bluuebunny/crossref_metadata_2025 huggingface dataset:
Lecture demonstrations
Authors: Wissler B. F.
Published: January 2009

The important position of the lecture demonstration in the teaching of physics has long been recognized. The Educational Advisory Committee of the American Institute of Physics suggested that a discussion of the aims and nature of the lecture demonstration could be fruitful, and that such a discussion could suitably be sponsored by the American Association of Physics Teachers. V. E. Eaton was asked to arrange a meeting in 1959 at Wesleyan University to fill this need. As a result of these suggestions, about 35 college physics teachers and others who are keenly interested in the teaching of physics gathered last summer in Middletown, Connecticut, to discuss the subject of “Lecture Demonstrations in Physics”.
Results of preliminary study of national physics roster
Authors: Barisch Sylvia
Published: January 2009

Six years ago, the National Science Foundation enlisted the aid of the American Institute of Physics in compiling data on physicists as part of the continuing National Register of Scientific and Technical Personnel. Since that time, thousands of individual physicists have cooperated with the Institute by providing the information about themselves which has been requested. A voluminous Physics Register now exists which contains reliable data with regard to the educational training, ages, geographical distribution, and employment of physicists throughout the US.
High-energy nuclear physics conference
Authors: Polkinghorne J. C.
Published: January 2009

Russia is no longer a terra incognita from which an occasional traveler returns with strange tales of prodigious toasts in vodka and the palatial magnificence of the Moscow Metro. It is several years too late for the author of this article to be able to indulge in discoursing widely on East and West and he must confine himself to the business in hand. It suffices, therefore, to say that Kiev is a finely laid out city that has made a remarkable recovery from the devastation of war, and to express gratitude to our hosts, the Academy of Sciences of the USSR, for all that they did to make our stay pleasurable and profitable. One thing however they could not provide: a host of new discoveries in the preceding year. In consequence it was rather a bread-and-butter conference, with caviar only in the most literal sense.
Can the scales of atomic weights and nuclidic masses be unified?
Authors: Wichers Edward
Published: January 2009

The current discussion about a unified scale of nuclidic masses and atomic weights * grew out of a desire to correct the indefiniteness of the chemical scale of atomic weights which results from variations in the isotopic composition of natural oxygen. Oxygen, with a defined atomic weight of 16, has been the universally accepted reference element for atomic weights since early in the present century. Earlier many chemists favored a scale based on hydrogen, with a definite atomic weight of unity. The hydrogen scale originated with Dalton and doubtless enjoyed support on the basis of Prout's hypothesis that the hydrogen atom is the structural unit in the atoms of all other elements. However, the operational advantages of oxygen in stoichiometric determinations of atomic weights offset the logical arguments for hydrogen and in time brought about the general acceptance of the oxygen scale. It was natural to assign a whole number, sixteen, to oxygen, rather than the nonintegral number representing its atomic weight on the hydrogen scale. Thus the unit of atomic weight became one-sixteenth the weight of an atom of oxygen.
The 7th International Symposium on Combustion
Authors: Starkman E. S.
Published: January 2009

The Seventh International Symposium on Combustion, the fifth such meeting since World War II and the first one outside of the United States, was held in London and Oxford, England, from August 27 to September 3, 1958. This seventh symposium, organized by The Combustion Institute and by The Institute of Fuels of Great Britain, was attended by 600 scientists and engineers, representing 19 nations.
Midwest Solid-State Physics Conference
Authors: Friauf Robert J.
Published: January 2009

Masers, rasers, growth of whiskers—these were among the things discussed at the 1958 meeting of the Midwest Solid-State Physics Conference, which was held on November 1 at the University of Kansas in Lawrence. Some seventy persons were in attendance, representing institutions in six midwestern states.
Congress will reconsider the draft
Authors: Barton H. A.
Published: January 2009

The careers of trained and budding scientists are apt to be affected by what Congress does before June 30 about the expiring selective service and reserve forces legislation. What it does may also largely determine the future value of the professional services of scientists to the national security.
Accelerator conference
Authors: Ajzenberg-Selove Fay
Published: January 2009

The conference, organized by High Voltage Engineering Corporation (HVEC), had two aspects. One was that described by the subtitle above, and the other, perhaps the more immediately exciting one, was the discussion of the capabilities of a new physics tool of extreme importance, the tandem generator. The conference was held at the Commander Hotel in Cambridge at a time when the air is crisp and the leaves beautifully colored and Cambridge appears as entrancing and exotic as any of the locales of any of the conferences reported in Physics Today. About two hundred and fifty people attended the meeting. The interests of the participants were about evenly divided between basic and applied physics.
Noncrystalline solids
Authors: Krumhansl J. A.
Published: January 2009

Upon receipt of the announcement of this conference, the standard reaction (after the usual quick check on location—choice or otherwise) seems to have been, “what do they mean by that?” This, of course, was also the organizing committee's question—“what is a ‘noncrystalline solid’?”
High-speed rotation
Authors: Beams J. W.
Published: January 2009

Upon this occasion the speaker usually reviews some scientific or technical subject with which he is or has been associated or he discusses current problems involving the role of physics in human affairs. Although the latter subject certainly is most timely and important, I shall address myself to the former. I will attempt to discuss some applications of high-speed rotation to science with special emphasis upon problems of centrifuging. No effort will be made to review adequately the subject or to emphasize the most important work done in the field. Instead I will discuss some of the work that has interested me personally. Unfortunately time is not available to mention properly all of my collaborators and students to whom should go most of the credit for the work.
Hydrodynamics
Authors: White George , Young J.
Published: January 2009

