580 research outputs found
Differential isospin-fractionation in dilute asymmetric nuclear matter
The differential isospin-fractionation (IsoF) during the liquid-gas phase
transition in dilute asymmetric nuclear matter is studied as a function of
nucleon momentum. Within a self-consistent thermal model it is shown that the
neutron/proton ratio of the gas phase becomes {\it smaller} than that of the
liquid phase for energetic nucleons, although the gas phase is overall more
neutron-rich. Clear indications of the differential IsoF consistent with the
thermal model predictions are demonstrated within a transport model for
heavy-ion reactions. Future comparisons with experimental data will allow us to
extract critical information about the momentum dependence of the isovector
strong interaction.Comment: Rapid Communication, Phys. Rev. C (2007) in pres
Constraining properties of neutron stars with heavy-ion reactions in terrestrial laboratories
Heavy-ion reactions provide a unique means to investigate the equation of
state (EOS) of neutron-rich nuclear matter, especially the density dependence
of the nuclear symmetry energy . The latter plays an important
role in understanding many key issues in both nuclear physics and astrophysics.
Recent analyses of heavy-ion reactions have already put a stringent constraint
on the around the saturation density. This subsequently allowed
us to constrain significantly the radii and cooling mechanisms of neutron stars
as well as the possible changing rate of the gravitational constant G.Comment: 6 pages. Talk given at the Nuclear Physics in Astrophysics III,
Dresden, Germany, March 26-31, 2007. To appear in a special volume of J. of
Phys.
Sulforaphane induces adipocyte browning and promotes glucose and lipid utilization
Scope: Obesity is closely related to the imbalance of white adipose tissue storing excess calories, and brown adipose tissue dissipating energy to produce heat in mammals. Recent studies revealed that acquisition of brown characteristics by white adipocytes, termed âbrowning,â may positively contribute to cellular bioenergetics and metabolism homeostasis. The goal was to investigate the putative effects of natural antioxidant sulforaphane (1-isothiocyanate-4-methyl-sulfonyl butane; SFN) on browning of white adipocytes. Methods and Results: 3T3-L1 mature white adipocytes were treated with SFN for 48 h, and then the mitochondrial content, function, and energy utilization were assessed. SFN was found to induce 3T3-L1 adipocytes browning based on the increased mitochondrial content and activity of respiratory chain enzymes, whereas the mechanism involved the upregulation of nuclear factor E2-related factor 2/ sirtuin1/ peroxisome proliferator-activated receptor gamma coactivator 1 alpha signaling. SFN enhanced uncoupling protein 1 expression, a marker for brown adipocyte, leading to the decrease in cellular ATP. SFN also enhanced glucose uptake and oxidative utilization, lipolysis and fatty acid oxidation in 3T3-L1 adipocytes. Conclusion: SFN-induced browning of white adipocytes enhanced the utilization of cellular fuel, and the application of SFN is a promising strategy to combat obesity and obesity-related metabolic disorder
Observation of Low Energy Raman Modes in Twisted Bilayer Graphene
Two new Raman modes below 100 cm^-1 are observed in twisted bilayer graphene
grown by chemical vapor deposition. The two modes are observed in a small range
of twisting angle at which the intensity of the G Raman peak is strongly
enhanced, indicating that these low energy modes and the G Raman mode share the
same resonance enhancement mechanism, as a function of twisting angle. The 94
cm^-1 mode (measured with a 532 nm laser excitation) is assigned to the
fundamental layer breathing vibration (ZO (prime) mode) mediated by the twisted
bilayer graphene lattice, which lacks long-range translational symmetry. The
dependence of this modes frequency and linewidth on the rotational angle can be
explained by the double resonance Raman process which is different from the
previously-identified Raman processes activated by twisted bilayer graphene
superlattice. The dependence also reveals the strong impact of electronic-band
overlaps of the two graphene layers. Another new mode at 52 cm^-1, not observed
previously in the bilayer graphene system, is tentatively attributed to a
torsion mode in which the bottom and top graphene layers rotate out-of-phase in
the plane.Comment: 12 pages, 5 figures, 14 supp. figures (accepted by Nano Lett
Electronic Transport in Chemical Vapor Deposited Graphene Synthesized on Cu: Quantum Hall Effect and Weak Localization
We report on electronic properties of graphene synthesized by chemical vapor
deposition (CVD) on copper then transferred to SiO2/Si. Wafer-scale (up to 4
inches) graphene films have been synthesized, consisting dominantly of
monolayer graphene as indicated by spectroscopic Raman mapping. Low temperature
transport measurements are performed on micro devices fabricated from such CVD
