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Rice (Oryza sativaL.) quality depends mainly on the characteristics of starch stored in kernels. Understanding the changes in starch characteristics in kernels during variety improvement would have great significance to improve rice quality. This study was designed to investigate the starch characteristics in the kernels and associated physiological traits of indicarice varieties in the lower reaches of the Yangtze River in China in last 80 years. Eight representative mid-season indicarice varieties were grown in the field. The results showed that the grain yield was significantly increased with the improvement of varieties and such an increase was mainly attributed to the increase in total number of spikelets. The tall varieties applied in the 1940s–1950s had higher protein content, relative crystallinity and infrared (IR) ratio of 1 045/1 022 cm−1. The semi-dwarf varieties applied in the 1980s–1990s had higher gel consistency, amylopectin content, IR ratio of 1 022/995 cm−1, and breakdown value. With the improvement of varieties, the amylose content, large-sized starch granule number and volume distribution, onset and peak of gelatinization temperature, gelatinization and retrogradation enthalpy, setback value, pasting temperature, viscosity of peak, hot and final, and 1-aminocycopropane-1-carboxylic acid (ACC) concentrations in panicles and root bleeding were gradually decreased, whereas the medium-sized starch granule number and volume distribution, activities of key enzymes in grains, and zeatin (Z)+zeatin riboside (ZR) contents in panicles and root bleeding at grain filling stage were gradually increased. Correlation analysis showed that starch thermodynamic characteristics were closely related to starch structure and components, key enzymes and hormones. The results suggest that starch quality was enhanced through the optimization of starch components, structure, thermodynamics, and the regulation of key enzymes in grains and hormones in panicles and root bleedings at grain filling stage during the improvement of mid-season indicarice.

Production of hydrogen peroxide (H2O2) via in situ electrochemical water oxidation possesses great potential applications in the energy and environment fields. In this work, for the first time, we reported a C,N codoped TiO2electrode for selective electrocatalytic water oxidation to produce H2O2in an acidic electrolyte. An electrochemical anodic oxidation method combined with postcalcination in the presence of urea was applied to fabricate such a C,N codoped TiO2electrode, which was evidenced by detail structural characterizations. The calcination temperature and urea atmosphere were found to play key roles in its catalytic performances; the optimized 600N sample exhibited an onset potential of 2.66 V (vs Ag/AgCl) and a Tafel slope of 51 mV dec–1at pH 3. Under the optimal applied potential, the cumulative H2O2concentration for this sample reached 0.29 μmol L–1cm–2h–1. More importantly, a simple recalcination strategy was developed to recover the deactivation electrode. This study proposed an efficient C,N codoped TiO2electrode toward water oxidation to selectively produce H2O2in the acidic electrolyte, which could be further used to in situ generate H2O2for the energy- and environment-related fields with water as the precursor.

For lack of flexible description and the increasing complexity of data input, traditional modeling methods can not meet the demand of fast modeling for complicated bridge structures. Traditional methods are classified into the data based modeling and the graphic based modeling, and their disadvantages are discussed. On this condition, a new modeling method based on design drawings of AutoCAD is presented in this paper, which could fulfill the requirement of fast modeling and reflect the mechanic properties and internal relation of the structures. Especially, it can draw data from the AutoCAD lines automatically for analysis. The efficiency and reliability of the method has been proved by our software system WXQ developed for curved-skew bridges through a practical project.

To study the three-dimensional (3D) magnetic field topology and its long-term evolution associated with the X3.4 flare of 2006 December 13, we investigate the coronal relative magnetic helicity in the flaring active region (AR) NOAA 10930 during the time period of December 8-14. The coronal helicity is calculated based on the 3D nonlinear force-free magnetic fields reconstructed by the weighted optimization method of Wiegelmann, and is compared with the amount of helicity injected through the photospheric surface of the AR. The helicity injection is determined from the magnetic helicity flux density proposed by Pariat et al. using Solar and Heliospheric Observatory/Michelson Doppler Imager magnetograms. The major findings of this study are the following. (1) The time profile of the coronal helicity shows a good correlation with that of the helicity accumulation by injection through the surface. (2) The coronal helicity of the AR is estimated to be -4.3 x 1043 Mx2 just before the X3.4 flare. (3) This flare is preceded not only by a large increase of negative helicity, -3.2 x 1043 Mx2, in the corona over [?]1.5 days but also by noticeable injections of positive helicity through the photospheric surface around the flaring magnetic polarity inversion line during the time period of the channel structure development. We conjecture that the occurrence of the X3.4 flare is involved with the positive helicity injection into an existing system of negative helicity.

