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There are strong indications that particles containing secondary organic aerosol (SOA) exhibit amorphous solid or semi-solid phase states in the atmosphere. This may facilitate deposition ice nucleation and thus influence cirrus cloud properties. However, experimental ice nucleation studies of biogenic SOA are scarce. Here, we investigated the ice nucleation ability of viscous SOA particles.
The SOA particles were produced from the ozone initiated oxidation of α-pinene in an aerosol chamber at temperatures in the range from −38 to −10 ◦C at 5–15 % relative humidity with respect to water to ensure their formation in a highly viscous phase state, i.e. semi-solid or glassy. The ice nucleation ability of SOA particles with different sizes was investigated with a new continuous flow diffusion chamber. For the first time, we observed heterogeneous ice nucleation of viscous α-pinene SOA in the deposition mode for ice saturation ratios between 1.3 and 1.4 significantly below the homogeneous freezing limit. The maximum frozen fractions found at temperatures between −36.5 and −38.3 °C ranged from 6 to 20 % and did not depend on the particle surface area. Global modelling of monoterpene SOA particles suggests that viscous biogenic SOA particles are indeed present in regions where cirrus cloud formation takes place. Hence, they could make up an important contribution to the global ice nuclei (IN) budget.
There are strong indications that particles containing secondary organic aerosol (SOA) exhibit amorphous solid or semi-solid phase states in the atmosphere. This may facilitate heterogeneous ice nucleation and thus influence cloud properties. However, experimental ice nucleation studies of biogenic SOA are scarce. Here, we investigated the ice nucleation ability of viscous SOA particles.
The SOA particles were produced from the ozone initiated oxidation of α-pinene in an aerosol chamber at temperatures in the range from −38 to −10 °C at 5–15 % relative humidity with respect to water to ensure their formation in a highly viscous phase state, i.e. semi-solid or glassy. The ice nucleation ability of SOA particles with different sizes was investigated with a new continuous flow diffusion chamber. For the first time, we observed heterogeneous ice nucleation of viscous α-pinene SOA for ice saturation ratios between 1.3 and 1.4 significantly below the homogeneous freezing limit. The maximum frozen fractions found at temperatures between −39.0 and −37.2 °C ranged from 6 to 20 % and did not depend on the particle surface area. Global modelling of monoterpene SOA particles suggests that viscous biogenic SOA particles are indeed present in regions where cirrus cloud formation takes place. Hence, they could make up an important contribution to the global ice nucleating particle budget.
Cloud microphysical processes involving the ice phase in tropospheric clouds are among the major uncertainties in cloud formation, weather and General Circulation Models (GCMs). The simultaneous detection of aerosol particles, liquid droplets, and ice crystals, especially in the small cloud-particle size range below 50 µm, remains challenging in mixed phase, often unstable ice-water phase environments. The Cloud Aerosol Spectrometer with Polarisation (CASPOL) is an airborne instrument that has the ability to detect such small cloud particles and measure their effects on the backscatter polarisation state. Here we operate the versatile Cosmics-Leaving- OUtdoor-Droplets (CLOUD) chamber facility at the European Organisation for Nuclear Research (CERN) to produce controlled mixed phase and other clouds by adiabatic expansions in an ultraclean environment, and use the CASPOL to discriminate between different aerosols, water and ice particles. In this paper, optical property measurements of mixed phase clouds and viscous Secondary Organic Aerosol (SOA) are presented. We report observations of significant liquid – viscous SOA particle polarisation transitions under dry conditions using CASPOL. Cluster analysis techniques were subsequently used to classify different types of particles according to their polarisation ratios during phase transition. A classification map is presented for water droplets, organic aerosol (e.g., SOA and oxalic acid), crystalline substances such as ammonium sulphate, and volcanic ash. Finally, we discuss the benefits and limitations of this classi- fication approach for atmospherically relevant concentration and mixtures with respect to the CLOUD 8–9 campaigns and its potential contribution to Tropical Troposphere Layer (TTL) analysis.
