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Agricultural extension requires close communication with farmers, and researchers must consider farmers’ perspectives on crop management. Farmers tend to take into account the canopy appearance when they decide on fertilizer application, and this is often neglected in crop management recommendations by researchers. Our objectives were to dissect the growth characteristics that farmers implicitly account for in nutrient management of tropical rice. Farmer participatory trials were conducted in irrigated and rainfed lowlands in the Philippines during the wet seasons of 2014, 2015, and 2016. Each year, 30 participating farmers made decisions on fertilizer management for plots with different seedling ages and planting densities. These treatments greatly changed the canopy appearance, and affected farmer decisions on nitrogen (N) management, particularly in the first year. We found that plant height and leaf greenness were the major determinants of their decisions in irrigated lowlands. Under rainfed conditions, the risk of drought made farmers focus on tillering rather than plant elongation and leaf color during early growth stages, and on canopy cover and plant elongation during later stages. Across years and water regimes, farmers applied 78% more N than researchers without generally increasing grain yield. Since crop diagnosis is a key for successful management by farmers, guidelines for efficient nutrient management should include numerical targets for the traits emphasized by farmers. That will help farmers better understand their crops, and the guidelines will be more user-friendly than providing only a fertilizer application prescription.
More than 10 Sub1 rice varieties carrying the submergence-tolerance gene have been released for flood-prone environments in tropical Asia. Improved management practices have been shown to enhance yields of these varieties. The objective of this study was to dissect the growth response of IR64-Sub1 to integrated crop management in a flash flood at the late vegetative stage. Field experiments were conducted at the International Rice Research Institute, Philippines in the dry and wet seasons of 2013. Complete submergence was imposed for 14 days starting at 37 days after transplanting. Integrated management practice (IMP) consisting of: (i) application of fertilizer (compared with no fertilizer use in conventional practice), (ii) use of lower seeding rate (400 vs. 800 kg ha−1) in the nursery bed, (iii) use of slightly older seedling for transplanting (30 vs. 18 day-old), and (iv) higher planting density (33.3 vs. 25.0 hills m−2) gave yields higher by 8–87% compared with the conventional practice (1.3–2.4 t ha−1) in both seasons. This was attributable to higher shoot biomass after water recession, more tillers m−2, greater leaf area expansion and shoot biomass accumulation during the recovery period, and higher filled-grain percentage at maturity. The improved management had no positive effect on panicle formation, spikelets panicle−1, and harvest index since stress was imposed at the transition period between vegetative and reproductive phases. Our results suggest the appropriate nursery management, for submergence-resilient seedlings to further alleviate damage caused by flash floods and increase the yield of Sub1 varieties in flood-prone rainfed lowlands.
Root rots are one of the main biotic constraints to common bean (Phaseolus vulgaris L.) production, causing losses estimated at 221 000 metric tons a year in sub-Saharan Africa. Until recently, root rots in Ugandan common bean agroecologies were mostly caused by Pythium and Fusarium spp., especially in high altitude areas. But now, severe root rots are observed in low and medium altitude agroecologies characterized by dry and warm conditions. The objective of our study was therefore to ascertain the current prevalence and incidence of common bean root rot diseases in Ugandan common bean agroecologies. Our results show that root rots were present in all seven agroecologies surveyed. Overall, the most rampant root rot was southern blight caused by Sclerotium rolfsii Sacc., followed by root rots caused by Fusarium spp., Pythium spp. and Rhizoctonia solani, respectively. Our study clearly showed the influence of environmental conditions on the prevalence and incidence of common bean root rots. While Fusarium and Pythium root rots are favoured under low air temperature and high air humidity in highland areas, high incidence of southern blight is favoured by warm and moist conditions of lowland areas. The prevalence and incidence of common bean root rots was mapped, providing a reliable baseline for future studies. Similarly, hotspots identified for common bean root rots will be a very useful resource for evaluation of germplasm and breeding lines for resistance to root rots.
