新闭路循环式面具呼吸测热法的研究

呼吸测热是研究家畜能量代谢,确定家畜的能量需要和评定饲料能量价值的重要方法。常用有呼吸室和呼吸面具法。近几十年来,大家畜的呼吸室发展较快。呼吸室法准确可靠,能长时持续测定,但设备较复杂,成本很高,至今在国际上只少数研究单位有大家畜呼吸室。常用的非呼吸室法有面具和头套法,由于装置成本低,能携带至现场测定,在国际上仍继续使用,但传统面具法(开路集气袋法)目前应用的不普遍。国内现刚     

Air containing nitrogen-15 ammonia: foliar absorption by corn seedlings

Thirty-day-old corn seedlings, grown in the greenhouse with different concentrations of supplemental nitrate nitrogen, were moved to a constant-temperature growth chamber and sealed in a 560-liter tent made of polyvinyl chloride. The plants were exposed to air containing ammonia labeled with nitrogen-15 (1, 10, and 20 parts per million) for 24 hours and then harvested. The nitrogen-15 content of the tops and roots showed that at 1 part per million 43 percent of the ammonia was absorbed, whereas at 10 and 20 parts per million, 30 percent of the ammonia was absorbed. The results demonstrate that growing plants may be a natural sink for atmospheric ammonia.     

植物体氮素的挥发损失——Ⅳ.玉米生长过程中挥发损失的氮素

把玉米植株和用经磷酸甘油液浸泡的塑料泡沫覆盖的生长介质(土壤)同置于密闭的生长室中,捕获测定了玉米整个生育过程中挥发的氨气。结果表明,玉米能挥发出少量的氨,中后期62d挥发量约为200g/ha;后期挥发量较前期大,约6g/d·ha(N)。温度、叶子衰老程度、施氮水平对氨气挥发量未表现出明显影响。玉米挥发的氨量不稳定,变异较大。     

Gaseous-diffusion porometer for continuous measurement of diffusive resistance of leaves

We describe a porometer that enables continuous monitoring of the stomatal diffusive resistance of leaves. The flux is measured of a gas-such as nitrous oxide-diffusing through a leaf that divides an enclosing chamber into two compartments. Nitrous oxide is added in known concentration to the airstream passing through the compartment on one side of the leaf and is recovered from the airstream passing through the opposite compartment. From measurements of the difference in concentration across the leaf and of the flux, the diffusive resistance of the leaf to N(2)O is calculated; this value, adjusted for resistance external to the leaf, gives a continuous record of internal diffusive resistance. This record can be made simultaneously with measurements of transpiration and photosynthesis.     

Thermal conductivity of monolithic organic aerogels

The total thermal conductivity lambda of resorcinol-formaldehyde aerogel monoliths has been measured as a function of density rho in the range from rho = 80 to 300 kilograms per cubic meter. A record-low conductivity value in air at 300 K of lambda approximately 0.012 watt per meter per kelvin was found for rho approximately 157 kilograms per cubic meter. Caloric measurements under variation of gas pressure as well as spectral infrared transmission measurements allowed the determination of solid conductivity, gaseous conductivity, and radiative conductivity as a function of density. The development of such low conductivity materials is of great interest with respect to the substitution of environmentally harmful insulating foams made from chlorofluorocarbons.     

Heat transfer measurements of the 1983 kilauea lava flow

Convective heat flow measurements of a basaltic lava flow were made during the 1983 eruption of Kilauea volcano in Hawaii. Eight field measurements of induced natural convection were made, giving heat flux values that ranged from 1.78 to 8.09 kilowatts per square meter at lava temperatures of 1088 and 1128 degrees Celsius, respectively. These field measurements of convective heat flux at subliquidus temperatures agree with previous laboratory measurements in furnace-melted samples of molten lava, and are useful for predicting heat transfer in magma bodies and for estimating heat extraction rates for magma energy.     