A magnetic channel--a series of polarity reversals separating elongated flux threads with opposite polarities--may be a manifestation of a highly non-potential magnetic configuration in active regions. To understand its formation, we have carried out a detailed analysis of the magnetic channel in AR 10930 using data taken by the Solar Optical Telescope/Hinode. As a result, we found upflows (-0.5 to -1.0 km s-1) and downflows (+1.5 to +2.0 km s-1) inside and at both tips of the thread, respectively, and a pair of strong vertical currents of opposite polarity along the channel. Moreover, our analysis of the nonlinear force-free fields constructed from the photospheric magnetic field indicates that the current density in the lower corona may have gradually increased as a result of the continuous emergence of the highly sheared flux along the channel. With these results, we suggest that the magnetic channel originates from the emergence of the twisted flux tube that has formed below the surface before the emergence.

In this study, the photospheric vector magnetograms, obtained with the Spectro-Polarimeter of the Solar Optical Telescope on board Hinode, are used as the boundary conditions to extrapolate the three-dimensional nonlinear force-free (NLFF) coronal magnetic fields. The observed non-force-free photospheric magnetic fields are preprocessed toward the nearly force-free chromospheric magnetic fields. The performance of the preprocessing procedure is evaluated by comparing with chromospheric magnetic fields obtained by the Vector SpectroMagnetograph instrument located on the Synoptic Optical Long-term Investigations of the Sun Tower. Then, the weighted optimization method is applied to the preprocessed boundary data to extrapolate the NLFF fields with which we are able to estimate the free magnetic energy stored in the active regions. The magnitude scaling correlation between the free magnetic energy and the soft X-ray flare index (FI) of active regions is then studied. The latter quantifies the impending flare production of active regions over the subsequent 1, 2, and 3 day time windows. Based on 75 samples, we find a positive correlation between the free energy and the FI. We also study the temporal variation of free magnetic energy for three active regions, of which two are flare-active and one is flare-quiet during the observation over a period of several days. While the magnitude of free magnetic energy unambiguously differentiates between the flare-active and the flare-quiet regions, the temporal variation of free magnetic energy does not exhibit a clear and consistent pre-flare pattern. This may indicate that the trigger mechanism of flares is as important as the energy storage in active regions.

We study the temporal variation of free magnetic energy E free around the time of four X-class flares. The high-cadence photospheric vector magnetograms obtained by the digital vector magnegograph system at the Big Bear Solar Observatory are used as the boundary conditions to reconstruct the three-dimensional nonlinear force-free (NLFF) coronal field. In order to remove the effect of the net Lorentz force and torque acting in the photosphere, the vector magnetograms are preprocessed using the method devised by Wiegelmann et al.. Then a well-tested multigrid-like optimization code by Wiegelmann is applied to the preprocessed boundary data to extrapolate the NLFF coronal field with which we are able to estimate the free energy E free. In all the four events, we find a significant drop of E free starting [?]15 minutes before the peak time of the associated nonthermal flare emission, although long-term trend varies from event to event. We discuss the physical implication of the result, i.e., the magnetic relaxation is already going on in the corona well before the flare reconnection.

The concept of "magnetic channel" was first introduced by Zirin & Wang. They were defined as a series of oppositely directed vertical-field inversions separated by extremely narrow elongated transverse fields. In this paper, we utilized unprecedented filtergraph and spectropolarimetry observations from Hinode, and studied the evolution and physical properties of channel structure of AR 10930 in detail. We found the following: (1) Channels are associated with new flux emergence in the middle of existing penumbra connecting the d sunspot. (2) The width of each channel is in the order of 1'' or less. (3) The line-of-sight magnetic gradient is highest in the channel, 2.4-4.9 G km[?]1. (4) The fields are highly sheared and inclined with a median shear angle around 64deg and inclination angle around 25deg. (5) Using nonlinear force-free field (NLFF) extrapolation, we derive a near surface current system carrying electric current in the order of 5 x 1011 A. (6) The X3.4 flare on 2006 December 13 occurred during the period that the channels rapidly formed, but a few hours before the maximum phase of channel structure development. Based on the observational evidence, we propose that the channels are formed during the emergence of a sequence of magnetic bipoles that are squeezed in the compact penumbra of the d sunspot and they are highly nonpotential. Formation of channels might be a precursor of major flares.

