bluuebunny/crossref_metadata_2025 huggingface dataset:
‘ZIMBABWEANS ARE FOOLISHLY LITIGIOUS’: EXPLORING THE LOGIC OF APPEALS TO A POLITICIZED LEGAL SYSTEM
Authors: Verheul Susanne
Published: January 2016

In this article, I focus on the narratives of two men, Patrick and Father Marko Mkandla. I ask whether their continued interactions with, and appeals to, Zimbabwe's politicized legal system were ‘foolish’. The two men inhabited different geographic regions and diverged in their economic positions, political engagement, and ties to Zimbabwe's human rights networks. They nonetheless both started their accounts by recollecting that they persisted in reporting cases of political violence to the Zimbabwe Republic Police. Their accounts show us that imagining, invoking and interacting with the law in Zimbabwe was often an ambiguous, occasionally dangerous, and very contradictory exercise. Under ZANU-PF's rule, judicial institutions were increasingly politicized as instruments for repression. The men nevertheless continued to interact with the state and its officials as if these were bound by rules. This allowed Patrick and Father Mkandla to perform their rights-based citizenship, to experience occasional ‘successes’, and to differentiate themselves from the ‘unprofessional’ politicized civil servants they encountered during their appeals. Rather than ‘foolishly’ invoking the law, some Zimbabwean citizens engaged it as a shared language through which they could articulate their imagination of, hopes for, and belonging to a rule-bound state in the future.
GOVERNMENT PROPERTIES: THE NIGERIA POLICE FORCE AS TOTAL INSTITUTION?
Authors: Owen Olly
Published: January 2016

This article looks at the relationships between Nigerian police officers and the Nigeria Police Force (NPF) in which they serve. Against simplistic portraits of police institutions as mechanistic agents of governmental power, the article looks inside one such institution to examine how it exercises power over its own personnel, in a totalizing institutional project which combines duty and identity within a hierarchical and paramilitarized structure. Police officers are caught between their embodying of state authority and their lack of authority within their own institution. At the same time, it depicts individual officers' attempts to navigate this structure to their own advantage, creating a counter-current within the institutional world. Both ultimately affect the way in which the NPF exercises its powers within wider society. According to this perspective, the violence and corruption, negligence and evasion that often typify interactions with the police may be less signs of police officers' power than of their attempts to cope with the lack of it.
A ‘DESPICABLE SHAMBLES’: LABOUR, PROPERTY AND STATUS IN FAYA-LARGEAU, NORTHERN CHAD
Authors: Brachet Julien , Scheele Judith
Published: January 2016

Faya-Largeau, the largest oasis in northern Chad, seems to present a classic picture of Saharan labour relations and status groups. Colonial officers spoke of nomadic ‘overlords’ who used to exploit sedentary ‘serfs’ of slave descent, but indirectly favoured the latter; today, former status relations are renegotiated, at times violently so. Access to vital resources, and especially agricultural land, is the focus of much contemporary conflict. Yet, on a closer look, this picture becomes less familiar: local agriculture requires little labour, property rights are uncertain, bilateral descent, exogamy and a high degree of mobility blur boundaries, while state involvement remains limited and ambiguous, and education little valued. Status, property and labour hence emerge as contextual categories that depend on as much as they constitute a historically specific and inherently unstable mode of production.
LABOUR POLITICS AND AFRICANIZATION AT A TANZANIAN SCIENTIFIC RESEARCH INSTITUTE, 1949–66
Authors: Poleykett Branwyn , Mangesho Peter
Published: January 2016

In this article we examine labour politics and unionization at a scientific research station: the former Institute of Malaria and Vector Borne Diseases (‘Amani’) in north-eastern Tanzania. Drawing on an analysis of an archive found at Amani, this paper approaches the process of decolonizing and Africanizing science and medical research from the perspective of African technicians. The technician cadre at Amani was drawn to scientific employment as it seemed to offer the promise of training, education and advancement. The union at Amani argued that African labour was crucial to the production of scientific knowledge at the station and that there ought to be a ‘ladder’ of promotion and progress that led from auxiliary scientific technician to independent researcher. The daily politics of the decolonization of science was conducted as everyday contentious labour relations and as increasingly vociferous claims upon the cultural power of science by African workers. Drawing attention to the social and spatial practices of African workers at Amani in the 1960s, we argue that Amani functioned not just within globalized networks of tropical medicine and scientific research but as a place bound both to local economies of labour and to larger geographies of African ambition and aspiration.
KENYA: TWENDAPI?: RE-READING ABDILATIF ABDALLA'S PAMPHLET FIFTY YEARS AFTER INDEPENDENCE
Authors: Kresse Kai
Published: January 2016

