Toward Rational Regulation of Marijuana in the United States: FDA's Role in Consumer Choice and Safety

The Food and Drug Administration is an agency dedicated to maintaining the health and safety of the American public. For as long as people have been purchasing and consuming foods and drugs there have been the problems of adulteration and imperfect consumer information. In some cases, FDA acts to protect the consumer against dangers he or she cannot protect him or herself from by prohibiting access to food containing invisible pathogens or drugs intended for specific maladies beyond lay diagnosis. In other cases, FDA decides the best approach is to allow for informed consumer choice through labeling and disclosure requirements. Generally, the latter approach is applied to areas of aesthetic choice, but even when products are potentially harmful (containing saturated fats, cholesterol, nicotine, caffeine, saccharine, preservatives) FDA is reluctant to ban them. Ultimate choice is left to the informed consumer, especially in areas of subjective choice, e.g. whether to consume a lollipop with a worm inside it or chocolate covered ants

On characterising the variability properties of X-ray light curves from active galaxies

We review some practical aspects of measuring the amplitude of variability in `red noise' light curves typical of those from Active Galactic Nuclei (AGN). The quantities commonly used to estimate the variability amplitude in AGN light curves, such as the fractional rms variability amplitude, F_var, and excess variance, sigma_XS^2, are examined. Their statistical properties, relationship to the power spectrum, and uses for investigating the nature of the variability processes are discussed. We demonstrate that sigma_XS^2 (or similarly F_var) shows large changes from one part of the light curve to the next, even when the variability is produced by a stationary process. This limits the usefulness of these estimators for quantifying differences in variability amplitude between different sources or from epoch to epoch in one source. Some examples of the expected scatter in the variance are tabulated for various typical power spectral shapes, based on Monte Carlo simulations. The excess variance can be useful for comparing the variability amplitudes of light curves in different energy bands from the same observation. Monte Carlo simulations are used to derive a description of the uncertainty in the amplitude expected between different energy bands (due to measurement errors). Finally, these estimators are used to demonstrate some variability properties of the bright Seyfert 1 galaxy Markarian 766. The source is found to show a strong, linear correlation between rms amplitude and flux, and to show significant spectral variability.Comment: 14 pages. 12 figures. Accepted for publication in MNRA

X-ray vs. Optical Variations in the Seyfert 1 Nucleus NGC 3516: A Puzzling Disconnectedness

We present optical broadband (B and R) observations of the Seyfert 1 nucleus NGC 3516, obtained at Wise Observatory from March 1997 to March 2002, contemporaneously with X-ray 2-10 keV measurements with RXTE. With these data we increase the temporal baseline of this dataset to 5 years, more than triple to the coverage we have previously presented for this object. Analysis of the new data does not confirm the 100-day lag of X-ray behind optical variations, tentatively reported in our previous work. Indeed, excluding the first year's data, which drive the previous result, there is no significant correlation at any lag between the X-ray and optical bands. We also find no correlation at any lag between optical flux and various X-ray hardness ratios. We conclude that the close relation observed between the bands during the first year of our program was either a fluke, or perhaps the result of the exceptionally bright state of NGC 3516 in 1997, to which it has yet to return. Reviewing the results of published joint X-ray and UV/optical Seyfert monitoring programs, we speculate that there are at least two components or mechanisms contributing to the X-ray continuum emission up to 10 keV: a soft component that is correlated with UV/optical variations on timescales >1 day, and whose presence can be detected when the source is observed at low enough energies (about 1 keV), is unabsorbed, or is in a sufficiently bright phase; and a hard component whose variations are uncorrelated with the UV/optical.Comment: 9 pages, AJ, in pres

Simultaneous EUV and X-ray variability of NGC 4051

We present a flux variability study of simultaneous RXTE and EUVE observations of the highly variable Seyfert galaxy NGC4051. We find a strong correlation between variability in the EUV and medium energy X-ray bands,indicating that both are sampling the same power-law continuum. The lag between the two bands is less than 20 ks and, depending on model assumptions, may be <1 ks. We examine the consequences of such a small lag in the context of simple Comptonisation models for the production of the power-law continuum. A lag of <1 ks implies that the size of the Comptonising region is less than 20 Schwarzschild radii for a black hole of mass >1E6 solar masses.Comment: 8 pages, accepted for publication in MNRA

