bluuebunny/crossref_metadata_2025 huggingface dataset:
Adaptive impedance control of uncertain robot manipulators with saturation effect based on dynamic surface technique and self-recurrent wavelet neural networks
Authors: Hamedani Mohammad Hossein , Zekri Maryam , Sheikholeslam Farid
Published: October 2018

Saturation nonlinearities, among the known challenges in control engineering, are ubiquitous in robotic systems and can lead to stability and performance degradation. In this paper, an adaptive dynamic surface impedance (ADSI) control approach is developed for an n-link robotic manipulator by employing self-recurrent wavelet neural networks (SRWNNs) in order to overcome the saturation effect. The proposed control approach is inspired by the theory of dynamic surface control (DSC) and SRWNNs. As a novel application of the dynamic surface method to obtain a simple structure, the target impedance is formulated in the state–space, and effective dynamic surfaces are defined to track the desired impedance behavior. In fact, DSC is used to force the robot manipulator to track the desired impedance, while the robot interacts with an environment. In addition, SRWNNs are applied to approximate the parametric uncertainties and external disturbances in the robot dynamical model. Self-feedback neurons are embedded as memory units in SRWNNs to model the sudden dynamic jumps of the environment. Using Lyapunov's method, an ADSI controller is designed, and adaptation laws are induced to guarantee the stability of the closed-loop system. Finally, simulations are conducted to verify the proper performance of the proposed approach for removing the saturation effect and tracking the target impedance. It is worth noting that the simulation results indicate the robustness of the controller against uncertainties and external disturbances.
English in the linguistic landscape of a northern Jordanian city
Authors: Salameh Alomoush Omar Ibrahim
Published: October 2018

The concept of the linguistic landscape (henceforth LL) includes all linguistic objects that characterise public environments, including but not limited to warning signs, instructions, public road signs, advertising billboards and posters, street names, graffiti, and notices on government and nongovernment buildings (Landry & Bourhis, 1997: 25). There is no doubt that the LL is a very significant domain for the examination of the cultural, socio-political, and economic changes that occur in a speech community (Backhaus, 2007; Gorter, 2017; Jaworski & Thurlow, 2010; Pakarinen & Björklund, 2017). The use of the LL approach to analyse how English is constructed and negotiated in the Jordanian context can provide new and important insights and evidence into the wide spread of English in a little-explored area, and can contribute to our understanding of the use of English as a global language.
A computational tool for creative idea generation based on analogical reasoning and ontology
Authors: Han Ji , Shi Feng , Chen Liuqing , Childs Peter R.N.
Published: October 2018

Analogy is a core cognition process used to produce inferences as well as new ideas using previous knowledge and experience. Ontology is a formal representation of a set of domain concepts and their relationships. The use of analogy and ontology in design activities to support design creativity have previously been explored. This paper explores an approach to construct ontologies with sufficient richness and coverage to support reasoning over real-world datasets for prompting creative idea generation. This approach has been implemented into a computational tool for assisting designers in generating creative ideas during the early stages of design. The tool, called “the Retriever”, has been developed based on ontology by embracing the aspects of analogical reasoning. A case study has indicated that the tool can be effective and useful for idea generation. The results have indicated that the tool, in its current formulation, can significantly improve the fluency and flexibility of idea generation and the usefulness of ideas, as well as slightly increase the originality of ideas, for the case study concerned.
Good idea! Or, good presentation? Examining the effect of presentation on perceived quality of concepts
Authors: Kwon Jieun , Kudrowitz Barry
Published: October 2018

In the product design realm, designers often use presentations to convey certain ideas about a product or a specific stage of the design process. The popular forms of presentation include verbal pitching, two-dimensional drawing, and prototyping. The clients, investigators, and other audiences rely on such presentations to evaluate an idea. Popular idea evaluation assessment tools, such as the consensual assessment technique, utilize such interactions. On the other hand, numerous pieces of literature state that the audiences are heavily influenced by the quality of presentation when evaluating the worth of the product being presented. In this study, we examine if the audience is able to discriminate between the quality of the presentation and the quality of the idea being presented. A total of 613 ideas were evaluated over a 4-year period during a specific product design class at different phases in the design process. The result shows that no matter the kind of presentation tool used, the presentation quality ratings and the idea value ratings had a very strong positive correlation despite the explicit instructions to reviewers to separate presentation quality from concept quality. Our additional analysis shows that such a pattern did not change during the different phases of the design process.
The impacts of deglaciation and human activity on the taxonomic structure of prokaryotic communities in Antarctic soils on King George Island
Authors: Pershina E.V. , Ivanova E.A. , Abakumov E.V. , Andronov E.E.
Published: October 2018