The pamphletKenya: Twendapi?(Kenya: Where are we heading?) is a text often referred to but rarely read or analysed. Abdilatif Abdalla wrote it as a twenty-two-year-old political activist of the KPU opposition as a critique of the dictatorial tendencies of Jomo Kenyatta and his KANU government in 1968, and consequently suffered three years of isolation in prison. Many (at least on the East African political and literary scene) know aboutKenya: Twendapi?but few seem to have read it – indeed, it seems almost unavailable to read. This contribution toAfrica's Local Intellectuals series provides a summary reconstruction of its main points and arguments, and a contextual discussion of the text. This is combined with the first published English translation (overseen by Abdalla himself) and a reprint of the original Swahili text, an important but almost inaccessible document. The article proceeds with a perspective first on the political context in Kenya at the time – an early turning point in postcolonial politics – and second on the work and life of its author, Abdilatif Abdalla who had been trained as a Swahili poet by elder family members who were poets. As most students of Swahili literature know, Abdalla's collection of poetrySauti ya Dhiki(1973) originated in the prison cell but they know little about the pamphletKenya: Twendapi?, nor the circumstances of its authorship. Part of my wider point for discussion is that Abdalla, as an engaged poet and political activist, can be usefully understood as a local intellectual who transcended the local from early on – topically and through global references and comparisons, but also through his experience in prison and exile. Concerns about Kenyan politics and Swahili literature have remained central to his life. This reflects Abdalla's continued and overarching connectedness to the Swahili-speaking region. Abdalla wrote in Swahili and was deeply familar with local Swahili genres and discursive conventions, language and verbal specifications (of critique, of emotions, of reflections) that use the whole range and depth of Kimvita, the Mombasan dialect of Kiswahili, as a reservoir of expression.
Oklahoma's Dormant Faults Hide Huge Seismic Risk Potential
Authors: Strelich Lily
Published: January 2016

Researchers look at induced seismicity data in Oklahoma to spot an increase of stress in faults that could cause even more damage than recent quakes.
Abundance of Satellite Data Presents Opportunity, Challenge
Authors: Hossain Faisal , Ramos Victor , Mugo Robinson
Published: January 2016

Globalizing Societal Application of Scientific Research and Observations from Remote Sensing: The Path Forward; Tacoma, Washington, 23–25 June 2015
Icebergs Fertilize Southern Ocean, Sequester Carbon
Authors: Wendel JoAnna
Published: January 2016

Huge, drifting ice rafts (the white spot on the satellite image below ) shed minerals as they melt, painting trails of nutrients, teeming phytoplankton, and chlorophyll across hundreds of kilometers of ocean.
Quake or Bomb? Seismic Waves Speak Truth, Even If Nations Don't
Authors: Sullivan Cody
Published: January 2016

When the Earth rumbles and no one knows why, seismologists can analyze the seismic event's waveforms to determine whether a hidden explosion or an earthquake caused the shaking.
Potential sources of microbial colonizers in an initial soil ecosystem after retreat of an alpine glacier
Authors: Rime Thomas , Hartmann Martin , Frey Beat
Published: January 2016

Rapid disintegration of alpine glaciers has led to the formation of new terrain consisting of mineral debris colonized by microorganisms. Despite the importance of microbial pioneers in triggering the formation of terrestrial ecosystems, their sources (endogenous versus exogenous) and identities remain elusive. We used 454-pyrosequencing to characterize the bacterial and fungal communities in endogenous glacier habitats (ice, sub-, supraglacial sediments and glacier stream leaving the glacier forefront) and in atmospheric deposition (snow, rain and aeolian dust). We compared these microbial communities with those occurring in recently deglaciated barren soils before and after snow melt (snow-covered soil and barren soil). Atmospheric bacteria and fungi were dominated by plant-epiphytic organisms and differed from endogenous glacier habitats and soils indicating that atmospheric input of microorganisms is not a major source of microbial pioneers in newly formed soils. We found, however, that bacterial communities in newly exposed soils resembled those of endogenous habitats, which suggests that bacterial pioneers originating from sub- and supraglacial sediments contributed to the colonization of newly exposed soils. Conversely, fungal communities differed between habitats suggesting a lower dispersal capability than bacteria. Yeasts putatively adapted to cold habitats characteristic of snow and supraglacial sediments were similar, despite the fact that these habitats were not spatially connected. These findings suggest that environmental filtering selects particular fungi in cold habitats. Atmospheric deposition provided important sources of dissolved organic C, nitrate and ammonium. Overall, microbial colonizers triggering soil development in alpine environments mainly originate from endogenous glacier habitats, whereas atmospheric deposition contributes to the establishment of microbial communities by providing sources of C and N.
Shifts in diversity and function of lake bacterial communities upon glacier retreat
Authors: Peter Hannes , Sommaruga Ruben
Published: January 2016

Global climate change is causing a wastage of glaciers and threatening biodiversity in glacier-fed ecosystems. The high turbidity typically found in those ecosystems, which is caused by inorganic particles and result of the erosive activity of glaciers is a key environmental factor influencing temperature and light availability, as well as other factors in the water column. Once these lakes loose hydrological connectivity to glaciers and turn clear, the accompanying environmental changes could represent a potential bottleneck for the established local diversity with yet unknown functional consequences. Here, we study three lakes situated along a turbidity gradient as well as one clear unconnected lake and evaluate seasonal changes in their bacterial community composition and diversity. Further, we assess potential consequences for community functioning. Glacier runoff represented a diverse source community for the lakes and several taxa were able to colonize downstream turbid habitats, although they were not found in the clear lake. Operational taxonomic unit-based alpha diversity and phylogenetic diversity decreased along the turbidity gradient, but metabolic functional diversity was negatively related to turbidity. No evidence for multifunctional redundancy, which may allow communities to maintain functioning upon alterations in diversity, was found. Our study gives a first view on how glacier-fed lake bacterial communities are affected by the melting of glaciers and indicates that diversity and community composition significantly change when hydrological connectivity to the glacier is lost and lakes turn clear.
Peat: home to novel syntrophic species that feed acetate- and hydrogen-scavenging methanogens
Authors: Schmidt Oliver , Hink Linda , Horn Marcus A , Drake Harold L
Published: January 2016

