bluuebunny/crossref_metadata_2025 huggingface dataset:
Vertically Aligned Carbon‐Nanotube Arrays Showing Schottky Behavior at Room Temperature
Authors: Jung Seung‐Ho , Jeong Soo‐Hwan , Kim Sang‐Uck , Hwang Sun‐Kyu , Lee Pyung‐Soo , Lee Kun‐Hong , Ko Ju‐Hye , Bae Eunju , Kang Donghun , Park Wanjun , Oh Hwangyou , Kim Ju‐Jin , Kim Hyungseok , Park Chan‐Gyung
Published: March 2005

Vertically aligned carbon‐nanotube (CNT) arrays were fabricated in the thin‐film anodic aluminum oxide (AAO) templates on silicon wafers utilizing a niobium (Nb) thin film as the source electrode. The average diameter of the CNTs was 25 nm, and the number density was 3×1010 cm−2. The CNT arrays synthesized at 700 °C and above exhibited Schottky behavior even at 300 K, with energy gaps between 0.2 eV and 0.3 eV. However, individual CNTs obtained by removal of the template behaved as resistors at 300 K. The CNT/Nb oxide/Nb junction is thought to be responsible for the Schottky behavior. This structure can be a useful cornerstone in the fabrication of nanotransistors operating at room temperature.
Sudden, Unexpected Death Associated with Meningioangiomatosis: Case Report
Authors: Wixom Chris , Chadwick Amy E. , Krous Henry F.
Published: March 2005

We report a case of sudden, unexpected death associated with meningioangiomatosis in a 13-year-old, previously healthy male without a history of seizures, neurologic deficits, or clinical stigmata of neurofibromatosis. There was no family history of neurofibromatosis. The postmortem examination showed a 5-cm mass involving the right posterior frontal and orbital frontal cortex that had microscopic features diagnostic of meningioangiomatosis. Because no other cause of death was found, we postulate that he likely died as a result of a seizure secondary to meningioangiomatosis.
Hox11L1 Expression by Precursors of Enteric Smooth Muscle: An Alternative Explanation for Megacecum in Hox11L1-/- Mice
Authors: Kapur Raj P. , Clarke Christine M. , Doggett Barbara , Taylor Brian E. , Baldessari Audrey , Parisi Melissa A. , Howe Douglas G.
Published: March 2005

Previous studies have focused on expression of Hox11L1 in enteric neurons as the explanation for intestinal and urinary bladder dysmotility observed in mice that do not have the transcription factor. However, Hox11L1 is also expressed transiently in endo-, meso-, and ectodermal cells of the most caudal embryo during gastrulation. We sought to more fully characterize the fates of these cells because they might help explain the pathogenesis of lethal pseudo-obstruction in Hox11L1-null mice. The Cre recombinase cDNA was introduced into the Hox11L1 locus, and expression of the “knock-in” allele was used to activate the Rosa26R, β-galactosidase reporter gene in cells with ongoing Hox11L1 transcription and their descendants. During gastrulation, Rosa26R activation was observed in progenitors of caudal somatic and visceral cells, including enteric smooth muscle. Expression in enteric neural precursors appeared much later. Analysis of endogenous Hox11L1 mRNA in aneuronal segments of large intestine that were grafted under the renal capsule indicated that the early activation of Hox11L1 in visceral mesoderm was transient and ceased before colonization of the large intestine by neural progenitors. Mice homozygous for the Cre allele died shortly after weaning, with cecal and proximal colonic distention but without overt anatomic defects that might represent maldevelopment of the visceral mesoderm. Our findings expand the range of possible functions of Hox11L1 to include activation of an as yet unknown developmental program in visceral smooth muscle and allow the possibility that intestinal dysmotility in Hox11L1-null animals may not be a primary neural disorder.
Small interfering RNA inhibits SARS‐CoV nucleocapsid gene expression in cultured cells and mouse muscles
Authors: Zhao Ping , Qin Zhao-Ling , Ke Jin-Shan , Lu Yang , Liu Min , Pan Wei , Zhao Lan-Juan , Cao Jie , Qi Zhong-Tian
Published: March 2005

SARS‐CoV is a newly identified coronavirus that causes severe acute respiratory syndrome (SARS). Currently, there is no effective method available for prophylaxis and treatment of SARS‐CoV infections. In the present study, the influence of small interfering RNA (siRNA) on SARS‐CoV nucleocapsid (N) protein expression was detected in cultured cells and mouse muscles. Four siRNA expression cassettes driven by mouse U6 promoter targeting SARS‐CoV N gene were prepared, and their inhibitory effects on expression of N and enhanced green fluorescence protein (EGFP) fusion protein were observed. A candidate siRNA was proved to down‐regulate N and EGFP expression actively in a sequence‐specific manner. The expression vector of this siRNA was constructed and confirmed to reduce N and EGFP expression efficiently in both cultured cells and adult mouse muscles. Our findings suggest that the siRNA should provide the basis for prophylaxis and therapy of SARS‐CoV infection in human.
Involvement of matrix metalloproteinase‐9 in platelet‐activating factor‐induced angiogenesis
Authors: Ko Hyun-Mi , Park Yeong-Min , Jung Bongnam , Kim Han-A , Choi Jung-Hwa , Park Sung Jun , Lee Hern-Ku , Im Suhn-Young
Published: March 2005

