bluuebunny/crossref_metadata_2025 huggingface dataset:
Controlled radical polymerization of styrene and methyl acrylate in the presence of reversible addition–fragmentation chain transfer agents, phenylethyl phenyl dithioacetate and phenyldithioacetic acid
Authors: Goh Yong‐Keng , Whittaker Michael R. , Monteiro Michael J.
Published: September 2005

The use of phenyldithioacetic acid (PDA) in homopolymerizations of styrene or methyl acrylate produced only a small fraction of chains with dithioester end groups. The polymerizations using 1‐phenylentyl phenyldithioacetate (PEPDTA) and PDA in the same reaction showed that PDA had little or no influence on the rate or molecular weight distribution even when a 1:1 ratio is used. The mechanistic pathway for the polymerizations in the presence of PDA seemed to be different for each monomer. Styrene favors addition of styrene to PDA via a Markovnikov type addition to form a reactive RAFT agent. The polymer was shown by double detection SEC to contain dithioester end groups over the whole distribution. This polymer was then used in a chain extension experiment and the Mn was close to theory. A unique feature of this work was that PDA could be used to form a RAFT agent in situ by heating a mixture of styrene and PDA for 24 h at 70 °C and then polymerizing in the presence of AIBN to give a linear increase in Mn and low values of PDI (<1.14). In the case of the polymerization of MA with PDA, the mechanism was proposed to be via degradative chain transfer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5232–5245, 2005
Electrical functionalities of poly(n‐hexyl isocyanate) in solid phase
Authors: Sugita A. , Yamashita Y. , Tasaka S.
Published: September 2005

We report electrical functionalities of a rigid rod‐like helical polymer, poly(n‐hexyl isocyanate) (PHIC), in the solid state. Our experimental results of a displacement (D)–field (E) hysteresis and a measurement of pyroelectric signal proved that the PHIC system was electrically active. From the D–E hysteresis loop, coercive field and remanent polarization were determined to be 6.8 MV/m and 3.0 mC/m2, respectively, at 80 °C. The pyroelectric coefficient was 9.5 mC/m2 K for the sample for which the poling treatment was conducted at 80 °C with the field 20 MV/m. The dipole ordering of the CO dipoles attached to the main chain was responsible for these electrical activities. Relatively small amounts of the remanent polarization and the pyroelectric coefficient possibly resulted from the short‐range dipole ordering in the noncrystalline phase. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3093–3099, 2005
Depressive symptoms, eating psychopathology, and physical activity in obese breast cancer survivors
Authors: Yeter Karen , Rock Cheryl L. , Pakiz Bilge , Bardwell Wayne A. , Nichols Jeanne F. , Wilfley Denise E.
Published: September 2005

Psychosocial problems such as depression are present as long‐term sequelae of breast cancer and its treatment in a substantial minority of patients. In general and patient populations, lifestyle factors such as obesity and physical activity have been associated with depression, and these and related characteristics may be associated with depression in breast cancer survivors. The purpose of this cross‐sectional study was to examine factors associated with depression in overweight or obese women (n=85) who had been diagnosed and treated for early stage breast cancer. Depressive symptoms were measured with the Beck depression inventory (BDI), eating psychopathology was assessed with the eating disorder examination—questionnaire (EDE‐Q), and physical activity was estimated with the seven‐day physical activity recall. BDI was directly correlated with global EDE‐Q score (r=0.56,P<0.01) and inversely associated with age (r=−0.22,P<0.05) in bivariate analysis. Controlling for body mass index, age, education and other factors, BDI was directly associated with global EDE‐Q score (P<0.001) and inversely associated with level of physical activity (P<0.05) in a model that explained 61% of the variance. Eating attitudes and behaviors, and physical activity level, are independently associated with depressive symptoms in overweight or obese breast cancer survivors. Copyright © 2005 John Wiley & Sons, Ltd.
Dual‐affinity avidin molecules
Authors: Hytönen Vesa P. , Nordlund Henri R. , Hörhä Jarno , Nyholm Thomas K. M. , Hyre David E. , Kulomaa Tuomas , Porkka Eevaleena J. , Marttila Ari T. , Stayton Patrick S. , Laitinen Olli H. , Kulomaa Markku S.
Published: September 2005

A recently reported dual‐chain avidin was modified further to contain two distinct, independent types of ligand‐binding sites within a single polypeptide chain. Chicken avidin is normally a tetrameric glycoprotein that binds water‐soluble d‐biotin with extreme affinity (Kd ≈ 10−15 M). Avidin is utilized in various applications and techniques in the life sciences and in the nanosciences. In a recent study, we described a novel avidin monomer‐fusion chimera that joins two circularly permuted monomers into a single polypeptide chain. Two of these dual‐chain avidins were observed to associate spontaneously to form a dimer equivalent to the wt tetramer. In the present study, we successfully used this scaffold to generate avidins in which the neighboring biotin‐binding sites of dual‐chain avidin exhibit two different affinities for biotin. In these novel avidins, one of the two binding sites in each polypeptide chain, the pseudodimer, is genetically modified to have lower binding affinity for biotin, whereas the remaining binding site still exhibits the high‐affinity characteristic of the wt protein. The pseudotetramer (i.e., a dimer of dual‐chain avidins) has two high and two lower affinity biotin‐binding sites. The usefulness of these novel proteins was demonstrated by immobilizing dual‐affinity avidin with its high‐affinity sites. The sites with lower affinity were then used for affinity purification of a biotinylated enzyme. These “dual‐affinity” avidin molecules open up wholly new possibilities in avidin–biotin technology, where they may have uses as novel bioseparation tools, carrier proteins, or nanoscale adapters. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Minimal surface as a model of β‐sheets
Authors: Koh Eunhee , Kim Taehyo
Published: September 2005

