bluuebunny/crossref_metadata_2025 huggingface dataset:
A new microsporidium Berwaldia singularis gen. et sp.nov. from Daphnia pulex and a survey of microsporidia described from Cladocera
Authors: Larsson Ronny
Published: November 2011

A new microsporidian parasite of a freshwater cladoceran from southern Sweden is described using light and electron microscopical methods. Development comprises 2 merogonial sequences, the first resulting in a cluster of 8 merozoites, the second in a chain of 4 merozoites. Each secondary merozoite develops into a sporont which divides into 2 sporoblasts, each of which develops into a spore. The spores are broadly oval and in fresh smears measure about 6 μm in length, with a single nucleus and a posterosome. The polar filament is about 40 μm long, of even thickness throughout, and appears as 15—18 coils in a single layer. The anchoring disc is small and the polaroplast is composed of 2 lamellar parts. Outside the plasma membrane of the sporont a 5-layered, electron-dense substance is produced, which further differentiates into endo- and exospore, an electron-dense substance occurring patchily on the exospore and a pansporoblast membrane. During development the sporoblasts and the young spores are connected by a dense substance. Mature spores appear single or paired. The pansporoblast membrane is composed of 2 structurally different layers, namely a thin outer, single membrane and an inner layer composed of tubular structures. It is connected to the spore coat by patches of the dense substance. The new microsporidium is considered to belong to a new genus of the family Telomyxidae, and its systematic relationship with this and the related family Tuzetiidae is discussed. A survey of microsporidia from Cladocera is included.
Scaling rate for semi-dispersing billiards with non-compact cusps
Authors: ARBIETO A. , MARKARIAN R. , PACIFICO M. J. , SOARES R.
Published: November 2011

We show that certain billiard tables with non-compact cusps are mixing with respect to the invariant infinite measure, in the sense of Krengel and Sucheston. Moreover, we show that the scaling rate is slower than a certain polynomial rate.
An investigation of English pronunciation teaching in Ireland
Authors: Murphy Deirdre
Published: November 2011

The global expansion of the use of English throughout the last decade has had significant implications for its instruction around the world. Among the issues that have arisen as a result of this expansion has been the selection of appropriate phonological models in the English language classroom. Specifically this particular issue has hinged on the question of whether it is more appropriate to encourage English language learners to strive towards the goal of a particular native variety of English pronunciation, or to promote an alternative target. This question has provoked much discussion, and has been the subject of occasionally heated debate (e.g. Jenkins, 1998, 2000; Scheuer, 2005, 2008; Seidlhofer & Jenkins, 2003).
The Shetland Islands: globalisation and the changing status of Standard English
Authors: Sundkvist Peter
Published: November 2011

This article serves as a commentary on the current position of ‘Standard English’ in the Shetland Islands, the northernmost part of the British Isles. Experience gained during linguistic fieldwork over a ten-year period suggests that there is a need to re-examine this issue, not least in view of societal changes. It will be argued that Shetland is by now a locality of relevance for those with an interest in standards of English, as well as Scots, and suggestions will also be made regarding potential future directions for research into Shetland English.
The ‘Outer Circle’ as a role model for the ‘Expanding Circle’
Authors: Rajagopalan Kanavillil
Published: November 2011

The post-World War II emergence of the linguistic phenomenon called ‘World English’ has given rise to seemingly endless discussion and much speculation among scholars and the lay public alike. The topics of discussion range from horrified exclamations at the mysterious apparition (like Horatio's ‘Look my Lord it comes! It beckons you to go with it, as if it some impartment did desire’, in Shakespeare's Hamlet), to what exactly we should call it or how at all should we otherwise identify it or make it identify itself (as in ‘Stay, speak, speak, I charge thee speak!’) and, finally to an attitude of familiarity breeding – for a change – conviviality and comfort (as in the somewhat resigned ‘Custom hath made it in him a property of easiness’).
Credibility Engineering in the Food Industry: Linking Science, Regulation, and Marketing in a Corporate Context
Authors: Penders Bart , Nelis Annemiek P.
Published: November 2011

Argument

We expand upon the notion of the “credibility cycle” through a study of credibility engineering by the food industry. Research and development (R&D) as well as marketing contribute to the credibility of the food company Unilever and its claims. Innovation encompasses the development, marketing, and sales of products. These are directed towards three distinct audiences: scientific peers, regulators, and consumers. R&D uses scientific articles to create credit for itself amongst peers and regulators. These articles are used to support health claims on products. However, R&D, regulation, and marketing are not separate realms. A single strategy of credibility engineering connects health claims to a specific public through linking that public to a health issue and a food product.
What Does the Arrest and Release of Emile Borel and His Colleagues in 1941 Tell Us about the German Occupation of France?
Authors: Mazliak Laurent , Shafer Glenn
Published: November 2011

Argument

The Germans occupying Paris arrested Emile Borel and three other members of the Académie des Sciences in October 1941 and released them about five weeks later. Drawing on German and French archives and other sources, we argue that these events illustrate the complexity of the motivations and tactics of the occupiers and the occupied. While Borel and his colleagues were genuine members of the Resistance, and those who arrested them were full participants in a brutal occupation, both sides respected a bargain, of no small importance to the Vichy regime, that allowed the university to pursue its work if its members avoided overt acts of opposition.
Entwicklung und Bedeutung von Mengen-Zahlen-Kompetenzen und eines basalen Konventions- und Regelwissens in den Klassen 5 bis 9
Authors: Ennemoser Marco , Krajewski Kristin , Schmidt Sabrina
Published: November 2011