Platelet‐activating factor (PAF) augments angiogenesis by promoting the synthesis of various angiogenic factors, via the activation of NF‐κB. In this study, we investigated the role of the matrix metalloproteinase (MMP)‐9, in PAF‐induced angiogenesis. PAF increased mRNA expression, protein synthesis, and MMP‐9 activity in ECV304 cells, in a NF‐κB‐dependent manner. PAF increased MMP‐9 promoter activity in ECV304, which was inhibited by WEB2107, and NF‐κB inhibitors. Transfected NF‐κB subunits, p65 or/and p50, increased luciferase activity in the reporter plasmid MMP‐9, resulting in an increase not only of MMP‐9 luciferase activity, but also of mRNA expression in MMP‐9. MMP‐9 or NF‐κB inhibitors significantly inhibited PAF‐induced angiogenesis, in a dose‐dependent manner, in an in vivo mouse Matrigel implantation model. In a parallel to the Matrigel implantation study, MMP‐9 or NF‐κB inhibitors inhibited PAF‐induced sprouting of porcine pulmonary arterial endothelial cells. These data indicate that NF‐κB‐dependent MMP‐9 plays a key role in PAF‐induced angiogenesis.
PTEN expression in ovine granulosa cells increases during terminal follicular growth
Authors: Froment Pascal , Bontoux Martine , Pisselet Claudine , Monget Philippe , Dupont Joëlle
Published: March 2005

In the present paper, we have studied the expression of the Phosphatase and TENsin homolog deleted on chromosome 10 (PTEN) and its putative biological role in the sheep ovary. We found by Northern‐blot, immunohistochemistry and immunoblot that PTEN is highly expressed in granulosa cells from large differentiated follicles (LF) in comparison with small proliferating follicles (SF) (P
< 0.001), with no clear effect of follicle quality. Moreover, the PTEN lipid phosphatase activity is also higher in LF than in SF (P
< 0.01). In contrast, levels of the phosphorylated form of AKT (pAKT) are lower in LF than in SF (P
< 0.0001). IGF‐I and insulin but not FSH, LH or forskolin are able to stimulate the expression of PTEN mRNA (P
< 0.001) and protein by ovine granulosa cells after 48 h of culture in vitro. An IGF‐1 time course analysis showed that expression of PTEN protein appeared after 12 h of culture, concomitant with the fall of the pAKT levels, which peaked after 6 h of stimulation with IGF‐I. Moreover, transfection experiments showed that overexpression of PTEN in ovine granulosa cells induced a decrease and an increase in E2F and p27 promoter activity, respectively (P
< 0.05). Overall, our present data show for the first time that the expression of PTEN increases during terminal follicular growth. This increase, that might be induced by IGF‐I but not FSH, would participate in the proliferation/differentiation transition of ovine granulosa cells in differentiating follicles.
The characterization of plasma membrane Ca2+‐ATPase in rich sphingomyelin–cholesterol domains
Authors: Pang Yuhong , Zhu Hua , Wu Ping , Chen Jianwen
Published: March 2005

According to the raft hypothesis, sphingolipid–cholesterol (CHOL) microdomains are involved in numerous cellular functions. Here, we have prepared liposomes to simulate the lipid composition of rafts/caveolae using phosphatidylchone, sphingomyelin (SPM)–CHOL in vitro. Experiments of both 1,6‐diphenyl‐1,3,5‐hexatriene and merocyanine‐540 fluorescence showed that a phase transition from ld to lo can be observed clearly. In particular, we investigated the behavior of a membrane protein, plasma membrane Ca2+‐ATPase (PMCA), in lipid rafts (lo phase). Three complementary approaches to characterize the physical appearance of PMCA were employed in the present study. Tryptophan intrinsic fluorescence increase, fluorescence quenching by both acrylamid and hypocrellin B decrease, and MIANS fluorescence decrease, indicate that the conformation of PMCA embedded in lipid lo phase is more compact than in lipid ld phase. Also, our results showed that PMCA activity decreased with the increase of SPM–CHOL content, in other words, with the increase of lo phase. This suggests that the specific domains containing high SPM–CHOL concentration are not a favorable place for PMCA activity. Finally, a possible explanation about PMCA molecules concentrated in caveolae/rafts was discussed.
Sumoylation of the nucleocapsid protein of severe acute respiratory syndrome coronavirus
Authors: Li Frank Qisheng , Xiao Han , Tam James P. , Liu D.X.
Published: March 2005

Severe acute respiratory syndrome coronavirus (SARS‐CoV) encodes a highly basic nucleocapsid (N) protein of 422 amino acids. Similar to other coronavirus N proteins, SARS‐CoV N protein is predicted to be phosphorylated and may contain nuclear localization signals, serine/arginine‐rich motif, RNA binding domain and regions responsible for self‐association and homo‐oligomerization. In this study, we demonstrate that the protein is posttranslationally modified by covalent attachment to the small ubiquitin‐like modifier. The major sumoylation site was mapped to the 62lysine residue of the N protein. Further expression and characterization of wild type N protein and K62A mutant reveal that sumoylation of the N protein drastically promotes its homo‐oligomerization, and plays certain roles in the N protein‐mediated interference of host cell division. This is the first report showing that a coronavirus N protein undergoes posttranslational modification by sumoylation, and the functional implication of this modification in the formation of coronavirus ribouncleoprotein complex, virion assembly and virus–host interactions.
Nitration and oligomerization of tau induced by peroxynitrite inhibit its microtubule‐binding activity
Authors: Zhang Yong Jie , Xu Ya Fei , Chen Xiao Qian , Wang Xiao Chuan , Wang Jian-Zhi
Published: March 2005

