bluuebunny/crossref_metadata_2025 huggingface dataset:
Background errors in a global wave model determined from altimeter data
Authors: Greenslade Diana J. M. , Young Ian R.
Published: September 2004

One of the main limitations to current wave data assimilation systems is the lack of an accurate representation of the structure of the background errors. One method that may be used to determine background errors is the observational method of Hollingsworth and Lönnberg [1986]. This method considers correlations of the differences between observations and the background. For the case of Significant Wave Height (SWH), potential observations come from satellite altimeters. In this paper, correlations of the differences between modeled SWH and bias‐corrected ERS‐2 data are calculated. The irregular sampling pattern of the altimeter is accounted for by adjusting the correlation length scales according to latitude and the calculated length scale. The results show that the length scale of the background errors varies significantly over the globe, with the largest scales at low latitudes and shortest scales at high latitudes. Very little seasonal or year‐to‐year variability in the correlation length scales is detected. Conversely, the magnitude of the background error variance is found to have considerable seasonal and year‐to‐year variability. By separating the altimeter ground tracks into ascending and descending tracks, it is possible to examine, to a limited extent, whether any anisotropy exists in the background errors.
Long‐term trends in atmospheric concentrations of sulfate, total sulfur, and trace elements in the northeastern United States
Authors: Husain Liaquat , Parekh Pravin P. , Dutkiewicz Vincent A. , Khan Adil R. , Yang Karl , Swami Kamal
Published: September 2004

Concentrations of K, Sc, Mn, Fe, Zn, As, Se, Sb, Hg, and Pb were determined in quarterly composites of daily aerosol samples collected at Mayville, and 530 km downwind at Whiteface Mountain (1.5 km altitude), New York, for ∼20 years. SO4 concentrations [SO4] were determined in individual daily samples. Continuous hourly SO2 data are also available for much of the period. [SO4] at Mayville were twice that at Whiteface Mountain, and total S (S as SO2 + SO4) burden was fourfold higher at Mayville. From 1979 through 2002, [SO4] decreased by 59% at Whiteface Mountain, and at Mayville the decrease was 30% from 1984 to 2002. From 1979 to 2002, SO2 emissions in eight states upwind of and contiguous with New York State (Ohio, Pennsylvania, Indiana, Illinois, Wisconsin, Kentucky, West Virginia, and Ontario, Canada) decreased by 49%. A linear relationship was observed between atmospheric [SO4] and [total S] burden at the two sites with the cumulative SO2 emissions. These observations suggest that any further reductions in SO2 emissions would result in a proportional decrease in [SO4] and [total S] across New York State and possibly across the northeastern United States. The data at Whiteface Mountain suggest that beginning in 1997, the decrease in [SO4] and [total S], relative to SO2 emissions, may be faster than the earlier period. Like [SO4] and [total S], the trace element concentrations were twofold to fivefold higher at Mayville than at Whiteface Mountain. The concentrations at both sites showed an unmistakable decrease over time. The largest decreases were observed for Hg (16%/year at Whiteface Mountain and 10%/year at Mayville) and Pb (14%/year at Whiteface Mountain and 10%/year at Mayville). The remaining elements (except Sb), including the crustal elements K, Mn, Sc, and Fe, showed a decreases of 3–5%/year. Trends for Sb at Whiteface Mountain and for Mn at Mayville could not be accurately discerned, apparently due to some nearby emissions. Apparently, the reductions in the emissions of SO2 and particulate matter have also resulted in the decrease of atmospheric burden of trace elements and an improvement in air quality.
Sphingosine 1‐phosphate‐induced vasoconstriction is elevated in mesenteric resistance arteries from aged female rats
Authors: Hemmings D G , Xu Y , Davidge S T
Published: September 2004

Sphingosine 1‐phosphate (S1P), a bioactive lipid, signals through cell surface receptors to induce vasoconstriction and activate endothelial nitric oxide synthase (eNOS), suggesting a role for S1P in vascular tone modulation.

Using a model of aging in female rats, we investigated the vasoactivity of S1P and the roles of eNOS and estrogen replacement in modulation of that vasoactivity.

Mesenteric arteries from aged female rats were significantly more sensitive to S1P‐induced vasoconstriction than arteries from young female rats, and reached greater maximum constriction (58.2±2.98 vs 34.8±4.44%; P<0.005). Modulation of this vasoconstriction by pretreating vessels with the NOS inhibitor L‐NAME occurred only in young vessels.

Ovariectomy reduced the maximum S1P‐induced vasoconstriction observed in intact aged rats. Estrogen replacement did not appear to have an independent beneficial effect. However, estrogen replacement did restore nitric oxide modulation of S1P‐induced vasoconstriction.

Expression of the S1P1 receptor, through which eNOS can be activated, was reduced in vessels from aged rats. S1P1 receptor expression was restored in vessels from the estrogen‐replaced group.

S1P is a novel mediator of vascular tone through induction of both vasoconstriction and vasodilation. Reduced S1P1 receptor expression on aging vessels may explain reduced eNOS activity, which results in greater sensitivity to S1P‐induced vasoconstriction. Estrogen replacement in aging female rats restores both S1P1 receptor expression and NOS activity, suggesting an important role for estrogen in this novel pathway of vascular tone modulation.

British Journal of Pharmacology (2004) 143, 276–284. doi:10.1038/sj.bjp.0705752
Role of PDE4 in superoxide anion generation through p44/42MAPK regulation: a cAMP and a PKA‐independent mechanism
Authors: Jacob Claire , Szilagyi Corinne , Allen Janet M , Bertrand Claude , Lagente Vincent
Published: September 2004

We investigated the generation of reactive oxygen species (ROS) from bronchoalveolar lavage (BAL) cells of either control or LPS‐exposed rats and the effects of PDE4 inhibitors on ROS production.

