bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nontrivial carrier recombination dynamics and optical properties of over‐excited GaN/AlN quantum dots
Authors: Kalliakos S. , Bretagnon T. , Lefebvre P. , Juillaguet S. , Taliercio T. , Guillet T. , Gil B. , Grandjean N. , Damilano B. , Dussaigne A. , Massies J. 
Published: September 2004

AbstractWe analyze the low temperature photoluminescence properties of two multi‐layer stacking of GaN/AlN quantum dots. We report drastic differences of linewidths between continuous wave and time‐resolved photoluminescence experiments. After the pulsed excitation, time‐resolved photoluminescence reveals a substantial red shift of the line, which keeps a fairly constant width. In continuous wave experiments, the screening of internal electric fields by accumulation of e–h pairs in quantum dot planes induces a blue‐shift. For samples with large number of quantum dot planes an unexpected narrowing of the emission line is observed when the laser intensity is increased. We assign the observed behaviors of energies and linewidths to the contributions of the in‐depth decrease of the degree of excitation of the different planes. Our interpretation is supported by the use of a model based on a self‐consistent solution of the Schrödinger and Poisson equations within the envelope function approximation. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural and optical properties of rare‐earth doped quantum dots grown by plasma‐assisted MBE
Authors: Hori Y. , Andreev T. , Jalabert D. , Biquard X. , Monroy E. , Tanaka M. , Oda O. , Dang Le Si , Daudin B. 
Published: September 2004

AbstractWe demonstrate Eu, Tm and Er doping of GaN quantum dots. In Er‐doped samples, two very sharp blue lines were observed. These lines were dominant over the green lines reported in the case of Er‐doped GaN thick layers. However, intensities were very low in comparison with Eu‐doped and Tm‐doped GaN QDs. Intense blue emission from Tm‐doped GaN QDs was observed. Temperature‐dependent photoluminescence was studied, and the intensity only decreased to 27% between room temperature and 10 K. Structural studies on Tm‐doped samples showed that the kinetic role of Tm atoms was different from that of Eu atoms. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermal analysis of GaN‐based LEDs using the finite element method and unit temperature profile approach
Authors: Lee Tae Hee , Kim Lan , Hwang Woong Joon , Lee C. C. , Shin Moo Whan 
Published: September 2004

AbstractThis paper reports on the thermal modelling of GaN‐based LEDs. The theoretical calculation was made by combining an analytical simulation employing the Unit Temperature Profile Approach (UTPA) and Finite Element Method (FEM). An interfacing process was made by the optimization of the modelling input parameters used in the analytical simulator. The calculated temperatures of the LED chip inside the epoxy package was compared with the experimentally measured data and the optimized heat transfer coefficients were extracted. The extracted parameters were implemented into the numerical thermal calculation of the package surface using FEM. By the effective interfacing process between the two modelling tools, it is demonstrated that the analytical simulator can be utilized for the accurate prediction of the surface temperatures of LED packaging with non‐flat surface. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron beam induced light emission from the polythiophene derivative/ITO structure
Authors: Panin Gennady N. , Kang Tae Won , Lee Haiwon 
Published: September 2004

AbstractLight emission from a poly‐[3‐(2‐benzotriazolo)‐ethylthiophene]/indium tin oxide (PBET/ITO) structure under electron beam excitation was investigated. Two peaks at 580 nm (green) and 620 nm (orange) are observed under low excitation. An ultraviolet (UV) emission centered at 347 nm appeared under high current excitation. The ratio of the UV/green‐orange band intensities increases with an increase of the current density and with a decrease of temperature. Stimulated emission and lasing from the polythiophene derivative structure are observed at high current density. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Impurity band in magnesium‐doped GaN layers grown by metalorganic chemical vapor deposition
Authors: Kang D. S. , Cheong M. G. , Lee S.‐K. , Suh E.‐K. , Hong C.‐H. , Lee H. J. 
Published: September 2004