The soil microbiome was investigated at environmentally distinct locations on King George Island in the South Shetland Islands (Antarctic Peninsula) using 16 S rRNA gene pyrosequencing. The taxonomic composition of the soil prokaryotes (bacteria and archaea) was evaluated at three sites representing human-disturbed soils (Bellingshausen Station) and soils undergoing different stages of deglaciation (fresh and old moraines located near Ecology Glacier). The taxonomic analysis revealed 20 bacterial and archaeal phyla, among which Proteobacteria (29.6%), Actinobacteria (25.3%), Bacteroidetes (15.8%), Cyanobacteria (11.2%), Acidobacteria (4.9%) and Verrucomicrobia (4.5%) comprised most of the microbiome. In a beta-diversity analysis, the samples formed separate clusters. The Bellingshausen Station samples were characterized by an increased amount ofNostocsp. andJanibactersp. Although the deglaciation history had less of an effect on the soil microbiome, the early stages of deglaciation (Sample 1) had a higher proportion of bacteria belonging to the families Xanthomonadaceae, Sphingomonadaceae and Nocardioidaceae, whereas the older moraines (Sample 2) were enriched with Chthoniobacteriacae and N1423WL. Solirubrobacteriales, Gaiellaceae and Chitinophagaceae bacteria were present in both stages of deglaciation, characterized by genus-level differences. Taxonomic analysis of the abundant operational taxonomic units (OTUs) revealed both endemic (Marisediminicola antarctica,Hymenobacter glaciei) and cosmopolitan bacterial species in the microbiomes.
How robust are the temperature trends on the Antarctic Peninsula?
Authors: Gonzalez Sergi , Fortuny Didac
Published: October 2018

The upward evolution of temperatures in the Antarctic Peninsula has weakened and even reversed in the last two decades. Due to the long-term variability in the region it is not easy to assess whether recent cooling trends are consistent with the internal variability or not. For this reason, this paper assesses the robustness of the trends by analysing their sensitivity with respect to the period selected. Every possible temperature trend in the interval 1958–2016 has been calculated and displayed in a two-dimensional parameter diagram. The results suggest that the warming observed in the Antarctic Peninsula since 1958 is quite robust, as all periods longer than 30 years exhibit statistically significant changes, especially in summer (with lower magnitude and higher significance) and autumn and winter (with larger magnitude and lower significance). Periods shorter than 30 years exhibit alternations of warming and cooling periods, and therefore do not represent robust trends even if they are statistically significant. Consequently, the recent 20-year cooling trend cannot be considered at the moment as evidence of a shift in the overall sign of the trend.
Neighborhood structural characteristics and Mexican-origin adolescents’ development
Authors: White Rebecca M. B. , Zeiders Katharine H. , Safa M. Dalal
Published: October 2018

Ethnic–racial and socioeconomic residential segregation are endemic in the United States, representing societal-level sociocultural processes that likely shape development. Considered alongside communities’ abilities to respond to external forces, like stratification, in ways that promote youth adaptive functioning and mitigate maladaptive functioning, it is likely that residence in segregated neighborhoods during adolescence has both costs and benefits. We examined the influences that early adolescents’ neighborhood structural characteristics, including Latino concentration and concentrated poverty, had on a range of developmentally salient downstream outcomes (i.e., internalizing, externalizing, prosocial behaviors, and ethnic–racial identity resolution) via implications for intermediate aspects of adolescents’ community participation and engagement (i.e., ethnic–racial identity exploration, ethnic–racial discrimination from peers, and school attachment). These mediational mechanisms were tested prospectively across three waves (Mage w1-w3 = 12.79, 15.83, 17.37 years, respectively) in a sample of 733 Mexican-origin adolescents (48.8% female). We found higher neighborhood Latino concentration during early adolescence predicted greater school attachment and ethnic–racial identity exploration and lower discrimination from peers in middle adolescence. These benefits, in turn, were associated with lower externalizing and internalizing and higher ethnic–racial identity resolution and prosocial behaviors in late adolescence. Findings are discussed relative to major guidelines for integrating culture into development and psychopathology.
Patterns of Political Secularism in Italy and Turkey: The Vatican and the Diyanet to the Test of Politics
Authors: Ozzano Luca , Maritato Chiara
Published: October 2018

For centuries, Rome and Istanbul have been representing and epitomizing two empires and two entities with both significant spiritual and temporal power: the Papacy and the Caliphate. During the 19th and the 20th centuries, these institutions underwent significant changes in a context of state secularization: in the case of the Papacy, there was a loss of temporal power and its “reduction” to a mainly moral authority; the Caliphate, on the other hand, was abolished after World War I, succeeded by the Presidency of Religious Affairs (Diyanet), a bureaucratic body under state control, founded in the era of Kemalist secularism. Despite these changes, today both institutions still play a significant role in the public life and public policies of the Italian and the Turkish republics. While the Vatican is able to influence the Italian public sphere and public discourse through both its influence on common people and its lobbying activities in relation to political decision-makers, in Turkey the Diyanet has become the main tool in the reshaping of Turkish society (both by the Kemalists and, later, by Erdoğan's AKP). This paper will analyze their influence on the two countries’ public policies in relation to religious pluralism and to family-related issues, to show how different ideas of secularism, institutional arrangements, and historical paths have led to a very different role of the two institutions in the Italian and Turkish political systems.
Onlinebasierte Diagnostik mathematischer Kompetenzen: Möglichkeiten und Grenzen
Authors: Kuhn Jörg-Tobias , Schwenk Christin
Published: October 2018