The PDE4 inhibitors, rolipram and Ariflo (cilomilast, SB 207499) dose‐dependently (0.1–10 μM) inhibited fMLP‐induced superoxide anion (O2•−) production (IC50s: 0.03 and 0.55 μM, respectively) in BAL cells of Wistar rats collected 3 h after an LPS‐aerosol (200 μg ml−1, 1 h). These BAL contained 85–95% neutrophils (BAL cells enriched in neutrophils).

In contrast, BAL cells collected at the end of the challenge contained only macrophages and in these conditions, rolipram and Ariflo (0.1–10 μM) could only inhibit 25 and 45% of fMLP‐induced O2•− release, respectively.

We also observed that the inhibition of p44/42MAPK by PD98059 (1–10 μM) increased O2•− release by BAL cells enriched in neutrophils, but not by macrophages, and prevented the inhibition of O2•− production induced by PDE4 inhibitors.

Western blot analysis showed that PDE4 inhibitors strongly activated p44/42MAPK in BAL cells enriched in neutrophils but not in macrophages. And in these cells, PDE4 and p44/42MAPK were co‐immunoprecipitated by a polyclonal anti‐PDE4 antibody.

The following cell permeable‐cAMP analogues, dbcAMP (10 μM–1 mM), 8‐CPT‐cAMP (1 mM) and 8‐pMeOPT‐2′‐O‐Me‐cAMP (0.5 mM), could not reduce fMLP‐induced O2•− production and both PKA inhibitors, PKA inhibitor 14–22 amide myristoylated (50 nM–1 μM) and H‐89 (100 nM–1 μM), did not affect the decrease of O2•− release induced by PDE4 inhibitors in BAL cells enriched in neutrophils.

These data suggest that PDE4 inhibitors decreased fMLP‐induced O2•− release in BAL cells enriched in neutrophils but not in macrophages, through p44/42MAPK activation by a cAMP‐ and a PKA‐independent mechanism.

British Journal of Pharmacology (2004) 143, 257–268. doi:10.1038/sj.bjp.0705927
Marijuana and cannabinoid regulation of brain reward circuits
Authors: Lupica Carl R , Riegel Arthur C , Hoffman Alexander F
Published: September 2004

The reward circuitry of the brain consists of neurons that synaptically connect a wide variety of nuclei. Of these brain regions, the ventral tegmental area (VTA) and the nucleus accumbens (NAc) play central roles in the processing of rewarding environmental stimuli and in drug addiction. The psychoactive properties of marijuana are mediated by the active constituent, Δ9‐THC, interacting primarily with CB1 cannabinoid receptors in a large number of brain areas. However, it is the activation of these receptors located within the central brain reward circuits that is thought to play an important role in sustaining the self‐administration of marijuana in humans, and in mediating the anxiolytic and pleasurable effects of the drug. Here we describe the cellular circuitry of the VTA and the NAc, define the sites within these areas at which cannabinoids alter synaptic processes, and discuss the relevance of these actions to the regulation of reinforcement and reward. In addition, we compare the effects of Δ9‐THC with those of other commonly abused drugs on these reward circuits, and we discuss the roles that endogenous cannabinoids may play within these brain pathways, and their possible involvement in regulating ongoing brain function, independently of marijuana consumption. We conclude that, whereas Δ9‐THC alters the activity of these central reward pathways in a manner that is consistent with other abused drugs, the cellular mechanism through which this occurs is likely different, relying upon the combined regulation of several afferent pathways to the VTA.

British Journal of Pharmacology (2004) 143, 227–234. doi:10.1038/sj.bjp.0705931
Loss of endothelial KATP channel‐dependent, NO‐mediated dilation of endocardial resistance coronary arteries in pigs with left ventricular hypertrophy
Authors: Gendron Marie‐Eve , Thorin Eric , Perrault Louis P
Published: September 2004

The influence of left ventricular hypertrophy (LVH) on the endothelial function of resistance endocardial arteries is not well established. The aim of this study was to characterise the mechanisms responsible for UK‐14,304 (α2‐adrenoreceptor agonist)‐induced endothelium‐dependent dilation in pig endocardial arteries isolated from hearts with or without LVH.

LVH was induced by aortic banding 2 months before determining endothelial function. Following euthanasia, hearts were harvested and endocardial resistance arteries were isolated and pressurised to 100 mmHg in no‐flow conditions. Vessels were preconstricted with acetylcholine (ACh) or high external K+ (40 mmol l−1 KCl). Results are expressed as mean±s.e.m.

UK‐14,304 induced a maximal dilation representing 79±6% (n=8) of the maximal diameter. NO synthase (L‐NNA, 10 μmol l−1, n=7) or guanylate cyclase (ODQ, 10 μmol l−1, n=4) inhibition reduced (P<0.05) UK‐14,304‐dependent dilation to 35±6 and 18±7%, respectively. Apamin and charybdotoxin reduced (P<0.05) to 39±8% (n=4) the dilation induced by UK‐14,304. In depolarised conditions, however, this dilation was prevented (P<0.05).

UK‐14,304‐induced dilation was reduced (P<0.05) by glibenclamide (Glib, 1 μmol l−1), a KATP channel blocker, either alone (35±10%, n=5) or in combination with L‐NNA (34±9%, n=4).

In LVH, UK‐14,304‐induced maximal dilation was markedly reduced (25±4%, P<0.05) compared to control; it was insensitive to L‐NNA (21±5%) but prevented either by the combination of L‐NNA, apamin and charybdotoxin, or by 40 mmol l−1 KCl.