Cloud microphysical processes involving the ice phase in tropospheric clouds are among the major uncertainties in cloud formation, weather, and general circulation models. The detection of aerosol particles, liquid droplets, and ice crystals, especially in the small cloud particle-size range below 50 μm, remains challenging in mixed phase, often unstable environments. The Cloud Aerosol Spectrometer with Polarization (CASPOL) is an airborne instrument that has the ability to detect such small cloud particles and measure the variability in polarization state of their backscattered light. Here we operate the versatile Cosmics Leaving OUtdoor Droplets (CLOUD) chamber facility at the European Organization for Nuclear Research (CERN) to produce controlled mixed phase and other clouds by adiabatic expansions in an ultraclean environment, and use the CASPOL to discriminate between different aerosols, water, and ice particles. In this paper, optical property measurements of mixed-phase clouds and viscous secondary organic aerosol (SOA) are presented. We report observations of significant liquid–viscous SOA particle polarization transitions under dry conditions using CASPOL. Cluster analysis techniques were subsequently used to classify different types of particles according to their polarization ratios during phase transition. A classification map is presented for water droplets, organic aerosol (e.g., SOA and oxalic acid), crystalline substances such as ammonium sulfate, and volcanic ash. Finally, we discuss the benefits and limitations of this classification approach for atmospherically relevant concentrations and mixtures with respect to the CLOUD 8–9 campaigns and its potential contribution to tropical troposphere layer analysis.
The CARIBIC (Civil Aircraft for the Regular Investigation of the Atmosphere Based on an Instrument Container) passenger aircraft observatory performed in situ measurements at 10–12 km altitude in the South Asian summer monsoon anticyclone between June and September 2008. These measurements enable us to investigate this atmospheric region (which so far has mostly been observed from satellites) using the broad suite of trace gases and aerosol particles measured by CARIBIC. Elevated levels of a variety of atmospheric pollutants (e.g. carbon monoxide, total reactive nitrogen oxides, aerosol particles, and several volatile organic compounds) were recorded. The measurements provide detailed information about the chemical composition of air in different parts of the monsoon anticyclone, particularly of ozone precursors. While covering a range of 3500 km inside the monsoon anticyclone, CARIBIC observations show remarkable consistency, i.e. with distinct latitudinal patterns of trace gases during the entire monsoon period.
Using the CARIBIC trace gas and aerosol particle measurements in combination with the Lagrangian particle dispersion model FLEXPART, we investigated the characteristics of monsoon outflow and the chemical evolution of air masses during transport. The trajectory calculations indicate that these air masses originated mainly from South Asia and mainland Southeast Asia. Estimated photochemical ages of the air were found to agree well with transport times from a source region east of 90–95° E. The photochemical ages of the air in the southern part of the monsoon anticyclone were systematically younger (less than 7 days) and the air masses were mostly in an ozone-forming chemical mode. In its northern part the air masses were older (up to 13 days) and had unclear ozone formation or destruction potential. Based on analysis of forward trajectories, several receptor regions were identified. In addition to predominantly westward transport, we found evidence for efficient transport (within 10 days) to the Pacific and North America, particularly during June and September, and also of cross-tropopause exchange, which was strongest during June and July. Westward transport to Africa and further to the Mediterranean was the main pathway during July.
The CARIBIC (Civil Aircraft for the Regular Investigation of the Atmosphere Based on an Instrument Container) passenger aircraft observatory performed in situ measurements at 10–12 km altitude in the South Asian summer monsoon anticyclone between June and September 2008. These measurements enable us to investigate this atmospheric region, which so far has mostly been observed from satellites, using the broad suite of trace gases and aerosols measured by CARIBIC. Elevated levels of a range of atmospheric pollutants were recorded e.g. carbon monoxide, total reactive nitrogen oxides, aerosol particles and several volatile organic compounds. The measurements provide detailed information about the chemical composition of air in different parts of the monsoon anticyclone, particularly of ozone precursors. While covering a range of 3500 km inside the monsoon anticyclone, CARIBIC observations show remarkable consistency, i.e. with regular latitudinal patterns of trace gases during the entire monsoon period. Trajectory calculations indicate that these air masses originated mainly from South Asia and Mainland Southeast Asia.