Zusammenfassung. In der vorliegenden Studie sollte gezeigt werden, dass theoretische Annahmen zur Entwicklung und Bedeutung grundlegender Mengen-Zahlen-Kompetenzen keinesfalls nur im Kindergarten- und Grundschulalter Gültigkeit besitzen, sondern dass diese unmittelbar auf die Sekundarstufe übertragbar sind. Darüber hinaus sollte mit dem mathematischen Konventions- und Regelwissen eine weitere potenziell bedeutsame und ebenfalls sehr basale Fertigkeitskomponente eingeführt werden, die in der verfügbaren Literatur bisher nicht als eigenständiger Kompetenzbereich diskutiert wird. Die theoretische Begründung für die Relevanz der einbezogenen Basiskompetenzen wird aus einer entwicklungs- und kognitionspsychologischen Perspektive abgeleitet, die sich deutlich von aktuellen Kompetenzerwerbsmodellen für den Sekundarstufenbereich unterscheidet und diese sinnvoll ergänzt. Die auf einer Stichprobe von 1782 Schülern basierenden Ergebnisse bestätigen, dass sich beide Basiskompetenzbereiche von Klasse 5 bis 9 substanziell weiterentwickeln. Obwohl es sich um sehr basale Facetten mathematischer Kompetenz handelt, konnten unter Einbezug der beiden Variablen 67% der Varianz in den Mathematikleistungen der 9. Klasse aufgeklärt werden.
Der Nutzen der erweiterten Theorie des geplanten Verhaltens zur Vorhersageder Vereinssportaktivitätvon Jugendlichen
Authors: Hoffmann Antje
Published: November 2011

Zusammenfassung. In der vorliegenden Untersuchung wurde die Vorhersage der Aufrechterhaltung der vereinsorganisierten Sportaktivität Jugendlicher untersucht. Die Grundlage für das Untersuchungsmodell bildet die Theorie des geplanten Verhaltens, welche um Sport Commitment und soziale Unterstützung erweitert wurde. In einer internet-basierten Befragung wurden 1127 Jugendliche untersucht. Die Ergebnisse der Studie bestätigen größtenteils die Modellannahmen. Wichtigste Einflussfaktoren der Intention sind die Einstellung sowie die wahrgenommene Verhaltenskontrolle. Sportfreude und Verhaltensmöglichkeiten sind bedeutende Prädiktoren des Commitment. Durch das Untersuchungsmodell wird eine zufrieden stellende Varianzaufklärung der Aufrechterhaltung der Vereinssportaktivität erreicht. Die Ergebnisse werden in den aktuellen Forschungsstand eingeordnet und mögliche Schlussfolgerungen für zukünftige Untersuchungen der Aufrechterhaltung sportlicher Aktivität diskutiert.
Macrophage migration inhibitory factor deficiency protects pancreatic islets from palmitic acid‐induced apoptosis
Authors: Saksida Tamara , Stosic‐Grujicic Stanislava , Timotijevic Gordana , Sandler Stellan , Stojanovic Ivana
Published: November 2011

As a result of chronic exposure to high levels of free fatty acids, glucose and inflammatory mediators β‐cell apoptosis occurs at the end stage of obesity‐associated type 2 diabetes (T2D). One potentially deleterious molecule for β‐cell function associated with T2D and obesity in humans is macrophage migration inhibitory factor (MIF). Therefore, the aim of this study was to explore MIF expressionin vivoduring development of obesity and insulin resistance in high‐fat diet (HFD)‐fed C57BL/6 mice and whether MIF inhibition could affect β‐cell apoptosis and dysfunction induced by palmitic acid (PA)in vitro. Indeed, increase in systemic and locally produced MIF correlated well with the weight gain, triglyceride upregulation, glucose intolerance and insulin resistance, which developed in HFD‐fed mice. Inin vitrosettings PA dose‐dependently induced MIF secretion before apoptosis development in islets. Further,mifgene deletion, mRNA silencing or protein inhibition rescued β‐cells from PA‐induced apoptosis as measured by MTT assay and histone‐DNA enzyme linked immuno sorbent assay. Protection from induced apoptosis was mediated by altered activation of caspase pathway and correlated with changes in the level of Bcl‐2 family members. Further, MIF inhibition conveyed a significant resistance to PA‐induced downregulation of insulin and PDX‐1 expression and ATP content. However, β‐cell function was not entirely preserved in the absence of MIF judging by low glucose oxidation and depolarized mitochondrial membrane. In conclusion, the observed considerable preservation of β‐cells from nutrient‐induced apoptosis might implicate MIF as a potential therapeutic target in the later stage of obesity‐associated T2D.
In silico design of novel leads for inhibition of human beta-2-microglobulin
Authors: Navya Pallapotu , Pradhan Dibyabhaba , Umamaheswari Amineni
Published: November 2011

