“镜子”与“探照灯”辨析——对新闻传播学中反映论与建构论的认识思考

新闻或新闻媒介是“镜子”还是“探照灯” ,学者们各有不同的看法。本文从认识论的角度来对“镜子 /反映论”和“探照灯 /建构论”这两种基本的思维模型进行深刻的学理追问 ,目的在于 :检视“镜子 /反映论”和“探照灯 /建构论”对于“新闻传播学”

Micro-galvanic corrosion behaviour of Mg-(7,9)Al-1Fe-xNd alloys

The localized micro-galvanic corrosion process and the kinetic information of Mg-(7,9)Al-1Fe-x Nd alloys were investigated by in situ observation under electrochemical control and in situ atomic force microscopy(AFM)in an electrolyte environment.The results revealed that the formation of the Nd-rich phase in alloys resulted in a decrease in the Volta potential difference from~400 m V(AlFe3/α-Mg)to~220 mV(Nd-rich/α-Mg),reducing the corrosion products around the cathodic phase and corrosion current density of the microscale area.The addition of Nd significantly improved the corrosion resistance,mainly due to the suppression of the micro-galvanic corrosion between the second phases and substrate.Finally,the corrosion mechanism of Mg-(7,9)Al-1Fe-x Nd alloys was discussed based on in situ observations and electrochemical results.

Development of advanced electron tomography in materials science based on TEM and STEM

The recent developments of electron tomography（ET） based on transmission electron microscopy（TEM） and scanning transmission electron microscopy（STEM） in the field of materials science were introduced. The various types of ET based on TEM as well as STEM were described in detail, which included bright-field（BF）-TEM tomography, dark-field（DF）-TEM tomography, weak-beam dark-field（WBDF）-TEM tomography, annular dark-field（ADF）-TEM tomography, energy-filtered transmission electron microscopy（EFTEM） tomography, high-angle annular dark-field（HAADF）-STEM tomography, ADF-STEM tomography, incoherent bright field（IBF）-STEM tomography, electron energy loss spectroscopy（EELS）-STEM tomography and X-ray energy dispersive spectrometry（XEDS）-STEM tomography, and so on. The optimized tilt series such as dual-axis tilt tomography, on-axis tilt tomography, conical tilt tomography and equally-sloped tomography（EST） were reported. The advanced reconstruction algorithms, such as discrete algebraic reconstruction technique（DART）, compressed sensing（CS） algorithm and EST were overviewed. At last, the development tendency of ET in materials science was presented.

Colonization Pattern of Azospirillum brasilense Yu62 on Maize Roots

Plasmid pVK1001 which carried the gfp gene of GFPmut2, a mutant of GFP, was introduced into Azospirillum brasilense Yu62 by electroporation. Maize seedlings were inoculated with the GFP-labelled baeteria and grown gnotobiotically in flask with semi-solid agar medium. Observations were performed with confocal laser scanning microscopy (CLSM) and electron microscopy, respectively, at 8 d and 12 d after inoculation. Confocal laser scanning microscopy showed that A. brasilense Yu62 could penetrate into the cortex tissue, colonizing in the intercellular spaces of the parenchyma cells of the cortex tissue. Transmission and scanning electron microscopy (TEM) showed that the majority of the bacteria colonized on the root surface and only a minority of them resided in the root interior.

Comparative Study on Morphological Characteristics of Ova from Two Species in Noctuidae

[Objective] The aim was to explore the morphological characteristics of ovum from Spodoptera exigua and Heliothis assulta.[Method]The ultra morphological characteristics of ovum was observed with scanning electron microscope（SEM）.[Result]The ova from S.exigua and H.assulta are all spheroid,the former has net line decoration on surface,with some aeropyle distributed on the net line decoration;the micropyle is located in the center of polar and has plum flower-like engraving;the surface of chorion of the latter has the parallel crowns through two polar.Between the parallel crown,the surface of chorion has the decorated trapezium line,all crowns of second polar zone have breast-tuber that distributes in parallel at the same latitude in line,and there is no aeropyle distributing on chorion.[Conclusion] The ultra morphological characteristics of the ova from two Noctuidae species showed significant difference to each other,which enriched ontogenesis data and also provided reference for the accurate identification of two kinds of ova.