Using the CARIBIC trace gas and aerosol measurements in combination with the Lagrangian particle dispersion model FLEXPART we investigated the characteristics of monsoon outflow and the chemical evolution of air masses during transport. Estimated photochemical ages of the air were found to agree well with transport times from a source region east of 95 ° E. The photochemical ages of the air in the southern part of the monsoon anticyclone were consistently younger (less than 7 days) and the air masses mostly in an ozone forming chemical regime. In its northern part the air masses were older (up to 13 days) and had unclear ozone formation or destruction potential. Based on analysis of forward trajectories several receptor regions were identified. In addition to predominantly westward transport, we found evidence for efficient transport (within 10 days) to the Pacific and North America, particularly during June and September, and also of cross-tropopause exchange, which was strongest during June and July. Westward transport to Africa and further to the Mediterranean was the main pathway during July.
The first concerted multi-model intercomparison of halogenated very short-lived substances (VSLS) has been performed, within the framework of the ongoing Atmospheric Tracer Transport Model Intercomparison Project (TransCom). Eleven global models or model variants participated, simulating the major natural bromine VSLS, bromoform (CHBr3) and dibromomethane (CH2Br2), over a 20-year period (1993-2012). The overarching goal of TransCom-VSLS was to provide a reconciled model estimate of the stratospheric source gas injection (SGI) of bromine from these gases, to constrain the current measurement-derived range, and to investigate inter-model differences
due to emissions and transport processes. Models ran with standardised idealised chemistry, to isolate differences due to transport, and we investigated the sensitivity of results to a range of VSLS emission inventories. Models were tested in their ability to reproduce the observed seasonal and spatial distribution of VSLS at the surface, using measurements from NOAA’s long-term global monitoring network, and in the tropical troposphere, using recent aircraft measurements - including high altitude observations from the NASA Global Hawk platform.
The models generally capture the seasonal cycle of surface CHBr3 and CH2Br2 well, with a strong model measurement correlation (r ≥0.7) and a low sensitivity to the choice of emission inventory, at most sites. In a given model, the absolute model-measurement agreement is highly sensitive to the choice of emissions and inter-model differences are also apparent, even when using the same inventory, highlighting the challenges faced in evaluating such inventories at the global scale. Across the ensemble, most consistency is found within the tropics where most of the models (8 out of 11) achieve optimal agreement to surface CHBr3 observations using the lowest of the three CHBr3 emission inventories tested (similarly, 8 out of 11 models for CH2Br2). In general, the models are able to reproduce well observations of CHBr3 and CH2Br2 obtained in the tropical tropopause layer (TTL) at various locations throughout the Pacific. Zonal variability in VSLS loading in the TTL is generally consistent among models, with CHBr3 (and to a lesser extent CH2Br2) most elevated over the tropical West Pacific during boreal winter. The models also indicate the Asian Monsoon during boreal summer to be an important pathway for VSLS reaching the stratosphere, though the strength of this signal varies considerably among models.
We derive an ensemble climatological mean estimate of the stratospheric bromine SGI from CHBr3 and CH2Br2 of 2.0 (1.2-2.5) ppt, ∼57% larger than the best estimate from the most re- cent World Meteorological Organization (WMO) Ozone Assessment Report. We find no evidence for a long-term, transport-driven trend in the stratospheric SGI of bromine over the simulation period. However, transport-driven inter-annual variability in the annual mean bromine SGI is of the order of a ±5%, with SGI exhibiting a strong positive correlation with ENSO in the East Pacific
Given an Abelian semi-group (A, +), an A-valued curvature measure is a valuation with values in A-valued measures. If A = R, complete classifications of Hausdorff-continuous translation-invariant SO(n)-invariant valuations and curvature measures were obtained by Hadwiger and Schneider, respectively. More recently, characterisation results have been achieved for curvature measures with values in A = Sym^p R^n and A = Sym^2 Λ^q R^n for p, q ≥ 1 with varying assumptions as for their invariance properties.
