bluuebunny/crossref_metadata_2025 huggingface dataset:
Ice water content vertical profiles of high-level clouds: classification and impact on radiative fluxes
Authors: Feofilov A. G. , Stubenrauch C. J. , Delanoë J.
Published: November 2015

Abstract. In this article, we discuss the shape of ice water content (IWC) vertical profiles in high ice clouds and its effect on their radiative properties, both in short- and in long-wave bands (SW and LW). Based on the analysis of collocated satellite data, we propose a minimal set of primitive shapes (rectangular, isosceles trapezoid, lower and upper triangle), which represents the IWC profiles sufficiently well. About 75 % of all high-level ice clouds (P < 440 hPa) have an ice water path (IWP) smaller than 100 g m−2, with a 10 % smaller contribution from single layer clouds. Most IWC profiles (80 %) can be represented by a rectangular or isosceles trapezoid shape. However, with increasing IWP, the number of lower triangle profiles (IWC rises towards cloud base) increases, reaching up to 40 % for IWP values greater than 300 g m−2. The number of upper triangle profiles (IWC rises towards cloud top) is in general small and decreases with IWP, with the maximum occurrence of 15 % in cases of IWP less than 10 g m−2. We propose a statistical classification of the IWC shapes using IWP as a single parameter. We have estimated the radiative effects of clouds with the same IWP and with different IWC profile shapes for five typical atmospheric scenarios and over a broad range of IWP, cloud height, cloud vertical extent, and effective ice crystal diameter (De). We explain changes in outgoing LW fluxes at the top of the atmosphere (TOA) by the cloud thermal radiance while differences in TOA SW fluxes relate to the De vertical profile within the cloud. Absolute differences in net TOA and surface fluxes associated with these parameterized IWC profiles instead of assuming constant IWC profiles are in general of the order of 1–2 W m−2: they are negligible for clouds with IWP < 30 g m−2, but may reach 2 W m−2 for clouds with IWP > 300 W m−2.
Spatial and temporal variability of clouds and precipitation over Germany: multiscale simulations across the "gray zone"
Authors: Barthlott C. , Hoose C.
Published: November 2015

Abstract. This paper assesses the resolution dependance of clouds and precipitation over Germany by numerical simulations with the COnsortium for Small-scale MOdeling (COSMO) model. Six intensive observation periods of the HOPE (HD(CP)2 Observational Prototype Experiment) measurement campaign conducted in spring 2013 and 1 summer day of the same year are simulated. By means of a series of grid-refinement resolution tests (horizontal grid spacing 2.8, 1 km, 500, and 250 m), the applicability of the COSMO model to represent real weather events in the gray zone, i.e., the scale ranging between the mesoscale limit (no turbulence resolved) and the large-eddy simulation limit (energy-containing turbulence resolved), is tested. To the authors' knowledge, this paper presents the first non-idealized COSMO simulations in the peer-reviewed literature at the 250–500 m scale. It is found that the kinetic energy spectra derived from model output show the expected −5/3 slope, as well as a dependency on model resolution, and that the effective resolution lies between 6 and 7 times the nominal resolution. Although the representation of a number of processes is enhanced with resolution (e.g., boundary-layer thermals, low-level convergence zones, gravity waves), their influence on the temporal evolution of precipitation is rather weak. However, rain intensities vary with resolution, leading to differences in the total rain amount of up to +48 %. Furthermore, the location of rain is similar for the springtime cases with moderate and strong synoptic forcing, whereas significant differences are obtained for the summertime case with air mass convection. Domain-averaged liquid water paths and cloud condensate profiles are used to analyze the temporal and spatial variability of the simulated clouds. Finally, probability density functions of convection-related parameters are analyzed to investigate their dependance on model resolution and their impact on cloud formation and subsequent precipitation.
Technical note: New particle formation event forecasts during PEGASOS–Zeppelin Northern mission 2013 in Hyytiälä, Finland
Authors: Nieminen T. , Yli-Juuti T. , Manninen H. E. , Petäjä T. , Kerminen V.-M. , Kulmala M.
Published: November 2015

Abstract. New particle formation (NPF) occurs frequently in the global atmosphere. During recent years, detailed laboratory experiments combined with intensive field observations in different locations have provided insights into the vapours responsible for the initial formation of particles and their subsequent growth. In this regard, the importance of sulfuric acid, stabilizing bases such as ammonia and amines as well as extremely low volatile organics, have been proposed. The instrumentation to observe freshly formed aerosol particles has developed to a stage where the instruments can be implemented as part of airborne platforms, such as aircrafts or a Zeppelin-type airship. Flight measurements are technically more demanding and require a greater detail of planning than field studies at the ground level. The high cost of flight hours, limited time available during a single research flight for the measurements, and different instrument payloads in Zeppelin airship for various flight missions demanded an analysis tool that would forecast whether or not there is a good chance for an NPF event. Here we present a methodology to forecast NPF event probability at the SMEAR II site in Hyytiälä, Finland. This methodology was used to optimize flight hours during the PEGASOS (Pan-European Gas Aerosol Climate Interaction Study)–Zeppelin Northern mission in May–June 2013. Based on the existing knowledge, we derived a method for estimating the nucleation probability that utilizes forecast air mass trajectories, weather forecasts, and air quality model predictions. With the forecast tool we were able to predict the occurrence of NPF events for the next day with more than 90 % success rate (10 out of 11 NPF event days correctly predicted). To our knowledge, no similar forecasts of NPF occurrence have been developed for other sites. This method of forecasting NPF occurrence could be applied also at other locations, provided that long-term observations of conditions favouring particle formation are available.
Diurnal cycle and multi-decadal trend of formaldehyde in the remote atmosphere near 46° N
Authors: Franco B. , Marais E. A. , Bovy B. , Bader W. , Lejeune B. , Roland G. , Servais C. , Mahieu E.
Published: November 2015

