Optimal cutting condition determination for milling thin-walled details

This paper presents an approach for determining the optimal cutting condition for milling thin-walled elements with complex shapes. The approach is based on the interaction between the thin-walled detail and its periodic excitation by tooth passing, taking into account the high intermittency of such a process. The influence of the excitation frequency on the amplitude of the detail oscillation during milling was determined by simulation and experiments. It was found that the analytical results agreed with experimental data. The position of the detail when the tooth starts to cut was evaluated through experiments. The influence of this parameter on the processing state is presented herein. The processing stability is investigated and compared with the proposed approach. Thereafter, spectral analyses are conducted to determine the contribution of the vibrating frequencies to the detail behavior during processing.The full text can be downloaded at https://link.springer.com/content/pdf/10.1007%2Fs40436-018-0224-y.pdf     

Photoelectron spectra of Yb-Si(100) heterointerfaces formed at room temperature

The laws of formation of the heterointerfaces formed upon ytterbium (Yb) deposition at room temperature (T=300 K) onto a (2×1)-reconstructed Si(100) surface were studied by methods of photoelectron spectroscopy (PES) with excitation by synchrotron radiation and low-energy electron diffraction (LEED). In the range of submonolayer surface coverages θ, the adsorption of Yb atoms leads to destruction of the surface dimers. This is accompanied by the formation of an amorphous film consisting of mixed Yb and Si atoms. For θ>1.5, a partly ordered metallic ytterbium film containing dissolved Si atoms is formed on the substrate surface. In all stages of deposition, there is charge transfer from Yb to Si atoms, which is manifested by a shift of the Si 2p core level. This shift is especially pronounced (reaching 1.5 eV) for silicon atoms dissolved in the metallic film.     

Assessment of cellular oxygen gradients with a panel of phosphorescent oxygen-sensitive probes

The supply of oxygen (O(2)) to respiring tissue, cells, and mitochondria regulates metabolism, gene expression, and cell fate. Depending on the cell type and mitochondrial function, O(2) gradients between extra- and intracellular compartments may vary and play important physiological roles such as the regulation of activity of prolyl hydroxylases and adaptive responses to hypoxia. Here we present a new methodology for the analysis of localized O(2) gradients in cultures of adherent cells, using three phosphorescent Pt-porphyrin based probes with different localization. One new O(2) probe targeted to the cell membrane was developed and used together with existing MitoXpress and Nano2 probes to monitor mean pericellular (PC), extracellular (EC), and intracellular (IC) O(2) concentrations, respectively. Mouse fibroblasts and neuronal PC12 cells cultured in standard microplates were stained with probes and measured on a commercial time-resolved fluorescence reader in phosphorescence lifetime mode. Respiring cells exposed to various levels of atmospheric O(2) showed differences in oxygenation of their IC, PC, and EC compartments. Experiments with different cell numbers and modulation of respiration activity demonstrated that these gradients are dynamic and regulated by the O(2) diffusion and consumption rate. The new method facilitates the assessment of such gradients.     

A comprehensive analysis of the CVD growth of boron nitride nanotubes

Boron nitride nanotube (BNNT) films were grown on silicon/silicon dioxide (Si/SiO(2)) substrates by a catalytic chemical vapor deposition (CVD) method in a horizontal electric furnace. The effects of growth temperature and catalyst concentration on the morphology of the films and the structure of individual BNNTs were systematically investigated. The BNNT films grown at 1200 and 1300?°C consisted of a homogeneous dispersion of separate tubes in random directions with average outer diameters of ~30 and ~60 nm, respectively. Meanwhile, the films grown at 1400?°C comprised of BNNT bundles in a flower-like morphology, which included thick tubes with average diameters of ~100 nm surrounded by very thin ones with diameters down to ~10 nm. In addition, low catalyst concentration led to the formation of BNNT films composed of entangled curly tubes, while high catalyst content resulted in very thick tubes with diameters up to ~350 nm in a semierect flower-like morphology. Extensive transmission electron microscopy (TEM) investigations revealed the diameter-dependent growth mechanisms for BNNTs; namely, thin and thick tubes with closed ends grew by base-growth and tip-growth mechanisms, respectively. However, high catalyst concentration motivated the formation of filled-with-catalyst BNNTs, which grew open-ended with a base-growth mechanism.     