Human myotrophin is the smallest ankyrin repeat protein implicated as a factor to induce cardiac hypertrophy. Activation of myotrophin was observed during acute myocardial infarction (MI). In acute coronary syndrome (ACS) patients, myotrophin acts as a self-governing predictor of major adverse cardiac events (MACE). Therefore, human myotrophin serves as an effective drug target for discovery of new potential drugs. Recent human myotropin inhibitors have poor pharmacological properties leading to intolerable side effects. Hence, ligand based virtual screening protocol of CADD method was pursued in the present study to propose new class potential myotrophin inhibitors. Docking was done by using Schrödinger software suite 2010 (maestro v9.1), docked complexes were validated and enumerated to find out the best lead, the top twenty docked complexes were selected and analyzed through LIGPLOT for their binding orientations. Finally, the ten top ranked leads were reported based on the XPGscore, better binding affinity and good pharmacological properties compared to existing inhibitors. Lead ‘1’ (Mitoxantrone) showed lowest XPGscore (-8.4k cal/mol) and good van der Waal interaction, hydrophobic interactions with the residues Lys-24, Glu-26, Tyr-21, Arg-30, Cys-2, Asp-3, Lys-4, Phe-6, Glu-5, Ala-9, Glu-70 and Gly-140 responsible for the preference of inhibition. Three hydrogen bonds were observed for myotrophin- lead1 docking complex with residues Asp-3, Cys-2 and Gly-5. Thus, lead1 would be the preferred compound to proceed with in vitro and in vivo verification. Our results illustrate a well-designed virtual screening campaign successfully identifying novel lead compounds as potential entry points for the development of drugs for cardiovascular disease treatment.
Absence of historical temporal trends in monthly, seasonal, and annual streamflows for the Okanagan and Similkameen Rivers in south-central British Columbia, Canada
Authors: Rayne Sierra , Forest Kaya
Published: November 2011

Potential historical temporal trends in monthly, seasonal, and annual mean, minimum, and maximum streamflows and date of the spring freshet runoff peak were investigated for the Okanagan and Similkameen Rivers in south-central British Columbia, Canada. There appears to be no compelling evidence that streamflow patterns in the Okanagan and Similkameen Rivers have changed over the available hydrometric record, nor does there appear to be evidence that future changes in streamflow patterns are imminent or likely.
Polyamine Drug Discovery: Synthetic Approaches to Therapeutic Modulators of Polyamine Metabolism
Authors: Woster Patrick M.
Published: November 2011

Numerous synthetic compounds have been described that either act as inhibitors of enzymes involved in polyamine metabolism or otherwise modulate these pathways. Development of agents that affect polyamine metabolism began with an attempt to identify specific inhibitors for the enzymes in the forward polyamine biosynthetic pathway, including ornithine decarboxylase, S-adenosylmethionine decarboxylase and the aminopropyltransferases spermidine synthase and spermine synthase. However, advances in our knowledge of polyamine metabolism have changed the focus of drug discovery in the polyamine area from an enzyme-inhibition strategy to a systematic search for polyamine analogs that exert antitumor effects through a variety of mechanisms, including the induction of apoptosis, inhibition of polyamine catabolism or epigenetic effects on gene expression. The purpose of this chapter is to describe syntheses that have been useful in the discovery of agents that disrupt polyamine metabolism, and relegating a description of the detailed biological effects of these agents to the following chapters. In this section, the syntheses of nucleosides, guanylhydrazones, alkylpolyamines, polyaminoguanidines, polyaminobiguanides, polyaminohydroxamates and polyaminobenzamides that have significant effects on polyamine metabolism are described.
Contemporary Computer-Assisted Approaches to Molecular Structure Elucidation
Authors: Elyashberg Mikhail E , Williams Antony , Blinov Kirill
Published: November 2011

Computer-Assisted Structure Elucidation (CASE) systems are a combination of software algorithms and tools to support and enable chemists and spectroscopists engaged in the process of molecular structure elucidation via the analysis of spectroscopic data. These expert systems dramatically reduce the time associated with structure elucidation and improve the reliability of the results. Contemporary Computer-Assisted Approaches to Molecular Structure Elucidation describes the principles on which these expert systems for spectroscopic structure elucidation are based and concisely explains the algorithmic concepts behind the programs. The authors use their own personal experiences in the development of the Structure Elucidator (StrucEluc) CASE software system to discuss the present state-of-the-art in computer-assisted structure elucidation. Scientists that are presently using CASE systems will be interested in the algorithms and modern approaches and for organizations that are currently using the StrucEluc platform the book is designed to help researchers understand the strategies behind CASE as well as details regarding the StrucEluc platform. For scientists that have never used CASE systems they will now have access to all necessary information to understand CASE systems for mastering this new and very effective approach to structure elucidation. The authors overall goal is writing this book is to produce the 'must read' definitive text that will represent the results of decades of work to develop computer-assisted structure elucidation software systems. CASE systems are now powerful software tools commonly outperforming and correcting human interpretations of data. This book will also provide an historical perspective of the work of the founding fathers of the technique and identify the challenges that have been overcome to produce modern CASE systems.
Synthesis of fullerene-containing poly(ethylene oxide)-block-polystyrene as model shape amphiphiles with variable composition, diverse architecture, and high fullerene functionality
Authors: Dong Xue-Hui , Zhang Wen-Bin , Li Yiwen , Huang Mingjun , Zhang Shuo , Quirk Roderic P. , Cheng Stephen Z. D.
Published: November 2011

