Nonadiabatic Electron Dynamics in Orthogonal Two-Color Laser Fields with Comparable Intensities.

We theoretically investigate the nonadiabatic subcycle electron dynamics in orthogonally polarized two-color laser fields with comparable intensities. The photoelectron dynamics is simulated by exact solution to the 3D time-dependent Schrödinger equation, and also by two other semiclassical methods, i.e., the quantum trajectory Monte Carlo simulation and the Coulomb-corrected strong field approximation. Through these methods, we identify the underlying mechanisms of the subcycle electron dynamics and find that both the nonadiabatic effects and the Coulomb potential play very important roles. The contribution of the nonadiabatic effects manifest in two aspects, i.e., the nonadiabatic ionization rate and the nonzero initial velocities at the tunneling exit. The Coulomb potential has a different impact on the electrons' trajectories for different relative phases between the two pulses.

Mechanisms of below-threshold harmonic generation in atoms.

Most previous studies have focused on high-order harmonic generation beyond the ionization threshold; mechanisms of below-threshold harmonics are less understood. We schematically study the harmonic emission process in this region by numerically solving the time-dependent Schrödinger equation of an atom in laser fields. We show that, besides the quantum path interference mechanism recently identified, the effects induced by the Coulomb potential also have a critical impact on these harmonics. These mechanisms can be distinguished in the structure of harmonic spectra by changing the laser wavelength and peak intensity. We find that the long quantum orbits can influence lower-order harmonics at a higher laser intensity. In addition, we show that the intensity-dependent steps of harmonic yield can disappear for certain harmonic orders, due to the trapping in the Rydberg states before recombination, which can explain recent experimental observations.

Classical-quantum correspondence for above-threshold ionization.

We measure high resolution photoelectron angular distributions (PADs) for above-threshold ionization of xenon atoms in infrared laser fields. Based on the Ammosov-Delone-Krainov theory, we develop an intuitive quantum-trajectory Monte Carlo model encoded with Feynman's path-integral approach, in which the Coulomb effect on electron trajectories and interference patterns are fully considered. We achieve a good agreement with the measured PADs of atoms for above-threshold ionization. The quantum-trajectory Monte Carlo theory sheds light on the role of ionic potential on PADs along the longitudinal and transverse direction with respect to the laser polarization, allowing us to unravel the classical coordinates (i.e., tunneling phase and initial momentum) at the tunnel exit for all of the photoelectrons of the PADs. We study the classical-quantum correspondence and build a bridge between the above-threshold ionization and the tunneling theory.

Molecular mechanism of colorectal cancer and screening of molecular markers based on bioinformatics analysis.

Genomics and bioinformatics methods were used to screen genes and molecular markers correlated with colorectal cancer incidence and progression, and their biological functions were analyzed. Differentially expressed genes were obtained using the GEO2R program following colorectal cancer chip data GSE44076 retrieval from the Gene Expression Omnibus gene expression comprehensive database. An online database (David) that combines annotation, visualization, and gene discovery was utilized for investigating genes. Pathway and protein analyses were performed via resources from the Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG). Visual analysis of the KEGG pathway was carried out according to ClueGO and CluePedia to establish the PPI network of gene interaction between pathways; the genes with the highest connectivity were screened by the molecular complex detection analysis method as Hub genes in this study; gene expression was verified by GEPIA online analysis tool, and Kaplan-Meier survival curve was drawn for prognosis analysis. By analyzing GSE44076 microarray data, 86 genes were selected, and colorectal cancer tissues' upregulation was observed in 27 genes and downregulation in 59 ones. GO assessment revealed that the differentially expressed genes were basically correlated with retinol dehydrogenase activity, carbon dehydrogenase activity, collagen-containing extracellular matrix, anchored component of memory, and cellular hormone metabolic process. Moreover, the KEGG assessment revealed that the differential genes contained various signal pathways such as retinol metabolism, chemical carotenogenesis, and nitrogen metabolism. Through further analysis of the PPI protein network, 4 clusters were obtained, and 16 Hub genes were screened out by combining the degree of each gene. Through the analysis of each gene on the prognosis of colon cancer through the GEPIA online analysis website, it was found that the expression levels of AQP8, CXCL8, and ZG16 genes were remarkably associated with colon cancer prognosis (P < 0.05). Genomics and bioinformatics methods can effectively analyze the genes and molecular markers correlated with colorectal cancer incidence and progression, help to systematically clarify the molecular mechanism of 16 key genes in colorectal cancer development and progression, and provide a theoretically valid insight for the screening of diagnostic markers of colorectal cancer and the selection of accurate targets for drug therapy.

Improved stress corrosion cracking resistance of in-situ TiB2/7050Al composite by pre-precipitation treatment.

A two-step aging treatment (50 L P, a peak aging following 50 ℃ pre-precipitation) has been investigated for the in-situ TiB2/7050Al composite. The 50 L P composite has the comparable mechanical properties to the composite at peak-aged (T6) state, and even better stress corrosion cracking resistance over the composite with the retrogression and re-aging (RRA) treatment. In detail, the different aging conditions lead to different precipitate morphologies and grain boundary microchemistries. According to the microstructure characteristics in the Al matrix, the 50 L P composite has considerably increased grain boundary precipitate interspace in comparison with the T6 composite, since the lower aging temperature should result in the reduced grain boundary precipitate number. Furthermore, the 50 L P composite has more Cu content in the grain boundary precipitate and reduced precipitate free zone width over the RRA composite, indicating the improved stress corrosion cracking resistance. For the reinforcement, the TiB2 particles should slightly aggravate the stress corrosion cracking susceptibility, since the grain boundary precipitates are still the preferential corrosion sites due to their lower corrosion potentials.

