Comment on in vivo corneal confocal microscopic analysis in patients with keratoconus

Dear Editor,The article by Bitirgen et al;published in the journal presents an interesting analysis of keratoconus patients and controls by in vivo corneal confocal microscopy.However,addressing the following observations regarding the study design used by the authors may help add another dimension to the discussion.The age range of the patient group has been stated as 18-41y and for controls as 18-37y.Although the mean age is similar

Analysis of Metallographic Characteristics of Aluminum Alloy for Turbocharged Impellers

In this paper, the composition, two-dimensional and three-dimensional microstructure of heat-resistant wrought aluminum alloy with strong oxidation resistance, heat resistance and easy processing are analyzed by using direct reading spectrometer, metallographic microscope and scanning electron microscope. The main alloy elements of heat-resistant forging aluminum alloy include Cu, Mg, Si, Ni and Fe. The α solid solution of each element in aluminum consists of S phase (Al2CuMg), Mg2Si phase, bright gray Al2CuNi phase and dark brown Al9FeNi phase. The distribution of each phase in the aluminum alloy is determined by the three-dimensional energy spectrum analysis of the microstructure, and the distribution of each phase in the crystal position is analyzed. The mechanism of heat resistance, easy processing type and wear resistance is obtained, which provides the theoretical basis for the development and use of heat-resistant forged aluminum alloy.

The Effect of Graphene Oxide on Mechanical Properties of Cement Mortar

Cement is widely used in engineering applications,but it has both the characteristics of high brittleness and poor bending resistance.In this paper,the effects of different amounts ofgraphene oxide on the flexural strength and compressive strength of cement mortar were studied by doping a certain amount of graphene oxide with cement mortar,and the strengthening mechanism of graphene oxide on cement mortar was obtained through microstructure detection.It is found that graphene oxide has a significant enhancement effect on the macroscopic mechanical properties of cement mortar,and graphene oxide provides nano-nucleation sites and growth templates for cement mortar,accelerates the hydration process,reduces the voids between hydration products,greatly increases the compactness,and improves the macroscopic properties of cement-based materials.

Quantitative XRD Analysis of Cement Clinker by the Multiphase Rietveld Method

Quantitative phase analysis of Portland cement clinker samples was performed using an adaptation of the Rietveld method.The Rietveld quantitative analysis program,originally in Fortran 77 code,was significantly modified in visual basic code with windows 9X graph user interface,which is free from the constraint of direct utilizable memory 640 k,and can be conveniently operated under the windows environment.The Rietveld quantitative method provides numerous advantages over conventional XRD quantitative method,especially in the intensity anomalies and superposition problems.Examples of its use are given with the results from other methods.It is concluded that,at present,the Rietveld method is the most suitable one for quantitative phase analysis of Portland cement clinker.

Analysis of inclusion and purity in steelmaking process

The paper mainly discussed the inclusions and the purity of molten steel and continuous casting slab in tapping,argon-bubbling,LF refining,VD vacuum degassing and continuous casting tundish processes during the steel making.At the same time,the improvement measures of smelting process were indicated. Si-Al-Ba alloy and Ca-Si deoxidation eventually were adopted in 120 t converter.The amount of the tapping was about 135t.After feeding Al wire and adding premelted slag in furnace,picked up the sample after the bottom argon-bubbling which had been done for over 5 minutes.The lime,fluorite,calcium carbide and Al powders were used to produce white slag in LF.Then the alloy compositions were adjusted. Feeding Ca wire after the treatment,and took out over 5 minutes' soft converting.The VD vacuum degassing should be kept for 15 minutes bellow 1.5 torr.After that,Ca wire could be fed.Finally,casting the slab into the size of 260 mm×2 280 mm. The research showed: (1) In converter procedure,the dephosphorization effect turned out good when the ratio of dephosphorization was 88.2%.The final oxygen and nitrogen contents satisfied the demand,and the effects of the final control and bottom-blowing were good. (2) During the LF refining process,the nitrogen seldom added.It showed the excellent sealing effect and the optimization of techniques on operating which had reached the domestic leading level. (3) After the VD vacuum degassing process,the Si,Mn,P,O,N contents were almost steady.The sulphur content kept decreasing to 0.003%and the[H]content was 1.9 ppm.The effect of the vacuum degassing process was good. (4) The oxygen content was controlled at 11 ppm in the continuous casting process,and the nitrogen content had increased to 53ppm with theΔ[N]28 ppm.Therefore,in order to prevent the molten steel from reoxidization,the protection of the continuous casting should be controlled rigorously. (5) The inclusions that existed before the LF refining process were mostly MnO-Al_2O_3-SiO_3 composite inclusions,while the inclusions were mostly calcium-aluminates inclusions after feeding Ca wires to LF or VD furnace.When the Ca/Al had reached to 0.1,7 Al_2O_3 12CaO were produced.The compositions and the sizes of the inclusions in continuous casting slab had changed obviously after the Ca treatment.The sizes were all within 100μm. (6) In order to prepare for the exploitation of the high-quality clean steel,the best process for feeding Ca wire,in LF or VD,and whether it should take one-step wire-feeding way or two-step way as well as the techniques of feeding Ca wire need to be studied further.The desulphurization in LF refining process didn' t reach balance.The ratio of desulphurization could be improved if extending the LF refining time and improving the kinetic condition.

