bluuebunny/crossref_metadata_2025 huggingface dataset:
Mesoscale modeling of Central American smoke transport to the United States: 1. “Top‐down” assessment of emission strength and diurnal variation impacts
Authors: Wang Jun , Christopher Sundar A. , Nair U. S. , Reid Jeffrey S. , Prins Elaine M. , Szykman James , Hand Jenny L.
Published: March 2006

As is typical in the Northern Hemisphere spring, during 20 April to 21 May 2003, significant biomass burning smoke from Central America was transported to the southeastern United States (SEUS). A coupled aerosol, radiation, and meteorology model that is built upon the heritage of the Regional Atmospheric Modeling System (RAMS), having newly developed capabilities of Assimilation and Radiation Online Modeling of Aerosols (AROMA) algorithm, was used to simulate the smoke transport and quantify the smoke radiative impacts on surface energetics, boundary layer, and other atmospheric processes. This paper, the first of a two‐part series, describes the model and examines the ability of RAMS‐AROMA to simulate the smoke transport. Because biomass‐burning fire activities have distinct diurnal variations, the FLAMBE hourly smoke emission inventory that is derived from the geostationary satellite (GOES) fire products was assimilated into the model. In the “top‐down” analysis, ground‐based observations were used to evaluate the model performance, and the comparisons with model‐simulated results were used to estimate emission uncertainties. Qualitatively, a 30‐day simulation of smoke spatial distribution as well as the timing and location of the smoke fronts are consistent with those identified from the PM2.5 observation network, local air quality reports, and the measurements of aerosol optical thickness (AOT) and aerosol vertical profiles from the Southern Great Plains (SGP) Atmospheric Radiation Measurements (ARM) site in Oklahoma. Quantitatively, the model‐simulated daily mean near‐surface dry smoke mass correlates well with PM2.5 mass at 34 locations in Texas and with the total carbon mass and nonsoil potassium mass (KNON) at three IMPROVE sites along the smoke pathway (with linear correlation coefficients R = 0.77, 0.74, and 0.69 at the significance level larger than 0.99, respectively). The top‐down sensitivity analysis indicates that the total smoke particle emission during the study period is about 1.3 ± 0.2 Tg. The results further indicate that the simulation with a daily smoke emission inventory provides a slightly better correlation with measurements in the downwind region on daily scales but gives an unrealistic diurnal variation of AOT in the smoke source region. This study suggests that the assimilation of emission inventories from geostationary satellites is superior to that of polar orbiting satellites and has important implications for the modeling of air quality in areas influenced by fire‐related pollutants from distant sources.
Observations and model simulations of mixing near the extratropical tropopause
Authors: Pan L. L. , Konopka P. , Browell E. V.
Published: March 2006

Mixing of stratospheric and tropospheric air plays an essential role in the stratosphere‐troposphere exchange (STE) of chemical species. Although evidence of mixing is frequently observed, quantifying its effect has been a significant challenge. We present an analysis using both observations and modeling tools to address the issues of where mixing occurs and how models can quantify its effect to STE across the extratropical tropopause. The data are from remote and in situ measurements on board the NASA DC‐8 during the Subsonic Assessment: Ozone and Nitrogen Oxides Experiment (SONEX). The model simulations use the Chemical Lagrangian Model of the Stratosphere (CLaMS). Our analyses use tracer correlations together with lidar measurements of ozone cross sections to characterize the spatial extent of the observed mixing. The results also serve to identify the air mass that is involved in an irreversible exchange. Results of the CLaMS simulations of lidar and in situ observations for a case observed on 29 October 1997 demonstrate the model's ability to characterize mixing near the tropopause. The results also indicate that using the shear and deformation in large‐scale winds, we can reproduce the observed mixing and the overall features of the stratospheric intrusion. An artificial tracer is used to quantify the transport between the stratosphere and troposphere, to track the preferred location and the cumulative effect of mixing. These results demonstrate progress toward modeling mixing and STE using Lagrangian models and show the potential of the CLaMS model in quantifying the effect of mixing on the chemical composition of the upper tropospheric and lower stratospheric region.
Ozone, water vapor, and temperature in the upper tropical troposphere: Variations over a decade of MOZAIC measurements
Authors: Bortz Sarah E. , Prather Michael J. , Cammas Jean‐Pierre , Thouret Valérie , Smit Herman
Published: March 2006

The MOZAIC (Measurement of Ozone and Water Vapor by Airbus In‐service Aircraft) program (Marenco et al., 1998) has archived in situ measurements of temperature, water vapor, and ozone from August 1994 to December 2003. We analyze the trends, seasonality, and interannual variability of these quantities at aircraft cruise levels (7.7–11.3 km) within the tropics (20°S–20°N). Mean lapse rates for temperature and log(water vapor) are nearly identical in both tropics. The root‐mean‐square variance in temperature over cruise levels, seasons, and years is small, ≤1°C. The seasonal range in water vapor, a factor of 2.5, is much larger than expected from the seasonal range in temperature (1.7°C) if the two scale with the lapse rate relation or the Clausius‐Clapeyron equation. The mean ozone abundance in the region sampled is 45 ppb in the north tropics and 50 ppb in the south tropics. This 112‐month period shows a clearly linear increase in ozone over the north tropics with a trend fit of 1.12 ± 0.05 ppb/yr. In the south tropics, which has a large seasonal range of over 25 ppb, the trend is less obvious but still robust, 1.03 ± 0.08 ppb/yr. These trends in the upper troposphere are twice as large as reported for surface ozone over the tropical Atlantic (Lelieveld et al., 2004), but this pattern of ozone increases is consistent with projected increases driven by industrial emissions.
Mutations of L293 in transmembrane two of the mouse 5‐hydroxytryptamine3A receptor alter gating and alcohol modulatory actions
Authors: Hu Xiang‐Qun , Hayrapetyan Volodya , Gadhiya Jay J , Rhubottom Heather E , Lovinger David M , Machu Tina K
Published: March 2006

The goal of this study was to determine whether mutations of L293 at the 15′ position of TM2 in the 5‐HT3A receptor alter macroscopic current kinetics, and if these changes could account for alterations in alcohol modulation. Receptor function was assessed in Xenopus oocytes under voltage‐clamp and in HEK293 cells with whole‐cell patch‐clamp recording and rapid drug application.