Abnormally nitrated tau has been found recently in the neurofibrillary tangles of Alzheimer's disease (AD). However, whether and how nitration of tau is involved in AD pathology is not known. Herein, we found that in vitro incubation of peroxynitrite with recombinant tau resulted in nitration and oligomerization of tau in a dosage‐dependent manner. Moreover, the nitrated tau showed a significantly decreased binding activity to taxol‐stabilized microtubulesin in vitro. Further study demonstrated that peroxynitrite also induced tau nitration in neuroblastoma N2a cell line, and the nitrated tau was accumulated in the cells. We conclude that abnormal nitration of tau contributes to the impaired biological activity of tau in binding to the microtubules and the aggregation of tau, implying a novel mechanism responsible for the neurodegeneration seen in AD brain.
On the power-law distribution of language family sizes
Authors: WICHMANN SØREN
Published: March 2005

When the sizes of language families of the world, measured by the number of languages contained in each family, are plotted in descending order on a diagram where the x-axis represents the place of each family in the rank-order (the largest family having rank 1, the next-largest, rank 2, and so on) and the y-axis represents the number of languages in the family determining the rank-ordering, it is seen that the distribution closely approximates a curve defined by the formula y=ax−b. Such ‘power-law’ distributions are known to characterize a wide range of social, biological, and physical phenomena and are essentially of a stochastic nature. It is suggested that the apparent power-law distribution of language family sizes is of relevance when evaluating overall classifications of the world's languages, for the analysis of taxonomic structures, for developing hypotheses concerning the prehistory of the world's languages, and for modelling the future extinction of language families.
The influence of visitors on intertidal biodiversity
Authors: Pinn Eunice H. , Rodgers Michelle
Published: March 2005

The Purbeck Marine Wildlife Reserve lies within the boundary of the Dorset and East Devon World Heritage Site on the south coast. This study investigated the influence of visitors on intertidal biodiversity at Kimmeridge Bay, the only accessible part of the reserve. The assemblages present on two rock ledges were compared: Washing Ledge, which is regularly visited and utilized by people, and Yellow Ledge, which is more isolated and visited much less regularly. At each ledge, three habitat types were investigated: open rock, rockpools and the fucoid zone. Multivariate statistical analysis revealed significant differences in assemblages between ledges and among habitat types. The differences observed in the communities of the two ledges can be explained to some extent by natural ecological processes, but human impacts were also detected. The most obvious contrast associated with trampling was a reduction in the larger, branching species of algae and an increase in ephemeral and crustose species in the more heavily utilized areas.
Characterization of bacteria with carbohydrase activities from tropical ecosystems
Authors: Tirado O. , Rosado W. , Govind N.S.
Published: March 2005

Several bacteria have been isolated from different tropical ecosystems (tropical rain forest, seawater, and marine sediments) from the island of Puerto Rico. These microorganisms were screened for carbohydrase activity using chromogenic substrates (amylose, pullulan, cellulose, dextran, arabinan, galactomannan, and xylan). The results indicate that 2–9% of cultured organisms show carbohydrase activity. Isolates were identified by partial sequence analysis of the polymerase chain reaction amplified small subunit rRNA gene. GenBank database comparison of the most versatile strains gave a match with Bacillus sp., Staphylococcus sp., Halomonas sp., and a gamma proteobacterium. Growth curves indicate that all strains assayed can grow as well in at least one complex carbohydrate as in glucose. A high β-xylosidase activity was detected in the Bacillus sp. strain crude enzyme preparation and this activity seems to be almost entirely cell associated. Our results show that tropical environments can be potentially good sources of bacteria with novel carbohydrases.
Eudendrium klausi (Cnidaria, Hydrozoa), a new species of hydroid from Belize
Authors: Puce Stefania , Cerrano Carlo , Marques Antonio C. , Bavestrello Giorgio
Published: March 2005

A new species of the cosmopolitan genus Eudendrium, E. klausi, is described from Carrie Bow Cay, Belize. The species is characterized by a small colony with an intense blue colour, polyps armoured with large microbasic euryteles scattered on the hydranth body, hypostome, and female spadix; female gonophores on normal hydranths with a reduced number of tentacles. The new species is compared to other Eudendrium with similar cnidome, and other Caribbean species, including those described by Allman (1877). Among the latter, E. gracile, E. laxum, E. attenuatum, and E. tenellum (sensu Allman) are considered as species inquirenda due to the lack or the unsuitability of the type materials and the inconclusive original descriptions. Eudendrium exiguum, E. eximium, and E. fruticosum were also studied and demonstrated to be different from E. klausi sp. nov.
An enriched Chaetopterus tube mat biotope in the eastern English Channel
Authors: Rees E.I.S , Bergmann M. , Galanidi M. , Hinz H. , Shucksmith R , Kaiser M.J.
Published: March 2005

Patches of a very dense tube mat biotope were found during fish habitat studies in the eastern English Channel. At three locations in the lows between linear sand banks off the French coast an un-described small Chaetopterus sp. occurred with small Lanice conchilega as an enriched sediment stabilizing biotope. This biotope was distinct though having similarities to other tide swept sub-tidal biotopes dominated by L. conchilega. Using cameras and side-scan sonar it was seen to overlay heterogeneous cobbles and shell hash with intermittent rippled sand veneer. The patchiness of this enriching biogenic feature contributed to the variability in trawl catches of fish.
Amphipod biodiversity of shallow water in the Taranto seas (north-western Ionian Sea)
Authors: Prato E. , Biandolino F.
Published: March 2005