Observation and characterization of asphalt microstructure by atomic force microscopy

The microstructure of asphalt is investigated by atomic force microscopy （AFM）. In order to analyze the impacts of asphalt types on microstructures, two neat asphalts with different penetration grades （50# and 70#） and one styrene-butadiene-styrene （SBS） modified asphalt are chosen. The influence of short-term aging is also studied. Based on the knowledge of asphalt＇s microproperties, the relationship between microstructures and healing property is analyzed. The results indicate that the microstructures of three asphalts are quite different and the effects of aging on the surface characteristics for different asphalts are also different. It is proposed that the bee structure is a type of wax crystal and it has a close relationship with the ＂bridge-healing＂ mechanism. The findings may reveal the formation mechanism of microstructure and the healing property for asphalts.

Synthesis and Characterization of GaN Nanorods by Ammoniating Ga_2O_3 /Co Films Deposited on Si(111) Substrates

GaN nanorods are successfully synthesized on Si（111） substrates with magnetron sputtering through ammoniating Ga2O3/Co films at 950℃. X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy,and Fourier-transform infrared spectroscopy are used to characterize the samples. The results demonstrate that the nanorods are single-crystal GaN with a hexagonal wurtzite structure and possess relatively smooth surfaces. The growth mechanism of GaN nanorods is also discussed.

Interaction Study between DNA and Histone Proteins on Single-molecule Level using Atomic Force Microscopy

DNA and histone protein are important in the formation of nucleosomal arrays, which are the first packaging level of DNA into a more compact chromatin structure. To characterize the interactions of DNA and histone proteins, we reconstitute nucleosomes using lambda DNA and whole histone proteins by dialysis and perform direct atomic force microscopy （AFM） imaging. Compared with non-specific DNA and histone binding, nucleosomes are formed within the assembled “beads-on-a-string” nucleosomal array by dialysis. These observations facilitate the establishment of the molecular mechanisms of nucleosome and demonstrate the capability of AFM for protein-DNA interaction analysis.

Evolution of Self-Organized Ge Quantum Dots During Ultra High Vacuum Annealing

The evolution of self organized Ge quantum dots structure is investigated by scanning tunneling microscopy and atomic force microscopy during annealing treatment up to 700℃ in an ultra high vacuum(UHV) system.When the sample temperature rises to 630℃,a great amount of new dots emerge on the wetting layer,which are believed to be incoherent islands compared with the dislocation free coherent islands formed during molecular beam epitaxy growth.

Analysis of PTCDA/ITO Surface and Interface Using X-ray Photoelectron Spectroscopy and Atomic Force Microscopy

The electronic states of the surface and interface of 3,4, 9, 10-perylenetetracarboxylic dianhydride （PTCDA）/indium-tin-oxide （ITO） thin film are investigated using X-ray photoelectron spectroscopy （XPS）. A- tomic force microscopy （AFM） is also applied to investigate the pattern of PTCDA/ITO film. XPS results show that there are two main peaks,which are associated with C atoms in the perylene rings and acid anhydride groups, located at 284.6 and 288.7eV, respectively,in the Cls spectrum of the original surface. It can be deduced from the emergence of a small peak at 290.4eV in the Cls spectrum that some C atoms are oxidized by O atoms from ITO. The binding energies of O atoms in C-O bonds and C--O---C bonds are 531.5 and 533.4eV respectively. At the interface,the peak at the high binding energy in the Cls spectrum disappears,and the peak value shifts about 0.2eV to lower binding energy, There is a significant 1.5eV chemical shift to lower binding energy in the Ols spectrum. These observations indicate that perylene rings inside PTCDA molecules are combined with In vacancies in the ITO at the interface. The AFM results show that PTCDA molecules formed an island-like structure a height of about 14nm. The sizes of the crystal grains are about 100--300nm. The island-like pattern comes from the delocalized π bonds of adjacent molecules in PTCDA and the combination of vacancies in ITO with perylene rings at the PTCDA/ITO interface.