Zusammenfassung. Im vorliegenden Beitrag wird auf Kriterien eingegangen, die eine computer- bzw. onlinebasierte Diagnostik mathematischer Kompetenzen erfüllen muss, damit für Grundschulkinder mit einer Rechenstörung optimale Fördermaßnahmen abgeleitet werden können. Testverfahren, die auf neuropsychologischer oder entwicklungspsychologischer Grundlage entwickelt wurden und die einen Schwerpunkt auf die Erfassung mathematischer Vorläuferfertigkeiten legen, lassen sich gut mit einem onlinebasierten Vorgehen verbinden und liefern gleichzeitig für die Förderplanung relevante diagnostische Information. Qualitativ-diagnostische Verfahren, die mathematische Denkprozesse beschreiben sollen, sind für die computerbasierte Administration eher ungeeignet, während vorwiegend curriculumorientierte Testverfahren für die Förderplanung oft zu wenig Information bieten. Computerbasierte Varianten existierender Papier-Bleistift-basierter mathematischer Testverfahren benötigen in der Regel eine Neunormierung oder zumindest eine Sicherstellung der Äquivalenz, zudem müssen grundlegende psychometrische Kriterien erfüllt sein. Neben einer Vorstellung geeigneter Testverfahren werden allgemeine Vor- und Nachteile onlinebasierter Diagnostik diskutiert.
Magnetic Fluctuations and Turbulence in the Venusian Magnetosheath Downstream of Different Types of Bow Shock
Authors: Xiao S. D. , Zhang T. L. , Vörös Z.
Published: October 2018

We statistically examine the characteristic scaling features of fluctuations in the dayside Venusian magnetosheath downstream of different types, quasi‐parallel (Q∥) and quasi‐perpendicular (Q⊥), of bow shock based on Venus Express data. We found that magnetic fluctuations have different characteristic scaling features downstream of Q∥ and Q⊥ bow shocks. Although the Venusian dayside magnetosheath is much thinner than the Earth magnetosheath, fully developed turbulence can be still observed downstream of the Q∥ bow shock, while the turbulence is not dominant downstream of Q⊥ bow shock. The type of bow shock plays an important role in the characteristic scaling features of downstream magnetic fluctuations. That means that the Q∥ IMF might be a source of the turbulence in Venusian magnetosheath.
Multiple Satellite Analysis of the Earth's Thermosphere and Interplanetary Magnetic Field Variations Due to ICME/CIR Events During 2003–2015
Authors: Krauss S. , Temmer M. , Vennerstrom S.
Published: October 2018

We present a refined statistical analysis based on interplanetary coronal mass ejections (ICMEs) as well as corotating interaction regions (CIRs) for the time period 2003–2015 to estimate the impact of different solar wind types on the geomagnetic activity and the neutral density in the Earth's thermosphere. For the time‐based delimitation of the events, we rely on the catalog maintained by Richardson and Cane and the corotating interaction region lists provided by S. Vennerstrom and Jian et al. (2011, https://doi.org/10.1007/s11207‐011‐9737‐2). These archives are based on in situ measurements from the Advanced Composition Explorer and/or the Wind spacecraft. On this basis, we thoroughly investigated 196 Earth‐directed ICME and 195 CIR events. To verify the impact on the Earths thermosphere we determined neutral mass densities by using accelerometer measurements collected by the low‐Earth‐orbiting satellites Gravity Recovery and Climate Experiment and Challenging Minisatellite Payload. Subsequently, the atmospheric densities are related to characteristic ICME parameters. In this process a new calibration method has been examined. Since increased solar activity may lead to a decrease of the satellites orbital altitude we additionally assessed the orbital decay for each of the events and satellites. The influence of CIR events is in the same range of magnitude as the majority of the ICMEs (186 out of 196). Even though, the extended investigation period between 2011 and 2015 has a lack of extreme solar events the combined analysis reveals comparable correlation coefficients between the neutral densities and the various ICME and geomagnetic parameters (mostly >0.85). The evaluation of orbit decay rates at different altitudes revealed a high dependency on the satellite actual altitude.
Edge Plasma Enhancements of Equatorial Plasma Depletions Observed by All‐Sky Imager and the C/NOFS Satellite
Authors: Wu Kun , Xu Jiyao , Xiong Chao , Yuan Wei
Published: October 2018

Equatorial plasma depletions (EPDs) appearing at nighttime low latitudes were widely studied before. The edge plasma enhancements of equatorial plasma depletions (EPEEPDs) were repeatedly observed by the all‐sky imager and the Communications/Navigation Outage Forecasting System (C/NOFS) satellite. However, the two‐dimensional structures of EPEEPDs have not been well addressed. In this study, the airglow observations from one all‐sky imager showed that the EPEEPDs occurred only in the east and west edges of EPDs but not at the poleward edge as earlier reported from the in situ measurements of low Earth orbit satellites. Four‐year observations (2012–2015) from both our all‐sky imager and the C/NOFS satellite have been analyzed. Compared to the airglow images, the in situ observation from C/NOFS showed that the edge plasma enhancements appeared to be less prominent with respect to the background, but both showed that the plasma enhancement was a high‐incidence phenomenon, and the average incidence reached about 82% during days with EPDs observed. The occurrence of EPEEPDs showed similar characteristic as EPDs, such as the longitudinal dependences. The zonal extension of EPEEPDs showed different scale characteristics at different altitudes; its zonal extent varied with its altitudinal dependence. Four‐year observations from C/NOFS satellite showed that the occurrence of EPEEPDs peaked during 20:00–22:00 LT. The result from all‐sky imager showed that the relative intensity enhancement appeared contemporaneously, with maximal relative intensity exceeding 90%. We suggest that the generation mechanism of EPEEPDs is possibly related to the polarized electric field of EPDs. The plasma is more likely to be redistributed and exhibits as depletion and enhancement.
The Impact of Tides on Simulated Landfast Ice in a Pan‐Arctic Ice‐Ocean Model
Authors: Lemieux Jean‐François , Lei Ji , Dupont Frédéric , Roy François , Losch Martin , Lique Camille , Laliberté Frédéric
Published: October 2018

