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Water deficit inhibits maize (Zea mays L.) seedling growth and yield. Application of exogenous melatonin can improve drought tolerance of corn, but little is known regarding the transcriptional mechanisms of melatonin-mediated drought tolerance in maize. Increased understanding of the effects of melatonin on maize plants under drought stress is vital to alleviate the adverse effects of drought on food production in the future. The aim of this investigation was to use physiological and transcriptome analyses for exploring the possible mechanisms of exogenous melatonin against drought stress in maize. In this study, maize seedlings were subjected to drought stress and some were treated with exogenous melatonin. The physiological results showed that melatonin inhibited H2O2 accumulation and promoted the scavenging of excessive reactive oxygen species to reduce oxidative damage in maize leaves. Transcriptomic analysis identified 957 differentially expressed genes between melatonin and non-melatonin treatment groups. Further detailed analyses suggested that melatonin-regulated genes are mainly related to glutathione metabolism, calcium signaling transduction, and jasmonic acid biosynthesis. Some transcription factor families, such as WRKY, AP2/ERF-ERF, MYB, NAC, and bZIP, were also activated by exogenous melatonin. Moreover, crosstalk between melatonin and other hormones that mediate drought tolerance was observed. In conclusion, the combination of physiological and transcriptome analyses revealed some mechanisms underlying the role of melatonin in alleviating drought; knowledge of these mechanisms may assist in successful maize cultivation under drought stress.

AIM To investigate the value of computed tomography (CT) texture analysis (TA) and imaging features for evaluating suspected surgical superior mesenteric–portal vein (SMPV) invasion in patients with pancreatic ductal adenocarcinoma (PDAC). MATERIALS AND METHODS Fifty-four patients with PDAC in the pancreatic head or uncinate process with suspected SMPV involvement were analysed retrospectively. SMPV invasion status was identified by surgical exploration. For each patient, 396 texture features were extracted on pretreatment CT. Non-parametric tests and minimum redundancy maximum relevance were used for feature selection. A CTTA model was constructed using multivariate logistic regression, and the area under the receiver operating characteristic (AUROC) of the model was calculated. Two reviewers evaluated qualitative imaging features independently for SMPV invasion and interobserver agreement was investigated. The diagnostic performance of the imaging features and the CTTA model for SMPV invasion was compared using the McNemar test. RESULTS Of the 54 patients with PDAC, SMPV invasion was detected in 23 (42.6%). The CTTA model yielded an AUROC of 0.88 (95% confidence interval, 0.76–0.97) and achieved significantly higher specificity (0.90) than the two reviewers (0.61 and 0.65; p=0.027 and 0.043). Interobserver agreement was moderate between the two reviewers (κ = 0.517). Of the 13 cases with disagreement between the two reviewers, 11 cases were predicted accurately by the CTTA model. CONCLUSION CTTA can predict suspected SMPV invasion in PDAC and may be a beneficial addition for qualitative imaging evaluation.

The ‘westerlies-dominated climatic regime’ (WDCR) in the present interglacial period was proposed because precipitation/moisture variations between arid central Asia and mid-latitude monsoonal Asia are out-of-phase or anti-phased on different timescales during the Holocene. In this study. we first review the development of the theoretical framework of the WDCR, and then outline the boundary of its core area: from the Caspian Sea in the west to the western Hexi Corridor in the east, with the northern and southern limits coinciding with the domain of arid central Asia. Next, we present a synthesis of multiple lines of evidence for the occurrence of the WDCR on multi-millennial (‘sub-orbital’ herein) to decadal timescales during the Holocene. Finally, we examine the possible physical mechanisms responsible for the WDCR. We find that external factors (insolation changes induced by orbital factors) generated the WDCR on a sub-orbital timescale, whereas a circum-global teleconnection/Silk Road pattern was the most significant factor responsible for the WDCR on centennial and decadal timescales. The study provides a comprehensive summary of the development of our knowledge of the WDCR over the past several decades, together with a tentative theoretical framework for understanding climatic and environmental changes within its region of influence. In addition, it forms a scientific basis for environmental management and ecological restoration in this arid region in the context of global warming.