Examination of responses of L293C and L293S receptors to agonist alone revealed enhanced activation, deactivation, and desensitization rates relative to the wild‐type receptor. The L293G mutation produced marked slowing of deactivation and desensitization rates. Increased potency of 5‐HT and increased efficacy of the partial agonist, DA, was also observed in these mutant receptors.

Ethanol and trichloroethanol (TCEt) enhancement of receptor function was reduced or eliminated in receptors containing L293 mutations to C, G, or S. The L293I mutant receptor retained ethanol and TCEt sensitivity. Ethanol and TCEt enhanced activation rate in the wild‐type, but not the L293G and L293S receptors. No relationship was observed between any physicochemical property of the substituted amino acids and the change in alcohol potentiation of function.

The changes in receptor‐channel properties in the mutant receptors support the idea that the L293 residue has important roles in channel gating. Our findings indicate that loss of allosteric modulation by alcohols is not related in any simple way to changes in channel kinetic properties brought about by L293 mutants. We did not observe any evidence that L293 is part of an alcohol binding site.

British Journal of Pharmacology (2006) 148, 88–101. doi:10.1038/sj.bjp.0706685
Suppression of pancreatitis‐related allodynia/hyperalgesia by proteinase‐activated receptor‐2 in mice
Authors: Kawabata Atsufumi , Matsunami Maho , Tsutsumi Masahiro , Ishiki Tsuyoshi , Fukushima Osamu , Sekiguchi Fumiko , Kawao Naoyuki , Minami Takeshi , Kanke Toru , Saito Naohiro
Published: March 2006

Proteinase‐activated receptor‐2 (PAR2), a receptor activated by trypsin and tryptase, is abundantly expressed in the gastrointestinal tract including the C‐fiber terminal, and might play a role in processing of visceral pain. In the present study, we examined and characterized the roles of PAR2 in pancreatitis‐related abdominal hyperalgesia/allodynia in mice.

Caerulein, administered i.p. once, caused a small increase in abdominal sensitivity to stimulation with von Frey hairs, without causing pancreatitis, in PAR2‐knockout (KO) mice, but not wild‐type (WT) mice.

Caerulein, given hourly six times in total, caused more profound abdominal hyperalgesia/allodynia in PAR2‐KO mice, as compared with WT mice, although no significant differences were detected in the severity of pancreatitis between the KO and WT animals.

The PAR2‐activating peptide, 2‐furoyl‐LIGRL‐NH2, coadministered repeatedly with caerulein six times in total, abolished the caerulein‐evoked abdominal hyperalgesia/allodynia in WT, but not PAR2‐KO, mice. Repeated doses of 2‐furoyl‐LIGRL‐NH2 moderately attenuated the severity of caerulein‐induced pancreatitis in WT animals.

Our data from experiments using PAR2‐KO mice provide evidence that PAR2 functions to attenuate pancreatitis‐related abdominal hyperalgesia/allodynia without affecting pancreatitis itself, although the PAR2AP applied exogenously is not only antinociceptive but also anti‐inflammatory.

British Journal of Pharmacology (2006) 148, 54–60. doi:10.1038/sj.bjp.0706708
Cannabinoid 1 (CB1) receptors coupled to cholinergic motorneurones inhibit neurogenic circular muscle contractility in the human colon
Authors: Hinds Nicholas M , Ullrich Katja , Smid Scott D
Published: March 2006

The effects of cannabinoid subtype 1 (CB1) receptor activation were determined on smooth muscle, inhibitory and excitatory motorneuronal function in strips of human colonic longitudinal muscle (LM) and circular muscle (CM) in vitro.

Electrical field stimulation (EFS; 0.5–20 Hz, 50 V) evoked a relaxation in LM and CM precontracted with a neurokinin‐2 (NK‐2) selective receptor agonist (β‐ala8‐neurokinin A; 10−6 M) in the presence of atropine (10−6 M); this was unaltered following pretreatment with the CB1‐receptor selective agonist arachidonyl‐2‐chloroethylamide (ACEA; 10−6 M).

In the presence of nitric oxide synthase blockade with N‐nitro‐L‐arginine (10−4 M), EFS evoked a frequency‐dependent ‘on‐contraction’ during stimulation and an ‘off‐contraction’ following stimulus cessation. On‐contractions were significantly inhibited in CM strips by pretreatment with ACEA (10−6 M). These inhibitory effects were reversed in the presence of the CB1 receptor‐selective antagonist N‐(piperidine‐1‐yl)‐5‐(4‐iodophenyl)‐1‐(2,4‐dichlorophenyl)‐4‐methyl‐1H‐pyrazole‐3‐carboxamide (10−7 M).