The purpose of this article is to present arguments based on experimental data that the β‐sheet structures in proteins are the result of the tendency to minimize surface areas. Thus, we propose the model that all β‐sheet structures are almost minimal surfaces, namely, their mean curvatures are nearly zero. To support this model, we chose 1740 disjoint β‐sheets with less than 10 strands from the all β‐protein class in a nonredundant 40% Structural Classification of Proteins (SCOP) database and applied the least‐squares method to fit the minimal surface catenoid (and in some rare cases, the plane) to the β‐sheet structures. The fitting errors were extremely small: The error of 1729 β‐sheets with catenoid minimal surface is 0.90 ± 0.55 Å and the error of the remaining 11 flat sheets with the plane is 0.64 ± 0.46 Å. The fact that the commonly used models for some β‐sheet surfaces (i.e., the hyperboloid and strophoid) have very small mean curvatures (< 0.05) supports our model. Moreover, we showed that this model also includes the isotropically stressed configuration model proposed by Salemme, in which the intrastrand tendency of the individual chains to twist or coil is in equilibrium with the tendency of the interstrand hydrogen bonding to resist twisting of the sheet as a whole. As an application we used our model to quantify the two principal independent modes in the flexibility of β‐sheets, that is, the bending parameter of β‐sheets and the inclined angle of β‐strands in a sheet. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Human glycerol kinase deficiency: Enzyme kinetics and fibroblast hybridization
Authors: McCabe E. R. B. , Sadava D. , Bullen W. W. , McKelvey H. A. , Seltzer W. K. , Rose C. I.
Published: September 2005

Glycerol kinase deficiency has been associated with neuromuscular, skeletal and adrenal abnormalities and has also been seen in individuals without these clinical findings. Examination of residual enzyme activity in patients' liver, kidney, leukocytes and fibroblasts showed a generalized, heritable defect: the apparentKm for glycerol was increased 5‐200‐fold over control values, whereas the apparentKm for ATP was not significantly altered. This kinetic defect was similar in fibroblasts from clinically different individuals with this inborn error of metabolism. Hybridization of fibroblasts from these individuals showed no evidence of complementation for glycerol kinase activity.
Hyperuricaemia and choreoathetosis in a child without mental retardation or self‐mutilation — a new HPRT variant
Authors: Gottlieb R. P. , Koppel M. M. , Nyhan W. L. , Bakay B. , Nissinen E. , Borden M. , Page T.
Published: September 2005

A thirteen‐year‐old boy is described who had uric acid nephrolithiasis, spasticity and choreoathetosis, but no self‐mutilation or mental retardation. Initial studies suggested the presence of the classic Lesch‐Nyhan enzymatic defect; study of the metabolism of [8‐14C]hypoxanthine and [8‐14C]guanine in intact fibroblasts and careful analysis of the data indicated that this was not the case. This child represents a newly identified variant of the HPRT locus.
Metabolism of collagen in aspartylglycosaminuria: Decreased synthesis by cultured fibroblasts
Authors: Näntö‐Salonen K. , Penttinen R.
Published: September 2005

Abstract Fibroblasts from patients with aspartylglycosaminuria (AGU) and from age‐matched healthy controls were studied in culture. The rate of synthesis of collagenous proteins was lower in AGU fibroblasts than in control cells despite the fact that the growth rates and growth patterns were similar. Qualitative differences in culture media proteins between AGU and control cultures were not revealed by gradient gel electrophoresis or by CM‐cellulose chromatography after pepsin treatment. DEAE‐cellulose chromatography of AGU culture media components showed that they contained more [3H]glucosamine‐labelled glycoproteins than the control cultures

Decreased collagen synthesis may explain the connective tissue symptoms (e.g. skeletal deformations and susceptibility to hernias) frequently present in AGU patients. Products from the incomplete intracellular degradation of glycoproteins can interfere with collagen synthesis in AGU. Aspartylglycosaminuria might thus provide a model for studying the regulation of collagen synthesis.
Mucolipidosis IV, a sialolipidosis due to ganglioside sialidase deficiency
Authors: Cam L. , Tettamanti G. , Berra B. , Sale F. Omodeo , Borrone C. , Gatti R. , Durand P. , Martin J. J.
Published: September 2005

A female patient of Italian, non‐Jewish, descent, 22 years of age, with cloudy corneae, capsular lens opacities and severe and progressive mental and motor deterioration is described.

Ultrastructural examination of a skin biopsy sample showed storage of membranous cytoplasmic bodies in Schwann cells, vessel walls, fibroblasts, smooth muscle fibres and sweat glands, and the presence of some electron‐lucent vacuoles, filled with fibrillo‐granular material, in sweat glands. Biochemical analysis of cultured fibroblasts (from skin explant) showed a complete deficiency of the sialidase acting on gangliosides, while the sialidase acting on sialyllactose and MU‐NeuAc, and several lysomal hydrolases were normal. The urine sediment analysis showed accumulation of all phospholipid species, of several glycolipids and of gangliosides, especially of the polysialylated species.

