bluuebunny/crossref_metadata_2025 huggingface dataset:
Tropical-Subtropical Ramalinae in the Ramalina Farinacea Complex
Authors: Stevens G. Nell
Published: May 2007

Five corticolous taxa of sorediate Ramalinae which occur in the tropics and subtropics are shown to comprise the tropical component of the otherwise temperate Ramalina farinacea complex. Their morphology, anatomy, chemistry, ecology and distribution are discussed. Ramalina pacifica Asah., R. nervulosa (Müll. Arg.) des Abb., R. dumeticola Krog & Swinscow and R. luciae Mohlo et al., were investigated together with an unnamed acid-deficient taxon. Ramalina nervulosa and R. pacifica are maintained as species while the remainder are considered as varieties of these species; viz. R. nervulosa var. dumeticola (Krog & Swinscow) comb. nov., R. nervulosa var. luciae (Mohlo et al.) comb. nov., and R. pacifica var. inacida var. nov.
Sizes and Growth-Rates of Thalli of the Lichen Rhizocarpon Geographicum on the Moraines of the Glacier De Valsorey, Valais, Switzerland
Authors: Proctor M. C. F.
Published: May 2007

Measurements of thalli of Rhizocarpon geographicum on the recent moraines of the Glacier de Valsorey and their surroundings are considered in relation to thallus growth rates and colonization following glacial recession. Photographs taken in 1975 and 1979 show that up to c. 3.5 cm diam the relation of maximum growth-rate to thallus size is approximated by a growth curve of the kind derived by Aplin and Hill, rising asymptotically towards a constant rate of radial growth (here c. 0.5 mm year−1). Growth-rates of many individual thalli fall well below the maximum. Parameters of the fitted growth curves are used to construct curves of thallus radius against time. Taken in conjunction with the field measurements these suggest two main phases of colonization, one from about 1880 to 1910, and one from about 1930 onwards. Some general considerations relating to lichenometry and lichen growth curves are discussed.
Two Little-Known or Misunderstood Brigantiaea Species from New Zealand
Authors: Hafellner J.
Published: May 2007

Descriptions are given of two little-known species of Brigantiaea (Lecanorales, Brigantiaeaceae) which are widely distributed in New Zealand. Brigantiaea lobulata F. J. Walker & Hafellner sp. nov. is described and the following new combinations are proposed: B. tabacodes (Zahlbr.), B. nipponica (Sato) and B. austroamericana (Räsänen), combs. nov.
Seasonal Photosynthetic Capacity Changes in Lichens: A Provisional Mechanistic Interpretation
Authors: Kershaw K. A.
Published: May 2007

The photosynthetic capacity changes that have previously been documented in lichens are reviewed together with the mechanisms of photosynthetic capacity change in free-living algae recently proposed by Prezelin and co-workers. Examination of seasonal capacity changes in Peltigera praetextata, P. rufescens, Cladonia rangiferina, C. stellaris, and Caloplaca trachyphylla using photosynthetic-illumination curves, provisionally establishes that synthesis of additional photosynthetic units, seasonal interruption of energy transduction, as well as enzymatic rate changes in the Calvin cycle, are all involved in these capacity changes.
Placynthium Arachnoideum, a New Lichen from Patagonia, and Notes on Other Species of the Genus in the Southern Hemisphere
Authors: Henssen Aino
Published: May 2007

The new species Placynthium arachnoideum Henssen is described from Patagonia. The lichen is characterized by incurved lobes retaining in part the false branching of the Scytonema phycobiont, and by two-celled, thick-walled spores with a perforated septum. Some localities in the Southern Hemisphere are given for P. asperellum, P. nigrum and P. subradiatum.
Quantification of Branch Dwelling Lichens for the Detection of Air Pollution Impact
Authors: Addison P. A.
Published: May 2007

In the Athabasca Oil Sands area of Alberta, a study was carried out to test a lichen community transplant technique and to determine the influence of oil sands extraction and processing emissions on lichen cover of transplanted communities. Measurement errors of a photographic technique for the determination of lichen cover were dependent upon lichen species but were not correlated to lichen cover. When lichen covers were small therefore, relative errors were very large. Changes in cover of naturally occurring lichen communities on black spruce branches were not significant over a four-year period. Lichen communities transplanted under jack pine and white spruce trees had cover changes with time not different from naturally occurring communities even over a period of years.

Significant (P<0.001) cover reductions of some lichen groups occurred on transplanted branches under white spruce within 8–3 km of a pollution source. Evernia, Cetraria, and Bryoria groups were reduced whereas Hypogymnia showed no response over a 3 year measurement period. Reductions in lichen cover were greater than the demonstrated precision of the technique.
Impact of Simulated Acid Rains on Nitrogenase Activity in Peltigera Aphthosa and P. Polydactyla
Authors: Fritz-Sheridan R. P.
Published: May 2007

Two ubiquitous diazotrophic North American lichens, Peltigera aphthosa and P. polydaclyla, were subjected to simulated acid rain. Both lichens exhibited a 50% reduction in nitrogen fixation at pH 5, 80% reduction at pH 4 and complete inhibition at pH 2. Nitrogen fixation was zero after 20 days exposure to simulated rain at pH 3 and zero after fourdays at pH 2.
Apothecium Production in Xanthoria Parietina
Authors: Pentecost A. , Rose C. I.
Published: May 2007