Topics ranging from hydrodynamic stability, turbulence, and magnetohydrodynamics to analytical and numerical approaches in calculating compressible flow problems were presented in invited talks at a conference on hydrodynamics held October 16–18, 1958, at Los Alamos, N. M. Sponsored by the Los Alamos Scientific Laboratory of the University of California, the meeting was attended by forty visiting scientists and as many LASL staff members. All sessions of the meeting were open and unclassified and were held in the auditorium of the Laboratory Administration Building.
Louis Nicot Ridenour, Jr. 1911–1959
Authors: Loomis F. W.
Published: January 2009

On the morning of May 21, 1959, Louis Ridenour was found dead of a cerebral hemorrhage in his hotel room in Washington, D.C. As so often in the past, he had come to Washington as a Scientific Adviser for the Air Force. He had made notes for a talk he was to give that day at a conference in the Pentagon.
Nuclear optical model
Authors: Ford Kenneth W.
Published: January 2009

A. M. Lane, of the Atomic Energy Research Establishment, Harwell, England, opened his remarks to the International Conference on the Nuclear Optical Model by quoting a US Navy man who was arranging Dr. Lane's MATS transportation to the conference. “What”, asked the sailor, “is the Navy doing transporting Limey opticians to the States?”
Fluctuations in solids
Authors: Brophy James J.
Published: January 2009

The major purpose of scientific conferences is to allow scientists to meet, exchange latest results, and discuss mutual problems. Unfortunately, the large attendance at most meetings forces a formal organization that to a large extent reduces these benefits. When the subject matter is sufficiently narrow and attendance is limited to scientists working in the area under discussion, the atmosphere becomes far more conducive to informal discussion and the fruitful exchange of ideas.
Preparation of high-school teachers of science
Authors: Buchta J. W.
Published: January 2009

Typical statements that may be gleaned from a variety of studies and compilations of data on the preparation of high-school teachers are:

“Training in physics ranged from 8 to 55 semester hours with the median at 16. Only 13 (about 25%) had majored in physics.”

“The average number of semester hours in physics taken by the science teachers was 10.”

“One third of the physics teachers had fewer than 10 semester hours in physics.”
Kamerlingh Onnes Conference on Low-Temperature Physics
Authors: Squire Charles F.
Published: January 2009

Fifty years ago H. Kamerlingh Onnes liquefied helium at Leiden University and to commemorate this the Netherlands Physical Society, together with Leiden University and certain Dutch industries, held a conference on low-temperature physics (June 23–28, 1958). There were more than 30 nations represented and over 300 participants, of which 100 were from the USA and three from the USSR. It was quite clear that Kamerlingh Onnes had really started something, for there were some 165 papers ranging over the topics which are unique to very low temperatures. The much coveted scientific award, The Kamerlingh Onnes Medal of the “Nederlandse Vereniging voor Koeltechniek”, was presented to S. C. Collins of the Massachusetts Institute of Technology. He became the third recipient of this honor, the other two being Peter Kapitza and the late Sir Francis Simon
X-ray crystallography: An account of early studies at Schenectady; the genesis and beginnings of x-ray crystallography at Caltech
Authors: Hughes Edward W. , Hull Albert W. , Burdick C. L.
Published: January 2009

The electromagnetic wave nature of x rays was first firmly established in 1912 by the observation of diffraction of x rays by crystals in the famous investigations of Friedrich, Knipping, and von Laue. The application of x-ray diffraction methods to the determination of the detailed structure of crystals was demonstrated within less than a year by W. L. Bragg and since that time literally thousands of papers have appeared describing either improvements in these methods or giving the results of their application to crystals, the natures of which have become increasingly complex as newer methods of increased power have been developed.
Rehovoth Conference on Nuclear Structure
Authors: Lipkin Harry J.
Published: January 2009

From September 8 to 15 an international gathering of physicists took place for the first time in the small new state of Israel. The 220 participants registered at the conference included 155 guests from countries ranging alphabetically from Argentina to Yugoslavia. The choice of the Weizmann Institute of Science in Rehovoth, Israel, as the location of the International Conference on Nuclear Structure was undoubtedly in recognition of Israel as a center of that particular kind of nuclear research which has made the name Racah familiar in laboratories throughout the world. However, in his opening address to the conference, Professor Racah found other links between nuclear structure and the State of Israel. The first Zionist Congress, said Racah, was held at about the same time as the discovery of radioactivity; the Balfour Declaration announcing British Government support for a Jewish National Home in Palestine was promulgated at about the same time as the discovery of artificial radioactivity; and in 1948 the State of Israel was born together with the shell model. To avoid being accused of partisanship with regard to nuclear models, however, he pointed out that one of the distinctive features of Israel were the collective settlements.
Dielectric dispersion of BiFeO3 thin film over a broad frequency range (100 Hz–10 GHz)
Authors: Zhang Xiao-Yu , Song Qing , Xu Feng , Ong C. K.
Published: January 2009

