9,310 research outputs found
Municipal Solid Waste Regulation: An Ineffective Solution to a National Problem
The volume of solid waste, particularly in urban areas, is increasing, and both public heath and the environment are in jeopardy because disposal methods have not kept pace. This Comment examines the historical role that municipalities have played in providing adequate methods for solid waste disposal, emphasizes the traditional methods of zoning and critiques the effectiveness of municipal regulation. It reviews recent federal and state solid waste management acts and analyzes the issue of preemption. This Comment also discusses the constitutionality of state and municipal waste bans. In conclusion, this Comment recommends more effective methods for states and municipalities to pursue in solving the problems of solid waste disposal
Photospheric activity, rotation, and star-planet interaction of the planet-hosting star CoRoT-6
The CoRoT satellite has recently discovered a hot Jupiter that transits
across the disc of a F9V star called CoRoT-6 with a period of 8.886 days. We
model the photospheric activity of the star and use the maps of the active
regions to study stellar differential rotation and the star-planet interaction.
We apply a maximum entropy spot model to fit the optical modulation as observed
by CoRoT during a uninterrupted interval of about 140 days. Photospheric active
regions are assumed to consist of spots and faculae in a fixed proportion with
solar-like contrasts. Individual active regions have lifetimes up to 30-40
days. Most of them form and decay within five active longitudes whose different
migration rates are attributed to the stellar differential rotation for which a
lower limit of \Delta \Omega / \Omega = 0.12 \pm 0.02 is obtained. Several
active regions show a maximum of activity at a longitude lagging the
subplanetary point by about 200 degrees with the probability of a chance
occurrence being smaller than 1 percent. Our spot modelling indicates that the
photospheric activity of CoRoT-6 could be partially modulated by some kind of
star-planet magnetic interaction, while an interaction related to tides is
highly unlikely because of the weakness of the tidal force.Comment: 9 pages, 7 figures, accepted to Astronomy & Astrophysic
Long-term radial-velocity variations of the Sun as a star: The HARPS view
Stellar radial velocities play a fundamental role in the discovery of
extrasolar planets and the measurement of their physical parameters as well as
in the study of stellar physical properties. We investigate the impact of the
solar activity on the radial velocity of the Sun using the HARPS spectrograph
to obtain measurements that can be directly compared with those acquired in the
extrasolar planet search programs. We use the Moon, the Galilean satellites,
and several asteroids as reflectors to measure the radial velocity of the Sun
as a star and correlate it with disc-integrated chromospheric and magnetic
indexes of solar activity that are similar to stellar activity indexes. We
discuss in detail the systematic effects that affect our measurements and the
methods to account for them. We find that the radial velocity of the Sun as a
star is positively correlated with the level of its chromospheric activity at
about 95 percent significance level. The amplitude of the long-term variation
measured in the 2006-2014 period is 4.98 \pm 1.44 m/s, in good agreement with
model predictions. The standard deviation of the residuals obtained by
subtracting a linear best fit is 2.82 m/s and is due to the rotation of the
reflecting bodies and the intrinsic variability of the Sun on timescales
shorter than the activity cycle. A correlation with a lower significance is
detected between the radial velocity and the mean absolute value of the
line-of-sight photospheric magnetic field flux density. Our results confirm
similar correlations found in other late-type main-sequence stars and provide
support to the predictions of radial velocity variations induced by stellar
activity based on current models.Comment: 11 pages, 7 figures, 2 tables, 1 Appendix; accepted by Astronomy and
Astrophysic
Novel schedule for treatment of inflammatory breast cancer
Inflammatory breast cancer (IBC) is the most aggressive form of this tumor, with the clinical and biological characteristics of a rapidly proliferating disease. This tumor is always diagnosed at advanced stages, atleast stage IIIB (locally advanced), so its management requires an integrated multidisciplinary approach with a systemic therapy followed by surgery and radiation therapy. Patients with IBC usually have a worse prognosis but the achievement of a pathologic complete response after neoadjuvant chemotherapy may have good rates of overall survival. We present the case of a 47 year old women with IBC, luminal B and with high proliferative index; she was successfully treated with a sequential schedule of chemotherapy (anthracyclines dose-dense/carboplatin+ taxane/Cyclophosphamide Methotrexate Fluorouracil), hormone-therapy, complementary radiotherapy and finally surgery until the achievement of a complete clinical and pathological response.