A regression equation was used to relate apothecium diameter to apothecium dry weight inXanthona parietina. This was used to estimate the contribution of apothecia to thallus weight in 80 randomly selected thalli from vertical concrete posts at Romney, Kent (mean 22–5%, range 0–87%). The energy contents of apothecia and the sterile thallus were found to be similar (17.6—18.2 KJ g−1 dry weight) and apothecium production was found to be independent of thallus aspect. The results are discussed with reference to apothecium growth rates and the allocation of resources in lichens.
Contribution to the Lichen Flora of Madeira
Authors: Arvidsson L. , Wall S.
Published: May 2007

37 taxa are discussed, with 34 being new to Madeira. Of these, Gyalectidium filicmum Müll. Arg., Massalongia carnosa (Dickson) Körber, Physaa tnbaaoides Nyl. and Rinodina intermedia Bagl., are first records from Macaronesia. Ecology and distribution of the species are briefly outlined. Our investigation shows that the proportion of both northern temperate and tropical elements in the lichen flora of Madeira is higher than formerly known.
A New Micarea From the Scottish Highlands
Authors: Coppins B.J.
Published: May 2007

A new terncolous Micarea (M. viridiatra sp. nov.) is described from the Cairngorm Mountains. It is similar and apparently closely allied to M. turfosa.
Artificial Re-Establishment of Lichens IV. Comparison between Natural and Synthetic Thalli of Usnea Strigosa
Authors: Ahmadjian V. , Jacobs J. B.
Published: May 2007

Synthetic thalli of Usnea strigosa produced the same fibril morphology and secondary compounds as natural thalli. The outer cortex of synthetic lichens was covered with crystals of usnic acid and compounds related to norstictic acids. The common presence on the fibrils of lichen acids suggests that these compounds have a functional role in the symbiosis. During alcohol dehydration, crystals of usnic acid dissolved and left impressions in the mucilage around the symbionts. The impressions were valuable indicators of the position of crystals in the lichen thallus. Crystal impressions of usnic acid were common on the cortical hyphae and were seen also on the surface of algal cells. The crystal impressions were larger in the synthetic lichen than in natural thalli. Impressions of norstictic acid and related compounds were not seen.
The Nature and Origin of Campylidia in Lichenized Fungi
Authors: Sérusiaux E.
Published: May 2007

The campylidia hypothesis, first introduced by Müller Argoviensis (1881) and recently restored by Vězda (1983), for the erect helmet-shaped structures found on foliicolous lichens and usually known as ‘ Pyrenotrichum ’ is adopted as being the most satisfactory. In the Badimia pollilensis aggregate, campylidia are shown to derive from primordia identical to those of the apothecia. In the genus Sporopodium, algal cells are included in the conidiogenous layer and are dispersed together with conidia. This also seems to be the case in the genus Loflammia. Short descriptions are given for the most common campylidium known as ‘ Pyrenotrichum splitgerben ’ and for another not yet assignable to a peculiar genus. Loflammia denwulinii sp. nov. is described from New Guinea.
Aspicilia Excavata: A New Lichen Species From Europe
Authors: Thor G. , Timdal E.
Published: May 2007

Aspicilia excavata Thor & Timdal sp. nov. is described and reported from Austria, Finland, Norway and Sweden. It is usually sterile and mainly characterized by an indeterminate thallus composed of small, white pruinose squamules excavated from the margin by dark brown to black soralia. The species grows on calcareous rocks and mortar, mainly on steep to overhanging faces.
Three New Saxicolous Ramalinae from Australia
Authors: Stevens G. Nell
Published: May 2007

Three new maritime saxicolous Ramalina species are described from Australia, R. litorea, R. whinrayii and R. caespitella N. Stevens spp. nov. The first species is tropical in occurrence, whereas the last two are temperate taxa and endemic to Australia.
Nomenclatural Notes on Some Australian Cladonia Species
Authors: Archer A. W.
Published: May 2007

An examination of the holotype or lectotype of eight taxa, first described from Australia, in the genus Cladonia has shown that the names are, with the exception of Cladonia fruticulosa Krempelh., synonyms of previously described taxa. The taxa examined were as follows (with the correct name in parentheses); C. cariosa var. diffissa F. Wilson (C. enantia Nyl.); C. conchata Nyl. (C. pyxidata (L.)Hoffm.); C. cornucopioides var. grandis Krempelh. (C. pleurola (Flörke) Schaerer); C. deformis var. tasmanica Krempelh. (C. subdigitata Nyl.); Cenomyce firma Laurer, Cladonia firma (Laurer) Krempelh. (C. murrayi W. Martin); C. lepidula Krempelh. (C. ochrochlora Flörke); C. pergracilis Krempelh. (C. ochrochlora Florke); C. subsquamosa var. pulverulenta Vainio (C. squamosula Müll. Arg.) Homosekikaic acid is reported to occur with thamnolic acid in C. squamosula Müll. Arg.
Nectriella Santessonii, A New Lichenicolous Pyrenomycete With an Acremonium Anamorph
Authors: Lowen Rosalind , Hawksworth D. L.
Published: May 2007

Nectriella santessonii sp. nov. (Hypocreales) on Anaptychia runcinata (With.) Laundon, is introduced for a species that previously has been confused with N. tincta (Fuckel) R. Sant. The two species are distinguished by several fundamental characters. The growth of single ascospores in pure culture has proved the connection between the new species and an Acremonium anamorph.
A Simulation Study on the Effect of Flora Composition, Study Design and Index Choice on the Predictive Power of Lichen Bioindication
Authors: Herben T. , Liška J.
Published: May 2007