The dielectric properties of single-phase BiFeO3 (BFO) thin films were investigated based on parallel-plate electrode (PPE) and coplanar interdigital electrode (CIE) configurations across a wide frequency range of 100 Hz–10 GHz. The dielectric dispersion in the PPE configuration, caused by the interfacial polarization in film/electrode interfaces, exhibited a strong dependence on frequency. In the CIE configuration, the low dielectric dispersion, high permittivity, and low dielectric loss indicated that interfacial polarization was substantially suppressed, revealing the dielectric properties of BFO film. Analysis of its electrical behavior demonstrated that Poole–Frenkel emission dominated the leakage current mechanism in the symmetric electrode structure.
Suppression of conductivity in Mn-doped ZnO thin films
Authors: Oo W. M. Hlaing , Saraf L. V. , Engelhard M. H. , Shutthanandan V. , Bergman L. , Huso J. , McCluskey M. D.
Published: January 2009

We studied the dopant concentration distribution and conductivity in ZnO:Mn films grown by metalorganic chemical vapor deposition. The ion beam, surface, and microstructural properties of undoped ZnO films were compared with Mn-doped ZnO films. Suppression of ZnO conductivity was observed for Mn doping up to ∼4.5 at. %. The presence of Mn2+, confirmed by x-ray photoelectron spectroscopy, is correlated with the reduction in conductivity. Variable-temperature Hall effect measurements yield an activation energy of 170 meV, consistent with deep donors in the bulk or at the interface. The results suggest that the incorporation of substitutional Mn suppresses the formation of native defects such as oxygen vacancies.
Hydrogen passivation of deep energy levels at the interfacial grain boundary in (110)/(100) bonded silicon wafers
Authors: Park Yongkook , Lu Jinggang , Rozgonyi George
Published: January 2009

This letter evaluates the density of grain boundary (GB) states before and after hydrogenation by J-V, C-V, and capacitance transient methods using gold/direct silicon-bonded (DSB) (110) thin silicon top layer/(100) silicon substrate junctions. The GB potential energy barrier in thermal equilibrium was reduced by 70 meV from 0.46 eV (before hydrogenation) to 0.39 eV (after hydrogen treatment). Whereas the clean sample had a density of GB states of ∼6×1012 cm−2 eV−1 in the range of Ev+0.54–0.64 eV, hydrogenation reduced the density of GB states to ∼9×1011 cm−2 eV−1 in the range of Ev+0.56–0.61 eV, which is about a sevenfold reduction from that of the clean sample.
Runaway electron energy measurement using hard x-ray spectroscopy in “Damavand” tokamak
Authors: Rasouli C. , Iraji D. , Farahbod A. H. , Akhtari K. , Rasouli H. , Modarresi H. , Lamehi M.
Published: January 2009

Set of experiments has been developed to study existing runaway electrons in “Damavand” tokamak plasma upon characteristics of hard x-ray emissions produced by collision of the runaway electrons with the plasma particles and limiters. As a first step, spatial distribution of hard x-ray emissions on the equatorial plane of the torus was considered. Obtained spectra of hard x-ray emissions for different alignments of shielded detector indicate isotropic emissivity in the equatorial plane. This is in agreement with wide angle cone of bremsstrahlung radiations, deduced from the mean value of energy of the runaway electrons. The mean energy was calculated from the slope of the energy spectrum of hard x-ray photons. In the second stage in order to investigate time evolution of energy of the runaway electrons, similar technique were applied to obtain hard x-ray energy in every 3 ms intervals, from the beginning to the end of plasma. The mean energy of the runaway electrons increases during the ramp up phase and reaches its maximum between 3 and 9 ms after plasma formation. Also considering the time dependence of the counted photons in each energy range shows that energetic photons are emitted during the ramp up phase of the plasma current in Damavand tokamak.
Charged defects and their effects on electrical behavior in Bi1−xLaxFeO3 thin films
Authors: Wang Y. , Zheng R. Y. , Sim C. H. , Wang J.
Published: January 2009

Ferroelectric and dielectric characteristics of Bi1−xLaxFeO3 thin films deposited on SrRuO3 as bottom electrode have been investigated. In accordance with the Rayleigh model, it is in principle established that La doping in BiFeO3 effectively reduces the concentration of charged defects and dielectric loss, although there is a slight deviation at the high level of La doping (x=0.2). This departure is attributed to the reversible bending movement of pinned 180° domain walls, which contributes to the dielectric permittivity nonlinearly without inducing loss. In addition, the competition between domain wall pinning and depinning is determined to be the dominant fatigue mechanism, as shown by the enhanced fatigue endurance at the high La-doping level, test frequency, and electrical field.
Shock induced phase change in KCl single crystals: Orientation relations between the B1 and B2 lattices
Authors: Turneaure Stefan J. , Gupta Y. M. , Rigg Paulo
Published: January 2009

The relative orientations between the lattices of the low pressure (B1) and high pressure (B2) phases of shock compressed KCl single crystals were examined using plate impact loading along the [111] and the [110] directions. The B2-phase lattice planes, perpendicular to the loading direction, were determined from transient x-ray diffraction measurements. Two closely spaced diffraction peaks were observed for the [111] loading direction. The lower Bragg angle peak is consistent with a 200 peak of a cubic B2-phase unit cell giving the orientation relation [111]B1 is parallel to [100]B2. The higher Bragg angle peak is not consistent with any peak from either a cubic B1 or a cubic B2 unit cell; the origin of this peak is unknown. Other experiments found no orientation relations; for the [111] loading direction, [111]B1 is not parallel to [211]B2 and for the [110] loading direction, [110]B1 is not parallel to [100]B2. The orientation relation determined for the [111] loading in this work is incompatible with a previously determined orientation relation obtained for the [100] loading [T. d’Almeida and Y. M. Gupta, Phys. Rev. Lett. 85, 330 (2000)]. This finding suggests that the transformation pathway between the B1 and B2 lattices in KCl crystals depends on the shock compression direction for the B1 phase. The results are discussed in terms of the compatibility between the macroscopic uniaxial strain imposed by shock wave loading and the microscopic rearrangement of atoms leading to the observed orientation relations.
Noise temperature spectrum of hot electrons in semiconductor superlattices
Authors: Wang C. , Cao J. C. , Zhang Chao
Published: January 2009

