bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphometric analysis of Alaskan members of the genus Potentilla sect. Niveae (Rosaceae)
Authors: Eriksen Bente
Published: March 2008

A morphometric study of Potentilla nivea, P unijlora, and P hookeriana, as well as the close relative of the latter, P furcata, has been carried out, and the quantitative data subjected to Canonical Discriminant Analysis. The four taxa belong to the arctic‐alpine section Niveae of Potentilla, and material for the analysis was collected in Alaska, U. S. A. The a priori defined groups are based on petiole hair type, the qualitative, and only, character traditionally used to distinguish taxa within Potentilla sect. Niveae. The hair types recognized previously by taxonomists have been vaguely defined, and the intraspecific variation of other morphological characters has never been discussed. Ordination by canonical discriminant analysis was performed to characterize mean differences among species, to obtain insight into group differences, and to estimate character weights from correlations between canonical variates and original variables. The four taxa differ significantly in the canonical analysis of six quantitative characters. Leaflet length, incision depth (length of leaflet teeth), and ovule number are shown to be the most important discriminators. A key to the four taxa, taking into account the intra‐ vesus interspecific variation, as well as character weights, is provided.
Changes in species composition following field and tree layer restoration and management in a wooded hay meadow
Authors: Austad I. , Losvik M. H.
Published: March 2008

A hillside with abandoned, wooded hay meadows in Leikanger in Sogn og Fjordane county, Western Norway, was investigated in 1992–1995. A management regime combining restoration (topping) of old pollarded trees, scything and removal of hay was reintroduced in the area. The availability of light, hydrological conditions and the nutrient content of the soil were the most important factors determining development of hay meadow vegetation to forest vegetation. Indicators of shaded conditions included Valeriana sambucifolia and Oxalis acetosella, while Anthriscus sylvestris was indicator of light conditions. Species such as Campanula rotundifolia, Pimpinella saxifraga, Plantago lanceolata, Lychnis viscaria and Hieracium pilosella, which were recorded mostly on dry ridges, were regarded as “relict” species, more common formerly when the area was managed in a traditional way. The cover of tall grasses and herbs, such as Dactylis glomerata, Poa trivialis and Anthriscus sylvestris, increased the first two years after restoration. This indicates an increase in available nutrients, probably a “pioneer clearing fertilization” due to the introduced pollarding. Restoration and management resulted in drier, more homogenous ecological conditions and reduced the differences in local climate between formerly open meadows and more wooded areas in the restored area. However, most of the vegetation seemed to be quite stable during the study period. One class, however, comprised releves from several unstable plots of the experimental site. The frequency of some light‐demanding species increased in the experimental site, while the frequency of Oxalis acetosella and Epilobium montanum increased in the control site.
Cyanoneuron (Rubiaceae), a new genus from Borneo and Sulawesi
Authors: Tange Christian
Published: March 2008

The genus Cyanoneuron is established to accommodate three Bornean and Sulawesi species previously placed in Myrioneuron. Two new species: C. grandiflorum and C. pedunculatum are described. All five species are illustrated. A survey of the character states including vegetative, inflorescence, floral, fruit, pollen, seed morphology and anatomy is given. The chromosome number has been counted for C. cyaneum, C. grandiflorum and C. pubescens. Cyanoneuron is tentatively included in the tribe Hedyotideae, but its affinity to genera inside this tribe is unknown.
Floral biology of the distylous Mediterranean shrub Jasminum fruticans (Oleaceae)
Authors: Guitián Javier , Guitián Pablo , Medrano Monica
Published: March 2008

Various aspects of the reproductive biology of two populations of the distylous shrub Jasminum fructicans (Oleaceae) in the northwest Iberian Peninsula were studied during 1994 and 1995. This species is a ‘tropical’ relict of pre‐Miocene origin. Two morphs (the L morph with long‐style/short‐pistil, and the S morph with short‐style/ long‐pistil) occur. Our results indicate that morph frequency ratio in the study populations is one‐to‐one. Experimental crosses revealed self‐incompatibility, very weak within‐morph compatibility and strong between‐morph compatibility (in all cases as is typical of distylous species). Pollen grains are larger in S‐morph plants, while both nectar reward and fruit set are higher in L‐morph plants. However, no differences were detected in number of pollen grains per stamen or in pollinator spectrum (the most frequent visitors to flowers of both morphs being species of the hy‐menopteran genera Anthophora, Melecta and Bombus).
A new Hyphoderma from Europe
Authors: Larsson Karl Henrik , Grosse‐Brauckmann Helga , Keller Jean
Published: March 2008

The new species Hyphoderma tibia (Aphyllophorales, Basidiomycotina) is described and illustrated using drawings and scanning electron microscope.
Biometry and DNA fingerprinting detect limited genetic differentiation among populations of the apomictic blackberry Rubus nessensis (Rosaceae)
Authors: Nybom Hilde
Published: March 2008