Adsorbability of Mycobacterium phlei on hematite surface

The adsorption of microorganisms on the mineral surface is the base of microorganisms that are considered as mineral processing reagents. The principles of the use of a highly hydrophobic and negatively charged bacterium, Mycobacterium phlei, as a flocculating-flotating agent for finely divided hematite were investigated. The flocculating-floating recovery is strongly dependent on the pH and the dosage of the bacterium. Generally the pH should be controlled over the range of 5.5-7, and the dosage should be controlled about 16 mg/L. The infrared spectrometry analysis indicates that the six functional groups of M. phlei, substituted aromatic compound groups, -（CH2） n-groups, -CH2（-CH3） groups, carbonyl groups, aromatic hydrocarbon groups, and carboxyl groups, are on the hematite surface, among which the first five ones contribute physical adsorption and only the carboxyl groups provide chemisorption. Microscopic analysis reveals that the dimensions and tight aggregation degree of the flocs of hematite particles formed by M. phlei are also impacted by the pH and the content of M. phlei in flotation.

Microstructure and Strain Fatigue Dislocation Structure of 7075-RRA Aluminum Alloy

The microstructure and the strain fatigue dislocation substructure of 7075-RRA (Retrogression and Reaging) aluminum alloy have been studied by using transmission electron microscopy. From these, a competitive mechanism of cyclic microscopic softening/hardening is put forward to explain the relation between macroscopic cyclic stability behavior and microscopic substructure.

Research on the intermediate phase of 40CrMnSiB steel shell under different heat treatments

In this study, 40 Cr Mn Si B steel cylindrical shells were tempered at 350, 500 and 600 ℃ to study the effect of tempering temperature on the dynamic process of expansion and fracture of the metal shell. A midexplosion recovery experiment for the metal cylinder under internal explosive loading was designed, and the wreckage of the casings at the intermediate phase was obtained. The effects of different tempering temperatures on the macroscopic and microscopic fracture characteristics of 40 Cr Mn Si B steel were studied. The influence of tempering temperatures on the fracture characteristic parameters of the recovered wreckage were measured and analyzed, including the circumferential divide size, the thickness and the number of the circumferential divisions. The results show that as the tempering temperature was increased from 350 to 600 ℃, at first, the degree of fragmentation and the fracture characteristic parameters of the recovered wreckage changed significantly and then became essentially consistent. Scanning electron microscopy analysis revealed flow-like structure characteristics caused by adiabatic shear on different fracture surfaces. At the detonation initiation end of the casing, fracturing was formed by tearing along the crack, which existed a distance from the initiation end and propagated along the axis direction. In contrast, the fracturing near the middle position consists of a plurality of radial shear fracture units. The amount of alloy carbide that was precipitated during the tempering process increased continuously with tempering temperature, leading to an increasing number of spherical carbide particles scattered around the fracture surface.

Thermal Insulation and Strength of Autoclaved Light Concrete

The primary objective of this study was to develop an autoclaved light concrete （ALC） material with ultra-thermal insulation property and to investigate the relationship between its physical characteristics and mechanical properties. Through tests of dry bulk density and compressive strength, relationship of physical characteristics and mechanical properties of samples were studied, resulting in a material with ultra-thermal insulation property. Scanning electron microscope （SEM） and energy-dispersive X-ray spectroscopy （EDX） were applied to analyze the micro-morphology and elemental composition of samples. To identify the product phases, X-ray diffraction （XRD） was engaged. The test results showed that compressive strength and thermal coefficient were reduced with the increasing of aluminum powder within the mixtures. As a result the optimal thermal coefficient and compressive strength of samples were improved to 0.061 W/（m·k） and 1.2 MPa, respectively. SEM, EDX and XRD analyses showed that calcium silicate hydrate and tobermorite crystal were main resultant phases.

Nano-silver induced ceramic coloring via control of glaze interface and phase separation

As a kind of rare materials,nano-silver has broad application prospects in the fields of catalysis,medical treatment,new energy and so on.However,there are few reports on the systematic research of nano-silver in ceramic glazes.In this work,different color ceramic glazes were produced by tuning the nano-silver content and optimizing the firing process.The crystalline phase composition,micro-morphology and elemental distribution of fired glazes were analyzed and discussed in depth.The elemental composition and distribution of the samples were studied.The surface of the glazes with varying Ag contents fired under the reducing atmosphere exhibited blue-white.And the blue color is attributable to Rayleigh scattering that may arise because the phase-separation structures existed in glazes.Interestingly,the color of the ceramic glazes with varying Ag contents changed to golden-yellow when the ceramic glazes were fired under the air atmosphere.Golden-yellow color of the samples fired under the air atmosphere is mainly attributable to the silver nanoparticles,though Ag^(+) may be existed in the glazes.