AbstractInGaN/GaN quantum well light emitting diodes (LEDs) were grown with p‐GaN layers of varied Mg impurity content. As the concentration of Mg impurity increases, the hole concentration increases up to a critical Mg impurity density and then decreases with further increase of the impurity. In this work, it is proposed that the accepters form the impurity band and that the band behavior with Mg content variation is attributed to the properties of the p‐GaN layer and the p‐layer effect on the I–V characteristics of LED. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Strong Eu emission of annealed Y2O3:Eu nanotube and nano‐sized crystals
Authors: Sekita Masami , Iwanaga Kenichi , Hamasuna Tomomi , Mohri Shinji , Uota Masafumi , Yada Mitsunori , Kijima Tsuyoshi 
Published: September 2004

AbstractWe have observed a drastic increase of the Eu3+ emission intensity by annealing nanotubes and nano‐sized hexagonal‐mesostructured crystals of the Y2O3:Eu system together with bulk samples. It is found that there are three Eu3+ sites in all samples. Stark splitting schemes are proposed for the three homogeneous sites. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis of Yttria‐Based Crystalline and Lamellar Nanostructures and their Formation Mechanism
Authors: Pinna Nicola , Garnweitner Georg , Beato Pablo , Niederberger Markus , Antonietti Markus 
Published: September 2004

AbstractA nonaqueous synthetic route for the preparation of a regular crystalline yttria mesostructure is presented. The reaction between yttrium alkoxides and benzyl alcohol results in the formation of a highly ordered lamellar nanocomposite consisting of yttria layers with a confined thickness of about 0.6 nm, separated from each other by organic layers of intercalated benzoate molecules. Doping with europium leads to strong red luminescence. The nanostructure formation proceeds via two reactions. A CC bond formation occurs between benzyl alcohol and the isopropanolate ligand. At the same time, yttrium oxide catalyzes two low‐temperature hydride‐transfer reactions to form benzoic acid and toluene from benzyl alcohol via benzaldehyde, thus limiting the growth of the thickness of the lamellae.
Can foreign direct investment help Poland catch up with the EU?
Authors: Weresa Marzenna Anna 
Published: September 2004

The paper examines the extent to which the inflow off oreign direct investment (FDI) helps Poland to catch up with the EU.
FDI can facilitate the process of catching up mainly through transfer and diffusion of technology, which leads to upgrading oftechnological and innovative potential ofa host country. The paper is aimed at assessing whether FDI is correlated with the innovation processes in different branches ofthe Polish industry. A regression analysis conducted in this paper has confirmed that, except for low-technology industries, FDI impacts Poland’s innovation efforts and thus helps Poland to catch up with the EU.
Evolution of the mane and group‐living in the lion (Panthera leo): a review
Authors: Yamaguchi Nobuyuki , Cooper Alan , Werdelin Lars , Macdonald David W. 
Published: September 2004

AbstractThe evolutionary history of the lion Panthera leo began in Pliocene east Africa, as open habitats expanded towards the end of the Cenozoic. During the middle–late Pleistocene, lions spread to most parts of Eurasia, North America, and may have eventually reached as far south as Peru. Lions probably evolved group‐living behaviour before they expanded out of Africa, and this trait is likely to have prevailed in subsequent populations. The first lions were presumed to have been maneless, and maneless forms seem to have persisted in Europe, and possibly the New World, until around 10 000 years ago. The maned form may have appeared c. 320 000–190 000 years ago, and may have had a selective advantage that enabled it to expand to replace the range of earlier maneless forms throughout Africa and western Eurasia by historic times: ‘latest wave hypothesis’.
Social rank in female reindeer (Rangifer tarandus): effects of body mass, antler size and age
Authors: Holand Ø , Gjøstein H. , Losvar A. , Kumpula J. , Smith M. E. , Røed K. H. , Nieminen M. , Weladji R. B. 
Published: September 2004