This study was carried out to determine the amphipod fauna in Mar Piccolo, Mar Grande and the Gulf of Taranto. Material in this study was obtained from 96 stations at different depths (maximum depth: −50 m) using various methods depending on the substrata. A total of 65 species was determined and 25 species are new records in the seas of Taranto. Microdeutopus gryllotalpa, Ericthonius brasiliensis, Monocorophium insidiosum, Elasmopus rapax, Gammarus aequicauda, Gammarus insensibilis, Leucothoe spinicarpa, Lysianassa costae and Pseudoprotella phasma were the dominant species and have been found in all areas considered. The comparison of the data shows that the area examined presents a high difference regarding biocenotic index. The highest number of species was collected in the Gulf with 1944 individuals, belonging to 58 species and 19 families, followed by Mar Grande with 1448 individuals belonging to 36 species and 11 families; finally Mar Piccolo with 698 individuals, 12 species and 6 families, in the First Inlet and 546 individuals, 18 species and 6 families, in the Second Inlet.
The bivalve species of the Dardanelles
Authors: Palaz Mustafa , Berber Selcuk
Published: March 2005

The bivalvia species of the Dardanelles were investigated at the upper infralittoral zone, by diving and dredge. Various species belonging to 14 families were identified in the Dardanelles. The families are as follows: Mytilidae, Ostreidae, Cardiidae, Pimidae, Solenidae, Pectinidae, Arcidae, Nuculidae, Veneridae, Donacidae, Tellinidae, Anomidae, Scrobiculariidae and Gastrochaenidae.
Recent foundation of Mexican populations of pearl oysters (Pteria sterna) revealed by lack of genetic variation on two mitochondrial genes
Authors: Arnaud-Haond S. , Blanc F. , Bonhomme F. , Monteforte M.
Published: March 2005

The rainbow pearl oyster Pteria sterna is distributed along the Mexican Pacific coasts and Gulf of Baja California, where it represents a great economic potential. Five sampled populations collected in Baja California were used to screen two mitochondrial DNA genes that have proven useful in population genetics studies of several other bivalve species. The lack of polymorphism detected in these samples suggests a recent event of very low population size, most likely a founder event, which is congruent with the absence of P. sterna in the fossil records in Baja California.
The diet and trophic ecology of anglerfish Lophius piscatorius at the Shetland Islands, UK
Authors: Laurenson C.H. , Priede I.G.
Published: March 2005

The diet of anglerfish (Lophius piscatorius), based on the analysis of stomach contents, was investigated in the Shetland Islands. Samples were obtained during trawling for sandeel (Ammodytidae species) and demersal trawling when mainly whitefish (gadoids) are targeted. This allowed the diets of samples collected from different areas and at different times to be compared. The diets in different length groups were also compared and niche breadth investigated.

A wide range of prey types, mainly fish, were recorded but the main prey was Norway pout (Trisopterus esmarkii) and lesser sandeel (Ammodytes marinus). Diet composition varied seasonally. In samples collected during whitefish trawling the occurrence of empty stomachs decreased from the first to the third quarters and generally increased with increasing anglerfish size. Empty stomachs occurred less frequently in samples collected from areas where sandeel fishing occurred compared to areas where whitefish trawling occurred.
The use of stomach fullness and colour indices to assess Sardina pilchardus feeding
Authors: Cunha Maria Emília , Garrido Susana , Pissarra Joaquim
Published: March 2005

Scales for stomach fullness and colour were developed and calibrated in order to provide an easy and reliable way to determine feeding intensity and food quality in sardines. The categories of the fullness scale reproduce the amount of food intake as indicated by the weight of the stomachs. The levels of the colour scale reflect the type of plankton eaten as shown by concentration of a-type phaeopigments and prey analysis of the stomach contents. Individuals of a wide length range were used in this study, leading us to suggest that these indices can be applied to the entire juvenile and adult sardine population. The use of the colour and fullness scales provides a rapid and efficient means of characterizing sardine feeding. Based on the colour and fullness categories of the stomachs the majority of stomachs were almost empty or at most half-full and the diet was composed of different proportions of phyto- and zooplankton items. As indicated by the prey analyses of the contents the most important constituent of the diet, in volume, were zooplankton prey.
Long‐term sediment mobilization at a sandy inner shelf site, LEO‐15
Authors: Styles Richard , Glenn Scott M.
Published: March 2005

Nearly 2 years of wave and current observations are used to drive a calibrated bottom boundary layer model to examine sediment transport at the Long‐term Ecosystem Observatory (LEO‐15) located off of the southern coast of New Jersey. The multiyear record is of sufficient resolution to categorize sediment mobilization characteristics such as storm duration, frequency of occurrence, seasonal trends, and modes of transport at this shallow water sandy site. A total of 51 sediment transport events are identified within the 2 year timeframe. Thirty‐two are categorized as winter events, and wintertime sediment transport constitutes 63% of the total for the 2 year period. In nearly all cases, bed load transport dominates the suspended load. The majority of the bed load transport is onshore due to wave asymmetries that lead to higher orbital velocities during the forward half of the wave cycle. For the remainder of events a bimodal wave spectrum is suspected to reverse the orbital velocity skewness leading to offshore transport. Suspended sediment transport is primarily directed alongshore toward the southwest, consistent with current patterns during northeasters. By including bed load transport, the net sediment transport for the 2 year period is directed primarily onshore and slightly alongshore toward the southwest.
Solar, interplanetary, and magnetospheric parameters for the radiation belt energetic electron flux
Authors: Vassiliadis D. , Fung S. F. , Klimas A. J.
Published: March 2005