The small signal response and thermal noise spectra in miniband superlattice are investigated. The properties of hot electron differential mobility, velocity fluctuation, and noise temperature are determined around a stationary condition. The field and frequency dependent drift velocity, electron energy, effective mass, and electron temperature are obtained. At low frequencies, noise temperature increases rapidly with the electric field. Our calculated noise temperatures for miniband superlattice are in good agreement with the experimental results, with the sample thickness estimated to be around 4 μm.
Changes in switching fields of CoCrPt–SiO2 perpendicular recording media due to Ru intermediate layer under low and high gas pressures
Authors: Xia Weixing , Murakami Yasukazu , Shindo Daisuke , Takahashi Migaku
Published: January 2009

It is well known that the deposition of an intermediate Ru layer under high Ar pressure during the fabrication of CoCrPt–SiO2 perpendicular recording media is effective in improving the magnetic properties of the upper CoCrPt–SiO2 layer. The change in the switching fields of the CoCrPt–SiO2 recording layer resulting from the presence of the high-pressure Ru layer is investigated through experiments and computer simulation. The monotonous increase in the magnetic anisotropy Ku and the decrease in the intergranular exchange coupling of the CoCrPt grains due to the presence of the high-pressure Ru layer result in a slight increase in the nucleation field, a significant increase in the coercivity and the saturation field, and a decrease in the slope of the hysteresis loop.
Coalescence overgrowth of GaN nanocolumns on sapphire with patterned metal organic vapor phase epitaxy
Authors: Tang Tsung-Yi , Shiao Wen-Yu , Lin Cheng-Hung , Shen Kun-Ching , Huang Jeng-Jie , Ting Shao-Ying , Liu Tzu-Chi , Yang C. C. , Yao Chiu-Lin , Yeh Jui-Hung , Hsu Ta-Cheng , Chen Wei-Chao , Hsu Hsu-Cheng , Chen Li-Chyong
Published: January 2009

High-quality coalescence overgrowth of patterned-grown GaN nanocolumns on c-plane sapphire substrate with metal organic chemical vapor deposition is demonstrated. Although domain structures of a tens of micron scale in the overgrown layer can be identified with cathodoluminescence measurement, from atomic force microscopy (AFM) measurement, the surface roughness of the overgrown layer in an area of 5×5 μm2 is as small as 0.411 nm, which is only one-half that of the high-quality GaN thin-film template directly grown on sapphire substrate (the control sample). Based on the AFM and depth-dependent x-ray diffraction measurements near the surface of the overgrown layer, the dislocation density is reduced to the order of 107 cm−2, which is one order of magnitude lower than that of the control sample and two to three orders of magnitude lower than those of ordinary GaN templates for fabricating light-emitting diodes. Also, the lateral domain size, reaching a level of ∼2.7 μm, becomes three times larger than the control sample. Meanwhile, the ratio of photoluminescence intensity at room temperature over that at low temperature of the overgrown sample is at least six times higher than that of the control sample. Although the strain in nanocolumns is almost completely released, a stress of ∼0.66 GPa is rebuilt when the coalescence overgrowth is implemented.
Resonant pull-in of a double-sided driven nanotube-based electromechanical resonator
Authors: Ke Changhong
Published: January 2009

We theoretically investigate the electromechanical dynamics of a double-sided driven cantilevered nanotube-based electromechanical resonator. Closed-form analytical solutions capable of predicting the steady-state resonant oscillation of the device and its resonant pull-in conditions are derived using an energy-based method and are verified through a comparison with numerical simulations. Our closed-form formulas clearly reveal the complex relationship among the device geometry, driving voltages, and the device’s electromechanical dynamics. Our results show that the stable steady-state spanning range of the resonating cantilever can reach up to 90% of the gap between the actuation electrodes, which substantially exceeds the previously reported quasistatic pull-in limit for cantilevered nanotube-based nanoelectromechanical systems and the resonant pull-in limit for double-sided driven microelectromechanical gyroscopes. Our results also reveal that the processes of tuning the resonant frequency of the resonator and controlling its stable steady-state oscillation amplitude can be decoupled and controlled separately by controlling the dc and ac components in the driving signal. The unique behavior of the large stable steady-state resonant oscillation range, which is independent of the electrostatic-force-induced resonant frequency tuning, makes this double-sided driven resonator attractive for many applications, such as tunable sensors for detecting ultratiny mass and force and tunable electronics. The results reported in this paper are useful to the optimal design of novel nanotube- or nanowire-based double-sided driven electromechanical resonators.
Dissociative recombination of highly enriched para-H3+
Authors: Tom Brian A. , Zhaunerchyk Vitali , Wiczer Michael B. , Mills Andrew A. , Crabtree Kyle N. , Kaminska Magdalena , Geppert Wolf D. , Hamberg Mathias , af Ugglas Magnus , Vigren Erik , van der Zande Wim J. , Larsson Mats , Thomas Richard D. , McCall Benjamin J.
Published: January 2009

