long-term unemployed individuals who benefit from participation at the end of our observation period. Hence, one policy implication is to address the programmes to this problem group more closely.

Journal ArticleDOI
01 Aug 2008-Kyklos
TL;DR: In this paper, the authors analyzed survey responses of 649 fund managers in the U.S., Germany, Italy and Thailand, and found that female fund managers tend to behave as expected from gender studies: they are more risk averse and shy away from competition in the tournament scenario.
Abstract: SUMMARY There are robust gender differences in the domains of risk taking, overconfidence and competition behavior. However, as expertise tends to level these differences, we ask whether financial experts still show gender dissimilarities in their domains of decision making? We analyze survey responses of 649 fund managers in the U.S., Germany, Italy and Thailand, and find that female fund managers tend to behave as expected from gender studies: they are more risk averse and shy away from competition in the tournament scenario. The expected lower degree of overconfidence by women is yet so small that it becomes insignificant in fund management.

Journal ArticleDOI
B. P. Abbott1, Richard J. Abbott1, Rana X. Adhikari1, Juri Agresti1  +460 moreInstitutions (49)
TL;DR: In this paper, a search for gravitational waves from the coalescence of compact binary systems during the third and fourth LIGO science runs was reported, which focused on gravitational waves generated during the inspiral phase of the binary evolution.
Abstract: We report on a search for gravitational waves from the coalescence of compact binaries during the third and fourth LIGO science runs. The search focused on gravitational waves generated during the inspiral phase of the binary evolution. In our analysis, we considered three categories of compact binary systems, ordered by mass: (i) primordial black hole binaries with masses in the range 0.35M_⊙

Journal ArticleDOI
TL;DR: In this article, a model that explains the very long-run economic and demographic development path of industrialized economies, stretching from the pre-industrial era to the present-day and beyond, is presented.
Abstract: This paper provides a unified growth theory, i.e. a model that explains the very long-run economic and demographic development path of industrialized economies, stretching from the pre-industrial era to the present-day and beyond. Making strict use of Malthus’ (An essay on the principle of population. London, printed for J. Johnson, 1798) so-called preventive check hypothesis—that fertility rates vary inversely with the price of food—the current study offers a new and straightforward explanation for the demographic transition and the break with the Malthusian era. Employing a two-sector framework with agriculture and industry, we demonstrate how fertility responds differently to productivity and income growth, depending on whether it emerges in agriculture or industry. Agricultural productivity and income growth makes food goods, and therefore children, relatively less expensive. Industrial productivity and income growth, on the other hand, makes food goods, and therefore children, relatively more expensive. The present framework lends support to existing unified growth theories and is well in tune with historical evidence about structural transformation.

Journal ArticleDOI
TL;DR: In this article, the authors used a hydrous ferrobasalt as starting material, conducted at 200MPa, 940^12008C, at a wide range of water activities and redox conditions (QFM 3 to QFMþ 4, where QFM is the quartz^fayalite^magnetite oxygen buffer), and showed that the addition of H2O decreases liquidus temperatures and changes significantly the proportions, temperature range and sequence of crystallizing mineral phases.
Abstract: Crystallization experiments using a hydrous ferrobasalt as starting material, conducted at 200MPa, 940^12008C, at a wide range of water activities (0 1^1) and redox conditions (QFM 3 to QFMþ 4, where QFM is the quartz^fayalite^magnetite oxygen buffer), show that H2O influences significantly the differentiation history of ferrobasaltic magmas. A combination of our data with published experiments on dry ferrobasalt at 1atm provides an extensive experimental database for modeling and quantifying crystallization and differentiation processes within a typical Fe-rich tholeiitic system under both dry and hydrous conditions.The addition of H2O decreases liquidus temperatures and changes significantly the proportions, temperature range and sequence of crystallizing mineral phases. The dry liquidus is at about 11708C whereas the liquidus for H2O-saturated melts is at 10608C.The main phases crystallizing from H2O-bearing ferrobasalt at the investigated conditions are olivine (OL), clinopyroxene (CPX), plagioclase (PL), magnetite (MT), hematite (HM), ilmenite (ILM) and amphibole (AM). The phase assemblage is similar to that of the dry system except for the presence of HM at extremely oxidizing conditions and AM at low temperatures (59508C) and H2O-saturated conditions. The important observation made in this study is that the stability of Fe^Ti-oxides, and in particular MT, as well as the simultaneous coprecipitation of MTand ILM, are almost independent of the activity of H2O (aH2O) in the system, whereas the liquidus temperatures of the silicate minerals are dramatically depressed by increasing aH2O.The stabilities of oxides are controlled mainly by the redox conditions prevailing in the system.The most pronounced effect of aH2O on the liquidus temperatures of silicates is observed for PL, which shows a considerable delay in crystallization with progressive magma differentiation. Early crystallization of Fe^Ti-oxides in H2O-bearing ferrobasaltic compositions precludes any significant Fe enrichment during differentiation. As Fe enrichment is a characteristic feature of the Skaergaard intrusion, it implies that the Skaergaard parental magma did not contain considerable amounts of water. On the other hand, our experiments indicate that the differentiation of some ferrobasaltic series from the Columbia River flood basalt province might have occurred in magmatic systems containing significant amounts of volatiles ( 0 5^3 wt%H2O).