Syntrophic bacteria drive the anaerobic degradation of certain fermentation products (e.g., butyrate, ethanol, propionate) to intermediary substrates (e.g., H2, formate, acetate) that yield methane at the ecosystem level. However, little is known about the in situ activities and identities of these syntrophs in peatlands, ecosystems that produce significant quantities of methane. The consumption of butyrate, ethanol or propionate by anoxic peat slurries at 5 and 15 °C yielded methane and CO2 as the sole accumulating products, indicating that the intermediates H2, formate and acetate were scavenged effectively by syntrophic methanogenic consortia. 16S rRNA stable isotope probing identified novel species/strains of Pelobacter and Syntrophomonas that syntrophically oxidized ethanol and butyrate, respectively. Propionate was syntrophically oxidized by novel species of Syntrophobacter and Smithella, genera that use different propionate-oxidizing pathways. Taxa not known for a syntrophic metabolism may have been involved in the oxidation of butyrate (Telmatospirillum-related) and propionate (unclassified Bacteroidetes and unclassified Fibrobacteres). Gibbs free energies (ΔGs) for syntrophic oxidations of ethanol and butyrate were more favorable than ΔGs for syntrophic oxidation of propionate. As a result of the thermodynamic constraints, acetate transiently accumulated in ethanol and butyrate treatments but not in propionate treatments. Aceticlastic methanogens (Methanosarcina, Methanosaeta) appeared to outnumber hydrogenotrophic methanogens (Methanocella, Methanoregula), reinforcing the likely importance of aceticlastic methanogenesis to the overall production of methane. ΔGs for acetogenesis from H2 to CO2 approximated to −20 kJ mol−1 when acetate concentrations were low, indicating that acetogens may have contributed to the flow of carbon and reductant towards methane.
Geographic patterns of co-occurrence network topological features for soil microbiota at continental scale in eastern China
Authors: Ma Bin , Wang Haizhen , Dsouza Melissa , Lou Jun , He Yan , Dai Zhongmin , Brookes Philip C , Xu Jianming , Gilbert Jack A
Published: January 2016

Soil microbiota play a critical role in soil biogeochemical processes and have a profound effect on soil functions. Recent studies have revealed microbial co-occurrence patterns in soil microbial communities, yet the geographic pattern of topological features in soil microbial co-occurrence networks at the continental scale are largely unknown. Here, we investigated the shifts of topological features in co-occurrence networks inferred from soil microbiota along a continental scale in eastern China. Integrating archaeal, bacterial and fungal community datasets, we inferred a meta-community co-occurrence network and analyzed node-level and network-level topological shifts associated with five climatic regions. Both node-level and network-level topological features revealed geographic patterns wherein microorganisms in the northern regions had closer relationships but had a lower interaction influence than those in the southern regions. We further identified topological differences associated with taxonomic groups and demonstrated that co-occurrence patterns were random for archaea and non-random for bacteria and fungi. Given that microbial interactions may contribute to soil functions more than species diversity, this geographic shift of topological features provides new insight into studying microbial biogeographic patterns, their organization and impacts on soil-associated function.
The membrane topology of vitamin K epoxide reductase is conserved between human isoforms and the bacterial enzyme
Authors: Cao Zhenbo , van Lith Marcel , Mitchell Lorna J. , Pringle Marie Anne , Inaba Kenji , Bulleid Neil J.
Published: January 2016

The membrane topology of vitamin K epoxide reductase (VKOR) is controversial with data supporting both a three transmembrane and a four transmembrane model. The positioning of the transmembrane domains and the loops between these domains is critical if we are to understand the mechanism of vitamin K oxidation and its recycling by members of the thioredoxin family of proteins and the mechanism of action of warfarin, an inhibitor of VKOR. Here we show that both mammalian VKOR isoforms adopt the same topology, with the large loop between transmembrane one and two facing the lumen of the endoplasmic reticulum (ER). We used a redox sensitive green fluorescent protein (GFP) fused to the N- or C-terminus to show that these regions face the cytosol, and introduction of glycosylation sites along with mixed disulfide formation with thioredoxin-like transmembrane protein (TMX) to demonstrate ER localization of the major loop. The topology is identical with the bacterial homologue from Synechococcus sp., for which the structure and mechanism of recycling has been characterized. Our results provide a resolution to the membrane topology controversy and support previous results suggesting a role for members of the ER protein disulfide isomerase (PDI) family in recycling VKOR.
Enzymatic changes in myosin regulatory proteins may explain vasoplegia in terminally ill patients with sepsis
Authors: Zheng Wentao , Kou Yong , Gao Feng-lan , Ouyang Xiu-he
Published: January 2016