We conclude that the patient under examination is affected by Mucolipidosis IV and the term ‘sialolipidosis’ is suggested for this inborn disorder.
Increased excretion of four acetyl‐CoA precursors during clinical episode of propionic acidaemia
Authors: Kuhara T. , Shinka T. , Matsumoto I. , Matsuo M.
Published: September 2005

Propionic acidaemia (McKusick 23200) is caused by reduced activity of propionyl‐CoA carboxylase (EC 6.4.1.3). A number of metabolites characteristic of this disease are excreted in patients' urine. We have developed a method of chemical diagnosis using gas chromatography‐mass spectrometry (GC‐MS). Since our first chemical diagnosis (Matsumotoet al., 1978), we have diagnosed seven patients. Profiles of urinary acids, however, varied from patient to patient. Factors affecting these profiles may be genetic make‐up, age, or the patient's clinical and nutritional conditions. We have compared two metabolic profiles of a girl under different clinical conditions and found increased excretion of acetyl‐CoA precursors during clinical episodes.
Neonatal multiple sulphatase deficiency disorder biochemical characterization
Authors: Eto Y. , Tokoro T. , Kureha Y. , Koda N. , Tada Y. , Tahara T. , Maekawa K. , Liebaers I. , Vamos E.
Published: September 2005

Recently, Vamos et al. (1981) reported that the clinical features in the neonatal onset form of multiple sulphatase deficiency (MSD) were much more pro nounced than those of the usual type of MSD. The activities of arylsulphatases A, B and C in the patient's cultured skin fibroblasts were greatly reduced. This paper characterizes the biochemical features of neonatal MSD and distinguishes this disorder from typical MSD.
A new variant form of hypertyrosinaemia due to 4‐hydroxyphenylpyruvic acid oxidase deficiency
Authors: Endo F. , Kitano A. , Uehara I. , Nagata N. , Matsuda I. , Shinka T. , Kuhara T. , Matsumoto I.
Published: September 2005

Two types of hereditary hypertyrosinaemia have been described (La Du and Gjessing, 1978). In this paper we describe familial cases of hypertyrosinaemia, in one of whom detailed enzymatic studies were done on the liver obtained at autopsy. The results suggest the disease as being a new variant of tyrosinaemia.
A lysosomal storage disorder in mice: A model of Niemann‐Pick disease
Authors: Sakiyama T. , Tsuda M. , Kitagawa T. , Fujita R. , Miyawaki S.
Published: September 2005

Recently a strain of C57 BL/KsJ mice showed a progressive degenerative neurologic manifestation with hepatosplenomegaly, similar to Niemann‐Pick disease in humans (Miyawakiet al., 1982). Niemann‐Pick disease (McKusick 25720), a rare genetic disorder, is characterized by sphingomyelin accumulation, parti cularly in the reticuloendothelial system, due to a genetic defect of sphingomyelin catabolism. Animal models as an analogue of human Niemann‐Pick disease have been found in the Siamese cat (Chrispet al., 1970) and CBA mice (Lyonet al., 1965), but no other reports on these strains have been available. The ethical and scientific limitations of human experimentation have made necessary investigations with appropriate animal sys tems. We report here a new murine model to study a lysosomal storage disorder.
Adolescent's perceptions of parenting behaviours and its relationship to adolescent Generalized Anxiety Disorder symptoms
Authors: Hale William W. , Engels Rutger , Meeus Wim
Published: September 2005

This study examined the relationship between how adolescents perceived parenting behaviours and adolescent Generalized Anxiety Disorder (GAD) symptom scores. The 1106 junior high and high school students (12–19 years old; 49.6% males and 50.4% females) completed questionnaires regarding their perception of parenting behaviours and self‐rated symptoms of GAD. The findings of this study demonstrate that adolescent perceptions of parental alienation and rejection are strongly associated with adolescent GAD symptom scores. Additionally, mid‐adolescence females perceive more parental alienation in relation to their GAD symptom scores than both early and mid‐adolescent males. And early adolescent males perceive more parental rejection in relation to their GAD symptom scores than mid‐adolescent males.
The estimation of hidden seal-inflicted losses in the Baltic Sea set-trap salmon fisheries
Authors: Fjälling Arne
Published: September 2005

A database has been constructed using detailed information on catches and seal-disturbance from contracted commercial fishers in the northern Baltic Sea. A model was developed for the calculation of seal-induced losses in set traps for salmon. The model compared catches on consecutive days or day-pairs. It was found that the total losses in set traps were high: 61% of the potential catch in a trend-adjusted sample of paired data. A significant part of these losses, such as fish wholly removed from gear was hidden. The traditional method of assessing losses by counting the remains of fish underestimated losses by 46%. The scaring effect of seal visits was not included. The model was also used for an analysis of the damage process. There were significant negative after-effects of seal visits on catch levels. It was also found that seal visits co-occur with salmon runs. It seems that seals prefer smaller to larger salmon when raiding traps. It is suggested that the traditional method of estimating losses by counting fish remains should be calibrated when used and that the new model with day-pairs should be tried in analyses of seal interference in other fishing operations.
Impact of ticks and tick-borne diseases on agriculture and human populations in Europe
Authors: SPARAGANO O. A. E.
Published: September 2005