Journal ArticleDOI
TL;DR: It is demonstrated that hot particles can be ideally used inside a microfluidic fixed-bed reactor for performing chemical syntheses including catalytic transformations, and magnetic induction in an electromagnetic field is a third way to introduce thermal energy to a reactor.
Abstract: Interest in magnetic nanoparticles has increased considerably lately, with diverse applications as magnetic liquids, in catalysis, in biotechnology and biomedicine, and in magnetic resonance spectroscopy. A principal problem associated with naked metallic nanoparticles is their high chemical reactivity, in particular oxidation by air. This drawback can be overcome by coating the nanoparticles with SiO2, metal oxides, gold, or carbon. Several applications of these nanoparticles for quasi-homogeneous catalysis have been disclosed. These particles are typically removed after the reaction by exploiting their magnetic properties. An unexploited and very important feature of magnetic materials is the possibility of heating them in an electromagnetic field. It has been demonstrated that isolated magnetic nanoparticles show magnetic behavior different from that in the bulk. These magnetic nanoparticles when coated with a silica shell can show superparamagnetic behavior. The silica coating prevents the magnetic cores from coupling, thereby preserving their superparamagnetic properties. These composites do not have a residual magnetization and their magnetization curves are anhysteretic. However, the susceptibility of a superparamagnetic material is almost as high as that of a ferromagnetic material. The concept of magnetically induced hyperthermia is based on specific properties of the magnetic nanoparticles upon exposure to a constantly changing magnetic field. Surprisingly, this property of magnetic nanoparticles has so far not been applied in chemical synthesis, although organic chemists are constantly testing new technologies such as microwave irradiation, solid-phase synthesis, and new reactor designs in their work with the goal of performing syntheses and workups more efficiently. Herein we disclose the first application of heating magnetic silica-coated nanoparticles in an electromagnetic field. We demonstrate that these hot particles can be ideally used inside a microfluidic fixed-bed reactor for performing chemical syntheses including catalytic transformations. Thus, besides conventional and microwave heating, magnetic induction in an electromagnetic field is a third way to introduce thermal energy to a reactor. Superparamagnetic materials like nanoparticles 1 can be heated in mediumor high-frequency fields. As the technical setup for the middle-frequency field (25 kHz) is simpler (see Figure 1b,c), we investigated the electromagnetic induction of heat in magnetic nanoparticles in this frequency range. In principal, the processes can be operated in a cyclic or a continuous mode. The inductor can accommodate a flowthrough reactor (glass; 14 cm length, 9 mm internal diameter), which is filled with superparamagnetic material 1. The reactor can be operated up to a backup