Activation of endothelial α2‐adrenoreceptor induces an endothelium‐dependent dilation of pig endocardial resistance arteries. This dilation is in part dependent on NO, the release of which appears to be dependent on the activation of endothelial KATP channels. This mechanism is blunted in LVH, leading to a profound reduction in UK‐14,304‐dependent dilation.

British Journal of Pharmacology (2004) 143, 285–291. doi:10.1038/sj.bjp.0705937
Effect of the statin atorvastatin on intracellular signalling by the prostacyclin receptor in vitro and in vivo
Authors: O'Meara Sarah J , Kinsella B Therese
Published: September 2004

Prostacyclin plays a central role within the vasculature. We have previously established that the prostacyclin receptor (IP) undergoes isoprenylation, a lipid modification obligate for its function. The aim of the current study was to investigate the effect of the hydroxy methyl glutaryl co‐enzyme A reductase inhibitor atorvastatin on signalling and function of the IP expressed in mammalian whole cells and in platelets isolated from patients undergoing therapeutic intervention with atorvastatin.

Initially, the effect of atorvastatin on signalling by the human (h) and mouse (m) IP overexpressed in human embryonic kidney 293 cells and the hIP endogenously expressed in human erythroleukaemic 92.1.7 cells was investigated. Atorvastatin significantly reduced IP‐mediated cAMP generation (IC50 6.6–11.1 μM) and [Ca2+]i mobilization (IC50 7.2–16.4 μM) in a concentration‐dependent manner, but had no effect on signalling by the nonisoprenylated β2 adrenergic receptor or the α or β isoforms of the human thromboxane A2 receptor (TP).

Moreover, atorvastatin significantly reduced IP‐mediated crossdesensitization of signalling by TPα (IC50 10.4 μM), but not by TPβ.

In contrast to the whole‐cell data, atorvastatin therapy did not interfere with IP‐mediated cAMP generation or IP‐induced inhibition of TP‐mediated aggregation of platelets isolated from human volunteers undergoing therapeutic intervention with atorvastatin (10–80 mg per daily dose).

In conclusion, while data generated in whole cells indicated that atorvastatin significantly impairs signalling by both the hIP and mP, the in vivo clinical data indicated that, at the administered therapeutic dose, atorvastatin does not significantly compromise IP signalling and function in humans.

British Journal of Pharmacology (2004) 143, 292–302. doi:10.1038/sj.bjp.0705947
The DNA repair helicase UvrD is essential for replication fork reversal in replication mutants
Authors: Flores Maria Jose , Bidnenko Vladimir , Michel Bénédicte
Published: September 2004

Replication forks arrested by inactivation of the main Escherichia coli DNA polymerase (polymerase III) are reversed by the annealing of newly synthesized leading‐ and lagging‐strand ends. Reversed forks are reset by the action of RecBC on the DNA double‐strand end, and in the absence of RecBC chromosomes are linearized by the Holliday junction resolvase RuvABC. We report here that the UvrD helicase is essential for RuvABC‐dependent chromosome linearization in E. coli polymerase III mutants, whereas its partners in DNA repair (UvrA/B and MutL/S) are not. We conclude that UvrD participates in replication fork reversal in E. coli.
Differential Expression of Three Purple Acid Phosphatases from Potato
Authors: Zimmermann P. , Regierer B. , Kossmann J. , Frossard E. , Amrhein N. , Bucher M.
Published: September 2004

Abstract: Three cDNAs encoding purple acid phosphatase (PAP) were cloned from potato (Solanum tuberosum L. cv. Désirée) and expression of the corresponding genes was characterised. StPAP1 encodes a low‐molecular weight PAP clustering with mammalian, cyanobacterial, and other plant PAPs. It was highly expressed in stem and root and its expression did not change in response to phosphorus (P) deprivation. StPAP2 and StPAP3 code for high‐molecular weight PAPs typical for plants. Corresponding gene expression was shown to be responsive to the level of P supply, with transcripts of StPAP2 and StPAP3 being most abundant in P‐deprived roots or both stem and roots, respectively. Root colonisation by arbuscular mycorrhizal fungi had no effect on the expression of any of the three PAP genes. StPAP1 mRNA is easily detectable along the root axis, including root hairs, but is barely detectable in root tips. In contrast, both StPAP2 and StPAP3 transcripts are abundant along the root axis, but absent in root hairs, and are most abundant in the root tip. All three PAPs described contain a predicted N‐terminal secretion signal and could play a role in extracellular P scavenging, P mobilisation from the rhizosphere, or cell wall regeneration.
Evolutionary Origin of a Preprotein Translocase in the Periplastid Membrane of Complex Plastids: a Hypothesis
Authors: Bodył A.
Published: September 2004

Abstract: Plastids with four envelope membranes have evolved from red and green algae engulfed by phagotrophic protozoans. It is assumed that the Sec translocon resides in their outermost membrane, while in the two innermost membranes the Toc‐Tic supercomplex is embedded. However, such a single Sec/single Toc‐Tic model cannot explain the passage of proteins across the second (or periplastid) membrane which represents the endosymbiont plasmalemma. One of the most recent models postulates that this membrane contains the Toc75 channel which was relocated here from the endosymbiont plastid. Unfortunately, the precursor of this protein carries a bipartite presequence, which means that its insertion into the new membrane would require relocation and/or modification of two different processing peptidases. I suggest that these obstacles can be easily bypassed by the assumption that the mitochondrial Tim23 channel was inserted into the endosymbiont plasmalemma. In contrast to Toc75, this protein has an internal, uncleavable targeting signal and its insertion into the new membrane would require neither relocation nor modification of additional proteins. Besides, such a relocated Tim23 channel could import not only plastid, but also mitochondrial proteins. I hypothesize that from the latter proteins, initially directed to the endosymbiont mitochondrion, periplastid proteins have evolved which are now targeted to the former cytosol and/or nucleus of the eukaryotic algal endosymbiont.
Microbial Populations and Activities in the Rhizoplane of Rock‐Weathering Desert Plants. I. Root Colonization and Weathering of Igneous Rocks
Authors: Puente M. E. , Bashan Y. , Li C. Y. , Lebsky V. K.
Published: September 2004