In developing models of the radiation belt energetic electron flux, it is important to include the states of the interplanetary medium and the magnetosphere, as well as the solar activity. In this study we choose the log flux je(t;L;E) at 2–6 MeV, as measured by the Proton‐Electron Telescope (PET) on SAMPEX in the period 1993–2002, as a representative flux variable and evaluate the usefulness of 17 interplanetary and magnetospheric (IP/MS) parameters in its specification. The reference parameter is the solar wind velocity, chosen because of its known high geoeffectiveness. We use finite impulse response filters to represent the effective coupling of the individual parameters to the log flux. We measure the temporal and spatial scales of the coupling using the impulse response function and the input's geoeffectiveness using the data‐model correlation. The correlation profile as a function of L is complex, and we identify its peaks in reference to the radial regions P0 (L = 3.1–4.0, inner edge of the outer belt), P1 (4.1–7.5, main outer belt), and P2 (>7.5, quasi‐trapped population), whose boundaries are determined from a radial correlative analysis (Vassiliadis et al., 2003b). Using the profiles, we classify the IP/MS parameters in four categories: (1) For the solar wind velocity and pressure the correlation is high and largely independent of L across P0 and P1, reaching its maximum in L = 4.8–6.1, or the central part of P1. (2) The IMF BSouth component and related IP/MS parameters have a bimodal correlation function, with peaks in region P0 (L = 3.0–4.1) and the geosynchronous orbit region within P1. (3) The IMF BNorth and four other interplanetary or solar irradiance parameters have a minimum correlation in P1, while the highest correlation is in the slot–outer belt boundary (L = 2.5). (4) Finally, the solar wind density has a unique correlation profile, which is anticorrelated with that of the solar wind velocity for certain L shells. We verify this classification using more complex filtering methods as well as standard correlation analysis. The categories correspond to four types of solar‐terrestrial interactions, namely, viscous interaction, magnetic reconnection, effects of ionospheric heating, and effects of high solar wind density. The response to these interactions produces the observed inner magnetospheric coherence. In each category the L dependence of the correlation profile helps explain why geoeffective solar wind structures are followed by electron acceleration in some L ranges but not in others.
Highly time‐resolved organic and elemental carbon measurements at the Baltimore Supersite in 2002
Authors: Park Seung Shik , Harrison David , Pancras J. Patrick , Ondov John M.
Published: March 2005

Organic carbon (OC) and elemental carbon (EC) in fine particles (PM2.5) were measured at the Baltimore Supersite at Ponca Street for 9.5 months in 2002 using a Sunset Laboratory carbon analyzer with 1‐hour time resolution. Monthly EC and CO diurnal averages were characterized by pronounced peaks in the early morning commute hours. OC concentration profiles were similar to CO and EC during the morning and evening rush hours, except when high ozone episodes occurred, i.e., generally in summer. Primary and secondary OC contributions were estimated during ozone episodes exceeding 100 ppb (1‐hour average). The largest 1‐hour ozone concentrations for the entire study period occurred between 11 and 13 August, during which secondary OC contributed, on average, ∼60% of the hourly OC concentrations and a maximum of 82%. Additionally, the annual EC emission rate is estimated for Maryland using published CO emission inventory data and a mean EC/CO ratio (0.0023 ± 0.0008) derived by regressing selected EC and CO measurements for each of the 9.5 months. The result, 2.31 ± 0.80 Gg EC yr−1, is similar to the estimate (2.95 Gg EC yr−1), determined on the basis of the PM2.5 emission inventory for Maryland and the mean EC abundance in PM2.5 measured with a U.S. Environmental Protection Agency speciation monitor in 2002. Finally, the Baltimore Supersite and much of the northeastern United States experienced severe smoke fumigation in early July 2002 owing to uncontrolled forest fires in Quebec, during which time, CO, EC, and OC were predominately associated with the Canadian smoke. During this episode, EC emissions are estimated to be 4.75 Gg EC from Canadian Quebec natural fires in July, and an annual release rate of 9.94 Gg EC yr−1 is estimated for all Canadian boreal forest fires.
Simulation of the mineral dust emission frequencies from desert areas of China and Mongolia using an aerodynamic roughness length map derived from the POLDER/ADEOS 1 surface products
Authors: Laurent B. , Marticorena B. , Bergametti G. , Chazette P. , Maignan F. , Schmechtig C.
Published: March 2005

To determine the location of the potential dust source regions and to evaluate the dust emission frequencies over the arid and semiarid areas of China and Mongolia (35.5°N–47°N; 73°E–125°E), we established a map of Z0 from the composition of protrusion coefficient (PC) derived from the POLDER‐1 bidirectional reflectance distribution function (BRDF). Using a ° × ° resolution Z0 data set, we derived a map of the 10‐m erosion threshold wind velocity for the Chinese and Mongolian deserts. The retrieved erosion thresholds range from 7 m s−1 in the sandy deserts (Taklimakan, Badain Jaran, and Tengger deserts) to up to 20 m s−1 in the Gobi desert. They are comparable to the minimum wind velocity measured in meteorological stations during dust storms in the Taklimakan (6–8 m s−1) and in the Gobi desert (11–20 m s−1). These erosion thresholds were combined with surface wind fields, soil moisture, and snow cover to simulate the dust emission frequencies of the eastern Asian deserts over 3 years (1997–1999). The simulations point out the Taklimakan desert and the deserts of northern China as the most frequent sources of dust emissions. The simulated seasonal cycle is characterized by a maximum in late spring and a minimum in late autumn and winter. The comparison with climatologic studies of dust storms derived from synoptic observations confirms the importance of these two source areas and the reliability of the simulated seasonal cycle. It reveals an underestimation of the dust emission frequency in the Gobi desert, because of a low frequency of high wind velocities. Our results also suggest that soil moisture and snow cover are not the main factors controlling the seasonal cycle or the interannual variability of the dust emission frequencies. We finally compared the simulated dust event frequencies to occurrences of Total Ozone Mapping Spectrometer (TOMS) Absorbing Aerosol Index (AAI) higher than 0.7 over the Taklimakan desert, where mineral dust is expected to be the dominant absorbing aerosol. A very good agreement is obtained between the simulated frequencies and the TOMS AAI frequencies on monthly and seasonal timescales.
Effects of vegetation on braided stream pattern and dynamics
Authors: Coulthard Tom J.
Published: March 2005

