Night Temperature Difference Research Articles

Optimizing Indoor Hemp Cultivation Efficiency through Differential Day–Night Temperature Treatment

This study was conducted to determine the optimal temperature difference in day–night indoor cultivation conditions to enhance the flower yield and functional component contents of female hemp plants. Hemp clones were cultivated under five distinct day and night temperature differences (DIF) during the reproductive stage. The daytime and nighttime temperature settings were as follows: 18:30 °C (negative 12 DIF), 21:27 °C (negative 6 DIF), 24:24 °C (0 DIF), 27:21 °C (positive 6 DIF), and 30:18 °C (positive 12 DIF). Seven weeks after transplantation, the growth parameters, leaf gas exchange, total phenolic compounds, 2,2-diphenylpicrylhydrazyl scavenging activity, and cannabinoid contents were analyzed. The total shoot biomass based on dry weight was highest at 21:27, reaching 41.76 g, and lowest at 30:18, measuring 24.46 g. However, the flower biomass, which is the primary production site, was highest at 24:24 and lowest at 18:30, showing a 4.7-fold difference. The photosynthesis-related parameters were temperature-dependent and strongly correlated with biomass production. The cannabinoid content of the hemp leaves increased at 21:27, whereas that of the hemp flowers increased at 27:21. The findings of this study indicate that the optimal temperature condition for female hemp flower production in a limited space is positive 6 DIF treatment, which corresponds to 27:21 °C. These results can contribute to advancements in indoor crop cultivation technology.

Hotter than Expected: Hubble Space Telescope (HST)/WFC3 Phase-resolved Spectroscopy of a Rare Irradiated Brown Dwarf with Strong Internal Heat Flux

With infrared flux contrasts larger than typically seen in hot Jupiter, tidally locked white dwarf–brown dwarf binaries offer a superior opportunity to investigate atmospheric processes in irradiated atmospheres. NLTT5306 is such a system, with a M BD = 52 ± 3 M Jup brown dwarf, orbiting a T eff = 7756 ± 35 K white dwarf with an ultra-short period of ∼102 minutes. We present Hubble Space Telescope/Wide Field Camera 3 spectroscopic phase curves of NLTT5306, consisting of 47 spectra from 1.1 to 1.7 μm with an average signal-to-noise ratio ∼ 65 per wavelength. We extracted the phase-resolved spectra of the brown dwarf NLTT5306B, finding a small <100 K day–night temperature difference (∼5% of the average day-side temperature). Our best-fit model phase curves revealed a complex wavelength-dependence on amplitudes and relative phase offsets, suggesting longitudinal–vertical atmospheric structure. The night-side spectrum was well fit by a cloudy, nonirradiated atmospheric model while the day side was best matched by a cloudy, weakly irradiated model. Additionally, we created a simple radiative energy redistribution model of the atmosphere and found evidence for efficient day-to-night heat redistribution and a moderately high Bond albedo. We also discovered an internal heat flux much higher than expected given the published system age, leading to an age reassessment that resulted in NLTT5306B most likely being much younger. We find that NLTT5306B is the only known significantly irradiated brown dwarf where the global temperature structure is not dominated by external irradiation, but rather its own internal heat. Our study provides an essential insight into the drivers of global circulation and day-to-night heat transport as a function of irradiation, rotation rate, and internal heat.

Terminator Habitability: The Case for Limited Water Availability on M-dwarf Planets

Rocky planets orbiting M-dwarf stars are among the most promising and abundant astronomical targets for detecting habitable climates. Planets in the M-dwarf habitable zone are likely synchronously rotating, such that we expect significant day–night temperature differences and potentially limited fractional habitability. Previous studies have focused on scenarios where fractional habitability is confined to the substellar or “eye” region, but in this paper we explore the possibility of planets with terminator habitability, defined by the existence of a habitable band at the transition between a scorching dayside and a glacial nightside. Using a global climate model, we show that for water-limited planets it is possible to have scorching temperatures in the “eye” and freezing temperatures on the nightside, while maintaining a temperate climate in the terminator region, due to reduced atmospheric energy transport. On water-rich planets, however, increasing the stellar flux leads to increased atmospheric energy transport and a reduction in day–night temperature differences, such that the terminator does not remain habitable once the dayside temperatures approach runaway or moist greenhouse limits. We also show that while water-abundant simulations may result in larger fractional habitability, they are vulnerable to water loss through cold trapping on the nightside surface or atmospheric water vapor escape, suggesting that even if planets were formed with abundant water, their climates could become water-limited and subject to terminator habitability.