The effects of several elements of floristic structure and bioindication study design on the predictive power of the Index of Atmospheric Purity (IAP) proposed by LeBlanc & De Sloover were studied using Monte Carlo simulation. The predictive power was assessed by the correlation coefficient of the IAP value, computed under specified assumptions, and the stand position along a simulated pollution gradient. The effects of seven parameters were studied: proportion of sensitive and poleophilous species, species frequency distribution, size of total species pool, number of stands, distribution of stands along the air pollution gradient and index choice. The simulations showed that the median predictive power of such studies is affected mainly by the proportion of sensitive and poleophilous species, the number of species, and distribution of trees along the pollution gradient. The variance of the predictive power is influenced mainly by the proportion of sensitive species, frequency distribution, number of stands and distribution of stands along the pollution gradient. Recommendations for further bioindication studiesare given.
A Review of Psilolechia
Authors: Coppins B. J. , Purvis O. W.
Published: May 2007

The genus Psilolechia Massal. is reviewed; four species are accepted, including P. leprosa sp. nov. from copper-rich sites in north-west Europe and Greenland, and P. purpurascens sp. nov. from Tasmania. A hyphomycetous anamorph is described for P. clavulifera, and anomalous forms of P. lucida with a vicarious, Stichococcus photobiont are reported.
The Genus Vezdaea in the British Isles
Authors: Coppins B. J.
Published: May 2007

Notes are provided on the genus Vezdaea and its five species represented in the British Isles, including V. acicularis sp. nov. A key to the six European species is included.
Choreospora Gen. Nov., A New Lichenicolous Hyphomycete from Australia
Authors: Constantinescu O. , Santesson R.
Published: May 2007

Choreospora tibellii P. Const. & R. Sant. gen. & sp. nov., a sporodochial hyphomycete with non-septate, tetraradiate conidia is described from Australia. The fungus grows on a sterile foliicolous lichenized thallus (?Echinoplaca sp.) on leaves of Cordyline.
The Genus Ramonia in the British Isles
Authors: Coppins B. J.
Published: May 2007

Notes are provided on the genus Ramonia and its four species represented in the British Isles, including R. dictyospora sp. nov. and R. nigra sp. nov.
Nitrogen Fixation on the Tropical Volcano, La Soufrière (Guadeloupe): Nitrogen Fixation, Photosynthesis and Respiration During the Prevailing Cloud/Shroud Climate By Stereocaulon Virgatum
Authors: Fritz-Sheridan R. P. , Coxson D. S.
Published: May 2007

Stereocaulon virgatum Ach. has colonized lava flows deposited on the west flank of the volcano La Soufrière. The mean annual rate of acetylene reduction was 43·4 nmol C2H4 gdw−1 h−1 with maximum rates during the prevalent cloud/shroud meteorology of 101 and minimum rates during rare high insolation events of 0·63 nmol gdw−1 h−1. Percentage thallus moisture was the major variable controlling nitrogenase activity. During cloud/shroud conditions the upper 90% of the lichen canopy reduced 85% of the acetylene. Canopy shading reduced intra-canopy temperatures allowing the basal 10% of the canopy to fix nitrogen during insolation shocks. Basal portions of pseudopodetia exhibited reduced rates of ethylene production when exposed to canopy surface light intensities during cloud/shroud conditions. The recovery pattern of nitrogenase following desiccation during an insolation shock is presented. Rates of photosynthesis during cloud/shroud conditions were high, reaching 50% of those attained during saturating light intensities.
Caloplaca Lucifuga: A New Lichen Species From Europe
Authors: Thor G.
Published: May 2007

Caloplaca lucifuga Thor sp. nov. is described and reported from Denmark, England, France, Germany, Italy and Sweden. It is only found sterile and is mainly characterized by its endophloedic, sorediate thallus, chemistry and habitat. In Sweden, the species is found in dense wooded pastures dominated by Quercus robur, growing on the bark of very old trunks of Quercus robur or, rarely, Tilia cordata. Outside Sweden, it is found also on Castanea sativa, Fagus sylvatica and Ulmus glabra.
Notes on the Genus Arthopyrenia in the British Isles
Authors: Coppins B. J.
Published: May 2007

The genus Arthopyrenia is redefined to include only corticolous lichenized or non-lichenized fungi. A key and notes are provided for the 14 species accepted for the British Isles, including three new species, A. carneobrunneola, A. ranunculospora and A. viridescens. Arthopyrenia nilescens is resurrected from synonymy, A. cinereopruinosa is confirmed as occurring in the British Isles, and A. fraxini, A. salicis and A. subcerasi are added to the British list. The following names are lectotypined: Arthopyrenia fraxini Massal. (including f. orbicularis Massal. and f. rufidula Massal.), A. salicis Massal., Verrucaria nitescens Salwey and V. subcerasi Vainio.
Biochemical Comparison of two Ecologically Distinctive Forms of Xanthoria Elegans in the Canadian High Arctic
Authors: Fahselt Dianne , Krol Marianna
Published: May 2007

Xanthoria elegans has a broad ecological amplitude, world-wide distribution and includes morphological variants which differ markedly with respect to colour, form and frequency of apothecia. Distinctive thallus forms are associated with different habitats. Samples from two contrasting habitats were studied on Ellesmere Island in the Canadian High Arctic. Carotenoids, polyphenolic products and isoenzymes were examined to establish whether two thallus types were biochemically distinct. Pigments were comparable in both morphological variants, as were approximately half of the most frequently occurring enzyme forms. Enzymatic similarity between the two resembled that between conspecific populations of other lichens. On the basis of the chemical attributes investigated, the thallus forms did not warrant recognition as fundamentally distinct entities, but were merely variants of an ecologically versatile and extremely plastic species.
Notes on the Arthoniaceae in the British Isles
Authors: Coppins B. J.
Published: May 2007