Abstract:Dense layers of bacteria and fungi in the rhizoplane of three species of cactus(Pachycereus pringlei, Stenocereus thurberi, Opuntia cholla)and a wild fig tree(Ficus palmeri)growing in rocks devoid of soil were revealed by bright‐field and fluorescence microscopy and field emission scanning electron microscopy. These desert plants are responsible for rock weathering in an ancient lava flow at La Purisima‐San Isidro and in sedimentary rock in the Sierra de La Paz, both in Baja California Sur, Mexico. The dominant bacterial groups colonizing the rhizoplane were fluorescent pseudomonads and bacilli. Seven of these bacterial species were identified by the 16S rRNA molecular method. Unidentified fungal and actimomycete species were also present. Some of the root‐colonizing microorganisms fixedin vitroN2, produced volatile and non‐volatile organic acids that subsequently reduced the pH of the rock medium in which the bacteria grew, and significantly dissolved insoluble phosphates, extrusive igneous rock, marble, and limestone. The bacteria were able to release significant amounts of useful minerals, such as P, K, Mg, Mn, Fe, Cu, and Zn from the rocks and were thermo‐tolerant, halo‐tolerant, and drought‐tolerant. The microbial community survived in the rhizoplane of cacti during the annual 10‐month dry season. This study indicates that rhizoplane bacteria on cacti roots in rock may be involved in chemical weathering in hot, subtropical deserts.
Microbial Populations and Activities in the Rhizoplane of Rock‐Weathering Desert Plants. II. Growth Promotion of Cactus Seedlings
Authors: Puente M. E. , Li C. Y. , Bashan Y.
Published: September 2004

Abstract: Four bacterial species isolated from the rhizoplane of cacti growing in bare lava rocks were assessed for growth promotion of giant cardon cactus seedlings (Pachycereus pringlei). These bacteria fixed N2, dissolved P, weathered extrusive igneous rock, marble, and limestone, and significantly mobilized useful minerals, such as P, K, Mg, Mn, Fe, Cu, and Zn in rock minerals. Cardon cactus seeds inoculated with these bacteria were able to sprout and grow normally without added nutrients for at least 12 months in pulverized extrusive igneous rock (ancient lava flows) mixed with perlite. Cacti that were not inoculated grew less vigorously and some died. The amount of useful minerals (P, K, Fe, Mg) for plant growth extracted from the pulverized lava, measured after cultivation of inoculated plants, was significant. This study shows that rhizoplane bacteria isolated from rock‐growing cacti promote growth of a cactus species, and can help supply essential minerals for a prolonged period of time.
Induction of Pathogen Resistance in Barley by Abiotic Stress
Authors: Wiese J. , Kranz T. , Schubert S.
Published: September 2004

Abstract: Enhanced resistance of barley (Hordeum vulgare L. cv. Ingrid) against barley powdery mildew (Blumeria graminis f. sp. hordei race A6) was induced by abiotic stress in a concentration‐dependent manner. The papilla‐mediated resistance was not only induced by osmotic stress, but also by proton stress. Resistance was directly correlated with increasing concentrations of various salts in the nutrient solution. Resistance induced by proton stress also depended on the stress intensity. Resistance induction occurred even at low stress intensities. Any specific ion toxicity affecting the fungal growth directly, and therefore leading to enhanced pathogen resistance, can be excluded because of the independence of resistance induction of the ion used and of the time course of sodium accumulation in the leaves. BCI‐4, a marker for benzo[1,2,3]thiadiazolecarbothioic acid S‐methyl ester (BTH)‐induced resistance was not induced by these abiotic stresses. However, resistance was induced in the same concentration‐dependent manner by the application of the stress hormone ABA to the root medium. During the relief of water stress, resistance did not decrease constantly. On the contrary, after a phase of decreasing resistance for 24 h the pathogen resistance increased again for 48 h before decreasing finally to control levels.
Sex Ratio of Some Long‐Lived Dioecious Plants in a Sand Dune Area
Authors: de Jong T. J. , van der Meijden E.
Published: September 2004

Abstract: In dioecious plants the fraction of males among flowering plants in the field (the secondary sex ratio) is the result of the fraction of males in the seeds (the primary sex ratio) and the subsequent survival and age at first reproduction of the two genders. It has been assumed that survival and age at first reproduction are the main determinants of biased secondary sex ratio but, especially for long‐lived perennials, few data are available. We address this issue for natural populations of four long‐lived perennials in a dune area. In Asparagus officinale and Bryonia dioica, the secondary sex ratio was unbiased. In Salix repens the secondary sex ratio was female‐biased (0.337). Hippophae rhamnoides populations were male‐biased; the average sex ratio of flowering plants was 0.658, while the fraction of males varied between 0.39 near the sea to 0.84 at the inland side of the dunes. The primary sex ratio was estimated by germinating seeds and growing plants under favourable conditions with minimal mortality. In S. repens the primary sex ratio in seeds was variable among mother plants and was, on average, female‐biased (0.289). This is close to the secondary sex ratio, suggesting that the female bias already originates in the seed stage. In Hippophae rhamnoides the primary sex ratio was slightly male‐biased (0.564). We argue that in this species, apart from the primary sex ratio, higher mortality and a later age at first reproduction for females contribute to the strong male bias among flowering plants in the field.
Nuclear DNA Amounts in 112 Species of Tropical Hardwoods ‐ New Estimates
Authors: Ohri D. , Bhargava A. , Chatterjee A.
Published: September 2004