Analysis of the influence of day and night temperature difference on oxygen concentration in ullage space of fuel tank

PurposeDetermining the variation law of the oxygen concentration in the ullage space of the fuel tank is the key to the design of the inert system. Among various factors affecting the oxygen concentration in the ullage space of the fuel tank, the temperature difference between day and night shows particular importance while relevant analysis and calculation are scarce.Design/methodology/approachThis study establishes a theoretical simulation model of the central wing fuel tank of an aircraft according to the relevant provisions of day-night temperature variation in FAR25 airworthiness regulations, verifies the model with the existing experimental data and discusses the corresponding relationship between the oxygen concentration in the ullage space of the fuel tank and the day-night temperature difference. The influence of day and night temperature difference, fuel type, fuel load rate, initial oxygen concentration, dissolved oxygen evolution and other factors on the oxygen concentration in the ullage space of the fuel tank were analyzed, and the limit of initial oxygen concentration of the fuel tank before the shutdown at night meeting the requirements of the airworthiness provisions was proposed.FindingsThe results show that the temperature difference between day and night, fuel load rate, initial oxygen concentration and other factors have different effects on the oxygen concentration in the ullage space of fuel tank. The initial oxygen concentration limit before shutdown shall be 2% below the 12% oxygen concentration stipulated by FAA.Research limitations/implicationsThe research results in this paper will be of good reference value to the design of the inert system and the calculation of the flammability exposure evaluation time. This paper aims to be good reference of the design of the inert system and the calculation of the flammability exposure evaluation time.Originality/valueThe research results of this paper can provide practical guidance for the current civil airworthiness certification work.

The first assessment of coarse-pixel soil moisture products within the multi-scale validation framework over Qinghai-Tibet Plateau

The validation of satellite soil moisture (SM) products is challenged by the large scale difference between in situ-satellite based measurements. In order to tackle the significant spatial scale mismatch, this study conducted a multi-scale validation of three typical SM products (i.e., SMOS-IC, SMAP L3, and AMSR2 LPRM) over Qinghai-Tibet Plateau. First, a 25-km better-performing SM dataset was produced by combining three SM products with the extended triple collocation (ETC) and arithmetic mean method. Second, a 500 m SM dataset was derived from the 25-km SM dataset with a random forest-based downscaling model and the high-resolution datasets of other variables. Third, the 500 m SM was evaluated using in situ SM measurements, which was then aggregated to a coarse pixel scale for the assessment of coarse-resolution satellite SM products. Finally, potential factors influencing the accuracy of satellite SM products were investigated. The results indicated that the 25-km merged SM product integrated the characteristics of these three SM products. During the downscaling process, terrain factors, NDVI, and day and night temperature difference were identified as the key variables to derive high-resolution SM, which agreed well with in situ measurements over most monitoring networks. The multi-scale validation results indicate that SMAP L3 and AMSR2 LPRM performs best regarding the median values of the correlation and deviation from the pixel scale reference in the spatial domain, respectively, and SMOS-IC is always the worst. However, when the pixel-based evaluation results were focused, AMSR2 LPRM performs best in most cases, followed by SMAP L3 and SMOS-IC. The accuracy of satellite SM products shows more dependence on slope than elevation, land cover types, and land surface temperature.