The impact of tides on the simulated landfast ice cover is investigated. Pan‐Arctic simulations are conducted with an ice‐ocean (CICE‐NEMO) model with a modified rheology and a grounding scheme. The reference experiment (without tides) indicates there is an overestimation of the extent of landfast ice in regions of strong tides such as the Gulf of Boothia, Prince Regent Inlet, and Lancaster Sound. The addition of tides in the simulation clearly leads to a decrease of the extent of landfast ice in some tidally active regions. This numerical experiment with tides is more in line with observations of landfast ice in all the regions studied. Thermodynamics and changes in grounding cannot explain the lower landfast ice area when tidal forcing is included. We rather demonstrate that this decrease in the landfast ice extent is dynamically driven by the increase of the ocean‐ice stress due to the tides.
Impact of Biomass Burning and Vertical Mixing of Residual‐Layer Aged Plumes on Ozone in the Yangtze River Delta, China: A Tethered‐Balloon Measurement and Modeling Study of a Multiday Ozone Episode
Authors: Xu Zhengning , Huang Xin , Nie Wei , Shen Yicheng , Zheng Longfei , Xie Yuning , Wang Tianyi , Ding Ke , Liu Lixia , Zhou Derong , Qi Ximeng , Ding Aijun
Published: October 2018

Ozone (O3) is one of the most important trace gases in the troposphere because of its impact on human health, crop yield, climate change, and atmospheric oxidizing capacity. In recent years, China has suffered from deleterious O3 pollution in many regions, especially in eastern China during summer. However, understanding the causes of high O3 pollution episodes is still limited because existing measurements were mainly conducted at the surface level. In this study, we conducted an intensive tethered‐balloon measurement at the Station for Observing Regional Processes of the Earth System in the Yangtze River Delta during a multiday O3 episode in mid‐June 2014, with the highest hourly surface O3 record (142 ppbv) at the station in 2014. By integrating available ground‐based, remote sensing and aircraft measurement data together with chemical transport modeling and Lagrangian dispersion modeling, we carried out a comprehensive analysis of the main source and formation mechanism for two typical days during the multiday O3 episode. On 11 June, agricultural straw burning in the north significantly enhanced O3 concentration (40–50 ppbv) above the planetary boundary layer (PBL) over Nanjing and further influenced the downwind surface O3 in the following days. On 14 June, regional photochemically aged air masses from city clusters in the Yangtze River Delta substantially influenced early morning ground O3 concentrations by vertical mixing from the residual layer and contributed to PBL daytime O3 buildup. This study provides a clear picture of the transport and mixing of O3 and relevant pollutants in the PBL from different sources and highlights the significance of regional emission control in the mitigation of photochemical pollution in eastern China.
Geology of Hebes Chasma, Mars: 1. Structure, Stratigraphy, and Mineralogy of the Interior Layered Deposits
Authors: Schmidt Gene , Fueten Frank , Stesky Robert , Flahaut Jessica , Hauber Ernst
Published: October 2018

Hebes Chasma is an 8‐km deep, 126 by 314 km, isolated basin that is partially filled with massive deposits of water‐altered strata called interior layered deposits (ILDs). By analyzing the ILD's structure, stratigraphy, and mineralogy, a depositional history of Hebes Chasma is interpreted. Three distinct ILD units were found and are informally referred to as the Lower, Upper, and Late ILD. These units are distinguished by their layer thicknesses, layer attitudes, mineralogies, and erosional landforms. The Lower and Upper ILDs comprise the chasma's 7.5‐km tall, 120 by 43 km, central mound, and the Late ILD is located in the valley between the central mound and the chasma's northern wall. A horizontal unconformity separates the Lower and Upper ILDs, and layer attitudes revealed large‐scale shallow folding within the Lower ILD. All ILDs are characterized by both monohydrated and polyhydrated sulfates signatures. Erosional landforms such as hummocks, polygons, and debris flows suggest past glacial activity within the chasma. A scenario involving several ash fall events during various stages of chasma formation is proposed as the dominant setting throughout Hebes' geologic history.
Using Machine Learning to Predict Geomorphic Disturbance: The Effects of Sample Size, Sample Prevalence, and Sampling Strategy
Authors: Perry George L. W. , Dickson Mark E.
Published: October 2018