Arthonia anglica Coppins, A. anombrophila Coppins & P. James (syn. A. cinereopruinosa auct. brit.) and A. ligniariella Coppins are newly described, and Arthothelium ilicinum var. dictyosporum is given specific rank. British material of ‘Arthonia exilis’ is shown to be Bryostigma leucodontis Poelt & Döbb., which is transferred to Arthonia. Arthonia granitophila Th. Fr. (syn. Melaspilea subarenacea J. Nowak & Kiszka) is transferred to Melaspilea. Arthonia ligniaria Hellb. is added to the British list. Arthonia astroidestra Nyl. is lectotypified and shown not to be conspecific with A. stellaris Krempelh., while A. excipienda Nyl. (syn. A. hibernica Nyl.) is found not to be a synonym of A. dispersa (Schrader) Nyl. Catillaria ooliticola W. Watson is made a synonym of A. lapidicola (Taylor) Branth & Rostrup; Arthonia punctilliformis Leighton is excluded from that genus; and A. dispersa and A. patellulata Nyl. are excluded from the British list. In addition, four new lichenicolous species on corticolous hosts are introduced: Arthonia cohabitans Coppins, A. graphidicola Coppins, A. invadens Coppins and A. thelotrematis Coppins.
Macentina Stigonemoides (Verrucariaceae), a New Lichenized Species from Great Britain and Ireland
Authors: Orange A.
Published: May 2007

Macentina stigonemoides sp. nov. is described from trees in Great Britain and Ireland; it is characterized by a filamentous to granular thallus with papillose cortical cells and pale perithecia with 3–5-septate spores.
The Genus Bryoria Sect. Implexae in Norway
Authors: Holien H.
Published: May 2007

In Norway three species are recognized in the genus Bryoria sect. Implexae, B. capillaris (Ach.) Brodo & D. Hawksw., B. implexa (Hoffm.) Brodo & D. Hawksw., and B. nadvornikiana (Gyeln.) Brodo & D. Hawksw. Notes on their morphology, chemistry, ecology and distribution are given. Bryoria friabilis Brodo & D. Hawksw., B. pseudofuscescens (Gyeln.) Brodo & D. Hawksw., and B. vrangiana (Gyeln.) Brodo & D. Hawksw. are considered to be conspecific with B. implexa. Bryoria setacea (Ach.) Brodo & D. Hawksw. is considered to be conspecific with B. capillaris.
Enzyme Polymorphism in Sexual and Asexual Umbilicate Lichens from Sverdrup Pass, Ellesmere Island, Canada
Authors: Fahselt Dianne
Published: May 2007

Four enzymes were examined electrophoretically from each of seven stands of arctic umbilicate lichens in central Ellesmere Island. The species studied included Umbilicaria virginis Schaerer, which was prolifically apotheciate, and U. decussata (Vill.) Zahlbr. and U. hyperborea (Ach.) Hoffm., which were both sterile. Electrophoretic banding patterns were converted to presence/absence data reflecting the occurrence of electromorphs in each thallus, and enzyme polymorphism was assessed using three statistical methods, one based on frequency of individual enzyme forms, another on the number of banding patterns, and a third on the proportional representation of different band patterns within each collection site. Greater enzyme variability occurred in stands of apotheciate species than in stands of species which were asexual in the study area, suggesting that regular sexual reproduction contributes to greater diversity.
The Lichen Genus Pterygiopsis in Northern Europe
Authors: Jørgensen P. M.
Published: May 2007

The genus Pterygiopsis Vainio (Lichinaceae), originally described from Brazil, is shown to have two species in Northern Europe: P. coracodiza (Nyl.) Henssen growing on irrigated rocks in N.W. Europe (France, Great Britain, W. Sweden and Norway), and P. lacustris P. M. Jørg. & R. Sant. sp. nov. occurring ± submerged in some lakes in S. Sweden.
Three New Species of Relicina From Australasia
Authors: Elix John A. , Johnston Jen
Published: May 2007

Three new species of Relicina are described: R. clarkensis Elix & Johnston and R. subcoronata Elix & Johnston from Australia, and R. columnaria Elix & Johnston from Papua New Guinea and Sabah.
Studies on Micarea in Australasia I. Four New Species From Tasmania
Authors: Coppins B. J. , Kantvilas G.
Published: May 2007

Four new species of Micarea are described from Tasmanian collections: M. austroternaria sp. nov. (also from Chile), M. flagellispora sp. nov. (also from New Zealand), M. isabellina sp. nov., and M. mutabilis sp. nov. (also from mainland Australia).
Isidiate Taxa in the Teloschistales and their Ecological and Evolutionary Significance
Authors: Kärnefelt I.
Published: May 2007

Thirteen isidiate taxa in the Teloschistales are briefly discussed, i.e. Letrouitia corallina (Müll. Arg.) Hafellner, L. leprolyta (Nyl.) Hafellner, Caloplaca bassiae (Ach.) Zahlbr., C. granulosa (Müll. Arg.) Jatta, C. herbidella (Hue) H. Magn., C. isidiigera Vězda, C. isidiosa (Vainio) Zahlbr., C. littorea Tavares, C. namibensis Kärnef., C. ochraceofulva (Müll. Arg.) Jatta, C. verruculifera (Vainio) Zahlbr., Xanthoria domogledensis Veˇzda and X. isidioidea (Beltr.) Szat. The presumed origins and affinities of these taxa, which are also often fertile, are discussed. The role of isidia in reproduction and dispersal, and the justification of specific status in some of these taxa is questioned.
Decomposition of Species of Pseudocyphellaria and Sticta in a Southern Chilean Forest
Authors: Guzman G. , Quilhot W. , Galloway D. J.
Published: May 2007