In the present work, we classify all smooth translation-invariant SO(n)-covariant curvature measures with values in any SO(n)-representation in terms of certain differential forms on the sphere bundle S R^n and describe their behaviour under the globalisation map. The latter result also yields a similar classification of all continuous SO(n)-module-valued SO(n)-covariant valuations. Furthermore, a decomposition of the space of smooth translation-
invariant scalar-valued curvature measures as an SO(n)-module is obtained. As a corollary, we construct explicit bases of continuous translation-invariant scalar-valued valuations and smooth translation-invariant scalar-valued curvature measures.
Xenia von Sankt-Petersburg (Ksenija Peterburgskaja) ist eine der bedeutendsten weiblichen Heiligen in der gesamten Orthodoxie. Ihr ungewöhnliches Leben entfaltete sich im 18. Jh. in der damaligen russischen Hauptstadt Sankt-Petersburg, zu deren heiligen Patronin sie später erwählt wurde. Doch erst in den vierziger Jahre des 19. Jahrhunderts wurden die ersten Zeugnisse über ihren Lebensweg und ihr religiöses Wirken schriftlich festgehalten. Um das Jahr 1912 entstand schliesslich eine Heiligenvita Xenias; sie wurde auf Grundlage bestehender Textfragmente und dem überlieferter Erzählungen aufgezeichnet. Im Jahr 1978 wurde Xenia zunächst von der Russisch-Orthodoxen Kirche im Ausland und dann im Jahr 1988 von dem Heiligen Synod (pomestnyj sobor) der Russisch-Orthodoxen Kirche des Moskauer Patriarchats offiziell heilig gesprochen.
Die Kanonisierung bestätigte aber nur eine seit fast zweihundert Jahren bestehende Volksverehrung. Ihrem hagiographischen Typus nach wurde Xenia als jurodivaja kategorisiert. Dieses russische Wort bedeutet in etwa eine Selige, ein Tolle, eine Wahnsinnige; sinngemäss eine heilige Närrin, die um Christi Willen vor der Augen der Öffentlichkeit einen Irrgang vorspielt, bewusst ein provokatives als deviant geltendes Verhalten an den Tag legt und sich dadurch den geltenden gesellschaftlichen Konventionen radikal verweigert.
The first concerted multi-model intercomparison of halogenated very short-lived substances (VSLS) has been performed, within the framework of the ongoing Atmospheric Tracer Transport Model Intercomparison Project (TransCom). Eleven global models or model variants participated (nine chemical transport models and two chemistry–climate models) by simulating the major natural bromine VSLS, bromoform (CHBr3) and dibromomethane (CH2Br2), over a 20-year period (1993–2012). Except for three model simulations, all others were driven offline by (or nudged to) reanalysed meteorology. The overarching goal of TransCom-VSLS was to provide a reconciled model estimate of the stratospheric source gas injection (SGI) of bromine from these gases, to constrain the current measurement-derived range, and to investigate inter-model differences due to emissions and transport processes. Models ran with standardised idealised chemistry, to isolate differences due to transport, and we investigated the sensitivity of results to a range of VSLS emission inventories. Models were tested in their ability to reproduce the observed seasonal and spatial distribution of VSLS at the surface, using measurements from NOAA's long-term global monitoring network, and in the tropical troposphere, using recent aircraft measurements – including high-altitude observations from the NASA Global Hawk platform.
The models generally capture the observed seasonal cycle of surface CHBr3 and CH2Br2 well, with a strong model–measurement correlation (r ≥ 0.7) at most sites. In a given model, the absolute model–measurement agreement at the surface is highly sensitive to the choice of emissions. Large inter-model differences are apparent when using the same emission inventory, highlighting the challenges faced in evaluating such inventories at the global scale. Across the ensemble, most consistency is found within the tropics where most of the models (8 out of 11) achieve best agreement to surface CHBr3 observations using the lowest of the three CHBr3 emission inventories tested (similarly, 8 out of 11 models for CH2Br2). In general, the models reproduce observations of CHBr3 and CH2Br2 obtained in the tropical tropopause layer (TTL) at various locations throughout the Pacific well. Zonal variability in VSLS loading in the TTL is generally consistent among models, with CHBr3 (and to a lesser extent CH2Br2) most elevated over the tropical western Pacific during boreal winter. The models also indicate the Asian monsoon during boreal summer to be an important pathway for VSLS reaching the stratosphere, though the strength of this signal varies considerably among models.