Abstract. Only very few long-term trends of formaldehyde (HCHO) exist. Furthermore, many uncertainties remain as to its diurnal cycle, representing a large short-term variability superimposed on seasonal and inter-annual variations that should be accounted for when comparing ground-based observations to e.g., model results. In this study, we derive a multi-decadal time series (January 1988–June 2015) of HCHO total columns from ground-based high-resolution Fourier transform infrared (FTIR) solar spectra recorded at the high-altitude station of Jungfraujoch (Swiss Alps, 46.5° N, 8.0° E, 3580 m a.s.l.), allowing for the characterization of the mid-latitudinal atmosphere for background conditions. First we investigate the HCHO diurnal variation, peaking around noontime and mainly driven by the intra-day insolation modulation and methane (CH4) oxidation. We also characterize quantitatively the diurnal cycles by adjusting a parametric model to the observations, which links the daytime to the HCHO columns according to the monthly intra-day regimes. It is then employed to scale all the individual FTIR measurements on a given daytime in order to remove the effect of the intra-day modulation for improving the trend determination and the comparison with HCHO columns simulated by the state-of-the-art chemical transport model GEOS-Chem v9-02. Such a parametric model will be useful to scale the Jungfraujoch HCHO columns on satellite overpass times in the framework of future calibration/validation efforts of space borne sensors. GEOS-Chem sensitivity tests suggest then that the seasonal and inter-annual HCHO column variations above Jungfraujoch are predominantly led by the atmospheric CH4 oxidation, with a maximum contribution of 25 % from the anthropogenic non-methane volatile organic compound precursors during wintertime. Finally, trend analysis of the so-scaled 27 year FTIR time series reveals a long-term evolution of the HCHO columns in the remote troposphere to be related with the atmospheric CH4 fluctuations and the short-term OH variability: +2.9 % yr−1 between 1988 and 1995, −3.7 % yr−1 over 1996–2002 and +0.8 % yr−1 from 2003 onwards.
Superimposed disturbance in the ionosphere triggered by spacecraft launches in China
Authors: He L. M. , Wu L. X. , Liu S. J. , Liu S. N.
Published: November 2015

Abstract. Using GPS dual-frequency observations collected by continuously operating GPS tracking stations in China, superimposed disturbances caused by the integrated action of spacecraft's physical effect and chemical effect on ionosphere during the launches of the spacecrafts Tiangong-1 and Shenzhou-8 in China were firstly determined. The results show that the superimposed disturbance was composed of remarkable ionospheric waves and significant ionospheric depletion emerged after both launches. Meanwhile, we found for the first time that the ionospheric waves were made up of two periods of wave by wavelet analysis. The first period of ∼ 4 min shows one event in the near stations and two sub-events in the few far stations. The second period of ∼ 9 min shows only one event in all the observed stations. Finally, the time characteristics for ionospheric waves and depletions were examined.
Prescribed-burning vs. wildfire: management implications for annual carbon emissions along a latitudinal gradient of Calluna vulgaris-dominated vegetation
Authors: Santana V. M. , Alday J. G. , Lee H. , Allen K. A. , Marrs R. H.
Published: November 2015

Abstract. A~present challenge in fire ecology is to optimize management techniques so that ecological services are maximized and C emissions minimized. Here, we model the effects of different prescribed-burning rotation intervals and wildfires on carbon emissions (present and future) in British moorlands. Biomass-accumulation curves from four Calluna-dominated ecosystems along a north–south, climatic gradient in Great Britain were calculated and used within a matrix-model based on Markov Chains to calculate above-ground biomass-loads, and annual C losses under different prescribed-burning rotation intervals. Additionally, we assessed the interaction of these parameters with an increasing wildfire return interval. We observed that litter accumulation patterns varied along the latitudinal gradient, with differences between northern (colder and wetter) and southern sites (hotter and drier). The accumulation patterns of the living vegetation dominated by Calluna were determined by site-specific conditions. The optimal prescribed-burning rotation interval for minimizing annual carbon losses also differed between sites: the rotation interval for northern sites was between 30 and 50 years, whereas for southern sites a hump-backed relationship was found with the optimal interval either between 8 to 10 years or between 30 to 50 years. Increasing wildfire frequency interacted with prescribed-burning rotation intervals by both increasing C emissions and modifying the optimum prescribed-burning interval for C minimum emission. This highlights the importance of studying site-specific biomass accumulation patterns with respect to environmental conditions for identifying suitable fire-rotation intervals to minimize C losses.
Effects of mountain tea plantations on nutrient cycling at upstream watersheds
Authors: Lin T.-C. , Shaner P.-J. L. , Wang L.-J. , Shih Y.-T. , Wang C.-P. , Huang G.-H. , Huang J.-C.
Published: November 2015