Tibetan Plateau vortices (TPVs), generated over the Tibetan Plateau, are important rainfall triggers in southwestern and eastern China when moving off the plateau. The heavy rainfall event that occurred over southwestern China in early July 2018 caused severe floods and landslides, leading to substantial damage to normal production and life. In this work, the roles of TPVs in the rainfall are investigated based on NCEP FNL (final) operational global analysis and forecast data from the Global Data Assimilation System (GDAS). The results show that TPVs over the eastern Tibetan Plateau favor ascending motion to the east of the plateau, which is conducive to precipitation and therefore the genesis of southwest vortices (SWVs). Generally, the ascending motion in southwestern China is stronger when TPVs exist, compared with the other scenarios in which the TPVs are absent. Ascending motion is always observed on the east side of TPVs, which is greatly attributed to the positive vertical vorticity and warm centers in the TPVs. In this fashion, the influence of TPVs is not merely limited around their centers, but further eastward. Therefore, the effects of TPVs may have been underestimated in previous investigations; the TPVs located over the eastern Tibetan Plateau that do not move off the plateau should also be seriously considered in future precipitation predictions.

High amylose maize flour (HAMF), normal maize flour (NMF), extruded normal maize flour (ENMF) and extruded high amylose maize flour (EHAMF) were employed to analyze the effects of the extrusion process on their physicochemical properties and in vitro digestion. The disruption degree of NMF and HAMF under extrusion followed the degree of gelatinization order. HAMF and EHAMF had higher onset temperature, peak temperature and conclusion temperature but lower melting enthalpies in comparison with NMF and ENMF. Extrusion treatment decreased viscosity and transformed A-type and B-type starch in NMF and HAMF into B + V-type. The solubility of all samples and swelling power of NMF and HAMF showed an increase, while swelling power of extruded maize flour decreased with increasing temperature. HAMF and EHAMF had a higher content of resistant starch but a lower content of slowly digestible starch and rapidly digestible starch than NMF and ENMF.

In this study the interdecadal variations of haze pollution during recent 34 years from 1980 to 2013 over eastern China are investigated. It is found that opposite interdecadal variations of wintertime haze days (WHDs) between the North China Plain region (NCP) and the Yangtze River Delta region (YRD) occurred in this period, i.e., a decreased interdecadal trend of anomalous WHDs appeared in NCP and an increased trend in YRD. Meteorological factors driven the opposite interdecadal variations of anomalous WHDs are revealed. In the phase of interdecadal variations with more WHDs in NCP and less in YRD before 1996, there were weaker northerly winds in the lower troposphere over eastern China accompanied with a weakened Siberia High and mid-latitude westerly jet. The decreased northerly winds are conductive to the local accumulation of air pollutants in NCP and inhibition of air pollutants to be transported from North China to YRD. Consequently, more WHDs appeared in YRD and less in NCP. On the contrary, in the phase of interdecadal variations with less WHDs in NCP and more in YRD after 1996, stronger northerly winds associated with strengthened Siberia High and westerly jet, appeared over eastern China. The increased northerly winds are favorable for the dispersion of air pollutants in NCP and transport more pollutants from North China to the downstream area in YRD, resulting in less WHDs in NCP and more in YRD.