Ticks are considered in Europe to be the most important arthropod group responsible for vector-borne diseases in humans, while in the tropics mosquitoes take over this position with ticks being the second most important. Over the last decade, vector-borne diseases have proliferated within Southern Europe (Blue tongue and West Nile viruses, both mosquito-borne diseases) while human ehrlichiosis (a tick-borne disease) has increased dramatically in Eastern Europe.
The analysis of crop cultivar breeding and evaluation trials: an overview of current mixed model approaches
Authors: SMITH A. B. , CULLIS B. R. , THOMPSON R.
Published: September 2005

The analysis of series of crop variety trials has a long history with the earliest approaches being based on ANOVA methods. Kempton (1984) discussed the inadequacies of this approach, summarized the alternatives available at that time and noted that all of these approaches could be classified as multiplicative models. Recently, mixed model approaches have become popular for the analysis of series of variety trials. There are numerous reasons for their use, including the ease with which incomplete data (not all varieties in all trials) can be handled and the ability to appropriately model within-trial error variation. Currently, the most common mixed model approaches for series of variety trials are mixed model versions of the methods summarized by Kempton (1984). In the present paper a general formulation that encompasses all of these methods is described, then individual methods are considered in detail.
A new method for determining meteoroid mass from head echo data
Authors: Close S. , Oppenheim M. , Durand D. , Dyrud L.
Published: September 2005

A head echo is the radar reflection from the plasma immediately surrounding a meteoroid upon its entry into the Earth's atmosphere; analysis of these plasmas can help determine a parent meteoroid's inherent properties, such as mass. In the past, meteoroid mass was calculated using head echo velocity and deceleration data by assuming momentum conservation between the meteoroid and air molecule. We refer to such masses as “dynamical masses.” This method, however, can only be used to determine meteoroid mass if either the meteoroid radius or density is assumed. In this paper, we expound upon a new method for determining a meteoroid's mass by utilizing our new spherical scattering theory. This theory allows us to use head echo measurements to calculate head echo plasma density. Then, by using the plasma density in an established formula that estimates the ratio of unionized to ionized material produced by an ablating meteoroid, we can determine a meteoroid's mass. We refer to such masses as “scattering masses.” We show that our new mass determination method applies to head echoes detected simultaneously at VHF and UHF and verify that the meteoroid mass is the same at both frequencies. We conclude with a comparison between dynamical and scattering masses and show that in general, these methods agree to within an order of magnitude.
Seasonal versus synoptic variability in planktonic production in a high‐latitude marginal sea: The Gulf of St. Lawrence (Canada)
Authors: Le Fouest V. , Zakardjian B. , Saucier F. J. , Starr M.
Published: September 2005

The Gulf of St. Lawrence (Canada) is a subarctic marginal sea characterized by highly variable hydrodynamic conditions that generate a spatial heterogeneity in the marine production. A better understanding of physical‐biological linkages is needed to improve our ability to evaluate the effects of climate variability and change on the gulf's planktonic production. We develop a three‐dimensional (3‐D) eddy permitting resolution physical‐biological coupled model of plankton dynamics in the Gulf of St. Lawrence. The planktonic ecosystem model accounts for the competition between simplified herbivorous and microbial food webs that characterize bloom and post‐bloom conditions, respectively, as generally observed in temperate and subarctic coastal waters. It is driven by a fully prognostic 3‐D sea ice‐ocean model with realistic tidal, atmospheric, and hydrological forcing. The simulation shows a consistent seasonal primary production cycle, and highlights the importance of local sea ice dynamics for the timing of the vernal bloom and the strong influence of the mesoscale circulation on planktonic production patterns at subregional scales.
Fate of fossil fuel CO2 in geologic time
Authors: Archer David
Published: September 2005

A model of the ocean and seafloor carbon cycle is subjected to injection of new CO2 pulses of varying sizes to estimate the resident atmospheric fraction over the coming 100 kyr. The model is used to separate the processes of air‐sea equilibrium, an ocean temperature feedback, CaCO3 compensation, and silicate weathering on the residual anthropogenic pCO2 in the atmosphere at 1, 10, and 100 kyr. The mean lifetime of anthropogenic CO2 is dominated by the long tail, resulting in a range of 30–35 kyr. The long lifetime of fossil fuel carbon release implies that the anthropogenic climate perturbation may have time to interact with ice sheets, methane clathrate deposits, and glacial/interglacial climate dynamics.
Ocean model predictions of chemistry changes from carbon dioxide emissions to the atmosphere and ocean
Authors: Caldeira Ken , Wickett Michael E.
Published: September 2005

We present ocean chemistry calculations based on ocean general circulation model simulations of atmospheric CO2 emission, stabilization of atmospheric CO2 content, and stabilization of atmospheric CO2 achieved in total or in part by injection of CO2 to the deep ocean interior. Our goal is to provide first‐order results from various CO2 pathways, allowing correspondence with studies of marine biological effects of added CO2. Parts of the Southern Ocean become undersaturated with respect to aragonite under the Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios (SRES) A1, A2, B1, and B2 emission pathways and the WRE pathways that stabilize CO2 at 650 ppm or above. Cumulative atmospheric emission of 5000 Pg C produces aragonite undersaturation in most of the surface ocean; 10,000 Pg C also produces calcite undersaturation in most of the surface ocean. Stabilization of atmospheric CO2 at 450 ppm produces both calcite and aragonite undersaturation in most of the deep ocean. The simulated SRES pathways produce global surface pH reductions of ∼0.3–0.5 units by year 2100. Approximately this same reduction is produced by WRE650 and WRE1000 stabilization scenarios and by the 1250 Pg C emission scenario by year 2300. Atmospheric emissions of 5000 Pg C and 20,000 Pg C produce global surface pH reductions of 0.8 and 1.4 units, respectively, by year 2300. Simulations of deep ocean CO2 injection as an alternative to atmospheric release show greater chemical impact on the deep ocean as the price for having less impact on the surface ocean and climate. Changes in ocean chemistry of the magnitude shown are likely to be biologically significant.
Characteristics of tropopause folds over Arctic latitudes
Authors: Rao T. Narayana , Kirkwood S.
Published: September 2005