Investigations using a 16 m by 2 m recirculating experimental flume model of an ephemeral braided river indicate that the presence of large and erosion‐resistant plants within the channel (e.g., trees or shrubs) can have a significant impact on channel pattern and planform dynamics. Simulations show that these plants have two effects. First, they act as obstructions, in some cases forcing the flow to divide. This flow separation can allow the deposition of a small island immediately in the lee of the plant splitting the channel. The net result is a substantial increase in the number of channels and, correspondingly, the braid index. This is in direct contrast to previous studies, where increased levels of vegetation in perennial streams have decreased the braid index. Second, the plants stabilize braid bars and can form relatively stable islands in their lee, significantly reducing the longitudinal migration of islands typically associated with braided rivers.
Assessment of the predictive capabilities of stochastic theories in a three‐dimensional laboratory test aquifer: Effective hydraulic conductivity and temporal moments of breakthrough curves
Authors: Fernàndez‐Garcia Daniel , Rajaram Harihar , Illangasekare Tissa H.
Published: March 2005

Conservative and sorptive tracer experiments were conducted in a highly heterogeneous (σlnK2 = 1.79) and anisotropic (λH/λV = 3.52) three‐dimensional test aquifer under well‐controlled laboratory conditions to evaluate the effective conductivity and temporal moments predicted by stochastic theories. The spatial distribution of lnK in the test aquifer conformed to a statistically homogeneous system, thus allowing evaluation of results from stochastic theories for stationary random fields. Effective hydraulic conductivity Keff in the mean flow direction for the test aquifer was compared with different stochastic theoretical expressions. Breakthrough curves (BTCs) at individual deep‐penetrating observation wells and averaged breakthrough curves at control planes were examined. The mean arrival time and the travel time variance estimated using averaged BTCs from many observation wells at the same control plane for bromide and lithium were slightly overestimated by stochastic theories, yet most of the experimental data ranged within the confidence interval rendered by the uncertainty in the statistical properties of the test aquifer. A highlight of our experimental approach is that the continuous sampling procedure also permitted the evaluation of higher‐order temporal moments that were analyzed to study the asymmetry and peakedness of BTCs by means of the coefficients of skewness and kurtosis, respectively. Small‐perturbation analytical solutions for the coefficient of skewness and kurtosis were provided. It is seen that although stochastic theories based upon small perturbations provide reasonably good estimates of the coefficients of skewness and kurtosis associated with averaged BTCs at control planes, in general, they can largely underestimate the peakedness and tailing of BTCs observed at individual deep‐penetrating observation wells.
Corrections to scaling and crossover from good- to θ-solvent regimes of interacting polymers
Authors: Pelissetto Andrea , Hansen Jean-Pierre
Published: March 2005

We exploit known properties of universal ratios, involving the radius of gyration Rg, the second and third virial coefficients B2 and B3, and the effective pair potential between the centers of mass of self-avoiding polymer chains with nearest-neighbor attraction, as well as Monte Carlo simulations, to investigate the crossover from good- to θ-solvent regimes of polymers of finite length L. The scaling limit and finite-L corrections to scaling are investigated in the good-solvent case and close to the θ temperature. Detailed interpolation formulas are derived from Monte Carlo data and results for the Edwards two-parameter model, providing estimates of universal ratios as functions of the observable ratio A2=B2∕Rg3 over the whole temperature range, from the θ point to the good-solvent regime. The convergence with L(L⩽8000) is found to be satisfactory under good-solvent conditions, but longer chains would be required to match theoretical predictions near the θ point, due to logarithmic corrections. A quantitative estimate of the universal ratio A3=B3∕Rg6 as a function of temperature shows that the third virial coefficient remains positive throughout, and goes through a pronounced minimum at the θ temperature, which goes to zero as 1∕lnL in the scaling limit.
Effects of KrF excimer laser irradiation on surface work function of indium-tin-oxide
Authors: Lin Yow-Jon , Chen Yao-Ming , Wang Yung-Chi
Published: March 2005

In this study, the effects of a KrF excimer laser irradiation on the surface work function (SWF) of indium-tin-oxide (ITO) have been investigated. From the observed x-ray photoelectron spectroscopy results, optical transmittance measurements, and four-point probe measurements, it is suggested that the surface chemical changes, the reduction of the carrier concentration, and an increase in the sheet resistance had strong effects on the SWF of ITO. We find that the (O2)2− occupation of oxygen vacancies (VO2+) near the ITO surface after laser irradiation induced a peroxidic ITO surface, increasing the SWF.
Capillary waves in a colloid-polymer interface
Authors: Vink R. L. C. , Horbach J. , Binder K.
Published: March 2005