Advances in data acquisition and statistical methodology have led to growing use of machine‐learning methods to predict geomorphic disturbance events. However, capturing the data required to parameterize these models is challenging because of expense or, more fundamentally, because the phenomenon of interest occurs infrequently. Thus, it is important to understand how the nature of the data used to train predictive models influences their performance. Using a database of cliff failure prediction and associated covariates from Auckland, New Zealand, we assess the performance of seven machine‐learning algorithms under different sampling strategies. Three sampling components are investigated: (i) the number of data points used in model training (sample size), (ii) the prevalence of occurrences (presences) in the data, and (iii) random versus spatial sampling strategy. Across the seven algorithms, small sample sizes can produce models that perform relatively well, especially if the prime concern is identifying key predictors rather than quantifying risk or predicting categorical outcome. Our analyses show that for the same effort (i.e., number of samples), sampling around multiple locations provides better predictions than sampling at just one or a few locations. Predictive performance may be further improved by considering issues such as the nature of what absences actually represent and paying careful attention to decisions about hyperparameter tuning, training‐testing data splits, and threshold optimization. It is well known that big data can inform complex data‐driven modeling, but here we show that careful sampling can facilitate informative event prediction even from small data.
From Remotely‐Sensed Data of Norwegian Boreal Forests to Fast and Flexible Models for Estimating Surface Albedo
Authors: Hu Xiangping , Cherubini Francesco , Vezhapparambu Sajith , Strømman Anders Hammer
Published: October 2018

The importance to consider changes in surface albedo and go beyond simple carbon accounting when assessing climate change impacts of forestry and land use activities is increasingly recognized. However, representation of albedo changes in climate models is complex and highly parameterized, thereby limiting their applications in climate impact studies. The availability of simple yet reliable albedo models can enhance consideration of albedo changes in land use studies. We propose a set of simplified models for estimating surface albedo in a boreal forest. We process and harmonize datasets of remotely‐sensed albedo estimates, forest structure parameters, and meteorological records for different forest locations in Norway. By combining linear unmixing with nonlinear programming, we simultaneously produce albedo estimates at the same resolution of the land cover dataset (16 m, notably higher than satellite retrievals) and a variety of flexible models for albedo predictions. We test different combinations of functional forms, variables, and constraints, including variants specific for snow‐free conditions. We find that models capture the seasonal pattern of surface albedo and the interactive effect of forest structures and meteorological parameters, and many of them show good statistical scores. The cross‐validation exercise shows that the models derived from one area perform reasonably well when applied to other forested areas in Norway, regardless of the temporal and spatial scales. By incorporating changes in forest structure and climate conditions as explicit variables, these models are simple to be used in different applications aiming at estimating albedo changes from forest management and climate change.
Tunable optical spin Hall effect in a liquid crystal microcavity
Authors: Lekenta Katarzyna , Król Mateusz , Mirek Rafał , Łempicka Karolina , Stephan Daniel , Mazur Rafał , Morawiak Przemysław , Kula Przemysław , Piecek Wiktor , Lagoudakis Pavlos G. , Piętka Barbara , Szczytko Jacek
Published: October 2018

The spin Hall effect, a key enabler in the field of spintronics, underlies the capability to control spin currents over macroscopic distances. The effect was initially predicted by D'Yakonov and Perel1 and has been recently brought to the foreground by its realization in paramagnetic metals by Hirsch2 and in semiconductors3 by Sih et al. Whereas the rapid dephasing of electrons poses severe limitations to the manipulation of macroscopic spin currents, the concept of replacing fermionic charges with neutral bosons such as photons in stratified media has brought some tangible advances in terms of comparatively lossless propagation and ease of detection4–7. These advances have led to several manifestations of the spin Hall effect with light, ranging from semiconductor microcavities8,9 to metasurfaces10. To date the observations have been limited to built-in effective magnetic fields that underpin the formation of spatial spin currents. Here we demonstrate external control of spin currents by modulating the splitting between transverse electric and magnetic fields in liquid crystals integrated in microcavities.
Sulfurimonas subgroup GD17 cells accumulate polyphosphate under fluctuating redox conditions in the Baltic Sea: possible implications for their ecology
Authors: Möller Lars , Laas Peeter , Rogge Andreas , Goetz Florian , Bahlo Rainer , Leipe Thomas , Labrenz Matthias
Published: October 2018

The central Baltic Sea is characterized by a pelagic redox zone exhibiting high dark CO2 fixation rates below the chemocline. These rates are mainly driven by chemolithoautotrophic and denitrifying Sulfurimonas GD17 subgroup cells which are motile and fast-reacting r-strategists. Baltic Sea redox zones are unstable and a measurable overlap of nitrate and reduced sulfur, essential for chemosynthesis, is often only available on small scales and short times due to local mixing events. This raises the question of how GD17 cells gain access to electron donors or acceptors over longer term periods and under substrate deficiency. One possible answer is that GD17 cells store high-energy-containing polyphosphate during favorable nutrient conditions to survive periods of nutrient starvation. We used scanning electron microscopy with energy-dispersive X-ray spectroscopy to investigate potential substrate enrichments in single GD17 cells collected from Baltic Sea redox zones. More specific substrate enrichment features were identified in experiments using Sulfurimonas gotlandica GD1T, a GD17 representative. Sulfurimonas cells accumulated polyphosphate both in situ and in vitro. Combined genome and culture-dependent analyses suggest that polyphosphate serves as an energy reservoir to maintain cellular integrity at unfavorable substrate conditions. This redox-independent energy supply would be a precondition for sustaining the r-strategy lifestyle of GD17 and may represent a newly identified survival strategy for chemolithoautotrophic prokaryotes occupying eutrophic redox zones.
Antiepileptic drug carbamazepine promotes horizontal transfer of plasmid-borne multi-antibiotic resistance genes within and across bacterial genera
Authors: Wang Yue , Lu Ji , Mao Likai , Li Jie , Yuan Zhiguo , Bond Philip L , Guo Jianhua
Published: October 2018

