No abstract

Strong-field laser–molecule interaction forms much of the basis for initiating and probing ultrafast quantum dynamics. Previous studies aimed at elucidating the origins of vibrational coherences induced by intense laser fields have been confined to diatomic molecules. Furthermore, in all cases examined to date, vibrational wave packet motion is found to be induced by R-selective depletion; wave packet motion launched by bond softening, though theoretically predicted, remains hitherto unobserved. Here we employ the exquisite sensitivity of femtosecond extreme ultraviolet absorption spectroscopy to sub-picometer structural changes to observe both bond softening-induced vibrational wave packets, launched by the interaction of intense laser pulses with iodomethane, as well as multimode vibrational motion of the parent ion produced by strong-field ionization. In addition, we show that signatures of coherent vibrational motion in the time-dependent extreme ultraviolet absorption spectra directly furnish vibronic coupling strengths involving core-level transitions, from which geometrical parameters of transient core-excited states are extracted.

The eastern Tibetan Plateau has become increasingly warmer and drier since the 1990s. Such warming and drying has a great impact on ecosystem processes on the eastern Tibetan Plateau. To determine their combined effects on CO 2 and N 2 O emission rates, we conducted a field manipulative experiment in an alpine meadow of the eastern Tibetan Plateau during the growing season of 2009. The experiment showed that warming manipulation increased soil temperature by 1°C, and drying manipulation decreased soil water content by 6.8 %. We found that by counteracting the effect of low temperature in the area, experimental warming significantly increased soil microbial biomass, the number of bacteria, fungi, actinomycetes, ammonifying bacteria, nitrobacteria and denitrifying bacteria, and facilitated the emission rates of CO 2 and N 2 O by 33.4 and 31.5 %, respectively. However, decreased precipitation further aggravated soil water stress and inhibited the numbers of these organisms, and reduced the emission rates of CO 2 and N 2 O by 47.4 and 37.9 %, respectively. So decreased soil water content tended to offset the positive effect of warming. Compared to the positive effects of warming, decreased soil water content was shown in our study to have even greater impact on the eastern Tibetan Plateau during the growing season. Therefore, inhibition of CO 2 and N 2 O emission rates (32.3 and 29.3 %, respectively) by warming and drying will intensify if the combined effects of these climatic trends persist in the region.

The Wenchuan earthquake (Richter scale 8) on 12 May 2008 in southwestern China caused widespread ecosystem damage in the Longmenshan area. It is important to evaluate natural vegetation recovery processes and provide basic information on ecological aspects of the recovering environment after the earthquake. To circumvent the weather limits of remote sensing in the Wenchuan earthquake-hit areas, and to meet the need for regional observation analyses, three Landsat TM images pre-and post-earthquake in Mao County were used for analysis. Post-earthquake normalized difference vegetation index (NDVI) values were compared to pre-earthquake values with an NDVIbased index differencing method to determine the extent to which the vegetation was damaged in relation to the pre-earthquake pattern, and the rate of recovery was evaluated. The spatial characteristics of vegetation loss and natural recovery patterns were analyzed in relation to elevation, slope and aspect. The results indicated that severely damaged sites occurred mainly in river valleys, within a range of 1,500-2,500 m elevation and on slopes of 25-55°. The distance from rivers, rather than the distance from active faults, controls the damage patterns. After 1 year of natural regeneration, 36 % of the destroyed areas showed a decrease in NDVI value, 28.8 % showed very little change, 19.1 % showed an increase, and 16.1 % also increased with a recovery rate greater than 100 %. Moreover, there is a good correlation between recovery rate and both slope and elevation, but recovery patterns in the damaged area are complicated. Our results indicate that natural recovery in this arid valley is a slow process.

No abstract

The monitoring of circulating tumor cells (CTCs) has recently served as a promising approach for assessing prognosis and evaluating cancer treatment. We have already developed a CTCs enrichment platform by EpCAM recognition peptide-functionalized magnetic nanoparticles (EP@MNPs). However, considering heterogeneous CTCs generated through epithelial-mesenchymal transition (EMT), mesenchymal CTCs would be missed with this method. Notably, N-cadherin, overexpressed on mesenchymal CTCs, can facilitate the migration of cancer cells. Hence, we screened a novel peptide targeting N-cadherin, NP, and developed a new CTCs isolation approach via NP@MNPs to complement EpCAM methods’ deficiencies. NP@MNPs had a high capture efficiency (about 85%) of mesenchymal CTCs from spiked human blood. Subsequently, CTCs were captured and sequenced at the single-cell level via NP@MNPs and EP@MNPs, RNA profiles of which showed that epithelial and mesenchymal subgroups could be distinguished. Here, a novel CTCs isolation platform laid the foundation for mesenchymal CTCs isolation and subsequent molecular analysis.

Single‐cell RNA sequencing on circulating tumor cells (CTCs) proves useful to study mechanisms of tumor heterogeneity, metastasis, and drug resistance. Currently, single‐cell RNA sequencing of CTCs usually takes three prerequisite steps: enrichment of CTCs from whole blood, characterization of captured cells by immunostaining and microscopic imaging, and single‐cell isolation through micromanipulation. However, multiple pipetting and transferring steps can easily cause the loss of rare CTCs. To address this issue, a novel integrated microfluidic chip for sequential enrichment, isolation, and characterization of CTCs at single‐cell level, is developed. And, single CTC lysis is achieved on the same chip. The microfluidic chip includes functions of blood clot filtration, single‐cell isolation, identification, and target single‐cell lysate collection. By spiking tumor cells into whole blood, it is validated that this microfluidic chip can effectively conduct single‐cell CTCs RNA sequencing. The approach lays a solid foundation for the analysis of RNA expression profiling of single‐cell CTCs.

To sequence single circulating tumor cells (CTCs) from whole blood, a microfluidic chip was developed to perform blood filtering/CTC enrichment/CTC sorting and in situ MDA for whole genome sequencing.