ACEA did not alter LM or CM contractile responses to acetylcholine or NK‐2 receptor‐evoked contraction.

Immunohistochemical studies revealed a colocalisation of CB1 receptors to cholinergic neurones in the human colon based on colabelling with choline acetyltransferase, in addition to CB1 receptor labelling in unidentified structures in the CM.

In conclusion, activation of CB1 receptors coupled to cholinergic motorneurones selectively and reversibly inhibits excitatory nerve transmission in colonic human colonic CM. These results provide evidence of a direct role for cannabinoids in the modulation of motor activity in the human colon by coupling to cholinergic motorneurones.

British Journal of Pharmacology (2006) 148, 191–199. doi:10.1038/sj.bjp.0706710
Ranolazine and late cardiac sodium current – a therapeutic target for angina, arrhythmia and more?
Authors: Makielski Jonathan C , Valdivia Carmen R
Published: March 2006

Ranolazine is a new antianginal drug approved for clinical use in the United States in January 2006. A study published in this same issue of theBritish Journal of Pharmacologycharacterizes ranolazine block of late sodium current caused by the long QT syndrome 3 mutations. This commentary discusses the implications of that study and the background and implications for block of late cardiac sodium current in general.

British Journal of Pharmacology(2006)148, 4–6. doi:10.1038/sj.bjp.0706713
Inhibition of Na+/H+‐exchanger with sabiporide attenuates the downregulation and uncoupling of the myocardialβ‐adrenoceptor system in failing rabbit hearts
Authors: Leineweber Kirsten , Aker Stephanie , Beilfuß Anja , Rekasi Heike , Konietzka Ina , Martin Claus , Heusch Gerd , Schulz Rainer
Published: March 2006

Chronic heart failure (HF) is characterized by left ventricular (LV) structural remodeling, impaired function, increased circulating noradrenaline (NA) levels and impaired responsiveness of the myocardialβ‐adrenoceptor (βAR)‐adenylyl cyclase (AC) system. In failing hearts, inhibition of the sodium/proton‐exchanger (NHE)‐1 attenuates LV remodeling and improves LV function. The mechanism(s) involved in these cardioprotective effects remain(s) unclear, but might involve effects on the impairedβAR‐AC system.

Therefore, we investigated whether NHE‐1 inhibition with sabiporide (SABI; 30 mg kg−1 day−1p.o.) might affect myocardialβAR density and AC activity in relation to changes in LV end‐diastolic diameter (LVEDD) and LV systolic fractional shortening (LVS‐FS) after 3 weeks of rapid LV pacing in rabbits.

After 3 weeks of rapid LV pacing LVEDD was significantly increased (Shams 17±0.2 mm,n=9 vs 3wksHF 20±0.5 mm,n=8;P<0.05) and LVS‐FS decreased (Shams 31±1%,n=9 vs 3wksHF 10±1%,n=8;P<0.05). SABI treatment significantly improved LV function independent of whether rabbits were treated after 1 week of pacing (3wksHF+2wksSABI (n=7): LVEDD 18±1 mm; LVS‐FS 16±4%) or before pacing (3wksHF+3wksSABI (n=9): LVEDD 18±1 mm; LVS‐FS 18±6%). After 3 weeks of rapid LV pacing, SABI treatment significantly attenuated increases in serum NA content (Shams 0.83±0.19, 3wksHF 2.68±0.38, 3wksHF+2wksSABI 1.22±0.32, 3wksHF+3wksSABI 1.38±0.33 ng ml−1). Moreover,βAR density (Shams 64±5, 3wksHF 38±3, 3wksHF+2wksSABI 48±4, 3wksHF+3wksSABI 55±3 fmol mg−1protein) and responsiveness (isoprenaline‐stimulated AC activity. (Shams 57.6±4.9, 3wksHF 36.3±6.0, 3wksHF+2wksSABI 56.9±6.0, 3wksHF+3wksSABI 54.5±4.8 pmol cyclic AMP mg−1 protein−1 min−1) were significantly improved in SABI‐treated rabbits.

From the present data we cannot address whether the improvedβAR‐AC system permitted improved LV function and/or whether the improved LV function resulted in less activation of the sympathetic nervous system and by this in a reduced stimulation of theβAR‐AC system. Accordingly, additional studies are needed to fully establish the cause‐and‐effect relationship between NHE‐1 inhibition and the restoration of the myocardialβAR system.

British Journal of Pharmacology(2006)148, 137–146. doi:10.1038/sj.bjp.0706714
Impairment of PAR‐2‐mediated relaxation system in colonic smooth muscle after intestinal inflammation
Authors: Sato Koichi , Ninomiya Hiromichi , Ohkura Shinsuke , Ozaki Hiroshi , Nasu Tetsuyuki
Published: March 2006

Protease‐activated receptor (PAR)‐2 plays important roles in intestinal inflammatory responses. Changes in PAR‐2‐mediated smooth muscle function may contribute pathophysiologically to the intestinal motility disorders often observed in inflammatory bowel disease (IBD).

Stimulation of PAR‐2 by trypsin‐induced relaxation of carbachol‐ and KCl‐induced contractions in normal rat colonic smooth muscle was completely resolved by tissue pretreatment with apamin, but not by pretreatment with l‐NMMA or a cocktail of neuronal blockers (tetrodotoxin, hexamethonium and propranolol).

In colon inflamed by dextran sodium sulphate (DSS), trypsin‐induced inhibitory effects were significantly reduced. Relaxation induced by SLIGRL‐NH2, a selective PAR‐2‐activating peptide, was also reduced in DSS‐treated rat colon. However, inhibitory effects of 1‐ethylbenzimidazolin‐2‐one, an activator of small conductance Ca2+‐activated K+ channel, were unaffected.