Click chemistry provides a precise and effective approach towards construction of fullerene-containing block polymers with diverse architecture, and high fullerene functionality.
The p101 subunit of PI3Kγ restores activation by Gβ mutants deficient in stimulating p110γ
Authors: Shymanets Aliaksei , Ahmadian Mohammad R. , Kössmeier Katja T. , Wetzker Reinhard , Harteneck Christian , Nürnberg Bernd
Published: November 2011

G-protein-regulated PI3Kγ (phosphoinositide 3-kinase γ) plays a crucial role in inflammatory and allergic processes. PI3Kγ, a dimeric protein formed by the non-catalytic p101 and catalytic p110γ subunits, is stimulated by receptor-released Gβγ complexes. We have demonstrated previously that Gβγ stimulates both monomeric p110γ and dimeric p110γ/p101 lipid kinase activity in vitro. In order to identify the Gβ residues responsible for the Gβγ–PI3Kγ interaction, we examined Gβ1 mutants for their ability to stimulate lipid and protein kinase activities and to recruit PI3Kγ to lipid vesicles. Our findings revealed different interaction profiles of Gβ residues interacting with p110γ or p110γ/p101. Moreover, p101 was able to rescue the stimulatory activity of Gβ1 mutants incapable of modulating monomeric p110γ. In addition to the known adaptor function of p101, in the present paper we show a novel regulatory role of p101 in the activation of PI3Kγ.
Unexpected hadrons show up at CERN
Authors: Lubkin Gloria B.
Published: November 2011

High-energy physicists are intrigued by some new results produced at the CERN Intersecting Storage Rings. At the New York American Physical Society meeting on 1 February, Luigi di Leila reported on experiments that showed an unexpectedly large amount of hadron production at high transverse momentum. The experiments were done by a CERN–Columbia–Rockefeller collaboration.
Is physics too ingrown?
Authors: Morse Philip M.
Published: November 2011

The state of physics—or of physicists—has deteriorated in the past several years. Support for physics has not increased, as it had been doing in the previous decades. Indeed, in some important areas it has decreased. Such a sudden change in rate of growth is ominous in itself to heads of projects and to physicists in more or less permanent positions. To our younger colleagues, who have not yet found a permanent job or who have not yet completed their graduate work, it has been catastrophic. How can we improve the situation?
Heavy ions–looking ahead
Authors: Hamilton Joseph H. , Sellin Ivan A.
Published: November 2011

Interest and excitement in many areas of physics and chemistry are growing as the research opportunities that would be offered by a universal heavy-ion accelerator begin to be appreciated. Advances made possible with existing beams—of carbon, oxygen, sulfur and argon—have stimulated the imagination of scientists who contemplate what would be possible with an accelerator allowing nuclear reactions all the way up to U238 on U238 to be studied.
Viscosity study suggests superfluidity
Authors: Lubkin Gloria B.
Published: November 2011

A group at Helsinki University of Technology headed by Olli Lounasmaa says that it has strong evidence for superfluidity in liquid He based on a viscosity measurement. The result is the latest link in a chain of experiments delineating the strange behavior of He.
No gravity-wave confirmation by the new experiments
Authors: Lubkin Gloria B.
Published: November 2011

Two new experiments have failed to detect gravity waves of the intensity originally reported by Joseph Weber in 1969–70. Richard L. Garwin and James L. Levine of IBM Research Center, operating a Weber-type antenna at 1695 Hz, report no signals after 18 days of serious data collection. At Bell Labs, J. Anthony Tyson, who has a Weber-type antenna sensitive to 710 Hz, found no signals after three months of operation in the present set-up.
Argonne ZGS yields polarized proton beam
Authors: Saar Robert A.
Published: November 2011

A collaboration of physicists and engineers at the Argonne National Laboratory has produced polarized proton beams of 6 GeV, the first polarized beam to be achieved in a synchrotron, says Alan Krisch (University of Michigan). The beam, with a polarization of (62±15)% was achieved by using a polarized proton source in conjunction with the Zero Gradient Synchrotron (ZGS).
Energy crises in perspective
Authors: Fisher John C.
Published: November 2011

How real and long lasting is the current energy crisis? There is reason to believe that domestic fossil fuels will continue to be available, at slowly declining prices (in constant dollars), in adequate amounts to support total anticipated energy consumption of the US and the world for many centuries. There is also every reason to believe that domestic nuclear fuels will continue to be available, at slowly declining prices (in constant dollars), in adequate amounts to support total anticipated energy consumption for many millenia. If nuclear fuels or other energy sources take an increased proportion of the load, the fossil fuels will last correspondingly longer. Thus, the current energy crisis, although very real, should be viewed as a transient perturbation of the long-term trajectory of our energy economy.
LEED data successfully analyzed
Authors: Rothenberg Marian S.
Published: November 2011

Hope for determining crystal surface structure through electron diffraction has been held out since Clinton Davisson and Lester Germer first saw coherent scattering of electrons in 1927. In an analogue to x-ray studies of bulk crystal structure, low-energy electrons (10–500 eV), which undergo strong elastic scattering and penetrate only a few atomic layers, should locate surface atoms. But the strong atomic scattering (cross section about 108 times those for x rays) leads not only to great surface sensitivity but also to several collisions per electron. The computational complexity of treating this multiple scattering was largely responsible for delaying the development of a working theory for over 40 years.
Muon–proton data at 150 GeV apparently violate scaling
Authors: Lubkin Gloria B.
Published: November 2011