The structure and the statistical fluctuations of interfaces between coexisting phases in the Asakura–Oosawa model [J. Chem. Phys. 22, 1255 (1954)] for a colloid-polymer mixture are analyzed by extensive Monte Carlo simulations. We make use of a recently developed grand canonical cluster move with an additional constraint stabilizing the existence of two interfaces in the (rectangular) box that is simulated. Choosing very large systems, of size L×L×D with L=60 and D=120, measured in units of the colloid radius, the spectrum of capillary wave-type interfacial excitations is analyzed in detail. The local position of the interface is defined in terms of a (local) Gibbs surface concept. For small wave vectors capillary wave theory is verified quantitatively, while for larger wave vectors pronounced deviations show up. When one analyzes the data in terms of the concept of a wave vector–dependent interfacial tension, a monotonous decrease of this quantity with increasing wave vector is found. Limitations of our analysis are critically discussed.
Electrically switchable third-harmonic generation in photonic crystals
Authors: Markowicz P. P. , Tiryaki H. , Prasad P. N. , Tondiglia V. P. , Natarajan L. V. , Bunning T. J. , Haus J. W.
Published: March 2005

We demonstrate electrically switchable third-harmonic generation in low refractive index contrast one-dimensional photonic crystals pumped by a near-infrared laser beam. A dramatic enhancement of the third-harmonic signal is observed on the short wavelength side of the photonic crystal stop band. The enhancement of the third-harmonic generation disappears when an electric field is applied, revealing the electrical switchability of the third-harmonic generation. The observed phenomenon of enhancement is explained theoretically with a coupled-mode model. We also show that up to a modulation frequency of 10 kHz the switching properties are supported in the photonic crystal.
A new lattice-based theory for hydrogen-bonding liquids in uniform electric fields
Authors: Suresh S. J.
Published: March 2005

We propose a new lattice-based, mean-field theory for predicting alignment of molecular dipoles and hydrogen bonds in liquids subject to uniform electric fields. The theory is presently restricted to liquids whose molecules possess one (proton) donor and one acceptor sites each, and wherein the H-bond axis is collinear with the dipole moments of the bonded molecules. The final expressions for hydrogen bond stoichiometry and polarization are free of lattice parameters, are interpretable using simple phenomenological arguments, and reduce to known limiting forms. The theory is applied to understand the internal structure of hydrogen cyanide in the liquid state at different electric fields.
Targeted molecular dynamics of an open-state KcsA channel
Authors: Compoint Mylène , Picaud Fabien , Ramseyer Christophe , Girardet Claude
Published: March 2005

Pore opening of KcsA channel is studied using targeted molecular dynamics simulations. Conformational changes of the protein are determined, starting from the crystallized refined 2.0Å structure (pdb 1K4C) determined in x-ray experiments and arriving to the open-state structure constructed on the basis of electron paramagnetic resonance spectroscopic data (pdb 1JQ1). Our results corroborate the essential role played by the terminal residues located on the transmembrane helices M2 which were not taken into account at that time. The aperture mechanism of the channel appears to be ziplike. A small constraint (≈5×10−2kcalmol−1Å−2 per Cα) applied to the terminal residues located on the intracellular side is sufficient to initialize the pore opening at the innermost part of the gate, but additional constraint must be applied to definitely complete the pore aperture. The open structure is proved to be a metastable state since releasing the constraint leads to another relaxed open conformation which seems to reach stability.
Uniform-diameter, aligned carbon nanotubes from microwave plasma-enhanced chemical-vapor deposition
Authors: Wong W. K. , Lee C. S. , Lee S. T.
Published: March 2005

Well-aligned multiwalled carbon nanotubes (CNTs) were grown by microwave plasma-enhanced chemical-vapor deposition using N2 as the carrier gas and CH4 as the carbon source. Thin iron films with different thicknesses (0.5–5 nm) on silicon substrates acted as catalysts. Atomic force microscopy was used to investigate the relationship between the iron film thickness and the size of the iron clusters formed after the plasma treatment. Scanning and transmission electron microscopies were utilized to study the morphology, structure, and diameter of the as-grown CNTs. With the iron film thickness of 0.5 nm, the CNTs showed a remarkable structural uniformity in terms of diameter (standard deviation was 11.4% of the average diameter). Field-emission measurements revealed the turn-on field (at a current density of 10μA∕cm2) and threshold field (at a current density of 10mA∕cm2) to be 5–8 and 6–11.5V∕μm, respectively.
Photostimulated electron detrapping and the two-state model for electron transport in nonpolar liquids
Authors: Shkrob Ilya A. , Sauer Myran C.
Published: March 2005

In common nonpolar liquids, such as saturated hydrocarbons, there is a dynamic equilibrium between trapped (localized) and quasifree (extended) states of the excess electron (the two-state model). Using time-resolved dc conductivity, the effect of 1064 nm laser photoexcitation of trapped electrons on the charge transport has been observed in liquid n-hexane and methylcyclohexane. The light promotes the electron from the trap into the conduction band of the liquid. From the analysis of the two-pulse, two-color photoconductivity data, the residence time of the electrons in traps has been estimated as ca. 8.3 ps for n-hexane and ca. 13 ps for methylcyclohexane (at 295 K). The rate of detrapping decreases at lower temperature with an activation energy of ca. 200 meV (280–320 K); the lifetime-mobility product for quasifree electrons scales linearly with the temperature. We suggest that the properties of trapped electrons in hydrocarbon liquids can be well accounted for using the simple spherical cavity model. The estimated localization time of the quasifree electron is 20–50 fs; both time estimates are in agreement with the “quasiballistic” model. This localization time is significantly lower than the value of 310±100fs obtained using time-domain terahertz (THz) spectroscopy for the same system [E. Knoesel, M. Bonn, J. Shan, F. Wang, and T. F. Heinz, J. Chem. Phys. 121, 394 (2004)]. We suggest that the THz signal originates from the oscillations of electron bubbles rather than the free-electron plasma; vibrations of these bubbles may be responsible for the deviations from the Drude behavior observed below 0.4 THz. Various implications of these results are discussed.
Exciton states in wurtzite InGaN strained coupled quantum dots: Effects of piezoelectricity and spontaneous polarization
Authors: Shi Jun-jie , Xia Cong-xin , Wei Shu-yi , Liu Zi-xin
Published: March 2005