The determination of the dissociative recombination rate coefficient of H3+ has had a turbulent history, but both experiment and theory have recently converged to a common value. Despite this convergence, it has not been clear if there should be a difference between the rate coefficients for ortho-H3+ and para-H3+. A difference has been predicted theoretically and could conceivably impact the ortho:para ratio of H3+ in the diffuse interstellar medium, where H3+ has been widely observed. We present the results of an experiment at the CRYRING ion storage ring in which we investigated the dissociative recombination of highly enriched (∼83.6%) para-H3+ using a supersonic expansion source that produced ions with Trot∼60–100 K. We observed an increase in the low energy recombination rate coefficient of the enriched para-H3+ by a factor of ∼1.25 in comparison to H3+ produced from normal H2 (ortho:para=3:1). The ratio of the rate coefficients of pure para-H3+ to that of pure ortho-H3+ is inferred to be ∼2 at low collision energies; the corresponding ratio of the thermal rate coefficients is ∼1.5 at electron temperatures from 60 to 1000 K. We conclude that this difference is unlikely to have an impact on the interstellar ortho:para ratio of H3+.
Effects of Fe, Ti, and V doping on the microstructure and electrical properties of grain and grain boundary of giant dielectric NiO-based ceramics
Authors: Thongbai Prasit , Pongha Sarawut , Yamwong Teerapon , Maensiri Santi
Published: January 2009

We report the giant dielectric response and electrical properties of Li0.05B0.02Ni0.93O (B=Fe, Ti, and V) ceramics prepared by a polymer pyrolysis route. The giant dielectric response in these materials can be ascribed based on the Maxwell–Wagner polarization and thermally activated mechanisms. It is found that Fe, Ti, and V doping has a strong effect on the microstructure and the conduction of grains and grain boundaries of these NiO-based ceramic systems, which make large contribution to their dielectric properties.
Specific resistance of Pd/Ir interfaces
Authors: Acharyya R. , Nguyen H. Y. T. , Loloee R. , Pratt W. P. , Bass J. , Wang Shuai , Xia Ke
Published: January 2009

From measurements of the current-perpendicular-to-plane total specific resistance (AR=area times resistance) of sputtered Pd/Ir multilayers, we derive the interface specific resistance, 2ARPd/Ir=1.02±0.06 fΩ m2, for this metal pair with closely similar lattice parameters. Assuming a single fcc crystal structure with the average lattice parameter, no-free-parameter calculations (including only spd orbitals) give for perfect interfaces 2ARPd/Ir (perf)=1.21±0.1 fΩ m2, and for interfaces composed of 2 ML of a random 50%-50% alloy 2ARPd/Ir (50/50)=1.22±0.1 fΩ m2. Within mutual uncertainties, these values fall just outside the range of the experimental value. Updating to add f-orbitals gives 2ARPd/Ir (perf)=1.10±0.1 fΩ m2 and 2ARPd/Ir (50-50)=1.13±0.1 fΩ m2, values now compatible with the experimental one. We also update, with f-orbitals, calculations for other pairs.
Quadrupolar magnetic actuation of superparamagnetic particles for enhanced microfluidic perfusion
Authors: Moser Yves , Lehnert Thomas , Gijs Martin A. M.
Published: January 2009

We report on the magnetic actuation of superparamagnetic particles in a microfluidic channel. The formation of a highly confined and dynamic plug of particles extending over the cross section of the microchannel is enabled by superposing a static and a time-varying magnetic field. The latter is generated by an electromagnet and focused across the microchannel using microstructured soft magnetic tips. Finite element calculations of the magnetic force distribution do compare well with experiments. Our system allows maximizing the exposure of superparamagnetic particles to a microfluidic flow of interest for integrated lab-on-a-chip applications.
Stabilizing nanostructured materials by coherent nanotwins and their grain boundary triple junction drag
Authors: Saldana C. , Murthy T. G. , Shankar M. R. , Stach E. A. , Chandrasekar S.
Published: January 2009

The role of nanotwin lamellae in enhancing thermal stability of nanostructured materials is examined. Nanostructured copper with varying densities of twins was generated by controlling the deformation strain rate during severe plastic deformation at cryogenic temperatures. While the nanostructured materials produced under cryogenic conditions are characteristically unstable even at room temperatures, their stability is markedly improved when a dense dispersion of nanotwins is introduced. Observations of the role of nanotwins in pinning grain and subgrain structures suggest an interfacial engineering approach to enhancing the stability of nanostructured alloys.
Ambipolar pentacene/C60-based field-effect transistors with high hole and electron mobilities in ambient atmosphere
Authors: Yan Hu , Kagata Tsubasa , Okuzaki Hidenori
Published: January 2009

Ambipolar field-effect transistors (FETs) were fabricated with a heterostructure of pentacene/C60 in which the C60 layer functioned as an n-type channel while the pentacene layer functioned as both a p-type channel and a sealing capsule for the unstable C60 layer. The ambipolar FET, operating in an ambient atmosphere, exhibited a hole mobility of 0.2 cm2/V s with a threshold voltage of −2.3 V and an electron mobility of 0.04 cm2/V s with a threshold voltage of 66 V with moderately good air stability. However, the threshold voltage and gate voltage for the n-channel operation must be improved for practical applications.
Between Market and State: Dilemmas of Environmental Governance in China's Sulphur Dioxide Emission Trading System
Authors: Tao Julia , Mah Daphne Ngar-Yin
Published: January 2009