We have investigated the variation of magnetic helicity over a span of several days around the times of 11 X-class flares which occurred in seven active regions (NOAA 9672, 10030, 10314, 10486, 10564, 10696, and 10720) using the magnetograms taken by the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory (SOHO). As a major result we found that each of these major flares was preceded by a significant helicity accumulation, ( 1.8-16) x 1042 Mx2 over a long period (0.5 to a few days). Another finding is that the helicity accumulates at a nearly constant rate, (4.5-48) x 1040 Mx2 hr[?]1, and then becomes nearly constant before the flares. This led us to distinguish the helicity variation into two phases: a phase of monotonically increasing helicity and the following phase of relatively constant helicity. As expected, the amount of helicity accumulated shows a modest correlation with time-integrated soft X-ray flux during flares. However, the average helicity change rate in the first phase shows even stronger correlation with the time-integrated soft X-ray flux. We discuss the physical implications of this result and the possibility that this characteristic helicity variation pattern can be used as an early warning sign for solar eruptions.

We report a detailed analysis of successive flaring during the X1.5 event in the NOAA AR 0808 on 2005 September 13. We identify a filament lying at the southeast boundary of the active region as the physical linkage between the two flares in close succession. It is noticeable that the filament erupted ~13 minutes after the initial flare onset at ~19 : 22 UT near the central magnetic polarity inversion line (PIL). During this time period, the filament only showed a slow rising; meanwhile, a spatially associated large magnetic loop with one leg connecting to the initial flaring site began to brighten in the TRACE 195 A channel. After ~19 : 35 UT, the filament abruptly erupted together with the bright TRACE loop. Besides the moving ribbons at the first flaring site, the filament eruption caused a secondary flare identified with another set of moving ribbons. This event thus provides a clear evidence for the successive flaring where the initial flare destabilizes the nearby flux loop system, leading to the filament eruption with the second flare. We also identify the initial flare core by finding rapid, irreversible enhancements of the photospheric transverse magnetic fields at a section of the PIL.

Using observations of more than 160 active regions, we investigate the relationship between the coronal X-ray brightness, LB, and five parameters derived from the photospheric magnetic fields. The coronal X-ray brightness and the magnetic measures were obtained from co-aligned SFD composite images from the Yohkoh SXT and full-disk magnetograms from the SOHO MDI, respectively. The magnetic parameters are (1) the length of strong-gradient magnetic neutral lines, GNL, (2) the magnetic energy dissipation, [?], (3) the unsigned line-of-sight magnetic flux, Ph, (4) the horizontal velocities, Vh, of random footpoint motions in the photosphere, and (5) a proxy for the Poynting flux, E = (1/4p) img1.gif img2.gif2, which characterizes the energy flux from the photosphere into the corona due to random footpoint motions. All measures except Vh were analyzed in both the extensive (total) and intensive (average over an area) forms. In addition, we used the area-averaged strong gradient (>50 G) of the magnetic field, [?]Bz, as an intensive form of GNL. We found that the Pearson correlation coefficient between the total X-ray brightness and the total magnetic measures decreases as 0.97, 0.88, 0.86, and 0.47 for Ph, E, [?], and GNL, respectively. The correlation coefficient between the averaged X-ray brightness and the averaged magnetic measures varied as 0.67, 0.71, 0.57, and 0.49 for img3.gif, img4.gif, img5.gif, and img6.gif, respectively. We also found that the velocities of the footpoint motions have no dependencies with Ph and LB. We concluded that the observed high correlation between LB and E is mainly due to the magnetic field. The energy of the Poynting flux is in the range 106.7-107.6 ergs cm-2 s-1 for the majority of active regions, which is sufficient to heat the corona due to footpoint random motions of magnetic flux tubes.