Bistability of the Atmospheric Circulation on TRAPPIST-1e

Using a 3D general circulation model, we demonstrate that a confirmed rocky exoplanet and a primary observational target, TRAPPIST-1e presents an interesting case of climate bistability. We find that the atmospheric circulation on TRAPPIST-1e can exist in two distinct regimes for a 1 bar nitrogen-dominated atmosphere. One is characterized by a single strong equatorial prograde jet and a large day–night temperature difference; the other is characterized by a pair of mid-latitude prograde jets and a relatively small day–night contrast. The circulation regime appears to be highly sensitive to the model setup, including initial and surface boundary conditions, as well as physical parameterizations of convection and cloud radiative effects. We focus on the emergence of the atmospheric circulation during the early stages of simulations and show that the regime bistability is associated with a delicate balance between the zonally asymmetric heating, mean overturning circulation, and mid-latitude baroclinic instability. The relative strength of these processes places the GCM simulations on different branches of the evolution of atmospheric dynamics. The resulting steady states of the two regimes have consistent differences in the amount of water content and clouds, affecting the water absorption bands as well as the continuum level in the transmission spectrum, although they are too small to be detected with current technology. Nevertheless, this regime bistability affects the surface temperature, especially on the night side of the planet, and presents an interesting case for understanding atmospheric dynamics and highlights uncertainty in 3D GCM results, motivating more multimodel studies.

Determination of the Suitability of the Newly Breed Güz Gülü Grape Cultivar for Cold Storage

In grape production, in order to maintain the competitive power in the domestic and foreign markets and to meet the market needs, it is necessary to have the product in a wide period of time. Especially late and high quality table grape varieties that are suitable for cold storage are needed. In the study, the suitability of Güz gülü grape variety for cold storage was investigated. The study was carried out during the harvest period of 2018 and 2019. The clusters were placed in bags weighing 5 kg and dual releasing SO2 pads with a dose of 0.9 g kg-1 of sulphur dioxide were placed in the bag. Müşküle variety was used as a control. After the applications, the grapes were stored for 90 days at 0-1 °C and 90±5% relative humidity. In order to determine the fruit quality characteristics of the samples at 15-day intervals throughout the storage period; weight loss, total soluble solids, titration acidity, maturity index, berry firmness, the removal force of the berries, cluster rachis color, decay rate, berry cracking rate and sensory analysis values were determined. It has been determined that Güz Gülü grape variety is not suitable for cold storage in Tekirdağ location due to the cracking of the skin. It was determined that the experiment should be done in locations with higher day and night temperature difference, better sun exposure and continental climate. In addition, it is recommended to apply calcium or other support components to increase the resistance of berry skin against cracking.

Circadian and seasonal variation in onset of acute myocardial infarction.

The aim was to investigate the circadian and seasonal variation of acute myocardial infarction (AMI). Clinical data of 3867 AMI patients hospitalized from November 2010 to October 2019 in the Border Yanbian Minority Autonomous Prefecture, China were collected, and 3158 patients with definite AMI onset times were analyzed. The clinical data analyzed included the time of onset, nationality, age, laboratory data. We divided the patients into 4 groups based on the timepoint of their AMI onsets: 00:00-05:59, 06:00-11:59, 12:00-17:59, and 18:00-23:59. We also divided the patients based on nationality: Chinese Korean and Han groups. We observed that there is a circadian rhythm in the incidence of AMI, and the peak of AMI is in the morning (7:00-9:00). Unexpectedly, the incidence of AMI was significantly lower in the cold winter than that of other 3 warm seasons (P < 0.01) and the peak of AMI presented at the months of the large contrast between day and night temperature difference (over 20°C) like May of Spring and October of Fall. Finally, there was no difference in circadian rhythm between Chinese Korean and Han, although these groups differed in age, body mass index, and the inflammatory cell level. These findings have shown a different seasonal and circadian variation in onset of AMI. Further studies are required to determine the pathophysiological mechanism(s) underlying these differences and to guide prevention of AMI for reducing its mortality and disability.

