bluuebunny/crossref_metadata_2025 huggingface dataset:
Super-resolution imaging using a three-dimensional metamaterials nanolens
Authors: Casse B. D. F. , Lu W. T. , Huang Y. J. , Gultepe E. , Menon L. , Sridhar S.
Published: January 2010

Super-resolution imaging beyond Abbe’s diffraction limit can be achieved by utilizing an optical medium or “metamaterial” that can either amplify or transport the decaying near-field evanescent waves that carry subwavelength features of objects. Earlier approaches at optical frequencies mostly utilized the amplification of evanescent waves in thin metallic films or metal-dielectric multilayers, but were restricted to very small thicknesses (⪡λ, wavelength) and accordingly short object-image distances, due to losses in the material. Here, we present an experimental demonstration of super-resolution imaging by a low-loss three-dimensional metamaterial nanolens consisting of aligned gold nanowires embedded in a porous alumina matrix. This composite medium possesses strongly anisotropic optical properties with negative permittivity in the nanowire axis direction, which enables the transport of both far-field and near-field components with low-loss over significant distances (>6λ), and over a broad spectral range. We demonstrate the imaging of large objects, having subwavelength features, with a resolution of at least λ/4 at near-infrared wavelengths. The results are in good agreement with a theoretical model of wave propagation in anisotropic media.
Interplay between magnetic impurities and photoinduced carriers in surface depletion layer of anatase Ti1−xCoxO2−δ thin film probed by x-ray photoemission spectroscopy
Authors: Yamashita N. , Sudayama T. , Mizokawa T. , Yamada Y. , Fukumura T. , Kawasaki M.
Published: January 2010

X-ray photoemission spectroscopy measurements with ultraviolet laser illumination have been performed for anatase Ti1−xCoxO2−δ thin films with x=0.05 and 0.10 in order to investigate the interplay between the Co spins and the photoinduced carriers in the surface region. We have found that the surface band bending is removed by the ultraviolet illumination, indicating that photoinduced carriers are injected into the surface depletion layer. After the carrier injection, the position of the chemical potential is governed by the exchange splitting of the Ti 3d conduction band due to the magnetic interaction between the photoinduced carriers and the Co spins.
Reversal of the extraordinary Hall effect polarity in thin Co/Pd multilayers
Authors: Rosenblatt D. , Karpovski M. , Gerber A.
Published: January 2010

Thin Co/Pd multilayers, with room temperature perpendicular anisotropy and an enhanced surface scattering, were studied for the possible use in the extraordinary Hall effect (EHE)-based magnetic memory devices. Polarity of the EHE signal was found to change from negative in thick samples to positive in thin ones. Reversal of EHE sign was also observed in thick samples with aging. The effect is argued to be related to the dominance of surface scattering having the EHE polarity opposite to that of the bulk.
Contact thermal resistance between individual multiwall carbon nanotubes
Authors: Yang Juekuan , Waltermire Scott , Chen Yunfei , Zinn Alfred A. , Xu Terry T. , Li Deyu
Published: January 2010

We report on experimental measurements of contact thermal resistance between individual carbon nanotubes. Results indicate that the contact thermal conductance can increase by nearly two orders of magnitude (from 10−8 to 10−6 W/K) as the contact area increases from a cross contact to an aligned contact. Normalization with respect to the contact area leads to normalized contact thermal resistance on the order of 10−9 m2 K/W at room temperature, one order of magnitude lower than that from a molecular dynamics simulation in literature. These results should have important implications in the design of carbon nanotube-polymer composites for tunable thermal properties.
Dynamic response of metamaterials in the terahertz regime: Blueshift tunability and broadband phase modulation
Authors: Manceau J.-M. , Shen N.-H. , Kafesaki M. , Soukoulis C. M. , Tzortzakis S.
Published: January 2010

Terahertz time-domain spectroscopy is used to probe the electromagnetic properties of metamaterials, which are dynamically photoexcited, using synchronized femtosecond near-infrared laser pulses. Blueshift tunability of the electric dipole metamaterial’s resonance, as well as a broadband phase tunability reaching ∼π/4, are demonstrated. Numerical simulations show the observations are due to changes in the complex index of the photoexcited semiconductor substrate.
Laser spectroscopy of gas confined in nanoporous materials
Authors: Svensson Tomas , Shen Zhijian
Published: January 2010

We show that high-resolution laser spectroscopy can probe surface interactions of gas confined in nanocavities of porous materials. We report on strong line broadening and unfamiliar line shapes due to tight confinement, as well as signal enhancement due to multiple photon scattering. This new domain of laser spectroscopy constitute a challenge for the theory of collisions and spectroscopic line shapes, and open for new ways of analyzing porous materials and processes taking place therein.
Al
2
O
3
/
NbAlO
/
Al
2
O
3
sandwich gate dielectric film on InP
Authors: Cheng Xinhong , Xu Dapeng , Sun Qing-Qing , He Dawei , Wang Zhongjian , Yu Yuehui , Zhang David Wei , Zhao Qingtai
Published: January 2010

