bluuebunny/crossref_metadata_2025 huggingface dataset:
Lichens of the Magnesian Limestone
Authors: Gilbert O. L.
Published: May 2007

The lichen flora of natural outcrops, disused quarries and churchyards in the Magnesian Limestone belt of England, which stretches from Nottingham to Tyneside, is described with reference to 50 sites; 106 taxa were encountered. The lichen flora is compared with that of the Carboniferous Limestone in Derbyshire and found to be distinctive, relating particularly to the abundance of less exacting calcicoles. Lecanora campestris subsp. dolomitica, a lichen widespread at the southern end of the outcrop, is described.
Cell Walls of the Phycobionts Trebouxia and Pseudotrebouxia: Constituents and Their Localization
Authors: König J. , Peveling E.
Published: May 2007

The cell wall composition of several species of the lichen phycobionts Trebouxia and Pseudotrebouxia has been investigated using gas chromatography, thin layer chromatography and infrared absorption spectrophotometry. In addition cell wall components (cellulose, non-cellulosic polysaccharides, sporopollenin, protein) were localized with cytochemical methods at the EM- level. The cell walls of Trebouxia and Pseudotrebouxia consist of several layers. In Trebouxia the inner layer (Si) consists mainly of cellulose, then followed by a non-cellulosic polysaccharide layer (S2), a sporopollenin-layer (S3) and an outer layer consisting again of a non-cellulosic polysaccharide (S4). In addition Trebouxia is surrounded by a sheath (a polysaccharide with species-specific terminal residues). In Pseudotrebouxia the cell wall is similarly constructed compared to Trebouxia, however, the sheath is lacking and the S4 layer contains a polysaccharide with species-specific terminal sugar residues. The role of the different cell wall constituents for the recognition mechanism between the lichen symbionts is discussed.
New or Interesting British Lichens V The Lichenologist
Authors: Coppins B. J. , James P. W.
Published: May 2007

Notes and keys are provided for British members of the Trapeliaceae. The genus Placynthiella Gyelnik is resurrected to accommodate the Lecidea uliginosa group: P. hyporhoda (Th. Fr.) comb, nov., P. icmalea (Ach.) comb, nov., P. oligotropha (Laundon) comb. nov. and P. uliginosa (Schrader) comb. nov. Aphanopsis Nyl. ex P. Sydow is recognized for the single species A. coenosa (Ach.) comb, nov., and attention is drawn to the enigmatic Biatora humida Kullhem. The Lecidea granulosa group is referred to Trapeliopsis, necessitating four new combinations, T. aeneofusca (Flörke ex Flotow) comb, nov., T. flexuosa (Fr.) comb, nov., T. gelatinosa (Flörke) comb. nov. and T. viridescens (Schrader) comb, nov., and the description of one new species, T. pseudogranulosa sp. nov. Special attention is given to sorediate species of Trapelia, including T. corticola sp. nov. and T. placodioides sp. nov.
Studies on The Growth of Lichens I Lobe Formation and the Maintenance of Circularity in Crustose Species
Authors: Hill D.J.
Published: May 2007

The rate of lobe division during thallus enlargement in Xanthoria elegans and Diploicia canescens is considered in geometric terms. The frequency of lobe engulfment by neighbouring lobes was measured, was fitted graphically to a simple equation and was found to result from constant lobe division with thallus size. Values for a constant in the equation and derived from the observed frequency of lobe engulfment provided a measurement of a new morphological parameter: ratio lobe length to width. Greatest departure from circularity in small thalli of D. canescens occurred when thallus size did not permit lobe competition. Increasing lobe engulfment and thallus circularity in larger thalli appeared to be correlated. Circularity in crustose thalli without lobes is discussed with definitions of ‘primary’ and ‘secondary’ areoles.
Macrolichens in Tasmanian Rainforests
Authors: Kantvilas G. , James P. W. , Jarman S. J.
Published: May 2007

96 macrolichens, including 12 new records, are reported for cool temperate rainforests in Tasmania. These species belong mainly to the austral cool temperate element. A descriptive account of the lichen floras from five major rainforest communities is given. Field observations suggest that substrate and light are the most important ecological factors affecting the distribution of lichens in rainforest. Although most species are widespread in Tasmania, large-scale disturbance and the fragmentation of rainforest stands is seen as a threat to their survival.
The Persistence of Cladonia Patches in Closed Heathland Stands
Authors: Hobbs R.J.
Published: May 2007

The inhibitory action of aqueous extracts from detached podetia of heathland Cladonia spp. and leachates from transplanted Cladonia turfs was tested using seeds of Avena fatua, Calluna vulgans and Deschampsia flexuosa. Significant inhibitory effects were found for each species. Further evidence from a field experiment suggests that patches containing a mixture of Cladonia spp. can inhibit germination or establishment of vascular species, probably through both chemical and physical processes, and thus maintain intact lichen patches in otherwise closed heathland stands.
On Succession in A Saxicolous Lichen Community
Authors: Woolhouse M. E. J. , Harmsen R. , Fahrig L.
Published: May 2007

The lichen flora was sampled at each of the five sites on a near-vertical gneiss rock face. The sites were ranked according to the degree ofweathering of the rock surface and were taken to represent different stages in a succession. The succession shows an increase in species richness and diversity over time, although the proportion of the rock face unoccupied by lichens increases at the oldest site. The succession will be driven by allogenic processes, physical weathering of the rock, facilitation, especially the effects of lichens on surface erosion, and by inhibition, through competition for space. At the oldest site mortality of lichen thalli becomes important, continually opening up new areas for recolonization and maintaining community diversity. The succession may be described by four phases: (1) colonization, (2) growth,(3) competition and (4) senescence.
Lichens of the coniston Copper mines
Authors: Purvis O. W. , James P. W.
Published: May 2007