Clonal plant species have in many recent studies exhibited unexpectedly high levels of genetic differentiation. This seems to hold true also for several apomictic (agamospermous) species in spite of their potential ability to spread single genotypes over large areas through seed dispersal. By contrast, previous DNA fingerprint studies have demonstrated apomictic Rubus species to be extremely homogeneous. The present study was undertaken to estimate the extent and distribution of intraspecific genetic variation in R. nessensis. Populations differed significantly for many biometrical characters but this variation was evenly distributed, with few significant differences between single pairs of populations. Patterns indicating ecoclinal variation, which could be adaptive in origin, were not found. Populations also clustered close together in a two‐dimensional CVA plot, with only one population being somewhat further removed. DNA analysis of later collected material from this population as well as from three others yielded identical DNA fingerprints with each of two different multi‐locus DNA probes. Taken together with previous DNA fingerprint studies, these results indicate that a major part of the R. nessensis plants in Northern Europe have been derived from a single recombinational event, possibly making this genet the most widespread land‐living organism in the world. The encountered variation in biometrical characters is probably instead caused by e.g. minor somatic mutations. Rubus species have relatively large, bird‐dispersed seeds that probably travel further than the small, wind‐dispersed seeds found in most previously investigated apomicts (e.g. in Asteraceae). The potential for single genotypes to disperse over large areas should therefore be greater in Rubus than in many other apomictic species groups.
Epiphytic diatoms in oligotrophc Lake Grane Langsø, Denmark
Authors: Nygaard Gunnar
Published: March 2008

The epiphytic diatoms on plant‐remnants in 10 samples collected in July 1951–1957 from 0.25 m depth in Grane Langsø, Denmark were studied. Averages of their relative frequencies are compared with the relative frequencies of epiphytic diatoms from 11.25 m depth with the aid of a Rank‐Abundance diagram. The two graphs were very similar suggesting identity between the epiphytic communities from 0.25 m depth and 11.25 m depth. This suggestion is supported by a highly significant correlation between the relatively abundances of species in the communities from the two depths. Also the populations of the common diatom species Tabellaria flocculosa had the same dimensions of the cells in the two depths and on different host plants, and none of the numerous epiphytic diatoms were ever observed in the plankton of Grane Langsø during five years of regular examination. Overall, the results imply that the littoral plant communities and the pelagic waters offer widely different conditions for growth and survival of diatoms resulting in the development of strictly different communities. The difference between epiphytic and planktonic diatom communities are also likely to become fully expressed due to physical separation of the communities in Grane Langsø resulting from its small size and wind protected location surrounded by forests.
The taxonomic status of Lithophyllum stìctaeforme (Rhodophyta, Corallinales) and its generic position in light of phylogenetic considerations
Authors: Athanasiadis A.
Published: March 2008

The type ofLithophyllum stìctaeforme(Areschoug) Hauck (‵Melobesia stictaeformisAreschoug in J. Agardh) is re‐examined and shown to be conspecific with a common Mediterranean foliose coralline recently recognized asLithophyllum frondosum(Dufour) Furnari, Cormaci et Alongi (‵Melobesia frondosaDufour) and previously known by the misapplied nameLithophyllum (Pseudolithophyllum) expansumPhilippi. The generic position of the species inLithophyllumorPseudolithophyllumis phylogenetically examined, in the Hennigian sense. It is shown that secondary perithallial outgrowths (‘faux hypothalle’) may represent a synapomorphy for these genera that traditionally have been segregated from each other by the presence, respectively absence, of a coaxial ‘faux hypothalle’. Recognition of bothLithophyllumandPseudolithophyllumby virtue of a single character in its two states (absent vs. present) is however not tenable, if these genera are considered to be sister‐taxa.
Amomum jainii sp. nov. (Zingiberaceae) from N. E. India
Authors: Tripathi Sunil , Prakash Ved
Published: March 2008

A new species, Amomum jainii from N. E. India is described and illustrated. — CDRI Communication No. 5882.
A synopsis of the genus Zingiber (Zingiberaceae) in Thailand
Authors: Theilade Ida
Published: March 2008

Twenty six species of Zingiber have been found in Thailand. Six new species are described, Z. longibracteatum, Z. peninsulare, Z. villosum, Z. flavovirens, Z. larsenii and Z. newmanii. Four species and one variety have been recorded in Thailand for the first time, namely Z barbatum, Z. aff. integrum, Z. petiolatum, Z.wrayi and Z. puberulum var. ovoideum. A key to the species is provided, as well as species descriptions, distribution and specimen citations. The taxa have been typified as far as possible. Undoubtedly more species of Zingiber remain to be described from Thailand.
Plant species richness in Fennoscandia: evaluating the relative importance of climate and history
Authors: Grytnes John Arvid , Birks H. J. B. , Peglar Sylvia M.
Published: March 2008

In Fennoscandia, the species richness of vascular plants in 75 × 75 km squares is highly correlated with geographical (latitude and longitude) and climatic variables (accumulated respiration sum, mean January temperature, and mean July temperature). When generalised additive models (GAM) are used, over 80% of the variation in richness can be statistically explained by geography and climate. Even though climate has such a high explanatory power we present several arguments for interpreting these results with care. Climate has no ecologically sound explanatory power when the variation due to latitude and longitude is accounted for, and the strongest latitudinal gradient in summer temperature is in an area where the latitudinal gradient in species richness is absent. We discuss the role that Holocene history might have on the variation in species richness, and argue that history and climate should be considered simultaneously when explaining the observed patterns in the geographical variation of species richness.
Morphological observations of Synurophycean algae from some acidic habitats, including the description of a sub‐specific taxon
Authors: Siver Peter A.
Published: March 2008