Al 2 O 3 / NbAlO / Al 2 O 3 sandwich dielectric films were grown on InP substrate and annealed. X-ray reflectivity measurements suggested that 1.0 nm interfacial layer existed at InP interface, x-ray diffraction and high resolution transmission electron microscopy indicated the films were crystallized. X-ray photoelectron spectra indicated the oxidization of InP substrate, and the valence-band offset between the dielectric film and InP interface was calculated to be 3.1 eV. The electrical measurements indicated that the leakage current density was 40 mA/cm2 at gate bias of 1 V, and the equivalent oxide thickness and the dielectric constant were 1.7 and 20 nm, respectively.
A way to measure electron spin-flipping at ferromagnetic/nonmagnetic interfaces and application to Co/Cu
Authors: Dassonneville B. , Acharyya R. , Nguyen H. Y. T. , Loloee R. , Pratt W. P. , Bass J.
Published: January 2010

We describe a technique, using the current-perpendicular-to-plane (CPP) geometry, to measure the parameter δF/N, characterizing flipping of electron spins at a ferromagnetic (F)/nonmagnetic (N) metallic interface. The technique involves measuring the CPP magnetoresistance of a sample containing a ferromagnetically coupled [F/N]n multilayer embedded within the 20 nm thick central Cu layer of a symmetric Py-based, double exchange-biased spin-valve. To focus on δF/N, the F- and N-layers are made thin compared to their spin-diffusion lengths. We test the technique using F/N=Co/Cu. Analyzing with no adjustable parameters, gives inconsistency with δCo/Cu=0, but consistency with our prior value of δCo/Cu=0.25±0.1. Taking δCo/Cu as adjustable gives δCo/Cu=0.33−0.08+0.03.
Electronic structure and spin coupling of the manganese dimer: The state of the art of ab initio approach
Authors: Buchachenko Alexei A. , Chałasiński Grzegorz , Szczęśniak Małgorzata M.
Published: January 2010

A thorough ab initio study of the Mn2 dimer in its lowest electronic states that correlate to the ground Mn(S6)+Mn(S6) dissociation limit is reported. Performance of multireference methods is examined in calculations of the fully spin-polarized S=5(∑+u11) state against the recent accurate single-reference coupled cluster CCSD(T) results [A. A. Buchachenko, Chem. Phys. Lett. 459, 73 (2008)]. The detailed comparison reveals a serious disagreement between the multireference configuration interaction (MRCI) and related nonperturbative results on the one hand and the complete active space perturbation theory (CASPT) calculations on the other. A striking difference found in the CASPT results of the second and third orders indicates poor perturbation expansion convergence. It is shown that a similar problem has affected most of the previous calculations performed using CASPT2 and similar perturbative approximations. The composition of the active space in the reference multiconfigurational self-consistent field calculations, the core correlation contribution, and basis set saturation effects are also analyzed. The lower spin states, S=0–4, are investigated using the MRCI method. The results indicate a similar dispersion binding for all the spin states within the manifold related to the closed 4s shells, which appears to screen and suppress the spin coupling between the half-filled 3d atomic shells. On this premise, the full set of model potentials is built by combining the accurate reference CCSD(T) interaction potential for S=5 and the MRCI spin-exchange energies for the S<5 states. This approach leads to the value of 550 cm−1 as a lower bound for the ∑+g1 ground-state dissociation energy. The spin-exchange energies themselves are found to comply with the simple Heisenberg model. The effective spin-coupling parameter J is estimated as −3.9 cm−1, a value roughly 2.5 times smaller in magnitude than those measured in the inert gas cryogenic matrices. Compressing of the Mn2 dimer in the matrix cage is suggested as the prime cause of this disagreement.
Ionic force field optimization based on single-ion and ion-pair solvation properties
Authors: Fyta Maria , Kalcher Immanuel , Dzubiella Joachim , Vrbka Luboš , Netz Roland R.
Published: January 2010

Molecular dynamics simulations of ionic solutions depend sensitively on the force fields employed for the ions. To resolve the fine differences between ions of the same valence and roughly similar size and in particular to correctly describe ion-specific effects, it is clear that accurate force fields are necessary. In the past, optimization strategies for ionic force fields either considered single-ion properties (such as the solvation free energy at infinite dilution or the ion-water structure) or ion-pair properties (in the form of ion-ion distribution functions). In this paper we investigate strategies to optimize ionic force fields based on single-ion and ion-pair properties simultaneously. To that end, we simulate five different salt solutions, namely, CsCl, KCl, NaI, KF, and CsI, at finite ion concentration. The force fields of these ions are systematically varied under the constraint that the single-ion solvation free energy matches the experimental value, which reduces the two-dimensional {σ,ε} parameter space of the Lennard-Jones interaction to a one dimensional line for each ion. From the finite-concentration simulations, the pair potential is extracted and the osmotic coefficient is calculated, which is compared to experimental data. We find a strong dependence of the osmotic coefficient on the force field, which is remarkable as the single-ion solvation free energy and the ion-water structure remain invariant under the parameter variation. Optimization of the force field is achieved for the cations Cs+ and K+, while for the anions I− and F− the experimental osmotic coefficient cannot be reached. This suggests that in the long run, additional parameters might have to be introduced into the modeling, for example by modified mixing rules.
Constrained-pairing mean-field theory. III. Inclusion of density functional exchange and correlation effects via alternative densities
Authors: Tsuchimochi Takashi , Scuseria Gustavo E. , Savin Andreas
Published: January 2010