Lichen communities at four sites of copper sulphide mineralization and associated secondary oxidation products are described from an old mining area at Coniston in the English Lake District. Five lichen species new to Britain, Stereocaulon symphycheilum, Lecanora handelii, Rhizocarpon furfurosum, Lecidea atrofulva and L. inops, are briefly described, the last mentioned being a specific indicator of copper mineralization. The species complex, Lecidea auriculata, L. diducens and L. inops, is discussed in some detail. Toninia leucophaeopsis and the non- British Bilimbia tornensis are distinct species and are both referred to the genus Stereocaulon.
Xanthomaculina Hale, A New Lichen Genus in the Parmeliaceae (Ascomycotina)
Authors: Hale M. E.
Published: May 2007

The endemic African lichen Parmelia hottentotta (Ach.) Ach. and related species are placed in a new genus, Xanthomaculina Hale, on the basis of cortical chemistry and a combination of conidial and morphological characters, including umbilicate growth form, presence of cilia and a vaulted cortex.
Glyphopeltis (Lecideaceae), A New Lichen Genus from Southern Africa
Authors: Brusse F.
Published: May 2007

A new saxicolous genus and species, Glyphopeltis eburina Brusse, is described from southern Africa. The genus differs from Lecidea s. lat. in the peltate thallus.
Epilithic Lichens in the Beacon Sandstone Formation, Victoria Land, Antarctica
Authors: Hale M. E.
Published: May 2007

The epilithic lichen flora on the Beacon sandstone formation in Victoria Land consists of seven species: Acarospora gwynniiDodge & Rudolph, Buellia grisea Dodge & Baker, B. pallida Dodge & Baker, Carbonea capsulata (Dodge & Baker) Hale comb, nov., Lecanora fuscobrunnea Dodge & Baker, Leaded cancriformis Dodge & Baker, and L. siplei Dodge & Baker. The typification of the species is given along with descriptions and distribution in Antarctica.
Thallus tip Structure and Matrix Development in Bryoria Fuscescens
Authors: Greenhalgh G. N. , Whitfield A.
Published: May 2007

SEM observations of the surface of branch tips of Bryoria fuscescens, before and after treatment to remove the matrix produced by the cortical hyphae, are described. Cortical hyphae are arranged in a simple, apical bundle, parallel to the long axis of the branch, which becomes, behind the apex, a hollow cylinder containing the algal population. The cortical structure is less complex than that of Usnea subfloridana. Substantial amounts of extracellular matrix are produced and the significance of this is discussed.
Studies In The Lichen Family Pannariaceae II. The Genus Leioderma Nyl
Authors: Galloway D. J. , Jørgensen P. M.
Published: May 2007

The Southern Hemisphere genus Leioderma Nyl. contains seven species: L. amphibolum (Knight) P. M. Jørg & D. Galloway, L. applanatum sp. nov., L. duplication (Mull. Arg.) comb, nov., L. erythrocarpum (Nyl.) comb, nov., L. glabrum sp. nov., L. pycnophorum Nyl., and L. sorediatum sp. nov. The genus has two subgenera (Leioderma, and Fuscoderma subgen. nov.) distinguished by differences in thallus morphology and the structures of asci and ascospores. Leioderma is closely related to Erioderma but differs in thallus habit, structure of cortex and ascus, and chemistry. Leioderma appears to be a Gondwanan genus. A key is given, and details of anatomy, morphology, distribution, ecology, phytogeography and taxonomy are discussed. A new, Lewderma-like, sorediate Parmeliella, P. subgranulata sp. nov., is described from New Zealand, and the related P. granulata Lamb, is recorded from New Zealand for the first time.
Measurement of Intrapopulational Enzyme Variation in Five Species of Epiphytic Lichens
Authors: Fahselt Dianne
Published: May 2007

Thalli of five species of epiphytic lichens were collected from one moribund spruce-fir stand in the Algonquin Highlands in Ontario, Canada. Extracts of all were subjected to isoelectric focusing and stained for activity of 16 enzyme systems. Gels were scored for the presence or absence of individual bands in each enzyme system, and the degree of polymorphism of all detectable enzymes was evaluated using a variability measure developed for use with presence/absence data. Esterase and alkaline phosphatase showed the greatest amount of polymorphism and superoxide dismutase was the least variable enzyme system. The degree of enzyme variability in each of the five species was probably a reflection of its past evolutionary history and bore little relationship to apparent potential for sexual reproduction.
The Identity of ‘Lecidea Cinnabarina’ in the British Isles
Authors: Coppins B. J. , James P. W.
Published: May 2007

Most British collections hitherto identified as Lecidea cinnabarina Sommerf. are shown to belong to either Pertusaria pupillaris (Nyl.) Th. Fr. or to a sterile species tentatively assigned to Schismatomma as S. quercicola Coppins & P. James sp. nov. Notes are also provided on a problematical Pertusaria, resembling P. pupillaris and Lecidea cinnabarina s. str.
A Rock Pool Lichen Community in Northern Transvaal, South Africa: Composition and Distribution Patterns
Authors: Wessels D. C. J. , Büdel B.
Published: May 2007