Antibiotic resistance is a severe global threat for public health, causing around 700,000 deaths per year. Horizontal gene transfer (HGT) is one of the most significant pathways to disseminate antibiotic resistance. It is commonly acknowledged that sub-minimum inhibition concentrations of antibiotics are major contributors in promoting antibiotic resistance through HGT. Pharmaceuticals are occurring in our environments at increased levels, yet little is known whether non-antibiotic pharmaceuticals cause or accelerate the dissemination of antibiotic resistance. Here, we report for the first time that the antiepileptic drug, carbamazepine, promotes conjugative transfer of antibiotic resistance genes. It was seen that environmentally relevant concentrations of carbamazepine (e.g., 0.05 mg/L) significantly enhanced the conjugative transfer of multiresistance genes carried by plasmid within and across bacterial genera. The underlying mechanisms of the enhanced HGT were revealed by detecting oxidative stress and cell membrane permeability, in combination with MinION DNA sequencing, genome-wide RNA sequencing, and proteomic analysis. Carbamazepine induced a series of acute responses, including increased levels of reactive oxygen species, the SOS response; increased cell membrane permeability, and pilus generation. Expressional levels of genes related to these processes were significantly upregulated during carbamazepine exposure. Given that HGT occurs widely among different species in various environments, these findings are an early warning for a wide assessment of the roles of non-antibiotic pharmaceuticals in the spread of antibiotic resistance.
Modeling microbial communities from atrazine contaminated soils promotes the development of biostimulation solutions
Authors: Xu Xihui , Zarecki Raphy , Medina Shlomit , Ofaim Shany , Liu Xiaowei , Chen Chen , Hu Shunli , Brom Dan , Gat Daniella , Porob Seema , Eizenberg Hanan , Ronen Zeev , Jiang Jiandong , Freilich Shiri
Published: October 2018

Microbial communities play a vital role in biogeochemical cycles, allowing the biodegradation of a wide range of pollutants. The composition of the community and the interactions between its members affect degradation rate and determine the identity of the final products. Here, we demonstrate the application of sequencing technologies and metabolic modeling approaches towards enhancing biodegradation of atrazine—a herbicide causing environmental pollution. Treatment of agriculture soil with atrazine is shown to induce significant changes in community structure and functional performances. Genome-scale metabolic models were constructed for Arthrobacter, the atrazine degrader, and four other non-atrazine degrading species whose relative abundance in soil was changed following exposure to the herbicide. By modeling community function we show that consortia including the direct degrader and non-degrader differentially abundant species perform better than Arthrobacter alone. Simulations predict that growth/degradation enhancement is derived by metabolic exchanges between community members. Based on simulations we designed endogenous consortia optimized for enhanced degradation whose performances were validated in vitro and biostimulation strategies that were tested in pot experiments. Overall, our analysis demonstrates that understanding community function in its wider context, beyond the single direct degrader perspective, promotes the design of biostimulation strategies.
A novel rat model of comorbid PTSD and addiction reveals intersections between stress susceptibility and enhanced cocaine seeking with a role for mGlu5 receptors
Authors: Schwendt Marek , Shallcross John , Hadad Natalie A. , Namba Mark D. , Hiller Helmut , Wu Lizhen , Krause Eric G. , Knackstedt Lori A.
Published: October 2018

Abstract

PTSD is highly comorbid with cocaine use disorder (CUD), and cocaine users with PTSD + CUD are more resistant to treatment. Here we sought to develop a rat model of PTSD + CUD in order to identify the neurobiological changes underlying such comorbidity and screen potential medications for reducing cocaine seeking in the PTSD population. We utilized a predator scent stress model of PTSD, wherein rats received a single exposure to the fox pheromone 2,5-dihydro-2,4,5-trimethylthiazoline (TMT). One week after TMT exposure, stress-susceptible (susceptible), intermediate, and resilient phenotypes were detected and were consistent with behavioral, corticosterone, and gene expression profiles 3 weeks post TMT. We assessed phenotypic differences in cocaine self-administration, extinction, and cue-primed reinstatement. Susceptible rats exhibited deficits in extinction learning and increased cue-primed reinstatement that was not prevented by Ceftriaxone, an antibiotic that consistently attenuates the reinstatement of cocaine seeking. TMT-exposed resilient rats displayed increased mGlu5 gene expression in the amygdala and medial prefrontal cortex and did not display the enhanced cocaine seeking observed in susceptible rats. Combined treatment with the mGlu5 positive allosteric modulator 3-Cyano-N-(1,3-diphenyl-1 H-pyrazol-5-yl)benzamide (CDPPB), fear extinction, and ceftriaxone prevented the reinstatement of cocaine seeking in susceptible rats with fear extinction an important mediating condition. These results highlight the need for animal models of PTSD to consider stress-responsivity, as only a subset of trauma-exposed individuals develop PTSD and these individuals likely exhibit distinct neurobiological changes compared with trauma-exposed populations who are resilient to stress. This work further identifies glutamate homeostasis and mGlu5 as a target for treating relapse in comorbid PTSD-cocaine addiction.
Tetratricopeptide repeat domain 7A is a nuclear factor that modulates transcription and chromatin structure
Authors: El-Daher Marie-Therese , Cagnard Nicolas , Gil Marine , Da Cruz Marie Chansel , Leveau Claire , Sepulveda Fernando , Zarhrate Mohammed , Tores Frédéric , Legoix Patricia , Baulande Sylvain , de Villartay Jean Pierre , Almouzni Geneviève , Quivy Jean-Pierre , Fischer Alain , de Saint Basile Geneviève
Published: October 2018