graphene, displaying ambipolar field effect (with on/off ratio ~5 and carrier
mobilities up to ~3000 cm^2/Vs) and "half-integer" quantum Hall effect, a
hall-mark of intrinsic electronic properties of monolayer graphene. We also
observe weak localization and extract information about phase coherence and
scattering of carriers.Comment: shortened version, published on APL. See version 1 for more Raman
data
Heterologous expression of a Glyoxalase I gene from sugarcane confers tolerance to several environmental stresses in bacteria
Glyoxalase I belongs to the glyoxalase system that detoxifies methylglyoxal (MG), a cytotoxic by-product produced mainly from triose phosphates. The concentration of MG increases rapidly under stress conditions. In this study, a novel glyoxalase I gene, designated as SoGloI was identified from sugarcane. SoGloI had a size of 1,091Â bp with one open reading frame (ORF) of 885 bp encoding a protein of 294 amino acids. SoGloI was predicted as a Ni2+-dependent GLOI protein with two typical glyoxalase domains at positions 28â149 and 159â283, respectively. SoGloI was cloned into an expression plasmid vector, and the Trx-His-S-tag SoGloI protein produced in Escherichia coli was about 51 kDa. The recombinant E. coli cells expressing SoGloI compared to the control grew faster and tolerated higher concentrations of NaCl, CuCl2, CdCl2, or ZnSO4. SoGloI ubiquitously expressed in various sugarcane tissues. The expression was up-regulated under the treatments of NaCl, CuCl2, CdCl2, ZnSO4 and abscisic acid (ABA), or under simulated biotic stress conditions upon exposure to salicylic acid (SA) and methyl jasmonate (MeJA). SoGloI activity steadily increased when sugarcane was subjected to NaCl, CuCl2, CdCl2, or ZnSO4 treatments. Sub-cellular observations indicated that the SoGloI protein was located in both cytosol and nucleus. These results suggest that the SoGloI gene may play an important role in sugarcaneâs response to various biotic and abiotic stresses
Genome Resources for ClimateâResilient Cowpea, an Essential Crop for Food Security
Cowpea (Vigna unguiculata L. Walp.) is a legume crop that is resilient to hot and droughtâprone climates, and a primary source of protein in subâSaharan Africa and other parts of the developing world. However, genome resources for cowpea have lagged behind most other major crops. Here we describe foundational genome resources and their application to the analysis of germplasm currently in use in West African breeding programs. Resources developed from the African cultivar IT97Kâ499â35 include a wholeâgenome shotgun (WGS) assembly, a bacterial artificial chromosome (BAC) physical map, and assembled sequences from 4355 BACs. These resources and WGS sequences of an additional 36 diverse cowpea accessions supported the development of a genotyping assay for 51 128 SNPs, which was then applied to five biâparental RIL populations to produce a consensus genetic map containing 37 372 SNPs. This genetic map enabled the anchoring of 100 Mb of WGS and 420 Mb of BAC sequences, an exploration of genetic diversity along each linkage group, and clarification of macrosynteny between cowpea and common bean. The SNP assay enabled a diversity analysis of materials from West African breeding programs. Two major subpopulations exist within those materials, one of which has significant parentage from South and East Africa and more diversity. There are genomic regions of high differentiation between subpopulations, one of which coincides with a cluster of nodulin genes. The new resources and knowledge help to define goals and accelerate the breeding of improved varieties to address food security issues related to limitedâinput smallâholder farming and climate stress
Control and Characterization of Individual Grains and Grain Boundaries in Graphene Grown by Chemical Vapor Deposition
The strong interest in graphene has motivated the scalable production of high
quality graphene and graphene devices. Since large-scale graphene films
synthesized to date are typically polycrystalline, it is important to
characterize and control grain boundaries, generally believed to degrade
graphene quality. Here we study single-crystal graphene grains synthesized by
ambient CVD on polycrystalline Cu, and show how individual boundaries between
coalescing grains affect graphene's electronic properties. The graphene grains
show no definite epitaxial relationship with the Cu substrate, and can cross Cu
grain boundaries. The edges of these grains are found to be predominantly
parallel to zigzag directions. We show that grain boundaries give a significant
Raman "D" peak, impede electrical transport, and induce prominent weak
localization indicative of intervalley scattering in graphene. Finally, we
demonstrate an approach using pre-patterned growth seeds to control graphene
nucleation, opening a route towards scalable fabrication of single-crystal
graphene devices without grain boundaries.Comment: New version with additional data. Accepted by Nature Material
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