We derive an ensemble climatological mean estimate of the stratospheric bromine SGI from CHBr3 and CH2Br2 of 2.0 (1.2–2.5) ppt, ∼ 57 % larger than the best estimate from the most recent World Meteorological Organization (WMO) Ozone Assessment Report. We find no evidence for a long-term, transport-driven trend in the stratospheric SGI of bromine over the simulation period. The transport-driven interannual variability in the annual mean bromine SGI is of the order of ±5 %, with SGI exhibiting a strong positive correlation with the El Niño–Southern Oscillation (ENSO) in the eastern Pacific. Overall, our results do not show systematic differences between models specific to the choice of reanalysis meteorology, rather clear differences are seen related to differences in the implementation of transport processes in the models.
Interleukin (IL)-22 is a STAT3-activating cytokine displaying characteristic AU-rich elements (ARE) in the 3'-untranslated region (3'-UTR) of its mRNA. This architecture suggests gene regulation by modulation of mRNA stability. Since related cytokines undergo post-transcriptional regulation by ARE-binding tristetraprolin (TTP), the role of this destabilizing protein in IL-22 production was investigated. Herein, we demonstrate that TTP-deficient mice display augmented serum IL-22. Likewise, IL-22 mRNA was enhanced in TTP-deficient splenocytes and isolated primary T cells. A pivotal role for TTP is underscored by an extended IL-22 mRNA half-life detectable in TTP-deficient T cells. Luciferase-reporter assays performed in human Jurkat T cells proved the destabilizing potential of the human IL-22-3'-UTR. Furthermore, overexpression of TTP in HEK293 cells substantially decreased luciferase activity directed by the IL-22-3'-UTR. Transcript destabilization by TTP was nullified upon cellular activation by TPA/A23187, an effect dependent on MEK1/2 activity. Accordingly, IL-22 mRNA half-life as determined in TPA/A23187-stimulated Jurkat T cells decreased under the influence of the MEK1/2 inhibitor U0126. Altogether, data indicate that TTP directly controls IL-22 production, a process counteracted by MEK1/2. The TTP-dependent regulatory pathway described herein likely contributes to the role of IL-22 in inflammation and cancer and may evolve as novel target for pharmacological IL-22 modulation.
NLP4CMC III : 3rd workshop on natural language processing for computer-mediated communication
(2016)
The present paper reports the first results of the compilation and annotation of a blog corpus for German. The main aim of the project is the representation of the blog discourse structure and relations between its elements (blog posts, comments) and participants (bloggers, commentators). The data included in the corpus were manually collected from the scientific blog portal SciLogs. The feature catalogue for the corpus annotation includes three types of information which is directly or indirectly provided in the blog or can be construed by means of statistical analysis or computational tools. At this point, only directly available information (e.g., title of the blog post, name of the blogger etc.) has been annotated. We believe, our blog corpus can be of interest for the general study of blog structure or related research questions as well as for the development of NLP methods and techniques (e.g. for authorship detection).
Already today modern driver assistance systems contribute more and more to make individual mobility in road traffic safer and more comfortable. For this purpose, modern vehicles are equipped with a multitude of sensors and actuators which perceive, interpret and react to the environment of the vehicle. In order to reach the next set of goals along this path, for example to be able to assist the driver in increasingly complex situations or to reach a higher degree of autonomy of driver assistance systems, a detailed understanding of the vehicle environment and especially of other moving traffic participants is necessary.
It is known that motion information plays a key role for human object recognition [Spelke, 1990]. However, full 3D motion information is mostly not taken into account for Stereo Vision-based object segmentation in literature. In this thesis, novel approaches for motion-based object segmentation of stereo image sequences are proposed from which a generic environmental model is derived that contributes to a more precise analysis and understanding of the respective traffic scene. The aim of the environmental model is to yield a minimal scene description in terms of a few moving objects and stationary background such as houses, crash barriers or parking vehicles. A minimal scene description aggregates as much information as possible and it is characterized by its stability, precision and efficiency.