Abstract. The expansion of agriculture to rugged mountains can exacerbate negative impacts of agricultural activities on ecosystem function. In this study, we monitored streamwater and rainfall chemistry of mountain watersheds at the Feitsui Reservoir Watershed in northern Taiwan to examine the effects of agriculture on watershed nutrient cycling. We found that the greater the proportion of tea plantation cover, the higher the concentrations of fertilizer-associated ions (NO3−, K+) in streamwater of the four mountain watersheds examined; on the other hand, the concentrations of the ions that are rich in soils (SO42−, Ca2+, Mg2+) did not increase with the proportion of tea plantation cover, suggesting that agriculture enriched fertilizer-associated nutrients in streamwater. Of the two watersheds for which rainfall chemistry was available, the one with higher proportion of tea plantation cover had higher concentrations of ions in rainfall and retained less nitrogen in proportion to input compared to the more pristine watershed, suggesting that agriculture can influence atmospheric deposition of nutrients and a system's ability to retain nutrients. As expected, we found that a forested watershed downstream of agricultural activities can dilute the concentrations of NO3− in streamwater by more than 70 %, indicating that such a landscape configuration helps mitigate nutrient enrichment in aquatic systems even for watersheds with steep topography. We estimated that tea plantation at our study site contributed approximately 450 kg ha−1 yr−1 of NO3-N via streamwater, an order of magnitude greater than previously reported for agricultural lands around the globe, which can only be matched by areas under intense fertilizer use. Furthermore, we constructed watershed N fluxes to show that excessive leaching of N, and additional loss to the atmosphere via volatilization and denitrification can occur under intense fertilizer use. In summary, this study demonstrated the pervasive impacts of agricultural activities, especially excessive fertilization, on ecosystem nutrient cycling at mountain watersheds.
Quantitative analysis of biogeochemically controlled density stratification in an iron-meromictic lake
Authors: Nixdorf E. , Boehrer B.
Published: November 2015

Abstract. Lake stratification controls the cycling of dissolved matter within the water body. This is of particular interest in the case of meromictic lakes, where permanent density stratification of the deep water limits vertical transport, and a chemically different (reducing) milieu can be established. As a consequence, the geochemical setting and the mixing regime of a lake can stabilize each other mutually. We attempt a quantitative approach to the contribution of chemical reactions sustaining the density stratification. As an example, we chose the prominent case of iron meromixis in Waldsee near Doebern, a small lake that originated from near-surface underground mining of lignite. From a data set covering 4 years of monthly measured electrical conductivity profiles, we calculated summed conductivity as a quantitative variable reflecting the amount of electro-active substances in the entire lake. Seasonal variations followed the changing of the chemocline height. Coinciding changes of electrical conductivities in the monimolimnion indicated that a considerable share of substances, precipitated by the advancing oxygenated epilimnion, re-dissolved in the remaining anoxic deep waters and contributed considerably to the density stratification. In addition, we designed a lab experiment, in which we removed iron compounds and organic material from monimolimnetic waters by introducing air bubbles. Precipitates could be identified by visual inspection. Eventually, the remaining solutes in the aerated water layer looked similar to mixolimnetic Waldsee water. Due to its reduced concentration of solutes, this water became less dense and remained floating on nearly unchanged monimolimnetic water. In conclusion, iron meromixis as seen in Waldsee did not require two different sources of incoming waters, but the inflow of iron-rich deep groundwater and the aeration through the lake surface were fully sufficient for the formation of iron meromixis.
Liquefaction susceptibility assessment in fluvial plains using airborne lidar: the case of the 2012 Emilia earthquake sequence area (Italy)
Authors: Civico R. , Brunori C. A. , De Martini P. M. , Pucci S. , Cinti F. R. , Pantosti D.
Published: November 2015

Abstract. We report a case study from the Po River plain region (northern Italy), where significant liquefaction-related land and property damage occurred during the 2012 Emilia seismic sequence. We took advantage of a 1 m pixel lidar digital terrain model (DTM) and of the 2012 Emilia coseismic liquefaction data set to (a) perform a detailed geomorphological study of the Po River plain area and (b) quantitatively define the liquefaction susceptibility of the geomorphologic features that experienced different abundance of liquefaction. One main finding is that linear topographic highs of fluvial origin – together with crevasse splays, abandoned riverbeds and very young land reclamation areas – acted as a preferential location for the occurrence of liquefaction phenomena. Moreover, we quantitatively defined a hierarchy in terms of liquefaction susceptibility for an ideal fluvial environment. We observed that a very high liquefaction susceptibility is found in coincidence with fluvial landforms, a high-to-moderate liquefaction susceptibility within a buffer distance of 100 and 200 m from mapped fluvial landforms and a low liquefaction susceptibility outside fluvial landforms and relative buffer areas. Lidar data allowed a significant improvement in mapping with respect to conventionally available topographic data and/or aerial imagery. These results have significant implications for accurate hazard and risk assessment as well as for land-use planning. We propose a simple geomorphological approach for liquefaction susceptibility estimation. Our findings can be applied to areas beyond Emilia that are characterized by similar fluvial-dominated environments and prone to significant seismic hazard.
Responses of atmospheric circulation to sea surface temperature anomalies in the South China Sea
Authors: Zhou M. P. , Wang G. H.
Published: November 2015