Morphological observations of the siliceous cell coverings of five taxa of Synurophyceae are made based on specimens collected from acidic, seepage lakes situated in either the Ocala National Forest, Florida, U.S.A. or the Cape Cod National Seashore, Massachusetts, U.S.A. All but one of the lakes, Lake Dorr, were clearwater in nature. A new taxon, Mallomonas corymbosa var. poseidonii var. nov., is described based on differences in bristle structure. New morphological features of four additional taxa, Synura echìnulata, Mallomonas mangofera f. foveata, M. acaroides var. muskokana, and M. duerrschmidtiae are presented and discussed in relation to their existing taxonomic descriptions. Other taxa of Synurophyceae, Dinobryon spp., Aulacoseira spp., Asterionella ralfsii, and dinofiagellates were common constituents of the phytoplankton from the seven study lakes at the times of collection.
Pollen morphology in Primula sect. Carolinella (Primulaceae) and its taxonomic implications
Authors: Anderberg Arne A. , El‐Ghazaly Gamal
Published: March 2008

Pollen morphology in Primula section Carolinella has been investigated for the first time. Seven of the nine species constituting the section were available for study, i. e., P. cardioeides, P. chapaensis, P. intanoensis, P. kwangtungensis, P. kweichouensis, P. partschiana, and P. rugosa, A considerable variation in pollen morphology was found among the investigated species, particularly in number and arrangement of the apertures. Pollen of different species were either tricolpate, tricolporate, trisyncolpate, or polycolpate. Within Primula, the section Carolinella is diagnosed by having calyptrate capsules and leaves with revolute vernation, but the variation in pollen morphology indicates that this group is heterogeneous, and that either polycolpate pollen or a capsular lid has evolved more than once in the genus Primula.
Uncommon vascular plant species in an East‐Central Swedish forest area‐a comparison between young and old stands
Authors: Elofsson Maria , Gustafsson Lena
Published: March 2008

Abundance of uncommon vascular plant species (indicator species and red‐listed species) was recorded in 120 circular (12.6 m2) random plots in young (10–24 years after deal‐cutting) and old (>80 years) forest stands, respectively, in the forest area of Vällen (2 600 ha), ca. 80 km north of Stockholm, Sweden. Factors describing stand density, field‐layer and soil moisture were recorded. A total of 16 species were observed and of these 14 were found in old and 9 in young stands. Seven species occurred exclusively in the old stands and two in the young stands. The total number of species records was significantly higher in young than in old stands, 80 and 71, respectively. Mean number of records per ha was ca. 530 for the young stands and ca. 470 for the old. Of the five species common enough to be tested, a difference was only found forParis quadrifolia, which was significantly more frequent in young than old stands.Galium odoratum, Hepatica nobilis, Lathyrus vernusandParis quadrifoliagrew in significantly more sheltered sites, e.g. beneath other herbs and grasses or close to shrubs and trees in young compared to old stands. Nested subset analysis showed that the whole data‐set had a nested structure.Galium odoratumwas significantly nested and thus indicated rich plant assemblages. In this calcareous area with nutrient‐rich forest soils, there evidently is a potential for at least some uncommon vascular plant species to survive the phases following clearcutting. The study indicates that green‐tree retention at final fellings and avoidance of heavy shrub removal during cleaning are beneficial to the flora.
Revision of the genus Genlisea (Lentibulariaceae) in Africa and Madagascar with notes on ecology and phytogeography
Authors: Fischer Eberhard , Porembski Stefan , Barthlott Wilhelm
Published: March 2008

The African and Madagascan representatives of the carnivorous genus Genlisea are investigated. All African material belongs to subgenus Genlisea and can be assigned to 10 taxa, which mainly differ in indumentum of calyx, corolla and ovary. The former section Tayloria, restricted to South America, is raised to subgeneric rank. One species, Genlisea margaretae, occurs in South‐East Africa and Madagascar as well. All species are restricted to specific oligotrophous habitats like granitic outcrops (inselbergs), ferricretes, white sands and swamps. Genlisea taylori from Angola is described as new. All species are described and illustrated and a key and distribution maps are presented.
Response of Norwegian alpine communities to nitrogen
Authors: Möls Tõnu , Paal Jaanus , Fremstad Eli
Published: March 2008

The effect of nitrogen pollution on species cover was tested in the Dovre mountains, south‐central Norway, through a three‐year fertilisation experiment in a low‐alpine community and a two‐year one in a middle‐alpine community, both dominated by lichens. The doses used were 0.7, 3.5 and 7 g N/m2, the highest doses corresponding to 1.75 and 3.5 times the annual deposition of nitrogen in southwestern Norway. The results were tested using the SAS/STAT/MIXED procedure. Using the Bonferroni correction, the procedure did not confirm a change in the cover of single species due to increased nitrogen supply, but there seemed to be a general tendency for an increase in cover in the low‐alpine Cetrarietum nivalis community. When less rigorous tests were applied, Arctostaphylos uva‐ursi, Vaccinium vitis‐idaea, Polytrichum piliferum, Cetraria nivalis and Cladonia mitis in Cetrarietum nivalis, and Cladonia coccifera in Phyllodoco‐Juncetum trifidi seemed to indicate that nitrogen had some effect on these communities. The lack of a clear response in single species may be due to the application of low doses over a short time‐span in an environment characterised by large interannual variations in climate, the deficiency of other important nutrients, dryness, the low growth potential of the species involved, and, to some extent, the community structure.
A synopsis of crustose calicioid lichens and fungi from mainland Africa and Madagascar
Authors: Tibell Leif
Published: March 2008

