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  • 1
    Language: English
    In: The journal of physical chemistry. B, 05 July 2012, Vol.116(26), pp.7739-45
    Description: We investigated structures of 12-hydroxystearic acid (12-HSA) gels in a wide temperature range from the gel to the sol states and the gelation process by means of small-angle neutron scattering (SANS) and time-resolved synchrotron small-angle X-ray scattering (SAXS), respectively. The SANS result shows that the size of the cross section of the crystalline fibers in the gel was not affected much by temperature change, although the density of the fibers decreased with the increase of temperature even in the gel state. The SANS profiles at various temperatures and compositions were well reduced by the product of the volume fraction of the fiber and the square of the scattering contrast. At temperatures above the melting point of the gels obtained from differential scanning calorimeter, the gel turned into a homogeneous solution. The time-resolved small-angle X-ray scattering experiments revealed the gelation process as mentioned below. At the early stage, the scattering behavior did not show any change (induction period). The induction period was longer at higher temperatures. In the second stage, an amorphous precursor appeared as an initial structure of crystalline nucleus. In the next stage, the fiber was developed via crystalline nucleation and growth. In this stage, the fibers grew with keeping the size of the cross section (the radius of gyration R ≅ 82 -84 Å) constant, and finally, the fiber growth was arrested because of gelation.
    Keywords: Crystal Growth -- Research ; Gelation -- Analysis ; Gellants -- Thermal Properties ; Gellants -- Structure ; Nucleation (Physics) -- Analysis ; Phase Transition Temperatures -- Measurement;
    ISSN: 15206106
    E-ISSN: 1520-5207
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  • 2
    Language: English
    In: Microwave Journal, May, 2011, Vol.54(5), p.222(4)
    Description: Issues regarding the accurate measurement of pulsed active devices are discussed. These can be addressed through receiver leveling and leveling of pulsed stimulus power.
    Keywords: Microwave Equipment -- Testing ; Electric Circuit Analysis -- Research
    ISSN: 0192-6225
    Source: Cengage Learning, Inc.
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  • 3
    In: Nature, 2012, Vol.485(7399), p.478
    Description: Solar flares are caused by the sudden release of magnetic energy stored near sunspots. They release 10 (29) to 10 (32) ergs of energy on a timescale of hours (1). Similar flares have been observed on many stars, with larger 'superflares' seen on a variety of stars (2,3), some of which are rapidly rotating (4,5) and some of which are of ordinary solar type (3,6). The small number of superflares observed on solar-type stars has hitherto precluded a detailed study of them. Here we report observations of 365 superflares, including some from slowly rotating solar-type stars, from about 83,000 stars observed over 120 days. Quasi-periodic brightness modulations observed in the solar-type stars suggest that they have much larger starspots than does the Sun. The maximum energy of the flare is not correlated with the stellar rotation period, but the data suggest that superflares occur more frequently on rapidly rotating stars. It has been proposed that hot Jupiters may be important in the generation of superflares on solar-type stars (7), but none have been discovered around the stars that we have studied, indicating that hot Jupiters associated with superflares are rare.
    Keywords: Solar Flares – Natural History ; Stars – Natural History ; Astrophysics – Research;
    ISSN: 0028-0836
    E-ISSN: 14764687
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  • 4
    In: Proceedings of the International Astronomical Union, 2016, Vol.12(S328), pp.22-29
    Description: Abstract Recent high-precision photometry from space (e.g., Kepler) enables us to investigate the nature of “superflares” on solar-type stars. The bolometric energy of superflares detected by Kepler ranges from 10 33 erg to 10 36 erg which is 10-10,000 times larger than that released by a typical X10 class solar flare. The occurrence frequency ( dN / dE ) of superflares as a function of flare energy ( E ) shows the power-law distribution with the power-law index of ~−1.8 for 10 34 〈 E 〈 10 36 erg. Most of superflare stars show quasi-periodic light variations which suggest the presence of large starspots. The bolometric energy released by flares is consistent with the magnetic energy stored near the starspots. The occurrence frequency of superflares increases as the rotation period decreases. However, the energy of the largest flares observed in a given period bin does not show any clear correlation with the rotation period. These results suggest that superflares would occur on the slowly-rotating stars.
    Keywords: Contributed Papers; Stars:Activity; Stars:Flare; Stars:Solar-Type
    ISSN: 1743-9213
    E-ISSN: 1743-9221
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  • 5
    In: Nature, 2003, Vol.423(6942), p.843
    Description: Gamma-ray bursts (GRBs) are energetic explosions that for 0.01--100 s are the brightest gamma-ray sources in the sky. Observations of the early evolution of afterglows we expected to provide clues about the nature of the bursts, but their rapid fading has hampered such studies; some recent rapid localizations of bursts have improved the situation. Here we report on an early detection of the very bright afterglow of the burst of 29 March 2003 (GRB030329). Our data show that, even early in the aferglow phase, the light curve shows unexpectedly complicated structures superimposed on the fading background. Comment: 8 pages, 1 figure, To appear in Nature June 19 issue. For the access to the data in the paper, see http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/GRB/grb030329/GRB030329_information .html
    Keywords: Astrophysics;
    ISSN: 0028-0836
    E-ISSN: 1476-4687
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  • 6
    In: Publications of the Astronomical Society of Japan, 2013, Vol. 65(4)
    Description: We analyzed a Kepler light curve of KIC 8751494, a recently recognized novalike cataclysmic variable in the Kepler field. We detected a stable periodicity of 0.114379(1) d, which we identified as being the binary’s orbital period. The stronger photometric period at around 0.12245 d, which had been detected from a ground-based observation, was found to be variable, and we identified this period as the positive-superhump period. This superhump period showed short-term (10–20 d) strong variations in period most unexpectedly when the object entered a slightly faint state. The fractional superhump excess varied by as much large as $\sim$ 30%. The variation of the period very well traced the variation of the brightness of the system. The time-scale of this variation of superhump periods was too slow to be interpreted as a variation caused by a change of the disk radius due to thermal disk instability. We interpreted the cause of the period variation as a varying pressure effect on the period of positive superhumps. This finding suggests that the pressure effect, in at least novalike systems, plays a very important (up to $\sim$ 30% in the precession rate) role in producing the period of positive superhumps. We also described a possible detection of negative superhumps with a varying period of 0.1071–0.1081 d in the Q14 run of the Kepler data, and found that the variation of frequency of negative superhumps followed that of positive superhumps. The relation between the fractional superhump excesses of negative and positive superhumps can be understood if the angular frequency of positive superhumps is decreased by a pressure effect. We also found that the phase of the variation in the velocity of the emission lines reported in the earlier study is compatible with the SW Sex-type classification. Further, we introduced a new two-dimentional period analysis using least absolute shrinkage and selection operator (Lasso), and showed superior advantages of this method.