A loss-of-function mutation in tetratricopeptide repeat domain 7A (TTC7A) is a recently identified cause of human intestinal and immune disorders. However, clues to related underlying molecular dysfunctions remain elusive. It is now shown based on the study of TTC7A-deficient and wild-type cells that TTC7A is an essential nuclear protein. It binds to chromatin, preferentially at actively transcribed regions. Its depletion results in broad range of epigenomic changes at proximal and distal transcriptional regulatory elements and in altered control of the transcriptional program. Loss of WT_TTC7A induces general decrease in chromatin compaction, unbalanced cellular distribution of histones, higher nucleosome accessibility to nuclease digestion along with genome instability, and reduced cell viability. Our observations characterize for the first time unreported functions for TTC7A in the nucleus that exert a critical role in chromatin organization and gene regulation to safeguard healthy immune and intestinal status.
Identifying triplet pathways in dilute pentacene films
Authors: Lubert-Perquel Daphné , Salvadori Enrico , Dyson Matthew , Stavrinou Paul N. , Montis Riccardo , Nagashima Hiroki , Kobori Yasuhiro , Heutz Sandrine , Kay Christopher W. M.
Published: October 2018

Building efficient triplet-harvesting layers for photovoltaic applications requires a deep understanding of the microscopic properties of the components involved and their dynamics. Singlet fission is a particularly appealing mechanism as it generates two excitons from a single photon. However, the pathways of the coupled triplets into free species, and their dependence on the intermolecular geometry, has not been fully explored. In this work, we produce highly ordered dilute pentacene films with distinct parallel and herringbone dimers and aggregates. Using electron paramagnetic resonance spectroscopy, we provide compelling evidence for the formation of distinct quintet excitons in ambient conditions, with intrinsically distinctive electronic and kinetic properties. We find that the ability of quintets to separate into free triplets is promoted in the parallel dimers and this provides molecular design rules to control the triplets, favouring either enhanced photovoltaic efficiency (parallel) or strongly bound pairs that could be exploited for logic applications (herringbone).
Charging dynamics of an individual nanopore
Authors: Tivony Ran , Safran Sam , Pincus Philip , Silbert Gilad , Klein Jacob
Published: October 2018

Meso-porous electrodes (pore width « 1 µm) are a central component in electrochemical energy storage devices and related technologies, based on the capacitive nature of electric double-layers at their surfaces. This requires that such charging, limited by ion transport within the pores, is attained over the device operation time. Here we measure directly electric double layer charging within individual nano-slits, formed between gold and mica surfaces in a surface force balance, by monitoring transient surface forces in response to an applied electric potential. We find that the nano-slit charging time is of order 1 s (far slower than the time of order 3 × 10−2 s characteristic of charging an unconfined surface in our configuration), increasing at smaller slit thickness, and decreasing with solution ion concentration. The results enable us to examine critically the nanopore charging dynamics, and indicate how to probe such charging in different conditions and aqueous environments.
Spectral field mapping in plasmonic nanostructures with nanometer resolution
Authors: Krehl J. , Guzzinati G. , Schultz J. , Potapov P. , Pohl D. , Martin Jérôme , Verbeeck J. , Fery A. , Büchner B. , Lubk A.
Published: October 2018

Plasmonic nanostructures and -devices are rapidly transforming light manipulation technology by allowing to modify and enhance optical fields on sub-wavelength scales. Advances in this field rely heavily on the development of new characterization methods for the fundamental nanoscale interactions. However, the direct and quantitative mapping of transient electric and magnetic fields characterizing the plasmonic coupling has been proven elusive to date. Here we demonstrate how to directly measure the inelastic momentum transfer of surface plasmon modes via the energy-loss filtered deflection of a focused electron beam in a transmission electron microscope. By scanning the beam over the sample we obtain a spatially and spectrally resolved deflection map and we further show how this deflection is related quantitatively to the spectral component of the induced electric and magnetic fields pertaining to the mode. In some regards this technique is an extension to the established differential phase contrast into the dynamic regime.
Spatially-resolved fluorescence-detected two-dimensional electronic spectroscopy probes varying excitonic structure in photosynthetic bacteria
Authors: Tiwari Vivek , Matutes Yassel Acosta , Gardiner Alastair T. , Jansen Thomas L. C. , Cogdell Richard J. , Ogilvie Jennifer P.
Published: October 2018