Characteristics of tropopause folds over Arctic latitudes have been studied using VHF radar measurements supplemented by balloon measurements. The variation of the radar parameters during the passage of tropopause folds is discussed in detail. To our knowledge, these observations constitute the first spaced antenna (SA) radar measurements during the passage of tropopause folds. This allows us to compare the parameters detectable using this mode with those observed using other configurations, such as the Doppler beam swinging (DBS) technique. In general, the structural characteristics, such as the slope of folds, seem to be similar at Arctic latitudes to that at midlatitudes; however, the height of the tropopause and the axis of the jet stream (and hence the folding) are found to be lower by 1–2 km than their counterparts in midlatitudes. In the case studies the radar‐derived parameters, such as the signal‐to‐noise ratio (SNR) and vertical shear of horizontal wind, clearly show the upper‐air frontal zone. The frontal circulation, conceived from vertical velocity, including the warm conveyer belt flow and the dry intrusion, is clearly visible in the first case, whereas it is masked by high‐amplitude mountain lee waves in the second case. Further, the frontal zone seems to be acting as a critical layer to mountain lee wave activity by absorbing/filtering the wave activity. The aspect angles derived from the present analysis agree well with those estimated by vertical beam spectral width but are small in comparison with those estimated by the power ratio method. The mean full correlation analysis (FCA) turbulent velocity is estimated using the ESRAD data obtained during the passage of 15 tropopause folds. The mean eddy diffusion coefficients, Kz, near the tropopause and in the upper portion of the fold, where strong turbulence is seen in case studies, are found to be 3.54 and 6.4 m2 s−1, respectively. Utilizing the mean Kz and the mean ozone gradient (obtained from ozonesondes) values, the ozone fluxes across the tropopause and topside of the fold due to turbulence are estimated as 0.71 m s−1 ppbv and 0.32 m s−1 ppbv, respectively. Although the flux across the tropopause is more than that occurring near the fold, the exchange occurring through folds could be more significant to the tropospheric chemical budget.
A new pathway for communicating the 11‐year solar cycle signal to the QBO
Authors: Cordero Eugene C. , Nathan Terrence R.
Published: September 2005

The response of the equatorial quasi‐biennial oscillation (QBO) to zonal‐mean ozone perturbations consistent with the 11‐year solar cycle is examined using a 2 dimensional model of the tropical stratosphere. Unique to this model are wave‐ozone feedbacks, which provide a new, nonlinear pathway for communicating solar variability effects to the QBO. Model simulations show that for zonal‐mean ozone perturbations representative of solar maximum (minimum), the diabatic heating due to the wave‐ozone feedbacks is primarily responsible for driving a slightly stronger (weaker) QBO circulation and producing a slightly shorter (longer) QBO period. These results, which are explained via an analytical analysis of the divergence of Eliassen‐palm flux, are in general agreement with observations of quasi‐decadal variability of the QBO.
Radial evolution of the electron distribution functions in the fast solar wind between 0.3 and 1.5 AU
Authors: Maksimovic M. , Zouganelis I. , Chaufray J.‐Y. , Issautier K. , Scime E. E. , Littleton J. E. , Marsch E. , McComas D. J. , Salem C. , Lin R. P. , Elliott H.
Published: September 2005

Observed electron distribution functions of the solar wind permanently exhibit three different components: a thermal core and a suprathermal halo, which are always present at all pitch angles, and a sharply magnetic field aligned “strahl” which is usually anti‐sunward moving. Whereas Coulomb collisions can explain the relative isotropy of the core population, the origin of the halo population, and more specifically the origin of its sunward directed part, remains unknown. In this study we present the radial evolution of the electron velocity distribution functions in the fast solar wind between 0.3 and 1.5 AU. For this purpose we combine data measured separately by the Helios, Wind, and Ulysses spacecraft. We compute average distributions over distance and normalize them to 1 AU to remove the effects of the solar wind expansion. Then we model separately the core, halo, and strahl components to compute their relative number density or fraction of the total electron density. We observe that, while the core fractional density remains roughly constant with radial distance, the halo and strahl fractional densities vary in an opposite way. The relative number of halo electrons is increasing, while the relative number of strahl electrons is decreasing with distance. Therefore we provide, for the first time, strong evidences for a scenario that is commonly assumed: the heliospheric electron halo population consists partly of electrons that have been scattered out of the strahl.
A climatology of cutoff lows in the Southern Hemisphere
Authors: Fuenzalida Humberto A. , Sánchez Rodrigo , Garreaud René D.
Published: September 2005

