bluuebunny/crossref_metadata_2025_split huggingface dataset:
BRAZILIAN RACE RELATIONS, FRENCH SOCIAL SCIENTISTS, AND AFRICAN DECOLONIZATION: A TRANSATLANTIC HISTORY OF THE IDEA OF MISCEGENATION
Authors: MERKEL IAN 
Published: March 2019

AbstractThis article analyzes how debates concerning Brazilian race relations, miscegenation, and racial democracy unfolded in France in the 1950s. During those years, Gilberto Freyre and those critical of him emerged in French social scientific discourse, offering distinct visions concerning race, culture, and the possibility of harmonious coexistence in a world structured by racial, social, and colonial inequalities. Certain French social scientists such as Lucien Febvre and Fernand Braudel embraced Freyre's vision as a possible source for racial and cultural mixing, whereas others, especially Alfred Métraux and Florestan Fernandes, directly criticized his work. Roger Bastide mediated between the two, translating Freyre's Casa-Grande & Senzala and coauthoring a UNESCO-based study on blacks and whites in São Paulo that largely repudiated Freyre's claims. I argue that in a period in which decolonization was already underway, Freyre piqued the interest of French social scientists looking to overcome the growing antagonism between colonizer and colonized, even if other models of cultural integration and autonomy contested the validity of Brazil's so-called racial democracy.
Detection of Carbonates in Martian Weathering Profiles
Authors: Bultel Benjamin , Viennet Jean‐Christophe , Poulet François , Carter John , Werner Stephanie C. 
Published: March 2019

AbstractNoachian surfaces on Mars exhibit vertical assemblages of weathering horizons termed as weathering profiles; this indicates that surface water caused alteration of the rocks that required a different, warmer climate than today. Evidence of this early Martian climate with CO2 vapor as the main component causing greenhouse warming has been challenged by the lack of carbonate in these profiles. Here we report the analysis of Compact Reconnaissance Imaging Spectrometer for Mars L‐detector data leading to the detections of carbonates using a spectral signature exclusively attributed to them. The carbonates are collocated with hydroxylated minerals in weathering profiles over the Martian surface. The origin of CO2 for the formation of carbonates could be the atmosphere. The widespread distribution of weathering profiles with carbonates over the surface of the planet suggest global interactions between fluids containing carbonate/bicarbonate ions with the surface of Mars in the presence of atmospheric water until around 3.7 billion years ago.
Deactivation of redox mediators in lithium-oxygen batteries by singlet oxygen
Authors: Kwak Won-Jin , Kim Hun , Petit Yann K. , Leypold Christian , Nguyen Trung Thien , Mahne Nika , Redfern Paul , Curtiss Larry A. , Jung Hun-Gi , Borisov Sergey M. , Freunberger Stefan A. , Sun Yang-Kook 
Published: March 2019

AbstractNon-aqueous lithium-oxygen batteries cycle by forming lithium peroxide during discharge and oxidizing it during recharge. The significant problem of oxidizing the solid insulating lithium peroxide can greatly be facilitated by incorporating redox mediators that shuttle electron-holes between the porous substrate and lithium peroxide. Redox mediator stability is thus key for energy efficiency, reversibility, and cycle life. However, the gradual deactivation of redox mediators during repeated cycling has not conclusively been explained. Here, we show that organic redox mediators are predominantly decomposed by singlet oxygen that forms during cycling. Their reaction with superoxide, previously assumed to mainly trigger their degradation, peroxide, and dioxygen, is orders of magnitude slower in comparison. The reduced form of the mediator is markedly more reactive towards singlet oxygen than the oxidized form, from which we derive reaction mechanisms supported by density functional theory calculations. Redox mediators must thus be designed for stability against singlet oxygen.
Characterization of putative DD-carboxypeptidase-encoding genes in Mycobacterium smegmatis
Authors: Ealand Christopher S. , Asmal Rukaya , Mashigo Lethabo , Campbell Lisa , Kana Bavesh D. 
Published: March 2019