Expression of PAR‐2 mRNA in colonic muscularis externa was significantly lower in DSS‐treated rats than in control rats.

These results suggest that the PAR‐2 mediated relaxation system in colonic smooth muscle is suppressed in this experimental colitis rat model, and may contribute to motility disorders in IBD.

British Journal of Pharmacology (2006) 148, 200–207. doi:10.1038/sj.bjp.0706717
Additive Methods for Prediction of Thermochemical Properties. The Laidler Method Revisited. 1. Hydrocarbons
Authors: Leal João Paulo
Published: March 2006

A new parameterization of the Laidler method for estimation of atomization enthalpies and standard enthalpies of formation at 298.15 K for several families of hydrocarbons (alkanes, alkenes, alkynes, polyenes, poly-ynes, alkyl radicals, cycloalkanes, cycloalkenes, benzene derivatives, and polyaromatics) is presented. A total of 200 compounds (164 for liquid phase) are used for the calculation of the parameters. Comparison between the experimental values and those calculated using the group additive scheme led to an average difference of 1.28 kJ⋅mol−1 for the gas phase enthalpy of formation (excluding the polyaromatic compounds) and of 1.38 kJ⋅mol−1 for the liquid phase enthalpy of formation. The data base used appears to be essentially error free, but for some compounds (e.g., 2,2,4-trimethyl-pentane, with the highest deviation among all compounds except the polyaromatic ones) the experimental values might need a reevaluation. An Excel worksheet is provided to simplify the calculation of enthalpies of formation and atomization enthalpies based on the Laidler terms defined in this paper.
IUPAC-NIST Solubility Data Series. 81. Hydrocarbons with Water and Seawater—Revised and Updated. Part 9. C10 Hydrocarbons with Water
Authors: Shaw David G. , Maczynski Andrzej , Goral Marian , Wisniewska-Goclowska Barbara , Skrzecz Adam , Owczarek Iwona , Blazej Krystyna , Haulait-Pirson Marie-Claire , Hefter Glenn T. , Huyskens P. L. , Kapuku F. , Maczynska Zofia , Szafranski Andrzej
Published: March 2006

The mutual solubilities and related liquid–liquid equilibria of C10 hydrocarbons with water are exhaustively and critically reviewed. Reports of experimental determination of solubility in 20 chemically distinct binary systems that appeared in the primary literature prior to end of 2002 are compiled. For ten systems sufficient data are available to allow critical evaluation. All data are expressed as mass percent and mole fraction as well as the originally reported units. In addition to the standard evaluation criteria used throughout the Solubility Data Series, a new method based on the evaluation of the all experimental data for a given homologous series of aliphatic and aromatic hydrocarbons was used.
IUPAC-NIST Solubility Data Series. 81. Hydrocarbons with Water and Seawater—Revised and Updated. Part 10. C11 and C12 Hydrocarbons with Water
Authors: Shaw David G. , Maczynski Andrzej , Goral Marian , Wisniewska-Goclowska Barbara , Skrzecz Adam , Owczarek Iwona , Blazej Krystyna , Haulait-Pirson Marie-Claire , Hefter Glenn T. , Kapuku F. , Maczynska Zofia , Szafranski Andrzej
Published: March 2006

The mutual solubilities and related liquid–liquid equilibria of C11 and C12 hydrocarbons with water and heavy water are exhaustively and critically reviewed. Reports of experimental determination of solubility in 24 chemically distinct binary systems that appeared in the primary literature prior to end of 2002 are compiled. For 12 systems sufficient data are available to allow critical evaluation. All data are expressed as mass percent and mole fraction as well as the originally reported units. In addition to the standard evaluation criteria used throughout the Solubility Data Series, a new method based on the evaluation of all the experimental data for a given series of aliphatic and aromatic hydrocarbons was used.
Medical application of radioactive nuclear beams at HIMAC
Authors: Kitagawa A. , Furusawa Y. , Kanai T. , Kanazawa M. , Mizuno H. , Muramatsu M. , Sato S. , Suda M. , Tomitani T. , Urakabe E. , Yoshimoto M. , Li Q. , Wei Z. , Hanawa K. , Iseki Y. , Sato K.
Published: March 2006

By using the radioactive nuclear beam with relativistic high energy of short-lived positron emitting nuclei, such as C10 and C11, a verification system for the precise radiotherapy has been developed. It is possible to determine the precise particle range and the three-dimensional irradiated area in the human body by a positron camera detector and a positron emission tomography system, respectively. The biological and chemical process of the metabolism is an important parameter for the precise measurement. The biological lifetimes of the C10 and C11 injected into the rabbit’s organs have been observed for the study of metabolism. The microscopic process around the cell is also of interest in the study of biological effectiveness. The observation of the difference between radiological effectiveness of C9 and that of C12 is in progress.
Extraction physics in volume H−-ion sources
Authors: Bacal M. , Hatayama A. , Matsumiya T. , Hamabe M. , Kuroda T. , Oka Y.
Published: March 2006

