443 research outputs found
A Drought Indicator based on Ecosystem Responses to Water Availability: The Normalized Ecosystem Drought Index
Drought is one of the most destructive natural disasters causing serious damages to human society, and studies have projected more severe and widespread droughts in the coming decades associated with the warming climate. Although several drought indices have been developed for drought monitoring, most of them were based on large scale environmental conditions rather than ecosystem transitional patterns to drought. Here, we propose using the ecosystem function oriented Normalized Ecosystem Drought Index (NEDI) to quantify drought severity, loosely related to Sprengel’s and Liebig’s Law of the Minimum for plant nutrition. Extensive eddy covariance measurements from 60 AmeriFlux sites across 8 IGBP vegetation types were used to validate the use of NEDI. The results show that NEDI can reasonably capture ecosystem transitional responses to limited water availability, suggesting that drought conditions detected by NEDI are ecosystem function oriented. The wildly used Palmer Drought Severity Index (PDSI), on the other hand, does not have a clear relationship with ecosystem responses to drought conditions because ecosystem adaptation ability is not considered in PDSI calculation.We thank the principal investigators of the AmeriFlux network, and the U.S. Department of Energy’s Office of Science for funding the AmeriFlux data resources. We thank the U.S. Department of Energy Lawrence Berkeley Lab Ameriflux Network Management Project for core site support. This research was supported through the National Science Foundation award EF1137306/MIT subaward 5710003122 to the University of California Davis; and other government, industry and foundation sponsors of the MIT Joint Program on the Science and Policy of Global Change. For a complete list of sponsors and U.S. government funding sources, please visit http://globalchange.mit.edu/sponsors/all
Fast simultaneous detection of K-RAS mutations in colorectal cancer
<p>Abstract</p> <p>Background</p> <p><it>RAS </it>genes acquire the most common somatic gain-of-function mutations in human cancer, and almost all of these mutations are located at codons 12, 13, 61, and 146.</p> <p>Methods</p> <p>We present a method for detecting these <it>K-RAS </it>hotspot mutations in 228 cases of colorectal cancer. The protocol is based on the multiplex amplification of exons 2, 3 and 4 in a single tube, followed by primer extension of the PCR products using various sizes of primers to detect base changes at codons 12, 13, 61 and 146. We compared the clinicopathological data of colorectal cancer patients with the <it>K-RAS </it>mutation status.</p> <p>Results</p> <p><it>K-RAS </it>mutation occurred in 36% (83/228) of our colorectal cancer cases. Univariate analysis revealed a significant association between <it>K-RAS </it>mutation at codon 12 of exon 2 and poor 5-year survival (p = 0.023) and lymph node involvement (p = 0.048). Also, <it>K-RAS </it>mutation at codon 13 of exon 2 correlates with the size of the tumor (p = 0.03). Multivariate analysis adjusted for tumor size, histologic grade, and lymph node metastasis also indicated <it>K-RAS </it>mutations at codon 12 and 13 of exon 2 correlate significantly with overall survival (p = 0.002 and 0.025). No association was observed between codon 61 and 146 and clinicopathological features.</p> <p>Conclusion</p> <p>We demonstrated a simple and fast way to identify <it>K-RAS </it>mutation.</p
Supporting 'design for reuse' with modular design
Engineering design reuse refers to the utilization of any knowledge gained from the design activity to support future design. As such, engineering design reuse approaches are concerned with the support, exploration, and enhancement of design knowledge prior, during, and after a design activity. Modular design is a product structuring principle whereby products are developed with distinct modules for rapid product development, efficient upgrades, and possible reuse (of the physical modules). The benefits of modular design center on a greater capacity for structuring component parts to better manage the relation between market requirements and the designed product. This study explores the capabilities of modular design principles to provide improved support for the engineering design reuse concept. The correlations between modular design and 'reuse' are highlighted, with the aim of identifying its potential to aid the little-supported process of design for reuse. In fulfilment of this objective the authors not only identify the requirements of design for reuse, but also propose how modular design principles can be extended to support design for reuse
New lanostanes and naphthoquinones isolated from Antrodia salmonea and their antioxidative burst activity in human leukocytes
Four new compounds were isolated from the basidiomata of the fungus Antrodia salmonea, a newly identified species of Antrodia (Aphyllophorales) in Taiwan. These new compounds are named as lanosta-8,24-diene-3 beta,15 alpha,21-triol (1), 24-methylenelanost-8-ene-3 beta,15 alpha,21-triol (2), 2,3-dimethoxy-5-(2',5'-dimethoxy-3',4'-methylenedioxyphenyl)-7-methyl-[1,4]-naphthoquinone (3), and 2,3-dimethoxy-6-(2,5'-dimethoxy-3',4'-methylenedioxyphenyl)-7-methyl-[1,4]-naphthoquinone (4), respectively. Their structures were elucidated by spectroscopic methods. An in vitro cellular functional assay was performed to evaluate their anti-oxidative burst activity in human leukocytes. They showed inhibitory effects against phorbol 12-myristate-13-acetate (PMA), a direct protein kinase C activator, induced oxidative burst in neutrophils (PMN) and mononuclear cells (MNC) with 50% inhibitory concentration (IC50) ranging from 3.5 to 25.8 mu M. The potency order of these compounds in PMA-activated leukocytes was as 1 > 3 > 4 > 2. They were relatively less effective in formyl-Met-Leu-Phe (fMLP), a G-protein coupled receptor agonist, induced oxidative burst, except for compounds 3 and 4 in fMLP-activated PMN. These results indicated that three (1, 3, and 4) of these four newly identified compounds displayed antioxidative effect in human leukocytes with different potency and might confer anti-inflammatory activity to these drugs
On the Possibility of Optical Unification in Heterotic Strings
Recently J. Giedt discussed a mechanism, entitled optical unification,
whereby string scale unification is facilitated via exotic matter with
intermediate scale mass. This mechanism guarantees that a virtual MSSM
unification below the string scale is extrapolated from the running of gauge
couplings upward from M_Z^o when an intermediate scale desert is assumed. In
this letter we explore the possibility of optical unification within the
context of weakly coupled heterotic strings. In particular, we investigate this
for models of free fermionic construction containing the NAHE set of basis
vectors. This class is of particular interest for optical unification, because
it provides a standard hypercharge embedding within SO(10), giving the standard
k_Y = 5/3 hypercharge level, which was shown necessary for optical unification.