Instead of dense stereo and optical flow information, the proposed object segmentation builds on the so-called Stixel World, an efficient superpixel-like representation of space-time stereo data. As it turns out this step substantially increases stability of the segmentation and it reduces the computational time by several orders of magnitude, thus enabling real-time automotive use in the first place. Besides the efficient, real-time capable optimization, the object segmentation has to be able to cope with significant noise which is due to the measurement principle of the used stereo camera system. For that reason, in order to obtain an optimal solution under the given extreme conditions, the segmentation task is formulated as a Bayesian optimization problem which allows to incorporate regularizing prior knowledge and redundancies into the object segmentation.
Object segmentation as it is discussed here means unsupervised segmentation since typically the number of objects in the scene and their individual object parameters are not known in advance. This information has to be estimated from the input data as well.
For inference, two approaches with their individual pros and cons are proposed, evaluated and compared. The first approach is based on dynamic programming. The key advantage of this approach is the possibility to take into account non-local priors such as shape or object size information which is impossible or which is prohibitively expensive with more local, conventional graph optimization approaches such as graphcut or belief propagation.
In the first instance, the Dynamic Programming approach is limited to one-dimensional data structures, in this case to the first Stixel row. A possible extension to capture multiple Stixel rows is discussed at the end of this thesis.
Further novel contributions include a special outlier concept to handle gross stereo errors associated with so-called stereo tear-off edges. Additionally, object-object interactions are taken into account by explicitly modeling object occlusions. These extensions prove to be dramatic improvements in practice.
This first approach is compared with a second approach that is based on an alternating optimization of the Stixel segmentation and of the relevant object parameters in an expectation maximization (EM) sense. The labeling step is performed by means of the _−expansion graphcut algorithm, the parameter estimation step is done via one-dimensional sampling and multidimensional gradient descent. By using the Stixel World and due to an efficient implementation, one step of the optimization only takes about one millisecond on a standard single CPU core. To the knowledge of the author, at the time of development there was no faster global optimization in a demonstrator car.
For both approaches, various testing scenarios have been carefully selected and allow to examine the proposed methods thoroughly under different real-world conditions with limited groundtruth at hand. As an additional innovative application, the first approach was successfully implemented in a demonstrator car that drove the so-called Bertha Benz Memorial Route from Mannheim to Pforzheim autonomously in real traffic.
At the end of this thesis, the limits of the proposed systems are discussed and a prospect on possible future work is given.
BACKGROUND: Microvascular ischemia is one of the hallmarks of hypertrophic cardiomyopathy (HCM) and has been associated with poor outcome. However, myocardial fibrosis, seen on cardiovascular magnetic resonance (CMR) as late gadolinium enhancement (LGE), can be responsible for rest perfusion defects in up to 30% of patients with HCM, potentially leading to an overestimation of the ischemic burden. We investigated the effect of left ventricle (LV) scar on the total LV ischemic burden using novel high-resolution perfusion analysis techniques in conjunction with LGE quantification.
METHODS: 30 patients with HCM and unobstructed epicardial coronary arteries underwent CMR with Fermi constrained quantitative perfusion analysis on segmental and high-resolution data. The latter were corrected for the presence of fibrosis on a pixel-by-pixel basis.
RESULTS: High-resolution quantification proved more sensitive for the detection of microvascular ischemia in comparison to segmental analysis. Areas of LGE were associated with significant reduction of myocardial perfusion reserve (MPR) leading to an overestimation of the total ischemic burden on non-corrected perfusion maps. Using a threshold MPR of 1.5, the presence of LGE caused an overestimation of the ischemic burden of 28%. The ischemic burden was more severe in patients with fibrosis, also after correction of the perfusion maps, in keeping with more severe disease in this subgroup.
CONCLUSIONS: LGE is an important confounder in the assessment of the ischemic burden in patients with HCM. High-resolution quantitative analysis with LGE correction enables the independent evaluation of microvascular ischemia and fibrosis and should be used when evaluating patients with HCM.
