4,269 research outputs found
DNA adducts in peripheral blood lymphocytes from aluminum production plant workers determined by 32P-postlabeling and enzyme-linked immunosorbent assay
32P-Postlabeling analysis and enzyme-linked immunosorbent assay (ELISA) have been used to detect DNA adducts in peripheral blood lymphocytes from primary aluminum production plant workers who were exposed occupationally to a mixture of polycyclic aromatic hydrocarbons (PAHs). Preliminary results reported here are from a comparative study being performed in two aluminum plants. The levels of aromatic DNA adducts have been determined by the 32P-postlabeling assay in samples collected on two occasions, 1 year apart. PAH-DNA adduct levels have also been determined by competitive ELISA in the second set of DNA samples. The results show the necessity of follow-up biomonitoring studies to detect possible alterations in biological effect induced by changing exposures. The comparison of the results obtained by 32P-postlabeling and ELISA may lead to a better understanding of the power and weaknesses of the two methods applied in these studies
Mott Transition, Compressibility Divergence and P-T Phase Diagram of Layered Organic Superconductors: An Ultrasonic Investigation
The phase diagram of the organic superconductor
-(BEDT-TTF)Cu[N(CN)Cl has been investigated by ultrasonic
velocity measurements under helium gas pressure. Different phase transitions
were identified trough several elastic anomalies characterized from isobaric
and isothermal sweeps. Our data reveal two crossover lines that end on the
critical point terminating the first-order Mott transition line. When the
critical point is approached along these lines, we observe a dramatic softening
of the velocity which is consistent with a diverging compressibility of the
electronic degrees of freedom.Comment: 4 pages, 5 figure
Complex microwave conductivity of PrCeCuO thin films using a cavity perturbation method
We report a study of the microwave conductivity of electron-doped
PrCeCuO superconducting thin films using a
cavity perturbation technique. The relative frequency shifts obtained for the
samples placed at a maximum electric field location in the cavity are treated
using the high conductivity limit presented recently by Peligrad
Using two resonance modes, TE (16.5 GHz) and TE
(13 GHz) of the same cavity, only one adjustable parameter is needed
to link the frequency shifts of an empty cavity to the ones of a cavity loaded
with a perfect conductor. Moreover, by studying different sample
configurations, we can relate the substrate effects on the frequency shifts to
a scaling factor. These procedures allow us to extract the temperature
dependence of the complex penetration depth and the complex microwave
conductivity of two films with different quality. Our data confirm that all the
physical properties of the superconducting state are consistent with an order
parameter with lines of nodes. Moreover, we demonstrate the high sensitivity of
these properties on the quality of the films
MicroRNA399 is a long-distance signal for the regulation of plant phosphate homeostasis
The presence of microRNA species in plant phloem sap suggests potential signaling roles by long-distance regulation of gene expression. Proof for such a role for a phloem-mobile microRNA is lacking. Here we show that phosphate (Pi) starvation-induced microRNA399 (miR399) is present in the phloem sap of two diverse plant species, rapeseed and pumpkin, and levels are strongly and specifically increased in phloem sap during Pi deprivation. By performing micro-grafting experiments using Arabidopsis, we further show that chimeric plants constitutively over-expressing miR399 in the shoot accumulate mature miR399 species to very high levels in their wild-type roots, while corresponding primary transcripts are virtually absent in roots, demonstrating shoot-to-root transport. The chimeric plants exhibit (i) down-regulation of the miR399 target transcript (PHO2), which encodes a critical component for maintenance of Pi homeostasis, in the wild-type root, and (ii) Pi accumulation in the shoot, which is the phenotype of pho2 mutants, miR399 over-expressers or chimeric plants with a genetic knock-out of PHO2 in the root. Hence the transported miR399 molecules retain biological activity. This is a demonstration of systemic control of a biological process, i.e. maintenance of plant Pi homeostasis, by a phloem-mobile microRNA
Fractured-Aquifer Hydrogeology from Geophysical Logs; The Passaic Formation, New Jersey
The Passaic Formation consists of gradational sequences of mudstone, siltstone, and sandstone, and is a principal aquifer in central New Jersey. Ground-water flow is primarily controlled by fractures interspersed throughout these sedimentary rocks and characterizing these fractures in terms of type, orientation, spatial distribution, frequency, and transmissivity is fundamental towards understanding local fluid-transport processes. To obtain this information, a comprehensive suite of geophysical logs was collected in 10 wells roughly 46 m in depth and located within a .05 km2 area in Hopewell Township, New Jersey. A seemingly complex, heterogeneous network of fractures identified with an acoustic televiewer was statistically reduced to two principal subsets corresponding to two distinct fracture types: (1) bedding-plane partings and (2) high-angle fractures. Bedding-plane partings are the most