The recently proposed constrained-pairing mean-field theory (CPMFT) is here extended to include exchange and correlation effects from density functional theory (DFT) via alternative densities. We transform from α and β spin densities to alternatives based on the total and on-top pair densities. This transformation is needed because CPMFT produces correct spin-symmetry and space-symmetry adapted densities that traditional DFT functionals are not designed to work with. The inclusion of DFT exchange and correlation effects in CPMFT is well founded both on practical and methodological reasons. We present multiple benchmarks showing that in many cases our model accurately reproduces unrestricted hybrid functional energies (both regular and range separated) and does so on the correct space-symmetry and spin-symmetry surface. Our approach affords efficient inclusion of dynamical correlation effects absent in CPMFT.
A density functional theory study of the CH2I2 reaction on Ag(111): Thermodynamics, kinetics, and electronic structures
Authors: Teng Bo-Tao , Huang Wei-Xin , Wu Feng-Min , Lan You-Zhao , Cao Dong-Bo
Published: January 2010

Density functional theory calculation was performed to study the adsorption and reaction of CH2I2 on Ag(111). Thermodynamically favorable reactions of CH2I2 on Ag(111) are CI bond ruptures and CH2 coupling to form ethylene. The energy barriers for the CI bond ruptures of chemisorbed CH2I2 on Ag(111) are 0.43–0.48 eV, whereas the activation energy for the CH bond rupture of chemisorbed CH2 on Ag(111) is 1.76 eV. The coupling reaction barrier of neighboring chemisorbed CH2 to form C2H4 on Ag(111) was much less than those of the CI bond ruptures of CH2I2(a) and the migration of chemisorbed CH2 on Ag(111). The adsorption behaviors of different surface species on Ag(111) were well explained in terms of the charge density difference.
Comparison of hydrogen and deuterium adsorption on Pd(100)
Authors: Gladys M. J. , Kambali I. , Karolewski M. A. , Soon A. , Stampfl C. , O’Connor D. J.
Published: January 2010

Low energy ion recoil spectroscopy is a powerful technique for the determination of adsorbate position on metal surfaces. In this study, this technique is employed to compare the adsorption sites of hydrogen and deuterium on Pd(100) by detection of either H or D recoil ions produced by Ne+ bombardment. Comparisons of experimental and Kalypso simulated azimuthal yield distributions show that, at room temperature, both hydrogen isotopes are adsorbed in the fourfold hollow site of Pd(100), however, at different heights above the surface (H—0.20 Å and D—0.25 Å). The adsorbates remain in the hollow site at all temperatures up to 383 K even though they move up to 0.40–0.45 Å above the surface. Density functional theory calculations show a similar coverage dependent adsorption height for both H and D and confirm a real difference between the H and D adsorption heights based on zero point energies.
Two-dimensional electronic spectra from the hierarchical equations of motion method: Application to model dimers
Authors: Chen Liping , Zheng Renhui , Shi Qiang , Yan YiJing
Published: January 2010

We extend our previous study of absorption line shapes of molecular aggregates using the Liouville space hierarchical equations of motion (HEOM) method [L. P. Chen, R. H. Zheng, Q. Shi, and Y. J. Yan, J. Chem. Phys. 131, 094502 (2009)] to calculate third order optical response functions and two-dimensional electronic spectra of model dimers. As in our previous work, we have focused on the applicability of several approximate methods related to the HEOM method. We show that while the second order perturbative quantum master equations are generally inaccurate in describing the peak shapes and solvation dynamics, they can give reasonable peak amplitude evolution even in the intermediate coupling regime. The stochastic Liouville equation results in good peak shapes, but does not properly describe the excited state dynamics due to the lack of detailed balance. A modified version of the high temperature approximation to the HEOM gives the best agreement with the exact result.
Molecular dynamics simulation of liquid carbon tetrachloride using ab initio force field
Authors: Li Arvin Huang-Te , Huang Shou-Cheng , Chao Sheng D.
Published: January 2010

Intermolecular interaction potentials of the carbon tetrachloride dimer in 12 orientations have been calculated using the Hartree–Fock self-consistent theory and the second-order Møller–Plesset (MP2) perturbation theory. We have employed basis sets from Pople’s medium size basis sets [up to 6-311++G(3df,3pd)] to Dunning’s correlation consistent basis sets (up to aug-cc-pVQZ). The calculated MP2 potential data were employed to parametrize a four-site force field for molecular simulations. We performed molecular dynamics simulations using the ab initio force field and compared the simulation results to experiments. Quantitative agreements for the atomwise radial distribution functions, the self-diffusion coefficients, and the neutron and x-ray diffraction scattering functions over a wide range of experimental conditions can be obtained, thus validating the ab initio force field without using experimental data a priori.
Carrier localization and nonradiative recombination in yellow emitting InGaN quantum wells
Authors: Li T. , Fischer A. M. , Wei Q. Y. , Ponce F. A. , Detchprohm T. , Wetzel C.
Published: January 2010

InGaN quantum wells, with luminescence in the yellow region of the visible spectrum, have been studied using conventional and time-resolved cathodoluminescence. We observe the absence of strong localization effects and a relatively high internal quantum efficiency of ∼12%, which are unexpected for InGaN in this-long wavelength emission range. We have also observed a steady decrease of the peak emission energy, and a continuous increase in the radiative recombination lifetime with temperature up to 100 K. These two features are manifestations of recombination due to nonlocalized excitons. Nonradiative recombination centers, with activation energy of ∼6 meV, appear to constitute the main mechanism limiting the internal quantum efficiency of these films.
Efficient hybrid evolutionary optimization of interatomic potential models
Authors: Brown W. Michael , Thompson Aidan P. , Schultz Peter A.
Published: January 2010