Luminal B inflammatory breast cancer with high proliferation index can benefit from sequential schedules of neoadjuvant chemotherapy and hormonal treatment and this can result in pathological complete response
Properties of starspots on CoRoT-2
As a planet eclipses its parent star, a dark spot on the surface of the star
may be occulted, causing a detectable variation in the light curve. A total of
77 consecutive transit light curves of CoRoT-2 were observed with a high
temporal resolution of 32 s, corresponding to an uninterrupted period of 134
days. By analyzing small intensity variations in the transit light curves, it
was possible to detect and characterize spots at fixed positions (latitude and
longitude) on the surface of the star. The model used simulates planetary
transits and enables the inclusion of spots on the stellar surface with
different sizes, intensities (i.e. temperatures), and positions. Fitting the
data by this model, it is possible to infer the spots physical characteristics.
The fits were either in spot longitude and radius, with a fixed intensity, or
in spots longitude and intensity, for spots of constant size. Before the
modeling of the spots were performed, the planetary radius relative to the star
radius was estimated by fitting the deepest transit to minimize the effect of
spots. A slightly larger (3%) radius, 0.172 Rstar, resulted instead of the
previously reported 0.1667 Rstar . The fitting of the transits yield spots, or
spot groups, with sizes of ranging from 0.2 to 0.7 planet radius, Rp, with a
mean of (0.41 +/- 0.13) Rp (~100,000 km), resulting in a stellar area covered
by spots within the transit latitudes of 10-20%. The intensity varied from 0.4
to 0.9 of the disk center intensity, Ic, with a mean of (0.60 +/- 0.19) Ic,
which can be converted to temperature by assuming an effective temperature of
5625 K for the stellar photosphere, the spots temperature ranges mainly from
3600 to 5000 K. The results from the spot modeling are in agreement with those
found for magnetic activity analysis from out of transit data of the same star.Comment: 7 pages, 11 figure
Measuring stellar differential rotation with high-precision space-borne photometry
We introduce a method of measuring a lower limit to the amplitude of surface
differential rotation from high-precision, evenly sampled photometric time
series. It is applied to main-sequence late-type stars whose optical flux
modulation is dominated by starspots. An autocorrelation of the time series was
used to select stars that allow an accurate determination of starspot rotation
periods. A simple two-spot model was applied together with a Bayesian
information criterion to preliminarily select intervals of the time series
showing evidence of differential rotation with starspots of almost constant
area. Finally, the significance of the differential rotation detection and a
measurement of its amplitude and uncertainty were obtained by an a posteriori
Bayesian analysis based on a Monte Carlo Markov Chain approach. We applied our
method to the Sun and eight other stars for which previous spot modelling had
been performed to compare our results with previous ones. We find that
autocorrelation is a simple method for selecting stars with a coherent
rotational signal that is a prerequisite for successfully measuring
differential rotation through spot modelling. For a proper Monte Carlo Markov
Chain analysis, it is necessary to take the strong correlations among different
parameters that exist in spot modelling into account. For the planet-hosting
star Kepler-30, we derive a lower limit to the relative amplitude of the
differential rotation of \Delta P / P = 0.0523 \pm 0.0016. We confirm that the
Sun as a star in the optical passband is not suitable for measuring
differential rotation owing to the rapid evolution of its photospheric active
regions. In general, our method performs well in comparison to more
sophisticated and time-consuming approaches.Comment: Accepted to Astronomy and Astrophysics, 15 pages, 13 figures, 4
tables and an Appendi
A match coefficient approach for damage imaging in structural components by ultrasonic synthetic aperture focus
Ultrasonic Synthetic Aperture Focus (SAF) techniques are commonly used to image structural defects. In this paper, a variation of SAF based on ideas borrowed from Matched Field Processing (MFP) is evaluated to reduce artifacts and sidelobes of the resulting images. In particular, instead of considering the full RF ultrasonic waveforms for the SAF time backpropagation, only selected features from the waveforms are utilized to form a “data vector” and a “replica” (expected) vector of MFP. These vectors are adaptive for the pair of transmitter-receiver and the focus point. The image is created as a matched filter between these two vectors. Experimental results are shown for an isotropic and homogenous metallic plate with simulated defects, probed by six piezoelectric patches used as receivers or transmitters
Searching for star-planet magnetic interaction in CoRoT observations
Close-in massive planets interact with their host stars through tidal and
magnetic mechanisms. In this paper, we review circumstantial evidence for
star-planet interaction as revealed by the photospheric magnetic activity in
some of the CoRoT planet-hosting stars, notably CoRoT-2, CoRoT-4, and CoRoT-6.
