2,855 research outputs found
Avian taxonomic and functional diversity in early stage of longleaf pine (Pinus palustris) stands restored at agricultural lands: Variations in scale dependency
In agricultural landscapes, the Longleaf Pine Initiative (LLPI) and the Bobwhite Quail Initiative (BQI) aim to restore longleaf pine forests and early successional habitats, respectively. The early stage of longleaf pine stands and grass and forb vegetation produced by a combination of both restoration programs (LLPI-BQI) may form habitat conditions favorable to early successional bird species and other birds, increasing avian diversity. We investigated how the LLPI and BQI programs affected taxonomic and functional diversity of birds and abundance of early successional birds (grassland and scrub/shrub species), and what environmental characteristics were associated with the diversity and abundance of birds. Our study was performed at 41 fields in Georgia, USA, during 2001-2002 by considering environmental characteristics at two spatial scales: local-scale vegetation features and restoration program type (LLPI or LLPI-BQI) and landscape-scale vegetation features and landscape heterogeneity. Functional evenness, species richness, and abundance of grassland and scrub/shrub species did not show a clear association with local- or landscape-scale variables. Shannon-Wiener diversity was slightly influenced by restoration program type (local-scale variable) with higher value at LLPI-BQI stands than at LLPI stands despite no significant differences in local vegetation features between those stands. Functional divergence was strongly positively associated with landscape-scale variables. That is, niche differentiation increased with increasing shrub coverage within a landscape, reducing competition between abundant bird species and others. Our results suggest that although a combination of BQI and LLPI program may have a positive effect on avian taxonomic diversity, it is important to consider shrub vegetation cover within a landscape to improve functional diversity
Avian taxonomic and functional diversity in early stage of longleaf pine (Pinus palustris) stands restored at agricultural lands: Variations in scale dependency
In agricultural landscapes, the Longleaf Pine Initiative (LLPI) and the Bobwhite Quail Initiative (BQI) aim to restore longleaf pine forests and early successional habitats, respectively. The early stage of longleaf pine stands and grass and forb vegetation produced by a combination of both restoration programs (LLPI-BQI) may form habitat conditions favorable to early successional bird species and other birds, increasing avian diversity. We investigated how the LLPI and BQI programs affected taxonomic and functional diversity of birds and abundance of early successional birds (grassland and scrub/shrub species), and what environmental characteristics were associated with the diversity and abundance of birds. Our study was performed at 41 fields in Georgia, USA, during 2001-2002 by considering environmental characteristics at two spatial scales: local-scale vegetation features and restoration program type (LLPI or LLPI-BQI) and landscape-scale vegetation features and landscape heterogeneity. Functional evenness, species richness, and abundance of grassland and scrub/shrub species did not show a clear association with local- or landscape-scale variables. Shannon-Wiener diversity was slightly influenced by restoration program type (local-scale variable) with higher value at LLPI-BQI stands than at LLPI stands despite no significant differences in local vegetation features between those stands. Functional divergence was strongly positively associated with landscape-scale variables. That is, niche differentiation increased with increasing shrub coverage within a landscape, reducing competition between abundant bird species and others. Our results suggest that although a combination of BQI and LLPI program may have a positive effect on avian taxonomic diversity, it is important to consider shrub vegetation cover within a landscape to improve functional diversity
Secondary Metabolic Gene Cluster Silencing in Aspergillus Nidulans
In contrast to most primary metabolism genes, the genes involved in secondary metabolism and certain nutrient utilization pathways are clustered in fungi. Recently a nuclear protein, LaeA, was found to be required for the transcription of several secondary metabolite gene clusters in Aspergillus nidulans. Here we show that LaeA regulation does not extend to nutrient utilization or the spoC1 sporulation clusters. One of the secondary metabolite clusters regulated by LaeA contains the positive regulatory (i.e. aflR) and biosynthetic genes required for biosynthesis of sterigmatocystin (ST), a carcinogenic toxin. Analysis of ST gene cluster expression indicates LaeA regulation of the cluster is location specific as transcription of genes bordering the ST cluster are unaffected in a ΔlaeA mutant and placement of a primary metabolic gene, argB, in the ST cluster resulted in argB silencing in the ΔlaeA background. ST cluster gene expression was remediated when an additional copy of aflR was placed outside of the cluster but not when placed in the cluster. Site-specific mutation of an s-adenosyl methionine (AdoMet) binding site in LaeA generated a ΔlaeA phenotype suggesting the protein to be a methyltransferase
