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  • 1
    Publication Date: 2011-10-08
    Description: Gene regulatory circuits can use dynamic, and even stochastic, strategies to respond to environmental conditions. We examined activation of the general stress response mediated by the alternative sigma factor, sigma(B), in individual Bacillus subtilis cells. We observed that energy stress activates sigma(B) in discrete stochastic pulses, with increasing levels of stress leading to higher pulse frequencies. By perturbing and rewiring the endogenous system, we found that this behavior results from three key features of the sigma(B) circuit: an ultrasensitive phosphorylation switch; stochasticity ("noise"), which activates that switch; and a mixed (positive and negative) transcriptional feedback, which can both amplify a pulse and switch it off. Together, these results show how prokaryotes encode signals using stochastic pulse frequency modulation through a compact regulatory architecture.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4100694/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4100694/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Locke, James C W -- Young, Jonathan W -- Fontes, Michelle -- Hernandez Jimenez, Maria Jesus -- Elowitz, Michael B -- P50 GM068763/GM/NIGMS NIH HHS/ -- R01 GM079771/GM/NIGMS NIH HHS/ -- R01GM079771/GM/NIGMS NIH HHS/ -- Howard Hughes Medical Institute/ -- New York, N.Y. -- Science. 2011 Oct 21;334(6054):366-9. doi: 10.1126/science.1208144. Epub 2011 Oct 6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute, Division of Biology and Bioengineering, Broad Center, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21979936" target="_blank"〉PubMed〈/a〉
    Keywords: Bacillus subtilis/*genetics/metabolism/*physiology ; Bacterial Proteins/genetics/*metabolism ; Carrier Proteins/genetics/metabolism ; Feedback, Physiological ; Gene Expression Regulation, Bacterial ; *Gene Regulatory Networks ; Mycophenolic Acid/pharmacology ; Phosphoric Monoester Hydrolases/genetics/metabolism ; Phosphorylation ; Protein-Serine-Threonine Kinases/genetics/metabolism ; Sigma Factor/genetics/*metabolism ; Stochastic Processes ; *Stress, Physiological ; Transcription, Genetic
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2011-08-24
    Description: Photoelectric lightcurve observations in the V band, together with estimates of the mean and maximum reduced magnitudes, are presented for 59 different asteroids; 15 new or significantly revised periods are reported. While fits are generally good for objects with moderate phase-relation slope, poor quality fits remain among the highest and lowest albedo objects studied in virtue of their respectively shallow and steep sloping-phase curves.
    Keywords: ASTRONOMY
    Type: Icarus (ISSN 0019-1035); 95; 115-147
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  • 3
    Publication Date: 2006-02-14
    Description: Over 20 asteroids were observed photometrically for period determinations and phase relation studies. These included 1036 Ganymed, the largest Mars-crossing asteroid known, and 1627 Ivar, an earth-approaching asteroid which is a potential space mission target. Doppler images of P/Halley from TMO were obtained. Initial testing of the JPL/TMO CCD camera system has supported by imaging P/Giacobini-Zinner and P/Halley.
    Keywords: ASTRONOMY
    Type: NASA, Washington Reports of Planetary Astronomy, 1985; p 94
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  • 4
    Publication Date: 2011-08-19
    Description: The 1036 Ganymed and 1627 Ivar photoelectric lightcurves presently discussed indicate in the former case a drastic lightcurve shape change, in conjunction with a significant increase of the synodic rotation period; a substantial change in viewing conditions during the apparition, and a complex interaction between these changes and the asteroid's irregular shape, are indicated by the change. In the latter asteroid's case, a prograde rotation rate is apparent in the observed decrease in synodic period. Both asteroids' phase curves exhibit deviations from the H-G magnitude system phase function at large phase angles.
