637 research outputs found
Differential effect of denervation on free radical scavenging enzymes in slow and fast muscle of rat
To determine the effect of denervation on the free radical scavenging systems in relation to the mitochondrial oxidative metabolism in the slow twitch soleus and fast twitch extensor digitorum longus (EDL) muscles, the sciatic nerve of the rat was crushed in the mid-thigh region and the muscle tissue levels of 5 enzymes were studied 2 and 5 weeks following crush. Radioimmunoassays were utilized for the selective measurement of cuprozinc (cytosolic) and mangano (mitochondrial) superoxide dismutases. These data represent the first systematic report of free radical scavening systems in slow and fast muscles in response to denervation. Selective modification of cuprozinc and manganosuperoxide dismutases and differential regulation of GSH-peroxidase was demonstrated in slow and fast muscle
Stringent promoter recognition and autoregulation by the group 3 σ-factor SigF in the cyanobacterium Synechocystis sp. strain PCC 6803
The cyanobacteirum Synechocystis sp. strain PCC 6803 possesses nine species of the sigma (σ)-factor gene for RNA polymerase (RNAP). Here, we identify and characterize the novel-type promoter recognized by a group 3 σ-factor, SigF. SigF autoregulates its own transcription and recognizes the promoter of pilA1 that acts in pilus formation and motility in PCC 6803. The pilA1 promoter (PpilA1-54) was recognized only by SigF and not by other σ-factors in PCC 6803. No PpilA1-54 activity was observed in Escherichia coli cells that possess RpoF (σ28) for fragellin and motility. Studies of in vitro transcription for PpilA1-54 identified the region from −39 to −7 including an AG-rich stretch and a core promoter with TAGGC (−32 region) and GGTAA (−12 region) as important for transcription. We also confirmed the unique PpilA1-54 architecture and further identified two novel promoters, recognized by SigF, for genes encoding periplasmic and phytochrome-like phototaxis proteins. These results and a phylogenetic analysis suggest that the PCC 6803 SigF is distinct from the E. coli RpoF or RpoD (σ70) type and constitutes a novel eubacterial group 3 σ-factor. We discuss a model case of stringent promoter recognition by SigF. Promoter types of PCC 6803 genes are also summarized
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Engineering climate debt: temperature overshoot and peak-shaving as risky subprime mortgage lending
Despite the ambitious temperature goal of the 2015 Paris Agreement,
the pace of reducing global CO2 emissions remains sluggish. This
creates conditions in which the idea of temperature ‘overshoot and peakshaving’
is emerging as a possible strategy to meet the Paris goal. An
overshoot and peak-shaving scenario rests upon the ‘temporary’ use of
speculative solar radiation management (SRM) technologies combined
with large-scale carbon dioxide removal (CDR). Whilst some view
optimistically the strategic interdependence between SRM and CDR, we
argue that this strategy comes with a risk of escalating ‘climate debt’.
We explain our position using the logic of debt and the analogy of
subprime mortgage lending. In overshoot and peak-shaving scenarios,
the role of CDR and SRM is to compensate for delayed mitigation, placing
the world in a double debt: ‘emissions debt’ and ‘temperature debt’.