The Infrared Imaging Magnetograph (IRIM) system developed by Big Bear Solar Observatory (BBSO) has been put into preliminary operation. It is one of the first imaging spectropolarimeters working at 1565 nm and is used for the observations of the Sun at its opacity minimum, exposing the deepest photospheric layers. The tandem system, which includes a 4.2 nm interference filter, a unique 0.25 nm birefringent Lyot filter, and a Fabry-Pérot etalon, is capable of providing a bandpass as low as 0.01 nm in a telecentric configuration. A fixed quarter-wave plate and a nematic liquid crystal variable retarder are employed for analyzing the circular polarization of the Zeeman components. The longitudinal magnetic field is measured for the highly Zeeman-sensitive Fe iline at 1564.85 nm (Landé factor g= 3). The polarimetric data were taken through a field of view of ?145''× 145''and were recorded by a 1024 × 1024 pixel, 14 bit HgCdTe CMOS focal plane array camera. Benefiting from the correlation tracking system and a newly developed adaptive optics system, the first imaging polarimetric observations at 1565 nm were made at the diffraction limit on 2005 July 1 using BBSO's 65 cm telescope. After comparing the magnetograms from IRIM with those taken by the Michelson Doppler Imager on board SOHO, it was found that all the magnetic features matched very well in both sets of magnetograms. In addition, Stokes Vprofiles obtained from the Fabry-Pérot etalon scan data provide access to both the true magnetic field strength and the filling factor of the small-scale magnetic flux elements. In this paper, we present the design, fabrication, and calibration of IRIM, as well as the results of the first scientific observations.

We observed two X-class white-light flares (WLFs) on 2003 October 29 (~20:40 UT) and November 2 (~17:16 UT) using the Dunn Solar Telescope (DST) and its High-Order Adaptive Optics (HOAO) system in several wavelengths. The spatial resolution was close to the diffraction limit of DST's 76 cm aperture, and the cadence was as high as 2 s. This is the first time that WLFs have been observed in the near-infrared (NIR) wavelength region. We present a detailed study in this paper comparing photospheric continuum observations during the two events with corresponding line-of-sight magnetograms from the Solar and Heliospheric Observatory (SOHO) Michelson Doppler Imager (MDI) and hard X-ray (HXR) data from the Ramaty High-Energy Solar Spectroscopic Imager (RHESSI). We also discuss several models that provide possible mechanisms to explain these continuum enhancements, especially in the NIR.

Forbes & Lin derived simple equations to link the properties of magnetic reconnection in the corona to observed signatures of solar flares. We measured the photospheric magnetic fields and the flare ribbon separation speeds then applied these equations to derive two physical terms for the magnetic reconnection rates: the rate of magnetic flux change phrec involved in magnetic reconnection in the low corona and the electric field Erec inside the reconnecting current sheet (RCS) that is generated during magnetic reconnection. The central interest in this work is to investigate and quantify the statistical correlation between the magnetic reconnection rate and the corresponding flux-rope acceleration. From a sample of 13 well-observed two-ribbon flares, which are associated with filament eruptions or coronal mass ejections (CMEs), the acceleration of erupting filaments is found mainly in the range of 0.05-0.4 km s-2, up to 3 km s-2. Correspondingly, the maximum Erec and phrec mostly occur in the range of 0.2-5 V cm-1 and 0.5-6 x 1018 Mx s-1, respectively. A positive and strong correlation is found with a cross-correlation coefficient of 0.94-0.97 between the magnetic reconnection rate and the acceleration of erupting filaments that represents the early stages of flux-rope eruptions in the low corona. However, the inferred reconnection rate is not correlated to the acceleration of CME fronts measured by the Large Angle and Spectrometric Coronagraph (LASCO) observations in the range of 2-30 solar radii (the correlation coefficient is less than 0.2). A reasonable correlation is found between the reconnection rate and the velocity of CMEs, which indicates the cumulative acceleration of CMEs from the low corona to the LASCO C2 field of view. The temporal correlation between the magnetic reconnection rate and the flare nonthermal emissions has also been verified in this paper.