Beginning in the 1990s, China has completed two phases of emission trading pilots. In this paper we assess China's pilot programme and analyze how it has been constrained by major problems in three areas of governance capacities: state, policy, and administrative capacities. These problems reflect deeper and more profound dilemmas of market transition experienced by the Chinese government in the past three decades. The dilemmas have resulted in the development of a ‘state-led’ pseudomarket, instead of a full and ‘autonomous’ market, for emission trading in China. It is evidently clear that China still faces many challenges in establishing a market for emission trading which require strengthening its governing capacity in order to address effectively the issues of the rule of law, independent regulation, information disclosure, and public accountability.
Control of extracellular cleavage of ProBDNF by high frequency neuronal activity
Authors: Nagappan Guhan , Zaitsev Eugene , Senatorov Vladimir V. , Yang Jianmin , Hempstead Barbara L. , Lu Bai
Published: January 2009

Pro- and mature neurotrophins often elicit opposing biological effects. For example, mature brain-derived neurotrophic factor (mBDNF) is critical for long-term potentiation induced by high-frequency stimulation, whereas proBDNF facilitate long-term depression induced by low-frequency stimulation. Because mBDNF is derived from proBDNF by endoproteolytic cleavage, mechanisms regulating the cleavage of proBDNF may control the direction of BDNF regulation. Using methods that selectively detect proBDNF or mBDNF, we show that low-frequency stimulation induced predominant proBDNF secretion in cultured hippocampal neurons. In contrast, high-frequency stimulation preferentially increased extracellular mBDNF. Inhibition of extracellular, but not intracellular cleavage of proBDNF greatly reduced high-frequency stimulation-induced extracellular mBDNF. Moreover, high-frequency, but not low-frequency stimulation selectively induced the secretion of tissue plasminogen activator, a key protease involved in extracellular proBDNF to mBDNF conversion. Thus, high-frequency neuronal activity controls the ratio of extracellular proBDNF/mBDNF by regulating the secretion of extracellular proteases. Our study demonstrates activity-dependent control of extracellular proteolytic cleavage of a secretory protein, and reveals an important mechanism that controls diametrically opposed functions of BDNF isoforms.
AICAR Preconditioning Prevents Postischemic Leukocyte Rolling and Adhesion: Role of KATP Channels and Heme Oxygenase
Authors: GASKIN F. SPENCER , KAMADA KAZUHIRO , YUSOF MOZOW , DURANTE WILLIAM , GROSS GARRETT , KORTHUIS RONALD J.
Published: January 2009

Objective: We previously demonstrated that pharmacologic activation of AMP‐activated protein kinase (AMPK) with 5‐aminoimidazole‐4‐carboxamide 1‐β‐D‐ribofuranoside (AICAR) 24 hours prior to (AICAR preconditioning; AICAR‐PC) ischemia/reperfusion (I/R) prevents postischemic leukocyte‐endothelial cell adhesive interactions (LEI) by a mechanism initiated by endothelial nitric oxide synthase (eNOS)‐dependent NO production during the period of AICAR‐PC. The major aim of this study was to examine the role of ATP‐sensitive potassium (KATP) channels and heme oxygenase as mediators of the antiadhesive effects of AICAR‐PC during I/R 24 hours later.

Methods: Intravital fluorescence microscopy was used to quantify LEI in the small intestine of AICAR‐preconditioned C57BL/6J mice treated with KATP channel or heme oxygenase inhibitors during I/R 24 hours after AICAR‐PC in separate experiments.

Results: I/R induced marked increases in LEI relative to sham control mice, proadhesive responses that were prevented by AICAR‐PC 24 hours prior to I/R. The effects of AICAR‐PC to prevent postischemic LEI were abolished by KATP channel or heme oxygenase inhibition during I/R.

Discussion/Conclusion: Our results indicate that the antiadhesive effects of AICAR‐PC are mediated by KATP channel‐ and heme oxygenase‐dependent mechanisms during I/R.
MatrixDB, a database focused on extracellular protein–protein and protein–carbohydrate interactions
Authors: Chautard Emilie , Ballut Lionel , Thierry-Mieg Nicolas , Ricard-Blum Sylvie
Published: January 2009

Summary: MatrixDB (http://matrixdb.ibcp.fr) is a database reporting mammalian protein–protein and protein–carbohydrate interactions involving extracellular molecules. It takes into account the full interaction repertoire of the extracellular matrix involving full-length molecules, fragments and multimers. The current version of MatrixDB contains 1972 interactions corresponding to 4412 experiments and involving 259 extracellular biomolecules.

Availability: MatrixDB is freely available at http://matrixdb.ibcp.fr

Contact:  nicolas.thierry-mieg@imag.fr; s.ricard-blum@ibcp.fr

Supplementary information:  Supplementary data are available at Bioinformatics online.
ProMoT: modular modeling for systems biology
Authors: Mirschel Sebastian , Steinmetz Katrin , Rempel Michael , Ginkel Martin , Gilles Ernst Dieter
Published: January 2009

Summary: The modeling tool ProMoT facilitates the efficient and comprehensible setup and editing of modular models coupled with customizable visual representations. Since its last major publication in 2003, ProMoT has gained new functionality in particular support of logical models, efficient editing, visual exploration, model validation and support for SBML.