Abstract: The 4C DNA values of 112 species, belonging to 37 families have a range from 0.83 pg (Bixa orellana) to 15.54 pg (Thryallis angustifolia), showing a 18.72‐fold variation. The genome size varies from 0.21 pg (Bixa orellana) to 3.32 (Thespesia populnea), with a 15.8‐fold difference. The Bombacaceae has the minimum range (1.08‐fold) of variation, while the maximum (5.0‐fold) is shown by the Fabaceae. The Boraginaceae, Lauraceae, Malpighiaceae, and Malvaceae generally have higher 4C DNA values of > 10 pg, while the Bixaceae, Caricaceae, Oxalidaceae, and Santalaceae have lower values of < 2.0 pg. These data add further to our knowledge on variation in DNA amount in tropical hardwoods.
Herbivory Differentially Affects Male and Female Reproductive Traits of Cucumis sativus
Authors: Thomson V. P. , Nicotra A. B. , Cunningham S. A.
Published: September 2004

Abstract: Herbivory is an important selection pressure in the life history of plants. Most studies use seed or fruit production as an indication of plant fitness, but the impact of herbivory on male reproductive success is usually ignored. It is possible that plants compensate for resources lost to herbivory by shifting the allocation from seed production to pollen production and export, or vice versa. This study examined the impact of herbivory by Helix aspersa on both male and female reproductive traits of a monoecious plant, Cucumis sativus. The effects of herbivory on the relative allocation to male and female flowers were assessed through measurements of the number and size of flowers of both sexes, and the amount of pollinator visitation. We performed two glasshouse experiments; the first looked at the impact of three levels of pre‐flowering herbivory, and the second looked at four levels of herbivory after the plants had started to flower. We found that herbivory during the flowering phase led to a significant increase in the number of plants without male flowers. As a consequence there was significantly less pollen export from this population, as estimated by movement of a pollen analog. The size of female flowers was reduced by severe herbivory, but there was no affect on pollen receipt by the female flowers of damaged plants. The decrease in allocation to male function after severe herbivory may be adaptive when male reproductive success is very unpredictable.
Biosystematic Studies on the Family Tofieldiaceae I. Phylogeny and Circumscription of the Family Inferred from DNA Sequences of matK and rbcL
Authors: Tamura M. N. , Fuse S. , Azuma H. , Hasebe M.
Published: September 2004

Abstract: In order to specify phylogenetic positions of the genera of Tofieldiaceae (Tofieldia, Triantha, Pleea, Harperocallis, Isidrogalvia), and to suggest reasonable circumscription of the family and genera of Tofieldiaceae, we determined DNA sequences of matK and rbcL for each genus of the family, and analyzed them phylogenetically with the 45 families and 113 genera of the monocots other than Tofieldiaceae, whose matK and rbcL sequences have already been reported. We found that Tofieldia, Triantha, Pleea, and Harperocallis form the same clade, which receives 100 % bootstrap support. This clade can be regarded as corresponding to Tofieldiaceae, and is embedded in the clade of Alismatales (98 %). On the other hand, Isidrogalvia is not included in this Tofieldiaceae clade, and positioned as sister to Narthecium (100 %), embedded in the clade of Nartheciaceae (Dioscoreales) (100 %). In the Tofieldiaceae, Pleea first diverges from the remaining three genera (100 %), and then, Harperocallis diverges from the Tofieldia‐Triantha complex (100 %). In the Tofieldia‐Triantha complex, five Tofieldia species form the same clade (100 %), and two Triantha species form another clade (100 %). Thus, Isidrogalvia should be transferred from Tofieldiaceae to Nartheciaceae. As Isidrogalvia, as well as the Nartheciaceae, have the carpels that are fully connate into a single style, Isidrogalvia fits the Nartheciaceae well with respect to carpel connation. After this transfer, the Tofieldiaceae correspond mainly to plants with almost free carpels and three styles. Pleea is better treated as an independent genus than included in Tofieldia. Triantha can be treated either as an independent genus or as congeneric with Tofieldia.
Below band gap photoreflectance transitions in epitaxial GaN
Authors: Yu Phil W. , Clark Jerry D. , Look David C. , Chen C. Q. , Yang Jinwei , Koutstis Edmundas , Khan M. Asif , Tsvertkov Denis V. , Dmitriev Vladimir A.
Published: September 2004

A photoreflectance (PR) and photoluminescence (PL) study has been performed on a Si-doped epitaxial GaN layer that contains impurity or defect related below band gap features in its PR spectrum. In the 300K PR spectrum, these features appear at energies of 3.26 and 3.33eV, respectively, but below 180K they can no longer be seen. The 3.26eV line evidently corresponds to a donor acceptor pair transition, also seen in PL. The origin of the 3.33eV line is uncertain, but may correspond to a transition involving the nitrogen vacancy.
Instrumentation for cryogenic microwave cavity resonance measurements
Authors: Tsai C. C. , Feller J. R. , Sarma Bimal K. , Ketterson J. B.
Published: September 2004