The distribution patterns of lichens belonging to the family Peltulaceae and procaryotic algae (cyanobacteria) were studied in a rock pool on a sandstone koppie (‘Inselberg’). situated in the mopane savanna of the northern Transvaal. The co-dominant lichen species along the wall of the pool were: Peltula clavata (Krempelh.) Wetmore, P. euploca (Ach.) Poelt ex Pisut, P. obscurans (Nyl.) Gyelnik, and P. placodizans (Zahlbr.) Wetmore. The cyanobacteria Gloeocapsa sanguinea (Ag.) Kütz. emend. Jaag, Plectonema tomasinianum Gom. ex Gom., Rivularia sp., Scytonema sp. and Tolypothrix sp. grew epilithically between the lichen thalli. Unicellular species of the genus Chroococcidiopsis Geitler or Myxosarcina Printz occurred cryptoendolithically. The distribution patterns of several lichen species are presented and statistical tests reveal distinct correlations of the habitats of some species with light levels and water supply; e.g. the olive-green P. placodizans preferred the fully exposed situation near and along the rim of the rock pool; the black species P. clavata was restricted to areas next to the water level.
Microfaunal communities associated with epiphytic lichens in Belfast
Authors: Roberts D. , Zimmer D.
Published: May 2007

The composition and richness of the microfauna on lime trees was surveyed in relation to the distribution and cover of lichens in Belfast. Parameters used to help interpret the results included distance from the city centre and available data on air quality. The percentage epiphyte cover on the trunks of lime trees was significantly correlated with distance from the city centre whereas that on tree bases as not. In contrast, the number of microfaunal species revealed strong positive correlations with distance for both the bases and the trunks of trees. Most of this increase in microfaunal species richness towards rural areas was due to protistans which are thus proposed as useful bioindicators of air pollution. The total species richness of fauna showed slight negative correlation with smoke but not SO2 levels.
A Second Lichen-Forming Species of Cheiromycina From Austria
Authors: Hawksworth D. L. , Poelt J.
Published: May 2007

A second species of the lichen-forming hyphomycete genus Cheiromycina B. Sutton, C. petri D. Hawksw. & Poelt sp.nov., is described from old Betula bark in Steiermark, Austria. It differs from C. flabelliformis B. Sutton in thallus colour, the more compact blue-grey non-eroding sporodochia, the very tightly dichotomously branched conidia, and in having much shorter terminal branches.
Koerberiella Wimmeriana (Lecanorales, Porpidiaceae) and Its Lichenicolous Fungi
Authors: Rambold G. , Hertel H. , Triebel D.
Published: May 2007

Lecanora creatina Norman ex Th. Fr. and Lecanora leucophyma Leighton were found to be synonyms of Koerberiella wimmeriana (Körber) B. Stein; both represents the isidiate growth form of the species. The lichenicolous fungi Arthonia almquistii Vainio, Endococcus propinquus (Körber) D. Hawksw. and Sagediopsis aquatica (B. Stein) Triebel occurs on K. wimmeriana. All are described in detail.
The Occurrence of Copper-Psoromic Acid in Lichens From Cupriferous Substrata
Authors: Purvis O. William , Elix John A. , Gaul Kim L.
Published: May 2007

The localization of psoromic acid and copper in partly green, copper-rich specimens of Lecidella bullata and Tephromela testaceoatra collected in Norway was studied by optical microscopy, scanning electron microscopy, and electron probe microanalysis. Infrared absorption spectroscopy of lichen material and of a synthetic copper-psoromic acid complex, and the other techniques, provide evidence that complexing of copper by psoromic acid occurs within specific areas of these lichens and this leads to their unusual colouration. In contrast, a specimen of copper-rich Lecanora cascadensis, which contains psoromic and usnic acids, does not contain such a complex. From the evidence obtained it is suggested that taxonomists should pay attention to the impact of rock and lichen chemistry on the appearance of lichen thalli.
Artificial Resynthesis of Thalli of the Cyanobacterial Lichen Peltigera Praetextata Under Laboratory Conditions
Authors: Stocker-Wörgötter Elfie , Türk Roman
Published: May 2007

The resynthesis of foliose thalli of the cyanobacterial lichen Peltigera praetextata was achieved on a soil substratum under laboratory conditions. On agar plates mycelia formation by this lichen fungus only occurred when a sufficient number of photobiont cells was present. Resynthesis on agar was restricted to the formation of loose algal-fungal associations, which showed no lichen-like structures. Early resynthesis stages were formed on soil only after a very long lag phase of 2–3 months. First soredia-like stages (resynthesis products of fungal hyphae and cyanobacteria) appeared, later tissue clumps and thallus primordia differentiated. Welldeveloped lichen thalli with rhizines that resembled young thalli from the natural environment were formed after an incubation time of 2–3 years.
The Brown Parmelia Type Specimens of A. N. Oxner
Authors: Esslinger Theodore L.
Published: May 2007

The morphology and chemistry of the type specimens for the four species of brown Parmelia described by A. N. Oxner have been studied. The correct name for the widely distributed Northern Hemisphere taxon, now generally known as Melanelia substygia (Räsänen) Essl. (Parmelia substygia Räsänen), is now M. tominii (Oxner) Essl. Parmelia borisorum Oxner and Parmelia altaica Oxner are also synonyms of M. tominii. Parmelia teretiuscula Oxner is a synonym of Melanelia stygia (L.) Essl.
Factors of Importance to Some Lichen Species of Deciduous Broad-Leaved Woods in Southern Sweden
Authors: Gustafsson Lena , Fiskesjö Anneli , Ingelög Torleif , Petterssonj Börje , Thor Göran
Published: May 2007