Recent hydrogen negative-ion sources (JT60, large helical device (LHD)) operate with a magnetic filter field extending up to the plasma electrode and extraction opening. As shown earlier such a magnetic field has a strong effect upon the value of the extracted negative ion and electron current. Measurements of the negative ion and electron density were performed in the ion source, both in the magnetic-field-free region and in the region near the plasma electrode. This work presents the experimental value of the ratio between the extracted negative ion and electron current in different sources. It is shown that the measured current ratio is considerably higher than what can be predicted from a simple thermal flux model based on the density ratio in the bulk of the plasma. We also calculated the ratio between the extracted negative ion and electron currents based on the measured ratio between the negative ion and electron density near the extraction opening using the different theoretical models for electron flux: (1) thermal flux model (I−∕Ie)thermal and (2) collisional flux model (I−∕Ie)coll. The comparisons show that (I−∕Ie)thermal is considerably smaller, while (I−∕Ie)coll tends to be larger than the experimental value. The underlying physics of this discrepancy is discussed.
Electron Interaction Cross Sections for CF3I, C2F4, and CFx (x=1–3) Radicals
Authors: Rozum I. , Limão-Vieira P. , Eden S. , Tennyson J. , Mason N. J.
Published: March 2006

The supply of absolute electron-impact cross sections for molecular targets and radicals is extremely important for developing plasma reactors and testing different types of etching gases. Current demand for such models is high as the industry aims to replace traditional plasma processing gases with less polluting species. New theoretical electron impact cross sections at typical etching plasma energies (sub 10 eV) are presented for the CFx (x=1–3) active radical species in a form suitable for plasma modeling. The available experimental and theoretical data are summarized for two potential feed gases, CF3I and C2F4. This data cover recommended cross sections for electron scattering (total, excitation, momentum transfer, and elastic integral), electron impact dissociation, and dissociative electron attachment, wherever possible. Numerical values are given as tables in the paper and are also placed in the electronic archive.
Reference Data for the Density and Viscosity of Liquid Aluminum and Liquid Iron
Authors: Assael Marc J. , Kakosimos Konstantinos , Banish R. Michael , Brillo Jürgen , Egry Ivan , Brooks Robert , Quested Peter N. , Mills Kenneth C. , Nagashima Akira , Sato Yuzuru , Wakeham William A.
Published: March 2006

The available experimental data for the density and viscosity of liquid aluminum and iron have been critically examined with the intention of establishing a density and a viscosity standard. All experimental data have been categorized into primary and secondary data according to the quality of measurement specified by a series of criteria. The proposed standard reference correlations for the density of the aluminum and iron are characterized by standard deviations of 0.65% and 0.77% at the 95% confidence level, respectively. The overall uncertainty in the absolute values of the density is estimated to be one of ±0.7% for aluminum and 0.8% for iron, which is worse than that of the most optimistic claims but recognizes the unexplained discrepancies between different methods. The standard reference correlations for the viscosity of aluminum and iron are characterized by standard deviations of 13.7% and 5.7% at the 95% confidence level, respectively. The uncertainty in the absolute values of the viscosity of the two metals is thought to be no larger than the scatter between measurements made with different techniques and so can be said to be ±14% in the case of aluminum and ±6% in the case of iron.
Precise formation of geometrically focused ion beams
Authors: Davydenko V. I. , Ivanov A. A. , Korepanov S. A. , Kotelnikov I. A.
Published: March 2006

Geometrically focused intense neutral beams for plasma diagnostic consist of many elementary beams formed by a multiaperture ion-optical system and aimed at the focal point. In real conditions, some of the elementary beams may have increased angular divergence and/or deviate from the intended direction, thus diminishing the neutral beam density at the focus. Several improvements to the geometrical focusing are considered in the article including flattening of the plasma profile across the emission surface, using of quasi-Pierce electrodes at the beam periphery, and minimizing the deviation of the electrodes from the spherical form. Application of these measures to the neutral beam Russian diagnostic injector developed in Budker Institute of Nuclear Physics allows an increase of neutral beam current density in the focus by ∼50%.
Minipermanent magnet high-current microwave ion source
Authors: Song Zhizhong , Peng Shixiang , Yu Jinxiang , Ming Jianchuan , Yuan Zhongxi , Qian Feng , Guo Zhiyu
Published: March 2006

A 2.45GHz high-current microwave ion source with permanent magnet was developed at Peking University. The source body is about 10cm in diameter and 10cm in height, and its weight is less than 5kg. It can operate in both pulse and continuous wave (cw) modes. In pulse mode, more than 100mA hydrogen ion current was extracted from a 5mm ion extraction aperture, when the microwave power is 500W and the extraction voltage is 45kV, which corresponds to a beam density of 500mA∕cm2. In cw mode, up to 60mA of hydrogen ion current can be extracted, and the beam density is 300mA∕cm2 at the same conditions. The proton ratio is about 80% and the normalized root-mean-square emittance is less than 0.1πmmmrad in both modes.
Manifolds on the verge of a hyperbolicity breakdown
Authors: Haro À. , de la Llave R.
Published: March 2006

We study numerically the disappearance of normally hyperbolic invariant tori in quasiperiodic systems and identify a scenario for their breakdown. In this scenario, the breakdown happens because two invariant directions of the transversal dynamics come close to each other, losing their regularity. On the other hand, the Lyapunov multipliers associated with the invariant directions remain more or less constant. We identify notable quantitative regularities in this scenario, namely that the minimum angle between the two invariant directions and the Lyapunov multipliers have power law dependence with the parameters. The exponents of the power laws seem to be universal.
Production of multiply charged ion beams from solid substances with the mVINIS ion source
Authors: Draganić I. , Dobrosavljević A. , Nedeljković T. , Šiljegović M.
Published: March 2006

