1,177 research outputs found
Energy transfer in a beam-framed structure using a modal method and a wave method at mid frequencies
A fully framed system consisting of four beams and a rectangular plate has been investigated in terms of the energy transfer between the beams and the plate when a force is applied to one of the beams. This configuration, which is a mixture of stiff and flexible elements, is a particularly important example in the industrial area, as it is widely used. A modal model based on interface basis functions is used. A wave model, which is an approximate method, has also been developed in which the plate, acting as a wave impedance, is separately attached to each beam. Experimental studies have been carried out for validation. The investigation with respect to power flow and energy shows the validity of both models in the mid-frequency region. The results show that most energy is dissipated by the flexible plate. The physical phenomena and limitations of the wave method for this particular structural configuration are discussed. Even though it is an approximate method, the wave approach can describe the dynamic characteristics of the excited beam and the plate in terms of the ratios of power and energy of each component. The comparison of the two methods shows that the plate rather than the beams plays a crucial role in transferring the energy from the excited beam to the parallel opposite beam in the beam-framed structure when these two beams have identical properties, whereas the energy transfer is reduced when the beams have dissimilar properties
Heavy metal content of vegetables irrigated with mixtures of wastewater and sewage sludge in Zimbabwe: Implications for human health
There is growing public concern in Zimbabwe over the illegal cultivation of vegetables on soils amended with sewage sludge or irrigated with admixtures of sewage and sewage sludge. Excessive accumulation of heavy metals in agricultural soils may not only result in environmental contamination, but lead to elevated heavy metal uptake by crops, which may affect food quality and safety. The work reported here studied heavy metal concentrations in crops irrigated with sewage sludge and sewage/sewage sludge admixtures at Firle Municipal Farm in Harare. The crops analysed in this study are heavily contaminated with the four regulated elements Cd, Cu, Pb and Zn. This contamination is at its highest in two of the staple dietary crops maize and tsunga. Tsunga leaves contained 3.68 mg kg-1 Cd, over 18 times the permissible level by the EU standards (0.2 mg kg-1); Cu concentrations were 111 mg kg-1, 5 times the EU Standard (20 mg kg-1); concentrations of Pb were 6.77 mg kg-1, over 22 times the permissible levels allowed by both EU standards and UK guidelines (0.3 mg kg-1); Zn concentrations were 221 mg kg-1, over 4 times the guideline value (50 mg kg-1). The other plants (beans, maize, peppers and sugarcane) also contained concentrations of heavy metals above the permissible levels. Furthermore the concentrations observed in this study were higher than those reported by other workers who have examined vegetation from other contaminated sites. This study highlights the potential risks involved in the cultivation and consumption of vegetables on plots irrigated with sewage sludge, a practice which may place at risk the health of the urban population who consume these vegetables
Structural basis for inhibition of the epidermal growth factor receptor by cetuximab
SummaryRecent structural studies of epidermal growth factor receptor (EGFR) family extracellular regions have identified an unexpected mechanism for ligand-induced receptor dimerization that has important implications for activation and inhibition of these receptors. Here we describe the 2.8 Å resolution X-ray crystal structure of the antigen binding (Fab) fragment from cetuximab (Erbitux), an inhibitory anti-EGFR antibody, in complex with the soluble extracellular region of EGFR (sEGFR). The sEGFR is in the characteristic “autoinhibited” or “tethered” inactive configuration. Cetuximab interacts exclusively with domain III of sEGFR, partially occluding the ligand binding region on this domain and sterically preventing the receptor from adopting the extended conformation required for dimerization. We suggest that both these effects contribute to potent inhibition of EGFR activation
Frequency dependence of Delta_nu of solar-like oscillators investigated: Influence of HeII ionization zone
Oscillations in solar-like oscillators tend to follow an approximately
regular pattern in which oscillation modes of a certain degree and consecutive
order appear at regular intervals in frequency, i.e. the so-called large
frequency separation. This is true to first order approximation for acoustic
modes. However, to a second order approximation it is evident that the large
frequency separation changes as a function of frequency. This frequency
dependence has been seen in the Sun and in other main-sequence stars. However,
from observations of giant stars, this effect seemed to be less pronounced. We
investigate the difference in frequency dependence of the large frequency
separation between main-sequence and giant stars using YREC evolutionary
models.Comment: 4 pages, 1 figure, to appear in Astrophysics and Space Science
Proceedings series of the 20th Stellar pulsation conference held in Granada
(Spain) from 6 to 10 September 201
Fluorescent carbon dioxide indicators
Over the last decade, fluorescence has become the dominant tool in biotechnology and medical imaging. These exciting advances have been underpinned by the advances in time-resolved techniques and instrumentation, probe design, chemical / biochemical sensing, coupled with our furthered knowledge in biology. Complementary volumes 9 and 10, Advanced Concepts of Fluorescence Sensing: Small Molecule Sensing and Advanced Concepts of Fluorescence Sensing: Macromolecular Sensing, aim to summarize the current state of the art in fluorescent sensing. For this reason, Drs. Geddes and Lakowicz have invited chapters, encompassing a broad range of fluorescence sensing techniques. Some chapters deal with small molecule sensors, such as for anions, cations, and CO2, while others summarize recent advances in protein-based and macromolecular sensors. The Editors have, however, not included DNA or RNA based sensing in this volume, as this were reviewed in Volume 7 and is to be the subject of a more detailed volume in the near future