The current study was conducted with the hypothesis that failure of maintenance of the vascular tone may be central to failure of the peripheral circulation and spiralling down of blood pressure in sepsis. Namely, we examined the balance between expression of myosin light chain (MLC) phosphatase and kinase, enzymes that regulate MLCs dephosphorylation and phosphorylation with a direct effect on pharmacomechanical coupling for smooth muscle relaxation and contraction respectively. Mechanical recordings and enzyme immunoassays of vascular smooth muscle lysates were used as the major methods to examine arterial biopsy samples from terminally ill sepsis patients. The results of the present study provide evidence that genomic alteration of expression of key regulatory proteins in vascular smooth muscles may be responsible for the relentless downhill course in sepsis. Down-regulation of myosin light chain kinase (MLCK) and up-regulation of MLCK may explain the loss of tone and failure to mount contractile response in vivo during circulation. The mechanical studies demonstrated the inability of the arteries to develop tone when stimulated by phenylephrine in vitro. The results of our study provide indirect hint that control of inflammation is a major therapeutic approach in sepsis, and may facilitate to ameliorate the progressive cardiovascular collapse.
Epoxyeicosatrienoic acid analogue mitigates kidney injury in a rat model of radiation nephropathy
Authors: Khan Md. Abdul Hye , Fish Brian , Wahl Geneva , Sharma Amit , Falck John R. , Paudyal Mahesh P. , Moulder John E. , Imig John D. , Cohen Eric P.
Published: January 2016

Arachidonic acid is metabolized to epoxyeicosatrienoic acids (EETs) by CYP epoxygenases, and EETs are kidney protective in multiple pathologies. We determined the ability of an EET analogue, EET-A, to mitigate experimental radiation nephropathy. The kidney expression of the EET producing enzyme CYP2C11 was lower in rats that received total body irradiation (TBI rat) compared with non-irradiated control. At 12 weeks after TBI, the rats had higher systolic blood pressure and impaired renal afferent arteriolar function compared with control, and EET-A or captopril mitigated these abnormalities. The TBI rats had 3-fold higher blood urea nitrogen (BUN) compared with control, and EET-A or captopril decreased BUN by 40–60%. The urine albumin/creatinine ratio was increased 94-fold in TBI rats, and EET-A or captopril attenuated that increase by 60–90%. In TBI rats, nephrinuria was elevated 30-fold and EET-A or captopril decreased it by 50–90%. Renal interstitial fibrosis, tubular and glomerular injury were present in the TBI rats, and each was decreased by EET-A or captopril. We further demonstrated elevated renal parenchymal apoptosis in TBI rats, which was mitigated by EET-A or captopril. Additional studies revealed that captopril or EET-A mitigated renal apoptosis by acting on the p53/Fas/FasL (Fas ligand) apoptotic pathway. The present study demonstrates a novel EET analogue-based strategy for mitigation of experimental radiation nephropathy by improving renal afferent arteriolar function and by decreasing renal apoptosis.
Design sensitivity and mixing uniformity of a micro-fluidic mixer
Authors: Ivorra Benjamin , López Redondo Juana , Ramos Angel M. , Santiago Juan G.
Published: January 2016

We consider a particular hydrodynamic focusing microfluidic mixer used to initiate the folding process of individual proteins, which has been designed in a previous work and exhibited a mixing time of 0.1 μs. The aim of the current paper is twofold. First, we explore the sensitivity of mixing time to key geometric and flow parameters. In particular, we study the angle between inlets, the shape of the channel intersections, channel widths, mixer depth, mixer symmetry, inlet velocities, working fluid physical properties, and denaturant concentration thresholds. Second, we analyze the uniformity of mixing times as a function of inlet flow streamlines. We find the shape of the intersection, channel width, inlet velocity ratio, and asymmetries have strong effects on mixing time; while inlet angles, mixer depth, fluid properties, and concentration thresholds have weaker effects. Also, the uniformity of the mixing time is preserved for most of the inlet flow and distances of down to within about 0.4 μm of the mixer wall. We offer these analyses of sensitivities to imperfections in mixer geometry and flow conditions as a guide to experimental efforts which aim to fabricate and use these types of mixers. Our study also highlights key issues and provides a guide to the optimization and practical design of other microfluidic devices dependent on both geometry and flow conditions.
Simulation-based study of wind loads on semi-submersed object in ocean wave field
Authors: Xie Shengbai , Yang Di , Liu Yi , Shen Lian
Published: January 2016

Wind forcing makes a vital contribution to the hydrodynamic loads on structures at sea. The flow physics is complex, involving interactions among surface water waves, turbulent wind, and semi-submersed object. We perform a simulation-based study on a canonical problem of wind past a semi-submersed rectangular prism with the focus on the wave effect, which is an essential factor in wind loads at sea but has been elusive. To tackle this problem, we develop a hybrid simulation method consisting of two parts: a precursor simulation of coupled wind and wave motions in the far field upstream to provide physical inflow condition, and a near-field simulation of the air and water motions around the object. The simulation method is validated through numerical tests and comparisons with data from the literature for different aspects of the code. This hybrid simulation method is then applied to study the effect of surface wave motions on the wind load on the object. Various wave conditions are considered, including pure wind-sea satisfying the Joint North Sea Wave Project spectrum as well as wind-sea mixed with long-wavelength ocean swells. The simulation results exhibit significant oscillations in the wind load on the object. The oscillations are found to correlate well with the incident wave motions and are particularly strong in the presence of swells. The underlying mechanism is explained through analyses on variations of wind speed with different wave phases and wave-correlated flow patterns of the wind when it impinges on the object. Our simulations also indicate that waves have an appreciable effect on the wake behind the object.
Resonance between heat-carrying electrons and Langmuir waves in inertial confinement fusion plasmas
Authors: Rozmus W. , Chapman T. , Brantov A. , Winjum B. J. , Berger R. L. , Brunner S. , Bychenkov V. Yu. , Tableman A. , Tzoufras M. , Glenzer S.
Published: January 2016