AbstractIn polygynous mammals, fitness differences may reflect differences in phenotypic quality as well as experience. This study determines dominance hierarchy among female reindeer Rangifer tarandus from two experimental herds (consisting of c. 45 animals in each) during 2 consecutive years. The influence of body mass, antler size and age on social rank in the herds was investigated, first using simple regression analysis. The combined effect of body mass, age and antler size on female rank was further assessed using principal component analysis, as these three parameters were significantly correlated. The improved Laundau linearity index of c. 0.5 (Pr < 0.001) in both herds indicated that a substantial part of the hierarchies was explained by their linearity properties. Consistently, body mass, female age and antler size, as well as their combined effect (measured by the scores on the main axis, PC1), influenced social rank in all four groups. It was concluded that both body mass and age are good predictors of social rank in female reindeer, whereas antler size in comparison plays a less important role in herds with a ‘normal’ female age structure. This suggests that female antlers may have evolved in intersexual rather than intrasexual competition. The temporal variations in the importance of body mass and age, probably owing to variation in female age structure between the 2 years, calls for conservative interpretations of whether body mass or age is more important in determining social rank among female reindeer. This is confirmed by the PCA analyses, where all three variables contributed more or less equally to the first component, the size variable, which on average explained more of the variation in female rank than body mass and age, suggesting that phenotypic quality expressed as the combination of the three variables is a better predictor of social rank than the variables per se. Hence, general conclusions about social rank based on single studies including few animals may not be credible.
Selection of food and ranging behaviour in a sexually monomorphic folivorous lemur: Lepilemur ruficaudatus
Authors: Ganzhorn Jörg U. , Pietsch Thomas , Fietz Joanna , Gross Sabine , Schmid Jutta , Steiner Nathalie 
Published: September 2004

AbstractMonomorphic lemurs of Madagascar allow us to investigate whether there are behavioural mechanisms that compensate for sex‐specific differences in the costs of maintenance and reproduction in arboreal primates. Food selection of the pair‐living Lepilemur ruficaudatus was studied in relation to food chemistry, and travel distances were measured as possible indications of differential investment in ranging activities (possibly related to the defence of territories and/or mating opportunities). Fourteen females and 14 males were radio‐tracked for a total of 365 half‐nights (from dusk to midnight or from midnight to dawn) at different times of the year (birth, lactation and weaning, pre‐mating, post‐mating). When based on monthly means, the two sexes did not differ in nightly travel distances. Food selection of females and males did not differ in relation to the chemical composition of leaves, but fruits consumed by females had lower fibre contents than fruits consumed by males. Even though other behavioural data are fragmentary, little evidence exists for behavioural mechanisms in L. ruficaudatus to compensate for the different energetic costs of females and males.
Encounters between two sympatric carnivores: red foxes (Vulpes vulpes) and European badgers (Meles meles)
Authors: Macdonald D. W. , Buesching C. D. , Stopka P. , Henderson J. , Ellwood S. A. , Baker S. E. 
Published: September 2004

AbstractInterspecific interactions between sympatric carnivores have important implications for intra‐guild competition, epidemiology (here especially in the context of rabies and bovine tuberculosis), and strategies for species‐specific population management. Data are provided on 135 interspecific encounters between at least 35 European badgers Meles meles and a minimum of five red foxes Vulpes vulpes, gathered with the aid of remote video surveillance at an artificial feeding site, and in the vicinity of six badger setts. We hypothesized that interspecific competition would be manifest in aggression and changes in vigilance and feeding, with the larger badger having the advantage, and we sought to explore differences in any such changes at the two types of site. Badgers were clearly dominant over foxes, fed in longer bouts and were less vigilant. At badger setts, once it was clear that the encounter was not going to escalate to aggression, each species was unaffected by the presence, proximity or orientation of the other. There are preliminary indications that foxes sometimes seek the company of badgers.
Molecular data suggest that melanistic ectotherms at the south‐western tip of Africa are the products of Miocene climatic events: evidence from cordylid lizards
Authors: Daniels S. R. , Mouton P. le F. N. , Du Toit D. A. 
Published: September 2004