Analogously, this can be understood as a combination of ‘subprime
mortgage’ (i.e., large-scale CDR) and ‘home-equity-line-of-credit’ (i.e.,
temporary SRM). With this analogy, we draw some important lessons
from the 2007-2009 US subprime mortgage crisis. The analogy signals
that the efficacy of temporary SRM cannot be evaluated in isolation of
the feasibility of large-scale CDR and that the failure of the overshoot
promise will lead to prolonged peak-shaving, masking an ever-rising
climate debt. Overshoot and peak-shaving scenarios should not be
presented as a secured feasible investment, but rather as a high-risk
speculation betting on insecure promises. Obscuring the riskiness of
such scenarios is a precipitous step towards escalating a climate debt
crisis
Heavy-Fermion Formation at the Metal-to-Insulator Transition in GdSrTiO
The perovskite-like transition-metal oxide GdSrTiO is
investigated by measurements of resistivity, specific-heat, and electron
paramagnetic resonance (EPR). Approaching the metal-to-insulator transition
from the metallic regime (), the Sommerfeld coefficient of
the specific heat becomes strongly enhanced and the resistivity increases
quadratically at low temperatures, which both are fingerprints of strong
electronic correlations. The temperature dependence of the dynamic
susceptibility, as determined from the Gd-EPR linewidth, signals the
importance of strong spin fluctuations, as observed in heavy-fermion compounds.Comment: 4pages, 3 figure
Observing the Sun with Atacama Large Millimeter/submillimeter Array (ALMA): High Resolution Interferometric Imaging
Observations of the Sun at millimeter and submillimeter wavelengths offer a
unique probe into the structure, dynamics, and heating of the chromosphere; the
structure of sunspots; the formation and eruption of prominences and filaments;
and energetic phenomena such as jets and flares. High-resolution observations
of the Sun at millimeter and submillimeter wavelengths are challenging due to
the intense, extended, low- contrast, and dynamic nature of emission from the
quiet Sun, and the extremely intense and variable nature of emissions
associated with energetic phenomena. The Atacama Large Millimeter/submillimeter
Array (ALMA) was designed with solar observations in mind. The requirements for
solar observations are significantly different from observations of sidereal
sources and special measures are necessary to successfully carry out this type
of observations. We describe the commissioning efforts that enable the use of
two frequency bands, the 3 mm band (Band 3) and the 1.25 mm band (Band 6), for
continuum interferometric-imaging observations of the Sun with ALMA. Examples
of high-resolution synthesized images obtained using the newly commissioned
modes during the solar commissioning campaign held in December 2015 are
presented. Although only 30 of the eventual 66 ALMA antennas were used for the
campaign, the solar images synthesized from the ALMA commissioning data reveal
new features of the solar atmosphere that demonstrate the potential power of
ALMA solar observations. The ongoing expansion of ALMA and solar-commissioning
efforts will continue to enable new and unique solar observing capabilities.Comment: 22 pages, 12 figures, accepted for publication in Solar Physic
What Does The Korringa Ratio Measure?
We present an analysis of the Korringa ratio in a dirty metal, emphasizing
the case where a Stoner enhancement of the uniform susceptibilty is present. We
find that the relaxation rates are significantly enhanced by disorder, and that
the inverse problem of determining the bare density of states from a study of
the change of the Knight shift and relaxation rates with some parameter, such
as pressure, has rather constrained solutions, with the disorder playing an
important role. Some preliminary applications to the case of chemical
substitution in the RbKC family of superconductors is
presented and some other relevant systems are mentioned.Comment: 849, Piscataway, New Jersey 08855 24 June 199
Observing the Sun with the Atacama Large Millimeter-submillimeter Array (ALMA): Fast-Scan Single-Dish Mapping
The Atacama Large Millimeter-submillimeter Array (ALMA) radio telescope has
commenced science observations of the Sun starting in late 2016. Since the Sun
is much larger than the field of view of individual ALMA dishes, the ALMA
interferometer is unable to measure the background level of solar emission when
observing the solar disk. The absolute temperature scale is a critical
measurement for much of ALMA solar science, including the understanding of
energy transfer through the solar atmosphere, the properties of prominences,
and the study of shock heating in the chromosphere. In order to provide an
absolute temperature scale, ALMA solar observing will take advantage of the
remarkable fast-scanning capabilities of the ALMA 12m dishes to make
single-dish maps of the full Sun. This article reports on the results of an
extensive commissioning effort to optimize the mapping procedure, and it
describes the nature of the resulting data. Amplitude calibration is discussed
in detail: a path that utilizes the two loads in the ALMA calibration system as
well as sky measurements is described and applied to commissioning data.