Journal ArticleDOI
TL;DR: Zarei et al. as mentioned in this paper applied multidesign optimization (MDO) technique for optimizing the square rectangular tubes to find more efficient and lighter crush absorber and achieving maximum energy absorption.
Abstract: Axial impact crush tests on empty and foam-filled square aluminum tubes have been performed. Furthermore, in order to find more details about the crush processes, finite element simulations of the experiments have been done. In terms of finding more efficient and lighter crush absorber and achieving maximum energy absorption, multidesign optimization (MDO) technique has been applied for optimizing the square rectangular tubes. Based on practical requirements the optimum tube geometry, which absorbs maximum energy and has a minimum weight, has been determined. Results of previous work indicated that using high density honeycomb for filling the tubes will results more energy absorption but the weight efficiency has been lost [Zarei HR, Kroger M. Optimum honeycomb filled crash absorber design. Mater Des 2007;29:193–204]. Therefore, a comprehensive study has been performed in order to find out the crush behavior of tube filled with foam with different densities. The MDO procedure has been implemented to find an optimum filled tube that absorbed the same energy as an optimum empty tube can absorb.

Journal ArticleDOI
TL;DR: In this paper, the effect of organic matter (OM) quantity and OM quality on physical protection of soil is investigated. And the authors conclude that a higher hydrophobicity of the OM appears to stabilize the organic C in soil, either caused by a specific reduced biodegradability of OM or indirectly caused by increased aggregate stability.
Abstract: The protective impact of aggregation on microbial degradation through separation has been described frequently, especially for biotically formed aggregates. However, to date little information exists on the effects of organic-matter (OM) quantity and OM quality on physical protection, i.e., reduced degradability by microorganisms caused by physical factors. In the present paper, we hypothesize that soil wettability, which is significantly influenced by OM, may act as a key factor for OM stabilization as it controls the microbial accessibility for water, nutrients, and oxygen in three-phase systems like soil. Based on this hypothesis, the first objective is to evaluate new findings on the organization of organo-mineral complexes at the nanoscale as one of the processes creating water-repellent coatings on mineral surfaces. The second objective is to quantify the degree of alteration of coated surfaces with regard to water repellence. We introduce a recently developed trial that combines FTIR spectra with contact-angle data as the link between chemical composition of OM and the physical wetting behavior of soil particles. In addition to characterizing the wetting properties of OM coatings, we discuss the implications of water-repellent surfaces for different physical protection mechanisms of OM. For typical minerals, the OM loading on mineral surfaces is patchy, whereas OM forms nanoscaled micro-aggregates together with metal oxides and hydroxides and with layered clay minerals. Such small aggregates may efficiently stabilize OM against microbial decomposition. However, despite the patchy structure of OM coating, we observed a relation between the chemical composition of OM and wettability. A higher hydrophobicity of the OM appears to stabilize the organic C in soil, either caused by a specific reduced biodegradability of OM or indirectly caused by increased aggregate stability. In partly saturated nonaggregated soil, the specific distribution of the pore water appears to further affect the mineralization of OM as a function of wettability. We conclude that the wettability of OM, quantified by the contact angle, links the chemical structure of OM with a bundle of physical soil properties and that reduced wettability results in the stabilization of OM in soils.

Journal ArticleDOI
TL;DR: In this paper, a methodology is developed to use data acquisition derived from condition monitoring and standard diagnosis for rehabilitation purposes of transformers, where the interpretation and understanding of the test data are obtained from international test standards to determine the current condition of transformer.
Abstract: In this paper, a methodology is developed to use data acquisition derived from condition monitoring and standard diagnosis for rehabilitation purposes of transformers. The interpretation and understanding of the test data are obtained from international test standards to determine the current condition of transformers. In an attempt to ascertain monitoring priorities, the effective test methods are selected for transformer diagnosis. In particular, the standardization of diagnostic and analytical techniques are being improved that will enable field personnel to more easily use the test results and will reduce the need for interpretation by experts. In addition, the advanced method has the potential to reduce the time greatly and increase the accuracy of diagnostics. The important aim of the standardization is to develop the multiple diagnostic models that combine results from the different tests and give an overall assessment of reliability and maintenance for transformers.

