151 research outputs found
Ion-scale spectral break of solar wind turbulence at high and low beta
The power spectrum of magnetic fluctuations in the solar wind at 1 AU displays a break between two power laws in the range of spacecraft-frame frequencies 0.1 to 1 Hz. These frequencies correspond to spatial scales in the plasma frame near the proton gyroradius ρi and proton inertial length di. At 1 AU it is difficult to determine which of these is associated with the break, since [Formula: see text] and the perpendicular ion plasma beta is typically β⊥i∼1. To address this, several exceptional intervals with β⊥i≪1 and β⊥i≫1 were investigated, during which these scales were well separated. It was found that for β⊥i≪1 the break occurs at di and for β⊥i≫1 at ρi, i.e., the larger of the two scales. Possible explanations for these results are discussed, including Alfvén wave dispersion, damping, and current sheets
Parallel-propagating Fluctuations at Proton-kinetic Scales in the Solar Wind are Dominated by Kinetic Instabilities
We use magnetic helicity to characterise solar wind fluctuations at
proton-kinetic scales from Wind observations. For the first time, we separate
the contributions to helicity from fluctuations propagating at angles
quasi-parallel and oblique to the local mean magnetic field, . We
find that the helicity of quasi-parallel fluctuations is consistent with
Alfv\'en-ion cyclotron and fast magnetosonic-whistler modes driven by proton
temperature anisotropy instabilities and the presence of a relative drift
between -particles and protons. We also find that the helicity of
oblique fluctuations has little dependence on proton temperature anisotropy and
is consistent with fluctuations from the anisotropic turbulent cascade. Our
results show that parallel-propagating fluctuations at proton-kinetic scales in
the solar wind are dominated by proton temperature anisotropy instabilities and
not the turbulent cascade. We also provide evidence that the behaviour of
fluctuations at these scales is independent of the origin and macroscopic
properties of the solar wind.Comment: Accepted for publication in ApJL. 6 Pages, 3 figures, 1 tabl
Mapping a forest mosaic – A comparison of vegetation and bird distributions using geographic boundary analysis
Many areas of ecological inquiry require the ability to detect and characterize change in ecological variables across both space and time. The purpose of this study was to investigate ways in which geographic boundary analysis techniques could be used to characterize the pattern of change over space in plant distributions in a forested wetland mosaic. With vegetation maps created using spatially constrained clustering and difference boundary delineation, we examined similarities between the identified boundaries in plant distributions and the occurrence of six species of songbirds. We found that vegetation boundaries were significantly cohesive, suggesting one or more crisp vegetation transition zones exist in the study site. Smaller, less cohesive boundary areas also provided important information about patterns of treefall gaps and dense patches of understory within the study area. Boundaries for songbird abundance were not cohesive, and bird and vegetation difference boundaries did not show significant overlap. However, bird boundaries did overlap significantly with vegetation cluster boundaries. Vegetation clusters delineated using constrained clustering techniques have the potential to be very useful for stratifying bird abundance data collected in different sections of the study site, which could be used to improve the efficiency of monitoring efforts for rare bird species.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43882/1/11258_2004_Article_358203.pd
A zone of preferential ion heating extends tens of solar radii from Sun
The extreme temperatures and non-thermal nature of the solar corona and solar
wind arise from an unidentified physical mechanism that preferentially heats
certain ion species relative to others. Spectroscopic indicators of unequal
temperatures commence within a fraction of a solar radius above the surface of
the Sun, but the outer reach of this mechanism has yet to be determined. Here
we present an empirical procedure for combining interplanetary solar wind
measurements and a modeled energy equation including Coulomb relaxation to
solve for the typical outer boundary of this zone of preferential heating.
Applied to two decades of observations by the Wind spacecraft, our results are
consistent with preferential heating being active in a zone extending from the
transition region in the lower corona to an outer boundary 20-40 solar radii
from the Sun, producing a steady state super-mass-proportional
-to-proton temperature ratio of . Preferential ion heating
continues far beyond the transition region and is important for the evolution
of both the outer corona and the solar wind. The outer boundary of this zone is
well below the orbits of spacecraft at 1 AU and even closer missions such as
Helios and MESSENGER, meaning it is likely that no existing mission has
directly observed intense preferential heating, just residual signatures. We
predict that {Parker Solar Probe} will be the first spacecraft with a perihelia
sufficiently close to the Sun to pass through the outer boundary, enter the
zone of preferential heating, and directly observe the physical mechanism in
action.Comment: 11 pages, 7 figures, accepted for publication in the Astrophysical
Journal on 1 August 201
ENT management of children with adenotonsillar disease during COVID-19 pandemic : ready to start again?