Effect of steel-wires and paraffin composite phase change materials on the heat exchange and exergetic performance of salt gradient solar pond

The addition of Phase Change Materials (PCM) to the salt gradient solar pond can significantly increase the heat capacity of the solar pond. Paraffin wax has a suitable range of phase transitions temperature and is feasible to be applied in solar pond. However, the poor thermal conductivity of paraffin is detrimental to thermal storage and release. In this study, the heat transfer behavior for the composite PCM of paraffin and steel wires has been studied firstly, the results shows that adding steel wires in paraffin improve the heat transfer performance obviously. With 10wt% adding percent, the maximum of heat transfer coefficient is 18.17 W/m2 °C−1 with increment of 18.84 % in melting process; and the maximum is 21.59 W/m2 °C−1 with increment of 20.88% during freezing process. Secondly, experiment study has been conducted in an experimental solar pond, with 20 PCM capsule tubes added, adding RT 50 and RT 60 made the day–night temperature differences 2.87 °C and 2.53 °C smaller than that of without any PCM conditions. In this study, adding RT 50 and RT 60 in solar pond achieve 9.34% and 14.13% exergy increments respectively. The study suggested that adding PCM to solar pond improves the quality of the heat energy of solar pond, and further extends the heat application scope of solar pond.

Changes in urbanization and urban heat island effect in Dhaka city

The study aimed to assess the changes in urban areas and UHI effects in Dhaka city, Bangladesh, from 2001 to 2017, using Moderate Resolution Imaging Spectroradiometer (MODIS) daily day- and nighttime land surface temperature (LST) data from 2001 to 2017. The expansion of the city was calculated using the city clustering algorithm (CCA). The temperature of the identified urbanized area was analyzed and compared with the adjacent regions. The changes in urban temperature were estimated using non-parametric statistical methods. The results showed that Dhaka city’s land surface area has grown by 25.33% and its inhabitants by 76.65% during 2001–2017. Urban expansion and dense settlements caused an increase in average temperature in some areas of Dhaka city nearly 3 °C compared to that at its boundary. The day and night temperature differences at Dhaka city’s warmest location and the coolest point outside the city were nearly 7 °C and 5 °C, respectively. The city’s annual average day- and nighttime temperatures was increasing at a rate of 0.03 °C and 0.023 °C/year over the period of the last 17 years. The rising temperature would increase the UHI effect in the future, which, combined with high humidity, may cause a significant increase in public health risk in the city if mitigation practices are not followed.

Graphical Analysis of Day - Night Temperature Difference by Interpolation and Approximation Methods for the Energy Converter of the Environment

Today, a lot of attention is paid to the search for environmentally friendly renewable energy sources. The most frequently considered such energy sources are wind energy, solar technology, the use of the energy of sea waves and biomass.Each of them has a drawback that prevents its widespread adoption. For example, wind farms create noise during their operation, are rigidly tied to the place where there are acceptable wind resources.To date, an energy converter has been developed, which works on the basis of the use of the ambient temperature difference during the day - the temperature is high during the day, and the temperature decreases at nightAs a rule, this temperature difference is in the range of about 5-9 degrees, although there are regions in which this difference is much higher, for example, in winter in Urengoy it can reach up to 30 degrees. An energy converter of this type is considered in works / 1-2/.The basis of the operation of such a converter is the change in the linear size of bodies, for example, plexiglass, with a change in temperature. When the temperature rises during the day, when the temperature is high, the rod lengthens, while at night, when the temperature is low, the linear dimensions of the rod decrease. This is exactly what is used to obtain energy through the use of a container. A conventional capacitor is used, one plate of which is fixed, the second plate of this capacitor is movable and connected to a dielectric plexiglass rod. When the temperature changes, for example, at a high temperature, the rod lengthens, the plates of the container come closer and the capacity will be maximum. At night, when the temperature decreases, the plexiglass rod is shortened, the plate moves away and the capacity decreases.If, at maximum capacity, the capacitor is charged and disconnected from the source, then the charge on it will be constant. At night, when the rod shrinks its linear dimensions, the movable plate moves away, the capacity falls. Since the charge on the container is constant, the voltage increases and we get an increase in energy, which is obtained from the day-night temperature difference and the change in the linear dimensions of the dielectric rod.