In ignition scale hot plasmas, temperature gradients and thermal transport modify electron distributions in a velocity range resonant with Langmuir waves typical of those produced by stimulated Raman scattering. We examine the resultant changes to the Landau damping experienced by these Langmuir waves and the levels of thermal plasma fluctuations. The form factor and Thomson scattering cross-section in such plasmas display unique characteristics of the background conditions. A theoretical model and high-order Vlasov-Fokker-Planck simulations are used in our analysis. An experiment to measure changes in thermal plasma fluctuation levels due to a thermal gradient is proposed.
Magnetic reconstructions in B-site doped manganites
Authors: Pradhan Kalpataru
Published: January 2016

The magnetic nature of the B-site dopants controls the magnetic phases in B-site doped manganites RE1−xAExMn1−ηBηO3. Different B-site dopants of equal valence, doped into the same reference manganite, lead to different magnetic phases at low temperature, which cannot be explained using the valence change scenario. We focus on trivalent B-site dopants in CE-CO-OO-I (CE-type antiferromagnet; CO: charge order; OO: orbital order; I: Insulator) manganites at half-filling x = 0.50 to study the role of magnetic interactions between the B-site dopants and the neighboring Mn-sites by using a two-orbital double-exchange model including super-exchange interactions, Jahn-Teller lattice distortions, and substitutional disorder in two dimensions. We show that the magnetic reconstructions around the B-site dopants due to the modified double-exchange and super-exchange interactions control the phase competition in B-site doped manganites.
Paramagnetic defects in KH2PO4 crystals with high concentration of embedded TiO2 nanoparticles
Authors: Grachev Valentin G. , Tse Romand , Malovichko Galina I. , Pritula Igor M. , Bezkrovnaya Olga N. , Kosinova Anna V.
Published: January 2016

Qualitative transformations of spectra of Electron Paramagnetic Resonance, EPR, were found in KH2PO4 crystals grown from liquor with 10−5–10−1 wt. % of anatase TiO2 nanoparticles in comparison with nominally pure KH2PO4. The nanoparticles have larger segregation coefficient for prismatic parts of the crystals than for pyramidal ones. Significant decrease in resonance absorption, complete disappearance of EPR lines of Fe3+ and Cr3+ centers, and appearance of four weak lines of equal intensities together with broad asymmetric lines with g-factors about 2.07–2.5 was observed in pyramidal parts grown with concentration of TiO2 nanoparticles larger than the threshold value 10−2 wt. %. The four lines were attributed to non-controlled impurity As substituted for P. In the presence of TiO2 nanoparticles, non-paramagnetic AsO43− clusters trap electrons becoming AsO44−. Disappearance of Fe3+ and Cr3+ centers was explained by their recharge to “EPR-silent” states and/or pairing at the surface of TiO2 nanoparticles.
Perspective: Mechanochemistry of biological and synthetic molecules
Authors: Makarov Dmitrii E.
Published: January 2016

Coupling of mechanical forces and chemical transformations is central to the biophysics of molecular machines, polymer chemistry, fracture mechanics, tribology, and other disciplines. As a consequence, the same physical principles and theoretical models should be applicable in all of those fields; in fact, similar models have been invoked (and often repeatedly reinvented) to describe, for example, cell adhesion, dry and wet friction, propagation of cracks, and action of molecular motors. This perspective offers a unified view of these phenomena, described in terms of chemical kinetics with rates of elementary steps that are force dependent. The central question is then to describe how the rate of a chemical transformation (and its other measurable properties such as the transition path) depends on the applied force. I will describe physical models used to answer this question and compare them with experimental measurements, which employ single-molecule force spectroscopy and which become increasingly common. Multidimensionality of the underlying molecular energy landscapes and the ensuing frequent misalignment between chemical and mechanical coordinates result in a number of distinct scenarios, each showing a nontrivial force dependence of the reaction rate. I will discuss these scenarios, their commonness (or its lack), and the prospects for their experimental validation. Finally, I will discuss open issues in the field.
Entropically induced asymmetric passage times of charged tracers across corrugated channels
Authors: Malgaretti Paolo , Pagonabarraga Ignacio , Miguel Rubi J.
Published: January 2016

We analyze the diffusion of charged and neutral tracers suspended in an electrolyte embedded in a channel of varying cross section. Making use of systematic approximations, the diffusion equation governing the motion of tracers is mapped into an effective 1D equation describing the dynamics along the longitudinal axis of the channel where its varying-section is encoded as an effective entropic potential. This simplified approach allows us to characterize tracer diffusion under generic confinement by measuring their mean first passage time (MFPT). In particular, we show that the interplay between geometrical confinement and electrostatic interactions strongly affect the MFTP of tracers across corrugated channels hence leading to alternative means to control tracers translocation across charged pores. Finally, our results show that the MFPTs of a charged tracer in opposite directions along an asymmetric channel may differ We expect our results to be relevant for biological as well synthetic devices whose dynamics is controlled by the detection of diluted tracers.
Anisotropy induced Kondo splitting in a mechanically stretched molecular junction: A first-principles based study
Authors: Wang Xiaoli , Hou Dong , Zheng Xiao , Yan YiJing
Published: January 2016