A possible violation of Bjorken scaling, which had worked extremely well for electron–proton scattering in the 10–20-GeV range, has been reported for a muon–proton scattering experiment at the National Accelerator Laboratory, for 150-GeV muons. In an invited paper at the APS Chicago meeting in February, K. Wendell Chen (Michigan State University) stressed that the results are still extremely preliminary. The principal investigators are Chen, Louis Hand (Cornell University) and Wayne Vernon (University of California at San Diego).
A first look at the 1973 Register
Authors: Porter Beverly F. , Barisch Sylvia F. , Sears Raymond W.
Published: November 2011

The early 1970's have been important years of change for the physics and astronomy community. Data from the 1973 APS–AIP Register of Physicists and Related Scientists are now being analyzed and will allow us to catch a glimpse of these changes. Our initial analysis of the information reveals that unemployment, which had been dramatically increasing into 1971, has since dropped considerably although not to levels of the mid-1960's. Despite the tight employment market, salaries have continued to increase with the largest increases noted for physicists employed by the government.
APS and OSA meet in Washington
Authors: Golden James
Published: November 2011

For the first time in over thirty years the Optical Society of America and the American Physical Society will meet together in Washington this month (21–25 April). The unusual nature of the meeting is reflected in a varied array of sessions and activities—among them, the celebration of the 75th Anniversary of the APS, special tutorial/review seminars in optics, the first Physics/Optics Show, a tour of the National Bureau of Standards facilities in Gaithersburg. Maryland, a Skylab Symposium featuring Owen Garriott of the Skylab II crew, and of course large numbers of invited and contributed papers.
Photonuclear reactions in medicine
Authors: McNeill K. G.
Published: November 2011

Medical researchers use radioactivity in two general and important ways. First of all, they require radioactive isotopes as tags or tracers to study complex bodily processes such as the excretion of copper from the human system or the preferential uptake of isotopes by tumors. Secondly, researchers may induce radioactivity in a given biological sample in order to perform a quantitative analysis on it. This technique of activation analysis enables them to measure, for example, the amount of lead in hair and bone or to perform a multielemental analysis of blood.
Unusual behavior in cadmium sulfide
Authors: Levi Barbara G.
Published: November 2011

In his recent measurements of the electrical conductivity of plastically deformed cadmium sulfide, Charles Elbaum of Brown University has found a large anistropy and unusual temperature dependence over a range from 20 to 300 K. The conductivity in the direction of the longest (z) axis of his specimens is from 106 to 108 times that along the other two mutually perpendicular directions. As a function of temperature the conductivity along the z axis first rises to a maximum of about 4.5 (Ω cm)−1 near 125 K, then decreases exponentially. By contrast, the conductivities at right angles decrease monotonically from values of about 10−6 (Ω cm)−1 at 300 K to values of about 10−8 (Ω cm)−1 at 125 K. Elbaum feels that the experimental results imply a metallic-type conduction along a pseudo-one-dimensional system consisting of arrays of dislocations.
How scientists advise the Congress
Authors: Ratchford J. Thomas
Published: November 2011

Science and technology resulting from applications of scientific knowledge require a great deal of legislative attention. Some of the reasons for this are obvious. Readers of PHYSICS TODAY are probably aware of the Atomic Energy Act of 1954, the National Science Foundation Act of 1950 and the National Aeronautical and Space Administration Act of 1958. These laws, currently on the statute books, deal explicitly with science and technology.
Many total cross sections are rising
Authors: Lubkin Gloria B.
Published: November 2011

When experiments last year at the CERN Intersecting Storage Rings showed that the total cross sections for proton–proton collisions were rising about 10% as center-of-mass energies increased from 23 to 53 GeV, there was great excitement and considerable surprise. Now a tripartite team working at the Fermi National Accelerator Laboratory has investigated total cross sections from targets of protons and deuterons where the incident particles were protons, antiprotons, positive and negative kaons and positive and negative pions; incident energies ranged from 50 to 200 GeV in the laboratory system. By comparing the proton and deuteron cross sections, neutron cross sections were deduced.
Physicists I have known
Authors: Ewald Paul P.
Published: November 2011

My first encounter with science came when I was eleven. My mother and I were living in Berlin, but often spent summer vacations with friends in Cambridge, England. In their house we met Siegfried Ruhemann, holder of the first chair in organic chemistry in England, at Cambridge's Gonville and Caius College.
Micro-imaging of transient guest profiles in nanochannels
Authors: Hibbe F. , Marthala V. R. R. , Chmelik C. , Weitkamp J. , Kärger J.
Published: November 2011

Zeolites of type ferrierite are exploited as a host system for monitoring the evolution of guest concentration (methanol) in nanoporous host materials upon adsorption. Additional transport resistances at the crystal surface have been removed so that uptake is exclusively controlled by the diffusion resistance of the pore space. Since the crystal shape deviates from a simple parallelepiped, the primary imaging data do not immediately reflect true local concentrations. A simple algorithm is developed which overcomes this complication. The determined transient concentration profiles ideally comply with the requirements for the application of the Boltzmann-Matano integration method for determining diffusivities. The resulting diffusivities (along the direction of the “10-ring channels”) are found to exceed those along the 8-ring channels by three orders of magnitude.
Li and Ca Co-decorated carbon nitride nanostructures as high-capacity hydrogen storage media
Authors: Wang Yusheng , Ji Yong , Li Meng , Yuan Pengfei , Sun Qiang , Jia Yu
Published: November 2011