Combined environmental stresses induced by drip irrigation positively affect most solar greenhouse grown tomato fruit quality

To evaluate the potential for improvement of greenhouse grown tomato fruit quality under drip irrigation, this experiment was conducted in arid Northwest China for two consecutive growth cycles from 2017 to 2018 (summer and winter). Drip and furrow irrigation with different designed soil wetting proportions were employed in this study, and irrigation amounts were less in the drip than furrow irrigation. Results showed that the organoleptic quality, nutritional quality and antioxidant activity of tomato fruits generally improved under drip irrigation. However, compared with furrow irrigation, fruit fresh weight and size were significantly lower under drip irrigation in summer cycle, and the improvements in fruit quality attributes were relatively small in winter cycle. The combined environmental stresses, characterized by lower soil water content, higher air temperature, soil temperature and day and night temperature difference, were responsible for the improvements in fruit quality under drip irrigation. According to the correlation network analysis, firmness, b*, lycopene, β-carotene and total phenol were amongst the fruit quality parameters that essentially differed between drip and furrow irrigation. Furthermore, total phenol was important for the responses of tomato fruits to the combined environmental stresses under drip irrigation. In conclusion, drip irrigation in a naturally ventilated solar greenhouse could improve tomato fruit quality while achieving water-saving simultaneously.

The difference in temperature between day and night affects the strawberry soluble sugar content by influencing the photosynthesis, respiration and sucrose phosphatase synthase

Plenty of studies have demonstrated that DIF has an effect on the fruit growth. To study the effects of day and night temperature differences on the strawberry sugar quality, an experiment using climate chambers was conducted. Five different differences between the day and night temperatures (DIF) were set, which were 6 °C (28 °C/22 °C, day/night temperature), 8 °C (29 °C/21 °C), 10 °C (30 °C/20 °C), 12 °C (31 °C/19 °C), 14 °C (32 °C/18 °C). The results showed the following indices peaked with a DIF of 12 °C, including the photosynthesis rate, glucose content, fructose content, sucrose content, soluble sugar content and sugar metabolic enzyme activity. The respiration rate increased with the DIF during the day and decreased with the DIF at night. The root dry weight peaked at a DIF of 10 °C, the stolon dry weight peaked at a DIF of 8 °C and the leaf dry weight peaked at a DIF of 6 °C; however, the fruit dry weight reached maximum values at a DIF of 12 °C. The Grey correlation analysis showed that the most important factor in our experiment affecting the fructose content was the sucrose phosphate synthase; however, for the sucrose, glucose, and soluble sugars, the most important factor was the photosynthesis. We found that a DIF of 12 °C (31 °C/19 °C, day/night temperature) was the most suitable for strawberry growth, especially for the sugar content accumulation.

Lunar Surface Temperature and Emissivity Retrieval From Diviner Lunar Radiometer Experiment Sensor

AbstractThe lunar surface temperature (LST) derived from thermal infrared (TIR) measurements can aid in understanding the physical properties of the lunar surface. The Diviner Lunar Radiometer Experiment (herein, Diviner) sensor provides global lunar surface observation in seven TIR channels. However, its retrieval of LST constantly uses a single emissivity value (i.e., 0.95) by ignoring the spatial variation of lunar surface, thereby reducing the accuracy of temperature and day–night temperature difference. To overcome this problem, this study developed a physical method called temperature–emissivity separation (TES) algorithm to retrieve LST and lunar surface emissivity from the daytime observation in three Christiansen Feature (CF) channels (7.55–8.05, 8.10–8.40, and 8.38–8.60 μm) of the Diviner, and then used the emissivity from daytime observation to inverse LST at nighttime observation. Findings showed that the TES algorithm could retrieve LST and emissivity with an error of less than 0.8 K and 0.008, respectively. However, observation noise significantly affected the retrieval accuracy, particularly for the low‐temperature pixels; moreover, high retrieval accuracy requires a surface temperature higher than 240 K. The new algorithm was applied to obtain the daytime and nighttime LST and emissivity from the Diviner images. Results showed that the LST retrieved from the algorithm differed approximately 3.9 K from that calculated from a single emissivity 0.95. Finally, an example of global surface temperature and emissivity were obtained. Consequently, the CF pixels were found to distribute in the latitude range from −60° to 60°; however, they did not have a large distribution in high‐latitude and near‐polar regions.