The lack of adequately predictive atomistic empirical models precludes meaningful simulations for many materials systems. We describe advances in the development of a hybrid, population based optimization strategy intended for the automated development of material specific interatomic potentials. We compare two strategies for parallel genetic programming and show that the Hierarchical Fair Competition algorithm produces better results in terms of transferability, despite a lower training set accuracy. We evaluate the use of hybrid local search and several fitness models using system energies and/or particle forces. We demonstrate a drastic reduction in the computation time with the use of a correlation-based fitness statistic. We show that the problem difficulty increases with the number of atoms present in the systems used for model development and demonstrate that vectorization can help to address this issue. Finally, we show that with the use of this method, we are able to “rediscover” the exact model for simple known two- and three-body interatomic potentials using only the system energies and particle forces from the supplied atomic configurations.
Transcriptional patterns in both host and bacterium underlie a daily rhythm of anatomical and metabolic change in a beneficial symbiosis
Authors: Wier Andrew M. , Nyholm Spencer V. , Mandel Mark J. , Massengo-Tiassé R. Prisca , Schaefer Amy L. , Koroleva Irina , Splinter-BonDurant Sandra , Brown Bartley , Manzella Liliana , Snir Einat , Almabrazi Hakeem , Scheetz Todd E. , Bonaldo Maria de Fatima , Casavant Thomas L. , Soares M. Bento , Cronan John E. , Reed Jennifer L. , Ruby Edward G. , McFall-Ngai Margaret J.
Published: January 2010

Mechanisms for controlling symbiont populations are critical for maintaining the associations that exist between a host and its microbial partners. We describe here the transcriptional, metabolic, and ultrastructural characteristics of a diel rhythm that occurs in the symbiosis between the squid
Euprymna scolopes
and the luminous bacterium
Vibrio fischeri.
The rhythm is driven by the host’s expulsion from its light-emitting organ of most of the symbiont population each day at dawn. The transcriptomes of both the host epithelium that supports the symbionts and the symbiont population itself were characterized and compared at four times over this daily cycle. The greatest fluctuation in gene expression of both partners occurred as the day began. Most notable was an up-regulation in the host of >50 cytoskeleton-related genes just before dawn and their subsequent down-regulation within 6 h. Examination of the epithelium by TEM revealed a corresponding restructuring, characterized by effacement and blebbing of its apical surface. After the dawn expulsion, the epithelium reestablished its polarity, and the residual symbionts began growing, repopulating the light organ. Analysis of the symbiont transcriptome suggested that the bacteria respond to the effacement by up-regulating genes associated with anaerobic respiration of glycerol; supporting this finding, lipid analysis of the symbionts’ membranes indicated a direct incorporation of host-derived fatty acids. After 12 h, the metabolic signature of the symbiont population shifted to one characteristic of chitin fermentation, which continued until the following dawn. Thus, the persistent maintenance of the squid–vibrio symbiosis is tied to a dynamic diel rhythm that involves both partners.
Epibranchial ganglia orchestrate the development of the cranial neurogenic crest
Authors: Coppola Eva , Rallu Murielle , Richard Juliette , Dufour Sylvie , Riethmacher Dieter , Guillemot François , Goridis Christo , Brunet Jean-François
Published: January 2010

The wiring of the nervous system arises from extensive directional migration of neuronal cell bodies and growth of processes that, somehow, end up forming functional circuits. Thus far, this feat of biological engineering appears to rely on sequences of pathfinding decisions upon local cues, each with little relationship to the anatomical and physiological outcome. Here, we uncover a straightforward cellular mechanism for circuit building whereby a neuronal type directs the development of its future partners. We show that visceral afferents of the head (that innervate taste buds) provide a scaffold for the establishment of visceral efferents (that innervate salivatory glands and blood vessels). In embryological terms, sensory neurons derived from an epibranchial placode—that we show to develop largely independently from the neural crest—guide the directional outgrowth of hindbrain visceral motoneurons and control the formation of neural crest–derived parasympathetic ganglia.
Antibody-mediated enhancement of community-acquired methicillin-resistant
Staphylococcus aureus
infection
Authors: Yoong Pauline , Pier Gerald B.
Published: January 2010