A synopsis of 42 species is given. Thirteen of the species are tropical to warm temperate, seventeen of the species are antitropical and mainly occur in the mountainous areas.Calicium lutescens, Chaenotheca chloroxanthaandMycocalicium rapaxare described as new.Acroscyphus sphaerophoroides, a spectacular species with an unusual distribution, is reported from Africa for the first time, from South Africa. Another fourteen species are reported new to Africa, and numerous new records for African countries are also included. Keys to the genera and species are given along with description of the species.
The systematics of Soldanella (Primulaceae) based on morphological and molecular (ITS, AFLPs) evidence
Authors: Zhang Li‐Bing , Kadereit Joachim W.
Published: March 2008

Based on the observation of more than 6300 herbarium specimens and molecular (ITS, AFLPs) evidence,Soldanellais divided into 16 species and four subspecies.Soldanella angusta, S. oreodoxaandS. rugosaare described as new, and the circumscriptions ofS. marmarossiensis, S. major, S. pusillassp.pusillaandS. hungaricaare emended. Nine hybrid names are lectotypified. All non‐hybrid taxa are described in detail and distribution maps are provided. Interspecific relationships are discussed on the background of morphological and molecular variation.
Astragalus sect. Astragalus (Fabaceae) in Iran, complementary notes with a key to the species
Authors: Ranjbar M. , Karamian R.
Published: March 2008

Astragalus zarreianus. is described and illustrated from Iran. It belongs to section Astragalus. This new species confined to western part of Iran (Prov. Illam) from only one location. A key to the species of the section known from Iran is prepared. Differences between the section and the closely related sections are discussed. On the basis of some important trends, an informal grouping is undertaken for yellow flower Astragali. Moreover, A. pseudo‐orthocarpus is considered as a valid species in this treatment and differences with its closest relatives are described.
Evolution of morphological diversity and resin secretion in flowers of Clusia (Clusiaceae): insights from ITS sequence variation
Authors: Gustafsson Mats H. G. , Bittrich Volker
Published: March 2008

The taxonomically poorly known, neotropical genus Clusia (Clusiaceae) comprises over 300 species of trees, shrubs and hemiepiphytes. The flowers are morphologically highly diverse and offer either nectar, pollen or resin as a reward for pollinators. Resin production in flowers is a poorly studied phenomenon, known from only five angiosperm genera. Variation in sequences of the nuclear ribosomal ITS region was analysed cladistically in order to trace the evolution of floral resin production in Clusia, and as a first step towards a phylogenetically based reclassification of the genus. The most parsimonious trees show that the genera Havetia, Havetiopsis, Oedematopus and Quapoya are nested inside Clusia. Traditionally, Clusia has been divided into sections based on androecial variation, and most of these groups are supported as monophyletic based on the ITS data. Sections Retinostemon, Havetia and Cochlanthera together form one of very few well‐supported suprasectional groups. Character optimisation experiments suggest that resiniferous flowers have evolved at least three times independently in Clusia, but a character‐evolution model with a single origin for floral resin is only slightly less parsimonious. Clades of resiniferous species are morphologically the most diverse, and it is concluded that resin production has been a key innovation triggering floral morphological diversification. Secondary losses of resin and switches to apomixis seem to be correlated with colonisation of habitats and areas where resin‐collecting bees are less frequent.
Some Desmids from the northern islands of Iceland and Orkney
Authors: Williamson David B.
Published: March 2008

Samples collected in Iceland and the Orkneys have been examined for their desmid floras. Both sets of samples revealed a mixed but in the main, rather common assortment of taxa, although some represent new records for both areas, so the knowledge of the desmid flora of these islands has been considerably increased by the present investigations. Some comments are also made about desmid records from the Faeroe Islands.
Crataegus azarolus var. sharania (Rosaceae), a new variety for the flora of Iraq
Authors: Shahbaz Saleem E. , Sadeq Zeravan A.
Published: March 2008

Crataegus azarolus var. sharania from Dohuk, Iraq is described as a new variety new to science. Morphological characteristics of twig, leaf, inflorescence, and infructescence are studied. Chromosome counting proved to be N= X=17. Results are compared with that of local varieties of C. azarolus.
On a new subspecies of Adoxa moschatellina (Adoxaceae), apoendemic in Calabria (S Italy)
Authors: Peruzzi Lorenzo , Passalacqua Nicodemo Giuseppe
Published: March 2008

Adoxa moschatellina subsp. cescae subsp. nova is proposed. Phytogeographical, karyological and morphological evidences are presented. This subspecies appear to be endemic to the Coastal Chain, Calabria (S Italy) and shows a triploid (2n = 54) chromosome complement, different from the diploid (2n = 36) one of A. moschatellina s.s. By a morphological point of view, pollen and stomata size of the latter (from the whole Italy, including the Pollino Massif, N Calabria) appear to be smaller in average than those of the new subspecies, which can be considered as a new apoendemic taxon, because of its distribution and high ploidy level.
Brief femoral artery ischaemia provides protection against myocardial ischaemia–reperfusion injury in rats: the possible mechanisms
Authors: Shahid Mohd , Tauseef Mohammad , Sharma K. K. , Fahim M.
Published: March 2008