General intracavity method for laser transition characterization byrelaxation oscillations spectral analysis

Monitoring the transient buildup of laser emission is proposed as a simple method for spectro-temporal intracavity diagnostics of laser transitions and materials. Using this method, we determined the absolute magnitude of both laser emission and absorption cross sections for a line-narrowed tunable Er³⁺-fiber laser     

Targeted tumor cell internalization and imaging of multifunctional quantum dot-conjugated immunoliposomes in vitro and in vivo

Targeted drug delivery systems that combine imaging and therapeutic modalities in a single macromolecular construct may offer advantages in the development and application of nanomedicines. To incorporate the unique optical properties of luminescent quantum dots (QDs) into immunoliposomes for cancer diagnosis and treatment, we describe the synthesis, biophysical characterization, tumor cell-selective internalization, and anticancer drug delivery of QD-conjugated immunoliposome-based nanoparticles (QD-ILs). Pharmacokinetic properties and in vivo imaging capability of QD-ILs were also investigated. Freeze-fracture electron microscopy was used to visualize naked QDs, liposome controls, nontargeted QD-conjugated liposomes (QD-Ls), and QD-ILs. QD-ILs prepared by insertion of anti-HER2 scFv exhibited efficient receptor-mediated endocytosis in HER2-overexpressing SK-BR-3 and MCF-7/HER2 cells but not in control MCF-7 cells as analyzed by flow cytometry and confocal microscopy. In contrast, nontargeted QD-Ls showed minimal binding and uptake in these cells. Doxorubicin-loaded QD-ILs showed efficient anticancer activity, while no cytotoxicity was observed for QD-ILs without chemotherapeutic payload. In athymic mice, QD-ILs significantly prolonged circulation of QDs, exhibiting a plasma terminal half-life ( t 1/2) of approximately 2.9 h as compared to free QDs with t 1/2 < 10 min. In MCF-7/HER2 xenograft models, localization of QD-ILs at tumor sites was confirmed by in vivo fluorescence imaging.     

Migration of specific planar grain boundaries in bicrystals: application of magnetic fields and mechanical stresses

Recent research on the dynamics of planar grain boundaries is reviewed. Novel measuring techniques developed for in situ observation and recording of magnetically and stress driven grain boundary migration are presented. The results of migration measurements obtained on bismuth, zinc and aluminum bicrystals are addressed. The experiments revealed that the inclination of a 〈112〉 tilt boundary in Bi has a very strong influence on its mobility. The migration of planar 〈10$ \bar 1 $ \bar 1 0〉 tilt grain boundaries with different misorientation angles was measured in situ in bicrystals of high purity zinc. The results proved that there is a pronounced misorientation dependence of grain boundary mobility in the investigated angular range. The shear stress induced migration of planar symmetric 〈100〉 tilt boundaries in aluminum bicrystals was observed to be accompanied by a lateral translation of the adjacent grains. The coupling between boundary motion and shearing is not confined to low angle and some low Σ high angle boundaries, but occurs also for noncoincidence high angle 〈100〉 tilt boundaries. It has been found that also for stress induced grain boundary motion there is a misorientation dependence of the migration activation parameters. Lower values of the activation enthalpy and the pre-exponential mobility factor can be associated with boundaries with tilt angles close to low Σ CSL orientation relationships.     

Development of novel metallic glass/polymer composite materials by microwave heating in a separated H-field

Using a single mode 915 MHz applicator, we fabricate novel Cu₅₀Zr₄₅Al₅ metallic glass/polyphenylene sulfide (PPS) composites with high relative densities by microwave processing the constituents in a separated H-field with an applied pressure of about 5 MPa. The heating behaviors and structural changes of the composites have been investigated. A good bonding state between metallic glassy and PPS particles is found. The gradient structure is also induced by microwave heating of the composites with a high fraction of PPS phase.