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Much of the fertiliser nitrogen (N) used in agriculture is lost to the atmosphere as nitric oxide and nitrogen dioxide (collectively referred to as N[O.sub.x]), ammonia (N[H.sub.3]), and nitrous oxide ([N.sub.2]O). The lost N is not only an economic problem for the farmer; it also contaminates the environment and affects human health. Because the values obtained for N[O.sub.x] and N[H.sub.3] loss to the atmosphere from agriculture in Monsoon Asia have been questioned, we quantitatively determined, using new techniques, the emission of these gases from a maize crop fertilised with urea in northern China. The fertiliser was deep-placed by traditional farmers' practice and emissions of N[O.sub.x] and N[H.sub.3] were determined with a chemiluminescence analyser and a backward Lagrangian stochastic dispersion technique. The emission measurements indicate that 1.2% of the applied N was lost as N[O.sub.x]. This loss is far greater than measured or derived by other researchers, and we suggest that this is because our measurements were made continuously rather than as spot measurements with static chambers. The results for N[H.sub.3] show that, although the fertiliser was placed below the soil surface, a small amount (7% of the applied N) was still lost to the atmosphere. Soil analyses indicate that the rate of nitrification in this soil was low, and the maximum nitrate (N[O.sub.3.sup.-]) concentration found in the soil (31.4 µg N/g) was only 3.9% of the fertiliser N added. Thus, there is little potential for N[O.sub.3.sup.-] to be leached down the profile. A study using soil cores and acetylene inhibition to measure denitrifying activity suggested that the rate of denitrification in this soil was also very low. The results suggest that in this soil with slow nitrification and denitrification rates and little potential for leaching, deep placement of the urea to limit N[H.sub.3] volatilisation is an effective method for increasing fertiliser use efficiency. Additional keywords: bLs method, deep placement, fertiliser, micrometeorological techniques., Introduction Agriculture in China is highly intensive and, with the aid of new technology and high input of fertiliser, is very productive and meets the demands by the rapidly increasing [...]

Enhanced hot carrier degradation in nMOSFETs with a forward substrate bias is investigated and reported.

InGaAs/GaAs (111)B quantum well p-i-n structures grown through gas source molecular beam epitaxy were studied through photoreflectance spectroscopy. The built-in electric field was determined from the above band-gap Franz-Keldysh oscillations (FKOs) by employing the reduced mass deduced from experiments. The strain-induced piezoelectric field was then obtained directly from the comparison of the periods of FKOs in various samples.

The calculated and measured majority carrier mobility in both n-type and p-type Hg0.78Cd0.22Te liquid phase epitaxy (LPE) films at 77 k over a wide range of carrier concentration were compared. 190 n-type LPE films, which were indium doped, and 360 p-type LPE films were subjected to Hall measurements. It was found that polar optical phonon, ionized impurity and alloy disorder scatterings dominate the scattering mechanisms of both LPE film types.

Minority-carrier lifetime in n-type indium-doped Hg0.78Cd0.22Te liquid-phase-epitaxial thin films was investigated. The results showed that Auger recombination with a value of 0.15 dominated minority-carrier lifetimes at temperatures above 130 K. In addition, the inclusion of Shockley-Read-Hall recombination was necessary to fit the lifetimes at temperatures lower than 120K.

[Fe.sub.1-x][Co.sub.x][O.sub.y] (O [less than or equal to] x [less than or equal to] 1,1 [less than or equal to] y [less than or equal to] 4/3) mixture oxide films are grown, with epitaxial quality, on MgO(001) substrates by molecular beam epitaxy. The X-ray diffraction result along (001) plane is similar to [Fe.sub.3][O.sub.4] for the films with x < 0.5 (Fe rich) and is similar to CoO for the films with x > 0.5 (Co rich). An abrupt change, over 2%, on the lattice spacing is observed around Fe/Co ~ 1(x = 0.5) suggesting a phase transformation from spinel to rocksalt. A fast suppression of the saturation magnetization is found markedly different from the bulk materials as the Co ratio increases. Crystalline anisotropy and anomalous magnetic properties are affected substantially by Co ions. These unique magnetic behaviors of Fe-Co-O films are believed to be related to cation distribution in spinel structure originated by the low-temperature process of thin-film fabrication. Index Terms--Ferrite films, magnetic anisotropy, magnetic epitaxial layers.

The above-barrier states in AlGaAs-GaAs superlattices at room temperature have been investigated. The results of photoconductivity and photoreflectance measurements showed the existence of free-carrier confinement at barrier layers. It was also shown that modified Messiah's calculation can be used to describe the barrier-width dependence of the above-barrier transition energies.

The photoconductivity (PC) in self-organized InAs/GaAs quantum dots is studied. It is shown that PC due to optical transitions are caused by the thermal excitation of photocarriers in the dots into the GaAs matrix. The effects of persistent photoconductivity (PPC) are also observed in self-organized InAs. A model based on the spatial separation of photocreated electrons and holes is developed to analyze the PPC effect.

A study was conducted on n+ -p diodes produced on p-type bulk Hg0.78Cd0.22Te with high dislocation density. The study's aim was to confirm the association of deep levels with narrow band gaps existing in HgCdTe. Deep level transient spectroscopy was used in the study. A deep level approximately 80 meV above the valence band was observed in samples with normal dislocation densities while a midgap level of around 60 meV above the valence band was observed in samples with high dislocation densities.

A method for determining the conductivity type of narrow band-gap HgCdTe materials was presented. The method was based on semiconductor thermoelectrical effects and generated a temperature gradient across the sampleby partly immersing it in liquid nitrogen. Two spring contacts were probes wereloaded on two separate locations on the sample to measure the induced Seebeck voltage. The results showed that Hall measurements had a greater influence on thermoelectric measurements than inverted surface effects