The present study was conducted to examine the role of nitric oxide (NO), mitochondrial ATP‐sensitive K+ channels (mito K+ATP channels) and reactive oxygen species (ROS) and their interdependence in brief femoral artery ischaemia‐induced myocardial preconditioning. To assess myocardial injury, myocardial infarction was induced by occlusion followed by reperfusion of the left anterior descending (LAD) coronary artery in anaesthetized rats and was assessed by triphenyl tetrazolium chloride (TTC) staining. Left ventricular function was assessed by left ventricular end‐diastolic pressure (LVEDP) and the maximal rate of rise of left ventricular pressure [LV(dP/dt)max]. Serum creatine kinase‐MB (CK‐MB) and lactate dehydrogenase (LDH) were determined by colorimetric kits. Remote preconditioning (RPC) was induced by 15 min occlusion of femoral arteries followed by 10 min of reperfusion just before LAD coronary artery occlusion. Brief femoral artery ischaemia led to a 61% reduction in myocardial infarct size, 57% reduction in elevated serum LDH and 72% reduction in elevated CK‐MB activities, and a significant improvement in LVEDP and LV(dP/dt)max compared with control animals. Pretreatment with 5‐hydroxydecanoate (5‐HD) or l‐NAME or N‐acetylcystein (NAC) blocked this protective effect of femoral artery ischaemia. Moreover, infusion of l‐arginine or diazoxide before coronary artery occlusion markedly reduced the myocardial infarction and improved the left ventricular function. This effect of l‐arginine was found to be abolished by the blockade of mito K+ATP channels with 5‐HD and, similarly, the effect of diazoxide was blocked in the presence of a ROS scavenger, NAC. The results suggest that brief femoral artery ischaemia‐induced RPC is mediated by a combination of increased NO synthesis, opening of mito K+ATP channels and increased ROS production. Moreover, it appears that NO is working upstream and acts via activation of mito K+ATP channels, which subsequently increases the production of ROS.
Activation of GIRK channels in substantia gelatinosa neurones of the adult rat spinal cord: a possible involvement of somatostatin
Authors: Nakatsuka Terumasa , Fujita Tsugumi , Inoue Kazuhide , Kumamoto Eiichi
Published: March 2008

Recent studies have suggested that spinal G‐protein‐coupled, inwardly rectifying K+ (GIRK) channels play an important role in thermal nociception and the analgesic actions of morphine and other agents. In this study, we show that spinal GIRK channels are activated by an endogenous neurotransmitter using whole‐cell patch‐clamp recordings from substantia gelatinosa (SG) neurones in adult rat spinal cord slices. Although repetitive stimuli applied to the dorsal root did not induce any slow responses, ones focally applied to the spinal dorsal horn produced slow inhibitory postsynaptic currents (IPSCs) at a holding potential of −50 mV in about 30% of the SG neurones recorded. The amplitude and duration of slow IPSCs increased with the number of stimuli and decreased with removal of Ca2+ from the external Krebs solution. Slow IPSCs were associated with an increase in membrane conductance; their polarity was reversed at a potential close to the equilibrium potential for K+, calculated from the Nernst equation. Slow IPSCs were blocked by addition of GDP‐β‐S into the patch‐pipette solution, reduced in amplitude in the presence of Ba2+, and significantly suppressed in the presence of an antagonist of GIRK channels, tertiapin‐Q. Somatostatin produced an outward current in a subpopulation of SG neurones and the slow IPSC was occluded during the somatostatin‐induced outward current. Moreover, slow IPSCs were significantly inhibited by the somatostatin receptor antagonist cyclo‐somatostatin. These results suggest that endogenously released somatostatin may induce slow IPSCs through the activation of GIRK channels in SG neurones; this slow synaptic transmission might play an important role in spinal antinociception.
Detailed comparison of expressed and native voltage‐gated proton channel currents
Authors: Musset B. , Cherny V. V. , Morgan D. , Okamura Y. , Ramsey I. S. , Clapham D. E. , DeCoursey T. E.
Published: March 2008

Two years ago, genes coding for voltage‐gated proton channels in humans, mice and Ciona intestinalis were discovered. Transfection of cDNA encoding the human HVCN1 (HV1) or mouse (mVSOP) ortholog of HVCN1 into mammalian cells results in currents that are extremely similar to native proton currents, with a subtle, but functionally important, difference. Expressed proton channels exhibit high H+ selectivity, voltage‐dependent gating, strong temperature sensitivity, inhibition by Zn2+, and gating kinetics similar to native proton currents. Like native channels, expressed proton channels are regulated by pH, with the proton conductance–voltage (gH–V) relationship shifting toward more negative voltages when pHo is increased or pHi is decreased. However, in every (unstimulated) cell studied to date, endogenous proton channels open only positive to the Nernst potential for protons, EH. Consequently, only outward H+ currents exist in the steady state. In contrast, when the human or mouse proton channel genes are expressed in HEK‐293 or COS‐7 cells, sustained inward H+ currents can be elicited, especially with an inward proton gradient (pHo < pHi). Inward current is the result of a negative shift in the absolute voltage dependence of gating. The voltage dependence at any given pHo and pHi is shifted by about −30 mV compared with native H+ channels. Expressed HV1 voltage dependence was insensitive to interventions that promote phosphorylation or dephosphorylation of native phagocyte proton channels, suggesting distinct regulation of expressed channels. Finally, we present additional evidence that speaks against a number of possible mechanisms for the anomalous voltage dependence of expressed H+ channels.
Dynamic ATP signalling and neural development
Authors: Dale Nicholas
Published: March 2008