Journal ArticleDOI
TL;DR: The absorption spectra of human skin in vivo in the wavelength range from 290 to 341 nm in 3-nm steps using laser optoacoustics are determined and the respective penetration depths are calculated.
Abstract: The wavelength-dependent penetration depth of ultraviolet radiation in human skin is a fundamental parameter for the estimation of the possible photobiological impact of ultraviolet (UV) radiation. We have determined the absorption spectra of human skin in vivo in the wavelength range from 290 to 341 nm in 3-nm steps using laser optoacoustics and calculated the respective penetration depths. Data were analyzed with respect to different skin regions and skin phototype of the 20 subjects in the study (phototype I: n=3; II: n=7; III: n=5; IV: n=5), revealing large variability between individuals. The penetration depth of UV radiation in human skin is highly dependent on wavelength and skin area, but no significant dependence on skin phototype could be found.

Journal ArticleDOI
TL;DR: This work examined the applicability of AFLP markers for reconstructing (species) relationships in Rosa, using UPGMA clustering, Wagner parsimony, and Bayesian inference to yield reliable trees.
Abstract: The genus Rosa has a complex evolutionary history caused by several factors, often in conjunction: extensive hybridization, recent radiation, incomplete lineage sorting, and multiple events of polyploidy. We examined the applicability of AFLP markers for reconstructing (species) relationships in Rosa, using UPGMA clustering, Wagner parsimony, and Bayesian inference. All trees were well resolved, but many of the deeper branches were weakly supported. The cluster analysis showed that the rose cultivars can be separated into a European and an Oriental cluster, each being related to different wild species. The phylogenetic analyses showed that (1) two of the four subgenera (Hulthemia and Platyrhodon) do not deserve subgeneric status; (2) section Carolinae should be merged with sect. Cinnamomeae; (3) subsection Rubigineae is a monophyletic group within sect. Caninae, making sect. Caninae paraphyletic; and (4) there is little support for the distinction of the five other subsections within sect. Caninae. Comparison of the trees with morphological classifications and with previous molecular studies showed that all methods yielded reliable trees. Bayesian inference proved to be a useful alternative to parsimony analysis of AFLP data. Because of their genome-wide sampling, AFLPs are the markers of choice to reconstruct (species) relationships in evolutionary complex groups.

Proceedings ArticleDOI
26 Oct 2008
TL;DR: A new approach to segment HTML pages is described, building on methods from Quantitative Linguistics and strategies borrowed from the area of Computer Vision, utilizing the notion of text-density as a measure to identify the individual text segments of a web page.
Abstract: Web Page segmentation is a crucial step for many applications in Information Retrieval, such as text classification, de-duplication and full-text search. In this paper we describe a new approach to segment HTML pages, building on methods from Quantitative Linguistics and strategies borrowed from the area of Computer Vision. We utilize the notion of text-density as a measure to identify the individual text segments of a web page, reducing the problem to solving a 1D-partitioning task. The distribution of segment-level text density seems to follow a negative hypergeometric distribution, described by Frumkina's Law. Our extensive evaluation confirms the validity and quality of our approach and its applicability to the Web.

Posted Content
TL;DR: This article examined heterogeneity in exchange rate expectations over 15 years and found that misalignments of the exchange rate and exchange rate changes explain heterogeneity, while the risk premium influences heterogeneity as well, but possible impacts from macroeconomic variables and exchange rates's volatility are dominated by the other determinants.
Abstract: This paper examines heterogeneity in exchange rate expectations. Whereas agents' heterogeneity is key in modern exchange rate models, evidence on determinants of heterogeneity is weak so far. Our sample, covering expectations from about 300 forecasters over 15 years, shows remarkable time variation in dispersion. Determinants of dispersion are consistent with the chartist-fundamentalist approach: misalignments of the exchange rate and exchange rate changes explain heterogeneity. The risk premium influences heterogeneity as well, but possible impacts from macroeconomic variables and exchange rate's volatility are dominated by the other determinants.

Journal ArticleDOI
TL;DR: In this article, a multidesign optimization (MDO) technique has been applied to maximize the energy absorption and specific energy absorption of square, rectangular and circular tubes, and the results of MDO have shown that the circular tubes have the best response.