bluuebunny/crossref_metadata_2025 huggingface dataset:
Why Does Political Science Hate American Indians?
Authors: Ferguson Kennan
Published: December 2016

Native Americans have been structurally excluded from the discipline of political science in the continental United States, as has Native epistemology and political issues. I analyze the reasons for these erasures and elisions, noting the combined effects of rejecting Native scholars, political issues, analysis, and texts. I describe how these arise from presumptions inherent to the disciplinary practices of U.S. political science, and suggest a set of alternative formulations that could expand our understanding of politics, including attention to other forms of law, constitutions, relationships to the environment, sovereignty, collective decision-making, U.S. history, and majoritarianism.
Sovereignty and Survivance—The Pathways of Native Politics
Authors: Carpenter Daniel
Published: December 2016

Native Americans have been structurally excluded from the discipline of political science in the continental United States, as has Native epistemology and political issues. I analyze the reasons for these erasures and elisions, noting the combined effects of rejecting Native scholars, political issues, analysis, and texts. I describe how these arise from presumptions inherent to the disciplinary practices of U.S. political science, and suggest a set of alternative formulations that could expand our understanding of politics, including attention to other forms of law, constitutions, relationships to the environment, sovereignty, collective decision-making, U.S. history, and majoritarianism.
Research Cycles: Adding More Substance to the Spin
Authors: Elman Colin , Burton Colleen Dougherty
Published: December 2016

In sciences such as biomedicine, researchers and journal editors are well aware that progress in answering difficult questions generally requires movement through a research cycle: Research on a topic or problem progresses from pure description, through correlational analyses and natural experiments, to phased randomized controlled trials (RCTs). In biomedical research all of these research activities are valued and find publication outlets in major journals. In political science, however, a growing emphasis on valid causal inference has led to the suppression of work early in the research cycle. The result of a potentially myopic emphasis on just one aspect of the cycle reduces incentives for discovery of new types of political phenomena, and more careful, efficient, transparent, and ethical research practices. Political science should recognize the significance of the research cycle and develop distinct criteria to evaluate work at each of its stages.
Of Research Cycles and Publication Models
Authors: McClure Kirstie M.
Published: December 2016

This response to Prof. Lieberman’s essay questions its analogy between “biomedical research” and the academic discipline of political science. Focused on the disanalogy of scope and scale between the two, it takes issue not with the “criterial framework” he offers, but with the quality of argumentation that leads us there. Supplementing the essay’s impressionistic account of editorial practice with evidence drawn from the New England Journal of Medicine and the publishing history of APSA journals since the 1960s, I suggest that the issue here is not simply editorial virtue and professional norms, but differences in the material and institutional bases of the journals’ alternative publication models.
Avoiding the Trivialization of Political Science
Authors: Falleti Tulia G.
Published: December 2016

I extensively agree with Lieberman’s main argument and especially with his recommendations to graduate students and journal editors, which come at a critical time for our discipline’s development and future relevance. However, I depart from Lieberman on two issues. First, I argue that the research cycle is circular, and not teleological as Lieberman implies. For instance, randomized control trial (RCT) studies could be the start (and not the end) of a research cycle that leads to more descriptive and qualitative analysis in order to improve our understanding of causality. Second, I believe that the size of effects in RCT studies does matter, among other reasons because small effects might be symptoms of defective conceptualization of the main research problem.
Why Would a Political Scientist Write a Biography?
Authors: Sparrow Bartholomew
Published: December 2016

Why would a political scientist write a biography of a U.S. national security advisor? Biography focuses on a single individual and has no guidelines on where or how to collect evidence or on how to organize that evidence. Nonetheless, a biography of General Brent Scowcroft, national security advisor to Presidents Gerald Ford and George H.W. Bush, allowed me to provide a broad overview of forty years of U.S. foreign policy history, to conduct an in-depth study of the personnel and organization involved in the national security decision-making, and to narrate the life of an extremely influential and interesting public figure. Biography fulfills many of political science’s disciplinary objectives, in fact: it speaks to important issues of political science, it offers thick description and facilitates the drawing of causal inferences, it addresses agency and structure, it is falsifiable, and it is able to communicate with a larger public.
A Discussion of Robert Vitalis's White World Order, Black Power Politics: The Birth of American International Relations
Authors: Crawford Neta
Published: December 2016

In White World Order, Black Power Politics: The Birth of American International Relations, Robert Vitalis presents a critical disciplinary history of the field of international relations, and the discipline of political science more broadly. Vitalis argues that the interconnections between imperialism and racism were “constitutive” of international relations scholarship in the U.S. since the turn of the 20th century, and that the perspectives of a generation of African-American scholars that included W. E. B. Dubois, Alain Locke, and Ralph Bunche were equally constitutive of this scholarship—by virtue of the way the emerging discipline sought to marginalize these scholars. In developing this argument, Vitalis raises questions about the construction of knowledge and the racial foundations of American political development. These issues lie at the heart of U.S. political science, and so we have invited a range of political scientists to comment on the book and its implications for our discipline.
A Discussion of Robert Vitalis’s White World Order, Black Power Politics: The Birth of American International Relations
Authors: Ling L.H.M.
Published: December 2016