The mVINIS ion source has enabled us to obtain multiply charged ion beams from gases as well as from solid materials. The solid substance ion beams were produced by using two techniques: (a) the evaporation of metals by using the inlet system based on a minioven and (b) the metal-ions-from-volatile-compounds method (MIVOC) by using the modified gas inlet system. Great efforts were made in the production of high current stable ion beams of solids with relatively high melting points (over 1000°C). The B3+ ion-beam current of over 300μA was one of the most intensive beams extracted until now. The obtained multiply charged ion-beam spectra of solid substances (B, Fe, and Zn) are presented as well as some of the corresponding experimental results achieved during the modification of polymers, carbon materials, and fullerenes.
Extraction of highly charged ions from the Berlin Electron Beam Ion Trap for interactions with a gas target
Authors: Allen F. I. , Biedermann C. , Radtke R. , Fussmann G.
Published: March 2006

Highly charged ions are extracted from the Berlin Electron Beam Ion Trap for investigations of charge exchange with a gas target. The classical over-the-barrier model for slow highly charged ions describes this process, whereby one or more electrons are captured from the target into Rydberg states of the ion. The excited state relaxes via a radiative cascade of the electron to ground energy. The cascade spectra are characteristic of the capture state. We investigate x-ray photons emitted as a result of interactions between Ar17+ ions at energies ⩽5qkeV with Ar atoms. Of particular interest is the velocity dependence of the angular momentum capture state lc.
Emittance and plasma potential measurements in double-frequency heating mode with the 14GHz electron cyclotron resonance ion source at the university of Jyvýskylý
Authors: Tarvainen O. , Suominen P. , Ropponen T. , Koivisto H.
Published: March 2006

The performance of electron cyclotron resonance ion sources can be improved through the use of multiple-frequency heating. However, the physical processes leading into enhanced production of highly charged ions are still mainly unknown. This gave us a strong motivation to perform a set of emittance and plasma potential measurements with the 14GHz electron cyclotron resonance ion source at the university of Jyvýskylý to compare the results obtained in single- and double-frequency heating modes. The measurements were performed with different microwave frequencies and combinations of primary and secondary powers. It was observed that both the emittance of different ion beams and the plasma potential decreased in the single-frequency heating mode as the microwave frequency was increased. The emittance of highly charged ion beams and the plasma potential was slightly lower in double-frequency heating mode than in single-frequency mode with the same source settings and total power.
Atomic wall recombination and volume negative ion production
Authors: Pagano Damiano , Gorse Claudine , Capitelli Mario
Published: March 2006

The development of a numerical code for the modeling of negative ion sources requires the knowledge of a lot of processes occurring both in the gas phase and at the surface. The present work concerns the effect of surface processes (in particular atomic wall recombination) on the kinetics of production/destruction of negative ions. Especially in the pressure regimes useful to produce negative hydrogen ions for thermonuclear applications, wall processes can strongly affect the negative ion production acting on the vibrational distribution of molecular hydrogen.
Advances in the performance and understanding of the Spallation Neutron Source ion source
Authors: Welton R. F. , Stockli M. P. , Murray S. N.
Published: March 2006

The ion source developed for the Spallation Neutron Source (SNS) is a radio-frequency, multicusp source designed to produce ∼40mA of H− with a normalized rms emittance of less than 0.2πmmmrad. To date, the source has been utilized in the commissioning of the SNS accelerator and has already demonstrated stable, satisfactory operation at beam currents of 10–40mA with duty factors of ∼0.1% for operational periods of several weeks. Ultimately the SNS facility will require beam duty factors of 6% (1ms pulse length, 60Hz repetition rate). To ascertain the capability of the source to deliver beams at this duty factor over sustained periods, ongoing experiments are being performed in which the ion source is continuously operated on a dedicated test stand. The results of these tests are reported as well as a theory of the Cs release and transport processes that was derived from these data. The theory was then employed to develop a more effective source-conditioning procedure and a direct-transfer Cs collar, which led to a considerable improvement in source performance.
Results of the CEA/Saclay H electron cyclotron resonance ion source, ECRIN
Authors: Tuske O. , Delferrière O. , Gobin R. , Harrault F. , Steiner T.
Published: March 2006

A 2.45GHz electron cyclotron resonance test stand based on a pure volume H− (negative) ion production is actually under development at CEA Saclay. The negative ion source is working in a pulsed mode, 2ms at 5–10Hz. The first H− ions have been observed at the beginning of 2002 with a poor efficiency: only a few microamperes were produced. Several changes inside the plasma chamber have increased the production rate of negative ions up to several milliamperes. A biased grid separates the plasma chamber into two regions. In the first part, we produce excited H2 molecules that are necessary for producing in the second zone H− ions by a dissociative attachment process located near the extraction zone. Qualitative and quantitative beam diagnostics allow measuring several beam parameters and analyzing the effect of gas mixing or materials on the H− production rate.
A normal form for excitable media
Authors: Gottwald Georg A. , Kramer Lorenz
Published: March 2006

We present a normal form for traveling waves in one-dimensional excitable media in the form of a differential delay equation. The normal form is built around the well-known saddle-node bifurcation generically present in excitable media. Finite wavelength effects are captured by a delay. The normal form describes the behavior of single pulses in a periodic domain and also the richer behavior of wave trains. The normal form exhibits a symmetry preserving Hopf bifurcation which may coalesce with the saddle node in a Bogdanov-Takens point, and a symmetry-breaking spatially inhomogeneous pitchfork bifurcation. We verify the existence of these bifurcations in numerical simulations. The parameters of the normal form are determined and its predictions are tested against numerical simulations of partial differential equation models of excitable media with good agreement.
Synchronization in nonidentical complex Ginzburg-Landau equations
Authors: Zhou C. T.
Published: March 2006