AbstractIn the present study the evolutionary relationships among Cordylusniger–oelofseni–cordylus are investigated using molecular sequence data to: (1) estimate the divergence within this group; (2) date the origin of melanism in the clade and to evaluate possible palaeoecological events responsible for its evolution; (3) examine the systematic relationships among the three isolated populations of C. oelofseni that were previously shown to be polyphyletic using allozyme data. The recovered topology for the combined sequence data (16S and NADH dehydrogenase component 2 (ND2)) among C. niger–oelofseni–cordylus suggests that melanism evolved only once in the clade. The application of a molecular clock to the data demonstrates that melanism evolved during the Miocene epoch, 17–15 million years ago. We believe that the development of a cold‐water current and upwelling system along the south‐west coast of Africa during this epoch was instrumental in the evolution of melanism in this lizard clade and possibly also in other ectotherm clades with melanistic forms occurring in the area. The results show that C. oelofseni, as presently construed, is composed of three distinct evolutionary lineages, with no shared haplotypes present and marked sequence divergence. Two of the three lineages represent undescribed species. Cordylus cordylus is composed of two distinct clades, a montane clade and a coastal lowland clade. Cladogenic activity in mountain areas of the Western Cape in South Africa has been particularly pronounced and the systematic diversity of many taxa may have been underestimated.
A change of diet from rodents to rabbits (Oryctolagus cuniculus). Is the wildcat (Felis silvestris) a specialist predator?
Authors: Malo Aurelio F. , Lozano Jorge , Huertas Daniel L. , Virgós Emilio 
Published: September 2004

AbstractThe results of a study testing the hypothesis that wildcats Felis silvestris are rodent‐specialist predators is reported. The diet of wildcats was studied in different habitats from central Spain where rabbits Oryctolagus cuniculus were either present or absent in order to explore whether the wildcat is a facultative or a rodent specialist. We predicted that if the wildcat was a rodent specialist there would be no differences in rodent composition in scats between areas with or without another profitable prey such as rabbits. To test this hypothesis, 239 scats were collected in two contrasting habitat types: Mediterranean vegetation areas, where rabbits were either present or absent, and Pyrenean oak forests, where there were no rabbits. All areas and habitat types were sampled in different seasons. The frequency of occurrence and biomass of different prey items and diet diversity were compared between habitats and areas with the presence/absence of rabbits. Wildcats consumed significantly fewer rodents in areas with rabbits than in areas where rabbits were absent, and diet diversity showed important seasonal variations. Values for diet diversity were lower in areas where rabbits were present. Thus it can be stated that wildcats do not specialize in rodents, and we suggest a facultative specialization on different prey items (rabbits or rodents) according to prey availability.
Factors affecting habitat selection by smooth‐coated otters (Lutra perspicillata) in Kerala, India
Authors: Anoop K. R. , Hussain S. A. 
Published: September 2004

AbstractThe factors affecting habitat selection by smooth‐coated otter Lutra perspicillata were studied along the Periyar Lake within the Periyar Tiger Reserve, Kerala, India, between November 2000 and April 2001. The importance of different habitat features influencing habitat selection was assessed using ordination technique. The presence of holts, spraint sites, grooming sites and footprints were considered as good indicators of the use of an area by the otters. For foraging, otters selected less rocky areas of the shallower parts of the lake, which are narrower and slanting. The number of streams joining these areas was more than on the other stretches of the lake and the bankside vegetation was dense. The deeper and wider areas of the lake were avoided. Holts were found in a variety of habitats, such as grass and Lantana thickets, rock crevices and under fallen logs and roots of standing trees at an average distance of 18 m from the water level. Grooming sites were characterized by high sand content and nearness to water.
Horn growth but not asymmetry heralds the onset of senescence in male Alpine ibex (Capra ibex)
Authors: von Hardenberg Achaz , Bassano Bruno , Arranz Maria del Pilar Zumel , Bogliani Giuseppe 
Published: September 2004

AbstractSenescence can be defined as accelerating phenotypic deterioration with old age. For traits that grow throughout life, such as the horns of some ungulates, senescence may be expressed as a decrease in annual growth rates, or an increase in asymmetry, in the years preceding death. Age‐specific yearly horn‐growth segments of 378 male Alpine ibex Capra ibex L. that died from natural causes were analysed in the Gran Paradiso National Park (Italian Alps). Horn annuli displayed fluctuating asymmetry. The hypothesis that asymmetry and size of the annuli of the horns could predict annual survival probability was tested. It was found that between 5 and 11 years of age, male ibex that grew shorter annuli than the average for the population had a greater probability of mortality over the following years than those with greater rates of horn growth. Horn asymmetry and mortality rates were not significantly correlated. Annulus size, reflecting the onset of senescence, seemed to be a better indicator of individual quality than annulus asymmetry.
Cycles representing the Todd class of a toric variety
Authors: Pommersheim James , Thomas Hugh 
Published: September 2004