升温环境下肉鸡体温和呼吸频率对热中性区上限温度估测

目的 通过非线性分段回归模型,分析随环境温度逐渐升高,肉鸡体表、体核温度和呼吸频率开始升高时的环境温度,即拐点温度（IPT）,估测肉鸡热中性区、热舒适区的上限温度。方法 试验选择21日龄AA肉鸡10只,饲养于人工环境控制舱内。舱内温度由18℃开始,每0.5 h升高1℃,至33℃维持0.5 h后,逐渐降至20℃,循环3 d。利用微型温度记录仪连续监测肉鸡体表和体核温度（每10min记录1次）。结果 经非线性分段回归分析,3次（天）估测出的肉鸡体表温度的拐点温度（IPT_ST）分别为21.18、21.09、21.13℃,平均21.13℃。肉鸡IPT_ST个体之间的变异较大,3次测定的变异系数分别为6.31、6.15、5.64;而同一只肉鸡3次估测的IPT_ST差别较小,10只鸡的变异系数平均为0.52,表明这种估测IPT_ST的方法重复性较好。肉鸡体核温度的拐点温度（IPT_CT）3次测定的结果分别为27.80、27.98、27.67℃,平均27.82℃。个体之间IPT_CT的变异系数为2.82、2.75、2.78,而同只肉鸡3次估测的IPT_CT变异较小,平均变异系数为0.90,表明这种估测IPT_CT的方法重复性较好。肉鸡呼吸频率的拐点温度（IPT_RR）3次测定的结果分别为28.42、29.52、29.25℃,平均29.06℃。由于肉鸡在高温环境下喘息并非持续发生,本试验呼吸频率的测定时间过短（每个温度下每只鸡测定了1 min）,造成部分肉鸡测定的呼吸频率过低,导致估测的IPT_RR偏高。结论 根据热中性区的定义,3—4周龄肉鸡热舒适区上限温度即为IPT_ST（21.13℃）,而热中性区上限温度应低于IPT_CT（27.82℃）。     

Crustal Layer of Seismic Velocity 6.9 to 7.6 Kilometers per Second under the Deep Oceans

Refraction measurements made in the deep ocean between the Marshall and Hawaiian islands reveal a layer of seismic velocity 7.3 kilometers per second between the 6.8 kilometer per second oceanic crustal layer and the mantle. This layer, normally masked as a second arrival, is revealed by continuous air gun refraction data. The layer may be widespread in the deep oceans.     

Molecular light emission induced by inelastic electron tunneling

Light emission from molecular layers has been induced by inelastically tunneling electrons in a tunneling junction. The fast quenching of molecular emission on metal surfaces was suppressed by use of the "transparent conductor" indium-tin-oxide for the junction electrodes. The emission measurements have been made in squeezable tunneling junctions as small as 10(-9) square centimeters, coated with 9-10 dichloro-anthracene layers. At a bias of 2.5 to 3.5 volts, yields of 5000 photons per microcoulomb were observed. Evidence for the molecular origin of the emission is given. This method shows good prospects for use in the imaging of chromophores on surfaces with atomic resolution.     

Laser frequency combs for astronomical observations

A direct measurement of the universe's expansion history could be made by observing in real time the evolution of the cosmological redshift of distant objects. However, this would require measurements of Doppler velocity drifts of approximately 1 centimeter per second per year, and astronomical spectrographs have not yet been calibrated to this tolerance. We demonstrated the first use of a laser frequency comb for wavelength calibration of an astronomical telescope. Even with a simple analysis, absolute calibration is achieved with an equivalent Doppler precision of approximately 9 meters per second at approximately 1.5 micrometers-beyond state-of-the-art accuracy. We show that tracking complex, time-varying systematic effects in the spectrograph and detector system is a particular advantage of laser frequency comb calibration. This technique promises an effective means for modeling and removal of such systematic effects to the accuracy required by future experiments to see direct evidence of the universe's putative acceleration.     

Recent changes in atmospheric carbon monoxide

Measurements of carbon monoxide (CO) in air samples collected from 27 locations between 71 degrees N and 41 degrees S show that atmospheric levels of this gas have decreased worldwide over the past 2 to 5 years. During this period, CO decreased at nearly a constant rate in the high northern latitudes. In contrast, in the tropics an abrupt decrease occurred beginning at the end of 1991. In the Northern Hemisphere, CO decreased at a spatially and temporally averaged rate of 7.3 (+/-0.9) parts per billion per year (6.1 percent per year) from June 1990 to June 1993, whereas in the Southern Hemisphere, CO decreased 4.2 (+/-0.5) parts per billion per year (7.0 percent per year). This recent change is opposite a long-term trend of a 1 to 2 percent per year increase inferred from measurements made in the Northern Hemisphere during the past 30 years.     

Strong, pure, and uniform carbon fibers obtained directly from the vapor phase

With laser-assisted chemical vapor deposition, strong and flexible carbon fibers were obtained at high reaction chamber pressures (> 1 bar) with growth rates > 0.3 millimeter per second; their tensile strength (3 gigapascals) approaches that of commercial intermediate modulus carbon fibers made by conventional process routes. With the process described here, carbon fibers can be produced with superior chemical purity and structural uniformity. They may become the material of choice in currently emerging premium end uses, including carbon fiber infrared detection elements.     