Purinergic signalling plays a major role in the function of every organ including the brain. A growing body of evidence also suggests that purinergic signalling is important in the development of the retina, cochlea and neocortex. In these three contexts release of ATP through the spontaneous gating of connexin hemichannels in cells, respectively, of the retinal pigment epithelium, Köllicker's organ, and the radial glia triggers waves of intracellular Ca2+ release. In the case of the developing retina and cortex, the released ATP acts to control proliferation of neuronal precursor cells, while in the cochlea it coordinates the spontaneous activity of adjacent hair cells to refine the tonotopic maps in the cochlear nucleus. Recently ATP‐derived ADP signalling has been implicated at the very earliest stages of development, notably in triggering the gene expression necessary for formation of the eye. It is now timely to test the extent to which connexin hemichannel‐mediated ATP release and accompanying Ca2+ waves contribute to all stages of development.
Co‐activation of p38 mitogen‐activated protein kinase and protein tyrosine phosphatase underlies metabotropic glutamate receptor‐dependent long‐term depression
Authors: Moult Peter R. , Corrêa Sônia A. L. , Collingridge Graham L. , Fitzjohn Stephen M. , Bashir Zafar I.
Published: March 2008

Long‐term potentiation (LTP) and long‐term depression (LTD) are forms of synaptic plasticity thought to contribute to learning and memory. Much is known about the mechanisms of NMDA receptor‐dependent LTD in the CA1 region of rat hippocampus but there is still considerable uncertainty about the mechanisms of LTD induced by mGluR activation (mGluR‐LTD). Furthermore, data on mGluR‐LTD derives largely from studies using pharmacologically induced LTD. To investigate mGluR‐LTD that is more physiologically relevant we have examined, in CA1 of adult rat hippocampus, mechanisms of synaptically induced mGluR‐LTD. We provide the first demonstration that activation of protein tyrosine phosphatase (PTP) is essential for the induction of synaptically induced mGluR‐LTD. In addition, we show that activation of p38 MAPK is also required for this form of LTD. Furthermore, LTD can be mimicked and occluded by activation of p38 MAPK, provided that protein tyrosine kinases (PTKs) are inhibited. These data therefore demonstrate that a novel combination of signalling cascades, requiring both activation of p38 MAPK and tyrosine de‐phosphorylation, underlies the induction of synaptically induced mGluR‐LTD.
Three-Dimensional Finite Element Analysis of Dovetail Attachments With and Without Crowning
Authors: Beisheim J. R. , Sinclair G. B.
Published: March 2008

The stress analysis of dovetail attachments presents some challenges. These stem from the high stress gradients present, the contact inequalities attending conforming contact, and the nonlinearities inherent in Coulomb friction laws. Obtaining converged contact stresses in the presence of these phenomena is demanding, especially in three dimensions. In Beisheim and Sinclair (2003, ASME J. Turbomach., 125, pp. 372–379), a submodeling approach with finite elements is employed to meet these challenges when friction is not present. Here we extend this approach to treat contact when friction is present. Converged stresses are obtained by using two successive submodels. Comparing these stresses with two-dimensional analysis elucidates some of the truly three-dimensional aspects of the stress analysis of dovetail attachments. Further comparisons of contact stresses when crowning is added indicate the possible alleviation of fretting fatigue that may be afforded by this means.
Effect of a Cutback Squealer and Cavity Depth on Film-Cooling Effectiveness on a Gas Turbine Blade Tip
Authors: Mhetras Shantanu , Narzary Diganta , Gao Zhihong , Han Je-Chin
Published: March 2008

Film-cooling effectiveness from shaped holes on the near tip pressure side and cylindrical holes on the squealer cavity floor is investigated. The pressure side squealer rim wall is cut near the trailing edge to allow the accumulated coolant in the cavity to escape and cool the tip trailing edge. Effects of varying blowing ratios and squealer cavity depth are also examined on film-cooling effectiveness. The film-cooling effectiveness distributions are measured on the blade tip, near tip pressure side and the inner pressure side and suction side rim walls using pressure sensitive paint technique. The internal coolant-supply passages of the squealer tipped blade are modeled similar to those in the GE-E3 rotor blade with two separate serpentine loops supplying coolant to the film-cooling holes. Two rows of cylindrical film-cooling holes are arranged offset to the suction side profile and along the camber line on the tip. Another row of shaped film-cooling holes is arranged along the pressure side just below the tip. The average blowing ratio of the cooling gas is controlled to be 0.5, 1.0, 1.5, and 2.0. A five-bladed linear cascade in a blow down facility with a tip gap clearance of 1.5% is used to perform the experiments. The free-stream Reynolds number, based on the axial chord length and the exit velocity, was 1,480,000 and the inlet and exit Mach numbers were 0.23 and 0.65, respectively. A blowing ratio of 1.0 is found to give best results on the pressure side, whereas the tip surfaces forming the squealer cavity give best results for M=2. Results show high film-cooling effectiveness magnitudes near the trailing edge of the blade tip due to coolant accumulation from upstream holes in the tip cavity. A squealer depth with a recess of 2.1mm causes the average effectiveness magnitudes to decrease slightly as compared to a squealer depth of 4.2mm.
Heat Transfer Behavior of Silica Nanoparticles in Pool Boiling Experiment
Authors: Milanova Denitsa , Kumar Ranganathan
Published: March 2008