Spin-triplet superconductivity in quasi-one dimension
We consider a system with electron-phonon interaction, antiferromagnetic
fluctuations and disconnected open Fermi surfaces. The existence of odd-parity
superconductivity in this circumstance is shown for the first time. If it is
applied to the quasi-one-dimensional systems like the organic conductors
(TMTSF)_2X we obtain spin-triplet superconductivity with nodeless gap. Our
result is also valid in higher dimensions(2d and 3d).Comment: 2 page
Differences in Iron Removal from Carbon Nanoonions and Multiwall Carbon Nanotubes for Analytical Purpose
The paper describes the differences between wet iron removal from carbon nanoonions and from multiwall carbon nanotubes for analytical purpose. Nowadays, both carbon nanoonions and multiwall carbon nanotubes are one of the most interesting materials with applicability in electronics, medicine and biotechnology. Medical applications of those nanomaterials require not only recognition of their structure but also measurement of metal impurities concentration. Inductively coupled plasma optical emission spectrometry as a method for Fe-determination requires liquid samples. Hence, we propose various protocols for leaching of iron from studied materials. Our results proved that structure of nanomaterials have an impact on the efficiency of iron removal
Differences in Iron Removal from Carbon Nanoonions and Multiwall Carbon Nanotubes for Analytical Purpose
The paper describes the differences between wet iron removal from carbon nanoonions and from multiwall carbon nanotubes for analytical purpose. Nowadays, both carbon nanoonions and multiwall carbon nanotubes are one of the most interesting materials with applicability in electronics, medicine and biotechnology. Medical applications of those nanomaterials require not only recognition of their structure but also measurement of metal impurities concentration. Inductively coupled plasma optical emission spectrometry as a method for Fe-determination requires liquid samples. Hence, we propose various protocols for leaching of iron from studied materials. Our results proved that structure of nanomaterials have an impact on the efficiency of iron removal
Shifts of the nuclear resonance in the vortex lattice in YBaCuO
The NMR and NQR spectra of Cu in the CuO plane of
YBaCuO in the superconducting state are discussed in terms of the
phenomenological theory of Ginzburg-Landau type extended to lower temperatures.
We show that the observed spectra, Kumagai {\em et al.}, PRB {\bf 63}, 144502
(2001), can be explained by a standard theory of the Bernoulli potential with
the charge transfer between CuO planes and CuO chains assumed.Comment: 11 pages 7 figure
Comments on the d-wave pairing mechanism for cuprate high superconductors: Higher is different?
The question of pairing glue for the cuprate superconductors (SC)is revisited
and its determination through the angle resolved photo-emission spectroscopy
(ARPES) is discussed in detail. There are two schools of thoughts about the
pairing glue question: One argues that superconductivity in the cuprates
emerges out of doping the spin singlet resonating valence bond (RVB) state.
Since singlet pairs are already formed in the RVB state there is no need for
additional boson glue to pair the electrons. The other instead suggests that
the d-wave pairs are mediated by the collective bosons like the conventional
low SC with the alteration that the phonons are replaced by another kind
of bosons ranging from the antiferromagnetic (AF) to loop current fluctuations.
An approach to resolve this dispute is to determine the frequency and momentum
dependences of the diagonal and off-diagonal self-energies directly from
experiments like the McMillan-Rowell procedure for the conventional SC. In that
a simple d-wave BCS theory describes superconducting properties of the cuprates
well, the Eliashberg analysis of well designed high resolution experimental
data will yield the crucial frequency and momentum dependences of the
self-energies. This line of approach using ARPES are discussed in more detail
in this review, and some remaining problems are commented.Comment: Invited review article published in the Journal of Korean Physical
Society; several typos corrected and a few comments and references adde
Granularity-induced gapless superconductivity in NbN films: evidence of thermal phase fluctuations
Using a single coil mutual inductance technique, we measure the low
temperature dependence of the magnetic penetration depth in superconducting NbN
films prepared with similar critical temperatures around 16 K but with
different microstructures. Only (100) epitaxial and weakly granular (100)
textured films display the characteristic exponential dependence of
conventional BCS s-wave superconductors. More granular (111) textured films
exhibit a linear dependence, indicating a gapless state in spite of the s-wave
gap. This result is quantitatively explained by a model of thermal phase
fluctuations favored by the granular structure.Comment: 10 pages, 4 figures, to appear in Phys. Rev.
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