Stifter-Gänge
(2007)
Ist 'das Ding' Stifters liebstes Substantiv, so darf 'gehen' als sein bevorzugtes Verb gelten. In der Erzählung 'Der Waldgänger' sieht sich etwa der an einem lebensweltlichen und geographischen "Scheidepunkte" innehaltende Wanderer von einer Landschaft umgeben, in der die Dinge buchstäblich ihren Gang gehen:
'Ganz oben, wo das Thal mit noch geringer Tiefe anfängt, begann auch ein winziges Wasserfädlein, neben dem Wanderer abwärts zu gehen. Es ging in dem Rinnsale neben dem Wege unhörbar und nur glizzernd vorwärts, bis es durch die Menge des durch die Höhen sickernden Wassers gestärkt vor ihm plaudernd und rauschend einher hüpfte, als wolle es ihm den Weg durch die Thalmündung hinaus zeigen [...]. Sie gingen an manchem Waldabhange, an mancher schattigen Stelle vorbei [...], sie gingen an manchen zerstreuten Häuschen, an mancher Mühle, an mancher auf einem tiefgelegenen Wiesenflecken weidenden Kuh vorüber, bis endlich nach einigen Stunden Wanderns [...] die hingebreitete große Ebene begann. Der Bach ging breit und wallend links gegen die Felder und Bäume [...]. (WG, 98f)'
Dem Gang der Dinge untersteht der Lauf der Welt. Diese Identität von Naturvorgängen und Lebensläufen immer neu, allen Irrwegen und Katastrophen, allen Sprüngen und Brüchen zum Trotz, unter Beweis stellen zu wollen, tritt Stifters Autorschaft an. Trauma und Trost seines Universums liegen beschlossen in dem fast stereotyp wiederkehrenden Satz: "Und so ging es immer fort."
Does an increase in competition increase or decrease bank stability? I exploit how the state-specific process of interstate banking deregulation lowered barriers to entry into urban banking markets and find that greater competition significantly increases bank stability. This result is robust to the inclusion of additional fixed effects and other influences, such as merger and acquisitions or diversification. Moreover, I find that greater competition reduces banks' nonperforming loans and increases bank profitability. These findings suggest that competition increases stability as it improves bank profitability and asset quality.
Returns to experience for U.S. workers have changed over the post-war period. This paper argues that a simple model goes a long way towards replicating these changes. The model features three well-known ingredients: (i) an aggregate production function with constant skill-biased technical change; (ii) cohort qualities that vary with average years of schooling; and crucially (iii) time-invariant age-efficiency profiles. The model quantitatively accounts for changes in longitudinal and cross-sectional returns to experience, as well as the differential evolution of the college wage premium for young and old workers.
We reconsider the role for human capital in accounting for cross-country income differences. Our contribution is to bring to bear new data on the pre- and post- migration labor market experiences of immigrants to the U.S. Immigrants from poor countries experience wage gains that are only 40 percent of the GDP per worker gap, which implies that “country" accounts for 40 percent of income differences, while human capital accounts for 60 percent. Our approach handles selection by comparing the wage of the same individual in two different countries. We also provide evidence on and a correction for skill transfer.
We examine the impact of house prices on labour supply decisions using UK micro data. We combine household survey data with local level house price measures and controls for local labour demand. Our micro data also allows us to control for individual level income expectations. We find significant house price effects on labour supply, consistent with leisure being a normal good. Labour supply responses to house prices are concentrated among young married female owners and older owners. This finding suggests house prices affect the decisions of marginal workers in the economy. Our estimates imply house prices are economically important for the participation decisions for these workers.