In White World Order, Black Power Politics: The Birth of American International Relations, Robert Vitalis presents a critical disciplinary history of the field of international relations, and the discipline of political science more broadly. Vitalis argues that the interconnections between imperialism and racism were “constitutive” of international relations scholarship in the U.S. since the turn of the 20th century, and that the perspectives of a generation of African-American scholars that included W. E. B. Dubois, Alain Locke, and Ralph Bunche were equally constitutive of this scholarship—by virtue of the way the emerging discipline sought to marginalize these scholars. In developing this argument, Vitalis raises questions about the construction of knowledge and the racial foundations of American political development. These issues lie at the heart of U.S. political science, and so we have invited a range of political scientists to comment on the book and its implications for our discipline.
A Discussion of Robert Vitalis’s White World Order, Black Power Politics: The Birth of American International Relations
Authors: Sabaratnam Meera
Published: December 2016

In White World Order, Black Power Politics: The Birth of American International Relations, Robert Vitalis presents a critical disciplinary history of the field of international relations, and the discipline of political science more broadly. Vitalis argues that the interconnections between imperialism and racism were “constitutive” of international relations scholarship in the U.S. since the turn of the 20th century, and that the perspectives of a generation of African-American scholars that included W. E. B. Dubois, Alain Locke, and Ralph Bunche were equally constitutive of this scholarship—by virtue of the way the emerging discipline sought to marginalize these scholars. In developing this argument, Vitalis raises questions about the construction of knowledge and the racial foundations of American political development. These issues lie at the heart of U.S. political science, and so we have invited a range of political scientists to comment on the book and its implications for our discipline.
A Discussion of Dawn Langan Teele’s Field Experiments and Their Critics: Essays on the Uses and Abuses of Experimentation in the Social Sciences
Authors: Schwartz-Shea Peregrine
Published: December 2016

Experimental approaches to political science research have become increasingly prominent in the discipline. Experimental research is regularly featured in some of the discipline’s top journals, and indeed in 2014 a new Journal of Experimental Political Science was created, published by Cambridge University Press. At the same time, there are disagreements among political scientists about the limits of experimental research, the ethical challenges associated with this research, and the general model of social scientific inquiry underlying much experimental research. Field Experiments and Their Critics: Essays on the Uses and Abuses of Experimentation in the Social Sciences, edited by Dawn Langan Teele (Yale University Press 2015), brings together many interesting perspectives on these issues. And so we have invited a number of political scientists to comment on the book, the issues it raises, and the more general question of “the uses and abuses of experimentation in the social sciences.”
A Discussion of Dawn Langan Teele’s Field Experiments and Their Critics: Essays on the Uses and Abuses of Experimentation in the Social Sciences
Authors: Sinclair Betsy
Published: December 2016

Experimental approaches to political science research have become increasingly prominent in the discipline. Experimental research is regularly featured in some of the discipline’s top journals, and indeed in 2014 a new Journal of Experimental Political Science was created, published by Cambridge University Press. At the same time, there are disagreements among political scientists about the limits of experimental research, the ethical challenges associated with this research, and the general model of social scientific inquiry underlying much experimental research. Field Experiments and Their Critics: Essays on the Uses and Abuses of Experimentation in the Social Sciences, edited by Dawn Langan Teele (Yale University Press 2015), brings together many interesting perspectives on these issues. And so we have invited a number of political scientists to comment on the book, the issues it raises, and the more general question of “the uses and abuses of experimentation in the social sciences.”
A Discussion of Josiah Ober’s The Rise and Fall of Classical Greece
Authors: Carugati Federica
Published: December 2016

Ancient Greece has long exercised a powerful hold on the imagination of modern political science. But until fairly recently, this influence has largely been philosophical, related to the origins of many theoretical concepts—including the concept of politics itself—in the ancient world. In The Rise and Fall of Classical Greece, Josiah Ober offers a synoptic and ambitious social theoretical account of the ancient Greek world, the sources of its power, the causes of its decline, and the lessons that can be drawn from this story for contemporary social and political science. We have thus invited a range of political scientists to comment on Ober’s account of classical Greece and its relevance to contemporary political inquiry.
A Discussion of Josiah Ober’s The Rise and Fall of Classical Greece
Authors: Monoson S. Sara
Published: December 2016

Ancient Greece has long exercised a powerful hold on the imagination of modern political science. But until fairly recently, this influence has largely been philosophical, related to the origins of many theoretical concepts—including the concept of politics itself—in the ancient world. In The Rise and Fall of Classical Greece, Josiah Ober offers a synoptic and ambitious social theoretical account of the ancient Greek world, the sources of its power, the causes of its decline, and the lessons that can be drawn from this story for contemporary social and political science. We have thus invited a range of political scientists to comment on Ober’s account of classical Greece and its relevance to contemporary political inquiry.
A Discussion of Josiah Ober’s The Rise and Fall of Classical Greece
Authors: Saxonhouse Arlene W.
Published: December 2016