numerous and have an average strike of N84° Wand dip of 20° N. The high-angle fractures are oriented subparallel to these features, with an average strike of N79° E and dip of 71 0 S, making the two fracture types roughly orthogonal. Their intersections form linear features that also retain this approximately east-west strike. Inspection of fluid temperature and conductance logs in conjunction with flowmeter measurements obtained during pumping allows the transmissive fractures to be distinguished from the general fracture population. These results show that, within the resolution capabilities ofthe logging tools, approximately 51 (or 18 percent) of the 280 total fractures are water producing. The bedding-plane partings exhibit transmissivities that average roughly 5 m2/day and that generally diminish in magnitude and frequency with depth. The high-angle fractures have average transmissivities that are about half those of the bedding-plane partings and show no apparent dependence upon depth. The geophysical logging results allow us to infer a distinct hydrogeologic structure within this aquifer that is defined by fracture type and orientation. Fluid flow near the surface is controlled primarily by the highly transmissive, subhorizontal bedding-plane partings. As depth increases, the high-angle fractures apparently become more dominant hydrologically
Diffusion on a solid surface: Anomalous is normal
We present a numerical study of classical particles diffusing on a solid
surface. The particles' motion is modeled by an underdamped Langevin equation
with ordinary thermal noise. The particle-surface interaction is described by a
periodic or a random two dimensional potential. The model leads to a rich
variety of different transport regimes, some of which correspond to anomalous
diffusion such as has recently been observed in experiments and Monte Carlo
simulations. We show that this anomalous behavior is controlled by the friction
coefficient, and stress that it emerges naturally in a system described by
ordinary canonical Maxwell-Boltzmann statistics
Bulk Band Gaps in Divalent Hexaborides
Complementary angle-resolved photoemission and bulk-sensitive k-resolved
resonant inelastic x-ray scattering of divalent hexaborides reveal a >1 eV
X-point gap between the valence and conduction bands, in contradiction to the
band overlap assumed in several models of their novel ferromagnetism. This
semiconducting gap implies that carriers detected in transport measurements
arise from defects, and the measured location of the bulk Fermi level at the
bottom of the conduction band implicates boron vacancies as the origin of the
excess electrons. The measured band structure and X-point gap in CaB_6
additionally provide a stringent test case for proper inclusion of many-body
effects in quasi-particle band calculations.Comment: 4 pages, 3 figures; new RIXS analysis; accepted for publication in
PR
Phenomenological model of elastic distortions near the spin-Peierls transition in
A phenomenological model of the Landau type forms the basis for a study of
elastic distortions near the spin-Peierls transition in . The
atomic displacements proposed by Hirota {\it et al.} [Phys. Rev. Lett. {\bf
73}, 736 (1994)] are accounted for by the model which includes linear coupling
between and distortions. displacements are seen to be responsible
for anomalies in the elastic properties {\it at} , whereas incipient
distortions give rise to temperature dependence below . A discussion of
possible critical behavior is also made.Comment: 1 figure available upon reques
Functional expression of PHO1 to the Golgi and trans-Golgi network and its role in export of inorganic phosphate.
Arabidopsis thaliana PHO1 is primarily expressed in the root vascular cylinder and is involved in the transfer of inorganic phosphate (Pi) from roots to shoots. To analyze the role of PHO1 in transport of Pi, we have generated transgenic plants expressing PHO1 in ectopic A. thaliana tissues using an estradiol-inducible promoter. Leaves treated with estradiol showed strong PHO1 expression, leading to detectable accumulation of PHO1 protein. Estradiol-mediated induction of PHO1 in leaves from soil-grown plants, in leaves and roots of plants grown in liquid culture, or in leaf mesophyll protoplasts, was all accompanied by the specific release of Pi to the extracellular medium as early as 2-3 h after addition of estradiol. Net Pi export triggered by PHO1 induction was enhanced by high extracellular Pi and weakly inhibited by the proton-ionophore carbonyl cyanide m-chlorophenylhydrazone. Expression of a PHO1-GFP construct complementing the pho1 mutant revealed GFP expression in punctate structures in the pericycle cells but no fluorescence at the plasma membrane. When expressed in onion epidermal cells or in tobacco mesophyll cells, PHO1-GFP was associated with similar punctate structures that co-localized with the Golgi/trans-Golgi network and uncharacterized vesicles. However, PHO1-GFP could be partially relocated to the plasma membrane in leaves infiltrated with a high-phosphate solution. Together, these results show that PHO1 can trigger Pi export in ectopic plant cells, strongly indicating that PHO1 is itself a Pi exporter. Interestingly, PHO1-mediated Pi export was associated with its localization to the Golgi and trans-Golgi networks, revealing a role for these organelles in Pi transport
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