A number of lichen species presumed to prefer broad-leaved, deciduous woodlands of long continuity were recorded in 101 stands with different histories and in different successional stages in southern Sweden. Of 19 recorded species, Arthonia vinosa, Calicium adspersum, C. salicinum, Lobaria pulmonaria, and Mycobilimbia sabuletorum occurred in ten stands or more. Habitat variables that indicate occurrence of natural forest conditions were registered and also factors of stand and site quality used in forest surveys. The lichen species recorded were significantly correlated with the presence of large, old, deciduous, broad-leaved trees. Deciduous, broadleaved woods with many large old trees are at present being rapidly transformed into forest plantations. The recorded lichen species will decrease unless the woods are protected or have modified management.
Lepraria in the British Isles
Authors: Laundon Jack R.
Published: May 2007

The first modern taxonomic classification of the species of Lepraria is presented. Chemistry is the most important character used to separate the morphologically similar, but distinct, sterile taxa. Nine species are recorded from the British Isles, of which L. eburnea and L. frigida are new to science. Lepraria nivalis is a new name for Crocynia murorum B. de Lesd., and L. caesioalba (B. de Lesd.) Laundon a new combination. Two species, L. incana (L.) Ach. and L. lobificans Nyl., are especially common and are dominant on shaded bark and rock. Twenty-eight lichens reported as Lepraria belong elsewhere or require further study. The combination Leproloma cacuminum (Massal.) Laundon is made to replace the name L. angardianum.
New Species and Combinations in The Lichen Flora of Great Britain and Ireland
Authors: Coppins B. J. , Jamesj P. W. , Hawksworth D. L.
Published: May 2007

In support of the Lichen Flora of Great Britain and Ireland, 22 new combinations are made, and the following new species are described: Bacidia subcircumspecta Coppins, B. viridifarinosa Coppins & P. James, Coccotrema citrinescens P. James & Coppins, Eopyrenula avellanae Coppins, E. grandicula Coppins, E. septemseptata Coppins, Fuscidea hibernica P. James & Poelt, Graphis alboscripta Coppins & P. James, Lecidea doliiformis Coppins & P. James, Melaspilea atroides Coppins, Opegrapha fumosa Coppins & P. James, and O. multipuncta Coppins & P. James.
Notes on Polysporina Vězda, with a Description of a New Species from Tasmania.
Authors: Kantvilas Gintaras
Published: May 2007

The new species,Polysponna terricolaKantvilas from south-eastern Tasmania, is described and compared to other species in the genus. It is well characterized by a range of morphological, anatomical and ecological characters, especially by the presence of oil paraphyses and oil droplets in the hymenium, features unknown in other members of the genus. Species ofPolysporinaare best separated by the following characters: size and morphology of the apothecia, size of ascospores, thickness of paraphyses and height of the hymenium. The combinationsP. ferniginea(Lettau) M. Steiner andP. pusilla(Anzi) M. Steiner are validated. A key to the taxa studied is provided.
NOMOS AND PHUSIS IN DEMOCRITUS AND PLATO
Authors: Taylor C. C. W.
Published: May 2007

This essay explores the treatment of the relation between nature
(phusis) and norm or convention (nomos) in Democritus
and in certain Platonic dialogues. In his physical theory Democritus draws
a sharp contrast between the real nature of things and their
representation via human conventions, but in his political and ethical
theory he maintains that moral conventions are grounded in the reality of
human nature. Plato builds on that insight in the account of the nature of
morality in the myth in the Protagoras. That provides material
for a defense of morality against the attacks by Callicles in the
Gorgias and Thrasymachus and Glaucon in the Republic,
all of whom seek to use the nature-convention contrast to devalue
morality.
FREEDOM, LIBERALITY, AND LIBERTY IN PLATO'S LAWS
Authors: Laks André
Published: May 2007

This essay aims at establishing that the word “free”
(eleutheros) and related terms are used by Plato in the
Laws in two main senses. There is, first, the constitutional
meaning of “freedom” which is put to work in book 3 in order
to analyze moderately good and degenerate forms of historical
constitutions. Strikingly enough, this meaning does not play any
subsequent role in the shaping of the Platonic constitution itself—a
fact which requires some kind of explanation. There is, then, scattered
throughout the work, the behavioral meaning of “freedom”
according to which the citizens of Magnesia, who are free in the sense
that they are free men, are supposed to behave as such and to be educated
accordingly, that is as “gentlemen.” One important aspect here
is that a free education will appeal to rationality. The philosophically
interesting fact, however, is that there appears to be no intrinsic link
for Plato between freedom and rationality, as we might expect on the basis
of modern philosophical assumptions whereby freedom is grounded on
rationality. Rather, freedom is the condition for exercising rationality,
because this exercise takes time. True, there is in the Laws a unique
occurrence of yet another conception of “freedom” according to
which one is free when one's reason masters one's desires. One might
speculate why Plato did not develop this specific conception of freedom,
which is in some sense closer to some modern views about liberty, as is
shown, for example, from I. Berlin's concept of “positive
liberty.”
Carbon dioxide and oxygen fluxes in the Southern Ocean: Mechanisms of interannual variability
Authors: Verdy A. , Dutkiewicz S. , Follows M. J. , Marshall J. , Czaja A.
Published: May 2007