We describe instrumentation and measurement procedures for performing microwave measurements on small metallic samples at dilution refrigerator temperatures using the microwave cavity perturbation technique. The quality factor Q of the lead-plated cavity was of order of 105 at temperatures below the superconducting transition temperature of lead. Microwaves were coupled into and out of the resonator through two room-temperature positionable semirigid coaxial lines, each terminated in a small-loop antenna. We describe in detail the arrangement of the apparatus used to tune to, and lock onto, a cavity resonance and the strategy used to categorize various resonance modes. One of the main features of this microwave spectrometer is the application of the FM detection method to measure changes in both the frequency and the quality factor of the sample-loaded cavity. The procedures for converting these quantities to the real and imaginary components of the surface impedance are described. As an application of the methodology used, we present some results of measurements on the superconducting response of a heavy fermion superconductor, UBe13, which can be fitted with the Mattis–Bardeen theory.
Stability of a finite-length screw pinch revisited
Authors: Ryutov D. D. , Cohen R. H. , Pearlstein L. D.
Published: September 2004

The ideal magnetohydrodynamic stability of a cylindrical screw pinch (i.e., a current-carrying plasma column embedded into an external axial magnetic field) has been considered in the past in great detail. However, the majority of these studies pertain, in fact, to an infinitely long pinch, where the axial eigenmodes can be represented as exp(ikz). The finite length is then accounted for by assigning a specific value to k, k=2π/L, with L being the distance between the electrodes; in this way, one recovers the familiar Kruskal–Shafranov (KS) stability condition. In the present paper it is emphasized that the solution of the exp(ikz) type cannot satisfy the boundary conditions at the conducting end plates. Previous papers on this subject are reviewed. An effective technique that allows one to analytically obtain stability criteria in the long-thin approximation is developed. Even in this (“long-thin”) case substantial deviations from the KS condition are found. In the general case, a convenient representation is obtained for the Green’s functions that express perturbations both inside and outside the plasma in terms of the radial displacement of the plasma boundary. These expressions are then used in combination with the energy principle to evaluate corrections to the long-thin approximation.
Properties of MgB2 thin films with carbon doping
Authors: Pogrebnyakov A. V. , Xi X. X. , Redwing J. M. , Vaithyanathan V. , Schlom D. G. , Soukiassian A. , Mi S. B. , Jia C. L. , Giencke J. E. , Eom C. B. , Chen J. , Hu Y. F. , Cui Y. , Li Qi
Published: September 2004

We have studied structural and superconducting properties of MgB2 thin films doped with carbon during the hybrid physical-chemical vapor deposition process. A carbon-containing precursor metalorganic bis(methylcyclopentadienyl)magnesium was added to the carrier gas to achieve carbon doping. As the amount of carbon in the film increases, the resistivity increases, Tc decreases, and the upper critical field increases dramatically as compared to clean films. The self-field Jc in the carbon doped film is lower than that in the clean film, but Jc remains relatively high to much higher magnetic fields, indicating stronger pinning. Structurally, the doped films are textured with columnar nano-grains and highly resistive amorphous areas at the grain boundaries. The carbon doping approach can be used to produce MgB2 materials for high magnetic-field applications.
Defect-free InP nanowires grown in [001] direction on InP (001)
Authors: Krishnamachari U. , Borgstrom M. , Ohlsson B. J. , Panev N. , Samuelson L. , Seifert W. , Larsson M. W. , Wallenberg L. R.
Published: September 2004

We report on [001]InP nanowires grown by metalorganic vapor phase epitaxy directly on (001)InP substrates. Characterization by scanning electron microscopy and transmission electron microscopy reveals wires with nearly square cross sections and a perfect zinc-blende crystalline structure that is free of stacking faults. Photoluminescence measurements of single [001] nanowires exhibit a narrow and intense emission peak at approximately 1.4eV, whereas ⟨111⟩B grown reference wires show additional broad luminescence peaks at lower energy. The origin of this uncommon wire growth direction [001] is discussed as a means of controlled formation of [00l]-oriented nanowires on (001) substrates.
Role of hydrogen on negative bias temperature instability in HfO2-based hole channel field-effect transistors
Authors: Houssa M. , Gendt S. De , Autran J. L. , Groeseneken G. , Heyns M. M.
Published: September 2004

The impact of hydrogen on negative bias temperature instability in atomic layer deposited HfO2-based hole channel field-effect transistors is investigated. After forming gas anneal of the devices at high temperature (580°C), the saturated threshold voltage shift of the transistor is about 100mV at 125°C. The threshold voltage instability is reduced to about a factor of 2 for devices annealed in forming gas at 520°C. A detailed analysis of the experimental results suggests that the defects responsible for negative bias temperature instabilities are hydrogen-induced overcoordinated oxygen centers, due to the transport and trapping of protons in the gate dielectric stack.
Time-resolved detection of individual electrons in a quantum dot
Authors: Schleser R. , Ruh E. , Ihn T. , Ensslin K. , Driscoll D. C. , Gossard A. C.
Published: September 2004

We present measurements on a quantum dot and a nearby, capacitively coupled, quantum point contact used as a charge detector. With the dot being weakly coupled to only a single reservoir, the transfer of individual electrons onto and off the dot can be observed in real time in the current signal from the quantum point contact. From these time-dependent traces, the quantum mechanical coupling between dot and reservoir can be extracted quantitatively. A similar analysis allows the determination of the occupation probability of the dot states.
Interface velocity of laser shocked Fe/LiF targets
Authors: Huser G. , Koenig M. , Benuzzi-Mounaix A. , Henry E. , Vinci T. , Faral B. , Tomasini M. , Telaro B. , Batani D.
Published: September 2004