In the last half century, a significant warming trend occurred in summer over eastern China in the East Asian monsoon region. However, there were no consistent trends with respect to the intensity of the East Asian summer monsoon (EASM) or the amount of summer rainfall averaged over eastern China. Both of the EASM and summer rainfall exhibited clear decadal variations. Obvious decadal shifts of EASM occurred around the mid- and late 1970s, the late 1980s and the early 1990s, and the late 1990s and early 2000s, respectively. Summer rainfall over eastern China exhibited a change in spatial distribution in the decadal timescale, in response to the decadal shifts of EASM. From the mid- and late 1970s to the late 1980s and the early 1990s, there was a meridional tri-polar rainfall distribution anomaly with more rainfall over the Yangtze River valley and less rainfall in North and South China; but in the period from the early 1990s to the late 1990s and the early 2000s the tri-polar distribution changed to a dipolar one, with more rainfall appearing over southern China south to the Yangtze River valley and less rainfall in North China. However, from the early 2000s to the late 2000s, the Yangtze River valley received less rainfall. The decadal changes in EASM and summer rainfall over eastern China in the last half century are closely related to natural internal forcing factors such as Eurasian snow cover, Arctic sea ice, sea surface temperatures in tropical Pacific and Indian Ocean, ocean–atmospheric coupled systems of the Pacific Decadal Oscillation (PDO) and Asian–Pacific Oscillation (APO), and uneven thermal forcing over the Asian continent. Up to now, the roles of anthropogenic factors, such as greenhouse gases, aerosols, and land usage/cover changes, on existing decadal variations of EASM and summer rainfall in this region remain uncertain.

The role of the intraseasonal oscillation (ISO) on the seasonal and interannual variations of the Indian summer monsoon is investigated based on the analysis of observational data. It is shown that the ISO significantly contributes to the establishment of low-level westerlies during the monsoon onset and developing periods. The effect of the ISO on the annual cycle of the monsoon is through nonlinear eddy momentum transport. On the interannual timescale, the Indian summer monsoon rainfall exhibits a significant out-of-phase relationship with the ISO intensity over the Indian monsoon region. In strong ISO years it appears the weak monsoon when there is an abnormal high over the India subcontinent in the lower troposphere. In weak ISO years there exists an abnormal low and the strong monsoon appears.

Numerical weather prediction (NWP) has become one of the most important means for weather forecasts in the world. It also mirrors a nation’s comprehensive strength in meteorology. In 2000, China Meteorological Administration (CMA) established the National Innovative Base for Meteorological Numerical Prediction in the Chinese Academy of Meteorological Sciences (CAMS), to work on developing a new generation of the national operational NWP system—Global/Regional Assimilation and PrEdiction System (GRAPES), to enhance meteorological services in China in the new century. In recent years, the GRAPES has witnessed a fast development. The GRAPES has been set up as an integration of the model framework, data assimilation, regional and global NWP system, which can be commonly used for both operation and research. In this paper, a brief review is made for illustrating the GRAPES system, including the advanced designs of the GRAPES, its diverse applications in multi-fields, and efficiencies of the regional and global GRAPES in operational applications based on hindcast results.

A dipole structure anomaly in summer Arctic atmospheric variability is identified in this study, which is characterized by the second mode of empirical orthogonal function (EOF) analysis of summer monthly mean sea level pressure (SLP) north of 70°N, accounting for 12.94% of the variance. The dipole anomaly shows a quasi-barotropic structure with opposite anomalous centers over the Canadian Arctic and the Beaufort Sea and between the Kara Sea and the Laptev Sea. The dipole anomaly reflects alternating variations in location of the polar vortex between the western and eastern Arctic regions. The positive phase of the dipole anomaly corresponds to the center of the polar vortex over the western Arctic, leading to an increase in summer mean rainfall in Northeast China. The dipole anomaly has a predominant 6-year periodicity, and shows interdecadal variations in recent decades.

In the summer of 1991, sound propagation and reverberation experiments were carried out in the Yellow Sea. Explosive sound sources and omnidirectional hydrophones were used. The sound speed profile consisted of a warmer surface isovelocity layer, a strong thermocline and a cooler isovelocity bottom layer. When both the source and the receiver were located above the thermocline, the transmission loss along a certain course and the non-directional average reverberation intensity showed similar frequency-selective attenuation at around 1300 Hz. On the basis of experimental results and some circumstantial evidence, the authors believe that the observed frequency-selective attenuation is due to swimbladder-bearing fish (probably, anchovies) living only above the thermocline.