We analyze the variability of air‐sea fluxes of carbon dioxide and oxygen in the Southern Ocean during the period 1993–2003 in a biogeochemical and physical simulation of the global ocean. Our results suggest that the nonseasonal variability is primarily driven by changes in entrainment of carbon‐rich, oxygen‐poor waters into the mixed layer during winter convection episodes. The Southern Annular Mode (SAM), known to impact the variability of air‐sea fluxes of carbon dioxide, is also found to affect oxygen fluxes. We find that El Niño–Southern Oscillation (ENSO) also plays an important role in generating interannual variability in air‐sea fluxes of carbon and oxygen. Anomalies driven by SAM and ENSO constitute a significant fraction of the simulated variability; the two climate indices are associated with surface heat fluxes, which control the modeled mixed layer depth variability. We adopt a Lagrangian view of tracers advected along the Antarctic Circumpolar Current (ACC) to highlight the importance of convective mixing in inducing anomalous air‐sea fluxes of carbon dioxide and oxygen. The idealized Lagrangian model captures the principal features of the variability simulated by the more complex model, suggesting that knowledge of entrainment, temperature, and mean geostrophic flow in the mixed layer is sufficient to obtain a first‐order description of the large‐scale variability in air‐sea transfer of soluble gases. Distinct spatial and temporal patterns arise from the different equilibration timescales of the two gases.
Restriction of convective depth in the Weddell Sea
Authors: Akitomo K.
Published: May 2007

The depth open‐ocean convection can reach around Maud Rise in the Weddell Sea is estimated based on the entrainment assumption using hydrographic data obtained in winter 1986 during which no distinct polynya was observed. While the water column is stable at all CTD stations when observed, additional cooling makes the mixed layer water heavier than the underlying water at any depth in an adiabatic sense. However, convective plume cannot reach the ocean bottom since it loses positive density anomaly due to thermobaricity by entraining the Warm Deep Water (WDW) on its downward way. The deeper convection is located over Maud Rise where the maximum temperature of the WDW, θmax, is about 0.5°C while the shallower one in the warm water cell region where θmax is more than 1.0°C. The mean convective depth is much shallower than the ocean depth and the ventilated depth during the Weddell Polynya years (3∼4 km).
The inositol 1,4,5-trisphosphate receptor (Itpr) gene family in Xenopus: identification of type 2 and type 3 inositol 1,4,5-trisphosphate receptor subtypes
Authors: Zhang Dan , Boulware Michael J. , Pendleton Matthew R. , Nogi Taisaku , Marchant Jonathan S.
Published: May 2007

Studies in the Xenopus model system have provided considerable insight into the developmental role of intracellular Ca2+ signals produced by activation of IP3Rs (inositol 1,4,5-trisphosphate receptors). However, unlike mammalian systems where three IP3R subtypes have been well characterized, our molecular understanding of the IP3Rs that underpin Ca2+ signalling during Xenopus embryogenesis relate solely to the original characterization of the ‘Xenopus IP3R’ cloned and purified from Xenopus laevis oocytes several years ago. In the present study, we have identified Xenopus type 2 and type 3 IP3Rs and report the full-length sequence, genomic architecture and developmental expression profile of these additional IP3R subtypes. In the light of the emerging genomic resources and opportunities for genetic manipulation in the diploid frog Xenopus tropicalis, these data will facilitate manipulations to resolve the contribution of IP3R diversity in Ca2+ signalling events observed during vertebrate development.
Specific Language Impairment in French-Speaking Children: Beyond Grammatical Morphology
Authors: Thordardottir Elin T. , Namazi Mahchid
Published: May 2007

Purpose

Studies on specific language impairment (SLI) in French have identified specific aspects of morphosyntax as particularly vulnerable. However, a cohesive picture of relative strengths and weaknesses characterizing SLI in French has not been established. In light of normative data showing low morphological error rates in the spontaneous language of French-speaking preschoolers, the relative prominence of such errors in SLI in young children was questioned.

Method

Spontaneous language samples were collected from 12 French-speaking preschool-age children with SLI, as well as 12 children with normal language development matched on age and 12 children with normal language development matched on mean length of utterance. Language samples were analyzed for length of utterance; lexical diversity and composition; diversity of grammatical morphology and morphological errors, including verb finiteness; subject omission; and object clitics.

Results

Children with SLI scored lower than age-matched children on all of these measures but similarly to the mean length of utterance–matched controls. Errors in grammatical morphology were very infrequent in all groups, with no significant group differences.

Conclusion

The results indicate that the spontaneous language of French-speaking children with SLI in the preschool age range is characterized primarily by a generalized language impairment and that morphological deficits do not stand out as an area of particular vulnerability, in contrast with the pattern found in English for this age group.
Mean-curvature flow and quasilocal mass for 2-surfaces in Hamiltonian general relativity
Authors: Anco Stephen C.
Published: May 2007

A family of quasilocal mass definitions that includes as special cases the Hawking mass and the Brown-York “rest mass” energy is derived for spacelike 2-surfaces in space-time. The definitions involve an integral of powers of the norm of the space-time mean-curvature vector of the 2-surface, whose properties are connected with apparent horizons. In particular, for any spacelike 2-surface, the direction of mean curvature is orthogonal (dual in the normal space) to a unique normal direction in which the 2-surface has vanishing expansion in space-time. The quasilocal mass definitions are obtained by an analysis of boundary terms arising in the gravitational ADM Hamiltonian on hypersurfaces with a spacelike 2-surface boundary, using a geometric time flow chosen proportional to the dualized mean-curvature vector field at the boundary surface. A similar analysis is made choosing a geometric rotational flow given in terms of the twist covector of the dual pair of mean-curvature vector fields, which leads to a family of quasilocal angular momentum definitions involving the squared norm of the twist. The large sphere limit of these definitions is shown to yield the ADM mass and angular momentum in asymptotically flat space-times, while at apparent horizons a quasilocal version of the Gibbons-Penrose inequality is derived. Finally, some results concerning positivity are proved for the quasilocal masses, motivated by consideration of spacelike mean-curvature flow of 2-surfaces in space-time.
Ultrafast photoinduced electron transfer from dimethylaniline to coumarin dyes in sodium dodecyl sulfate and triton X-100 micelles
Authors: Ghosh Subhadip , Mondal Sudip Kumar , Sahu Kalyanasis , Bhattacharyya Kankan
Published: May 2007