Abstract. The sea surface temperature (SST) anomalies in the South China Sea (SCS) and their influences on global atmospheric circulation were studied. The results of a simple atmospheric model suggested that the SCS SST anomalies can induce several barotropic wave trains from the SCS to other regions such as North America, high latitudes of the Southern Hemisphere and the Mediterranean. The baroclinic stream function anomalies from the simple model showed an anticyclonic vortex pair in the Asian continent and the northern and southern Indian Ocean and a cyclonic vortex in the North Pacific and the southwestern Pacific. It is suggested that the spatial pattern of SST anomalies in the SCS can affect the magnitude of stream function anomalies, although it cannot affect the spatial pattern of atmospheric circulation.
CO2 emission and structural characteristics of two calcareous soils amended with municipal solid waste and plant residue
Authors: Yazdanpanah N.
Published: November 2015

Abstract. This investigation examines the effect of different amendments on selected soil physical and biological properties over a twenty four month period in two cropland fields. Urban municipal solid waste (MSW) compost and alfalfa residue (AR) were used as different organic amendments at the rates of 0 (control), 10 and 30 Mg ha−1 to a clay loam soil and a loamy sand soil in a semiarid region. Result showed that the soil improvement was controlled by the application rate and decomposability of amendments and soil type. The addition of organic amendments to the soils improved aggregate stability and consequently enhanced total porosity, especially macro pores fraction. The increased soil organic carbon (SOC) and total porosity values as compared to the control treatment were greater in the loamy sand soil than in the clay loam soil. Moreover, compared to the microbial respiration of control plots, the application of MSW resulted in higher values of microbial respiration in the clay loam soil than in the loamy sand soil, whereas the reverse order was found for AR. Linear and power functions were provided for the relationships between microbial respiration and SOC in the loamy sand and clay loam soils, respectively. Also, CO2 emission was stimulated significantly as power functions of the total porosity and the ratio of macro to micro pores. However, the soil microbial respiration and carbon storage improved aggregate stability and pore size distribution, as a response, soil porosity especially macro pores fraction controlled CO2 flux.
The user as network
Authors: Levy Karen E.C.
Published: November 2015

The user has become central to the way technology is conceptualized, designed, and studied in sociotechnical research and human-computer interaction; recently, non-users have also become productive foci of scholarly analysis. This paper argues that a focus on individualized users and non-users is incomplete, and conflates multiple modes of complex relation among people, institutions, and technologies. Rather than the use/non-use conception, I argue for conceptualizing users as networks: as constellations of power relations and institutional entanglements, mediated through technologies. To illustrate, I offer a case study of Nexafed, a tamperproof formulation of pseudoephedrine. The market for Nexafed seems nonexistent in traditional use/non-use terms, but when we construe the user more broadly — as a network of interpersonal, legal, and institutional relationships, consisting of multiple modes of relation between people and technology — not only does the drug’s market make sense, but we also understand how new motivations (social shame, mistrust, robbery, gossip) can act as salient drivers of technology use. The Nexafed case illustrates the utility of a networked perspective to develop more nuanced theoretical understandings of use and non-use in sociotechnical relations, beyond the direct human-technology interface.
Replicants, imposters and the real deal: Issues of non-use and technology resistance in vintage and software instruments
Authors: Thorén Claes , Kitzmann Andreas
Published: November 2015

This paper explores non-use and technology resistance among musicians and enthusiasts devoted to analog synthesizers (particularly vintage synthesizers from the 1970s), and the recent influx of software simulations that often elicit critical and negative reactions among this group of devotees. Drawing on a combination of assemblage theory and affect theory this paper presents a case study of a prominent online music community and asks: What does this particular instance of technological resistance reveal about the social construction of technology and the on-going emotional and material negotiations that constitute digital and analog experiences? Results show that the possession or appreciation of analog synthesizers and the rejection of their digital counterparts is less about composing music or playing with others and more about a solitary activity that is deeply emotional, experiential and carefully untainted by the impurity of digital processing and equipment.
Why study technology non-use?
Authors: Baumer Eric P.S. , Ames Morgan G. , Burrell Jenna , Brubaker Jed R. , Dourish Paul
Published: November 2015

This special issue provides an opportunity to rethink how we approach, study, and conceptualize human relationships with, and through, technology. The authors in this collection take a multiplicity of approaches on diverse topics to develop a rigorous theoretical understanding for non-use, setting crucial groundwork for future research.
Entangled with technology: Engagement with Facebook among the young old
Authors: Van House Nancy A.
Published: November 2015