AbstractPenicillin binding proteins (PBPs) are the target of numerous antimicrobial agents that disrupt bacterial cell wall synthesis. In mycobacteria, cell elongation occurs through insertion of nascent cell wall material in the sub-polar region, a process largely driven by High Molecular Weight PBPs. In contrast, the function of DD-carboxypeptidases (DD-CPases), which are Low Molecular Weight Class 1C PBPs, in mycobacteria remains poorly understood. Mycobacterium smegmatis encodes four putative DD-CPase homologues, which display homology to counterparts in Escherichia coli. Herein, we demonstrate that these are expressed in varying abundance during growth. Deletion of MSMEG_1661, MSMEG_2433 or MSMEG_2432, individually resulted in no defects in growth, cell morphology, drug susceptibility or spatial incorporation of new peptidoglycan. In contrast, deletion of MSMEG_6113 (dacB) was only possible in a merodiploid strain expressing the homologous M. tuberculosis operon encoding Rv3627c (dacB), Rv3626c, Rv3625c (mesJ) and Rv3624c (hpt), suggestive of essentiality. To investigate the role of this operon in mycobacterial growth, we depleted gene expression using anhydrotetracycline-responsive repressors and noted reduced bipolar peptidoglycan synthesis. These data point to a possible role for this four gene operon, which is highly conserved across all mycobacterial species, in regulating spatial localization of peptidoglycan synthesis.
Utilizing general human movement models to predict the spread of emerging infectious diseases in resource poor settings
Authors: Kraemer M. U. G. , Golding N. , Bisanzio D. , Bhatt S. , Pigott D. M. , Ray S. E. , Brady O. J. , Brownstein J. S. , Faria N. R. , Cummings D. A. T. , Pybus O. G. , Smith D. L. , Tatem A. J. , Hay S. I. , Reiner R. C. 
Published: March 2019

AbstractHuman mobility is an important driver of geographic spread of infectious pathogens. Detailed information about human movements during outbreaks are, however, difficult to obtain and may not be available during future epidemics. The Ebola virus disease (EVD) outbreak in West Africa between 2014–16 demonstrated how quickly pathogens can spread to large urban centers following one cross-species transmission event. Here we describe a flexible transmission model to test the utility of generalised human movement models in estimating EVD cases and spatial spread over the course of the outbreak. A transmission model that includes a general model of human mobility significantly improves prediction of EVD’s incidence compared to models without this component. Human movement plays an important role not only to ignite the epidemic in locations previously disease free, but over the course of the entire epidemic. We also demonstrate important differences between countries in population mixing and the improved prediction attributable to movement metrics. Given their relative rareness, locally derived mobility data are unlikely to exist in advance of future epidemics or pandemics. Our findings show that transmission patterns derived from general human movement models can improve forecasts of spatio-temporal transmission patterns in places where local mobility data is unavailable.
Keggin-type polyoxotungstates as mushroom tyrosinase inhibitors - A speciation study
Authors: Breibeck Joscha , Gumerova Nadiia I. , Boesen Benedikt B. , Galanski Mathea Sophia , Rompel Annette 
Published: March 2019

AbstractMushroom tyrosinase abPPO4 is a commercially relevant polyphenol oxidase and has been being targeted for numerous inhibition studies including polyoxometalates (POMs). In the present work, its diphenolase activity was inhibited at pH 6.8 by a series of structurally related polyoxotungstates (POTs) of the α-Keggin archetype, exhibiting the general formula [Xn+W12O40](8−n)− in order to elucidate charge-dependent activity correlations. Kinetic data were obtained from the dopachrome assay and 183W NMR was applied to obtain crucial insights into the actual Keggin POT speciation in solution, facilitating a straightforward assignment of inhibition effects to the identified POT species. While [PW12O40]3− was completely hydrolyzed to its moderately active lacunary form Hx[PW11O39](7−x)− (Ki = 25.6 mM), [SiW12O40]4− showed the most pronounced inhibition effects with a Ki of 4.7 mM despite of partial hydrolysis to its ineffective lacunary form Hx[SiW11O39](8−x)−. More negative Keggin cluster charges of 5− and 6− generally resulted in preclusion of inhibitory efficacy as well as hydrolysis, but with the Ni-substituted cluster [PW11O39{Ni(H2O)}]5− enzymatic inhibition was clearly restored (Ki = 9.7 mM). The inhibitory capacity of the structurally intact Keggin POTs was found to be inversely correlated to their net charge. The here applied speciation strategy is of utmost importance for any biological POM application to identify the actually active POM species.
Reverse-Correlation Analysis of the Mechanosensation Circuit and Behavior in C. elegans Reveals Temporal and Spatial Encoding
Authors: Porto Daniel A. , Giblin John , Zhao Yiran , Lu Hang 
Published: March 2019