“Covering Effects” under Diurnal Temperature Variations in Arid and Semiarid Areas

“Covering effects” dominated by water vapor migration in arid and semiarid areas threaten the stability of engineering entities. To explore the “covering effects” dominated by water vapor migration under the influence of diurnal temperature variations, a series of one‐side evaporation experiments were conducted. Characteristics of water vapor migration between the unsaturated loess soil column with and without a lid were compared in detail to illustrate the “covering effects” on water vapor migration, as were the effects of test time. Further, the characteristics of “covering effects” in loess and sand soil columns were compared. The results show that the “covering effects” formed in the loess soil column with a lid by cycling day and night temperature differences led water vapor to accumulate and condense beneath the lid. However, unlike the “covering effects” during freezing conditions that lead to a significant increase in the moisture content in the top layer, in this study, the moisture content in the top layer (0–8 cm) decreased. Although “soil lid” and the “soil covering effects” exist in both loess soil columns with and without lids, the “soil covering effects” for the former are much more obvious, and the moisture content in the upper part of the loess soil column (8–45 cm) shows a significant increase. By cycling day and night temperature differences, the “covering effects” or “soil covering effects” grew as the test time increased. Compared to the loess soil column, the “covering effects” in the sand soil column were extremely weak, and the moisture migration in the sand soil column was dominated by the downward movement liquid water. This paper illustrates the “covering effects” under the influence of diurnal temperature variations and reveals the mechanism of water vapor migration in subgrade soils in arid and semiarid areas.

Modeling of Surface Temperature for Near-Earth Asteroid 2016HO3

On April 18, 2019, the China National Space Administration (CNSA) published the plan of asteroid exploration, which would select the near-earth asteroid 2016HO3 as one of its targets. On this paper, the parameters of 2016HO3 for thermal environment analysis were discussed. By investigating the current international observation data, the environmental parameters of 2016HO3 are obtained preliminarily. Then the near-Earth asteroid thermal model(NEATM) and asteroid thermal physics model (TPM) were used to model and analyze the surface temperature of 2016HO3, and the upper boulder of the temperature was 412 K. Considering the spinning effect, the day and night temperature difference at different locations was simulated and analyzed, and the temperature analysis method under the polar night conditions was proposed, then the maximum temperature difference at any position was determined to be about 30 K. Last on the basis of TPM, by the idea of the average illumination during the rotation period, the temperature analysis method of the polar night was proposed, and lower limit of temperature of 2016HO3 was achieved.

Estimation of Urbanization Impacts on Local Weather: A Case Study in Northern China (Jing-Jin-Ji District)

With the past rapid economic development and large population growth, Jing-Jin-Ji District has been undergoing rapid urbanization, which has caused considerable regional weather changes in local regions. In this paper, we used the Weather Research and Forecasting (WRF) model to quantitatively analyze the effects of past urbanization and potential future urbanization on the regional weather in the center of Jing-Jin-Ji District. The hydrometeorological data from two weeks in July 2019 were used to simulate the influence of urbanization on local weather in the Jing-Jin-Ji District at regional scales using a single-layer canopy parameterization scheme. To better quantify the differences in temperature and precipitation induced by urbanization, three simulation scenarios were designed, which were no urban cover (NU), current urbanization cover (CU), and full urban land cover (FU), respectively. The results showed that: (1) Urbanization progress (from NU to CU and from CU to FU) in Jing-Jin-Ji District increased the daytime temperature, night temperature, and temperature difference between day and night, while decreasing the total rainfall and peak rainfall. (2) Compared with NU, the mean temperature of the CU and FU increased 0.3 K and 0.6 K, respectively, and the mean precipitation of CU and FU decreased by approximately 6% and 8.4%, respectively. (3) The main influence of urbanization on weather was reflected by the maximum temperature and peak rainfall, while the other impacts were relatively insignificant. (4) Compared with NU, the maximum temperature of CU and FU increased 0.82 K and 1.35 K, respectively, and the peak rainfall of NU and FU decreased by approximately 9.5% and 19.0%, respectively; The results of this study bring to light the urban management strategies for policy makers.