This article frames the concepts of use and non-use in terms of Ingold’s understanding of life as on-going movement along multiple lines, or meshwork, and tangles of relationships to people, places, and things. In addition, I draw on practice theory and the turn to ontology, which argues that any one technology is enacted as multiple technologies via different practices. Based on a study of engagement with Facebook among the young old (age 60 to 70), I argue that use and non-use can be understood in terms of the different versions of a technology enacted or envisioned. A person’s engagement with a technology is a knot in the tangle of lines that are the trajectories of technologies and of people’s lives.
International Host Communities: A Positioning Platform for Zimbabwe Tourism Brand
Authors: Chigora Farai , Zvavahera Promise
Published: November 2015

The study investigated the strength of showcasing Zimbabwe tourism destination offerings at international platforms to its tourism brand performance. This was mainly based on the fact that the Zimbabwe tourism destination authorities are investing more in selling the country’s tourism brand at international platforms but not gaining a huge mileage in positioning the brand. The study employed a mixed methods research design combing both quantitative and qualitative approaches in extracting data from respondents. An in-depth interview was employed first as a qualitative technique in order to find the most common showcasing platforms from Zimbabwe tourism brand. This was done to senior managers and experts in the Zimbabwe tourism industry. Their responses revealed the platforms as carnivals, road shows, indabas, regional magazines and international interactive websites. A quantitative research was therefore done using survey questionnaires that were distributed to foreigners and local in order to assess the most dominant platform for positioning Zimbabwe’s tourism brand. The results show that indabas are the most effective platforms to brand Zimbabwe tourism brand. This is followed by international interactive websites and regional magazines. The research recommended that internationlising brand showcasing does not yield more on its own. There is a need to start with intensive local acceptance then go regional and international.
A New Approach Model in Post Graduate Training of Local Government Officers
Authors: Tózsa István
Published: November 2015

This study is based on the final report of Program ÁROP 2.2.22 entitled Training for the Local Governments of the Convergence Regions realized at the National University of Public Service, Hungary by the professional advisor of Program ÁROP 2.2.22.

In 2013-15 there was a new type of post graduate training elaborated and piloted in Hungary at the Institute of Executive Training and Continuing Education (VTKI) within the National University of Public Service (NKE). Although the pilot financed by the State Administration Reform Operative Program (ÁROP) had not lacked the previously established attempts to include interactivity in the training, it was the first to observe and apply the actual principles of the European Union 2020 expressed in the threefold criteria of economic growth: smartness, sustainability and inclusiveness. All of them are represented by a pillar of the program like e-learning, class training and field training with the inclusion of local society. According to the objectives of the program there were at least 10 thousand attendees from the civil service sphere set as project indicators, so it has been a large scale training program that took place in 2014 in Hungary. The following article shows the innovations included in this new approach model of post graduate training civil servants. 
An Experience of Science Theatre to Introduce Earth Interior and Natural Hazards to Children
Authors: Musacchio Gemma , Lanza Tiziana , D’Addezio Giuliana
Published: November 2015

The present paper describes an experience of science theatre addressed to children of primary and secondary school, with the main purpose of making them acquainted with a topic, the interior of the Earth, largely underestimated in compulsory school curricula worldwide. A not less important task was to encourage a positive attitude towards natural hazards that are here presented as an expression of our planet vitality. We conducted the experience with the help of a theatrical company specialized in shows for children, trying to merge scientific accuracy, entertainment and ethical issues. Several performances have been reiterated in different context, giving us the opportunity of conducting a preliminary survey with a public of different ages, skills and expectations. Results suggest that science theatre, while relying on creativity and emotional learning has the potential to raise children interest on the process of making science, on natural phenomena and may trigger a positive attitude on natural disasters reduction best practices.
Testing PID and MPC Performance for Mobile Robot Local Path-Following
Authors: Pacheco Lluis , Luo Ningsu
Published: November 2015

This paper outlines the online performance of a control law based on PID (proportional-integral-derivative) controllers and MPC (model predictive control) for mobile robot local path-following. Both techniques share the use of a set of different dynamic models. PID controllers are used for controlling the speed of the robot's wheels, while high level algorithms compute the necessary wheel speeds in order to generate a motion that approaches the vehicle towards the desired path. Meanwhile, local MPC is implemented by computing the horizon of suitable coordinates that arise from the set of command input combinations. Therefore, command speeds that correspond to the desired point are obtained by minimizing a cost function in which the population of the available coordinates is taken into account.
Robust Adaptive Control of a Free-Floating Space Robot System in Cartesian Space
Authors: Zhang Fuhai , Fu Yili , Qu Jiadi , Wang Shuguo
Published: November 2015

This paper presents a novel, robust, adaptive trajectory-tracking control scheme for the free-floating space robot system in Cartesian space. The dynamic equation of the free-floating space robot system in Cartesian space is derived from the augmented variable method. The proposed basic robust adaptive controller is able to deal with parametric and non-parametric uncertainties simultaneously. Another advantage of the control scheme is that the known and unknown external disturbance bounds can be considered using a modification of the parameter-estimation law. In addition, three cases are certified to achieve robustness for both parametric uncertainties and external disturbances. The simulation results show that the control scheme can ensure stable tracking of the desired trajectory of the end-effector.
APP and APLP2 interact with the synaptic release machinery and facilitate transmitter release at hippocampal synapses
Authors: Fanutza Tomas , Del Prete Dolores , Ford Michael J , Castillo Pablo E , D’Adamio Luciano
Published: November 2015