Community-acquired infections caused by methicillin-resistant
Staphylococcus aureus
(MRSA) expressing the Panton-Valentine leukocidin (PVL) are rampant, but the contribution of PVL to bacterial virulence remains controversial. While PVL is usually viewed as a cytotoxin, at sublytic amounts it activates protective innate immune responses. A leukotoxic effect might predominate in high inoculum studies, whereas protective proinflammatory properties might predominate in settings with lower bacterial inocula that more closely mimic what initially occurs in humans. However, these protective effects might possibly be neutralized by antibodies to PVL, which are found in normal human sera and at increased levels following PVL
+
S. aureus
infections. In a low-inoculum murine skin abscess model including a foreign body at the infection site, strains deleted for the
pvl
genes replicated more efficiently within abscesses than isogenic PVL
+
strains. Coinfection of mice at separate sites with isogenic PVL
+
and PVL
-
MRSA abrogated the differences in bacterial burdens, indicating a systemic effect on host innate immunity from production of PVL. Mice given antibody to PVL and then infected with seven different PVL
+
strains also had significantly higher bacterial counts in abscesses compared with mice given nonimmune serum. Antibody to PVL had no effect on MRSA strains that did not produce PVL. In vitro, antibody to PVL incapacitated PVL-mediated activation of PMNs, indicating that virulence of PVL
+
MRSA is enhanced by the interference of PVL-activated innate immune responses. Given the high rates of primary and recurring MRSA infections in humans, it appears that antibodies to PVL might contribute to host susceptibility to infection.
Synthetic amyloid-β oligomers impair long-term memory independently of cellular prion protein
Authors: Balducci Claudia , Beeg Marten , Stravalaci Matteo , Bastone Antonio , Sclip Alessandra , Biasini Emiliano , Tapella Laura , Colombo Laura , Manzoni Claudia , Borsello Tiziana , Chiesa Roberto , Gobbi Marco , Salmona Mario , Forloni Gianluigi
Published: January 2010

Inability to form new memories is an early clinical sign of Alzheimer’s disease (AD). There is ample evidence that the amyloid-β (Aβ) peptide plays a key role in the pathogenesis of this disorder. Soluble, bio-derived oligomers of Aβ are proposed as the key mediators of synaptic and cognitive dysfunction, but more tractable models of Aβ−mediated cognitive impairment are needed. Here we report that, in mice, acute intracerebroventricular injections of synthetic Aβ
1–42
oligomers impaired consolidation of the long-term recognition memory, whereas mature Aβ
1–42
fibrils and freshly dissolved peptide did not. The deficit induced by oligomers was reversible and was prevented by an anti-Aβ antibody. It has been suggested that the cellular prion protein (PrP
C
) mediates the impairment of synaptic plasticity induced by Aβ. We confirmed that Aβ
1–42
oligomers interact with PrP
C
, with nanomolar affinity. However, PrP-expressing and PrP knock-out mice were equally susceptible to this impairment. These data suggest that Aβ
1–42
oligomers are responsible for cognitive impairment in AD and that PrP
C
is not required.
Myosin Va cooperates with PKA RIα to mediate maintenance of the endplate in vivo
Authors: Röder Ira V. , Choi Kyeong-Rock , Reischl Markus , Petersen Yvonne , Diefenbacher Markus E. , Zaccolo Manuela , Pozzan Tullio , Rudolf Rüdiger
Published: January 2010

Myosin V motor proteins facilitate recycling of synaptic receptors, including AMPA and acetylcholine receptors, in central and peripheral synapses, respectively. To shed light on the regulation of receptor recycling, we employed in vivo imaging of mouse neuromuscular synapses. We found that myosin Va cooperates with PKA on the postsynapse to maintain size and integrity of the synapse; this cooperation also regulated the lifetime of acetylcholine receptors. Myosin Va and PKA colocalized in subsynaptic enrichments. These accumulations were crucial for synaptic integrity and proper cAMP signaling, and were dependent on AKAP function, myosin Va, and an intact actin cytoskeleton. The neuropeptide and cAMP agonist, calcitonin-gene related peptide, rescued fragmentation of synapses upon denervation. We hypothesize that neuronal ligands trigger local activation of PKA, which in turn controls synaptic integrity and turnover of receptors. To this end, myosin Va mediates correct positioning of PKA in a postsynaptic microdomain, presumably by tethering PKA to the actin cytoskeleton.
Corn content of French fry oil from national chain vs. small business restaurants
Authors: Jahren A. Hope , Schubert Brian A.
Published: January 2010

Several issues, ranging from sustainability to health, may interest the consumers in the corn content of their food. However, because restaurants are excluded from the Nutrition Labeling and Education Act of 1990, national chain restaurants provide nonspecific ingredient information and small businesses supply none. We measured the carbon isotope composition of fry oil in French fries purchased from 68 (67%) of the 101 national chain fast food restaurants on Oahu (i.e., McDonald’s, Burger King, Wendy’s, Arby’s, and Jack in the Box), and paired this with a similar number of small businesses (
n
= 66) to calculate minimum percent contribution of corn to total fry oil. We found that the majority (69%) of the national chain restaurants served fries containing corn oil, whereas this was true for only a minority (20%) of the small businesses. Corn oil is more expensive than soybean oil (for example) when purchased from a small business supplier, suggesting that large-scale corporate agreements are necessary to make corn oil frying cost-effective. When considering French fry oil along with corn-fed beef and chicken, as well as high-fructose corn syrup–sweetened soda, we see the pervasive influence of corn as an ingredient in national chain fast food.
Nanowire transistor arrays for mapping neural circuits in acute brain slices
Authors: Qing Quan , Pal Sumon K. , Tian Bozhi , Duan Xiaojie , Timko Brian P. , Cohen-Karni Tzahi , Murthy Venkatesh N. , Lieber Charles M.
Published: January 2010