We present a statistical study of 106 filament eruptions, which were automatically detected by a pattern recognition program implemented at Big Bear Solar Observatory using Ha full-disk data from 1999 to 2003. We compare these events with Geostationary Operational Environmental Satellite soft X-ray time profiles, solar-geophysical data (SGD) solar event reports, Michelson Doppler Imager magnetograms, and Large Angle and Spectrometric Coronagraph (LASCO) data to determine the relationship between filament eruptions and other phenomena of solar activity. (1) Excluding eight events with no corresponding LASCO data, 55% or 56% of 98 events were associated with coronal mass ejections (CMEs). (2) Active region filament eruptions have a considerably higher flare association rate of 95% compared to quiescent filament eruptions with 27%, but a comparable CME association rate, namely, 43% for active region filament eruptions and 54% for quiescent filament eruptions. (3) 54% or 68% of 80 disk events were associated with new flux emergence. In addition, we derived the sign of magnetic helicity and the orientation of the magnetic field associated with seven halo CMEs and demonstrated that the geoeffectiveness of a halo CME can be predicted by these two parameters.

In this paper, we present a detailed study of the M8.7 flare that occurred on 2002 July 26 using data from the Big Bear Solar Observatory (BBSO), Ramaty High Energy Solar Spectroscopic Imager (RHESSI), the Transition Region and Coronal Explorer (TRACE), and the Solar and Heliospheric Observatory (SOHO). This flare has interesting properties similar to a number of flares that we studied previously, such as a rapid increase of magnetic flux in one polarity and an increase in transverse fields and magnetic shear associated with the flare. However, this event had the most comprehensive observations; in particular, the high-resolution high-cadence BBSO vector magnetograph observations. At the time of the flare, across the flare neutral line, there was a sudden emergence of magnetic flux at the rate of 1020 Mx hr-1 in both the longitudinal and transverse components. The emerging flux mostly occurred at the sites of the flare. It was very inclined and led to impulsively enhanced shear in the magnetic fields. We discuss these observations in the context of magnetic reconnection triggered by rapid flux emergence. It is also possible that the new flux signifies flare-related change in the field line inclination.

In this paper, we present a detailed study of a two-ribbon flare in the plage region observed by Kanzelhohe Solar Observatory (KSO), which is one of the stations in our global Ha network. We select this event due to its very clear filament eruption, two-ribbon separation, and association with a fast coronal mass ejection (CME). We study the separation between the two ribbons seen in Ha as a function of time and find that the separation motion consisted of a fast stage of rapid motion at a speed of about 15 km s-1 in the first 20 minutes and a slow stage with a separation speed of about 1 km s-1 lasting for 2 hr. We then estimate the rate of the magnetic reconnection in the corona, as represented by the electric fields Ec in the reconnecting current sheet, by measuring the ribbon motion speed and the magnetic fields obtained from MDI. We find that there were two stages as well in evolution of the electric fields: Ec = 1 V cm-1 averaged over 20 minutes in the early stage, followed by Ec = 0.1 V cm-1 in the subsequent 2 hr. The two stages of the ribbon motion and electric fields coincide with the impulsive and decaying phases of the flare, respectively, yielding clear evidence that the impulsive flare energy release is governed by the fast magnetic reconnection in the corona. We also measure the projected heights of the erupting filament from KSO Ha and SOHO/EIT images. The filament started to rise 20 minutes before the flare. After the flare onset, it was accelerated quickly at a rate of 300 m s-2, and in 20 minutes, reached a speed of at least 540 km s-1, when it disappeared beyond the limb in the EIT observations. The acceleration rate of the CME is estimated to be 58 m s-2 during the decay phase of the flare. The comparison of the height and velocity profiles between the filament and CME suggests that fast acceleration of mass ejections occurred during the impulsive phase of the flare, when the magnetic reconnection rate was also large, with Ec = 1 V cm-1.

Depending on the textural distribution of easy axes of the particles there could exhibit one, two or three prominent cusps in the curves for the reversible transverse susceptibility at high KV/kBT. Experimentally, the number of cusps detected at low KV/kBTmay be one less since the cusp at Hcis fairly sensitive to thermal relaxation.