We present a NAHE model for which the set of exotic SU(3)_C
triplet/anti-triplet pairs, SU(2)_L doublets, and non-Abelian singlets with
hypercharge offers the possibility of optical unification. Whether this model
can realize optical unification is conditional upon these exotics not receiving
Fayet-Iliopoulos (FI) scale masses when a flat direction of scalar vacuum
expectation values is non-perturbatively chosen to cancel the FI D-term, xi,
generated by the anomalous U(1)-breaking Green-Schwarz-Dine-Seiberg-Wittten
mechanism. A study of perturbative flat directions and their phenomenological
implications for this model is underway.
This paper is a product of the NFS Research Experiences for Undergraduates
and the NSF High School Summer Science Research programs at Baylor University.Comment: 16 pages. Standard Late
Muon anomalous magnetic moment in the standard model with two Higgs doublets
The muon anomalous magnetic moment is investigated in the standard model with
two Higgs doublets (S2HDM) motivated from spontaneous CP violation. Thus all
the effective Yukawa couplings become complex. As a consequence of the non-zero
phase in the couplings, the one loop contribution from the neutral scalar
bosons could be positive and negative relying on the CP phases. The
interference between one and two loop diagrams can be constructive in a large
parameter space of CP-phases. This will result in a significant contribution to
muon anomalous magnetic moment even in the flavor conserving process with a
heavy neutral scalar boson ( 200 GeV) once the effective muon Yukawa
coupling is large (). In general, the one loop contributions
from lepton flavor changing scalar interactions become more important. In
particular, when all contributions are positive in a reasonable parameter space
of CP phases, the recently reported 2.6 sigma experiment vs. theory deviation
can be easily explained even for a heavy scalar boson with a relative small
Yukawa coupling in the S2HDM.Comment: 8 pages, RevTex file, 5 figures, published version Phys. Rev. D 54
(2001) 11501
Slepton Flavor Nonuniversality, the Muon EDM and its Proposed sensitive Search at Brookhaven
We analyze the electric dipole moment of the electron (), of the neutron
() and of the muon () using the cancellation mechanism in the
presence of nonuniversalities of the soft breaking parameters. It is shown that
the nonuniversalities in the slepton sector produce a strong violation of the
scaling relation in the cancellation region. An
analysis of and under the constraints of the current
experimental limits on and and under the constraints of the recent
Brookhaven result on shows that in the non-scaling region
can be as large as ()ecm and thus within reach of the
recently proposed Brookhaven experiment for a sensitive search for at
the level of ecm.Comment: 24 pages, Latex, including 5 figures with additional reference
Quantum dynamics of phase transitions in broken symmetry field theory
We perform a detailed numerical investigation of the dynamics of broken
symmetry field theory in 1+1 dimensions using a
Schwinger-Dyson equation truncation scheme based on ignoring vertex
corrections. In an earlier paper, we called this the bare vertex approximation
(BVA). We assume the initial state is described by a Gaussian density matrix
peaked around some non-zero value of and .Comment: 28 pages, 21 figures; ver 2 -- additional comments on the nature of
the phase transition in 1+1 dimension
Substructures in lens galaxies: PG1115+080 and B1555+375, two fold configurations
We study the anomalous flux ratio which is observed in some four-image lens
systems, where the source lies close to a fold caustic. In this case two of the
images are close to the critical curve and their flux ratio should be equal to
unity, instead in several cases the observed value differs significantly. The
most plausible solution is to invoke the presence of substructures, as for
instance predicted by the Cold Dark Matter scenario, located near the two
images. In particular, we analyze the two fold lens systems PG1115+080 and
B1555+375, for which there are not yet satisfactory models which explain the
observed anomalous flux ratios. We add to a smooth lens model, which reproduces
well the positions of the images but not the anomalous fluxes, one or two
substructures described as singular isothermal spheres. For PG1115+080 we
consider a smooth model with the influence of the group of galaxies described
by a SIS and a substructure with mass as well as a
smooth model with an external shear and one substructure with mass . For B1555+375 either a strong external shear or two substructures
with mass reproduce the data quite well.Comment: 26 pages, updated bibliography, Accepted for publication in
Astrophysics & Space Scienc
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