Morphological Evolutions of Ni-Rich Phases in Al-Si Piston Alloys during 250-400 °C Thermal Exposure Processes.

The thermal stability of the Al-Si alloys during the thermal exposure process from 250 °C to 400 °C was systematically investigated. The relationships between the morphological evolution and the mechanical changes of the alloys were determined through the Vickers hardness test and materials characterization method. Initially, the alloys exhibited similar thermal degradation behavior. For example, the exposure process of the alloy at 300 °C can be divided into two stages according to the changes of the alloy hardness and the matrix micro-hardness. In detail, the first stage (0-2 h) exhibited a severe reduction of the alloy hardness while the second stage showed a more leveled hardness during the following 98 h. There are three identified morphological characteristics of Ni-rich phases in the alloy. Furthermore, the differences in both composition and the micro-hardness between these Ni-rich phases were confirmed. The underlying relationships between the morphological transformation of the Ni-rich phases and hardness fluctuation in the alloy were correlated and elucidated. The observed alloy hardness increase when the exposure temperature was 400 °C was unexpected. This behavior was explained from the perspectives of both Ni-rich phases evolution and dispersoid formation.

Superior Strength and Ductility of In Situ Nano TiB2/Al-Cu-Mg Composites by Cold Rolling and Post-Aging Treatment.

In this work, the combination of cold rolling with post-aging treatment is developed to achieve the optimal strength-ductility for the in situ nano TiB2/Al-Cu-Mg composite. The microstructure and mechanical properties of the composite subjected to 20% thickness reduction of cold rolling at room temperature and their evolutions upon post-aging at different temperatures were investigated by means of a tensile test, differential scanning calorimetry, scanning electron microscopy, and transmission electron microscopy. It was found that the TiB2 particles were effective in dislocation pinning and accumulation during the cold-rolling process. The tensile tests indicated that both the yield and ultimate tensile strengths of the cold-rolling sample increased a lot due to the dislocation strengthening and precipitation strengthening generated by dynamic precipitation during cold rolling in comparison with the conventional T6 sample. After aging at 100 °C/12 h, the elongation to failure reached ~8.4%, which was higher than the conventional T6 sample. Meanwhile, there was also a dramatic increase of strength. The yield and ultimate tensile strengths are ~644 MPa and ~726 MPa, respectively. This remarkable strength-ductility combination was due to the modified microstructure caused prior to artificial aging by the cold-rolling method and the formation of nanosized Guinier-Preston-Bagaryatsky (GPB) zones. The underlying mechanisms related to the superior strength-ductility combination were discussed regarding the microstructural characteristics in the composite.

Characterization of PI (breast cancer cell special peptide) in MDA-MB-231 breast cancer cells and its potential therapeutic applications.

Gene therapy is one of the most important aspects of molecular targeted therapeutic approaches for tumors. A small molecule targeting carrier plays an important role in this process. PI, a new peptide found in our phage library, has been specifically suggested, combined with the human triple-negative breast cancer cell line MDA-MB­231, and may be developed as a targeting/individualization therapy strategy to be applied in breast cancer research. In this study, we further investigated whether this peptide could carry exogenous protein to the target cells by forming a fusion peptide. PI-GST and PI-TK were cloned into plasmids and used for expression studies, analyses of PI-mediated protein delivery efficiency, and to investigations into the effect of PI on thymidine kinase/ganciclovir-mediated cytotoxicity. Biodistribution profiles were also investigated in vivo. The results showed the PI fusion protein was expressed correctly in vitro, and could carry GST into the target cells. Under certain conditions, PI-TK sensitizes cells to ganciclovir more efficiently than TK. In vivo there was a trend for increased inhibition of tumor growth with PI-TK when ganciclovir was present. Therefore, our results suggest the potential of PI as a new specific target carrier in breast cancer therapy.

[Effects of CDH1 gene promoter methylation on expression of E-cadherin and beta-catenin and its clinicopathological significance in colon carcinoma].

OBJECTIVE: To investigate the relationship between methylation of the CDH1 gene promoter on the expression of E-cadherin and ß-catenin, and to evaluate the correlation with clinicopathological characteristics of the colonic carcinoma. METHODS: Methylation specific PCR (MSP) was used to detect CDH1 gene promoter methylation in the cancer tissue, adjacent tissues and normal tissues in 68 patients. The expression of E-cadherin and ß-catenin was determined by immunohistochemistry staining. RESULTS: The positive rate of CDH1 gene promoter methylation was 32.4% in adjacent tissues and 57.4% in cancer tissue, while no detectable methylation was found in all the normal tissues. The difference was statistically significant. The positive rate of E-cadherin was 92.6% in the normal tissues, 66.2% in the adjacent tissues and 44.1% in the cancer tissues. In all normal tissues, ß-catenin was expressed only at the cellular membrane but not in the cytosol or nucleus, while the expression of ß-catenin was present in the cytosol or nucleus in 29.4% of the adjacent tissues and 50.0% of the cancer tissues. The positive rate of CDH1 gene promoter methylation was negatively correlated with E-cadherin expression(r=-0.312, P=0.01) and positively correlated with ß-catenin cytosolic/nucleus expression(r=0.309, P=0.018). The differentiation and metastasis of colonic carcinoma were associated with the aberrant expression of E-cadherin, ß-catenin, and methylation of CDH1 promoter (P<0.05). CONCLUSION: CDH1 gene promoter methylation may lead to aberrant expression of E-cadherin and ß-catenin in colonic carcinoma, and may play an important role in promoting the invasion of tumor.