AbstractAnimals must integrate the activity of multiple mechanoreceptors to navigate complex environments. In Caenorhabditis elegans, the general roles of the mechanosensory neurons have been defined, but most studies involve end-point or single-time-point measurements, and thus lack dynamic information. Here, we formulate a set of unbiased quantitative characterizations of the mechanosensory system by using reverse correlation analysis on behavior. We use a custom tracking, selective illumination, and optogenetics platform to compare two mechanosensory systems: the gentle-touch (TRNs) and harsh-touch (PVD) circuits. This method yields characteristic linear filters that allow for the prediction of behavioral responses. The resulting filters are consistent with previous findings and further provide new insights on the dynamics and spatial encoding of the systems. Our results suggest that the tiled network of the gentle-touch neurons has better resolution for spatial encoding than the harsh-touch neurons. Additionally, linear-nonlinear models can predict behavioral responses based only on sensory neuron activity. Our results capture the overall dynamics of behavior induced by the activation of sensory neurons, providing simple transformations that quantitatively characterize these systems. Furthermore, this platform can be extended to capture the behavioral dynamics induced by any neuron or other excitable cells in the animal.
Differential Diffusion of Helium Isotopes in Glass, Quantum-tunneling 3He Enrichment, and Portable 3He/4He Monitoring of Mantle Processes
Authors: McMurtry Gary M. , DeLuze James R. , Hilton David R. , Blessing James E. 
Published: March 2019

AbstractWhile studying the scientific and engineering aspects of a field-portable 3He/4He ratio detector, we found elevated ratios at comparatively lower temperatures that appear to result from differential diffusion of these isotopes in pure quartz glass. The 3He enrichment relative to 4He in lab air, expressed as the ratio R and normalized to the accepted 3He/4He ratio of 1.40 E-06 (Ra), ranges from peak values of about 200 to 600 in dry static samples. Even at the maximum classical 3He/4He diffusivity ratio of 1.15, the expected R would be only 1.61 E-06. Within a narrow temperature window, the air value in our experimental set up with pure quartz glass can range from about 2.70 to 8.20 E-04, or nearly 1000 times the expected enrichment based upon classical fractionation. When plotted versus temperature, the narrow 3He net partial pressure peak reveals at least three sharper embedded peaks that may be quantized vibrational entrance states in quartz glass which are temperature specific. This discovery has implications for relatively low-energy industrial enrichment of scarce 3He from natural sources on Earth, and for radiogenic and cosmogenic helium dating assumptions in natural glasses. It also has bearing upon designs for field portable 3He/4He ratio detectors aimed at earthquake and volcanic eruption studies, and monitoring of nuclear sites.
The M1 muscarinic acetylcholine receptor subtype is important for retinal neuron survival in aging mice
Authors: Laspas Panagiotis , Zhutdieva Mayagozel B. , Brochhausen Christoph , Musayeva Aytan , Zadeh Jenia Kouchek , Pfeiffer Norbert , Xia Ning , Li Huige , Wess Juergen , Gericke Adrian 
Published: March 2019