New Results on Standard Solar Models
We describe the current status of solar modelling and focus on the problems
originated with the introduction of solar abundance determinations with low CNO
abundance values. We use models computed with solar abundance compilations
obtained during the last decade, including the newest published abundances by
Asplund and collaborators. Results presented here make focus both on
helioseismic properties and the models as well as in the neutrino fluxes
predictions. We also discuss changes in radiative opacities to restore
agreement between helioseismology, solar models, and solar abundances and show
the effect of such modifications on solar neutrino fluxes.Comment: 9 pages. Review talk presented at "Synergies between solar and
stellar modelling", Rome, June 2009. To be published by Astrophysics and
Space Scienc
CLES, Code Liegeois d'Evolution Stellaire
Cles is an evolution code recently developed to produce stellar models
meeting the specific requirements of studies in asteroseismology. It offers the
users a lot of choices in the input physics they want in their models and its
versatility allows them to tailor the code to their needs and implement easily
new features. We describe the features implemented in the current version of
the code and the techniques used to solve the equations of stellar structure
and evolution. A brief account is given of the use of the program and of a
solar calibration realized with it.Comment: Comments: 8 pages, Astrophys. Space Sci. CoRoT-ESTA Volume, in the
pres
Genetic diversity among farmer-preferred cassava landraces in Uganda
Understanding of genetic diversity among a breeding population is an
important requirement for crop improvement as it allows for the
selection of diverse parental combinations and formation of heterotic
pools for genetic gain. This study was carried out to determine genetic
diversity within and among 51 farmer-preferred cassava ( Manihot
esculenta ) landraces and 15 elite accessions grown in Uganda. Twenty
six simple sequence repeat (SSR) markers used for genetic diversity
assessment in this study revealed a total of 154 alleles, of which 24%
were unique alleles present only in landraces. The genetic diversity
and observed herozygosity in landraces were slightly higher than in
elite accessions. Elite accessions clustered with some of the landraces
indicating that there were some alleles in common. However, 58.8% of
the landraces fell into 3 different clusters independent of the elite
accessions. Including these landraces with unique alleles in cassava
breeding schemes will increase the chances of producing farmer
preferred adapted elite cultivars. The study also revealed genetic
differentiation among accessions from different regions providing an
opportunity for establishment of heterotic pools within a breeding
programme.La compr\ue9hension de la diversit\ue9 g\ue9n\ue9tique est une
condition importante dans la s\ue9lection de diverses combinaisons
parentales et la formation des groupes h\ue9terotiques
d\u2019int\ue9r\ueat g\ue9n\ue9tique pour
l\u2019am\ue9lioration des cultures. Cette \ue9tude \ue9tait
conduite pour d\ue9terminer la diversit\ue9 g\ue9n\ue9tique
parmi 51 vari\ue9t\ue9s locales de manioc ( Manihot esculenta )
pr\ue9f\ue9r\ue9es des fermiers et 15 accessions \ue9lites
cultiv\ue9es en Ouganda. Vingt six marqueurs simples \ue0 sequence
r\ue9p\ue9t\ue9e (SSR) utilis\ue9s pour l\u2019\ue9valuation
de la diversit\ue9 g\ue9n\ue9tique ont r\ue9v\ue9l\ue9 un
total de 154 all\ue8les, parmi lesquelles 24% \ue9taient des
all\ue8les uniques pr\ue9sentes dans les races locales seulement.
La diversit\ue9 g\ue9n\ue9tique et
l\u2019h\ue9terozygosit\ue9 observ\ue9es dans les races locales
\ue9taient l\ue9g\ue8rement sup\ue9rieures que dans les
accessions \ue9lites. Celles-ci s\u2019\ue9taient regroup\ue9es
avec quelques vari\ue9t\ue9s locales indiquant donc qu\u2019elles
avaient quelques all\ue8les en commun. Par ailleurs, 58.8% des races
locales ont form\ue9 trois diff\ue9rents groupes
ind\ue9pendamment des accessions \ue9lites. Inclure ces races
locales \ue0 all\ue8les uniques dans les syst\ue8mes
d\u2019am\ue9lioration du manioc permettra d\u2019augmenter les
chances de produire des cultivars \ue9lites pr\ue9f\ue9r\ue9s
des fermiers. L\u2019\ue9tude montre aussi que la
diff\ue9renciation g\ue9n\ue9tique trouv\ue9e parmi les
accessions de diff\ue9rentes r\ue9gions est une opportunit\ue9
offerte pour l\u2019\ue9tablissement des groupes h\ue9terotiques
dans le programme d\u2019am\ue9lioration
Habitable Zones of Host Stars During the Post-MS Phase
A star will become brighter and brighter with stellar evolution, and the
distance of its habitable zone will become farther and farther. Some planets
outside the habitable zone of a host star during the main sequence phase may
enter the habitable zone of the host star during other evolutionary phases. A
terrestrial planet within the habitable zone of its host star is generally
thought to be suited to life existence. Furthermore, a rocky moon around a
giant planet may be also suited to life survive, provided that the planet-moon
system is within the habitable zone of its host star. Using Eggleton's code and
the boundary flux of habitable zone, we calculate the habitable zone of our
Solar after the main sequence phase. It is found that Mars' orbit and Jupiter's
orbit will enter the habitable zone of Solar during the subgiant branch phase
and the red giant branch phase, respectively. And the orbit of Saturn will
enter the habitable zone of Solar during the He-burning phase for about 137
million years. Life is unlikely at any time on Saturn, as it is a giant gaseous
planet. However, Titan, the rocky moon of Saturn, may be suitable for
biological evolution and become another Earth during that time. For low-mass
stars, there are similar habitable zones during the He-burning phase as our
Solar, because there are similar core masses and luminosities for these stars
during that phase.Comment: 6 pages, 7 figures. Accepted by Ap & S
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