The amyloid precursor protein (APP), whose mutations cause familial Alzheimer’s disease, interacts with the synaptic release machinery, suggesting a role in neurotransmission. Here we mapped this interaction to the NH2-terminal region of the APP intracellular domain. A peptide encompassing this binding domain -named JCasp- is naturally produced by a γ-secretase/caspase double-cut of APP. JCasp interferes with the APP-presynaptic proteins interaction and, if linked to a cell-penetrating peptide, reduces glutamate release in acute hippocampal slices from wild-type but not APP deficient mice, indicating that JCasp inhibits APP function.The APP-like protein-2 (APLP2) also binds the synaptic release machinery. Deletion of APP and APLP2 produces synaptic deficits similar to those caused by JCasp. Our data support the notion that APP and APLP2 facilitate transmitter release, likely through the interaction with the neurotransmitter release machinery. Given the link of APP to Alzheimer’s disease, alterations of this synaptic role of APP could contribute to dementia.
Neuromodulation of excitatory synaptogenesis in striatal development
Authors: Kozorovitskiy Yevgenia , Peixoto Rui , Wang Wengang , Saunders Arpiar , Sabatini Bernardo L
Published: November 2015

Dopamine is released in the striatum during development and impacts the activity of Protein Kinase A (PKA) in striatal spiny projection neurons (SPNs). We examined whether dopaminergic neuromodulation regulates activity-dependent glutamatergic synapse formation in the developing striatum. Systemic in vivo treatment with Gαs-coupled G-protein receptors (GPCRs) agonists enhanced excitatory synapses on direct pathway striatal spiny projection neurons (dSPNs), whereas rapid production of excitatory synapses on indirect pathway neurons (iSPNs) required the activation of Gαs GPCRs in SPNs of both pathways. Nevertheless, in vitro Gαs activation was sufficient to enhance spinogenesis induced by glutamate photolysis in both dSPNs and iSPNs, suggesting that iSPNs in intact neural circuits have additional requirements for rapid synaptic development. We evaluated the in vivo effects of enhanced glutamate release from corticostriatal axons and postsynaptic PKA and discovered a mechanism of developmental plasticity wherein rapid synaptogenesis is promoted by the coordinated actions of glutamate and postsynaptic Gαs-coupled receptors.
Cell-cycle quiescence maintains Caenorhabditis elegans germline stem cells independent of GLP-1/Notch
Authors: Seidel Hannah S , Kimble Judith
Published: November 2015

Many types of adult stem cells exist in a state of cell-cycle quiescence, yet it has remained unclear whether quiescence plays a role in maintaining the stem cell fate. Here we establish the adult germline of Caenorhabditis elegans as a model for facultative stem cell quiescence. We find that mitotically dividing germ cells—including germline stem cells—become quiescent in the absence of food. This quiescence is characterized by a slowing of S phase, a block to M-phase entry, and the ability to re-enter M phase rapidly in response to re-feeding. Further, we demonstrate that cell-cycle quiescence alters the genetic requirements for stem cell maintenance: The signaling pathway required for stem cell maintenance under fed conditions—GLP-1/Notch signaling—becomes dispensable under conditions of quiescence. Thus, cell-cycle quiescence can itself maintain stem cells, independent of the signaling pathway otherwise essential for such maintenance.
The sensitivity of global climate to the episodicity of fire aerosol emissions
Authors: Clark Spencer K. , Ward Daniel S. , Mahowald Natalie M.
Published: November 2015

Here we explore the sensitivity of the global radiative forcing and climate response to the episodicity of fire emissions. We compare the standard approach used in present day and future climate modeling studies, in which emissions are not episodic but smoothly interpolated between monthly mean values and that contrast to the response when fires are represented using a range of approximations of episodicity. The range includes cases with episodicity levels matching observed fire day and fire event counts, as well as cases with extreme episodicity. We compare the different emissions schemes in a set of Community Atmosphere Model (CAM5) simulations forced with reanalysis meteorology and a set of simulations with online dynamics designed to calculate aerosol indirect effect radiative forcings. We find that using climatologically observed fire frequency improves model estimates of cloud properties over the standard scheme, particularly in boreal regions, when both are compared to a simulation with meteorologically synchronized emissions. Using these emissions schemes leads to a range in global indirect effect radiative forcing of fire aerosols between −1.1 and −1.3 W m−2. In cases with extreme episodicity, we see increased transport of aerosols vertically, leading to longer lifetimes and less negative indirect effect radiative forcings. In general, the range in climate impacts that results from the different realistic fire emissions schemes is smaller than the uncertainty in climate impacts due to other aspects of modeling fire emissions.
Spectroscopic properties of explosive volcanism within the Caloris basin with MESSENGER observations
Authors: Besse S. , Doressoundiram A. , Benkhoff J.
Published: November 2015