The interface velocity of iron partially releasing into a lithium fluoride (LiF) window has been measured using VISAR technique. Corrections to the fringe-per-velocity relationship are presented. A good agreement with hydrodynamic simulations is found at laser intensities <2×1013 W/cm2. For higher intensities, velocities appear to be lower than the numerical predictions. A strong modification of compressed LiF index of refraction behavior might explain such a discrepancy.
Dependence of oxide thickness on O2 pressure and experimental determination of Gibbs free energies of ultrathin oxide films in vacuum
Authors: Bouzidi L. , Slavin A. J.
Published: September 2004

Ultrathin oxide films grown in a vacuum are important in many industrial processes, with the values of Gibbs free energies of the gas and films determining the oxide type that grows on a surface, and its thickness. A high-stability quartz-crystal microbalance is used to provide quantitative experimental data on these free energies, for the model case of oxidation of a lead film on a gold substrate. The surface oxide, PbO, forms a single molecular layer at 10−6Torr of O2, but thickens abruptly to two layers at 1×10−4Torr, and becomes even thicker by 0.33Torr. This is explained using film free energies.
Critical effects of substrate terraces and steps morphology on the growth mode of epitaxial SrRuO3 films
Authors: Sánchez F. , Herranz G. , Infante I. C. , Fontcuberta J. , García-Cuenca M. V. , Ferrater C. , Varela M.
Published: September 2004

We report on the controlled fabrication of the arrays of self-organized fingerlike nanostructures of SrRuO3 that form on SrTiO3(001). We show that the size (width and height) of the one-dimensional nanometric units can be tuned or suppressed by using appropriate substrate vicinality θv and surface termination. Critical effects on the fingers height are observed when θv is below an angle as small as ∼0.1°. The value of θv also determines if the final two-dimensional growth is by a step flow (θv=0.5°), by layer by layer (θv=0.04°), or by coexistence of both mechanisms (θv=0.1°). The fingers are suppressed when TiO2-terminated low-miscut substrates are used, as film nucleation takes place on the terraces and then substrate steps are not active as templates for the one-dimensional structure formation. These findings shall contribute to progress toward lateral nanostructuration of complex oxide surfaces.
Three-dimensional heteroepitaxy in self-assembled BaTiO3–CoFe2O4 nanostructures
Authors: Zheng H. , Wang J. , Mohaddes-Ardabili L. , Wuttig M. , Salamanca-Riba L. , Schlom D. G. , Ramesh R.
Published: September 2004

Self-assembled BaTiO3–CoFe2O4 complex oxide nanostructures have been synthesized by pulsed laser deposition. A single ceramic target with a molar ratio of 0.62BaTiO3–0.38CoFe2O4 was used. Spinel CoFe2O4 and perovskite BaTiO3 phases spontaneously separated during heteroepitaxial growth on a single-crystal SrTiO3(001) substrate. The nanostructures are epitaxial in-plane as well as out-of-plane, with CoFe2O4 nanopillar arrays embedded in a BaTiO3 matrix. The CoFe2O4 nanopillars have uniform size and spacing and nearly circular cross section. As the substrate temperature increases from 750 to 950°C, the average diameter of the pillars increases from ∼9 to ∼70nm.
Highly efficient second-harmonic generation in doubly resonantplanar microcavities
Authors: Liscidini Marco , Andreani Lucio Claudio
Published: September 2004

A theoretical study of second-harmonic generation in planar microcavities with periodic dielectric mirrors is made. Strong enhancement of the nonlinear conversion is predicted when double resonance for the pump and harmonic fields, as well as phase matching, are achieved. For a given structure design, the finite angle of incidence is used as a tuning parameter and the splitting between cavity modes with different polarizations is used to compensate the material dispersion. Examples are given for GaAs cavities with AlGaAs∕Alox dielectric mirrors.
Vertical-cavity semiconductor devices for generation and detection of fluorescence emission on a single chip
Authors: Porta P. A. , Summers H. D.
Published: September 2004

In this letter, we describe the realization and the characterization of vertical-cavity semiconductor devices with monolithically integrated detectors for the excitation and detection of fluorescence emission from a fluorophore. These devices can act as excitation sources in forward bias and as detectors in reverse bias mode. Photonic microstructuring is used to control the optical field within the device. Detection is made possible at wavelengths longer than that of emission, with minimum attenuation of the output signal. These characteristics make these devices suitable for fluorescence spectroscopy as they are able to provide an excitation signal and detect the redshifted dye fluorescence.
Confinement in silicon nanowires: Optical properties
Authors: Bhattacharya S. , Banerjee D. , Adu K. W. , Samui S. , Bhattacharyya Somnath
Published: September 2004

The blueshift of the optical absorption edge along with the intense red photoluminescence (PL) peak has been observed from micron-long crystalline silicon nanowires prepared by pulsed-laser vaporization of heated Si (mixed with metal catalyst) targets. Previous studies on the confinement in silicon nanostructures resulted in a dispute regarding the application of theoretical models to explain their optical properties. Based on the microstructure a phenomenological confinement model, incorporating the nanowire diameter distribution is used, which is found to describe the optical properties including the shape of absorption spectra, the band gap, and the PL peak position of the Si nanowires very well.
Minority carrier diffusion length and lifetime for electrons in a type-II InAs∕GaSb superlattice photodiode
Authors: Li Jian V. , Chuang Shun Lien , Jackson Eric M. , Aifer Edward
Published: September 2004