Clinical manifestations of COVID-19 in children are milder, but the real burden of disease is unknown. After the lockdown, in our Region Lombardia we have been requested to progressively resume medical services including outpatient assessment and priority surgery. Therefore, we screened surgical waiting lists with identification of 47 children candidates to priority surgery (among 358). No homogeneous national health surveillance/screening programs are ongoing or have been conceived to test susceptible population among children/healthcare workers in preparation of coming down to routinely daily activities, and diagnostic strategies are not completely accurate in children. So, restoring medical services now might be untimely
Coronal electron temperature in the protracted solar minimum, the cycle 24 mini maximum, and over centuries
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106800/1/jgra50869.pd
Infected chronic ischemic wound topically treated with a multi-strain probiotic formulation: A novel tailored treatment strategy
Background A wide debate is ongoing regarding the role of cutaneous dysbiosis in the pathogenesis and evolution of difficult-to-treat chronic wounds. Nowadays, probiotic treatment considered as an useful tool to counteract dysbiosis but the evidence in regard to their therapeutic use in the setting of difficult-to-treat cutaneous ulcers is still poor. Aim: clinical report An 83-year-old woman suffering a critical limb ischemia and an infected difficult-to-treat ulcerated cutaneous lesion of the right leg, was complementary treated with local application of a mixture of probiotic bacteria. Methods Microbiological and metabolomic analysis were conducted on wound swabs obtained before and after bacteriotherapy. Results During the treatment course, a progressive healing of the lesion was observed with microbiological resolution of the polymicrobial infection of the wound. Metabolomic analysis showed a significant difference in the local concentration of propionate, 2-hydroxyisovalerate, 2-oxoisocaproate, 2,3-butanediol, putrescine, thymine, and trimethylamine before and after bacteriotherapy. Conclusion The microbiological and metabolomic results seem to confirm the usefulness of complementary probiotic treatment in difficult-to-treat infected wounds. Further investigations are needed to confirm these preliminary findings
Infected chronic ischemic wound topically treated with a multi-strain probiotic formulation: A novel tailored treatment strategy
Background A wide debate is ongoing regarding the role of cutaneous dysbiosis in the pathogenesis and evolution of difficult-to-treat chronic wounds. Nowadays, probiotic treatment considered as an useful tool to counteract dysbiosis but the evidence in regard to their therapeutic use in the setting of difficult-to-treat cutaneous ulcers is still poor. Aim: clinical report An 83-year-old woman suffering a critical limb ischemia and an infected difficult-to-treat ulcerated cutaneous lesion of the right leg, was complementary treated with local application of a mixture of probiotic bacteria. Methods Microbiological and metabolomic analysis were conducted on wound swabs obtained before and after bacteriotherapy. Results During the treatment course, a progressive healing of the lesion was observed with microbiological resolution of the polymicrobial infection of the wound. Metabolomic analysis showed a significant difference in the local concentration of propionate, 2-hydroxyisovalerate, 2-oxoisocaproate, 2,3-butanediol, putrescine, thymine, and trimethylamine before and after bacteriotherapy. Conclusion The microbiological and metabolomic results seem to confirm the usefulness of complementary probiotic treatment in difficult-to-treat infected wounds. Further investigations are needed to confirm these preliminary findings
The statistical properties of solar wind temperature parameters near 1 AU
We present a long-duration (10 years) statistical analysis of the
temperatures, plasma betas, and temperature ratios for the electron, proton,
and alpha-particle populations observed by the \emph{Wind} spacecraft near 1
AU. The mean(median) scalar temperatures are
12.2(11.9) eV, 12.7(8.6) eV, and
23.9(10.8) eV. The mean(median) total
plasma betas are 2.31(1.09),
1.79(1.05), and 0.17(0.05). The mean(median) temperature ratios are
1.64(1.27),
1.24(0.82), and
2.50(1.94). We also examined these parameters during time intervals that
exclude interplanetary (IP) shocks, times within the magnetic obstacles (MOs)
of interplanetary coronal mass ejections (ICMEs), and times that exclude MOs.
The only times that show significant alterations to any of the parameters
examined are those during MOs. In fact, the only parameter that does not show a
significant change during MOs is the electron temperature. Although each
parameter shows a broad range of values, the vast majority are near the median.
We also compute particle-particle collision rates and compare to effective
wave-particle collision rates. We find that, for reasonable assumptions of wave
amplitude and occurrence rates, the effect of wave-particle interactions on the
plasma is equal to or greater than the effect of Coulomb collisions. Thus,
wave-particle interactions should not be neglected when modeling the solar
wind.Comment: 23 pages, 3 figures, 6 tables, submitted to Astrophys. J. Suppl. on
Jan. 30, 201
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