Volcanism on Mercury has been indisputably identified at various locations on the surface, by means of both effusive and explosive volcanism. Its characterization is crucial to understand the evolution of the planet, in particular the thermal evolution of the mantle, and the volatile content of the planet. This analysis presents a detailed view of the pyroclastic deposits of the Caloris basin. Observations from the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) are used to understand the spectral characteristics of the pyroclastic deposits, both in the visible and near‐infrared. Additional calibration steps are proposed to reconcile the difference of absolute reflectance between the visible (VIS) and near‐infrared (NIR) detectors. These calibration steps allow the use of the full spectral range of the MASCS instrument. Pyroclastic deposits exhibit a redder spectral slope in the VIS and NIR. This spectral slope diminishes toward the edge of the deposits to match that of Mercury's average surface. Spectral properties in the ultraviolet (UV) also change as a function of distance to the vent. Only the UV properties unambiguously separate the pyroclastic deposits from Mercury's average spectra. The spectral variations are consistent with a lower iron content of the pyroclastic deposits with respect to the average surface of Mercury, similar to what has been proposed for pyrolcastic deposits on the lunar surface. Nonetheless, given the limited illumination conditions diversity of the MASCS instrument, other causes such as grain size, space weathering, and bulk composition could also be accounted for the spectral variations. Variability of the pyroclastic deposits' properties within the entire basin are potentially identified between the three main clusters, and could be related to space weathering of deposits of different ages.
Influence of Pre‐Solution Treatment on Microstructure and Mechanical Properties of Mg–Gd–Nd–Zn–Zr Alloy Processed by ECAP
Authors: Liu Yong , Kang Zhi Xin , Zhang Jun Yi , Wang Fen , Li Yuan Yuan
Published: November 2015

Equal channel angular pressing (ECAP) works as a useful method for microstructure refinement and strength hardening. Billets of the as‐cast and solution‐treated Mg–Gd–Nd–Zn–Zr alloy are processed by ECAP to investigate influence of pre‐solution treatment on the microstructure and mechanical properties of the alloy. The average grain size is refined from 80 to 1.5 µm after eight passes at 375 °C. Both yield stress and ultimate tensile strength of the alloy in two conditions are improved after multi‐pass ECAP. The retained broken eutectics as well as precipitation produced during ECAP may provide a stronger strength. Compared to the as‐cast alloy, solution‐treated alloy possesses higher elongation after ECAP. The variation in strength and ductility can be explained by the texture modification and microstructure evolution.
Tuning the Charge Transfer in Fx‐TCNQ/Rubrene Single‐Crystal Interfaces
Authors: Krupskaya Yulia , Lezama Ignacio Gutiérrez , Morpurgo Alberto F.
Published: November 2015

Interfaces formed by two different organic semiconductors often exhibit a large conductivity, originating from transfer of charge between the constituent materials. The precise mechanisms driving charge transfer and determining its magnitude remain vastly unexplored, and are not understood microscopically. To start addressing this issue, we have performed a systematic study of highly reproducible single‐crystal interfaces based on rubrene (tetraphenylnaphthacene) and Fx‐TCNQ (fluorinated tetracyanoquinodimethane), a family of molecules whose electron affinity can be tuned by increasing the fluorine content. The combined analysis of transport and scanning Kelvin probe measurements reveals that the interfacial charge‐carrier density, resistivity, and activation energy correlate with the electron affinity of Fx‐TCNQ crystals, with a higher affinity resulting in larger charge transfer. Although the transport properties can be described consistently and quantitatively using a mobility‐edge model, we find that a quantitative analysis of charge transfer in terms of single‐particle band diagrams reveals a discrepancy ≈100 meV in the interfacial energy level alignment. We attribute the discrepancy to phenomena known to affect the energetics of organic semiconductors, which are neglected by a single‐particle description—such as molecular relaxation and bandgap renormalization due to screening. The systematic behavior of the Fx‐TCNQ/rubrene interfaces opens the possibility to investigate these phenomena experimentally, under controlled conditions.
Regimes of Exciton Transport in Molecular Crystals in the Presence of Dynamic Disorder
Authors: Aragó Juan , Troisi Alessandro
Published: November 2015

Thermal motions in molecular crystals cause substantial fluctuation of the excitonic coupling between neighboring molecules (dynamic disorder). The effect of such fluctuation on the exciton dynamics in two limiting cases is explored here, exemplified by the crystals of anthracene and a heteropentacene derivative. When the excitonic coupling is small in comparison with the electron–phonon coupling, the exciton diffusion is incoherent and the inclusion of excitonic coupling fluctuation does not alter the exciton physics but can improve the agreement between computed and experimental diffusion coefficients. For large excitonic couplings, when the transport becomes coherent, the thermal motions determine the diffusivity of the exciton, which can be several orders of magnitude larger than in the incoherent case. The coherent regime is less frequent but potentially of great technological importance.
Are Fluorescent Organic Nanoparticles Relevant Tools for Tracking Cancer Cells or Macrophages?
Authors: Faucon Adrien , Benhelli‐Mokrani Houda , Córdova Luis A. , Brulin Bénédicte , Heymann Dominique , Hulin Philippe , Nedellec Steven , Ishow Eléna
Published: November 2015