Revealing the functional connectivity in natural neuronal networks is central to understanding circuits in the brain. Here, we show that silicon nanowire field-effect transistor (Si NWFET) arrays fabricated on transparent substrates can be reliably interfaced to acute brain slices. NWFET arrays were readily designed to record across a wide range of length scales, while the transparent device chips enabled imaging of individual cell bodies and identification of areas of healthy neurons at both upper and lower tissue surfaces. Simultaneous NWFET and patch clamp studies enabled unambiguous identification of action potential signals, with additional features detected at earlier times by the nanodevices. NWFET recording at different positions in the absence and presence of synaptic and ion-channel blockers enabled assignment of these features to presynaptic firing and postsynaptic depolarization from regions either close to somata or abundant in dendritic projections. In all cases, the NWFET signal amplitudes were from 0.3–3 mV. In contrast to conventional multielectrode array measurements, the small active surface of the NWFET devices, ∼0.06 μm
2
, provides highly localized multiplexed measurements of neuronal activities with demonstrated sub-millisecond temporal resolution and, significantly, better than 30 μm spatial resolution. In addition, multiplexed mapping with 2D NWFET arrays revealed spatially heterogeneous functional connectivity in the olfactory cortex with a resolution surpassing substantially previous electrical recording techniques. Our demonstration of simultaneous high temporal and spatial resolution recording, as well as mapping of functional connectivity, suggest that NWFETs can become a powerful platform for studying neural circuits in the brain.
STUDYING THE ATMOSPHERE OF THE EXOPLANET HAT-P-7b VIA SECONDARY ECLIPSE MEASUREMENTS WITH EPOXI, SPITZER, AND KEPLER
Authors: Christiansen Jessie L. , Ballard Sarah , Charbonneau David , Madhusudhan Nikku , Seager Sara , Holman Matthew J. , Wellnitz Dennis D. , Deming Drake , A'Hearn Michael F.
Published: January 2010

The highly irradiated transiting exoplanet, HAT-P-7b, currently provides one of the best opportunities for studying planetary emission in the optical and infrared wavelengths. We observe six near-consecutive secondary eclipses of HAT-P-7b at optical wavelengths with the EPOXI spacecraft. We place an upper limit on the relative eclipse depth of 0.055% (95% confidence). We also analyze Spitzer observations of the same target in the infrared, obtaining secondary eclipse depths of 0.098% ± 0.017%, 0.159% ± 0.022%, 0.245% ± 0.031%, and 0.225% ± 0.052% in the 3.6, 4.5, 5.8, and 8.0 μm IRAC bands, respectively. We combine these measurements with the recently published Kepler secondary eclipse measurement and generate atmospheric models for the dayside of the planet that are consistent with both the optical and infrared measurements. The data are best fit by models with a temperature inversion, as expected from the high incident flux. The models predict a low optical albedo of ≲0.13, with subsolar abundances of Na, K, TiO, and VO. We also find that the best-fitting models predict that 10% of the absorbed stellar flux is redistributed to the nightside of the planet, which is qualitatively consistent with the inefficient day–night redistribution apparent in the Kepler phase curve. Models without thermal inversions fit the data only at the 1.25σ level, and also require an overabundance of methane, which is not expected in the very hot atmosphere of HAT-P-7b. We also analyze the eight transits of HAT-P-7b present in the EPOXI data set and improve the constraints on the system parameters, finding a period of P = 2.2047308 ± 0.0000025 days, a stellar radius of R
⋆ = 1.824 ± 0.089 R
☉, a planetary radius of Rp
= 1.342 ± 0.068 R
Jup, and an inclination of i = 85.7+3.5
−2.2 deg.
GAM generation by drift waves in JIPP T-llU tokamak core plasmas
Authors: Hamada Y. , Watari T. , Nishizawa A. , Yamagishi O. , Narihara K. , Kawasumi Y. , Ido T. , Kojima M. , Toi K.
Published: January 2010

Density and potential fluctuations were measured in the core region of the JIPP-TIIU plasma using a heavy ion beam probe. By applying a new technique of wavenumber resolved bicoherence, the coupling of the drift waves with zonal flows was clearly observed. In addition, nonlinear energy flow from drift-wave turbulence to high-frequency zonal flows using Ritz's model equation was first observed in the core region of low-density tokamak plasmas, which means there is generation of GAM by drift waves. The nonlinear growth rate of high-frequency zonal flow was estimated to be in the order of 104 s−1 or higher. In additionally heated plasmas where low-frequency ion temperature gradient mode is dominant, the bicoherence pattern changes drastically.
Analysis of evolution of γ-ray emission induced by MeV ions in JET
Authors: Yavorskij V. , Kiptily V. , Challis C. , Goloborod'ko V. , Eriksson L.G. , Hawkes N. , Neururer P. , Reznik S. , Schoepf K. , Sharapov S.E. , Stork D. , Voitsekhovitch I. , Zastrow K.-D.
Published: January 2010

The paper investigates the temporal evolution of γ-ray emission induced by nuclear reactions between energetic D–T fusion-born alpha particles with beryllium impurity ions in JET plasmas, 9Be(α, nγ)12C. During and after tritium NBI blips into JET deuterium plasmas there occurs a delay between alpha production and γ-emission. The delay time observed renders possible the assessment of alpha transport, e.g. loss rates of alphas, and hence may be used for fast ion diagnostics if the characteristic confinement time does not exceed ∼20% of the Spitzer slowing-down time. The analysis of the measured relaxation of γ-emission is further demonstrated for examining the energy distributions of ICRH accelerated 4He ions in the MeV energy range.
Spectra of magnetic perturbations triggered by pellets in JET plasmas
Authors: Poli F.M. , Lang P.T. , Sharapov S.E. , Alper B. , Koslowski H.R.
Published: January 2010