Ancient Greece has long exercised a powerful hold on the imagination of modern political science. But until fairly recently, this influence has largely been philosophical, related to the origins of many theoretical concepts—including the concept of politics itself—in the ancient world. In The Rise and Fall of Classical Greece, Josiah Ober offers a synoptic and ambitious social theoretical account of the ancient Greek world, the sources of its power, the causes of its decline, and the lessons that can be drawn from this story for contemporary social and political science. We have thus invited a range of political scientists to comment on Ober’s account of classical Greece and its relevance to contemporary political inquiry.
A Discussion of Josiah Ober’s The Rise and Fall of Classical Greece
Authors: Schwartzberg Melissa
Published: December 2016

Ancient Greece has long exercised a powerful hold on the imagination of modern political science. But until fairly recently, this influence has largely been philosophical, related to the origins of many theoretical concepts—including the concept of politics itself—in the ancient world. In The Rise and Fall of Classical Greece, Josiah Ober offers a synoptic and ambitious social theoretical account of the ancient Greek world, the sources of its power, the causes of its decline, and the lessons that can be drawn from this story for contemporary social and political science. We have thus invited a range of political scientists to comment on Ober’s account of classical Greece and its relevance to contemporary political inquiry.
Land rights and neoliberalism: an irreconcilable conflict for indigenous peoples in India?
Authors: Sigamany Indrani
Published: December 2016

Does legislation that grants land rights necessarily ensure justice? The Forest Rights Act of 2006 (FRA) in India, a landmark social justice law, aims to enhance land security for forest peoples. Increasingly displaced by development and extractive industries that intensify impoverishment, indigenous peoples in India should, with the FRA, be able to protect their land, their livelihoods and their culture. Continued government violations of forest land rights in the name of development highlight that economically vulnerable populations lack the power to take advantage of legislation. I examine the tension of current indigenous land struggles in the context of the legal frameworks of the FRA and the neoliberal culture of India.
Twenty years after Novye Atagi: A call to care for the carers
Authors: Hensch Christoph
Published: December 2016

Working in the humanitarian sector as an aid worker has become a dangerous endeavour, with attacks against humanitarian workers becoming more common. In this personal story by a former head of office at an International Committee of the Red Cross (ICRC) surgical hospital, a short, violent encounter leads to a long journey of recovery. There is an important role for the community in supporting the healing process; the author suggests that an integral and collaborative involvement by organizations like the ICRC is effective in addressing the impact of violence directed towards humanitarian aid workers.
Enhanced susceptibility of CA3 hippocampus to prenatal nicotine exposure
Authors: Kalejaiye O. O. , Gondré-Lewis M. C.
Published: December 2016

The brain is highly susceptible to adverse effects of drugs of abuse during early phases of life. Prenatal nicotine exposure (PNE), a preventable cause of gestational and infant mortality, can alter neuron wiring and induce sustained deficits in attention and learning. Here, a rat model of PNE (embryonic days 7–21) was used to examine the maturing hippocampus, which encodes new memories and processes emotional memory. Components of synaptic signaling were evaluated at postnatal day 14 (P14), a period of prolific synaptogenesis in rats, to determine if glutamatergic transmission-associated molecules are regulated in subregions of hippocampus as early as P14. PNE resulted in reduced expression of GluN2B, GluA2 and CaMKIIα, but elevated SNAP25 proteins specifically in the CA3 but not CA1. Only CaMKIIα was regulated in dentate gyrus at this age. These results suggest that glutamatergic and synaptic dysregulation of learning and memory may occur in hippocampus in a temporally and subregionally specific manner.
Ellen R. M. Druffel Receives 2016 Roger Revelle Medal
Authors:   AGU
Published: December 2016

Ellen R. M. Druffel was awarded the 2016 Roger Revelle Medal at the American Geophysical Union Fall Meeting Honors Ceremony, held on 14 December 2016 in San Francisco, Calif. The medal is for "outstanding contributions in atmospheric sciences, atmosphere-ocean coupling, atmosphere-land coupling, biogeochemical cycles, climate or related aspects of the Earth system."
Preparation, characterization and antibiotic properties of silver–silicon nanocomposites
Authors: Chang Huan , Gao Wei , Sun Xiangyu , Tan Hui , Sun Shuqing
Published: December 2016

Ag nanoparticles supported on porous silicon showing excellent antibiotic properties against both E. coli and S. aureus were presented.
An array of WO3 and CTO heterojunction semiconducting metal oxide gas sensors used as a tool for explosive detection
Authors: Horsfall Lauren A. , Pugh David C. , Blackman Christopher S. , Parkin Ivan P.
Published: December 2016

An array of WO3 and CTO heterojunction semiconducting metal oxide gas sensors used for the detection of explosives.
Introduction of metal precursors by electrodeposition for the in situ growth of metal–organic framework membranes on porous metal substrates
Authors: Zhou Sheng , Wei Yanying , Zhuang Libin , Ding Liang-Xin , Wang Haihui
Published: December 2016

