We utilize 100 fs optical pulses to induce ultrafast disorder of 35-to 150-nm thick single Au(111) crystals and observe the subsequent structural evolution using 0.6-ps, 8.04-keV X-ray pulses. Monitoring the picosecond time-dependent modulation of the X-ray diffraction intensity, width, and shift, we have measured directly electron/phonon coupling, phonon/lattice interaction, and a histogram of the lattice disorder evolution, such as lattice breath due to a pressure wave propagating at sonic velocity, lattice melting, and recrystallization, including mosaic formation. Results of theoretical simulations agree and support the experimental data of the lattice/liquid phase transition process. These time-resolved X-ray diffraction data provide a detailed description of all the significant processes induced by ultrafast laser pulses impinging on thin metallic single crystals.ultrafast X-ray diffraction | laser-induced phase transition | coherent phonon | annealing | grain growth L attice disorder and phase transition in metal, semiconductor, and alloy are of vital importance in both fundamental science and technology. Irradiation with femtosecond laser pulses induces lattice disorder (1), which could be (i) a purely electronic nonthermal order-disorder process by injecting carriers into bulk semiconductor crystals, such as Si (2, 3) and GaAs (4, 5) within 1 ps; (ii) a purely thermal-disorder thermal process that depends on electron/phonon, phonon/phonon, and phonon/lattice interaction time in metal films, especially in noble metals, such as Au (6, 7); (iii) a combination of thermal-and nonthermal-disorder with the ratio depending on the laser fluence (8). When the laser fluence is sufficient, the phase transition from solid to liquid will occur and the melting process is considered to involve both thermal and nonthermal processes, whereas in gold (9-11) and aluminum films, which is the dominant process is still under debate (12-14). The laser heating and melting of the gold film studies presented in this paper were induced by low excitation levels, therefore the electronic effects on the stability of the lattice are not expected to occur (15), which is in contrast to the high excitation levels used for electronic hardening in gold (10).In this paper, we describe experiments that utilize subpicosecond time-resolved X-ray diffraction (XRD) to measure directly the transient changes in the crystal structure induced by 400-nm, 100-fs laser pulses impinging upon the surface of 35-, 70-, and 150-nm-thick Au(111) single-crystal films. The experiments presented here may be assigned to a weak excitation region, at fluence lower than 15 mJ∕cm 2 , where the blast wave and coherent phonons were observed, and a strong excitation region, at fluencies of 37 mJ∕cm 2 and above, where melting occurs. In addition, a pressure blast wave, formed immediately upon excitation, induced lattice contraction (16) that propagated through the bulk of the crystal at sonic velocity, generating stress and the wellknown sonic wave. We will show that, i...
Curvularia lunata is an important pathogen causing Curvularia leaf spot in maize. Significant pathogenic variation has been found in C. lunata. To better understand the mechanism of this phenomenon, we consecutively put the selective pressures of resistant maize population on C. lunata strain WS18 (low virulence) artificially. As a result, the virulence of this strain was significantly enhanced. Using 2DE, 12 up-regulated and four down-regulated proteins were identified in virulence-increased strain compared to WS18. Our analysis revealed that melanin synthesis-related proteins (Brn1, Brn2, and scytalone dehydratase) and stress tolerance-related proteins (HSP 70) directly involved in the potential virulence growth as crucial markers or factors in C. lunata. To validate 2DE results and screen differential genes at mRNA level, we constructed a subtracted cDNA library (tester: virulence-increased strain; driver: WS18). A total of 188 unigenes were obtained this way, of which 14 were indicators for the evolution of pathogen virulence. Brn1 and hsp genes exhibited similar expression patterns corresponding to proteins detected by 2DE. Overall, our results indicated that differential proteins or genes, being involved with melanin synthesis or tolerance response to stress, could be considered as hallmarks of virulence increase in C. lunata.
A feasibility study for non-invasive diabetic detection based on a low cost portable Raman spectrometer and urine surface-enhanced Raman spectroscopy (SERS) is presented. SERS of 41 urine samples (20 diabetic patients and 21 healthy volunteers) mixed with silver nanoparticles are measured by a self-developed portable Raman spectrometer (Hx-Spec) which is excited by a 785 nm diode laser and the spectrum range is 200–2700 cm−1 with a resolution (FWHM) of 6 cm−1. By methods of principal components analysis and linear discriminant analysis, a diagnostic sensitivity of 85% and a specificity of 90.5% are achieved in separating diabetic samples from normal urine specimens. The corresponding receiver operating characteristic is 0.836, indicting the accuracy of the predictive model.
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