We use the electron-beam-induced current (EBIC) technique to investigate carrier transport characteristics in a type-II InAs∕GaSb superlattice photodiode with cutoff wavelength at 7.7μm. We use a theoretical model that includes an extended generation source and depletion region to simulate the EBIC current on both sides of the p–n junction. The electron minority diffusion length in the p-superlattice, Le, is extracted from the simulation, from which the electron lifetime τe is obtained. Le increases from 0.275μm at 5.3Kto0.355μm at 100K. τe drops from 1.5ns at 5.3Kto0.13ns at 100K.
Laser-induced wavy pattern formation in metal thin films
Authors: Xiao Ke , Guan Zi Sheng , Wang Guo Jie , Jiang Lei , Zhu Dao Ben , Wang Yu Ren
Published: September 2004

Laser-induced well-ordered and controllable wavy patterns are constructed in the deposited metal thin film. The micrometer-sized structure and orientation of the wavy patterns can be controlled via scanning a different size of rectangle laser spot on the films. Ordered patterns such as aligned, crossed, and whirled wave structures were designed over large areas. This patterning technique may find applications in both exploring the reliability and mechanical properties of thin films, and fabricating microfluidic devices.
InGaSb
photodetectors using an InGaSb substrate for 2μm applications
Authors: Refaat Tamer F. , Abedin M. Nurul , Bhagwat Vinay , Bhat Ishwara B. , Dutta Partha S. , Singh Upendra N.
Published: September 2004

Detectors operating at 2μm are important for several applications including optical communication and atmospheric remote sensing. In this letter, fabrication of 2μm photodetectors using an InGaSb substrate is reported. The ternary substrates were grown using vertical Bridgmann technique and Zn diffusion was used to fabricate p–n junction diodes and photodiodes. Dark current measurement reveals that the breakdown voltage is in the 0.75 to 1V range. Spectral response measurements indicated a 2μm responsivity of 0.56A∕W corresponding to 35% quantum efficiency. Photodiode performance was compared to similar devices fabricated on binary substrates.
Electronic structure and spin polarization of MnGaP
Authors: Kronik Leeor , Jain Manish , Chelikowsky James R.
Published: September 2004

We present ab initio pseudopotential–density-functional calculations for the electronic structure of the dilute magnetic semiconductor MnxGa1−xP, with a realistic x=0.063, in its ordered ferromagnetic phase. We find that it possesses a spin-polarized valence band that could support ideal spin-polarized hole transport. We further find spin-polarized features in the conduction band that could support ideal spin-polarized transport of minority electrons. As such, it emerges as a silicon-lattice-matched candidate material for spintronics applications.
Video-rate compatible photorefractive polymers with stable dynamic properties under continuous operation
Authors: Fuentes-Hernandez Canek , Thomas Jayan , Termine Roberto , Meredith Gerald , Peyghambarian Nasser , Kippelen Bernard , Barlow Steve , Walker Gregory , Marder Seth R. , Yamamoto Michiharu , Cammack Kevin , Matsumoto Kenji
Published: September 2004

We report on photorefractive polymer composites that exhibit stable dynamic properties under continuous operation. These materials are based on a bis-triarylamine side-chain polymer matrix with a low ionization potential. The evolution of the response time for exposures up to 4kJ∕cm2 was studied and compared with that obtained in poly(n-vinylcarbazole) (PVK) based composites. In the composites, operational stability is combined with video-rate compatible dynamics, large dynamic range at moderate fields, and long shelf lifetimes.
Hydrogen dilution profiling for hydrogenated microcrystallinesilicon solar cells
Authors: Yan Baojie , Yue Guozhen , Yang Jeffrey , Guha Subhendu , Williamson D. L. , Han Daxing , Jiang Chun-Sheng
Published: September 2004

The structural properties of hydrogenated microcrystalline silicon solar cells are investigated using Raman, x-ray diffraction, and atomic force microscopy. The experimental results showed a significant increase of microcrystalline volume fraction and grain size with increasing film thickness. The correlation between the cell performance and the microstructure suggests that the increase of grain size and microcrystalline volume fraction with thickness is the main reason for the deterioration of cell performance as the intrinsic layer thickness increases. By varying the hydrogen dilution in the gas mixture during deposition, microstructure evolution has been controlled and cell performance significantly improved.
Monochromatic imaging and angular distribution measurements of extreme ultraviolet light from laser-produced Sn and SnO2 plasmas
Authors: Tao Y. , Sohbatzadeh F. , Nishimura H. , Matsui R. , Hibino T. , Okuno T. , Fujioka S. , Nagai K. , Norimatsu T. , Nishihara K. , Miyanaga N. , Izawa Y. , Sunahara A. , Kawamura T.
Published: September 2004

Properties of extreme ultraviolet (EUV) emission from laser-produced Sn and SnO2 plasmas were investigated. EUV emission images were taken with a monochromatic imager for 13.5nm with 4% bandwidth. It was found that the EUV emitting plasma is not formed symmetrically with respect to the target surface normal but extends toward laser incident axis. This result is consistent with the angular distribution of EUV emission peaked toward the direction nearly perpendicular to the laser axis. The asymmetric plasma can be attributed to the interaction of a long laser pulse with expanding plasma along the path of laser incidence.
90
°
a
−
b
domains in epitaxial ferroelectric Bi3.25La0.75Ti3O12 films
Authors: Chu Ming-Wen , Lee Sung Kyun , Hesse Dietrich , Gösele Ulrich
Published: September 2004

A cross-sectional high-resolution electron microscopy study was performed on (010)∕(100)-oriented ferroelectric Bi3.25La0.75Ti3O12 (BLT) films. Using Bragg filtering, curved, irregular, and nanoscale 90° domain configurations were observed. The weak ferroelastic strain of 0.024% suggests a negligible polarization clamping of 90°a–b domains under bipolar electric field and an easy 90° switching of the polar a axis in the ab plane. In addition, antiphase boundaries were characterized. A negligible contribution of 90°a–b domains to the fatigue of BLT is proposed.