A cross-correlation coefficient of complex fields has been investigated for diagnosing spatiotemporal synchronization behavior of coupled complex fields. We have also generalized the subsystem synchronization way established in low-dimensional systems to one- and two-dimensional Ginzburg-Landau equations. By applying the indicator to examine the synchronization behavior of coupled Ginzburg-Landau equations, it is shown that our subsystem approach may be of better synchronization performance than the linear feedback method. For the linear feedback Ginzburg-Landau equation, the nonidentical system exhibits generalized synchronization characteristics in both amplitude and phase. However, the nonidentical subsystem may exhibit complete-like synchronization properties. The difference between complex fields for driven and response systems gives a linear scaling with the change of their parameter difference.
Chaotic synchronization: A nonlinear predictive filtering approach
Authors: Kurian Ajeesh P. , Puthusserypady Sadasivan
Published: March 2006

The synchronization of chaotic systems is a difficult task due to their sensitive dependence on the initial conditions. Perfect synchronization is almost impossible when noise is present in the system. One of the well known stochastic filtering algorithms that is used to synchronize chaotic systems in the presence of noise is the extended Kalman filter (EKF). However, for highly nonlinear systems, the approximation error introduced by the EKF has been shown to be relatively high. In this paper, a nonlinear predictive filter (NPF) is proposed for synchronizing chaotic systems. In this scheme, it is not required to approximate the underlying nonlinearity and hence there is no need to compute the Jacobian of the chaotic system. Numerical simulations are carried out to compare the performances of the NPF and EKF algorithms for synchronizing different sets of chaotic systems and/or maps. The well known Lorenz and Mackey-Glass systems as well as Ikeda map are used for numerical evaluation of the performance. Results clearly show that the NPF based approach is superior to the EKF based approach in terms of the normalized mean square error (NMSE), total NMSE, and the time taken for synchronization (measured in terms of the normalized instantaneous square error) for all the systems and/or maps considered.
Chaotic dynamics of a passively mode-locked soliton fiber ring laser
Authors: Zhao L. M. , Tang D. Y. , Liu A. Q.
Published: March 2006

We report on the experimental and numerical studies of the chaotic dynamics of a soliton fiber ring laser passively mode-locked by using the nonlinear polarization rotation (NPR) technique. Period-doubling route to chaos on the soliton repetition rate of either the single pulse soliton or the bound solitons of the laser was experimentally observed. Based on a coupled complex Ginzburg-Landau equation model and also taking into account the laser cavity effect, we further show numerically that the period-doubling bifurcations and route to chaos are intrinsic properties of the laser, whose appearance is independent of the details of the laser cavity design and the laser soliton operation. Property of the solitons under the dynamical bifurcations is also numerically investigated.
Simple estimation of absolute free energies for biomolecules
Authors: Ytreberg F. Marty , Zuckerman Daniel M.
Published: March 2006

One reason that free energy difference calculations are notoriously difficult in molecular systems is due to insufficient conformational overlap, or similarity, between the two states or systems of interest. The degree of overlap is irrelevant, however, if the absolute free energy of each state can be computed. We present a method for calculating the absolute free energy that employs a simple construction of an exactly computable reference system which possesses high overlap with the state of interest. The approach requires only a physical ensemble of conformations generated via simulation and an auxiliary calculation of approximately equal central-processing-unit cost. Moreover, the calculations can converge to the correct free energy value even when the physical ensemble is incomplete or improperly distributed. As a “proof of principle,” we use the approach to correctly predict free energies for test systems where the absolute values can be calculated exactly and also to predict the conformational equilibrium for leucine dipeptide in implicit solvent.
Comment on “Exact analytic solutions of nonlinear boundary value problems in fluid mechanics (Blasius equations)” [J. Math. Phys. 46, 033101 (2005)].
Authors: Iacono R.
Published: March 2006

A simple procedure is given to transform the Blasius equation into an Abel equation of the second kind.
Theoretical study of hydrogen dissociative adsorption on the Cu(110) surface
Authors: Salin A.
Published: March 2006

We have calculated the six-dimensional (6D) potential energy surface for H2 in front of a frozen Cu(110) surface using density functional theory for 22 H2-surface configurations and the corrugation reducing procedure to interpolate between them. We carry out classical trajectory calculations on the dissociative adsorption process and find excellent agreement with measurements. We find that it is of prominent importance to account for the rovibrational state distribution in the incident H2 beam. A straightforward analysis leads to the conclusion that the motion along the surface does not play an appreciable role in the dynamics whereas the dynamical role of molecular rotation is crucial. The latter fact precludes any interpretation of dissociation in terms of a static concept such as “barrier distributions.”
Kinetics of interior loop formation in semiflexible chains
Authors: Hyeon Changbong , Thirumalai D.
Published: March 2006

