Use of near-infrared reflectance spectroscopy for the rapid determination of the digestible energy and metabolizable energy content of corn fed to growing pigs

Background： The ability of near-infrared reflectance spectroscopy（NIRS） to determine the digestible energy（DE）and metabolizable energy（ME） content of corn fed to growing pigs was tested. One hundred and seventeen corn samples, comprising different planting regions and varieties were collected from all over China in a three-year period. The samples were randomly split into a calibration set（n = 88） and a validation set（n = 29）. The actual and calculated DE and ME content of the corn samples was determined by digestion-metabolism experiments and the prediction equations of Noblet and Perez（J Anim Sci. 71：3389–98,1993）. The samples were then subjected to NIRS scanning and calibrations were performed by the modified partial least square（MPLS） regression method based on77 different spectral pre-treatments. The NIRS equations based on the actually determined and calculated DE and ME were built separately and then validated using validation samples.Results： The NIRS equations obtained from actually determined DE, the coefficient of determination for calibration（RSQcal）, cross-validation（R^2CV）, and validation（RSQv） were 0.89, 0.87 and 0.86, and these values for determined ME were 0.87, 0.86 and 0.86. For the NIRS equations built from calculated DE, the RSQcal, R^2CV, and RSQvvalues were 0.88, 0.85 and 0.84, and these values for calculated ME were 0.86, 0.84 and 0.82. Except for the equation based on calculated ME（RPD_v= 2.38, 〈 2.50）, the other three equations built from actually determined energy and calculated DE produced good prediction performance（RPD_vranging from 2.53 to 2.69, 〉 2.50） when applied to validation samples.Conclusion： These results indicate that NIRS can be used as a quantitative method for the rapid determination of the available energy in corn fed to growing pigs, and the NIRS equations based on the actually determined energy produced better predictive performance than those built from calculated energy values.

ENERGY-LOSS FUNCTIONS DERIVED FROM REELS SPECTRA FOR ALUMINUM

The effective energy loss functions for Al have been derived from differential i nverse inelastic mean free path based on the extended Landau approach. It has be en revealed that the effective energy loss function is very close in value to th e theoretical surface energy loss function in the lower energy loss region but g radually approaches the theoretical bulk energy loss function in the higher ener gy loss region. Moreover, the intensity corresponding to surface excitation in e ffective energy loss functions decreases with the increase of primary electron e nergy. These facts show that the present effective energy loss function describe s not only surface excitation but also bulk excitation. At last, REELS spectra s imulated by Monte Carlo method based on use of the effective energy loss functio ns has reproduced the experimental REELS spectra with considerable success.

Cubic ZnO films obtained at low pressure by molecular beam epitaxy

A zinc oxide thin film in cubic crystalline phase, which is usually prepared under high pressure, has been grown on the Mg O（001） substrate by a three-step growth using plasma-assisted molecular beam epitaxy. The cubic structure is confirmed by in-situ reflection high energy electron diffraction measurements and simulations. The x-ray photoelectron spectroscopy reveals that the outer-layer surface of the film（less than 5 nm thick） is of ZnO phase while the buffer layer above the substrate is of ZnMgO phase, which is further confirmed by the band edge transmissions at the wavelengths of about 390 nm and 280 nm, respectively. The x-ray diffraction exhibits no peaks related to wurtzite ZnO phase in the film. The cubic ZnO film is presumably considered to be of the rock-salt phase. This work suggests that the metastable cubic ZnO films, which are of applicational interest for p-type doping, can be epitaxially grown on the rock-salt substrates without the usually needed high pressure conditions.

Effect of thickness on the microstructure of GaN films on Al_2 O_3 (0001) by laser molecular beam epitaxy

Heteroepitaxial GaN films are grown on sapphire （0001） substrates using laser molecular beam epitaxy. The growth processes are in-situ monitored by reflection high energy electron diffraction. It is revealed that the growth mode of GaN transformed from three-dimensional （3D） island mode to two-dimensional （2D） layer-by-layer mode with the increase of thickness. This paper investigates the interfacial strain relaxation of GaN films by analysing their diffraction patterns. Calculation shows that the strain is completely relaxed when the thickness reaches 15 nm. The surface morphology evolution indicates that island merging and reduction of the island-edge barrier provide an effective way to make GaN films follow a 2D layer-by-layer growth mode. The ll0-nm GaN films with a 2D growth mode have smooth regular hexagonal shapes. The X-ray diffraction indicates that thickness has a significant effect on the crystallized quality of GaN thin films.

Design of a novel correlative reflection electron microscope for in-situ real-time chemical analysis

A novel instrument that integrates reflection high energy electron diffraction(RHEED),electron energy loss spectroscopy(EELS),and imaging is designed and simulated.Since it can correlate the structural,elemental,and spatial information of the same surface region via the simultaneously acquired patterns of RHEED,EELS,and energy-filtered electron microscopy,it is named correlative reflection electron microscopy(c-REM).Our simulation demonstrates that the spatial resolution of this c-REM is lower than 50 nm,which meets the requirements for in-situ monitoring the structural and chemical evolution of surface in advanced material.