The heat transfer characteristics of silica (SiO2) nanofluids at 0.5vol% concentration and particle sizes of 10nm and 20nm in pool boiling with a suspended heating Nichrome wire have been analyzed. The influence of acidity on heat transfer has been studied. The pH value of the nanosuspensions is important from the point of view that it determines the stability of the particles and their mutual interactions toward the suspended heated wire. When there is no particle deposition on the wire, the nanofluid increases critical heat flux (CHF) by about 50% within the uncertainty limits regardless of pH of the base fluid or particle size. The extent of oxidation on the wire impacts CHF, and is influenced by the chemical composition of nanofluids in buffer solutions. The boiling regime is further extended to higher heat flux when there is agglomeration on the wire. This agglomeration allows high heat transfer through interagglomerate pores, resulting in a nearly threefold increase in burnout heat flux. This deposition occurs for the charged 10nm silica particle. The chemical composition, oxidation, and packing of the particles within the deposition on the wire are shown to be the reasons for the extension of the boiling regime and the net enhancement of the burnout heat flux.
Transient and Steady-State Experimental Comparison Study of Effective Thermal Conductivity of Al2O3∕Water Nanofluids
Authors: Li Calvin H. , Williams Wesley , Buongiorno Jacopo , Hu Lin-Wen , Peterson G. P.
Published: March 2008

Nanofluids are being studied for their potential to enhance heat transfer, which could have a significant impact on energy generation and storage systems. However, only limited experimental data on metal and metal-oxide based nanofluids, showing enhancement of the thermal conductivity, are currently available. Moreover, the majority of the data currently available have been obtained using transient methods. Some controversy exists as to the validity of the measured enhancement and the possibility that this enhancement may be an artifact of the experimental methodology. In the current investigation, Al2O3∕water nanofluids with normal diameters of 47nm at different volume fractions (0.5%, 2%, 4%, and 6%) have been investigated, using two different methodologies: a transient hot-wire method and a steady-state cut-bar method. The comparison of the measured data obtained using these two different experimental systems at room temperature was conducted and the experimental data at higher temperatures were obtained with steady-state cut-bar method and compared with previously reported data obtained using a transient hot-wire method. The arguments that the methodology is the cause of the observed enhancement of nanofluids effective thermal conductivity are evaluated and resolved. It is clear from the results that at room temperature, both the steady-state cut-bar and transient hot-wire methods result in nearly identical values for the effective thermal conductivity of the nanofluids tested, while at higher temperatures, the onset of natural convection results in larger measured effective thermal conductivities for the hot-wire method than those obtained using the steady-state cut-bar method. The experimental data at room temperature were also compared with previously reported data at room temperature and current available theoretical models, and the deviations of experimental data from the predicted values are presented and discussed.
Carbon Nanotubes, Synthesis, Growth and Orientation Control in Opposed Flow Diffusion Flames
Authors: Kennedy Lawrence A.
Published: March 2008

The combustion synthesis of carbon nanotubes is reviewed, examining their formation and control in diffusion flames. Much of the initial work in this area employed coflow diffusion flames and provided insight into carbon nanotube (CNT) formation. However, the inherent multidimensional nature of such coflow flames made the critical spatial location difficult to maintain. Among this early work, our UIC group demonstrated the superiority of the opposed flow diffusion flame configuration due to its uniform radial distribution that reduces such flow to a one-dimensional process. While a summary of the early coflow flame work is presented, the use of the opposed flow diffusion flame will be the focus of this review. The production of carbon nanostructures in the absence of a catalyst is discussed together with the range of morphology of nanostructures generated when a catalyst is employed. The important aspect of control of the growth and orientation of CNTs and generation of CNT arrays through the use of electric fields is examined as is the use of anodized aluminum oxide templates. Fruitful areas for further research such as the functional coating of CNTs with polymers and the application of these opposed flow flames to synthesis of other materials are discussed.
Effect of Rarefaction, Dissipation, and Accommodation Coefficients on Heat Transfer in Microcylindrical Couette Flow
Authors: Jiji Latif M.
Published: March 2008

This paper examines the effects of rarefaction, dissipation, curvature, and accommodation coefficients on flow and heat transfer characteristics in rotating microdevices. The problem is modeled as a cylindrical Couette flow with a rotating shaft and stationary housing. The housing is maintained at uniform temperature while the rotating shaft is insulated. Thus, heat transfer is due to viscous dissipation only. An analytic solution is obtained for the temperature distribution in the gas filled concentric clearance between the rotating shaft and its stationary housing. The solution is valid in the slip flow and temperature jump domain defined by the Knudsen number range of 0.001<Kn<0.1. The important effect of the momentum accommodation coefficient on velocity reversal and its impact on heat transfer is determined. The Nusselt number was found to depend on four parameters: the momentum accommodation coefficient of the stationary surface σuo, Knudsen number Kn, ratio of housing to shaft radius ro∕ri, and the dimensionless group [γ∕(γ+1)](2σto−1)∕(σtoPr). Results indicate that curvature, Knudsen number, and the accommodation coefficients have significant effects on temperature distribution, heat transfer, and Nusselt number.
The Experimental Exploration of Embedding Phase Change Materials With Graphite Nanofibers for the Thermal Management of Electronics
Authors: Weinstein Randy D. , Kopec Thomas C. , Fleischer Amy S. , D’Addio Elizabeth , Bessel Carol A.
Published: March 2008