The annual rate of lichen decomposition was measured in a mixed, cool temperate rainforest in Puyehue National Park, southern Chile. Five macrolichens, Pseudocyphellaria berberina, P. divutsa, P. glabra, P. nitida and Sticta hypochra, and bamboo leaves (Chusquaea macrostachya) were used as experimental material. Rates of decomposition are high in all lichen species and ranged from k = 0·45 to 2·79. Lichens with hopane triterpenoids {P. divulsa and P. glabra) were more resistant to decomposition. The contribution of these lichens to the nutrient economy of the rainforest ecosystem is highly significant, as they are both abundant in terms of biomass and have a rapid turnover.
Lichens of the Dartmoor Rocks
Authors: Giavarini V. J.
Published: May 2007

A description of the lichen communities associated with natural rock outcrops and derelict mine workings in the upland region of Dartmoor, south-west England, is presented. An examination of 34 study sites revealed 270 taxa, of which 28 are reported as new to Devon including several national rarities. Notes on 29 tors have been prepared and reasons for the predominance or decline of particular communities or species are discussed.
Statistical Analysis of Bioindicator Value of Epiphytic Lichens
Authors: Oksanen Jari , Läärä Esa , Zobel Kristjan
Published: May 2007

Generalized linear modelling was applied in analysing the bioindicator value of epiphytic lichens for air pollution around an industrial centre in the Siberian mountains using data published previously by Zobel (1988a). The occurrence of taxa on tree boles was systematically related to the distance from the pollution source and to the altitude from sea level. Binomial distribution was postulated to describe the random variation and maximum likelihood and quasi-likelihood methods were used. Zobel had pooled the original data by grouping distance and altitude into three qualitative levels. The model for pooled data with qualitative factors generally had a poor fit. We assigned quantitative values, linear and quadratic contrasts, to the altitude and distance levels and a linear by linear interaction term between altitude and distance. In most taxa the interaction appeared significant, and these models had generally a better fit and smaller overdispersion than qualitative models. Finally, more effective analysis was performed on the original plotwise data utilizing unpublished quantitative information for distance and altitude. Most species (16/19) had a significant and usually positively monotone response to distance. In the majority of these (10/16) the effect of distance varied between the altitude levels most often so that the lichens were scarcer at low altitude and their increase was faster at high altitude.
Pyrenocollema Elegans, A New Marine Lichen
Authors: Santesson R.
Published: May 2007

Pyrenocollema elegans sp. nov., a widespread lichen on the Atlantic coast of Europe and the Pacific coast of North and South America, is distinguished from other members of the genus by a thallus bearing numerous black ridges and warts.
WHY SHOULD PHILOSOPHERS RULE? PLATO'S REPUBLIC AND
ARISTOTLE'S PROTREPTICUS
Authors: Bobonich Christopher
Published: May 2007

I examine Plato's claim in the Republic that philosophers
must rule in a good city and Aristotle's attitude towards this claim in
his early, and little discussed, work, the Protrepticus. I argue
that in the Republic, Plato's main reason for having philosophers
rule is that they alone understand the role of philosophical knowledge in
a good life and how to produce characters that love such knowledge. He
does not think that philosophic knowledge is necessary for getting right
the vast majority of judgments about actions open to assessment as
virtuous or vicious. I argue that in the Protrepticus Aristotle
accepts similar reasons for the rule of philosophers, but goes beyond the
Republic and seems to suggest that philosophic knowledge is
required for getting right ethical and political judgments in general. I
close by noting some connections with Aristotle's later views in the
Eudemian Ethics, the Nicomachean Ethics, and the
Politics.
Water vapor diffusion in Mars subsurface environments
Authors: Hudson Troy L. , Aharonson Oded , Schorghofer Norbert , Farmer Crofton B. , Hecht Michael H. , Bridges Nathan T.
Published: May 2007

The diffusion coefficient of water vapor in unconsolidated porous media is measured for various soil simulants at Mars‐like pressures and subzero temperatures. An experimental chamber which simultaneously reproduces a low‐pressure, low‐temperature, and low‐humidity environment is used to monitor water flux from an ice source through a porous diffusion barrier. Experiments are performed on four types of simulants: 40–70μm glass beads, sintered glass filter disks, 1–3μm dust (both loose and packed), and JSC Mars–1. A theoretical framework is presented that applies to environments that are not necessarily isothermal or isobaric. For most of our samples, we find diffusion coefficients in the range of 2.8 to 5.4 cm2s−1at 600 Pascal and 260 K. This range becomes 1.9–4.7 cm2s−1when extrapolated to a Mars‐like temperature of 200 K. Our preferred value for JSC Mars–1 at 600 Pa and 200 K is 3.7 ± 0.5 cm2s−1. The tortuosities of the glass beads is about 1.8. Packed dust displays a lower mean diffusion coefficient of 0.38 ± 0.26 cm2s−1, which can be attributed to transition to the Knudsen regime where molecular collisions with the pore walls dominate. Values for the diffusion coefficient and the variation of the diffusion coefficient with pressure are well matched by existing models. The survival of shallow subsurface ice on Mars and the providence of diffusion barriers are considered in light of these measurements.
Catalytic mechanism of Zn2+-dependent polyol dehydrogenases: kinetic comparison of sheep liver sorbitol dehydrogenase with wild-type and Glu154→Cys forms of yeast xylitol dehydrogenase
Authors: Klimacek Mario , Hellmer Heidemarie , Nidetzky Bernd
Published: May 2007