AbstractMuscarinic acetylcholine receptors have been implicated as potential neuroprotective targets for glaucoma. We tested the hypothesis that the lack of a single muscarinic receptor subtype leads to age-dependent neuron reduction in the retinal ganglion cell layer. Mice with targeted disruption of single muscarinic acetylcholine receptor subtype genes (M1 to M5) and wild-type controls were examined at two age categories, 5 and 15 months, respectively. We found no differences in intraocular pressure between individual mouse groups. Remarkably, in 15-month-old mice devoid of the M1 receptor, neuron number in the retinal ganglion cell layer and axon number in the optic nerve were markedly reduced. Moreover, mRNA expression for the prooxidative enzyme, NOX2, was increased, while mRNA expression for the antioxidative enzymes, SOD1, GPx1 and HO-1, was reduced in aged M1 receptor-deficient mice compared to age-matched wild-type mice. In line with these findings, the reactive oxygen species level was also elevated in the retinal ganglion cell layer of aged M1 receptor-deficient mice. In conclusion, M1 receptor deficiency results in retinal ganglion cell loss in aged mice via involvement of oxidative stress. Based on these findings, activation of M1 receptor signaling may become therapeutically useful to promote retinal ganglion cell survival.
Simulation and design of folded perovskite x-ray detectors
Authors: Mescher Henning , Hamann Elias , Lemmer Uli 
Published: March 2019

AbstractA variety of medical, industrial, and scientific applications requires highly sensitive and cost-effective x-ray detectors for photon energies ranging from keV to MeV. Adapting the thickness of polycrystalline or single crystal conversion layers especially to high-energy applications increases the complexity of fabrication and potentially decreases the performance of conventional direct conversion x-ray detectors. To tackle the challenges with respect to the active layer thickness and to combine the superior performance of single crystal materials with the low-cost nature of polycrystalline conversion layers, we investigate thin film x-ray detector technologies based on a folded device architecture. Analytical models simulating the sensitivity and the detective quantum efficiency (DQE) are used to evaluate the performance of folded detectors based on polycrystalline organic-inorganic perovskite semiconductors in various layout configurations and for different photon energies. Simulations of folded perovskite devices show high sensitivities. The DQE analysis introduces additional noise related boundary conditions for the folding length. A comparison with conventional detectors based on state of the art conversion materials at different photon energies demonstrates the potential of the folded detector layout as simulated sensitivities are comparable to single crystal detectors.
Nanoscale structure of amyloid-β plaques in Alzheimer’s disease
Authors: Querol-Vilaseca Marta , Colom-Cadena Martí , Pegueroles Jordi , Nuñez-Llaves Raúl , Luque-Cabecerans Joan , Muñoz-Llahuna Laia , Andilla Jordi , Belbin Olivia , Spires-Jones Tara L. , Gelpi Ellen , Clarimon Jordi , Loza-Alvarez Pablo , Fortea Juan , Lleó Alberto 
Published: March 2019

AbstractSoluble amyloid-β (Aβ) is considered to be a critical component in the pathogenesis of Alzheimer’s disease (AD). Evidence suggests that these non-fibrillar Aβ assemblies are implicated in synaptic dysfunction, neurodegeneration and cell death. However, characterization of these species comes mainly from studies in cellular or animal models, and there is little data in intact human samples due to the lack of adequate optical microscopic resolution to study these small structures. Here, to achieve super-resolution in all three dimensions, we applied Array Tomography (AT) and Stimulated Emission Depletion microscopy (STED), to characterize in postmortem human brain tissue non-fibrillar Aβ structures in amyloid plaques of cases with autosomal dominant and sporadic AD. Ultrathin sections scanned with super-resolution STED microscopy allowed the detection of small Aβ structures of the order of 100 nm. We reconstructed a whole human amyloid plaque and established that plaques are formed by a dense core of higher order Aβ species (~0.022 µm3) and a peripheral halo of smaller Aβ structures (~0.003 µm3). This work highlights the potential of AT-STED for human neuropathological studies.
Calcitonin native prefibrillar oligomers but not monomers induce membrane damage that triggers NMDA-mediated Ca2+-influx, LTP impairment and neurotoxicity
Authors: Belfiore Marcello , Cariati Ida , Matteucci Andrea , Gaddini Lucia , Macchia Gianfranco , Fioravanti Raoul , Frank Claudio , Tancredi Virginia , D’Arcangelo Giovanna , Diociaiuti Marco 
Published: March 2019