The Global Muon Detector Network (GMDN) is composed by four ground cosmic ray detectors distributed around the Earth: Nagoya (Japan), Hobart (Australia), Sao Martinho da Serra (Brazil) and Kuwait city (Kuwait). The network has operated since March 2006. It has been upgraded a few times, increasing its detection area. Each detector is sensitive to muons produced by the interactions of ~50 GeV Galactic Cosmic Rays (GCR) with the Earth′s atmosphere. At these energies, GCR are known to be affected by interplanetary disturbances in the vicinity of the earth. Of special interest are the interplanetary counterparts of coronal mass ejections (ICMEs) and their driven shocks because they are known to be the main origins of geomagnetic storms. It has been observed that these ICMEs produce changes in the cosmic ray gradient, which can be measured by GMDN observations. In terms of applications for space weather, some attempts have been made to use GMDN for forecasting ICME arrival at the earth with lead times of the order of few hours. Scientific space weather studies benefit the most from the GMDN network. As an example, studies have been able to determine ICME orientation at the earth using cosmic ray gradient. Such determinations are of crucial importance for southward interplanetary magnetic field estimates, as well as ICME rotation.
Designing bioactive materials, with controlled metal ion release, exerting significant bioactivity and associated low toxicity for humans, is nowadays one of the most important challenges for the scientific community. In this work, we propose a new material combining the well-known antimicrobial properties of copper nanoparticles (CuNPs) with those of bioactive chitosan (CS), a cheap natural polymer widely exploited for its biodegradability and nontoxicity. Here, we used ultrafast femtosecond laser pulses to finely fragment, via laser ablation, a Cu solid target immersed into aqueous CS solutions. Homogeneously dispersed copper-chitosan (Cu-CS) colloids were obtained by tuning the Cu/CS molar ratios, according to the initial chitosan concentration, as well as other experimental parameters. Cu-CS colloids were characterized by several techniques, like UV-Vis and X-ray Photoelectron spectroscopies (XPS). Transmission Electron Microscopy (TEM) was used to morphologically characterize the novel nanocomposites.
Nano-sized SiOx/C composite was successfully prepared by drip combustion in a fluidized bed reactor. A mixture of tetraethyl orthosilicate (TEOS) ant kerosene at a 2:3 volume ratio was used as a precursor solution. The synthesis was carried out between 600 °C and 900 °C. The as-prepared powder (600 °C) consists of SiOx and carbon particles which are approximately ranged from 30 to 80 nm. For the nano-sized SiOx/C composite sample, the heat treatment process was introduced to remove incomplete combustion materials and the dry ball milling was performed to homogenize the distribution of carbon inside the sample. The final sample (nano-sized SiOx/C nanocomposite) was used as an electrode active material and then electrochemical testing was performed. The cell exhibited discharge and charge capacities of 1158 and 533 mAh g-1, respectively, at current density of 50 mAh g-1 in the voltage range between 0.01-3 V versus Li/Li+.
The 3D morphological evolution of titanium foams as they undergo a two-step fabrication process is quantitatively characterized through x-ray micro- and nano-tomography. In the first process step, a Cu–Ti–Cr–Zr prealloy is immersed in liquid Mg, where Cu is alloyed with Mg while a skeleton of crystalline Ti–Cr–Zr is created. In the second step, the Mg–Cu phase is etched in acid, leaving a Ti–Cr–Zr foam with submicron struts. 3D images of these solidified Ti–Cr–Zr/Mg–Cu composites and leached Ti–Cr–Zr foams are acquired after 5, 10, and 30 min exposure to liquid Mg. As the Mg exposure time increases, the Ti–Cr–Zr ligaments grow in size. The tortuosity loosely follows the Bruggeman relation. The interfacial surface distribution of these Ti-foams is qualitatively similar to other nano-porous metal prepared by one-step dealloying. The characteristic length of the Mg–Cu phase and pores are also reported.
Corium which simulates the molten core of a Boiling Water Reactor was prepared as a parameter of Zr content, and melting temperatures and thermal conductivities were measured. The melting temperatures were measured by the thermal arrest method and were 2622 oC, 2509 oC and 2540 oC, respectively, in the specimens of 24.3 at%, 49.0 at% and 73.5 at% Zr content. Thermal conductivities had low values of 2.0-3.5 W/m oC at temperatures of 400 to 1600 oC.
