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Due to climate change, extreme high temperature weather is occurred frequently, which may cause a serious decline in crop yield. The growth status of maize seedlings directly affects the formation of later yield. However, there are insufficient understanding and studies on the maize seedling growth and physiological characteristics of leaves under high temperature stress at present. Hence, this experiment was designed to investigate the effects of heat stress on the plant biomass, photosynthetic characteristics, antioxidant enzyme activities and osmotic adjustment substances in the two maize varieties (heat-resistant variety ZD958 and heat-sensitive variety HSV20), with its clear the response mechanism of heat stress to the physiological metabolism changes at seedling stage. The results showed that the plant height increased, while the photosynthetic green leaf area, dry matter accumulation, root surface area and total root length significantly decreased under heat stress. High temperature treatment reduced the Pn, Gs, Tr, Fv/Fm, Fv/F0, qP and SPAD, and increased the Ci and NPQ. As heat stress time increased, the antioxidant enzyme activities first increased and then decreased, while the MDA content continued to increase. Additionally, the free proline content first increased and then decreased. Comparatively, we revealed that ZD958 has stronger antioxidant enzyme activities and osmotic regulation abilities, stable chlorophyll content, higher photosynthetic rate and maximal photochemical efficiency under heat stress, which may be the reasons why the root and shoot growth of seedlings has slighter changes and greater adaptability to heat stress. [ABSTRACT FROM AUTHOR]

Gamma-ray angular distributions in oriented 92 Mo produced via the 6 Li+ 89 Y reaction were studied in this work. The characteristic γ rays in 92 Mo were measured by means of the GALILEO array, which is composed of 25 Compton-suppressed HPGe detectors arranged in a nearly 2 π geometry. A detailed analysis of the spin-alignment attenuation factors ( α 2 ) for different excited states in 92 Mo was performed, by analyzing the measured angular distribution coefficients of several pure-E2 transitions. The relationship between α 2 and the spin was established in 92 Mo and the 244-keV transition between the 5 1 - and 4 1 + states resulted to have a E1 + M2 character with a mixing ratio (δ ) of - 0. 05 - 0.06 + 0.05 , consistent with shell model calculations. [ABSTRACT FROM AUTHOR]

Quasi-elastic scattering angular distribution for the 94.5 MeV 17 F radioactive ion beam on the 208 Pb target has been measured. To describe the experimental quasi-elastic scattering angular distribution and explore the reaction dynamic, firstly, the optical potentials with the double-folding São Paulo and Akyüz Winther potentials for both real and imaginary parts were used to analyze the experimental data. It is observed that both theoretical angular distributions are very similar. The optical model results describe reasonably the experimental data until 100 ∘ but underpredict the data for larger angles. Secondly, the continuum discretized coupled channel method (CDCC) was used to study the effect of the breakup channel on the elastic scattering. The double-folding São Paulo and Akyüz Winther potentials were used as nuclear interactions giving again similar results. The agreement with the data is slightly improved at intermediate angles. The sensibility of the CDCC effects upon the nuclear interaction potential was checked. Finally, the influence of inelastic states of both projectile and target, the one-proton, one-neutron, two-neutron and α transfer channels on the quasi-elastic scattering angular distribution is analyzed in the frame of the coupled channel and coupled reaction channel methods, respectively. It is observed that the coupling to the first excited state of 17 F is the one that affects more the elastic scattering, although the inelastic channels of the target also influence it when compared with the optical model results. The effect of the transfer channels on the quasi-elastic angular distribution is negligible. [ABSTRACT FROM AUTHOR]

Owing to brittleness and hardness, optical glass is one of the materials that is most difficult to cut. Nevertheless, as the threshold value of the undeformed chip thickness is reached, brittle materials undergo a transition from the brittle to the ductile machining region. Below this threshold, it is believed that the energy required to propagate cracks is larger than the energy required for plastic deformation. Thus, plastic deformation is the predominant mechanism of material removal in machining these materials in this mode. An experimental study is conducted to diamond-cut BK7 glass in ductile mode. As an effective rake angle plays a more important role than a nominal rake angle does, a discussion about this effective angle is carried out in the paper. The investigation presents the feasibility of achieving nanometric surfaces. Power spectral density (PSD) analysis on the machined surfaces shows the difference between the characteristics of the two modes. During the experiments, it is recognised that tool wear is a severe problem. Further study is in process to improve the cutting tool life. [ABSTRACT FROM AUTHOR]

According to the hypothesis of ductile machining, brittle materials undergo a transition from brittle to ductile mode once a critical undeformed chip thickness is reached. Below this threshold, the energy required to propagate cracks is believed to be larger than the energy required for plastic deformation, so that plastic deformation is the predominant mechanism of material removal in machining these materials in this mode. An experimental study is conducted using diamond cutting for machining single crystal silicon. Analysis of the machined surfaces under a scanning electron microscope (SEM) and an atomic force microscope (AFM) identifies the brittle region and the ductile region. The study shows that the effect of the cutting edge radius possesses a critical importance in the cutting operation. Experimental results of taper cutting show a substantial difference in surface topography with diamond cutting tools of 0° rake angle and an extreme negative rake angle. Cutting with a diamond cutting tool of 0° rake angle could be in a ductile mode if the undeformed chip thickness is less than a critical value, while a ductile mode cutting using the latter tool could not be found in various undeformed chip thicknesses. [ABSTRACT FROM AUTHOR]