An efficient and generalizable strategy assisted by electrodeposition was developed for the in situ growth of various MOF membranes.
Unusual formation of tetragonal microstructures from nitrogen-doped carbon nanocapsules with cobalt nanocores as a bi-functional oxygen electrocatalyst
Authors: Hu Enlai , Ning Jiqiang , He Bin , Li Zhipeng , Zheng Changcheng , Zhong Yijun , Zhang Ziyang , Hu Yong
Published: December 2016

A novel electrocatalyst based on nitrogen-doped carbon nanocapsules containing metallic cobalt nanoparticle (Co–N–C) tetragonal microstructures was firstly synthesized.
Improving endothelialization by the combined application of polyethylene glycol coated cerium oxide nanoparticles and VEGF in electrospun polyurethane scaffolds
Authors: Dai Wei-Wei , Guo Hong-Feng , Qian De-Hui , Qin Zhe-Xue , Lei Yan , Hou Xiao-Yu , Wen Can
Published: December 2016

CNPs-PEG/VEGF loaded electrospun PU scaffolds inhibit oxidative stress-induced EPC apoptosis as well as promote endothelializationin vitro.
A tumor-targeting and lysosome-specific two-photon fluorescent probe for imaging pH changes in living cells
Authors: Dong Baoli , Song Xuezhen , Kong Xiuqi , Wang Chao , Zhang Nan , Lin Weiying
Published: December 2016

Lysosomal pH is closely related to the metastasis and apoptosis of cancer cells.
Electrosprayed large-area membranes of Ag-nanocubes embedded in cellulose acetate microspheres as homogeneous SERS substrates
Authors: Ke Yan , Meng Guowen , Huang Zhulin , Zhou Ningning
Published: December 2016

Large-area electrosprayed membranes consisting of Ag-nanocubes embedded in cellulose acetate microspheres as SERS substrates with remarked homogeneous signals.
Tunable white light of multi-cation-site Na2BaCa(PO4)2:Eu,Mn phosphor: synthesis, structure and PL/CL properties
Authors: Cao Yaxin , Ding Jianyan , Ding Xin , Wang Xicheng , Wang Yuhua
Published: December 2016

The luminescence investigation on Na2BaCa(PO4)2:Eu,Mn: color tunable phosphors with multi-cation-sites and good thermal stability.
Gold nanodisc arrays as near infrared metal-enhanced fluorescence platforms with tuneable enhancement factors
Authors: Pang J. , Theodorou I. G. , Centeno A. , Petrov P. K. , Alford N. M. , Ryan M. P. , Xie F.
Published: December 2016

Au nanodisc arrays with nanoscale control of their structural characteristics, allow significant NIR fluorescence enhancement with tunable sensitivities.
New insights into the microstructure of translucent CaAlSiN3:Eu2+ phosphor ceramics for solid-state laser lighting
Authors: Li Shuxing , Tang Daiming , Tian Zifeng , Liu Xuejian , Takeda Takashi , Hirosaki Naoto , Xu Fangfang , Huang Zhengren , Xie Rong-Jun
Published: December 2016

Detailed microstructures and performances as well as the relationships between them have been analyzed.
SIG 17 Perspectives Vol. 2, No. 1, May 2012
Authors: Domsch Celeste
Published: December 2016

Sorry, this activity is no longer available for CEUs. Visit the SIG 17 page on the
ASHA Store
to see available CE activities.

Use the CE questions PDF here as study questions to guide your Perspectives reading.
Dysphagia in Persons with Dementia: The Dual Diagnosis Challenge
Authors: Tristani Michelle
Published: December 2016

“While there is life, we must provide quality of life.” Paul Raia

Swallowing and cognition have always been considered two major contributors to quality of life. It's interesting to note, for example, when someone asks for directions, instructions are often provided by using favorite restaurants as landmarks. It is customary for many people spend significant amounts of time and effort accessing executive functions to plan, organize, and cook daily meals as well as to prepare for special occasions and holidays. The enjoyment experienced by sharing a meal with friends and family members is positively anticipated.

The evaluation of functional and quality of life outcomes continues to emerge as a vital component of state-of-the-art health care. Specific to the field of medical speech-language pathology, any discussions pertaining to dementia and/or dysphagia bring quality of life issues to the forefront. Dysphagia as a sequelae of dementia is understood to have significant negative impacts on quality of life due to the challenges associated with its management in persons with progressive, degenerative neuropathology and resulting cognitive, sensory, and motor decline.
Altered Regional Myocardial Mechanics in Transplanted Hearts: Influence of Time and Transplantation
Authors: Stephan Anna , Grundmann Sebastian , Föll Daniela , Beyersdorf Friedhelm , Bode Christoph , Geibel Annette , Wengenmayer Tobias
Published: December 2016

Background Global longitudinal strain is reduced in heart transplant recipients, but little is known about regional contractility of the transplanted heart. Moreover, it is unclear if factors such as time after transplant and ischemic time have an influence on regional contractility. To test for regional changes in myocardial deformation, we assessed regional myocardial deformation using three-dimensional speckle tracking echocardiography in heart transplant recipients and controls.

Methods Global and regional longitudinal, circumferential, and radial strain was assessed in 51 heart transplant recipients and a control group of healthy individuals (n = 26). Moreover, we correlated regional contractility with clinical characteristics and compared subgroups of heart transplant recipients with normal (n = 32) and reduced left ventricular ejection fraction (n = 32).