In this paper, we describe a way to construct cycles which represent the Todd class of a toric variety. Given a lattice with an inner product, we assign a rational number

μ
(
σ
)

\mu (\sigma )

to each rational polyhedral cone

σ
\sigma

in the lattice, such that for any toric variety

X
X

with fan

Σ
\Sigma

in the lattice, we have
\[

Td
⁡
(
X
)
=

∑

σ
∈
Σ

μ
(
σ
)
[
V
(
σ
)
]
.

\operatorname {Td}(X)=\sum _{\sigma \in \Sigma } \mu (\sigma ) [V(\sigma )].

\]
This constitutes an improved answer to an old question of Danilov. In a similar way, beginning from the choice of a complete flag in the lattice, we obtain the cycle Todd classes constructed by Morelli. Our construction is based on an intersection product on cycles of a simplicial toric variety developed by the second author. Important properties of the construction are established by showing a connection to the canonical representation of the Todd class of a simplicial toric variety as a product of torus-invariant divisors developed by the first author.
Regularity of a free boundary in parabolic potential theory
Authors: Caffarelli Luis , Petrosyan Arshak , Shahgholian Henrik 
Published: September 2004

We study the regularity of the free boundary in a Stefan-type problem
\[

Δ
u
−

∂
t

u
=

χ
Ω

in

D
⊂

R

n

×

R

,

u
=

|

∇
u

|

=
0

on

D
∖
Ω

\Delta u - \partial _t u = \chi _\Omega \quad \text {in $D\subset \mathbb {R}^n\times \mathbb {R}$}, \qquad u = |\nabla u| = 0 \quad \text {on $D\setminus \Omega $}

\]
with no sign assumptions on

u
u

and the time derivative

∂
t

u

\partial _t u

.
Hydrogen sulfide‐induced apoptosis of human aorta smooth muscle cells via the activation of mitogen‐activated protein kinases and caspase‐3
Authors: Yang Guangdong , Sun Xianfeng , Wang Rui 
Published: September 2004

ABSTRACTThe endogenous production of hydrogen sulfide (H2S) and its physiological functions, including membrane hyperpolarization and smooth muscle cell relaxation, position this gas well in the family of gasotransmitters together with nitric oxide (NO) and carbon monoxide (CO). In this study, we demonstrate that H2S at physiologically relevant concentrations induced apoptosis of human aorta smooth muscle cells (HASMCs). Exposure of HASMCs to H2S did not induce necrosis as verified with Trypan blue exclusion and LDH release analysis. After inhibiting endogenous H2S production, exogenous H2S induced much more significant apoptosis, which was not altered by the presence of albumin or glutathione. H2S treatment increased the activities of ERK and p38 mitogen‐activated protein kinase (MAPK), but not c‐Jun N‐terminal kinase activity. Suppression of extracellular signal‐regulated kinase (ERK) activity, but not of p38 activity, inhibited the H2S‐induced apoptosis of HASMCs. The activation of ERK by H2S in HASMCs was accompanied by increased caspase‐3 activity. Inhibition of caspase‐3 by AC‐DEVD‐CHO attenuated the H2S‐induced cell apoptosis. Inhibition of ERK by U0126 decreased caspase‐3 activity, whereas AC‐DEVD‐CHO did not alter ERK activity. In conclusion, exogenous H2S induces apoptosis of HASMCs, which is significantly affected by the endogenous H2S level. Of the three investigated MAPKs, only ERK played an active role in mediating H2S‐induced apoptosis of HASMCs by activating caspase‐3. These findings may help reveal novel mechanisms for many diseases linked to H2S‐related abnormal cellular proliferation and apoptosis.