In this study, sintered pellets were prepared from Zircaloy-2 oxide and UO2 as a parameter of content ratio (Zr contents were 0, 24.3, 49.0, 73.4, and 97.9 at% in metal). The sintered pellets were heated in 5%H2/Ar gas. UO2 pellets underwent simple thermal expansion caused by thermal vibration while Zircaloy-2 oxide pellets underwent thermal expansion and volume change with phase transformation. Finally, the 24.3, 49.0, and 73.5 at%Zr-UO2 pellet specimens showed both phenomena. However, phase transformation temperatures were lower than that of Zircaloy-2 oxide, and volume changes were much smaller. X-ray diffraction patterns obtained after thermal expansion measurements showed that the 24.3 at%Zr-UO2 specimen contained tetragonal and cubic (Zr, U)O2 while the 73.5 at%Zr-UO2 specimen contained mainly monoclinic ZrO2.
Oxygen potentials of PuO2-x were measured at temperatures of 1473 - 1873 K by thermo-gravimetry. The oxygen potentials were determined by in situ analysis as functions of oxygen-to-metal ratio and temperature. The measurement data were analyzed on the basis of defect chemistry and an approximate equation was derived to represent the relationship among temperature, oxygen partial pressure, and deviation x in PuO2-x.
Iodine filters expended after nuclear fuel reprocessing contain radioactive iodine (I-129), almost all of which exists as silver iodide (AgI). The synthetic rock technique is a solidification treatment technique using hot isostatic press (HIP), in which the alumina adsorbent base material is synthesized to form a dense solidified material (synthetic rock), and I-129 is physically confined in the form of AgI in the alumina matrix. Thus, it is necessary to understand the matrix dissolution behavior to evaluate the iodine release behavior.
Experiments involving the dissolution of the matrix were carried out under various temperatures (35–70 °C) and pH values (10–12.5) that reflect the disposal conditions. The results of the experiments showed that the dissolution rate of Al visibly increases with temperature and pH. The dissolution rate constant was calculated from the initial data assuming the dissolution of the matrix as a primary reaction. The logarithmic rate constant showed a good linear correlation with the pH and the reciprocal of temperature. The 27Al-NMR analysis of the solutions of the dissolved matrix showed that the major chemical species present in the solutions was Al(OH)4-. This indicated that the dissolution of the matrix can be described by the following equation: Al2O3 + 2OH- + 3H2O → 2Al(OH)4-. Subsequently, the empirical equation of the rate of dissolution of the matrix as a function of the temperature and pH was derived. It will be used to evaluate the iodine release behavior from the synthetic rock.
We present the results and critical analyses of recent studies of ultrafast optical nonlinearities of liquid crystals in the isotropic and ordered phases for time scales spanning femtoseconds – microseconds. Pure undoped liquid crystals as well as liquid crystals containing plasmonic nano-particles have been investigated. Individual molecular electronic optical nonlinearities are found to be useful for femtoseconds – nanoseconds nonlinear transmission clamping applications. On the other hand, laser induced order parameter and birefringence modification in aligned nematic cells allow very rapid transmission switching of visible as well as near infrared lasers with response times in the sub-microseconds - few nanoseconds regime.
We compare the merits of potential observatory sites on the Antarctic Plateau, in regard to the boundary layer, cloud cover, free atmosphere seeing, aurorae, airglow, and precipitable water vapour. We find that (a) all Antarctic sites are likely compromised for optical work by airglow and aurorae; (b) Dome A is the best existing site in almost all respects; (c) there is an even better site (“Ridge A”) 150 kms SW of Dome A; (d) Dome F is a remarkably good site except for aurorae; (e) Dome C probably has the least cloud cover of any of the sites, and might be able to use a predicted `OH hole' in the Spring.