Availability: ProMoT is an open source project and freely available at http://www.mpi-magdeburg.mpg.de/projects/promot/.

Contact:  mirschel@mpi-magdeburg.mpg.de; mirschel@mpi-magdeburg.mpg.de

Supplementary information:  Supplementary data are available at Bioinformatics online.
A newcis-acting regulatory element driving gene expression in the zebrafish pineal gland
Authors: Alon Shahar , Eisenberg Eli , Jacob-Hirsch Jasmine , Rechavi Gideon , Vatine Gad , Toyama Reiko , Coon Steven L. , Klein David C. , Gothilf Yoav
Published: January 2009

Motivation: The identification of functional cis-acting DNA regulatory elements is a crucial step towards understanding gene regulation. Ab initio motif detection algorithms have been extensively used in search of regulatory elements. Yet, their success in providing experimentally validated regulatory elements in vertebrates has been limited.

Results: Here we report in silico identification and in vivo validation of regulatory elements that determine enhanced gene expression in the pineal gland of zebrafish. Microarray data enabled detection of genes that exhibit high expression in the pineal gland. The promoter regions of these genes were computationally analyzed in order to identify overrepresented motifs. The highest ranking motif identified is a CRX/OTX binding site, known to govern expression in the pineal gland and retina. The second highest ranking motif was not reported before; we experimentally validated its function in vivo by mutational analysis. The methodology presented here may be applicable as a general scheme for finding regulatory elements that contribute to tissue-specific gene expression.

Contacts:  yoavg@tauex.tau.ac.il; elieis@post.tau.ac.il

Supplementary information:  Supplementary data are available at Bioinformatics online.
DTA: dihedral transition analysis for characterization of the effects of large main-chain dihedral changes in proteins
Authors: Nishima Wataru , Qi Guoying , Hayward Steven , Kitao Akio
Published: January 2009

Motivation: The biological function of proteins is associated with a variety of motions, ranging from global domain motion to local motion of side chain. We propose a method, dihedral transition analysis (DTA), to identify significant dihedral angle changes between two distinct protein conformations and for characterization of the effect of these transitions on both local and global conformation.

Results: Applying DTA to a comprehensive and non-redundant dataset of 459 high-resolution pairs of protein structures, we found that a dihedral transition occurs in 82% of proteins. Multiple dihedral transitions are shown to occur cooperatively along the sequence, which allows us to separate a polypeptide chain into fragments with and without transitions, namely transition fragments (TFs) and stable fragments (SFs), respectively. By characterizing the magnitude of TF conformational change and the effect of the transition on the neighboring fragments, flap and hinge motions are identified as typical motions. DTA is also useful to detect protein motions, subtle in RMSD but significant in terms of dihedral angle changes, such as the peptide-plane flip, the side-chain flip and path-preserving motions. We conclude that DTA is a useful tool to extract potential functional motions, some of which might have been missed using conventional methods for protein motion analysis.

Availability:  http://dynamics.iam.u-tokyo.ac.jp/DTA/

Contact:  kitao@iam.u-tokyo.ac.jp

Supplementary information:  Supplementary data are available at Bioinformatics online.
Morphological convergence and coexistence in three sympatric North American species of Microtus (Rodentia: Arvicolinae)
Authors: Spaeth Paula Ann
Published: January 2009

Aim  Niche theory predicts that ecologically identical species cannot stably coexist in local communities. My aim was to investigate morphological diversity as a possible factor enabling the coexistence of a species‐rich Microtus (Rodentia: Arvicolinae) fauna in a hotspot of North American mammalian diversity, the Greater Yellowstone Ecosystem (GYE).

Location  The Greater Yellowstone Ecosystem, North America.

Methods  Using in‐hand morphological measurements of size and shape, I compared the morphologies of three North American vole species (Microtus spp.), in sympatry in the GYE and in allopatry across their ranges, in order to examine: (1) whether morphologies are fixed or plastic and (2) the degree of morphological character displacement or convergence in sympatric species.

Results  Support was found for plasticity of morphology for all three vole species: M. longicaudus, M. montanus and M. pennsylvanicus. However, Microtus individuals of all species from the GYE area of sympatry were more similar to each other than to allopatric individuals of the same species.

Main conclusions  Competition among these congeners is not manifested in morphological overdispersion. The response of these congeneric species to the same local ecological conditions is convergent. The relative strength of environmental conditions appears to be stronger than the strength of competitive interactions among the study species.
Glycolipids are involved in biofilm accumulation and prolonged bacteraemia in Enterococcus faecalis
Authors: Theilacker Christian , Sanchez‐Carballo Patricia , Toma Ioana , Fabretti Francesca , Sava Irina , Kropec Andrea , Holst Otto , Huebner Johannes
Published: January 2009