Conventional implementations of two-dimensional electronic spectroscopy typically spatially average over ~1010 chromophores spread over ~104 micron square area, limiting their ability to characterize spatially heterogeneous samples. Here we present a variation of two-dimensional electronic spectroscopy that is capable of mapping spatially varying differences in excitonic structure, with sensitivity orders of magnitude better than conventional spatially-averaged electronic spectroscopies. The approach performs fluorescence-detection-based fully collinear two-dimensional electronic spectroscopy in a microscope, combining femtosecond time-resolution, sub-micron spatial resolution, and the sensitivity of fluorescence detection. We demonstrate the approach on a mixture of photosynthetic bacteria that are known to exhibit variations in electronic structure with growth conditions. Spatial variations in the constitution of mixed bacterial colonies manifests as spatially varying peak intensities in the measured two-dimensional contour maps, which exhibit distinct diagonal and cross-peaks that reflect differences in the excitonic structure of the bacterial proteins.
Rifampicin can induce antibiotic tolerance in mycobacteria via paradoxical changes in rpoB transcription
Authors: Zhu Jun-Hao , Wang Bi-Wei , Pan Miaomiao , Zeng Yu-Na , Rego Hesper , Javid Babak
Published: October 2018

Metrics commonly used to describe antibiotic efficacy rely on measurements performed on bacterial populations. However, certain cells in a bacterial population can continue to grow and divide, even at antibiotic concentrations that kill the majority of cells, in a phenomenon known as antibiotic tolerance. Here, we describe a form of semi-heritable tolerance to the key anti-mycobacterial agent rifampicin, which is known to inhibit transcription by targeting the β subunit of the RNA polymerase (RpoB). We show that rifampicin exposure results in rpoB upregulation in a sub-population of cells, followed by growth. More specifically, rifampicin preferentially inhibits one of the two rpoB promoters (promoter I), allowing increased rpoB expression from a second promoter (promoter II), and thus triggering growth. Disruption of promoter architecture leads to differences in rifampicin susceptibility of the population, confirming the contribution of rifampicin-induced rpoB expression to tolerance.
Author Correction: Scutoids are a geometrical solution to three-dimensional packing of epithelia
Authors: Gómez-Gálvez Pedro , Vicente-Munuera Pablo , Tagua Antonio , Forja Cristina , Castro Ana M. , Letrán Marta , Valencia-Expósito Andrea , Grima Clara , Bermúdez-Gallardo Marina , Serrano-Pérez-Higueras Óscar , Cavodeassi Florencia , Sotillos Sol , Martín-Bermudo María D. , Márquez Alberto , Buceta Javier , Escudero Luis M.
Published: October 2018

The original version of this Article contained an error in ref. 39, which incorrectly cited ‘Fristrom, D. & Fristrom, J. W. in The Development of Drosophila melanogaster (eds. Bate, M. & Martinez-Arias, A.) II, (Cold spring harbor laboratory press, 1993)’. The correct reference is ‘Condic, M.L, Fristrom, D. & Fristrom, J.W. Apical cell shape changes during Drosophila imaginal leg disc elongation: a novel morphogenetic mechanism. Development111: 23-33 (1991)’. Furthermore, the last sentence of the fourth paragraph of the introduction incorrectly omitted citation of work by Rupprecht et al. The correct citation is given below. These errors have now been corrected in both the PDF and HTML versions of the Article. Rupprecht, J.F., Ong, K.H., Yin, J., Huang, A., Dinh, H.H., Singh, A.P., Zhang, S., Yu, W. & Saunders, T.E. Geometric constraints alter cell arrangements within curved epithelial tissues. Mol. Biol. Cell 28, 3582-3594 (2017).
State-recycling and time-resolved imaging in topological photonic lattices
Authors: Mukherjee Sebabrata , Chandrasekharan Harikumar K. , Öhberg Patrik , Goldman Nathan , Thomson Robert R.
Published: October 2018

Photonic lattices—arrays of optical waveguides—are powerful platforms for simulating a range of phenomena, including topological phases. While probing dynamics is possible in these systems, by reinterpreting the propagation direction as time, accessing long timescales constitutes a severe experimental challenge. Here, we overcome this limitation by placing the photonic lattice in a cavity, which allows the optical state to evolve through the lattice multiple times. The accompanying detection method, which exploits a multi-pixel single-photon detector array, offers quasi-real time-resolved measurements after each round trip. We apply the state-recycling scheme to intriguing photonic lattices emulating Dirac fermions and Floquet topological phases. We also realise a synthetic pulsed electric field, which can be used to drive transport within photonic lattices. This work opens an exciting route towards the detection of long timescale effects in engineered photonic lattices and the realisation of hybrid analogue-digital simulators.
The quantum-confined Stark effect in layered hybrid perovskites mediated by orientational polarizability of confined dipoles
Authors: Walters G. , Wei M. , Voznyy O. , Quintero-Bermudez R. , Kiani A. , Smilgies D.-M. , Munir R. , Amassian A. , Hoogland S. , Sargent E.
Published: October 2018

The quantum-confined Stark effect (QCSE) is an established optical modulation mechanism, yet top-performing modulators harnessing it rely on costly fabrication processes. Here, we present large modulation amplitudes for solution-processed layered hybrid perovskites and a modulation mechanism related to the orientational polarizability of dipolar cations confined within these self-assembled quantum wells. We report an anomalous (blue-shifting) QCSE for layers that contain methylammonium cations, in contrast with cesium-containing layers that show normal (red-shifting) behavior. We attribute the blue-shifts to an extraordinary diminution in the exciton binding energy that arises from an augmented separation of the electron and hole wavefunctions caused by the orientational response of the dipolar cations. The absorption coefficient changes, realized by either the red- or blue-shifts, are the strongest among solution-processed materials at room temperature and are comparable to those exhibited in the highest-performing epitaxial compound semiconductor heterostructures.