    Keywords: Accretion, Accretion Disks ; Stars: Dwarf Novae ; Stars: Individual (Kic 8751494) ; Novae, Cataclysmic Variables
    ISSN: 0004-6264
    E-ISSN: 2053-051X
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  • 7
    Language: English
    In: Surgery Today, 2011, Vol.41(7), pp.1003-1006
    Description: This report describes three cases of a delayed closure to prevent the occurrence of abdominal compartment syndrome (ACS) in patients presenting with ruptured abdominal aortic aneurysms (rAAA). The delayed closure technique is useful for rAAA in order to prevent ACS.
    Keywords: Delayed closure ; Abdominal compartment syndrome
    ISSN: 0941-1291
    E-ISSN: 1436-2813
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  • 8
    Description: We analyzed a Kepler light curve of KIC 8751494, a recently recognized novalike cataclysmic variable in the Kepler field. We detected a stable periodicity of 0.114379(1) d, which we identified as being the binary's orbital period. The stronger photometric period around 0.12245 d, which had been detected from the ground-based observation, was found to be variable, and we identified this period as being the positive superhump period. This superhump period showed short-term (10-20 d) and strong variations in period most unexpectedly when the object entered a slightly faint state. The fractional superhump excess varied as large as ~30%. The variation of the period very well traced the variation of the brightness of the system. The time-scales of this variation of the superhump period was too slow to be interpreted as the variation caused by the change in the disk radius due to the thermal disk instability. We interpreted that the period variation was caused by the varying pressure effect on the period of positive superhumps. This finding suggests that the pressure effect, in at least novalike systems, plays a very important (up to ~30% in the precession rate) role in producing the period of the positive superhumps. We also described a possible detection of the negative superhumps with a varying period of 0.1071-0.1081 d in the Q14 run of the Kepler data. We also found that the phase of the velocity variation of the emission lines reported in the earlier study is compatible with the SW Sex-type classification. Further, we introduced a new two-dimentional period analysis using least absolute shrinkage and selection operator (Lasso) and showed superior advantage of this method. Comment: 10 pages, 8 figures, accepted for publication in PASJ, minor correcrtions
    Keywords: Astrophysics - Solar And Stellar Astrophysics
    Source: Cornell University
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  • 9
    In: Proceedings of the International Astronomical Union, 2012, Vol.8(S293), pp.393-395
    Description: Abstract We present the results of an extensive survey of superflares on late-type stars (G, K, and M-type main sequence stars) using the Kepler satellite data. Wefound about 6,800 superflares on late-type stars from the data of about 120,000 stars observed over 500 days. The total bolometric energy of superflares in oursample ranges from 10 32 erg to 10 36 erg. Our data suggest that the occurrencefrequency of superflares depends on the surface temperature and the rotationperiod of stars. Superflares on M-type stars occur about 10-100 times morefrequently than those on G-type stars. Our results suggest that the average frequency ofsuperflares releasing 10 34 –10 35 erg of energy (100-1,000 times larger than the largestsolar flares) on M-type stars and Sun-like stars is once in 10 years and once in a few thousand years respectively.
    Keywords: Contributed Papers; Stars: Flare; Stars: Late-Type
    ISBN: 9781107033825
    ISSN: 1743-9213
    E-ISSN: 1743-9221
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  • 10
    In: Publications of the Astronomical Society of Japan, 2012, Vol. 64(3)
    Description: We have developed a method for estimating the orbital periods of dwarf novae from the Sloan Digital Sky Survey (SDSS) colors in quiescence using an artificial neural network. For typical objects below the period gap with sufficient photometric accuracy, we were able to estimate the orbital periods with accuracy to a 1 $\sigma$ error of 22%. The error of the estimation is worse for systems with longer orbital periods. We have also developed a neural-network-based method for categorical classification. This method has proven to be efficient in classifying objects into three categories (WZ Sge type, SU UMa type, and SS Cyg/Z Cam type), and works for very faint objects to a limit of g $=$ 21 mag. Using this method, we have investigated the distribution of the orbital periods of dwarf novae from a modern transient survey (Catalina Real-Time Survey). Using a Bayesian analysis developed by Uemura et al. (2010 , PASJ, 62, 613), we have found that the present sample tends to give a flatter distribution to the shortest period and a shorter estimate of the period minimum, which may have resulted from uncertainties in the neural-network analysis and photometric errors. We also provide estimated orbital periods, estimated classifications, and supplemental information on known dwarf novae with the quiescent SDSS photometry.
    Keywords: Methods: Statistical ; Stars: Dwarf Novae ; Stars: Evolution ; Novae, Cataclysmic Variables ; Surveys
    ISSN: 0004-6264
    E-ISSN: 2053-051X
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