Within the framework of the effective-mass approximation, exciton states confined in wurtzite InxGa1−xN∕GaN strained coupled quantum dots (QDs) are investigated by means of a variational approach, including three-dimensional confinement of the electrons and holes in the QDs and strong built-in electric field effects caused by the piezoelectricity and spontaneous polarization. The relationship between exciton states and structural parameters of coupled QDs is studied in detail. We find that the strong built-in electric field in the InxGa1−xN∕GaN strained coupled QDs gives rise to a marked reduction of the effective band gap of InxGa1−xN QDs and leads to a remarkable increasing of the emission wavelengths. Both the sizes and alloy fluctuations of QDs have a significant influence on the exciton states and interband optical transitions in coupled QDs. Moreover, the barrier thickness between the two coupled InxGa1−xN QDs has a considerable influence on the exciton states and optical properties. When the barrier thickness is increased, the exciton binding energy is reduced, the emission wavelength is increased, and the electron-hole recombination rate is obviously reduced. Our theoretical results are in good agreement with the experimental measurements.
Structure of spin-split evanescent states in the fundamental gap of zinc-blende-type semiconductors
Authors: Richard Soline , Drouhin Henri-Jean , Rougemaille Nicolas , Fishman Guy
Published: March 2005

We calculate evanescent waves in GaAs throughout the forbidden band gap, taking into account both the absence of inversion symmetry and the spin-orbit coupling. In this case, the energy bands are spin split. We find that the evanescent wave functions only exist in limited energy and wave-vector domains. We show that no evanescent state associated with a purely imaginary wave vector exists in some simple directions such as [110], which has implications concerning the tunneling mechanism itself. Finally, we show that a GaAs tunnel barrier can be used as a spin injector in solid-state devices.
Ultrathin epitaxial Al2O3 films grown on Nb(110)∕sapphire(0001) investigated by tunneling spectroscopy and microscopy
Authors: Dietrich Ch. , Koslowski B. , Ziemann P.
Published: March 2005

Structural as well as electronic properties of ultrathin epitaxial Al2O3 films prepared on Nb(110)∕sapphire(0001) were analyzed in situ by applying scanning tunneling microscopy (STM) and spectroscopy as well as ultraviolet photoelectron spectroscopy, cathode luminescence, and low-energy electron diffraction. According to these experiments, the niobium base film is protected from oxidation, while the ultrathin Al film deposited onto the Nb is fully oxidized and (0001)-oriented with a very smooth surface. The STM-imaged topography of the oxide films in most cases reflects monatomic steps of the underlying Nb(110) film. In some cases (10% of all samples with low tunneling barriers) additional ∼0.4-nm-high steps are observed characteristic of monatomic Al2O3 steps. Furthermore, for growing tunneling voltages (>1V), the STM-imaged topographies reveal an increasing density of small hillocks, which are attributed to localized defect states such as oxygen vacancies still present within the oxide layer.
Magnetodynamics of a multicomponent (dusty) plasma. I. Rotation waves near low-frequency cutoff in a homogeneous medium
Authors: Ganguli Gurudas , Rudakov Leonid
Published: March 2005

By considering one of the species of a two-ion species plasma to be massive charged dust particles, the origin of the low-frequency cutoff in a multispecies plasma is found to be a fluid rotation of the light component with a characteristic frequency, Ωr=(ZnH∕ne)ΩL, where nH and ne are densities of the heavy component and electrons, respectively, Z is the charge state of the heavy component, and ΩL is the light ion cyclotron frequency. A fluid resonance at ω=Ωr modifies the properties of plasma oscillations in the vicinity of the cutoff and gives rise to the rotation waves in a manner similar to the cyclotron waves. The presence of a heavy component leads to the nonlinear Schrödinger equation for the system. The nonlinear dynamics of such a system consists of a combination of strong and weak turbulence with strong turbulence dominating in the long wavelength and the weak turbulence dominating in the short wavelength.
Consideration of magnetic field fluctuation measurements in torus plasma with a heavy ion beam probe
Authors: Shimizu A. , Fujisawa A. , Ohshima S. , Nakano H.
Published: March 2005

The article proposes a method of magnetic fluctuation measurement using a heavy ion beam probe (HIBP) in an axisymmetric torus configuration. The method is based on the detection of the toroidal position (not velocity) of the secondary beam in the analyzer. However, the method needs careful consideration with respect to path integral fluctuations along the probing beam orbit to evaluate local magnetic fluctuation, similarly to density fluctuation measurements with a HIBP. Here, we present an analytic formula to estimate and calculate the path integral effects for different fluctuation patterns in the profile, the correlation length, the radial wavelength, and the poloidal mode number. As a result, it is found that a large distance between the plasma and the detector lessens the importance of the path integral effect, and that local fluctuation of the magnetic field can be properly detected with a HIBP.