AbstractAmyloid protein misfolding results in a self-assembling aggregation process, characterized by the formation of typical aggregates. The attention is focused on pre-fibrillar oligomers (PFOs), formed in the early stages and supposed to be neurotoxic. PFOs structure may change due to their instability and different experimental protocols. Consequently, it is difficult to ascertain which aggregation species are actually neurotoxic. We used salmon Calcitonin (sCT) as an amyloid model whose slow aggregation rate allowed to prepare stable samples without photochemical cross-linking. Intracellular Ca2+ rise plays a fundamental role in amyloid protein-induced neurodegerations. Two paradigms have been explored: (i) the “membrane permeabilization” due to the formation of amyloid pores or other types of membrane damage; (ii) “receptor-mediated” modulation of Ca2+ channels. In the present paper, we tested the effects of native sCT PFOs- with respect to Monomer-enriched solutions in neurons characterized by an increasing degree of differentiation, in terms of -Ca2+-influx, cellular viability, -Long-Term Potentiation impairment, Post-Synaptic Densities and synaptophysin expression. Results indicated that PFOs-, but not Monomer-enriched solutions, induced abnormal -Ca2+-influx, which could only in part be ascribed to NMDAR activation. Thus, we propose an innovative neurotoxicity mechanism for amyloid proteins where “membrane permeabilization” and “receptor-mediated” paradigms coexist.
Bromeliaceae subfamilies show divergent trends of genome size evolution
Authors: Müller Lilian-Lee B. , Zotz Gerhard , Albach Dirk C. 
Published: March 2019

AbstractGenome size is known to vary widely across plants. Yet, the evolutionary drivers and consequences of genome size variation across organisms are far from understood. We investigated genome size variation and evolution in two major subfamilies of the Neotropical family Bromeliaceae by determining new genome size values for 83 species, testing phylogenetic signal in genome size variation, and assessing the fit to different evolutionary models. For a subset of epiphytic bromeliad species, we also evaluated the relationship of genome size with thermal traits and relative growth rate (RGR), respectively. Genome size variation in Bromelioideae appears to be evolutionary conserved, while genome size among Tillandsioideae varies considerably, not just due to polyploidy but arguably also due to environmental factors. The subfamilies show fundamental differences in genome size and RGR: Bromelioideae have, on average, lower genome sizes than Tillandsioideae and at the same time exhibit higher RGR. We attribute this to different resource use strategies in the subfamilies. Analyses among subfamilies, however, revealed unexpected positive relationships between RGR and genome size, which might be explained by the nutrient regime during cultivation. Future research should test whether there is indeed a trade-off between genome size and growth efficiency as a function of nutrient supply.
Friction factor for turbulent open channel flow covered by vegetation
Authors: Wang Wei-Jie , Peng Wen-Qi , Huai Wen-Xin , Katul Gabriel G. , Liu Xiao-Bo , Qu Xiao-Dong , Dong Fei 
Published: March 2019

AbstractThe need for operational models describing the friction factor f in streams remains undisputed given its utility across a plethora of hydrological and hydraulic applications concerned with shallow inertial flows. For small-scale roughness elements uniformly covering the wetted parameter of a wide channel, the Darcy-Weisbach f = 8(u*/Ub)2 is widely used at very high Reynolds numbers, where u* is friction velocity related to the surface kinematic stress, Ub = Q/A is bulk velocity, Q is flow rate, and A is cross-sectional area orthogonal to the flow direction. In natural streams, the presence of vegetation introduces additional complications to quantifying f, the subject of the present work. Turbulent flow through vegetation are characterized by a number of coherent vortical structures: (i) von Karman vortex streets in the lower layers of vegetated canopies, (ii) Kelvin-Helmholtz as well as attached eddies near the vegetation top, and (iii) attached eddies well above the vegetated layer. These vortical structures govern the canonical mixing lengths for momentum transfer and their influence on f is to be derived. The main novelty is that the friction factor of vegetated flow can be expressed as fv = 4Cd(Uv/Ub)2 where Uv is the spatially averaged velocity within the canopy volume, and Cd is a local drag coefficient per unit frontal area derived to include the aforemontioned layer-wise effects of vortical structures within and above the canopy along with key vegetation properties. The proposed expression is compared with a number of empirical relations derived for vegetation under emergent and submerged conditions as well as numerous data sets covering a wide range of canopy morphology, densities, and rigidity. It is envisaged that the proposed formulation be imminently employed in eco-hydraulics where the interaction between flow and vegetation is being sought.