The magnetic anisotropy and Kondo phenomena in a mechanically stretched magnetic molecular junction are investigated by combining the density functional theory (DFT) and hierarchical equations of motion (HEOM) approach. The system is comprised of a magnetic complex Co(tpy–SH)2 sandwiched between adjacent gold electrodes, which is mechanically stretched in experiments done by Parks et al. [Science 328, 1370 (2010)]. The electronic structure and mechanical property of the stretched system are investigated via the DFT calculations. The HEOM approach is then employed to characterize the Kondo resonance features, based on the Anderson impurity model parameterized from the DFT results. It is confirmed that the ground state prefers the S = 1 local spin state. The structural properties, the magnetic anisotropy, and corresponding Kondo peak splitting in the axial stretching process are systematically evaluated. The results reveal that the strong electron correlations and the local magnetic properties of the molecule magnet are very sensitive to structural distortion. This work demonstrates that the combined DFT+HEOM approach could be useful in understanding and designing mechanically controlled molecular junctions.
Speeding up equation of motion coupled cluster theory with the chain of spheres approximation
Authors: Dutta Achintya Kumar , Neese Frank , Izsák Róbert
Published: January 2016

In the present paper, the chain of spheres exchange (COSX) approximation is applied to the highest scaling terms in the equation of motion (EOM) coupled cluster equations with single and double excitations, in particular, the terms involving integrals with four virtual labels. It is found that even the acceleration of this single term yields significant computational gains without compromising the desired accuracy of the method. For an excitation energy calculation on a cluster of five water molecules using 585 basis functions, the four virtual term is 9.4 times faster using COSX with a loose grid than using the canonical implementation, which yields a 2.6 fold acceleration for the whole of the EOM calculation. For electron attachment calculations, the four virtual term is 15 times and the total EOM calculation is 10 times faster than the canonical calculation for the same system. The accuracy of the new method was tested using Thiel’s test set for excited states using the same settings and the maximum absolute deviation over the whole test set was found to be 12.945 cm−1 (59 μHartree) for excitation energies and 6.799 cm−1 (31 μHartree) for electron attachments. Using MP2 amplitudes for the ground state in combination with the parallel evaluation of the full EOM equations in the manner discussed in this paper enabled us to perform calculations for large systems. Electron affinity values for the two lowest states of a Zn protoporphyrine model compound (224 correlated electrons and 1120 basis functions) were obtained in 3 days 19 h using 4 cores of a Xeon E5-2670 processor allocating 10 GB memory per core. Calculating the lowest two excitation energies for trans-retinal (114 correlated electrons and 539 basis functions) took 1 day 21 h using eight cores of the same processor and identical memory allocation per core.
Backbones in the parameter plane of the Hénon map
Authors: Falcolini Corrado , Tedeschini-Lalli Laura
Published: January 2016

Parameter plane (b, a) of the real Hénon map has been investigated for curves of bifurcation, curves of homoclinic heteroclinic onsets, and also searching for borders of areas variously characterized. Such curves are, in general, complicated and show singularities. Pieces of two monotone curves, spanning the (b, a) parameter plane of the real Hénon map, can be detected in four quite different studies appeared along the years 1982–2008. We study the extent of their similarity to read and interpret them into the same curves. To us, these two curves are the accumulation loci of bifurcation curves of two principal families of periodic sinks of type “period-adding machine.” We call them “backbones,” because they are monotone; moreover, they are the borders of some important regions in the (b, a)-plane. Hamouly and Mira in 1982 [C. R. Acad. Sc. Paris1 293, 525–528 (1982)] studied the structure of bifurcation of periodic orbits and their mutual position and intersection. Gonchenko et al. [SIAM J. Appl. Dyn. Syst. 4, 407–436 (2005)] display the continuation (in parameter plane) of the first heteroclinic connection and of the first homoclinic connection between the two fixed points of the map. Alligood and Sauer [Commun. Math. Phys. 120, 105–119 (1988)] studied parameter regions characterized by the same rotation number of the “accessible” periodic saddle. Finally, Lorenz [Physica D 237, 1689–1704 (2008)] in 2008 draws areas in the parameter plane statistically characterized by a finite attractor. In this paper, we show how these criteria interact. We therefore conjecture that the wealth of curves of homoclinic onsets could be in general hierarchized by the structure of accessible saddles.
Characterization of anisotropic acoustic metamaterial slabs
Authors: Park Jun Hyeong , Lee Hyung Jin , Kim Yoon Young
Published: January 2016