Results Global longitudinal and circumferential strain was significantly reduced in all heart transplant recipients, as well as in the transplant group with normal ejection fraction compared with the control group (p < 0.001). Global radial strain (GRS) was elevated in both transplant groups, but was significantly higher in transplant recipients with normal ejection fraction compared with the control group (p < 0.01). Both transplant groups revealed lower longitudinal and circumferential strain values in the mid- and apical regions (p < 0.001), whereas longitudinal and circumferential strain was higher in the basal region (p < 0.01). In both groups, transplanted hearts showed increased radial strain in the basal (p < 0.05, p < 0.01) and midregions (p = 0.22; p < 0.01) and did not differ in the apical regions. Cold ischemic time (150 ± 12.6 minutes) was independently associated with reduction in circumferential strain. Time since transplantation ranging from 18 days to 21 years had no effect on myocardial deformation parameters.

Conclusion Left ventricular mechanics in transplanted hearts display significantly different systolic deformation patterns than native hearts. Strain capability forms a regional gradient from the base toward the apex. The presence of a time-independent deformation pattern and the correlation with cold ischemic time suggest damage induced by the transplantation itself. These findings might be important for understanding pseudo-abnormal echocardiograms in heart transplant patients.
Ex vacuo atom chip Bose-Einstein condensate
Authors: Squires Matthew B. , Olson Spencer E. , Kasch Brian , Stickney James A. , Erickson Christopher J. , Crow Jonathan A. R. , Carlson Evan J. , Burke John H.
Published: December 2016

Ex vacuo atom chips, used in conjunction with a custom thin walled vacuum chamber, have enabled the rapid replacement of atom chips for magnetically trapped cold atom experiments. Atoms were trapped in >2 kHz magnetic traps created using high power atom chips. A thin walled vacuum chamber allowed the atoms to be trapped ≲1 mm from the atom chip conductors which were located outside of the vacuum system. Placing the atom chip outside of the vacuum simplified the electrical connections and improved the thermal management. Using a multi-lead Z-wire chip design, a Bose-Einstein condensate was produced with an external atom chip. Vacuum and optical conditions were maintained while replacing the Z-wire chip with an atom chip with a cross-wire design. The atom chips were exchanged and an initial magnetic trap was achieved in less than 3 h.
Speckle contrast reduction of laser light using a chiral nematic liquid crystal diffuser
Authors: Hansford David J. , Fells Julian A. J. , Elston Steve J. , Morris Stephen M.
Published: December 2016

High coherence in laser light causes spatially distributed interference called speckle. In applications such as holographic projection, this undesirable side effect degrades image clarity. The current methods of speckle reduction, such as a rotating ground-glass diffuser, require additional bulky moving parts. Here, we present an alternative technology based upon a compact, electrohydrodynamic chiral nematic liquid crystal device. A spatially random phase modulation of the incident light is achieved through the electrohydrodynamic instabilities that are induced by an alternating electric field. Using a chiral nematic liquid crystal device that is doped with an ionic compound, we find that the speckle contrast can be reduced by as much as 80%.
An implementation of discrete electron transport models for gold in the Geant4 simulation toolkit
Authors: Sakata D. , Incerti S. , Bordage M. C. , Lampe N. , Okada S. , Emfietzoglou D. , Kyriakou I. , Murakami K. , Sasaki T. , Tran H. , Guatelli S. , Ivantchenko V. N.
Published: December 2016

Gold nanoparticle (GNP) boosted radiation therapy can enhance the biological effectiveness of radiation treatments by increasing the quantity of direct and indirect radiation-induced cellular damage. As the physical effects of GNP boosted radiotherapy occur across energy scales that descend down to 10 eV, Monte Carlo simulations require discrete physics models down to these very low energies in order to avoid underestimating the absorbed dose and secondary particle generation. Discrete physics models for electron transportation down to 10 eV have been implemented within the Geant4-DNA low energy extension of Geant4. Such models allow the investigation of GNP effects at the nanoscale. At low energies, the new models have better agreement with experimental data on the backscattering coefficient, and they show similar performance for transmission coefficient data as the Livermore and Penelope models already implemented in Geant4. These new models are applicable in simulations focussed towards estimating the relative biological effectiveness of radiation in GNP boosted radiotherapy applications with photon and electron radiation sources.
Bender-Wu singularities
Authors: Giachetti Riccardo , Grecchi Vincenzo
Published: December 2016

We consider the properties of the family of double well quantum Hamiltonians Hħ = − ħ2 (d2/dx2) + i(x3 − x), x ∈ ℝ, ħ > 0, starting from the resonances of the cubic oscillator Hϵ = − (d2/dx2) + x2 + ϵx3, ϵ > 0, and studying their analytic continuations obtained by generalized changes of representation. We prove the existence of infinite crossings of the eigenvalues of Hħ together with the selection rules of the pairs of eigenvalues taking part in a crossing. This is a semiclassical localization effect. The eigenvalues at the crossings accumulate at a critical energy for some of the Stokes lines.
Fractional formalism to DNA chain and impact of the fractional order on breather dynamics
Authors: Mvogo Alain , Kofané Timoléon Crépin
Published: December 2016