An RXTE Survey of Long-Term X-ray Variability in Seyfert 1 Galaxies

Data from the first three years of RXTE observations have been systematically analyzed to yield a set of 300 day, 2-10 keV light curves with similarly uniform, ~5 day sampling, for a total of nine Seyfert 1 galaxies. This is the first X-ray variability survey to consistently probe time scales longer than a few days in a large number of AGN. Comparison with ASCA data covering a similar band but much shorter (~1 day) time scales shows that all the AGN are more strongly variable on long time scales than on short time scales. This increase is greatest for the highest-luminosity sources. The well-known anticorrelation between source luminosity and variability amplitude is both stronger and shallower in power-law slope when measured on long time scales. This is consistent with a picture in which the X-ray variability of Seyfert 1s can be can be described by a single, universal fluctuation power density shape for which the cutoff moves to longer time scales for higher luminosity sources. All of the Seyfert 1s exhibit stronger variability in the relatively soft 2-4 keV band than in the harder 7-10 keV band. This effect is much too pronounced to be explained by simple models based on either the dilution of the power-law continuum by the Compton reflection component or on the hard X-rays being produced in a static, pair-dominated, plane-parallel Comptonizing corona.Comment: 18 pages, 9 figures. Accepted for publication in the Astrophysical Journa

Rapid recurrence and radiographic progression of sarcomatoid renal cell carcinoma

© 2017 Sarcomatoid renal cell carcinoma (sRCC) is an aggressive variant of renal cell carcinoma (RCC) that has a significantly lower overall survival. Even after prompt surgical extirpation, this histologic variant progresses rapidly. We present a case of an early recurrence and rapid progression of sRCC despite successful radical resection

Long-Term X-ray Spectral Variability in Seyfert 1 Galaxies

Direct time-resolved spectral fitting has been performed on continuous RXTE monitoring of seven Seyfert 1 galaxies in order to study their broadband spectral variability and Fe K alpha variability characteristics on time scales of days to years. Variability in the Fe K alpha line is not detected in some objects but is present in others, e.g., in NGC 3516, NGC 4151 and NGC 5548 there are systematic decreases in line flux by factors of ~2-5 over 3-4 years. The Fe K alpha line varies less strongly than the broadband continuum, but, like the continuum, exhibits stronger variability towards longer time scales. Relatively less model-dependent broadband fractional variability amplitude (Fvar) spectra also show weaker line variability compared to the continuum variability. Comparable systematic long-term decreases in the line and continuum are present in NGC 5548. Overall, however, there is no evidence for correlated variability between the line and continuum, severely challenging models in which the line tracks continuum variations modified only by a light-travel time delay. Local effects such as the formation of an ionized skin at the site of line emission may be relevant. The spectral fitting and Fvar spectra both support spectral softening as continuum flux increases.Comment: Accepted for publication in ApJ. 29 page

Multi-band optical micro-variability observations of BL Lacertae

We have observed BL Lacertae in the B, R and I bands for 2 nights in July, 1999, and 3 nights in July, 2001. The observations resulted in almost evenly sampled light curves, with an average sampling interval of ~5 min. The source is significantly variable in all bands. On average, the variability amplitude increases from ~5% in the I band, to ~5.5% in the R and ~6.5% in the B band light curves. The rising and decaying time scales are comparable within each band, but they increase from the B, to R and I band light curves. The optical power spectrum shows a red noise component with a slope of ~ -2. Cross-correlation analysis shows that in most cases the delay between the variations in the B and I band light curves is less than ~ 0.4 hrs. The cross-correlation functions are asymmetric, implying complex delays of the I band variations with respect to the B band variations. Furthermore, in one case we find that the I band variations are significantly delayed (by ~0.2 hrs) with respect to the B band variations. We also detect significant spectral variations: the spectrum becomes steeper as the flux increases, and the flattest spectral index corresponds to the maximum B band flux. Our results imply that the fast, intra-night variations of the source correspond to perturbations of different regions in the jet which cause localized injections of relativistic particles on time scales much sorter that the average sampling interval of the light curves. The variations are controlled by the cooling and light crossing time scales, which are probably comparable.Comment: Accepted for publication in A&