In an anisotropic acoustic metamaterial, the off-diagonal components of its effective mass density tensor should be considered in order to describe the anisotropic behavior produced by arbitrarily shaped inclusions. However, few studies have been carried out to characterize anisotropic acoustic metamaterials. In this paper, we propose a method that uses the non-diagonal effective mass density tensor to determine the behavior of anisotropic acoustic metamaterials. Our method accurately evaluates the effective properties of anisotropic acoustic metamaterials by separately dealing with slabs made of single and multiple unit cells along the thickness direction. To determine the effective properties, the reflection and transmission coefficients of an acoustic metamaterial slab are calculated, and then the wave vectors inside of the slab are determined using these coefficients. The effective material properties are finally determined by utilizing the spatial dispersion relation of the anisotropic acoustic metamaterial. Since the dispersion relation of an anisotropic acoustic metamaterial is explicitly used, its effective properties can be easily determined by only using a limited number of normal and oblique plane wave incidences into a metamaterial slab, unlike existing approaches requiring a large number of wave incidences. The validity of the proposed method is verified by conducting wave simulations for anisotropic acoustic metamaterial slabs with Z-shaped elastic inclusions of tilted principal material axes.
Power absorption in acoustically driven ferromagnetic resonance
Authors: Labanowski D. , Jung A. , Salahuddin S.
Published: January 2016

Surface acoustic waves (SAWs) have recently been used to drive ferromagnetic resonance by exploiting the coupling between strain and magnetization in magnetostrictive materials in a technique called acoustically driven ferromagnetic resonance (ADFMR). In this work, we quantitatively examine the power absorbed by the magnetic elements in such systems. We find that power absorption scales exponentially with the length of the magnetic element in the direction of SAW propagation, with the rate of scaling set by the thickness of magnetic material. In addition, we find that ADFMR behaves consistently across a wide range of input power values (>65 dB). Our results indicate that devices such as filters, oscillators, and sensors can be designed that operate with very low power, yet provide high tunability.
Ferroelectricity and magnetoelectric coupling in h-YbMnO3: Spin reorientation and defect effect
Authors: Qiang Gang , Fang Yifei , Lu Xiaowen , Cao Shixun , Zhang Jincang
Published: January 2016

Low-temperature magnetic and electric properties in hexagonal multiferroic compound YbMnO3 were studied. The Mn3+ spin moments order at TN = 85 K and reoriented around 43.5 K, leading to the magnetic phase transition from B2(P63cm) → A2(P63cm). The concomitant ferroelectric polarization is observed and explained microscopically by the destruction of initial symmetric relationship of the polarization between the upper and lower half of the magnetic unit cell. The asymmetry of the polarization vs temperature curves under opposite poling voltage revealed the pinning effect of the defects on the electrical polarization.
Comparison of short-channel effects in monolayer MoS2 based junctionless and inversion-mode field-effect transistors
Authors: Agarwal Tarun , Sorée Bart , Radu Iuliana , Raghavan Praveen , Fiori Gianluca , Iannaccone Giuseppe , Thean Aaron , Heyns Marc , Dehaene Wim
Published: January 2016

Conventional junctionless (JL) multi-gate (MuG) field-effect transistors (FETs) require extremely scaled channels to deliver high on-state current with low short-channel effect related leakage. In this letter, using ultra-thin 2D materials (e.g., monolayer MoS2), we present comparison of short-channel effects in JL, and inversion-mode (IM) FETs. We show that JL FETs exhibit better sub-threshold slope (S.S.) and drain-induced-barrier-lowering (DIBL) in comparison to IM FETs due to reduced peak electric field at the junctions. But, threshold voltage (VT) roll-off with channel length downscaling is found to be significantly higher in JL FETs than IM FETs, due to higher source/drain controlled charges (dE/dx) in the channel. Further, we show that although VT roll-off in JL FETs improves by increasing the gate control, i.e., by scaling the oxide, or channel thickness, the sensitivity of threshold voltage on structural parameters is found out to be high.
Self-assembly of colloidal bands driven by a periodic external field
Authors: Nunes André S. , Araújo Nuno A. M. , Telo da Gama Margarida M.
Published: January 2016

We study the formation of bands of colloidal particles driven by periodic external fields. Using Brownian dynamics, we determine the dependence of the band width on the strength of the particle interactions and on the intensity and periodicity of the field. We also investigate the switching (field-on) dynamics and the relaxation times as a function of the system parameters. The observed scaling relations were analyzed using a simple dynamic density-functional theory of fluids.
Pseudopotential-based electron quantum transport: Theoretical formulation and application to nanometer-scale silicon nanowire transistors
Authors: Fang Jingtian , Vandenberghe William G. , Fu Bo , Fischetti Massimo V.
Published: January 2016

We present a formalism to treat quantum electronic transport at the nanometer scale based on empirical pseudopotentials. This formalism offers explicit atomistic wavefunctions and an accurate band structure, enabling a detailed study of the characteristics of devices with a nanometer-scale channel and body. Assuming externally applied potentials that change slowly along the electron-transport direction, we invoke the envelope-wavefunction approximation to apply the open boundary conditions and to develop the transport equations. We construct the full-band open boundary conditions (self-energies of device contacts) from the complex band structure of the contacts. We solve the transport equations and present the expressions required to calculate the device characteristics, such as device current and charge density. We apply this formalism to study ballistic transport in a gate-all-around (GAA) silicon nanowire field-effect transistor with a body-size of 0.39 nm, a gate length of 6.52 nm, and an effective oxide thickness of 0.43 nm. Simulation results show that this device exhibits a subthreshold slope (SS) of ∼66 mV/decade and a drain-induced barrier-lowering of ∼2.5 mV/V. Our theoretical calculations predict that low-dimensionality channels in a 3D GAA architecture are able to meet the performance requirements of future devices in terms of SS swing and electrostatic control.
Presence of monovalent oxygen anions in oxides demonstrated using X-ray photoelectron spectra
Authors: Wu L. Q. , Li S. Q. , Li Y. C. , Li Z. Z. , Tang G. D. , Qi W. H. , Xue L. C. , Ding L. L. , Ge X. S.
Published: January 2016