To improve the thermal performance of phase change materials (PCMs), graphite nanofibers were embedded into a paraffin PCM. The thermal effects of graphite fiber loading levels (0–5wt%) and graphite fiber type (herringbone, ribbon, or platelet) during the melting process were examined for a 131cm3 volume system with power loads between 3W and 7W(1160–2710W∕m2). It was found that the maximum system temperature decreased as graphite fiber loading levels increased and that the results were fiber-structure dependent.
An Atomistic Simulation Study of the Role of Asperities and Indentations on Heterogeneous Bubble Nucleation
Authors: Novak Brian R. , Maginn Edward J. , McCready Mark J.
Published: March 2008

Heterogeneous bubble nucleation was studied on surfaces having nanometer scale asperities and indentations as well as different surface-fluid interaction energies. Nonequilibrium molecular dynamics simulations at constant normal stress and either temperature or heat flux were carried out for the Lennard–Jones fluid in contact with a Lennard–Jones solid. When surface defects were of the same size or smaller than the estimated critical nucleus (the smallest nucleus whose growth is energetically favored) size of 1000–2000Å3, there was no difference between the defected surfaces and atomically smooth surfaces. On the other hand, surfaces with significantly larger indentations had nucleation rates that were about two orders of magnitude higher than the systems with small defects. Moreover, nucleation was localized in the large indentations. This localization was greatest under constant heat flux conditions and when the solid-fluid interactions were weak. The results suggest strategies for enhancing heterogeneous bubble nucleation rates as well as for controlling the location of nucleation events.
Alumina Nanoparticles Enhance the Flow Boiling Critical Heat Flux of Water at Low Pressure
Authors: Kim Sung Joong , McKrell Thomas , Buongiorno Jacopo , Hu Lin-Wen
Published: March 2008

Many studies have shown that addition of nanosized particles to water enhances the critical heat flux (CHF) in pool boiling. The resulting colloidal dispersions are known in the literature as nanofluids. However, for most potential applications of nanofluids the situation of interest is flow boiling. This technical note presents first-of-a-kind data for flow boiling CHF in nanofluids. It is shown that a significant CHF enhancement (up to ∼30%) can be achieved with as little as 0.01% by volume concentration of alumina nanoparticles in flow experiments at atmospheric pressure, low subcooling (<20°C), and relatively high mass flux (⩾1000kg∕m2s).
Rotary Machine Health Diagnosis Based on Empirical Mode Decomposition
Authors: Yan Ruqiang , Gao Robert X.
Published: March 2008

This paper presents a signal decomposition and feature extraction technique for the health diagnosis of rotary machines, based on the empirical mode decomposition. Vibration signal measured from a defective rolling bearing is decomposed into a number of intrinsic mode functions (IMFs), with each IMF corresponding to a specific range of frequency components contained within the vibration signal. Two criteria, the energy measure and correlation measure, are investigated to determine the most representative IMF for extracting defect-induced characteristic features out of vibration signals. The envelope spectrum of the selected IMF is investigated as an indicator for both the existence and the specific location of structural defects within the bearing. Theoretical foundation of the technique is introduced, and its performance is experimentally verified.
Dynamics and Performance of a Harmonically Excited Vertical Impact Damper
Authors: Ramachandran Sanjiv , Lesieutre George
Published: March 2008

Particle impact dampers (PIDs) have been shown to be effective in vibration damping. However, our understanding of such dampers is still limited, based on the theoretical models existing today. Predicting the performance of the PID is an important problem, which needs to be investigated more thoroughly. This research seeks to understand the dynamics of a PID as well as those parameters which govern its behavior. The system investigated is a particle impact damper with a ceiling, under the influence of gravity. The base is harmonically excited in the vertical direction. A two-dimensional discrete map is obtained, wherein the variables at one impact uniquely dictate the variables at the next impact. This map is solved using a numerical continuation procedure. Periodic impact motions and “irregular” motions are observed. The effects of various parameters such as the gap clearance, coefficient of restitution, and the base acceleration are analyzed. The dependence of the effective damping loss factor on these parameters is also studied. The loss factor results indicate peak damping for certain combinations of parameters. These combinations of parameters correspond to a region in parameter space where two-impacts-per-cycle motions are observed over a wide range of nondimensional base accelerations. The value of the nondimensional acceleration at which the onset of two-impacts-per-cycle solutions occurs depends on the nondimensional gap clearance and the coefficient of restitution. The range of nondimensional gap clearances over which two-impacts-per-cycle solutions are observed increases as the coefficient of restitution increases. In the regime of two-impacts-per-cycle solutions, the value of nondimensional base acceleration corresponding to onset of these solutions initially decreases and then increases with increasing nondimensional gap clearance. As the two-impacts-per-cycle solutions are associated with high loss factors that are relatively insensitive to changing conditions, they are of great interest to the designer.