Co-ordination of catalytic Zn2+ in sorbitol/xylitol dehydrogenases of the medium-chain dehydrogenase/reductase superfamily involves direct or water-mediated interactions from a glutamic acid residue, which substitutes a homologous cysteine ligand in alcohol dehydrogenases of the yeast and liver type. Glu154 of xylitol dehydrogenase from the yeast Galactocandida mastotermitis (termed GmXDH) was mutated to a cysteine residue (E154C) to revert this replacement. In spite of their variable Zn2+ content (0.10–0.40 atom/subunit), purified preparations of E154C exhibited a constant catalytic Zn2+ centre activity (kcat) of 1.19±0.03 s−1 and did not require exogenous Zn2+ for activity or stability. E154C retained 0.019±0.003% and 0.74±0.03% of wild-type catalytic efficiency (kcat/Ksorbitol=7800±700 M−1· s−1) and kcat (=161±4 s−1) for NAD+-dependent oxidation of sorbitol at 25 °C respectively. The pH profile of kcat/Ksorbitol for E154C decreased below an apparent pK of 9.1±0.3, reflecting a shift in pK by about +1.7–1.9 pH units compared with the corresponding pH profiles for GmXDH and sheep liver sorbitol dehydrogenase (termed slSDH). The difference in pK for profiles determined in 1H2O and 2H2O solvent was similar and unusually small for all three enzymes (≈+0.2 log units), suggesting that the observed pK in the binary enzyme–NAD+ complexes could be due to Zn2+-bound water. Under conditions eliminating their different pH-dependences, wild-type and mutant GmXDH displayed similar primary and solvent deuterium kinetic isotope effects of 1.7±0.2 (E154C, 1.7±0.1) and 1.9±0.3 (E154C, 2.4±0.2) on kcat/Ksorbitol respectively. Transient kinetic studies of NAD+ reduction and proton release during sorbitol oxidation by slSDH at pH 8.2 show that two protons are lost with a rate constant of 687±12 s−1 in the pre-steady state, which features a turnover of 0.9±0.1 enzyme equivalents as NADH was produced with a rate constant of 409±3 s−1. The results support an auxiliary participation of Glu154 in catalysis, and possible mechanisms of proton transfer in sorbitol/xylitol dehydrogenases are discussed.
A vasopressin/oxytocin-related conopeptide with γ-carboxyglutamate at position 8
Authors: Möller Carolina , Marí Frank
Published: May 2007

Vasopressins and oxytocins are homologous, ubiquitous and multifunctional peptides present in animals. Conopressins are vasopressin/oxytocin-related peptides that have been found in the venom of cone snails, a genus of marine predatory molluscs that envenom their prey with a complex mixture of neuroactive peptides. In the present paper, we report the purification and characterization of a unique conopressin isolated from the venom of Conus villepinii, a vermivorous cone snail species from the western Atlantic Ocean. This novel peptide, designated γ-conopressin-vil, has the sequence CLIQDCPγG* (γ is γ-carboxyglutamate and * is C-terminal amidation). The unique feature of this vasopressin/oxytocin-like peptide is that the eighth residue is γ-carboxyglutamate instead of a neutral or basic residue; therefore it could not be directly classified into either the vasopressin or the oxytocin peptide families. Nano-NMR spectroscopy of the peptide isolated directly from the cone snails revealed that the native γ-conopressin-vil undergoes structural changes in the presence of calcium. This suggests that the peptide binds calcium, and the calcium-binding process is mediated by the γ-carboxyglutamate residue. However, the negatively charged residues in the sequence of γ-conopressin-vil may mediate calcium binding by a novel mechanism not observed in other peptides of this family.
Collagen pretzels revealed by electron microscopy
Authors: Kadler Karl
Published: May 2007

Collagen XV is a million-dalton protein with a structural role in skeletal muscle and capillaries. As with all collagens, studies of its function are hindered by the absence of good structural data: collagens are triple-helical, non-crystallizable, multidomain proteins with extensive post-translational modification that are refractory to analysis by high-resolution structural techniques. For collagen XV, this situation is compounded by the fact that it is also a proteoglycan. In this issue of the Biochemical Journal, Myers and her colleagues use rotary shadowing electron microscopy to obtain images of purified collagen XV molecules that are sufficiently detailed to show the three-lobed structure of the N-terminus and individual glycosaminoglycan side chains. Individual molecules appear as knotted strands resembling a pretzel (a pastry snack folded in a unique figure-of-eight), which contrasts with our conventional image of collagen molecules as semi-rigid rods. Importantly, collagen XV multimerizes into cruciform structures in which simpler forms have two to four molecules per complex. Immunoelectron microscopy revealed knotted collagen XV complexes bridging collagen fibrils adjacent to basement membrane. These accomplishments are made all the more impressive by the fact that collagen XV was purified from human umbilical cord, in which the protein is represented at only (1−2)×10−4% of dry weight!
The Development of the Text Reception Threshold Test: A Visual Analogue of the Speech Reception Threshold Test
Authors: Zekveld Adriana A. , George Erwin L. J. , Kramer Sophia E. , Goverts S. Theo , Houtgast Tammo
Published: May 2007

Purpose

In this study, the authors aimed to develop a visual analogue of the widely used Speech Reception Threshold (SRT; R. Plomp & A. M. Mimpen, 1979b) test. The Text Reception Threshold (TRT) test, in which visually presented sentences are masked by a bar pattern, enables the quantification of modality-aspecific variance in speech-in-noise comprehension to obtain more insight into interindividual differences in this ability.