Biofilm production is thought to be an important step in many enterococcal infections. In several Gram‐positive bacteria, membrane glycolipids have been implicated in biofilm formation. We constructed a non‐polar deletion mutant of a putative glucosyltransferase designated biofilm‐associated glycolipid synthesis A (bgsA) in Enterococcus faecalis 12030. Analysis of major extracted glycolipids by nuclear magnetic resonance spectroscopy revealed that the cell membrane of 12030ΔbgsA was devoid of diglucosyl–diacylglycerol (DGlcDAG), while monoglucosyl–diacylglycerol was overrepresented. The cell walls of 12030ΔbgsA contained longer lipoteichoic acid molecules and were less hydrophobic than wild‐type bacteria. Inactivation of bgsA in E. faecalis 12030 and E. faecalis V583 led to an almost complete arrest of biofilm formation on plastic surfaces. Overexpression of bgsA, on the other hand, resulted in increased biofilm production. While initial adherence was not affected, bgsA‐deficient bacteria did not accumulate in the growing biofilm. Also, adherence of E. faecalisΔbgsA to Caco‐2 cells was impaired. In a mouse bacteraemia model, E. faecalis 12030ΔbgsA was cleared more rapidly from the bloodstream than the wild‐type strain. In summary, BgsA is a glycosyltransferase synthetizing DGlcDAG, a glycolipid and lipoteichoic acid precursor involved in biofilm accumulation, adherence to host cells, and virulence in vivo.
Cross‐immunity and immune mimicry as mechanisms of resistance to the lantibiotic lacticin 3147
Authors: Draper Lorraine A. , Grainger Karen , Deegan Lucy H. , Cotter Paul D. , Hill Colin , Ross R. Paul
Published: January 2009

Lantibiotics are antimicrobial peptides that possess great potential as clinical therapeutic agents. These peptides exhibit many beneficial traits and in many cases the emergence of resistance is extremely rare. In contrast, producers of lantibiotics synthesize dedicated immunity proteins to provide self‐protection. These proteins have very specific activities and cross‐immunity is rare. However, producers of two peptide lantibiotics, such as lacticin 3147, face the unusual challenge of exposure to two active peptides (α and β). Here, in addition to establishing the contribution of LtnI and LtnFE to lacticin 3147 immunity, investigations were carried out to determine if production of a closely related lantibiotic (i.e. staphylococcin C55) or possession of LtnI/LtnFE homologues could provide protection. Here we establish that not only are staphylococcin C55 producers cross‐immune to lacticin 3147, and therefore represent a natural repository of Staphylococcus aureus strains that are protected against lacticin 3147, but that functional immunity homologues are also produced by strains of Bacillus licheniformis and Enterococcus faecium. This result raises the spectre of resistance through immune mimicry, i.e. the emergence of lantibiotic‐resistant strains from the environment resulting from the possession/acquisition of immunity gene homologues. These phenomena will have to be considered carefully when developing lantibiotics for clinical application.
Microtubule‐severing proteins are involved in flagellar length control and mitosis in Trypanosomatids
Authors: Casanova Magali , Crobu Lucien , Blaineau Christine , Bourgeois Nathalie , Bastien Patrick , Pagès Michel
Published: January 2009

Microtubules are key players in the biology of Trypanosomatid parasites, not only as classical components of the mitotic spindle, microtubule‐organizing centres and flagellum but also as the essential constituent of the cytoskeleton. Their length dynamics are regulated by, among others, microtubule‐severing proteins. Four and six genes encoding microtubule‐severing proteins can be found bioinformatically in the Leishmania major and Trypanosoma brucei genome respectively. We investigated all these proteins in these organisms, which include the katanin, katanin‐like, spastin and fidgetin, and looked at their subcellular localization as well as their putative function by examining ‘loss‐of‐function’ phenotypes. The katanin‐like KAT60b was found implicated in flagellar length reduction, but not in its size increase, while the katanin p80 subunit appeared clearly involved in cytokinesis. Fidgetin and spastin homologues were both localized in the nucleus: the first as a discrete and variable number of dots during most of the cell cycle, redistributing to the spindle and midbody during mitosis; the second concentrated as ≤ 5 perinucleolar punctuations, similar to the electron‐dense plaques identified in T. brucei, which were assimilated to kinetochores. This first study of microtubule‐severing proteins in ‘divergent’ eukaryotes gives further insight into the multiple functions of these proteins identified in the hitherto studied models.
Single 23S rRNA mutations at the ribosomal peptidyl transferase centre confer resistance to valnemulin and other antibiotics in Mycobacterium smegmatis by perturbation of the drug binding pocket
Authors: Long Katherine S. , Poehlsgaard Jacob , Hansen Lykke H. , Hobbie Sven N. , Böttger Erik C. , Vester Birte
Published: January 2009

Tiamulin and valnemulin target the peptidyl transferase centre (PTC) on the bacterial ribosome. They are used in veterinary medicine to treat infections caused by a variety of bacterial pathogens, including the intestinal spirochetes Brachyspira spp. Mutations in ribosomal protein L3 and 23S rRNA have previously been associated with tiamulin resistance in Brachyspira spp. isolates, but as multiple mutations were isolated together, the roles of the individual mutations are unclear. In this work, individual 23S rRNA mutations associated with pleuromutilin resistance at positions 2055, 2447, 2504 and 2572 (Escherichia coli numbering) are introduced into a Mycobacterium smegmatis strain with a single rRNA operon. The single mutations each confer a significant and similar degree of valnemulin resistance and those at 2447 and 2504 also confer cross‐resistance to other antibiotics that bind to the PTC in M. smegmatis. Antibiotic footprinting experiments on mutant ribosomes show that the introduced mutations cause structural perturbations at the PTC and reduced binding of pleuromutilin antibiotics. This work underscores the fact that mutations at nucleotides distant from the pleuromutilin binding site can confer the same level of valnemulin resistance as those at nucleotides abutting the bound drug, and suggests that the former function indirectly by altering local structure and flexibility at the drug binding pocket.