Using first-principles method based on density functional theory, we perform a detailed study of the hydrogen storage properties of Li and Ca co-decorated graphene-like carbon nitride (g-CN) nanostructures. The results show that the average adsorption energy of the molecular hydrogen is ∼0.26 eV/H2, which is acceptable for reversible H2 adsorption/desorption near ambient temperature. Moreover, the findings also show that the storage capacity of the Li and Ca co-decorated g-CN can reach up to 9.17 wt %, presenting a good potential as hydrogen storage material. Regarding the H2 adsorption mechanism, it is demonstrated that the Li adatoms become positively charged through charge transferring to g-CN and then bind hydrogen molecules via the polarization mechanism.
Surface rippling on bulk metallic glass under nanosecond pulse laser ablation
Authors: Liu Y. , Jiang M. Q. , Yang G. W. , Guan Y. J. , Dai L. H.
Published: November 2011

We report an interesting surface ripple patterns in the irradiated area of a Zr-based bulk metallic glass by nanosecond pulse laser with single shot. Such surface rippling phenomenon can be ascribed to the Kelvin-Helmholtz instability at the interface between the molten layer and the expanding plasma plume. The analytical instability criterion is obtained via a perturbation analysis. Furthermore, the model demonstrates that the characteristic spacing of the ripples is dominated by the density, transverse velocity of the plasma wind, and the surface tension of the molten layer. The predicted spacing agrees well with the experimentally observed values. The results are fundamentally useful for laser-processing bulk metallic glasses (BMGs) and even for understanding the nature of flow in BMGs.
Utilization of simple scaling laws for modulating tip-sample peak forces in atomic force microscopy characterization in liquid environments
Authors: Solares Santiago D. , Chang Jonathan , Seog Joonil , Kareem Adam U.
Published: November 2011

The dynamics of atomic force microscopy (AFM) microcantilevers in liquid environments have been previously shown to be extremely complex and nonlinear, exhibiting phenomena such as momentary excitation of higher eigenmodes, fluid-borne excitation, mass loading, and the emergence of sub-harmonic responses. It has also been shown that the signals acquired by the instrument can differ significantly between tip- and base-excited cantilevers in highly damped environments, such that it can be difficult for users to modulate the peak impact forces for base-excited AFM systems that are not equipped with advanced force spectroscopy tools. Despite the dynamic complexity, we show that through understanding of simple scaling laws based on the damped harmonic oscillator model and operation at high amplitude setpoints, it is possible to modulate the tip-sample forces, which could be useful in studies that require experiments involving different but controllable peak force levels.
Adatom kinetics on nonpolar InN surfaces: Implications for one-dimensional nanostructures growth
Authors: Aliano A. , Catellani A. , Cicero G.
Published: November 2011

The adatom kinetics processes of adsorption and diffusion for In and N species on nonpolar InN a- and m-planes have been studied using ab initio density functional theory calculations. Our results reveal remarkable in-plane anisotropic potential energy surfaces, consistently with experimental data on vertically c-oriented one-dimensional nanostructure formation; we demonstrate that lateral wall morphology strongly determinates the contribution of diffusion to the growth process.
Growth mechanism and electronic properties of epitaxial In2O3 films on sapphire
Authors: Wang Ch. Y. , Kirste L. , Morales F. M. , Mánuel J. M. , Röhlig C. C. , Köhler K. , Cimalla V. , García R. , Ambacher O.
Published: November 2011

In this work, we report on the epitaxial growth of high-quality cubic indium oxide thick films on c-plane sapphire substrates using a two-step growth process. The epitaxial relationship of In2O3 on (0001) Al2O3 has been investigated. The (222) plane spacing and lattice parameter of a most strain-relaxed high-quality In2O3 film have been determined to be 292.58 pm and 1013.53 pm, respectively. The electronic properties in dependence of the film thickness are interpreted using a three-region model. The density at the surface and interface totals (3.3±1.5)×1013cm-2, while the background electron density in the bulk was determined to be (2.4±0.5)×1018cm-3. Furthermore, post treatments such as irradiation via ultraviolet light and ozone oxidation have been found to influence only the surface layer, while the bulk electronic properties remain unchanged.
Wide frequency range magnetoimpedance in tri-layered thin NiFe/Ag/NiFe films: Experiment and numerical calculation
Authors: Corrêa M. A. , Bohn F. , Escobar V. M. , Marques M. S. , Viegas A. D. C. , Schelp L. F. , Sommer R. L.
Published: November 2011

Given that the magnetoinductive effect (MI), skin effect and ferromagnetic resonance influence magnetic permeability behavior at different frequency ranges, the description of the magnetoimpedance effect over a wide range of frequency becomes a difficult task. To that end, we perform an experimental investigation of the magnetoimpedance effect in a tri-layered thin film over a wide frequency range. We compare the experimental results for a tri-layered thin film with numerical calculus performed using an approach that considers a magnetic transverse susceptibility model for planar systems and an appropriate magnetoimpedance model for a tri-layered system together. The results show remarkably good agreement between numerical calculus and experimental measurements. Thus, we discuss the experimental results in terms of different mechanisms that govern the MI changes observed in distinct frequency ranges and provide experimental support to confirm the validity of the theoretical approach.
The stochastisation hypothesis and the spacing of planetary systems
Authors: Cresson Jacky
Published: November 2011