The oxygen vacancy model has been used to explain the magnetic and electrical transport properties of dilute magnetic semiconductors and resistive switching. In particular, some authors have claimed that they found a symmetric peak corresponding to the oxygen vacancies in O1s photoelectron spectra. In this paper, using X-ray photoelectron spectra with argon ion etching, it is shown that this symmetric peak may also be interpreted as being related to O1− anions, rather than to oxygen vacancies.
Darkfield microspectroscopy of nanostructures on silver tip-enhanced Raman scattering probes
Authors: Itoh Tamitake , Yamamoto Yuko S. , Suzuki Toshiaki , Kitahama Yasutaka , Ozaki Yukihiro
Published: January 2016

We report an evaluation method employing darkfield microspectroscopy for silver probes used in tip-enhanced Raman scattering (TERS). By adjusting the darkfield illumination, the diffracted light from the probe outlines disappears and the diffracted light from the surface nanostructures and tips of the probes appears as colorful spots. Scanning electron microscopy reveals that the spectral variations in these spots reflect the shapes of the surface nanostructures. The tip curvatures correlate to the spectral maxima of their spots. Temporal color changes in the spots indicate the deterioration due to the oxidation of the silver surfaces. These results show that the proposed method is useful for in situ evaluation of plasmonic properties of TERS probes.
A molecular dynamics study of the breathing and deforming modes of the spherical ionic SDS and nonionic C12E8 micelles
Authors: Wang Lin , Fujimoto Kazushi , Yoshii Noriyuki , Okazaki Susumu
Published: January 2016

In order to investigate shape of the micelles and its thermal fluctuations, molecular dynamics calculations have been performed for spherical ionic sodium dodecyl sulfate (SDS) and nonionic octaethyleneglycol monododecyl ether (C12E8) micelles. New statistical functions suitable for extracting the fluctuations of the shape of the spherical micelles were defined using spherical harmonics and Legendre polynomials. The breathing and deforming modes of the SDS and C12E8 micelles were analyzed in detail based on these new functions. The elastic nature of the micelle core was also discussed. The present analysis gives a new molecular picture that the micelle shape is a superposition of the various kinds of breathing and deforming modes, and each mode has a specific relaxation time of the shape fluctuation.
In-situ transmission electron microscopy growth of nanoparticles under extreme conditions
Authors: Luce F. P. , Oliviero E. , Azevedo G. de M. , Baptista D. L. , Zawislak F. C. , Fichtner P. F. P.
Published: January 2016

The formation and time resolved behavior of individual Pb nanoparticles embedded in silica have been studied by in-situ transmission electron microscopy observations at high temperatures (400–1100 °C) and under 200 keV electron irradiation. It is shown that under such extreme conditions, nanoparticles can migrate at long distances presenting a Brownian-like behavior and eventually coalesce. The particle migration phenomenon is discussed considering the influence of the thermal energy and the electron irradiation effects on the atomic diffusion process which is shown to control particle migration. These results and comparison with ex-situ experiments tackle the stability and the microstructure evolution of nanoparticles systems under extreme conditions. It elucidates on the effects of energetic particle irradiation-annealing treatments either as a tool or as a detrimental issue that could hamper their long-term applications in radiation-harsh environments such as in space or nuclear sectors.
Phase structure and piezoelectric properties of (1−x)K0.48Na0.52Nb0.95Sb0.05O3-x(Bi0.5Na0.5)0.9(Li0.5Ce0.5)0.1ZrO3 lead-free piezoelectric ceramics
Authors: Xing Jie , Tan Zhi , Jiang Laiming , Chen Qiang , Wu Jiagang , Zhang Wen , Xiao Dingquan , Zhu Jianguo
Published: January 2016

(1−x)K0.48Na0.52Nb0.95Sb0.05O3-x(Bi0.5Na0.5)0.9(Li0.5Ce0.5)0.1ZrO3 [(1−x)KNNS-xBNLCZ] lead-free piezoceramics were prepared by the conventional solid state sintering method. The effects of BNLCZ contents on their phase structure, microstructure, and piezoelectric properties were investigated. All the samples show a pure perovskite structure, and no secondary phases were formed in the detected range. The rhombohedral and tetragonal phases of (1−x)KNNS-xBNLCZ coexist in the composition range of 0.0325 ≤ x ≤ 0.0425 at room temperature. A remarkably strong piezoelectricity was obtained by the addition of appropriate BNLCZ contents. The excellent piezoelectric properties of the ceramics with x = 0.04 were obtained: d33 ∼ 485 pC/N, kp ∼ 48%, and TC ∼ 227 °C. All the results show that the introduction of (Bi0.5Na0.5)0.9(Li0.5Ce0.5)0.1ZrO3 is a very effective way to form the rhombohedral and tetragonal phase coexistence of potassium-sodium niobate-based ceramics, which can improve its piezoelectric properties.