The occurrence of cutoff lows (COLs) in the Southern Hemisphere at 500 hPa is studied for a 31‐year period using atmospheric NCEP‐NCAR reanalysis. The methodology combines objective detection and tracking for cyclonic systems with visual inspection in order to select those systems that segregate equatorward from the main westerlies. Hemispheric charts and frequency distributions are presented for COL distribution, initial and final locations, duration, intensity, and motion. COLs tend to cluster around the three main continental areas and to have a low frequency of occurrence over the oceans. Because particular features are shown by the COLs associated with each continent, three longitudinal sectors centered in Africa, Australia, and South America are defined. From the total of 1253 COLs detected, 10% were found in the African sector, 48% were found in the Australian sector, and 42% were found in the South American sector. Marked seasonal cycles with summer minima are found around South America and Africa but not over Australia. Over South America, net dissipation of COLs prevails while over Australia, generation is the dominant process. Active storm tracks and moist conditions seem to be responsible for fewer COLs, while low winds in the upper troposphere and dry conditions in the lower troposphere are associated with a higher frequency of occurrence. A trend in the number of COLs is significant only near South America with higher COLs after 1990. No relation was found between COL frequencies and the ENSO phenomena.
The integrated photon echo and solvation dynamics. II. Peak shifts and two-dimensional photon echo of a coupled chromophore system
Authors: Cho Minhaeng , Fleming Graham R.
Published: September 2005

A theoretical description of one- and two-color photon echo peak shifts (PEPS) and two-dimensional (2D) photon echo spectrum (PES) of a coupled chromophore system are presented. The effects of population relaxation in the one-exciton states on both the PEPS and the 2D PES are investigated. For values of time T shorter than the population relaxation time, a finite two-color peak shift magnitude and nonzero cross peaks in the 2D PES provide evidence of electronic coupling between the chromophores. These two distinct observables, i.e., PEPS and off-diagonal peaks, both originate from the electronic coupling. However, it is shown that the PEPS and 2D PES methods can provide complementary information on the structure-dependent nonlinear optical responses of coupled chromophore systems.
Stability and structure of polyelectrolyte multilayers deposited from salt free solutions
Authors: Abu-Sharkh Basel
Published: September 2005

Molecular-dynamics (MD) simulation results show that polyelectrolyte multilayers deposited from salt free solutions on charged planar surfaces are thermodynamically stable structures that form spontaneously regardless of the method of deposition. The simulation also shows that the polyelectrolyte multilayers are “fuzzy” in nature and molecules in one layer interpenetrate other layers. The influence of chain length, surface charge, and polymer charge is also investigated. Layer thickness was found to be independent of chain length. The ratio of surface to chain charge was found to influence the thickness of the first layer and the amount of polymer absorbed in the first few layers. The thickness of the subsequent layers was found to be independent of the charge ratio.
Stabilization of amorphous GaN by oxygen
Authors: Budde F. , Ruck B. J. , Koo A. , Granville S. , Trodahl H. J. , Bittar A. , Williams G. V. M. , Ariza M. J. , Bonnet B. , Jones D. J. , Metson J. B. , Rubanov S. , Munroe P.
Published: September 2005

We have investigated experimentally the structure of disordered GaN films. The results suggest that it is not possible to stabilize an amorphous network in stoichiometric films, and the GaN instead consists of random-stacked nanocrystals of some 3-nm diameter. However, incorporation of 15% or more oxygen stabilizes an amorphous phase, which we attribute to the presence of nontetrahedral bonds centered on oxygen. The ionic favorability of heteropolar bonds and its strikingly simple constraint to even-membered rings are the likely causes of the instability of stoichiometric a-GaN.
Direct determination of the ionization energies of FeO and CuO with VUV radiation
Authors: Metz Ricardo B. , Nicolas Christophe , Ahmed Musahid , Leone Stephen R.
Published: September 2005

Photoionization efficiency curves were measured for gas-phase FeO and CuO using tunable vacuum-ultraviolet radiation at the Advanced Light Source. The molecules are prepared using laser ablation of a metal-oxide powder in a novel high-repetition-rate source and are thermally moderated in a supersonic expansion. These measurements provide the first directly measured ionization energy for CuO, IE(CuO)=9.41±0.01eV. The direct measurement also gives a greatly improved ionization energy for FeO, IE(FeO)=8.56±0.01eV. The ionization energy connects the dissociation energies of the neutral and cation, leading to a refined bond strength for the FeO cation: D0(Fe+–O)=3.52±0.02eV. A dramatic increase in the photoionization cross section at energies of 0.36eV above the threshold ionization energy is assigned to autoionization and direct ionization involving one or more low-lying quartet states of FeO+. The interaction between the sextet ground state and low-lying quartet states of FeO+ is key to understanding the oxidation of hydrogen and methane by FeO+, and these experiments provide the first experimental observation of the low-lying quartet states of FeO+.
Turbulence regulation by stochastic zonal flows in dynamical models
Authors: Kim Eun-jin
Published: September 2005