Method

Using an adaptive procedure similar to the SRT test, the TRT test determines the percentage of unmasked text needed to read 50% of sentences correctly. SRTs in stationary noise (SRT
STAT
), modulated noise (SRT
MOD
), and TRTs were determined for 34 participants with normal hearing, aged 19 to 78 years.

Results

The results indicate that about 30% of the variance in SRT
STAT
and SRT
MOD
is shared with variance in TRT, which reflects the shared involvement of a modality-aspecific cognitive or linguistic ability in forming meaningful wholes of fragments of sentences.

Conclusion

The TRT test, a visual analogue of the SRT test, has been developed to measure the variance in speech-in-noise comprehension associated with modality-aspecific cognitive skills. In future research, normative data of the TRT test should be developed. It would also be interesting to measure TRTs of individuals experiencing difficulties understanding speech.
Measures of the Glottal Source Spectrum
Authors: Kreiman Jody , Gerratt Bruce R. , Antoñanzas-Barroso Norma
Published: May 2007

Purpose

Many researchers have studied the acoustics, physiology, and perceptual characteristics of the voice source, but despite significant attention, it remains unclear which aspects of the source should be quantified and how measurements should be made. In this study, the authors examined the relationships among a number of existing measures of the glottal source spectrum, along with the association of these measures to overall spectral shapes and to glottal pulse shapes, to determine which measures of the source best capture information about the shapes of glottal pulses and glottal source spectra.

Method

Seventy-eight different measures of source spectral shapes were made on the voices of 70 speakers. Principal components analysis was applied to measurement data, and the resulting factors were compared with factors similarly derived from oral speech spectra and glottal pulses.

Results

Results revealed high levels of duplication and overlap among existing measures of source spectral slope. Further, existing measures were not well aligned with patterns of spectral variability. In particular, existing spectral measures do not appear to model the higher frequency parts of the source spectrum adequately.

Conclusion

The failure of existing measures to adequately quantify spectral variability may explain why results of studies examining the perceptual importance of spectral slope have not produced consistent results. Because variability in the speech signal is often perceptually salient, these results suggest that most existing measures of source spectral slope are unlikely to be good predictors of voice quality.
Determination of Phonation Instability Pressure and Phonation Pressure Range in Excised Larynges
Authors: Zhang Yu , Reynders William J. , Jiang Jack J. , Tateya Ichiro
Published: May 2007

Purpose

The present study was a methodological study designed to reveal the dynamic mechanisms of phonation instability pressure (PIP) using bifurcation analysis. Phonation pressure range (PPR) was also proposed for assessing the pressure range of normal vocal fold vibrations.

Method

The authors first introduced the concept of bifurcation on the basis of a symmetric vocal fold model and then applied the bifurcation analysis to data from excised larynges. By recording acoustic signals from 10 excised larynges, the authors measured phonation threshold pressure (PTP), PIP, and PPR at the bifurcation pressure points from the spectrograms as subglottal pressure was progressively increased. Furthermore, to investigate the effects of vocal fold elongation on PTP, PIP, and PPR, the authors manipulated the elongation of the vocal folds at 0%, 5%, 10%, and 15% of the resting vocal fold length.

Results

The authors found that PTP, PIP, and PPR were effectively determined using the bifurcation analysis. When vocal fold elongation was increased from 0% to 15%, PTP was significantly increased (p< .001), PIP was not significantly changed (p= .54), and PPR was significantly decreased (p= .003).

Conclusion

PIP and PPR represent important parameters to assess phonation instability. Bifurcation analysis represents a valuable procedure for revealing the mechanisms behind PTP, PIP, and PPR and for investigating the effects of vocal fold biomechanical parameters on these 3 pressure parameters.
Lexical Aspect and the Use of Verb Morphology by Children With Specific Language Impairment
Authors: Leonard Laurence B. , Deevy Patricia , Kurtz Robert , Krantz Chorev Laurie , Owen Amanda , Polite Elgustus , Elam Diana , Finneran Denise
Published: May 2007

Purpose

Many typically developing children first use inflections such as –
ed
with verb predicates whose meanings are compatible with the functions of the inflection (e.g., using –
ed
when describing events of brief duration with clear end points, such as
dropped
). This tendency is assumed to be beneficial for development. In this study, the authors examine whether preschool-aged children with specific language impairment (SLI) show a similar tendency.

Method

Sixteen children in each of three groups participated—children with SLI, typically developing children matched for age (TD–A), and younger typically developing children matched for mean length of utterance (TD–MLU). The children described actions in contexts that promoted either past tense –
ed
or progressive aspect –
ing
in past contexts. Half of the verb predicates referred to events of brief duration with distinct endpoints (e.g.,
drop
), and half referred to events of considerable duration with less distinct points of termination (e.g.,
play
).

Results

Both the TD–A children and the TD–MLU children used –
ed
with verb predicates of the first type more consistently than they did with verb predicates of the second type. They showed the reverse pattern for –
ing
. The children with SLI did not show any effects according to the verb predicate type. However, although the children with SLI made less overall use of –
ed
than did both groups of TD children, they differed only from the TD–A children in their overall use of –
ing
.