We introduce the stochastisation hypothesis which aims to provide a framework to deal with physical systems in random environment. We apply the stochastisation hypothesis in two different cases: in the study of the dynamics of a protoplanetary nebula and in the chaotic long-term behaviour of a generic planetary system using previous works of Albeverio et al. [“A stochastic model for the orbits of planets and satellites: an interpretation of Titius-Bode law,” Expo. Math. 4, 363–373 (1983)], Nottale [“The quantization of the solar system,” Astron. Astrophys. 315, L9 (1996)], and Laskar [“On the spacing of planetary systems,” Phys. Rev. Lett. 84(15), 3240–3243 (2000)10.1103/PhysRevLett.84.3240]. These results give both a particular law for the distribution of planetary orbits.
A floating platform of concrete for offshore wind turbine
Authors: Hua Jianbo
Published: November 2011

A floating platform concept is introduced in this paper for offshore wind turbine. A vertical cylinder on the top of an elliptical sphere forms the principal configuration of the platform. The analysis of the dynamic performance of an example platform with 5 MW wind turbine by means of the well-established linear theory for the dynamics of marine constructions in waves shows that the platform is able to secure the normal function of the wind turbine in waves up to rough sea state and has the required dynamic performance for survival in extreme waves by adopting a survival ballast condition. An important feature of this concept is that reinforced concrete can be used as cost-efficient construction material so that the service life, several times longer than similar steel constructions can be obtained despite of the marine corrosive and erosive environment. Thus, this kind of platform can become competitive in the economical, sustainable, and environment-friendly aspect.
How nanoscale seed particles affect vapor-liquid nucleation
Authors: Liu Yawei , Men Yumei , Zhang Xianren
Published: November 2011

In this work, we used constrained lattice density functional theory to investigate how nanoscale seed particles affect heterogeneous vapor-liquid nucleation. The effects of the physical properties of nanoscale seed particles, including the seed size, the strength of seed-fluid attraction, and the shape of the seeds, on the structure of critical nuclei and nucleation barrier were systemically investigated.
Time- and angle-resolved x-ray diffraction to probe structural and chemical evolution during Al-Ni intermetallic reactions
Authors: Yoo Choong-Shik , Wei Haoyan , Chen Jing-Yin , Shen Guoyin , Chow Paul , Xiao Yuming
Published: November 2011

We present novel time- and angle-resolved x-ray diffraction (TARXD) capable of probing structural and chemical evolutions during rapidly propagating exothermic intermetallic reactions between Ni-Al multilayers. The system utilizes monochromatic synchrotron x-rays and a two-dimensional (2D) pixel array x-ray detector in combination of a fast-rotating diffraction beam chopper, providing a time (in azimuth) and angle (in distance) resolved x-ray diffraction image continuously recorded at a time resolution of ∼30 μs over a time period of 3 ms. Multiple frames of the TARXD images can also be obtained with time resolutions between 30 and 300 μs over three to several hundreds of milliseconds. The present method is coupled with a high-speed camera and a six-channel optical pyrometer to determine the reaction characteristics including the propagation speed of 7.6 m/s, adiabatic heating rate of 4.0 × 106 K/s, and conductive cooling rate of 4.5 × 104 K/s. These time-dependent structural and temperature data provide evidences for the rapid formation of intermetallic NiAl alloy within 45 μs, thermal expansion coefficient of 1.1 × 10−6 K for NiAl, and crystallization of V and Ag3In in later time.
Analysis of local chemical and structural inhomogeneities in FeySe1−xTex single crystals
Authors: Speller S. C. , Britton T. B. , Hughes G. , Lozano-Perez S. , Boothroyd A. T. , Pomjakushina E. , Conder K. , Grovenor C. R. M.
Published: November 2011

Co-existence of superconductivity and magnetism has been reported in certain regions of the Fe(Se,Te) phase diagram. Here, we address the key question of whether these different properties occur simultaneously within a homogeneous crystal or whether a “two-phase” description is more appropriate. Extensive microstructural analysis suggests that a Te-rich sample exhibiting both bulk superconductivity and magnetic order contains significant chemical and structural inhomogeneity, suggesting that the “two-phase” explanation may be valid in this sample. The high-resolution electron backscatter diffraction (HR-EBSD) technique has been used to map local changes in lattice parameter very precisely in these compounds.
Fractal disperse hydrogen sorption kinetics in spark discharge generated Mg/NbOx and Mg/Pd nanocomposites
Authors: Anastasopol Anca , Pfeiffer Tobias V. , Schmidt-Ott Andreas , Mulder Fokko M. , Eijt Stephan W. H.
Published: November 2011

Isothermal hydrogen desorption of spark discharge generated Mg/NbOx and Mg/Pd metal hydride nanocomposites is consistently described by a kinetic model based on multiple reaction rates, in contrast to the Johnson-Mehl-Avrami-Kolmogorov [M. Avrami, J. Phys. Chem. 9, 177 (1941); W. A. Johnson and R. F. Mehl, Trans. Am. Inst. Min., Metal. Eng. 135, 416 (1939); A. N. Kolmogorov, Izv. Akad. Nauk SSSR, Ser. Mat. 3, 355 (1937); F. Liu, F. Sommer, C. Bos, and E. J. Mittemeijer, Int. Mat. Rev. 52, 193 (2007)] model which is commonly applied to explain the kinetics of metal hydride transformations. The broad range of reaction rates arises from the disperse character of the particle size and the dendritic morphology of the samples. The model is expected to be generally applicable for metal hydrides which show a significant variation in particle sizes, in configuration and/or chemical composition of local surroundings of the reacting nanoparticles.
Ab initio study of acoustic velocities in molybdenum under high pressure and high temperature
Authors: Zeng Zhao-Yi , Hu Cui-E , Liu Xun , Cai Ling-Cang , Jing Fu-Qian
Published: November 2011