Deformation defects and electron irradiation effect in nanostructured Al-Mg alloy processed by severe plastic deformation

In order to explore the exact nature of deformation defects previously observed in nanostructured Al-Mg alloys subjected to severe plastic deformation, a more thorough examination of the radiation effect on the formation of the planar defects in the high pressure torsion （HPT） alloys was conducted using high-resolution transmission electron microscopy （HRTEM）. The results show that high density defects in the HRTEM images disappear completely when these images are exposed under the electron beam for some duration of time. At the same time, lattice defects are never observed within no-defect areas even when the beam-exposure increases to the degree that holes appear in the areas. Therefore, it is confirmed that the planar defects observed in the HPT alloys mainly result from the significant plastic deformation and are not due to the radiation effect during HRTEM observation.

Obsevation for Epidermal Ultrastructure of Nostoc sphaeroides Kutzing under Scanning Electron Microscope

[Objective]The experiment aimed to explore a new way for observing surface structure of Nostoc sphaeroides Kutzing. [Method] The scanning electron microscope was used to observe the epidermal ultrastructure of wild and cultured Nostoc sphaeroides Kutzing. [ Result] The epidermis of wild and cultured Nostoc sphaeroides Kutzing showed mixture structure of fibril colloid which was reticular arranged. The difference between wild and cultured Nostoc sphaeroides Kutzing was that the outer epidermis of cultured Nostoc sphaeroides Kutzing had trichome distribution but the wild Nostoc sphaeroides Kutzing did not has such distribution. The obsevation results of under smaller than 10 μm by scanning electron microscope was touched thick and showed many folds and distortions. [ Conclusion] The scanning electron microscope was an effective way to study development of Nostoc sphaeroides Kutzing colony and it was worth popularizing.

TEM STUDY ON MICROSTRUCTURAL DEVELOPMENT OF SINGLE-AGEING 7055 ALUMINUM ALLOYS

Mierostruetural development of a commercial 7055 （Al-Zn-Mg-Cu）alloy is studied by transmission electron mieroseope（TEM） during the process of single-ageing for up to 48 h. It is observed that Guinier-Preston （GP） zones are formed on { 111} planes when the sample is aged for a short time and grows up gradually with increase of ageing time. η＇ phase is formsed after ageing for 4 h at 120℃, having the orientation relationship with the matrix as[0 0 0 1]η＇//[1 1^- 1]Al and （1 0 1^- 1）η＇//（1 1 0）Al.η phase starts to occur after 24 h ageing and has an orientation relationship with matrix as [1^- 1 0 0]η//[1 1 0]Al and （0 0 0 1）η// （1 1 1）Al. Since the density of both η＇ phase and η phase particles is much lower than that of GP zone on aged alloy, GP zones are important to control the properties of the alloy.

AFM Observation of GaN Grown on Different Substrates at Low Temperatures

Aim To study the relationship between the substrate temperature and the morphology and properties of GaN. Methods\ Applying the hydride chemical vapor deposition method, GaN films were deposited on different kinds of substrates, including sapphire, Si(111),Si(100),GaAs and GaP(111) both on the P face and the Ga face. The growth was performed at low temperatures of below 700℃. XRD, Hall measurement, cathodoluminescence (CL) and atomic force microscopy (AFM) were used to characterise the film properties. Results\ It was found that the temperature and the nature of substrate materials influence the layer morphology. Conclusion\ The analysis shows that no apparent relationship exists between the optical properties and layer morphology.

Optimization of InGaAs Quantum Dots for Optoelectronic Applications

Self-assembled In 0.35Ga 0.65As/GaAs quantum dots with low indium content are grown under different growth temperature and investigated using contact atomic force microscopy(AFM).In order to obtain high density and high uniformity of quantum dots,optimized conditions are concluded for MBE growth.Optimized growth conditions also compared with these of InAs/GaAs quantum dots.This will be very useful for InGaAs/GaAs QDs optoelectronic applications,such as quantum dots lasers and quantum dots infrared photodetectors.

RESEARCH ON MEMBRANE BIOREACTOR TREATING DOMESTIC WASTEWATER AND RELATED MECHANISMS

Experiments on treatment of domestic wastewater by membrane bioreactors were carried out.The results showed that this process could produce good quality effluent with low COD,turbidity and total count of bacteria.With intermittent operation and continuous aeration,the membrane flux was kept steady.The mechanisms of removing COD through membrane,the structure of membrane and filtration resistance were also discussed.