A theory of turbulence reduction by zonal flows is presented in the interchange turbulence model. Zonal flows with a finite correlation time τZF are shown to lead to a significant reduction in particle transport and turbulence amplitude, with the scalings ⟪nυx⟫∝τDΩeff−1∝Ωeff−3∕2, ⟪n2⟫∝τD∝Ωeff−1∕2, and ⟪υx2⟫∝τDΩeff−2∝Ωeff−5∕2. Here, Ωeff=τZFΩrms2, τD=(τη∕Ωeff)1∕2, and τη are the effective shearing rate, effective decorrelation time, and diffusive turbulent scattering time, respectively. Compared to the transport of passive scalar fields [E. Kim and P. H. Diamond, Phys. Plasmas, 11, L77 (2004)], the reduction is much more severe due to the suppression of turbulent velocity. However, the overall transport and turbulence amplitude are still larger compared with the case of coherent shearing because shearing by random zonal flows with a finite correlation time is less efficient, with a longer decorrelation time τD than (τη∕Ω2)1∕3 in the case of coherent shearing.
On the dynamics of edge-core coupling
Authors: Hahm T. S. , Diamond P. H. , Lin Z. , Rewoldt G. , Gurcan O. , Ethier S.
Published: September 2005

One of the nagging, unresolved questions in fusion theory is concerned with the extent of the edge. Gyrokinetic particle simulations of toroidal ion temperature gradient turbulence spreading using the gyrokinetic toroidal code [Z. Lin, T. S. Hahm, W. W. Lee, W. M. Tang, and R. B. White, Science 281, 1835 (1998)] and its related dynamical model have been extended to a system with radially varying ion temperature gradient, in order to study the inward spreading of edge turbulence toward the core plasma. Due to such spreading, the turbulence intensity in the core region is significantly enhanced over the value obtained from the simulations of the core region only, and the precise boundary of the edge region is blurred. Even when the core gradient is within the Dimits shift regime (i.e., dominated by self-generated zonal flows which reduce the transport to a negligible value), a significant level of turbulence can penetrate to the core due to spreading from the edge. The scaling of the turbulent front propagation speed is closer to the prediction from a nonlinear diffusion model than from the one based on linear toroidal coupling.
Profile-turbulence interactions, magnetohydrodynamic relaxations, and transport in tokamaks
Authors: Thyagaraja A. , Knight P. J. , de Baar M. R. , Hogeweij G. M. D. , Min E.
Published: September 2005

The dynamical behavior of the global, two-fluid, electromagnetic model of a tokamak plasma is explored under conditions corresponding to the Rijnhuizen tokamak project [A. J. H. Donné, Plasma Phys. Rep. 20, 192 (1994)] using the CUTIE code [A. Thyagaraja, Plasma Phys. Controlled Fusion 42, B255 (2000)]. Simulations of an off-axis electron-cyclotron-heated (350kW) hydrogen discharge and a purely Ohmic one over several resistive evolution times (τres≃15−20ms) are described. The results illustrate profile-turbulence interactions and the spectral transfer processes implicated in the spontaneous generation and maintenance of mesoscale zonal flows and dynamo currents. Relaxation phenomena, including off- and on-axis sawteeth and periodically repeating edge ballooning instabilities mediated by these mechanisms, are presented. The CUTIE model reproduces many observed features of the experiment qualitatively and suggests that global electromagnetic simulations may play an essential role in understanding tokamak turbulence and transport.
An examination of the validity of nonequilibrium molecular-dynamics simulation algorithms for arbitrary steady-state flows
Authors: Edwards Brian J. , Baig Chunggi , Keffer David J.
Published: September 2005

Nonlinear-response theory of nonequilibrium molecular-dynamics simulation algorithms is considered under the imposition of an arbitrary steady-state flow field. It is demonstrated that the SLLOD and DOLLS algorithms cannot be used for general flows, although the SLLOD algorithm is rigorous for planar Couette flow. Following the same procedure used to establish SLLOD as the valid algorithm for planar Couette flow [D. J. Evans and E. P. Morriss, Phys. Rev. A 30, 1528 (1984)], it is demonstrated that the p-SLLOD algorithm is valid for arbitrary flows and produces the correct nonlinear response of the viscous pressure tensor.
Nanomechanics of silicon surfaces with atomic force microscopy: An insight to the first stages of plastic deformation
Authors: Garcia-Manyes Sergi , Güell Aleix G. , Gorostiza Pau , Sanz Fausto
Published: September 2005

The use of stiff cantilevers with diamond tips allows us to perform nanoindentations on hard covalent materials such as silicon with atomic force microscopy. Thanks to the high sensitivity in the force measurements together with the high resolution upon imaging the surface, we can study nanomechanical properties. At this scale, the surface deforms, following a simple non-Hertzian spring model. The plastic onset can be assessed from a discontinuity in the force-distance curves. Hardness measurements with penetration depths as small as 1nm yield H=∼25GPa, thus showing a drastic increase with penetration depths below 5nm.
Determining the nucleation rate from the dimer growth probability
Authors: ter Horst Joop H. , Kashchiev Dimo
Published: September 2005

A new method is proposed for the determination of the stationary one-component nucleation rate J with the help of data for the growth probability P2 of a dimer which is the smallest cluster of the nucleating phase. The method is based on an exact formula relating J and P2, and is readily applicable to computer simulations of nucleation. Using the method, the dependence of J on the supersaturation s is determined by kinetic Monte Carlo simulations of two-dimensional (2D) nucleation of monolayers on the (100) face of Kossel crystal. The change of J over nearly 11 orders of magnitude is followed and it is found that the classical nucleation theory overestimates the simulation J values by an s-dependent factor. The 2D nucleus size evaluated via the nucleation theorem is described satisfactorily by the classical Gibbs-Thomson equation and its corrected version accounting for the spinodal limit of 2D nucleation.
Low-temperature electronic transport through macromolecules and characteristics of intramolecular electron transfer
Authors: Zimbovskaya Natalya A.
Published: September 2005