The primary steps of photoinduced electron transfer (PET) from N,N-dimethylaniline (DMA) to five coumarin dyes are studied in an anionic micelle [sodium dodecyl sulfate (SDS)] and a neutral micelle [triton X-100 (TX-100)] using femtosecond upconversion. The rate of PET in micelle is found to be highly nonexponential. In both the micelles, PET displays components much faster (∼10ps) than the slow components (180–2900ps) of solvation dynamics. The ultrafast components of electron transfer exhibit a bell-shaped dependence on the free energy change. This is similar to Marcus inversion. The rates of PET in TX-100 and SDS micelle are, in general, faster than those in cetyltrimethylammonium bromide (CTAB) micelle. In the SDS and TX-100 micelle, the Marcus inversion occurs at −ΔG0 ∼0.7eV which is lower than that (∼1.2eV) in CTAB micelle. Possible causes of variation of PET in different micelles are discussed.
Barrier discharges in cellular polypropylene ferroelectrets: How do they influence the electromechanical properties?
Authors: Qiu Xunlin , Mellinger Axel , Wegener Michael , Wirges Werner , Gerhard Reimund
Published: May 2007

Ferroelectrets (i.e., charged cellular polymers) are rendered piezoelectric by means of barrier discharges inside the air-filled voids. The light emission from barrier discharges in cellular polypropylene ferroelectrets was quantitatively studied. Light emission typically occurs above a threshold voltage of 3 kV and then significantly increases with the applied voltage. Time-resolved images reveal discharge processes in individual voids. In addition, a second “back discharge” emission is observed when the voltage is reduced to zero. The buildup of the “effective polarization” in cellular PP ferroelectrets was studied by an acoustic method and dielectric resonance spectroscopy. A polarization-voltage (P-V) hysteresis loop was obtained by analyzing the data with an existing model for the piezoelectric d33 coefficient of ferroelectrets, from which a threshold charging voltage of 3 kV and the back barrier discharges were confirmed and a zero-field “effective polarization” of 0.5 mC/m2 was determined. However, charge densities of up to 2 mC/m2 were measured under an applied bias voltage, leading to the conclusion that the observed back discharges destroy a significant fraction of the effective charge density.
On the effective temperature concept in the problem of laminar vortex shedding behind a heated circular cylinder
Authors: Fedorchenko Alexander I. , Trávníček Zdenek , Wang An-Bang
Published: May 2007

Prediction of the nonisothermal vortex shedding based on the effective temperature Teff=T∞+c(TW−T∞) is always linked with the specific material properties of the working fluid, while a desirable universal prediction is unknown. Here we show that the thermal effect in diluted gases, where cylinder heating stabilizes wake flow (thus delaying the onset of vortex shedding), can be quantified in the extraordinary compact form of the proportionality between the critical Reynolds number ReC,∞ and the dimensionless film temperature Tf*. The theoretically derived c value for any dilute gas is related to an exponent n of the kinematic viscosity-temperature power law by a simple formula c=(2n)−1. The universal character of the proportionality has been proven; the linear increase of the critical Reynolds number is independent of the specific material properties for all diluted gases.
Crown behavior in drop impact on wet walls
Authors: Mukherjee Shiladitya , Abraham John
Published: May 2007

Axisymmetric computations of drop impingement on walls with a pre-existing liquid film are reported. A high-density-ratio lattice-Boltzmann model is employed for the computations. The focus of the work is on the behavior of the crown that forms as a result of impingement. When the crown forms, its base radius and height grow with time. Subsequently, it may break up. The influence of wall liquid film thickness, and surrounding gas density and viscosity on crown behavior is investigated. When the liquid film is thin, it is observed that the rate of increase of the radius and height of the crown increases with increasing film thickness. The breakup of the crown is delayed. On thicker films, the rate of increase decreases with increasing film thickness, but the breakup is further delayed. When either gas density or viscosity is increased, the rate of increase of the radius and height decreases and breakup is delayed.
Functionalizing Zn- and O-terminated ZnO with thiols
Authors: Sadik Patrick W. , Pearton Stephen J. , Norton David P. , Lambers Eric , Ren Fan
Published: May 2007

We have investigated the adsorption of dodecanethiol on zinc- and oxygen-terminated ZnO surfaces. Strong enthalpic adsorption is demonstrated by the stability of sulfur on both ZnO surfaces for temperatures up to 400°C. The minimal presence of the S 2p3∕2 170eV peak suggests absorption of the sulfur as an unoxidized thiol. The results indicate a higher surface coverage of the thiol on the zinc-terminated surface. Evidence from reflection high energy electron diffraction measurements for the surface ordering after thiol treatment of the oxygen-terminated ZnO surface suggests that the dodecanethiol molecules can adsorb in a highly ordered manner. These results further open the possibility for biofunctionalization of ZnO for biosensing applications.
Propagating double layers in electronegative plasmas
Authors: Meige A. , Plihon N. , Hagelaar G. J. M. , Boeuf J.-P. , Chabert P. , Boswell R. W.
Published: May 2007