We have investigated the impact of the fractional order derivative on the dynamics of modulated waves of a homogeneous DNA chain that is based on site-dependent finite stacking and pairing enthalpies. We have reformulated the classical Lagrangian of the system by including the coordinates depending on the Riemann-Liouville time derivative of fractional order γ. From the Lagrange equation, we derived the fractional nonlinear equation of motion. We obtained the fractional breather as solutions by means of a fractional perturbation technique. The impact of the fractional order is investigated and we showed that depending on the values of γ, there are three types of waves that propagate in DNA. We have static breathers, breathers of small amplitude and high velocity, and breathers of high amplitude and small velocity.
Investigation of powder dynamics in silane-argon discharge using impedance analyser
Authors: Chaudhary Deepika , Sharma Mansi , Sudhakar S. , Kumar Sushil
Published: December 2016

We report the growth of powder formation in Argon (Ar) diluted Silane (SiH4) plasma using 27.12 MHz assisted Plasma Enhanced Chemical Vapor Deposition process with the approach of plasma diagnosis. The appearance of powder during processing contaminates the process chamber which further can alter the film properties; hence plasma diagnosis was vital towards detecting this variation. This work presents for the first time a diagnosis of powder in the plasma using Impedance Analyser (V/I probe) at various concentrations of Argon dilution (10%–90%), chamber pressure (0.3 Torr–0.6 Torr), and applied power (4 W–20 W). Efforts were made to understand the different phases of powder formation (i.e., chain and accumulation process, coalescence phase and α → γ′ transition (powder zone)) by monitoring and evaluating the plasma characteristics such as discharge voltage and current (Vrms and Irms), Impedance (Z), phase angle (ϕ), electron density (ne), bulk field (Eb), and sheath width (ds). From the results of plasma characterization, the coalescence phase can be well diagnosed by the low amplitude of Irms, ϕ, ne, and ds in combination with a high amplitude of Vrms and Eb whereas α → γ′ transition regime diagnose by a lower value of Vrms, Z, ϕ, Eb, and ds with a higher value of Irms and ne which signifies the presence of powder in the plasma. It was also observed that with the increase of applied power, the coalescence phase gets shifted towards the lower Ar dilution percentage. Conversely, the phase transition region from amorphous (a-Si:H) to microcrystalline (μc-Si:H) thin film will observe at the onset of powder formation thus on account of plasma results, deposition of silicon thin films was carried out, and the film properties are in good agreement with plasma characteristics.
Generation and cessation of oscillations: Interplay of excitability and dispersal in a class of ecosystems
Authors: Arumugam Ramesh , Banerjee Tanmoy , Dutta Partha Sharathi
Published: December 2016

We investigate the complex spatiotemporal dynamics of an ecological network with species dispersal mediated via a mean-field coupling. The local dynamics of the network are governed by the Truscott–Brindley model, which is an important ecological model showing excitability. Our results focus on the interplay of excitability and dispersal by always considering that the individual nodes are in their (excitable) steady states. In contrast to the previous studies, we not only observe the dispersal induced generation of oscillation but also report two distinct mechanisms of cessation of oscillations, namely, amplitude and oscillation death. We show that the dispersal between the nodes influences the intrinsic dynamics of the system resulting in multiple oscillatory dynamics such as period-1 and period-2 limit cycles. We also show the existence of multi-cluster states, which has much relevance and importance in ecology.
Multipactor threshold sensitivity to total electron emission yield in small gap waveguide structure and TEEY models accuracy
Authors: Fil N. , Belhaj M. , Hillairet J. , Puech J.
Published: December 2016

Radio-frequency (RF) systems used in vacuum can be damaged by electronic avalanches triggered by the multipactor effect. This undesirable phenomenon can appear for RF components used in space communication payloads as well as in experimental fusion devices, among others. To determine the multipactor breakdown threshold, expensive multipactor experimental tests can be made or multipactor simulations can be performed. This second method uses the Total Electron Emission Yield (TEEY) curve as input and the breakdown threshold predicted by simulation highly depends on this curve. Consequently we decided to make a sensitivity study of multipactor breakdown threshold in relation to the TEEY curve variations. We study the silver conductor material with a RF waveguide transformer. Two critical energy regions are found for a small gap waveguide structure: energies around first cross-over energy and energies between the first cross-over and the yield maximum. Electron emission data have to be accurate on these regions to get a coherent multipactor threshold. Six TEEY models are benchmarked with respect to their capability to accurately model these regions.
Coaxial air flow device for the production of millimeter-sized spherical hydrogel particles
Authors: Workamp Marcel , Alaie Sepideh , Dijksman Joshua A.
Published: December 2016