Conclusion

Difficulties with tense-related morphology may be compounded in children with SLI if they fail to make use of associations between the lexical aspect of verb predicates and the grammatical function of the accompanying inflections. The authors argue that the advantages of using these associations as a starting point in acquisition may be especially important in the case of –
ed
. Additional studies of children with SLI are clearly needed, including those that employ longitudinal, naturalistic data.
Bragg rotor spectrometer for the JET tokamak (abstract)
Authors: Barnsley R. , Patel A. , Peacock N. J. , Smith R. T. C.
Published: May 2007

A Bragg rotor spectrometer uses diffractors ranging from LiF (420) (2d=0.18 nm) to a multilayer mirror (Ni–C 2d=11.7 nm). The extension to longer wavelengths is particularly useful at JET, where radiated power and Zeff are usually dominated by light impurities such as Be and C, whose H- and He-like transitions lie between about 2.5 and 10 nm. A hexagonal rotor scans six diffractors sequentially and gives either full coverage of the soft x-ray spectrum (to monitor a range of ionization stages of any possible impurity), or high monochromatic sensitivity (to monitor trace impurities and give time resolution of ∼10 μs for the study of transient events such as impurity injection). A large area gas proportional counter covers a Bragg angle range from 20° to 70°, with each of its ten anodes being connected to an independent amplifier-discriminator chain, allowing count rates up to 20 MHz to be processed. Moderate resolving power is provided by a 1:600 Soller collimator. A smaller rotor is mounted with a side-by-side array of four small diffractors, and is reciprocated over a relatively small Bragg angle range to give a time resolution of 20 ms for about ten representative lines (for routine analysis of radiated power components).
A CO2 laser tangential imaging system for CDX-U (abstract)
Authors: Nazikian R. M. , Robinson J. , Wright J. , Kaita R.
Published: May 2007

In a previous paper [R. Nazikian and B. Grek, Rev. Sci. Instrum. 61, 2899 (1990)], it was shown that tangential imaging provides a powerful new technique for rendering two-dimensional images of local density fluctuations in toroidal plasma devices. The technique consists of projecting a CO2 laser beam tangent to magnetic field lines at the plasma midplane and using phase contrast or other related optical methods for imaging line integral density fluctuations. In this paper we present recent progress in the development of such an imaging system for CDX-U. The interferometer makes use of a novel variation on the Zernike phase contrast method for detecting phase variations impressed on laser beams propagating through random media. This work supported by Department of Energy contract No. DE-AC02-76-CHO-3073.
Optical nonlinearity in GaAs quantum dots
Authors: Plaut A. S. , Kash K. , Van der Gaag B. P. , Gozdz A. S. , Harbison J. P. , Florez L. T.
Published: May 2007

We have measured the optical saturation intensity of GaAs quantum dots and have found it to be 50 W/cm2; more than an order of magnitude smaller than that reported for GaAs quantum wells. Compared to such quantum wells, our quantum dots also show a larger amount of saturation, again by more than an order of magnitude. We find that the saturation intensity of our quantum dots depends exponentially on the photoexcitation energy, with greater intensities required for photon energies closer to the bottom of the quantum dot confinement potential.
Elastic turbulence in von Karman swirling flow between two disks
Authors: Burghelea Teodor , Segre Enrico , Steinberg Victor
Published: May 2007

We discuss the role of elastic stress in the statistical properties of elastic turbulence, realized by the flow of a polymer solution between two disks. The dynamics of the elastic stress are analogous to those of a small-scale fast dynamo in magnetohydrodynamics, and to those of the turbulent advection of a passive scalar in the Batchelor regime. Both systems are theoretically studied in the literature, and this analogy is exploited to explain the statistical properties, the flow structure, and the scaling observed experimentally. The following features of elastic turbulence are confirmed experimentally and presented in this paper: (i) The rms of the vorticity (and that of velocity gradients) saturates in the bulk of the elastic turbulent flow, leading to the saturation of the elastic stress. (ii) The rms of the velocity gradients (and thus the elastic stress) grows linearly with Wi in the boundary layer, near the driving disk. The rms of the velocity gradients in the boundary layer is one to two orders of magnitude larger than in the bulk. (iii) The PDFs of the injected power at either constant angular speed or torque show skewness and exponential tails, which both indicate intermittent statistical behavior. Also the PDFs of the normalized accelerations, which can be related to the statistics of velocity gradients via the Taylor hypothesis, exhibit well-pronounced exponential tails. (iv) A new length scale, i.e., the thickness of the boundary layer, as measured from the profile of the rms of the velocity gradient, is found to be relevant for the boundary layer of the elastic stresses. The velocity boundary layer just reflects some of the features of the boundary layer of the elastic stresses (rms of the velocity gradients). This measured length scale is much smaller than the vessel size. (v) The scaling of the structure functions of the vorticity, velocity gradients, and injected power is found to be the same as that of a passive scalar advected by an elastic turbulent velocity field.
Further support for Townsend’s Reynolds number similarity hypothesis in high Reynolds number rough-wall pipe flow
Authors: Kunkel Gary J. , Allen James J. , Smits Alexander J.
Published: May 2007

Measurements of turbulence behavior in high Reynolds number fully developed rough-wall pipe flow are presented. The data are acquired with single-component conventional hot-wire anemometry in the Princeton/ONR Superpipe fitted with a honed rough pipe. Streamwise turbulence intensities, higher-order moments, and spectra are compared with the corresponding results from a previous smooth-wall pipe flow study in the same facility. Accepting the experimental challenges of conducting hot-wire anemometry studies in such a facility, the rough-wall data agree well with the smooth-wall data in the outer region of the flow, strongly supporting Townsend’s Reynolds number similarity hypothesis.