Strongly solvatochromic fluorophores are devised, containing alkyl chains and enable to self‐assemble as very bright fluorescent organic nanoparticles (FONs) in water (Φf = 0.28). The alkyl chains impart each fluorophore with strongly hydrophobic surroundings, causing distinct emission colors between FONs where the fluorophores are associated, and their disassembled state. Such color change is harnessed to assess the long‐term fate of FONs in both cancer cells and monocytes/macrophages. Disintegration of the orange‐emitting FONs by monocytes/macrophages is evidenced through the formation of micrometer green‐yellowish emitting vesicles. By contrast, cancer cells retain longer the integrity of organic nanoparticles. In both cases, no significant toxicity is detected, making FONs as valuable bioimaging agents for cell tracking with weak risks of deleterious accumulation and low degradation rate.
Sequential In Vitro Cyclization by Cytochrome P450 Enzymes of Glycopeptide Antibiotic Precursors Bearing the X‐Domain from Nonribosomal Peptide Biosynthesis
Authors: Brieke Clara , Peschke Madeleine , Haslinger Kristina , Cryle Max J.
Published: November 2015

The biosynthesis of the glycopeptide antibiotics, which include vancomycin and teicoplanin, relies on the interplay between the peptide‐producing non‐ribosomal peptide synthetase (NRPS) and Cytochrome P450 enzymes (P450s) that catalyze side‐chain crosslinking of the peptide. We demonstrate that sequential in vitro P450‐catalyzed cyclization of peptide substrates is enabled by the use of an NRPS peptide carrier protein (PCP)‐X di‐domain as a P450 recruitment platform. This study reveals that whilst the precursor peptide sequence influences the installation of the second crosslink by the P450 OxyAtei, activity is not restricted to the native teicoplanin peptide. Initial peptide cyclization is possible with teicoplanin and vancomycin OxyB homologues, and the latter displays excellent activity with all substrate combinations tested. By using non‐natural X‐domain substrates, bicyclization of hexapeptides was also shown, which demonstrates the utility of this method for the cyclization of varied peptide substrates in vitro.
Auf dem Weg zu neuartigen phosphorbasierten Architekturen: eine nicht‐katalysierte Methode zur Gewinnung von sechsgliedrigen Heterozyklen
Authors: Romero‐Nieto Carlos , López‐Andarias Alicia , Egler‐Lucas Carolina , Gebert Florian , Neus Jens‐Peter , Pilgram Oliver
Published: November 2015

Phosphorbasierte Heterozyklen ermöglichen Materialeigenschaften, die durch reine Kohlenstoffstrukturen nicht zugänglich sind. Die einzigartige Hybridisierung des Phosphors führt zu Elektronen‐akzeptierenden Eigenschaften, einer großen Zahl an Koordinationsreaktionen und ermöglicht zudem die Kontrolle über die elektronischen Eigenschaften durch Phosphor‐Post‐Funktionalisierung. Hier beschreiben wir nun eine neue nicht‐katalysierte Methode zur Synthese kondensierter sechsgliedriger Phosphorheterozyklen, insbesondere zur Synthese neuartiger Phosphaphenalene. Diese kondensierten Systeme weisen Vorteile von sowohl fünf‐ als auch sechsgliedrigen Phosphorheterozyklen auf und ermöglichen eine Serie vielseitiger Post‐Funktionalisierungsreaktionen. Diese Arbeit eröffnet somit neue Horizonte auf dem Gebiet der konjugierten Materialien.
Hierarchically Structured Nanomaterials for Electrochemical Energy Conversion
Authors: Trogadas Panagiotis , Ramani Vijay , Strasser Peter , Fuller Thomas F. , Coppens Marc‐Olivier
Published: November 2015

Hierarchical nanomaterials are highly suitable as electrocatalysts and electrocatalyst supports in electrochemical energy conversion devices. The intrinsic kinetics of an electrocatalyst are associated with the nanostructure of the active phase and the support, while the overall properties are also affected by the mesostructure. Therefore, both structures need to be controlled. A comparative state‐of‐the‐art review of catalysts and supports is provided along with detailed synthesis methods. To further improve the design of these hierarchical nanomaterials, in‐depth research on the effect of materials architecture on reaction and transport kinetics is necessary. Inspiration can be derived from nature, which is full of very effective hierarchical structures. Developing fundamental understanding of how desired properties of biological systems are related to their hierarchical architecture can guide the development of novel catalytic nanomaterials and nature‐inspired electrochemical devices.
Endoperoxides Revealed as Origin of the Toxicity of Graphene Oxide
Authors: Pieper Hanna , Chercheja Serghei , Eigler Siegfried , Halbig Christian E. , Filipovic Milos R. , Mokhir Andriy
Published: November 2015

Potential biomedicinal applications of graphene oxide (GO), for example, as a carrier of biomolecules or a reagent for photothermal therapy and biosensing, are limited by its cytotoxicity and mutagenicity. It is believed that these properties are at least partially caused by GO‐induced oxidative stress in cells. However, it is not known which chemical fragments of GO are responsible for this unfavorable effect. We generated four GOs containing variable redox‐active groups on the surface, including Mn2+, C‐centered radicals, and endoperoxides (EPs). A comparison of the abilities of these materials to generate reactive oxygen species in human cervical cancer cells revealed that EPs play a crucial role in GO‐induced oxidative stress. These data could be applied to the rational design of biocompatible nontoxic GOs for biomedical applications.