We describe a method to produce millimeter-sized hydrogel particles, by dispersing aqueous droplets in an oil using a nozzle and subsequently solidifying them. We show that we can vary the size of the particles using an air flow along the nozzle. The resulting particle size can be well predicted by a simple model where a drag force generated by the air flow, adds to the weight pulling the droplet from the nozzle. Particles produced using this method have diameters ranging from 0.7 to 2.3 mm. Production rates up to 0.5 ml/min per nozzle have been achieved, which compares favorably to standard microfluidic techniques. Finally, we show that the method can be used to produce both physical and chemical gel particles and is thus highly universal.
Strong 1.54 μm cathodoluminescence from core-shell structures of silicon nanoparticles and erbium
Authors: Hoang Tuan , Elhalawany Noha , Enders Brian , Bahceci Ersin , Abuhassan Laila , Nayfeh Munir H.
Published: December 2016

We report on the development of efficient infrared-active core-shell Er2O3-Si nanoparticle architecture. Sub 3-nm H-terminated Si nanoparticles are used to reduce/deposit Er3+ ions on the nanoparticles, which in an aqueous environment simultaneously oxidize to produce the core-shells. Our results show strong cathodoluminance at 1543 nm while being able to resolve the Stark splitting. The strong luminescence afforded by the core-shell architecture in which the Si-Er interspacing drops appreciably supports a sensitive interspacing-dependent dipole-dipole energy transfer interaction model, while the hydrogenated silicon-core allows increased loading and reduced segregation of Er as in amorphous silicon material. The room temperature-wet procedure, with pre-prepared and -sorted Si nanostructures affords promising applications in electronic and optical technologies.
The impact of resource dependence of the mechanisms of life on the spatial population dynamics of an in silico microbial community
Authors: Daly Aisling J. , Baetens Jan M. , De Baets Bernard
Published: December 2016

Biodiversity has a critical impact on ecosystem functionality and stability, and thus the current biodiversity crisis has motivated many studies of the mechanisms that sustain biodiversity, a notable example being non-transitive or cyclic competition. We therefore extend existing microscopic models of communities with cyclic competition by incorporating resource dependence in demographic processes, characteristics of natural systems often oversimplified or overlooked by modellers. The spatially explicit nature of our individual-based model of three interacting species results in the formation of stable spatial structures, which have significant effects on community functioning, in agreement with experimental observations of pattern formation in microbial communities.
Accurate B-spline-based 3-D interpolation scheme for digital volume correlation
Authors: Ren Maodong , Liang Jin , Wei Bin
Published: December 2016

An accurate and efficient 3-D interpolation scheme, based on sampling theorem and Fourier transform technique, is proposed to reduce the sub-voxel matching error caused by intensity interpolation bias in digital volume correlation. First, the influence factors of the interpolation bias are investigated theoretically using the transfer function of an interpolation filter (henceforth filter) in the Fourier domain. A law that the positional error of a filter can be expressed as a function of fractional position and wave number is found. Then, considering the above factors, an optimized B-spline-based recursive filter, combining B-spline transforms and least squares optimization method, is designed to virtually eliminate the interpolation bias in the process of sub-voxel matching. Besides, given each volumetric image containing different wave number ranges, a Gaussian weighting function is constructed to emphasize or suppress certain of wave number ranges based on the Fourier spectrum analysis. Finally, a novel software is developed and series of validation experiments were carried out to verify the proposed scheme. Experimental results show that the proposed scheme can reduce the interpolation bias to an acceptable level.
Ignition and monitoring technique for plasma processing of multicell superconducting radio-frequency cavities
Authors: Doleans Marc
Published: December 2016

An in-situ plasma processing technique has been developed at the Spallation Neutron Source (SNS) to improve the performance of the superconducting radio-frequency (SRF) cavities in operation. The technique uses a low-density reactive neon-oxygen plasma at room-temperature to improve the surface work function, to help remove adsorbed gases on the RF surface, and to reduce its secondary emission yield. SNS SRF cavities have six accelerating cells and the plasma typically ignites in the cell where the electric field is the highest. This article details the technique to ignite and monitor the plasma in each cell of the SNS cavities.
Nanoscale deformations in graphene by laser annealing
Authors: Coleman Christopher , Erasmus Rudolph , Bhattacharyya Somnath
Published: December 2016

We investigate a method of inducing nano to micron scale strained regions in graphene using a laser treatment monitored by Raman spectroscopy. The Raman G-peak of the strained region shows a splitting and redshift for graphene exposed to a laser power density above a certain threshold limit (20 mW). We also note blue-shifting of the positions of both Raman D and 2D-peaks and the decrease of both their intensities relative to the G-peak with increasing laser power. These features correspond to p-type doping effects that are believed to be caused by gas adsorbates released from the substrate during the laser treatment. The induced strain is verified by AFM analysis, which shows the blister-like deformations of the treated area and the corresponding strength of the induced gauge fields in the deformed region. We find that, depending on the exact size and geometry of the blisters, the gauge fields can range between 0.4 mT and 300 T. This laser treatment procedure establishes an effective method for the local deformation and doping of graphene, which may be useful for strain engineering in device fabrication.
A family of new explicit, revertible, volume-preserving numerical schemes for the system of Lorentz force
Authors: Tu Xiongbiao , Zhu Beibei , Tang Yifa , Qin Hong , Liu Jian , Zhang Ruili
Published: December 2016