Although Walter Benjamin was never timid when it came to writing, one practice he consistently avoided was that of creating neologisms. It is therefore with all the more reluctance that I find myself compelled to resort to something similar, in order to sum up a motif that has imposed itself over the years in my reading of Benjamin. What is involved is, to be sure, not exactly a neologism, since it does not involve the creation of a new word, but rather the highlighting of a word-part, a suffix (eine Nachsilbe). In English, to be sure, this suffix, when spoken, is indistinguishable from a word: what distinguishes it from a word is not audible, but only legible: a hyphen, marking a separation that is also a joining, a 'Bindestrich' that does not bind it to anything in particular and yet that requires it to be bound to something else. The suffix in question thus sounds deceptively familiar, since it coincides, audibly, with the word "abilities". However, unlike that word, its first letter - which purely by accident happens to be the first letter of the alphabet--is preceded by a dash. When written in isolation, this gives it a somewhat bizarre appearance, to be sure, since suffixes are not usually encountered separately from the words they modify. But this bizarre appearance pales when compared to its German 'original'. If the book of essays to be published in English under the title, "Benjamin’s -abilities," is ever translated into German - "back" into German I was tempted to write, since German here is of course the language in which Benjamin wrote and in which I generally read him - then its title, were it to be entirely faithful to the English, would indeed have to involve the creation of a neologism. For translated back into German, the German title would require its readers to "read, what was never written", namely: "Benjamins -barkeiten" (written, "Bindestrich- b--kleingeschrieben").
En tentant de regarder une image singulière avec quelques mots de Walter Benjamin, je voudrais, non pas me livrer à un exercice de commentaire, de glose ou de déchiffrement, mais, plus modestement, faire acte de reconnaissance, porter témoignage d’une experience de l’image, d’une 'poétique de l’image'. Walter Benjamin, l’un des penseurs qui a le plus radicalement bouleversé - réinventé - la notion de lisibilité (Lesbarkeit), est aussi l’un des penseurs au contact duquel l’histoire de l’art se trouve bouleversée dans son rapport même à la visibilité (Sichtbarkeit) et à la temporalité des images. Il ne s’agit pas seulement de rendre hommage à celui qui, mieux que quiconque, aura théorisé le rôle de la reproductibilité, taconté l’histoire de "l’art en tant que photographie" ou décrit le "déclin de l’aura". Il s’agit de travailler avec sa façon de mettre le temps au coeur de toute question d’image, et de faire de l’image - à commencer par la fameuse "image dialectique" - l’opérateur central de toute historicité. Le meilleur hommage, la meilleure justice que l’on puisse rendre à quelque chose, dit Benjamin - en parlant des "guenilles", des "rebuts" de l’histoire -, c’est de l’utiliser. Je vais tâcher de suivre cette leçon en vous présentant un objet de travail et en essayant de restituer la 'valeur d’usage' d’un ou de deux textes de Benjamin pour tenter de savoir, tout simplement, 'comment regarder une image'.
We study money creation and destruction in today’s monetary architecture and examine the impact of monetary policy and capital regulation in a general equilibrium setting. There are two types of money created and destructed: bank deposits, when banks grant loans to firms or to other banks and central bank money, when the central bank grants loans to private banks. We show that equilibria yield the first-best level of money creation and lending when prices are flexible, regardless of the monetary policy or capital regulation. When prices are rigid, we identify the circumstances in which money creation is excessive or breaks down and the ones in which an adequate combination of monetary policy and capital regulation can restore efficiency.
The dramatic shift from traditional pension plans to participant-directed 401(k) plans has increased the decision-making responsibility of individual investors for their own retirement planning. With this shift comes increasing evidence that investors are making poor decisions in choosing how much to save for retirement and in selecting among their investment options. Studies question the value of efforts to improve these decisions through regulatory reforms or investor education.
This article posits that deficiencies in workplace retirement savings cannot be adequately addressed until the reasons for poor investment decisions are better understood. We report the results of an exploratory study that asked subjects to complete a simulated retirement investment task and collected information about their financial knowledge and preferences. The study enabled us to measure financial literacy and evaluate its relationship to retirement investment decision-making. In line with existing research, we found a strong relationship between financial literacy and successful retirement investing. Our results suggest, however, that the relevant understanding in this context is not about math so much as it is a basic knowledge of the relative costs and benefits of the major investment categories. Finally, we present results suggesting that financial literacy is separate from investment preferences — specifically, that tolerance for risk is a separate and highly predictive variable in estimating retirement planning success.
Our research suggests that individual employees are likely to lack the skills necessary to support the current regulatory model of participant-directed retirement investing. The structure and regulation of retirement plans ought to take this fact seriously. We explore the potential for investor education and professional advice, respectively, to overcome the limitations of individualized choice.