The phenomena are discussed in the general framework of activity-induced
features in stars accompanied by hot Jupiters. The theoretical mechanisms
proposed to explain the activity enhancements possibly related with hot Jupiter
are also briefly reviewed with an emphasis on the possible effects at
photospheric level. The unique advantages of CoRoT and Kepler observations to
test these models are pointed out.Comment: Invited review paper accepted by Astrophysics and Space Science, 13
pages, 5 figure
Irreversible magnetization under rotating fields and lock-in effect on ErBa_2Cu_3O_7 single crystal with columnar defects
We have measured the irreversible magnetization M_i of an ErBa_2Cu_3O_7
single crystal with columnar defects (CD), using a technique based on sample
rotation under a fixed magnetic field H. This method is valid for samples whose
magnetization vector remains perpendicular to the sample surface over a wide
angle range - which is the case for platelets and thin films - and presents
several advantages over measurements of M_L(H) loops at fixed angles. The
resulting M_i(\Theta) curves for several temperatures show a peak in the CD
direction at high fields. At lower fields, a very well defined plateau
indicative of the vortex lock-in to the CD develops. The H dependence of the
lock-in angle \phi_L follows the H^{-1} theoretical prediction, while the
temperature dependence is in agreement with entropic smearing effects
corresponding to short range vortex-defects interactions.Comment: 7 pages, 6 figures, to be published in Phys. Rev.
Mitochondrial Function as a Determinant of Life Span
Average human life expectancy has progressively increased over many decades largely due to improvements in nutrition, vaccination, antimicrobial agents, and effective treatment/prevention of cardiovascular disease, cancer, etc. Maximal life span, in contrast, has changed very little. Caloric restriction (CR) increases maximal life span in many species, in concert with improvements in mitochondrial function. These effects have yet to be demonstrated in humans, and the duration and level of CR required to extend life span in animals is not realistic in humans. Physical activity (voluntary exercise) continues to hold much promise for increasing healthy life expectancy in humans, but remains to show any impact to increase maximal life span. However, longevity in Caenorhabditis elegans is related to activity levels, possibly through maintenance of mitochondrial function throughout the life span. In humans, we reported a progressive decline in muscle mitochondrial DNA abundance and protein synthesis with age. Other investigators also noted age-related declines in muscle mitochondrial function, which are related to peak oxygen uptake. Long-term aerobic exercise largely prevented age-related declines in mitochondrial DNA abundance and function in humans and may increase spontaneous activity levels in mice. Notwithstanding, the impact of aerobic exercise and activity levels on maximal life span is uncertain. It is proposed that age-related declines in mitochondrial content and function not only affect physical function, but also play a major role in regulation of life span. Regular aerobic exercise and prevention of adiposity by healthy diet may increase healthy life expectancy and prolong life span through beneficial effects at the level of the mitochondrion
- …