Loop formation between monomers in the interior of semiflexible chains describes elementary events in biomolecular folding and DNA bending. We calculate analytically the interior distance distribution function for semiflexible chains using a mean field approach. Using the potential of mean force derived from the distance distribution function we present a simple expression for the kinetics of interior looping by adopting Kramers theory. For the parameters, that are appropriate for DNA, the theoretical predictions in comparison with the case are in excellent agreement with explicit Brownian dynamics simulations of wormlike chain (WLC) model. The interior looping times (τIC) can be greatly altered in the cases when the stiffness of the loop differs from that of the dangling ends. If the dangling end is stiffer than the loop then τIC increases for the case of the WLC with uniform persistence length. In contrast, attachment of flexible dangling ends enhances rate of interior loop formation. The theory also shows that if the monomers are charged and interact via screened Coulomb potential then both the cyclization (τc) and interior looping (τIC) times greatly increase at low ionic concentration. Because both τc and τIC are determined essentially by the effective persistence length [lp(R)] we computed lp(R) by varying the range of the repulsive interaction between the monomers. For short range interactions lp(R) nearly coincides with the bare persistence length which is determined largely by the backbone chain connectivity. This finding rationalizes the efficacy of describing a number of experimental observations (response of biopolymers to force and cyclization kinetics) in biomolecules using WLC model with an effective persistence length.
Two-terminal longitudinal hotwire sensor for monitoring the position and speed of advancing liquid fronts in microfluidic channels
Authors: Ryu Kee Suk , Shaikh Kashan , Goluch Edgar , Liu Chang
Published: March 2006

We report a simple and practical sensor for monitoring both the absolute position and advancing speed of liquid front in a microfluidic channel. The sensor consists of a longitudinal hot wire element—a two-terminal electrical device, with its length spanning the entire channel. The design, materials, fabrication method, and use of this sensor are extremely simple. Characterization results are presented.
Where surface physics and fluid dynamics meet: Rupture of an amphiphile layer by fluid flow
Authors: Bandi M. M. , Goldburg W. I. , Cressman J. R. , Kellay H.
Published: March 2006

We investigate the fluctuating pattern created by a jet of fluid impingent upon an amphiphile-covered surface. This microscopically thin layer is initially covered with 50μm floating particles so that the layer can be visualized. A vertical jet of water located below the surface and directed upward drives a hole in this layer. The hole is particle-free and is surrounded by the particle-laden amphiphile region. The jet ruptures the amphiphile layer creating a particle-free region that is surrounded by the particle-covered surface. The aim of the experiment is to understand the (fluctuating) shape of the ramified interface between the particle-laden and particle-free regions.
Integrated shadow mask method for patterning small molecule organic semiconductors
Authors: De Vusser Stijn , Steudel Soeren , Myny Kris , Genoe Jan , Heremans Paul
Published: March 2006

We have developed a simple and efficient method for patterning small molecule semiconductors for applications in the field of organic electronics. In our approach, a profile is created using a single layer of photoresist, defining the regions where the organic semiconductor is to be deposited. Subsequent deposition of a small molecule semiconductor results in a discontinuity of the semiconductor film at the photoresist edge. The resulting transistor characteristics have an off current that is systematically below 1pA. We demonstrate both p-type and n-type organic thin-film transistors using this method, using pentacene and copper hexadecafluorophthalocyanine (F16CuPc), respectively.
Synthesis of ordered large-scale ZnO nanopore arrays
Authors: Ding G. Q. , Shen W. Z. , Zheng M. J. , Fan D. H.
Published: March 2006

An effective approach is demonstrated for growing ordered large-scale ZnO nanopore arrays through radio-frequency magnetron sputtering deposition on porous alumina membranes (PAMs). The realization of highly ordered hexagonal ZnO nanopore arrays benefits from the unique properties of ZnO (hexagonal structure, polar surfaces, and preferable growth directions) and PAMs (controllable hexagonal nanopores and localized negative charges). Further evidence has been shown through the effects of nanorod size and thermal treatment of PAMs on the yielded morphology of ZnO nanopore arrays. This approach opens the possibility of creating regular semiconducting nanopore arrays for the application of filters, sensors, and templates.
Random telegraph signal in nanoscale back-side charge trapping memories
Authors: Silva H. , Tiwari S.
Published: March 2006

Random telegraph signal (RTS) was observed in the front and back channel source-drain current of nanoscale double-gated back-side charge trapping memories. The front gate dielectric is silicon oxide and the back gate dielectric is a stack of silicon oxide–silicon nitride–silicon oxide (ONO). The structure provides a tool for traps characterization at multiple interfaces and combinations of materials. Bias dependence of RTS due to a trap in the back ONO was measured to determine the position of the trap in the dielectric. The results show that the individual trap is located within the tunneling oxide, 1.3nm away from the silicon interface. RTS due to traps responsible for the memory properties, located in the silicon nitride or its interface, was not observed.
Influence of oxidizing ambient to tetraethylorthosilicate thin films containing solid-state reaction silicon nanocrystals
Authors: Lau H. W. , Tan O. K.
Published: March 2006

In this work, we present a systematic study on the oxidation of solid-state reaction silicon nanocrystals (Si nc) embedded in tetraethylorthosilicate (TEOS) thin films. The 12.8nm Si nc are spun coated in TEOS thin film and hard baked in O2 ambient at 900°C with varying times. The resulting grain size is investigated using x-ray diffraction and transmission electron microscopy. Si nanoclusters are observed. Upon 900°C oxidation with varying times, three main regions of grain size transition are identified. With short oxidation time, sintering with oxidation at the rim of the agglomerate dominates; at medium oxidation time, full sintering in the agglomerate with pure oxidation retarded by interfacial stress and strain dominates; at long oxidation time, self-limiting effect prevails. Study has been carried out using a combination of classical sintering model and Kao’s two dimensional oxidation model considering the decrease of reaction rate with increasing stress perpendicular to the Si surface. In our developed model, the critical stress for self-limiting oxidation is found to be 2.9×109Pa.