    Keywords: ASTRONOMY
    Type: Icarus (ISSN 0019-1035); 78; 363-381
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  • 5
    Publication Date: 2019-06-28
    Description: Photometric observations of the asteroid 37 Fides carried out at four observatories are reported. The data were taken at phase angles ranging from approximately 2-23 deg. A composite of the light curves obtained revealed that, considering a period of 7.33 hr, the full cycle light curve exhibits one maximum and one minimum. An increase in brightness was observed following a primary minimum, a factor that indicated the cyclical appearance and disappearance of a large topographical feature. It is concluded that the 7.33 hr period is the rotational speed of the asteroid, in contrast with a previously held 14.66 hr rotational period. The method is concluded useful for identifying rotational periods of asteroids when only partial light curve data from different sources is available, and when the projections can be checked observationally.
    Keywords: ASTRONOMY
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 123; 2 Ju; July 198
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  • 6
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    In:  Other Sources
    Publication Date: 2019-06-27
    Description: Photoelectric observations of 32 asteroids observed from Table Mountain Observatory during the second half of 1978 are reported. Rotation periods were obtained for most objects. Absolute magnitudes and phase functions were not determined for any of these asteroids. The geometric mean rotation period of the 32 asteroids observed is 14.2 + or - 1.6 hr, as compared to 9.38 + or - 0.35 hr for 182 asteroids analyzed in Harris and Burns (1979). This difference is attributed to an observational selection effect which favors detection of fast rotation. If this is true, then the present sample contains the reverse bias, since it is complete in that a period (in some cases very approximate) was obtained for each object observed, but fast rotators are underrepresented due to prior discovery of their rotation properties.
    Keywords: ASTRONOMY
    Type: Icarus; 43; July 198
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  • 7
    Publication Date: 2019-06-28
    Description: Results of a worldwide photometric investigation of the asteroid 324 Bamberga conducted from September to November 1978 are presented. The full-cycle light curve obtained from observations at Torino, Graz, Catania and Table Mountain observatories shows two maxima and two minima with a maximum amplitude of 0.075 magnitudes from which rotation period of 29.42 plus or minus 0.01 hours is derived. Linear least squares solution of the phase relation results in a phase coefficient of 0.034 plus or minus 0.001 mag/deg, a mean V magnitude of 7.20 and a zero-phase absolute V magnitude of 7.17 plus or minus 0.01. The color indices obtained (0.69 for B-V and 0.36 for U-B) are in agreement with the C taxonomic type assigned to the asteroid. The unusual length of the period of 324 Bamberga relative to that of other asteroids of diameter greater than 200 km is pointed out.
    Keywords: ASTRONOMY
    Type: Icarus; vol 43
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  • 8
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    Unknown
    In:  Other Sources
    Publication Date: 2019-06-28
    Description: The results from the year 1979 of an ongoing program of asteroid photometry at Table Mountain Observatory are presented. The results for 53 asteroids are summarized in a table, showing the number, name, opposition date, taxonomic class, diameter, absolute magnitude, mean absolute magnitude at zero phase angle and values of the absolute magnitude and linear phase coefficient derived from it, the rotation period in hours, peak-to-peak amplitude of variation, difference between mean and maximum brightness, and reliability index. Another table presents data on aspect and comparison stars, including brightness and distance data. Reliable rotation periods are reported for 22 asteroids for which no previous values are known. For seven asteroids, periods are reported which are revisions of previously reported values.
    Keywords: ASTRONOMY
    Type: Icarus (ISSN 0019-1035); 54; April 19
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  • 9
    Publication Date: 2019-06-28
    Description: Photoelectric lightcurves of 304 Olga were obtained at Table Mountain Observatory in 1978 near opposition. From these observations, and several observations made from Lowell Observatory a month later, a rotation period of 18.36 + or - 0.02 hr and a light curve amplitude of 0.20 magnitude are obtained. The range of solar phase angle covered by the observations is from 2.0 to 22 deg. The resulting phase function is well fit by the Bowell and Lumme model (1979), with Q = 0.02. This low value of Q is suggestive of a low-albedo object.
    Keywords: ASTRONOMY
    Type: Icarus; 43; Aug. 198
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  • 10
    Publication Date: 2019-06-28
    Keywords: ASTRONOMY
    Type: Astronomy and Astrophysics; 115; 2; Nov. 198
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