Aiming at investigating edge localised mode (ELM) pacing for future application on ITER, experiments have been conducted on JET injecting pellets in different plasma configurations, including high confinement regimes with type-I and type-III ELMs, low confinement regimes and Ohmically heated plasmas. The magnetic perturbations spectra and the toroidal mode number, n, of triggered events are compared with those of spontaneous ELMs using a wavelet analysis to provide good time resolution of short-lived coherent modes. It is found that—in all these configurations—triggered events have a coherent mode structure, indicating that pellets can trigger an MHD event basically in every background plasma. Two components have been found in the magnetic perturbations induced by pellets, with distinct frequencies and toroidal mode numbers. In high confinement regimes triggered events have similarities with spontaneous ELMs: both are seen to start from low toroidal mode numbers, then the maximum measured n increases up to about 10 within 0.3 ms before the ELM burst.
An advanced disruption predictor for JET tested in a simulated real-time environment
Authors: Rattá G.A. , Vega J. , Murari A. , Vagliasindi G. , Johnson M.F. , de Vries P.C.
Published: January 2010

Disruptions are sudden and unavoidable losses of confinement that may put at risk the integrity of a tokamak. However, the physical phenomena leading to disruptions are very complex and non-linear and therefore no satisfactory model has been devised so far either for their avoidance or their prediction. For this reason, machine learning techniques have been extensively pursued in the last years. In this paper a real-time predictor specifically developed for JET and based on support vector machines is presented. The main aim of the present investigation is to obtain high recognition rates in a real-time simulated environment. To this end the predictor has been tested on the time slices of entire discharges exactly as in real world operation.

Since the year 2000, the experiments at JET have been organized in campaigns named sequentially beginning with campaign C1. In this paper results from campaign C1 (year 2000) and up to C19 (year 2007) are reported. The predictor has been trained with data from JET's campaigns up to C7 with particular attention to reducing the number of missed alarms, which are less than 1%, for a test set of discharges from the same campaigns used for the training. The false alarms plus premature alarms are of the order of 6.4%, for a total success rate of more than 92%. The robustness of the predictor has been proven by testing it with a wide subset of shots of more recent campaigns (from C8 to C19) without any retraining. The success rate over the period between C8 and C14 is on average 88% and never falls below 82%, confirming the good generalization capabilities of the developed technique. After C14, significant modifications were implemented on JET and its diagnostics and consequently the success rates of the predictor between C15 and C19 decays to an average of 79%. Finally, the performance of the developed detection system has been compared with the predictions of the JET protection system (JPS). The new predictor clearly outperforms JPS up to about 180 ms before the disruptions.
Drift stabilization of ballooning modes in a high-⟨β⟩ LHD configuration
Authors: Brocher L. , Cooper W.A. , Graves J.P. , Cooper G.A. , Narushima Y. , Watanabe K.Y.
Published: January 2010

Ideal MHD yields at best inconclusive predictions about the stability of the LHD heliotron for ⟨β⟩ ⩾ 3%. We investigate the impact of the drift stabilization of ballooning modes for the inward-shifted LHD configuration (vacuum magnetic axis R
0 ∼ 3.5 m). The background equilibrium is considered anisotropic in which the neutral beam ions contribute about 1/4 fraction of the total diamagnetic beta, ⟨βdia⟩. A drift corrected ballooning mode equation obtained from the linearized gyrokinetic equation is expanded assuming that the hot particle drifts are much larger than the mode frequency. The fast particle pressure gradients contribute weakly to both the instability drive and the diamagnetic drift stabilization (which is dominated by the thermal ion diamagnetic drifts) for ⟨βdia⟩ ∊ [0, 4.8]%. In the single-fluid limit (diamagnetic drifts ignored), the thermal pressure gradients drive ballooning modes in a broad region encompassing the outer 60–90% of the plasma volume at ⟨βdia⟩ ≈ 4.8%. To stabilize these modes, we find that diamagnetic drift corrections must be invoked (mainly due to the thermal ions). The energetic ion diamagnetic drifts play a role only for low wave number values, k
α ⩽ 8. It has been verified that the fast particle drift ordering imposed by the model is amply satisfied for on-axis hot particle to thermal density N
h0/N
i0 ≈ 1% even at high ⟨βdia⟩.
ASDEX Upgrade—JT-60U comparison and ECRH power requirements for NTM stabilization in ITER
Authors: Urso L. , Zohm H. , Isayama A. , Maraschek M. , Poli E.
Published: January 2010

Neoclassical tearing modes (NTMs) are experimentally controlled with local electron cyclotron current drive (ECCD) and the island width decay during NTM stabilization is modelled using the so-called modified Rutherford equation (MRE). In this paper, a modelling of the MRE is carried out and simulations of the island width decay are compared with the experimentally observed ones in order to fit the two free machine-independent parameters present in the equation. A systematic study on a database of NTM stabilization discharges from ASDEX Upgrade and JT-60U is done for extrapolating the ECCD power requirements for ITER. The extrapolation to ITER of the NTM stabilization results from ASDEX Upgrade and JT-60U shows that 10 MW of ECCD power are enough to stabilize large NTMs. The 10 MW power estimate for ITER is based on the assumption that the free parameters in the MRE are machine independent. Indeed, this assumption is verified in this paper for ASDEX Upgrade and JT-60U. An interesting consequence of the relatively modest power requirement for ITER is that the installed 20 MW will suffice for simultaneous 2/1 and 3/2 NTM stabilization.
Influence of the low order rational q surfaces on the pellet deposition profile
Authors: Commaux N. , Pégourié B. , Baylor L.R. , Köchl F. , Parks P.B. , Jernigan T.C. , Géraud A. , Nehme H.
Published: January 2010