Inspection of a large number of single-dish datasets shows significant
variation in the resulting temperatures, and based on the temperature
distributions we derive quiet-Sun values at disk center of 7300 K at lambda=3
mm and 5900 K at lambda=1.3 mm. These values have statistical uncertainties of
order 100 K, but systematic uncertainties in the temperature scale that may be
significantly larger. Example images are presented from two periods with very
different levels of solar activity. At a resolution of order 25 arcsec, the 1.3
mm wavelength images show temperatures on the disk that vary over about a 2000
K range.Comment: Solar Physics, accepted: 24 pages, 13 figure
Unique Spin Dynamics and Unconventional Superconductivity in the Layered Heavy Fermion Compound CeIrIn_5:NQR Evidence
We report measurements of the ^{115}In nuclear spin-lattice relaxation rate
(1/T_1) between T=0.09 K and 100 K in the new heavy fermion (HF) compound
CeIrIn_5. At 0.4 K < T < 100 K, 1/T_1 is strongly T-dependent, which indicates
that CeIrIn_5 is much more itinerant than known Ce-based HFs. We find that
1/T_1T, subtracting that for LaIrIn_5, follows a 1/(T+\theta)^{3/4} variation
with \theta=8 K. We argue that this novel feature points to anisotropic, due to
a layered crystal structure, spin fluctuations near a magnetic ordering. The
bulk superconductivity sets in at 0.40 K below which the coherence peak is
absent and 1/T_1 follows a T^3 variation, which suggests unconventional
superconductivity with line-node gap.Comment: minor changes, appeared in PRL (4 pages, 4 figures
High-Mass Cloud Cores in the eta Carinae Giant Molecular Cloud
We carried out an unbiased survey for massive dense cores in the giant
molecular cloud associated with eta Carinae with the NANTEN telescope in 12CO,
13CO, and C18O 1-0 emission lines. We identified 15 C18O cores. Two of the 15
cores are associated with IRAS point sources whose luminosities are larger than
10^4 Lo, which indicates that massive star formation is occuring within these
cores. Five cores including the two with IRAS sources are associated with MSX
point sources. We detected H13CO+ (1-0) emission toward 4 C18O cores, one of
which is associated with neither IRAS nor MSX point sources. This core shows
the presence of a bipolar molecular outflow in 12CO (2-1), which indicates that
star formation is also occuring in the core. In total, six C18O cores out of 15
are experienced star formation, and at least 2 of 15 are massive-star forming
cores in the eta Car GMC. We found that massive star formation occurs
preferentially in cores with larger column density, mass, number density, and
smaller ratio of virial mass to LTE mass Mvir/M. We also found that the cores
in the eta Car GMC are characterized by large line width and Mvir/M on average
compared to the cores in other GMCs. We investigated the origin of a large
amount of turbulence in the eta Car GMC. We propose the possibility that the
large turbulence was pre-existing when the GMC was formed, and is now
dissipating. Mechanisms such as multiple supernova explosions in the Carina
flare supershell may have contributed to form a GMC with a large amount of
turbulence.Comment: 41 pages, including 11 fugures and 9 tables. Accepted by ApJ. Author
changed. Paper with high resolution figures is available at
http://astrol.cias.osakafu-u.ac.jp/~yonekura/work/paper/etaCar
Hall Effect and Resistivity in High-Tc Superconductors: The Conserving Approximation
The Hall coefficient (R_H) of high-Tc cuprates in the normal state shows the
striking non-Fermi liquid behavior: R_H follows a Curie-Weiss type temperature
dependence, and |R_H|>>1/|ne| at low temperatures in the under-doped compounds.
Moreover, R_H is positive for hole-doped compounds and is negative for
electron-doped ones, although each of them has a similar hole-like Fermi
surface. In this paper, we give the explanation of this long-standing problem
from the standpoint of the nearly antiferromagnetic (AF) Fermi liquid. We
consider seriously the vertex corrections for the current which are
indispensable to satisfy the conservation laws, which are violated within the
conventional Boltzmann transport approximation. The obtained total current J_k
takes an enhanced value and is no more perpendicular to the Fermi surface due
to the strong AF fluctuations. By virtue of this mechanism, the anomalous
behavior of R_H in high-Tc cuprates is neutrally explained. We find that both
the temperature and the (electron, or hole) doping dependences of R_H in
high-T_c cuprates are reproduced well by numerical calculations based on the
fluctuation-exchange (FLEX) approximation, applied to the single-band Hubbard
model. We also discuss the temperature dependence of R_H in other nearly AF
metals, e.g., V_2O_3, kappa-BEDT-TTF organic superconductors, and heavy fermion
systems close to the AF phase boundary.Comment: 19 pages, to appear in Phys. Rev. B, No.59, Vol.22, 199
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