MECHANISM OF MICROBAND FORMATION IN COLD ROLLED INTERSTITIAL-FREE STEEL

The mechanism of the shear band formation in the high cold rolled BCC metal is analyzed. Based on the plastic deformation theory, the shear distribution in the deformed grain is calculated by using the Taylor constraint model and the Bishop ＆ Hill maximum work principle. Results show that when the rolling direction （RD） is parallel to a certain direction of a grain, the large localized shear occurs on one slip plane, thus generating microbands in the grain because of the high localized shear strain. The angle between the RD and the shear band is about 30°. The plate-like structure of the microband is formed because of the dislocation double cross slip. The transmission electron microscope （TEM） observation of the microband in the cold rolled BCC metal confirms the formation mechanism of the microband.

Experimental Research of DLC Film Deposited by Filtered Vacuum Arc Evaporation

Diamond like carbon (DLC) films was grown successfully on silicon, titanium and high speed steel (HSS) substrate at low temperature in a filtered vacuum arc deposition system. Arc discharges were established on a graphite cathode in this home built system with a toridal macroparticles filter. Ion current convected by the plasma beam was measured with a negatively biased probe. It was shown that the magnetic field of the coils located on the plasma duct has a strong influence on ion current. Scanning electron microscope (SEM), atomic force microscope (AFM) and Raman spectrum are used to study the DLC films. Tribological behaviors of the deposited film are also studied.

Observation and Comparision on Morphological Characteristics of the Seed-like Fruits of Salvia shandongensis and Its Relatives

[Objective] This study aimed to compare and analyse the morphological characteristics of the seed-like fruits between Salvia shandongensis J. X. Li et F. Q. Zhou and its relatives. [Method] The morphological characteristics of the mature seed-like fruits of Salvia shandongensis and its three congeners, S. miltiorrhiza, S. miltiorrhiza f. alba and S. bowleyana, were comparatively observed using both optical microscope and scanning electron microscope. [Result] The results showed that there were distinct differences in the shape, size and exine sculpture of the seed-like fruits of the four Danshen congeners： the seed-like fruits of S. shandongensis that were elliptical and had areolate sculpture with subquadrangular convex meshes as well as densely filamentous transverse lines were easy to be distinguished from those of S. miltiorrhiza Bge., which were broadly elliptical and had reticulate sculpture with subquadrate concave meshes. The seed-like fruits of S. bowleyana were fusiform and their ektexine had reticulate sculpture with polygonal meshes, which were slightly convex at the center, which are obviously different from those of S. shandongensis. [Conclusion] This study first accumulates data of the seed-like fruits of S. shandongensis, which provides important bases for establishing its taxonomical status and studying its germplasm. The morphological characteristics and reticulate sculpture on ektexine of the seed-like fruits S. miltiorrhiza Bge. are consistent with the previous report. The results in this study not only provide references for uncovering the genetic relationships between S. shandongensis and S. miltiorrhiza Bge., as well as the interspecific classification and identification. In addition, this study also provides new scientific proofs for the identification of Danshen species and their introduction and cultivation, genetics and breeding.

Observation and Comparison of Pollen Submicroscopic Morphology of Seven Mulberry(Morus alba Linn.) Cultivars

[Objective] This study aimed to investigate the submicroscopic structure and morphological characteristics of mulberry pollen. [Method] Mulberry pollen of seven cultivars were treated by glutaraldehyde fixing, alcohol gradient dehydration, freeze-drying and metal plating to observe the size and surface ornamentation under the scanning electron microscope （SEM）. [Result] The pollen surface characteristics and ornamentation were clearly visible, indicating that this method is suitable for SEM observation of mulberry pollen; experimental mulberry pollen was nearly spher- ical, with two germination apertures and processes on aperture membrane; polar axis was 15.99-22.63 μm long, and equatorial axis was 14.98-20.78 μm long; the pollen volume of ＂Yu No.2＇ was the maximum, while that of ＂Jinxuan No.7＇ was the minimum; the surface of mulberry pollen showed smooth and tumor-like protuberance ornamentations, covered with different densities of particles. [Conclusion] Glutaralde- hyde fixative-alcohol gradient dehydration is an ideal method for morphological char- acteristics of mulberry pollen. This study may provide useful information for palynology identification of Morus plants or even species-level systematic classification.