Double layers have been observed to propagate from the source region to the diffusion chamber of a helicon-type reactor filled up with a low-pressure mixture of Ar∕SF6 [N. Plihon et al., J. Appl. Phys. 98, 023306 (2005)]. In the present paper the most significant and new experimental results are reported. A fully self-consistent hybrid model in which the electron energy distribution function, the electron temperature, and the various source terms are calculated is developed to investigate these propagating double layers. The spontaneous formation of propagating double layers is only observed in the simulation for system in which the localized inductive heating is combined with small diameter chambers. The conditions of formation and the properties of the propagating double layers observed in the simulation are in good agreement with that of the experiment. By correlating the results of the experiment and the simulation, a formation mechanism compatible with ion two-stream instability is proposed.
Dynamics of polymer melts confined by smooth walls: Crossover from nonentangled region to entangled region
Authors: Li Yijie , Wei Dongshan , Han Charles C. , Liao Qi
Published: May 2007

The authors present the results of molecular dynamics simulations of polymer films confined by smooth walls. Simulations were performed for a wide range of chain lengths covering both nonentangled and entangled regions, as well as film thicknesses ranging from the order of unperturbed chain size to the bulk state. The simulation results for the chain size dependence on the film thickness are compared with the prediction of the scaling model. By measuring the correlation function of the end-to-end vectors, we have determined the relaxation time of confined polymer chains in different entangled states. It is shown that there is a minimum in the relaxation time of long chains when decreasing the film thickness, which is partially due to the confinement-induced disentanglement effect.
Optical properties of sputtered amorphous beryllium nitride thin films
Authors: Khoshman J. M. , Khan A. , Kordesch M. E.
Published: May 2007

The optical properties of amorphous beryllium nitride (a-Be3N2) thin films deposited on Si (100) at temperature <50°C using reactive rf sputtering deposition were examined in the wavelength range of 280–1600nm. X-ray diffraction of the films showed no structure, suggesting the Be3N2 films grown on the Si (100) substrates are amorphous. The thicknesses and optical constants of the films were derived from variable-angle spectroscopic ellipsometry measurements using the Cauchy-Urbach model. Refractive indices and extinction coefficients of the films were determined to be in the range n=1.98–2.28 and κ=0.0002–0.08, respectively. Analysis of the absorption coefficient shows the optical absorption edge of a-Be3N2 films to be 4.12±0.01eV. These values were in excellent agreement with the photoluminescence measurements (4.18eV). The surface morphology was characterized by atomic force microscopy. The surfaces of the films were very smooth and their average roughnesses were measured to be in the range of 0.36–2.4nm. An effective medium approximation model of 50% Be3N2 and 50% voids was used in the ellipsometric fitting procedure. The spectral dependence of transmissivity of the films was investigated at different angles of incidence (20°–80°). The a-Be3N2 films shown high transmissivity (80%–99%) in the visible and near infrared regions.
Tagging multiphoton ionization events by two-dimensional photoelectron spectroscopy
Authors: de Groot Mattijs , Broos Jaap , Buma Wybren Jan
Published: May 2007

Two-dimensional photoelectron spectroscopy has been used to supply process-specific labels to multiphoton ionization events. Employing these tags, the authors can construct excitation and photoelectron spectra along predefined excitation routes in the neutral manifold and ionization routes to the ionic manifold from one single two-dimensional photoelectron spectrum. These results offer a novel way to elucidate the vibronic and dynamic properties of excited and ionic states.
First ultraviolet absorption band of methane: An ab initio study
Authors: van Harrevelt Rob
Published: May 2007

Quantum mechanical calculations of the cross sections for photodissociation of CH4 and CD4 in the 1t2→3s band are presented. The potential energy surfaces for the three states correlating with the 1T21 state at tetrahedral geometries are calculated. The elements of the (3×3) matrix representing the electronic Hamiltonian in the diabatic basis are expanded in powers of nuclear coordinates, up to the second order. The expansion coefficients are based on accurate multireference configuration interaction calculations. The electronically nonadiabatic dynamics is treated with the multiconfiguration time-dependent Hartree approach. All nine internal degrees of methane are included in the quantum dynamics simulations. The calculated cross section agrees well with experiment. Semiclassical calculations using the reflection principle suggest that the peaks in the spectrum correspond to the three adiabatic electronic states correlating with the 1T21 state at Td geometries. However, the non-Born-Oppenheimer terms in the Hamiltonian have a strong effect on the positions of the peaks in the absorption spectrum. The results of semiclassical calculations, which neglect these terms, are therefore quite different from the accurate quantum results and experiment.
In situ observation of Zn-induced etching during CdSe quantum dot formation using time-resolved ellipsometry
Authors: Kruse Carsten , Gartner Mariuca , Gust Arne , Hommel Detlef
Published: May 2007

A combined segregation and desorption process has been observed in situ by ellipsometry in real-time during overgrowth of a CdSe layer by a ZnSe cap layer using migration enhanced epitaxy. This segregation enhanced etching of CdSe during Zn deposition is known to play an important role in the formation process of CdSe quantum dots. The time-resolved ellipsometry data can be fitted assuming a rapid thickness reduction of about 68% of the CdSe layer, consistent with results obtained by high-resolution x-ray diffraction after growth. Furthermore, a significant change in growth rate during deposition of CdSe has been observed.
Contribution of water vapor to slider air-bearing pressure in hard disk drives
Authors: Ma Yansheng , Liu Bo
Published: May 2007