The Lorentz system underlies the fundamental rules for the motion of charged particle in electromagnetic field, which is proved volume-preserving. In this paper, we construct a family of new revertible numerical schemes for general autonomous systems, which in particular, are explicit and volume-preserving for Lorentz systems. These new schemes can prevent the extra numerical errors caused by mismatched initial half-step values in the Boris-like algorithm. Numerical experiments demonstrate the superiorities of our second-order methods in long-term simulations and energy preservation over the Boris algorithm and a higher order Runge-Kutta method (RK3). We also apply these new methods to the guiding center system and find that they behave much better than RK3.
β-relaxation related bright bands in thin film metallic glasses: Localized percolation of flow units captured via transmission electron microscope
Authors: Chen Z. Q. , Huang P. , Xu K. W. , Wang F. , Lu T. J.
Published: December 2016

We report that β-relaxation of amorphous NiW alloy film was effectively enhanced by adding two thin crystalline layers into the amorphous layer. Correspondingly, more bright bands, i.e., nano shear bands, were captured in the amorphous layer, which experienced more pronounced β-relaxations. Based on the potential energy landscape theory, the bright band was proposed to be the localized percolation of flow units corresponding to β-relaxation. Our findings may help connecting experimentally β-relaxation with flow units and shed light on the microstructure origin of β-relaxation.
Surface microcavities at nanoscale depths produced by ultrafast laser pulses
Authors: Romashevskiy S. A. , Ashitkov S. I. , Agranat M. B.
Published: December 2016

The evolution of silicon surface (111) induced by a single femtosecond laser pulse (350 fs, 1028 nm) at near-threshold fluences in viscous liquid is investigated by SEM and AFM. Depending on the deposited energy, the near-surface layers undergo several transformations that generally resulted in controlled formation of simple and complex bowl-shaped surface microcavities at nanoscale depths, surrounded by characteristic rims. At fluences below the ablation threshold, a 2-nm-depth microcavity is observed. The embedded microcavity has the form of an ultra-smooth paraboloid with a roughness ∼0.1 nm rms. Its formation is associated with a flow of melt from the center to the edges due to surface tension variations induced by a single Gaussian-shaped femtosecond laser pulse above the melting threshold. Similar microcavities with depths up to 4 nm are also observed with an increasing fluence. However, at higher fluences complex microcavities, characterized by a central sub-nanostructured region (with a roughness ∼0.5 nm rms) encircled with a crown-like rim of ∼5 nm height and ∼50 nm width (at FWHM), are found. The carried out experiments clearly demonstrate the surrounding medium to play a crucial role in producing of smooth and nanostructured surface microcavities at nanoscale depths with single femtosecond laser pulses.
Amorphous ZnOxNy thin films with high electron Hall mobility exceeding 200 cm2 V−1 s−1
Authors: Yamazaki Takanori , Shigematsu Kei , Hirose Yasushi , Nakao Shoichiro , Harayama Isao , Sekiba Daiichiro , Hasegawa Tetsuya
Published: December 2016

Zinc oxynitride (ZnOxNy) has attracted much attention as an amorphous semiconductor with high electron mobility. Recent studies reported that ZnOxNy thin films grown by sputtering contained nanocrystals, which might reduce their electron mobility through grain boundary scattering. In this study, we fabricated amorphous ZnOxNy thin films on a glass substrate by a less-energetic nitrogen-plasma-assisted pulsed laser deposition (PLD) to suppress the formation of the nanocrystals. Grown by PLD under optimized conditions, these ZnOxNy thin films exhibited extremely flat surfaces with a root-mean-squared roughness (Rrms) of less than 0.3 nm. The Hall mobility of these films exceeded 200 cm2 V−1 s−1 at a critical carrier concentration of ∼1 × 1019 cm−3, which was twice as high as the reported values for sputter-deposited films. Meanwhile, the mobility of films with larger Rrms was limited to ∼160 cm2 V−1 s−1 even at the critical carrier concentration and comparable with that of the sputter-deposited ZnOxNy films. The substantial enhancement in mobility in extremely flat ZnOxNy films demonstrated that suppressing the formation of nanocrystals is the key to fabricating amorphous ZnOxNy thin films with very high mobility.
Collective Thomson scattering system for determination of ion properties in a high flux plasma beam
Authors: van der Meiden H. J. , Vernimmen J. W. M. , Bystrov K. , Jesko K. , Kantor M. Y. , De Temmerman G. , Morgan T. W.
Published: December 2016

A collective Thomson scattering system has been developed for measuring ion temperature, plasma velocity and impurity concentration in the high density magnetized Magnum-PSI plasma beam, allowing for measurements at low temperature (<5 eV) and high electron density >4 × 1020 m−3, while avoiding laser plasma heating caused by inverse Bremsstrahlung. The collective Thomson scattering system is based on the fundamental mode of a seeded Nd:YAG laser and equipped with an LIVAR M506 camera (EBABS technology). The first collective Thomson scattering measurements are taken at the linear plasma generator Pilot-PSI, 40 mm downstream of the cascaded arc source. At this location, the ion temperature is about equal to the electron temperature in the bulk of the plasma beam.