Long-distance electron transfer (ET) plays an important part in many biological processes. Also, fundamental understanding of ET processes could give grounds for designing miniaturized electronic devices. So far, experimental data on the ET mostly concern ET rates which characterize ET processes as a whole. Here, we develop a different approach which could provide more information about intrinsic characteristics of the long-range intramolecular ET. A starting point of the studies is an obvious resemblance between ET processes and electric transport through molecular wires placed between metallic contacts. Accordingly, the theory of electronic transport through molecular wires is applied to analyze characteristics of a long-range electron transfer through molecular bridges. Assuming a coherent electron tunneling to be a predominant mechanism of ET at low temperatures, it is shown that low-temperature current-voltage characteristics could exhibit a special structure, and the latter contains information concerning intrinsic features of the intramolecular ET. Using the Buttiker dephasing model within the scattering matrix formalism, we analyze the effect of dephasing on the electron transmission function and current-voltage curves.
Ferroelectric properties of sol-gel derived Ca modified PbZr0.52Ti0.48O3 films
Authors: Ezhilvalavan S. , Samper Victor D.
Published: September 2005

In this letter, we report the ferroelectric properties and leakage current characteristics of Ca modified PbZr0.52Ti0.48O3 (PCZT) films prepared by a sol-gel process. The PCZT film of thickness ∼1μm shows excellent ferroelectric properties in terms of large remnant polarization of ∼30μC∕cm2 (Ec∼200kV∕cm), high saturation polarization of about 51μC∕cm2 for an applied field of 915kV∕cm, fatigue free characteristics up to ⩾1010 switching cycles, and a low leakage current density of 5×10−8A∕cm2 at 100kV∕cm. X-ray diffraction, atomic force, and scanning electron microscope investigations indicate that PCZT films deposited on PbTiO3 layers exhibit a dense, well-crystallized microstructure having random orientations and a rather smooth surface morphology.
Multipolar excitation in triangular nanoprisms
Authors: Shuford Kevin L. , Ratner Mark A. , Schatz George C.
Published: September 2005

Theoretical studies on the optical properties of gold triangular prisms in solution are presented to determine how structural modifications affect the extinction spectrum. Well-defined trends in the particle extinction are found to depend on the triangular edge length and the prism thickness. Calculations performed on large, thin triangular prisms indicate multipolar excitation and display numerous peaks in the extinction spectrum. The dominant peaks are assigned to different in-plane modes corresponding to the lowest three orders of a multipole expansion. Vector polarization plots are presented to support the peak assignments. Altering the prisms by snipping off the points of the triangular cross section significantly blueshifts the dipole peak, but the higher-order modes are only slightly affected. Snipping off large volumes can lead to the suppression of high-order multipoles in the extinction spectrum.
F
+
OH
reactive collisions on new excited A″3 and A′3 potential-energy surfaces
Authors: Gómez-Carrasco Susana , Roncero Octavio , González-Sánchez Lola , Hernández M. Luz , Alvariño José M. , Paniagua Miguel , Aguado Alfredo
Published: September 2005

Global three-dimensional adiabatic potential-energy surfaces for the excited 2A″3 and 1A′3 triplet states of OHF are obtained to study the F(P2)+OH(Π2)→O(P3)+HF(Σ+1) reaction. Highly accurate ab initio calculations are obtained for the two excited electronic states and fitted to analytical functions with small deviations. The reaction dynamics is studied using a wave-packet treatment within a centrifugal sudden approach, which is justified by the linear transition state of the two electronic states studied. The reaction efficiency presents a marked preference for perpendicular orientation of the initial relative velocity vector and the angular momentum of the OH reagent, consistent in the body-fixed frame used with an initial collinear geometry which facilitates the access to the transition state. It is also found that the reaction cross section presents a rather high threshold so that, in an adiabatic picture, the two excited triplet states do not contribute to the rate constant at room temperature. Thus, only the lowest triplet state leads to reaction under these conditions and the simulated rate constants are too low as compared with the experimental ones. Such disagreement is likely to be due to nonadiabatic transitions occurring at the conical intersections near the transition state for this reaction.
Electrostatic shocks and solitons in nonuniform dusty plasmas
Authors: Saleem H.
Published: September 2005

The Korteweg–de Vries–Burgers equation for the nonlinear dust drift wave is obtained which admits solutions in the form of solitons, monotonic shocks, and oscillatory shocks in different limits. The relevance of this investigation to laboratory and space plasmas is pointed out.
A cylindrical Davey–Stewartson equation for a modulated cylindrical wave packet
Authors: Xue Ju-Kui
Published: September 2005

The modulation of a dust-ion acoustic wave (DIAW) in dusty plasmas with the combined effects of bounded cylindrical geometry and the transverse perturbation are studied. By using the standard reductive perturbation method, a cylindrical Davey–Stewartson (CDS) equation is obtained for the first time. The modulational instability of the DIAW described by the CDS equation is investigated. A new explicit criterion for the modulational instability of the DIAW described by the CDS is obtained. It is shown that the present instability criterion is different from that obtained in a standard nonlinear Schrödinger equation (NLSE), a Davey–Stewartson equation, or a cylindrically symmetric NLSE, and a wider parameter domain for modulational instability exists.