Divergent Response of Leaf Coloring Seasons to Temperature Change in Northern China over the Past 50 Years

Autumn phenology plays a critical role in terrestrial ecosystem circulations. However, the changes in autumn phenology and their correlation with temperature remain uncertain because mean temperature alone was not able to determine the changes in autumn phenology at various sites. Here, the leaf coloring season (LCS) was defined as the period when the leaves of more than half of the species had recognized changes in color. We systematically studied the changes in peak, start, end, and duration of LCS and their correlations with five temperature parameters (mean temperature, accumulated cold temperature, day temperature, night temperature, and temperature difference between day and night) in four periods. Similarly to previous findings, the start date of LCS advanced and the end of LCS delayed over the past 50 years, which consequently led to a lengthened duration of LCS in Xi’an, Harbin, Minqin, and Shenyang. In general, the rise in mean temperature, day temperature, and night temperature would delay the peak, start, and end of LCS and lengthen the duration of LCS in most cases. We also proved that the changes in LCS metrics not only could completely be explained by mean temperature but also were influenced by day temperature, night temperature, temperature difference, and even other climatic factors such as precipitation, at different sites.

The KLMY90 # Asphalt and Its Mixture Performance Research for Gannan Area

Asphalt pavement is widely used at home and abroad because of its advantages of comfortable driving, convenient maintenance, short construction period, etc. Asphalt becomes brittle and is cracked in winter. Gannan is located in the plateau, belonging to plateau climate, low year-round temperature, often wind and rain, day and night temperature difference, strong sunlight. Therefore, the asphalt was selected with high temperature stability and low temperature ductility. The KLMY90# asphalt and its mixture were studied for the technical properties. The results showed: the content of saturates and aromatic components reduced at aging temperature; the saturated and aromatic content decreased at aging time; the saturated content decreased slowly than the content of aromatic content as the aging time decreasing; the dynamic stability increased with the asphalt-aggregate ratio; the asphalt mixture had superior performance, strong water resistance. The KLMY90# asphalt and its mixture were more suitable for paving roads for Gannan.

Grain yield responses of lowland rice varieties to increased amount of nitrogen fertilizer under tropical highland conditions in central Kenya

Tropical highland conditions in Mwea Kenya, ensure the high radiation and the large day–night temperature differences. Such conditions are generally believed to promote rice growth and yield, but the current grain yield is lower than the expectation. In the current standard N fertilizer practice in Mwea, 75 kg nitrogen (N) ha−1 is applied in three splits at fixed timing. The effects of increases in N fertilizer amount (125, 175, and 225 kg N ha−1) on rice growth and yield were evaluated to test the hypothesis that unachieved high rice grain yield in Mwea is due to insufficient amount of N fertilizer. Two popular lowland varieties in Mwea (Basmati 370 and BW196) and two varieties reported as high yielding in other countries (Takanari and IR72) were used. Shoot dry weight (DW) increased with increases in the amount of N fertilizer applied in three splits at fixed timing, irrespective of variety. It reached approximately 20 t ha−1 under increased N conditions (>75 kg N ha−1) in several cases, indicating that high biomass production could be achieved by increasing N application rate. However, the increased biomass did not increase grain yield, due to decreased grain filling under high N conditions in all varieties. Thus, N amounts above 75 kg ha−1 were ineffective for increasing grain yields in Mwea, where N fertilizer was applied in three splits at fixed timing. Increasing influence of low temperature under high N conditions may be one of the reasons for the decreased grain filling in Mwea.