This work presents some observations during the period of the Whole Heliosphere Interval (WHI) of the effects of interplanetary (IP) structures on the near-Earth space using three sets of observations: magnetic field and plasma from the Advanced Composition Explorer (ACE) satellite, ground-based cosmic ray data from the Global Muon Detection Network (GMDN) and geomagnetic indices (Disturbance storm-time, Dst, and auroral electrojet index, AE). Since WHI was near minimum solar activity, high speed streams and corotating interaction regions (CIRs) were the dominant structures observed in the interplanetary space surrounding Earth. Very pronounced geomagnetic effects are shown to be correlated to CIRs, especially because they can cause the so-called High-Intensity Long-Duration Continuous AE Activity (HILDCAAs) - Tsurutani and Gonzalez (1987). At least a few high speed streams can be identified during the period of WHI. The focus here is to characterize these IP structures and their geospace consequences.
Phosphorus doping on (001)-oriented diamond is introduced and compared with results achieved on (111) diamond. Detailed procedures, conditions, doping characteristics, and recent electrical properties of (001) phosphorus-doped diamond films are described. Now the highest mobility is reached to be ∼780 cm2/Vs at room temperature. The carrier compensation ratio, which is still high around 50-80 %, is the most important issues for (001) phosphorus-doped diamond to improve its electrical property. The origin of compensators in phosphorus-doped diamond is investigated, while yet to be identified.
Ultraviolet light emitting diode with p-i-n junction structure is also introduced using (001) n-type diamond. A strong UV light emission at around ∼240 nm is observed even at room temperature. High performance of diamond UV-LED is demonstrated.
We have investigated the thickness dependence of critical current for YBa2Cu3O7-x (YBCO) film with artificial pinning centers on metallic substrate. Artificial pinning centers were introduced by the pulsed laser deposition (PLD) using YBCO target including YSZ particles. The film over 1 μm in thickness exhibited with high critical current (Ic) of 40.7A in applied magnetic field of 3T parallel to the c-axis at 77K. This value was 5 times as high as the normal YBCO film without artificial pinning centers. The large Ic enabled us to approach to a practical application in the near future. Furthermore, it was clarified that the columnar nano-structure formed in the film, we call “the bamboo structure”, was a dominant pinning center because each Jc-θ curve of all thick films formed a universal line by the normalization of Jc. In addition, it was also found that YSZ addition has an optimal concentration for pinning by the study of YSZ concentration in the film.
Aqueous dissolution tests of AgI were performed in Na2S solutions in order to evaluate, empirically, dissolution of AgI to release iodine under reducing conditions with sulfide. The results indicated that AgI dissolves to release iodine being controlled by mainly precipitation of Ag2S. However, the dissolution of AgI can be depressed to proceed, and the thermodynamic equilibrium cannot be attained easily. Solid phase analysis for the reacted AgI suggested that a thin layer of solid silver forming at AgI surface may evolve to be protective against transportation of reactant species, which can lead to the depression in the dissolution of AgI.
We determined the most probable atomistic structure of an ultra-low-k material (k≅ 2.5) by computer simulations. Among the candidate structures generated by a molecular-dynamics calculation, the most probable one that reproduces the observed properties was selected using a first-principles density-functional-theory calculation. The candidate structures consisted of Si-O-Si network with some silicon atoms, each of which had a CH3 group or a hydrogen atom bonded. The structure with CH3 groups but no hydrogen atom reproduced the experimental properties best. This structure was then used to investigate the behaviors of the material irradiated with ultraviolet light.
We report on the novel normally-off GaN-based heterojunction field effect transistors (HFETs) on a Si substrate. The AlGaN/AlN/GaN heterostructure was grown using a metalorganic chemical vapor deposition (MOCVD). The HFET for a normally-off operation was fabricated using a precisely controlled thin-AlGaN layer as an electron supply layer. As a result, the HFET was operated at the condition of the positive gate bias. We also characterized the enlarged gate-width devices. The breakdown voltage of FET was over 300 V. A normally-off operation using GaN based HFETs with a thin-AlGaN/AlN/GaN heterostructure on the silicon substrate were thus confirmed for the first time.