Water vapor in humid air contributes to slider air-bearing pressure in a totally different way from that of dry air. Water vapor pressure keeps constant in slider-disk interface and is identical to the water vapor pressure outside the interface. The simulated slider flying height and attitude in humid air are different from that in dry air and the higher the relative humidity the bigger the differences.
Transparent metallic Sb-doped SnO2 nanowires
Authors: Wan Qing , Dattoli Eric N. , Lu Wei
Published: May 2007

The authors report the growth and characterization of single-crystalline, degenerately Sb-doped SnO2 (SnO2:Sb) nanowires. The in situ doped SnO2:Sb nanowires are transparent conductors with resistivities down to 4.1×10−4Ωcm and failure-current densities up to 2.1×107A∕cm2. High carrier concentrations (>1020cm−3) and minimal environmental effects were also observed and attributed to effective Sb doping. The SnO2:Sb nanowires can be obtained at large quantities using a low-cost vapor transport method and may provide a suitable alternative to indium tin oxide as transparent conducting oxide materials. Field emission devices with SnO2:Sb nanowire cathodes and anodes exhibited an ultralow turn-on voltage of 2V.
Thermodynamic properties and interfacial layer characteristics of HfO2 thin films deposited by plasma-enhanced atomic layer deposition
Authors: Kim Inhoe , Kuk Seoungwoo , Kim Seokhoon , Kim Jinwoo , Jeon Hyeongtag , Cho M.-H. , Chung K.-B.
Published: May 2007

The thermodynamic properties and interfacial characteristics of HfO2 thin films that were deposited by the direct plasma atomic layer deposition (DPALD) method are investigated. The as-deposited HfO2 films that were deposited by the DPALD method show crystallization of the HfO2 layers, which initiates at approximately the 35th cycle (about 2.8nm) of the DPALD process. Medium-energy ion scattering analysis reveals that the direct O2 plasma causes a compositional change in the interfacial layer as the process progresses. With an increase in the number of process cycles, the Si content decreases and the O content increases at that position, so that the HfO2-like Hf-silicate layer is formed on top of the interfacial layer. The enhanced physical reactivity of the oxygen ions in the direct plasma and the Hf-silicate layer may be the driving forces that accelerate the early crystallization of the HfO2 layer in the DPALD process in the as-deposited state.
Contrast in transmission spectroscopy of a single quantum dot
Authors: Gerardot B. D. , Seidl S. , Dalgarno P. A. , Warburton R. J. , Kroner M. , Karrai K. , Badolato A. , Petroff P. M.
Published: May 2007

The authors perform transmission spectroscopy on single quantum dots and examine the effects of a resident carrier’s spin, the incident laser spot size, polarization, and power on the experimental contrast. They demonstrate a factor of 5 improvement in the maximum contrast by using a solid immersion lens to decrease the spot area. This increase yields a maximum signal to noise ratio of ∼2000Hz−1∕2, which will allow for megahertz detection frequencies. The authors anticipate that this improvement will allow further investigation of spectral fluctuation and open up the feasibility for an all-optical readout of an electron spin in a quantum dot.
Surface recombination velocity reduction in type-II InAs∕GaSb superlattice photodiodes due to ammonium sulfide passivation
Authors: Li Jian V. , Chuang Shun Lien , Aifer Edward , Jackson Eric M.
Published: May 2007

The surface recombination velocity (SRV) of minority electrons in a type-II InAs∕GaSb superlattice photodiode is quantitatively investigated using the electron beam induced current technique and its value used to evaluate the effects of two different passivation methods. Before passivation, the SRV was determined to be (5.0±0.2)×104cm∕s. The SRVs of two samples passivated at room temperature are compared with that of the unpassivated sample. One passivation method, using a neutralized (NH4)2S solution for 60min, reduces the SRV by a factor of 2. The other passivation method, using 4% (NH4)2S solution for 30min, reduces the SRV by more than one order of magnitude.
Interaction of dislocations with vacancies in silicon: Electronic effects
Authors: de Araýýjo M. M. , Justo J. F. , Nunes R. W.
Published: May 2007

The authors report on an ab initio investigation of the interaction of vacancies with the core of 90° partial dislocation in silicon. For the single-period and the double-period core reconstructions, they find the vacancy formation energies at the core sites to be lower than in the crystalline environment. Moreover, they find that the vacancy-dislocation coupling does not change the U-negative nature of a vacancy in silicon, but leads to quantitative changes in the relative stability of different charge states, as the Fermi level sweeps the electronic band gap in this material.
Highly dispersive thermo-optical properties of gold nanoparticles
Authors: Palpant Bruno , Rashidi-Huyeh Majid , Gallas Bruno , Chenot Stéphane , Fisson Serge
Published: May 2007

The experimental study of the effect of temperature on the complex optical response of matrix-embedded noble metal nanoparticles has been carried out. A thin silica film containing gold nanoparticles with 7% volume fraction has been elaborated. Its thermo-optical refraction and absorption coefficients have then been extracted from temperature-dependent spectroscopic ellipsometry measurements in the visible range. The results, in agreement with our theoretical approach, exhibit strong dispersion, with amplitude and sign changes due to the local electromagnetic field enhancement associated with the surface plasmon resonance in gold nanoparticles.