Pellet injection is planned to be the main fuelling method on ITER. The high temperature of the plasma during a fusion burn will limit the penetration of the pellet to the outer third of the minor radius. This limited penetration is expected to be compensated by a polarization drift, which will deposit the particles deeper in the plasma for the pellets injected from the high field side. In order to evaluate the expected depth of the fuelling on ITER, a good understanding of this drift effect is important. Experimental data acquired on the DIII-D (USA) and Tore Supra (France) tokamaks show that the polarization drift is influenced by the low order rational q surfaces. These surfaces appear to attenuate the polarization mechanism as the drifting particles cross them. In this paper, a correlation between the maximum of the pellet mass deposition profile and the positions of the q = 2 and q = 3 surfaces on DIII-D and Tore Supra is shown for high field side and low field side injection. A model is proposed to explain this effect and compared with the experimental results. To conclude, the possible consequences of this phenomenon on the fuelling in ITER are described.
Calculation and experimental test of the cooling factor of tungsten
Authors: Pütterich T. , Neu R. , Dux R. , Whiteford A.D. , O'Mullane M.G. , Summers H.P.
Published: January 2010

The cooling factor of W is evaluated using state of the art data for line radiation and an ionization balance which has been benchmarked with experiment. For the calculation of line radiation, level-resolved calculations were performed with the Cowan code to obtain the electronic structure and excitation cross sections (plane-wave Born approximation). The data were processed by a collisional radiative model to obtain electron density dependent emissions. These data were then combined with the radiative power derived from recombination rates and bremsstrahlung to obtain the total cooling factor. The effect of uncertainties in the recombination rates on the cooling factor was studied and was identified to be of secondary importance. The new cooling factor is benchmarked, by comparisons of the line radiation with spectral measurements as well as with a direct measurement of the cooling factor. Additionally, a less detailed calculation using a configuration averaged model was performed. It was used to benchmark the level-resolved calculations and to improve the prediction on radiation power from line radiation for ionization stages which are computationally challenging. The obtained values for the cooling factor validate older predictions from the literature. Its ingredients and the absolute value are consistent with the existing experimental results regarding the value itself, the spectral distribution of emissions and the ionization equilibrium. A table of the cooling factor versus electron temperature is provided. Finally, the cooling factor is used to investigate the operational window of a fusion reactor with W as intrinsic impurity. The minimum value of nTτ
E
, for which a thermonuclear burn is possible, is increased by 20% for a W concentration of 3.0 × 10−5 compared with a plasma without any impurities, except for the He ash which is considered in both cases.
Analysis of the footprint traces on the first walls of the compact plasma wall interaction device (CPD) using surface analysis and electron orbit calculations
Authors: Sharma S.K. , Zushi H. , Osakabe M. , Takeiri Y. , Yoshida N. , Hasegava M. , Yoshinaga T. , Hanada K. , Idei H. , Sakamoto M. , Nakamura K. , Sato K.N.
Published: January 2010

After the non-inductive current startup experimental campaign on the spherical tokamak compact plasma wall interaction device (CPD), various localized damage tracks or footprint traces have been observed on plasma facing components (PFCs), such as the chamber walls and the ‘stiffeners’ that support them. Although the magnetic field configuration is mainly open, the footprint traces are classified as (1) radially distributed traces, (2) toroidal imperfect circular traces with small gaps, (3) arc-shaped traces and (4) vertically distributed traces. The surface analysis of the samples attached near the traces has been carried out by scanning electron microscopy and x-ray photoelectron spectroscopy. They suggest thin deposition of impurity materials (C, Cu, Ti, Fe and their oxides) over the traces. These footprint traces are analysed in view of the localized plasma wall interaction and the loss of energetic electrons using orbit calculations. Radially distributed traces correspond to the loss of co- and counter-moving passing electrons mainly escaping along the magnetic field lines. The imperfect circular traces are found corresponding to lost orbits of the energetic trapped electrons largely crossing the magnetic field lines. Other traces are also discussed from a viewpoint of loss along the magnetic field lines and impurity deposition.
The effect of plasma profile variation on the stability of the n = 1 internal kink mode in rotating tokamak plasmas
Authors: Chapman I.T. , Graves J.P. , Wahlberg C.
Published: January 2010

The sensitivity of the stability of the ideal n = 1 internal kink mode to variations in the plasma profiles is analysed both analytically and numerically in rotating tokamak plasmas. These stability analyses have been carried out including the centrifugal effects of toroidal plasma rotation upon the equilibrium, and also inconsistently when the equilibrium is treated as static. The change in plasma stability due to rotation is partially (consistent equilibrium) or wholly (inconsistent treatment) determined by the radial profiles of the plasma density and rotation velocity. It is found that the internal kink mode stability is strongly influenced by small variations in these plasma profiles. The implications of this extreme sensitivity are discussed, with particular reference to experimental data from MAST.