Acoustic velocities of Molybdenum (Mo) under high pressure and high temperature are calculated by using the generalized gradient approximation within density functional theory. The break in acoustic velocities of bcc Mo along Hugoniot occurs around 175–275 GPa, which agrees with shock-wave experimental results in which the phase transition was found at 210 GPa, 4100 K [R. S. Hixson, Phys. Rev. Lett. 62, 637 (1989)]. By comparing the acoustic velocities, we confirmed the phase transition from bcc to fcc Mo.
Communication: Regularizing binding energy distributions and thermodynamics of hydration: Theory and application to water modeled with classical and ab initio simulations
Authors: Weber Valéry , Merchant Safir , Asthagiri D.
Published: November 2011

The high-energy tail of the distribution of solute-solvent interaction energies is poorly characterized for condensed systems, but this tail region is of principal interest in determining the excess free energy of the solute. We introduce external fields centered on the solute to modulate the short-range repulsive interaction between the solute and solvent. This regularizes the binding energy distribution and makes it easy to calculate the free energy of the solute with the field. Together with the work done to apply the field in the presence and absence of the solute, we calculate the excess chemical potential of the solute. We present the formal development of this idea and apply it to study liquid water.
Influence of coastal vegetation on the 2004 tsunami wave impact in west Aceh
Authors: Laso Bayas Juan Carlos , Marohn Carsten , Dercon Gerd , Dewi Sonya , Piepho Hans Peter , Joshi Laxman , van Noordwijk Meine , Cadisch Georg
Published: November 2011

In a tsunami event human casualties and infrastructure damage are determined predominantly by seaquake intensity and offshore properties. On land, wave energy is attenuated by gravitation (elevation) and friction (land cover). Tree belts have been promoted as “bioshields” against wave impact. However, given the lack of quantitative evidence of their performance in such extreme events, tree belts have been criticized for creating a false sense of security. This study used 180 transects perpendicular to over 100 km on the west coast of Aceh, Indonesia to analyze the influence of coastal vegetation, particularly cultivated trees, on the impact of the 2004 tsunami. Satellite imagery; land cover maps; land use characteristics; stem diameter, height, and planting density; and a literature review were used to develop a land cover roughness coefficient accounting for the resistance offered by different land uses to the wave advance. Applying a spatial generalized linear mixed model, we found that while distance to coast was the dominant determinant of impact (casualties and infrastructure damage), the existing coastal vegetation in front of settlements also significantly reduced casualties by an average of 5%. In contrast, dense vegetation behind villages endangered human lives and increased structural damage. Debris carried by the backwash may have contributed to these dissimilar effects of land cover. For sustainable and effective coastal risk management, location of settlements is essential, while the protective potential of coastal vegetation, as determined by its spatial arrangement, should be regarded as an important livelihood provider rather than just as a bioshield.
Age dynamics in scientific creativity
Authors: Jones Benjamin F. , Weinberg Bruce A.
Published: November 2011

Data on Nobel Laureates show that the age–creativity relationship varies substantially more over time than across fields. The age dynamics within fields closely mirror field-specific shifts in (
i
) training patterns and (
ii
) the prevalence of theoretical contributions. These dynamics are especially pronounced in physics and coincide with the emergence of quantum mechanics. Taken together, these findings show fundamental shifts in the life cycle of research productivity, inform theories of the age–creativity relationship, and provide observable predictors for the age at which great achievements are made.
Role of donor genital tract HIV-1 diversity in the transmission bottleneck
Authors: Boeras Debrah I. , Hraber Peter T. , Hurlston Mackenzie , Evans-Strickfaden Tammy , Bhattacharya Tanmoy , Giorgi Elena E. , Mulenga Joseph , Karita Etienne , Korber Bette T. , Allen Susan , Hart Clyde E. , Derdeyn Cynthia A. , Hunter Eric
Published: November 2011

The predominant mode of HIV-1 infection is heterosexual transmission, where a genetic bottleneck is imposed on the virus quasispecies. To probe whether limited genetic diversity in the genital tract (GT) of the transmitting partner drives this bottleneck, viral envelope sequences from the blood and genital fluids of eight transmission pairs from Rwanda and Zambia were analyzed. The chronically infected transmitting partner's virus population was heterogeneous with distinct genital subpopulations, and the virus populations within the GT of two of four women sampled longitudinally exhibited evidence of stability over time intervals on the order of weeks to months. Surprisingly, the transmitted founder variant was not derived from the predominant GT subpopulations. Rather, in each case, the transmitting variant was phylogenetically distinct from the sampled locally replicating population. Although the exact distribution of the virus population present in the GT at the time of transmission cannot be unambiguously defined in these human studies, it is unlikely, based on these data, that the transmission bottleneck is driven in every case by limited viral diversity in the donor GT or that HIV transmission is solely a stochastic event.