气隔式油脂密封下部卸油装置

国内目前铁路油罐车轻质油品的装卸多数采用上装上卸式，此方式存在许多难以解决的问题，如气阻，蒸发损耗超标准，操作程序复杂，劳动量大，不安全等。为此，设计了气隔式油脂密封下部卸油装置。它是由密封活塞，传动机构和活塞缸组成。密封活塞又和活塞缸共同组成油脂室和空气室。油胆内装满密封油脂，两端由密封密封，空气室则把油品与油脂隔绝开来。该装置与阀门内装满密封油脂，两端由密封圈密封，空气室则把油品与油脂隔绝开来     

Broadband cavity ringdown spectroscopy for sensitive and rapid molecular detection

We demonstrate highly efficient cavity ringdown spectroscopy in which a broad-bandwidth optical frequency comb is coherently coupled to a high-finesse optical cavity that acts as the sample chamber. 125,000 optical comb components, each coupled into a specific longitudinal cavity mode, undergo ringdown decays when the cavity input is shut off. Sensitive intracavity absorption information is simultaneously available across 100 nanometers in the visible and near-infrared spectral regions. Real-time, quantitative measurements were made of the trace presence, the transition strengths and linewidths, and the population redistributions due to collisions and the temperature changes for molecules such as C2H2, O2, H2O, and NH3.     

箱体结构及计算方法对夏玉米农田N2O排放测定结果的影响

为探讨不同箱体结构及计算方法对夏玉米农田N_2O排放测量结果的影响,于2012—2013年在中国农业大学曲周实验站采用静态箱-气相色谱法研究了4个处理在夏玉米季N_2O排放结果,即大箱+直线算法、小箱+直线算法、大箱+曲线并直线算法及小箱+曲线并直线算法。小箱顶部中央留孔使玉米茎能够通过采样箱顶部而不影响玉米生长,大箱在玉米生长到50 cm以后压弯玉米植株。研究表明:在定量夏玉米农田土壤N_2O排放时,与不破坏玉米根系正常生长的小箱测定结果相比,因使用大箱并压弯玉米造成玉米生长不良,不会显著影响N_2O累积排放量的测定结果。在N_2O日排放通量较强时,曲线并直线算法与直线算法得到的结果没有显著差异;而在N_2O日排放通量较弱时,曲线并直线算法测定结果高于直线算法。由于N_2O排放较弱时的通量对夏玉米季农田N_2O累积排放量贡献很小,因此,曲线并直线和直线算法在计算夏玉米季农田N_2O累积排放量时并无显著差异。     

Recent crustal uplift in yellowstone national park

Comparison of precise leveling measurements made in 1923 with those made in 1975, 1976, and 1977 reveals that the 600,000-year-old Yellowstone caldera is being uplifted relative to its surroundings. Maximum relative uplift since 1923 is in excess of 700 millimeters-about 14 millimeters vertically per year. The most likely cause of this rapid and unusually large surface deformation is a recent influx of molten or partially molten materials to a location within the crust beneath Yellowstone National Park.     

用立式多层产孢箱同步生产多株生防真菌孢子粉

利用自主研制的一台立式多层产孢箱作为固相发酵产孢装置，对2株金龟子绿僵菌（Metarhizium anisopliae）、1株金龟子绿僵菌金龟子变种（Manisopliae var．anisopliae）和2株球孢白僵菌（Beauveria bassiana）同时进行了高纯度孢子粉生产的产能试验。每菌株接种6kg大米基质，等量分置于产孢箱的3层中，于25℃下发酵6d。在5株供试菌中，球孢白僵菌Bb2860菌株的产孢量最高，达到2．2×10^12个孢子/kg大米，表现出优异的工艺性状和商品菌剂开发潜力。     

Deformation studies on soufriere, st. Vincent, between 1977 and 1981

Dry-tilt measurements at two stations indicate that Soufriere Volcano gradually inflated at least 10 microradians prior to the initial explosions of April 1979 and then rapidly deflated more than 20 microradians after the activity got under way. The tilt measured at the station 6.5 kilometers from the summit was about twice that measured at a distance of 2.5 kilometers. This finding suggests the existence of a magma chamber at a depth of more than 10 kilometers.     

Stratospheric sulfuric Acid layer: evidence for an anthropogenic component

Recent measurements of small aerosol particles in the stratosphere over Laramie, Wyoming, indicate low-concentration background conditions. A comparison of measurements made some 20 years ago with the present background concentration reveals the possibility of an increase of 9 percent per year. Since the aerosol particles are predominantly sulfuric acid droplets which form in the stratosphere from tropospheric sulfur-containing gases, such an increase may be related to man-made sulfur emissions.     

Evidence for large upward trends of ultraviolet-B radiation linked to ozone depletion

Spectral measurements of ultraviolet-B radiation made at Toronto since 1989 indicate that the intensity of light at wavelengths near 300 nanometers has increased by 35 percent per year in winter and 7 percent per year in summer. The wavelength dependence of these trends indicates that the increase is caused by the downward trend in total ozone that was measured at Toronto during the same period. The trend at wavelengths between 320 and 325 nanometers is essentially zero.