In this paper, reverberation loss is considered as a basic physical quantity to describe shallow water reverberation, and reverberation loss versus time was calculated by using three models: the ray-based model, the WKBZ mode models with account taken and not taken of the effects of complex eigenvalues. Numerical simulations show that the effects of complex eigenvalues cannot be neglected, and at medium ranges the reverberation loss from the ray-based model is consistent with that from the WKBZ mode model with the effects of complex eigenvalues taken into account. The experimental results shows that reverberation loss is not dependent on the bandwidth. Reverberation in shallow swater with a thermocline shows strong depth dependence, and the theoretical geometric mean rule of reverberation intensity was demonstrated by experiment.

By use of the WKBZ approximation of eigenfunctions with the surface phase-shift correction, and taking account of both the waveguide and bottom-reflection modes, a WKBZ adiabatic mode approach suitable for gradually range-dependent channels is proposed. The numerical simulations show that the acoustic fields in the convergence zones are mainly determined by the waveguide modes, while for the deep shadow zones the bottom-reflection modes must be taken into account. The approach is applied to the environment in the Philippine Sea, and the calculated results for frequencies from 109 to 860 Hz and ranges up to 240 km are in good agreement with the measured data.

On the basis of Fourier synthesis of frequency components, a WKBZ mode approach to pulse propagation in ocean channels is presented, and applied to calculations of propagation of a signal energy and waveform. For propagation of pulse signals with several bandwidths in an Arctic surface duct, the results calculated from the WKBZ code show that with increase of bandwidth the transmission loss curve of pulse-signal energy gradually becomes smooth and approaches that of the range-averaged intensity of the center frequency. For long range propagation of a band-limited signal with frequencies from 100 to 150 Hz in a North Pacific channel, signal waveforms, including arrival times and amplitudes at ranges from 44 to 4000 km, were calculated by using WKBZ and conventional normal mode (CNM) codes. A great number of calculations show that both the arrival times and amplitudes calculated from the WKBZ code are well consistent with those from the CNM code, but the computation speed of the WKBZ code is faster than that of the CNM code by a factor of over 100.

Proceedings from the eigenvalue equation of the normal modes in homogeneous shallow water, we derive several formulae for calculating the mode attenuation and group velocity, and compare their accuracy by means of numerical results. Especially discussed are the attenuation and group velocity of the critical mode in a Perkeris channel and it is shown that, in general, the attenuation and the group velocity of the critical mode, respectively, are less than the absorption and the sound speed in the bottom. Therefore, the Kornhauser, Raney, Weston and Tindle conclusions that the attenuation and the group velocity of the critical mode are exactly equal to the absorption and the sound speed in the bottom, respectively, are modified.

In this paper, the general expressions of long-range reverberation intensity in shallow water have been developed on the basis of the normal mode theory. Because the effects of the complex eigenvalues on the mode incident field have been considered, the results are more accurate than those in previous former normal mode theories of reverberation. In addition, for the sake of simplifying the calculations and making the results convenient to compare with experiments, the reverberation intensity has been smoothed by space averaging. The expressions obtained have obvious physical meaning and concise form so that they can be used for numerical calculation and analytical discussion. These expressions are suitable for wider types of velocity profile, bottom-reflection and scattering coefficients. As an example, the average reverberation intensity in shallow water with a thermocline is evaluated. The result shows that when both the source and receiver are located above the thermocline, the long-range reverberation intensity is proportional to r −5 . This result is in agreement with the experimental data.

In this paper, the sound field of a general type of directional radiator in a stratified medium is treated, and the concept of directivity is applied to calculation of the normal modes. The result shows that the normal mode field of a directional radiator can be obtained by supplementing the normal mode expression of an omnidirectional point source with the directional excitation function, which is dependent on the position and directivity of the radiator. In addition, the normal mode fields of radiators with vertical-symmetrical, vertical-antisymmetrical, single-sided and sharp directivities are calculated, respectively. For a vertical line array in a homogeneous water layer, if the source distribution is proportional to the eigenfunction of some normal mode, the zeros of the directional excitation function correspond precisely to the directions of the eigenrays of other normal modes.