The recent focus on topological insulators is due to the scientific interest in the new state of quantum matter as well as the technology potential for a new generation of THz optoelectronics, ...spintronics and quantum computations. It is important to elucidate the dynamics of the Dirac fermions in the topologically protected surface state. Hence we utilized a novel ultrafast optical pump mid-infrared probe to explore the dynamics of Dirac fermions near the Dirac point. The femtosecond snapshots of the relaxation process were revealed by the ultrafast optics. Specifically, the Dirac fermion-phonon coupling strength in the Dirac cone was found to increase from 0.08 to 0.19 while Dirac fermions were away from the Dirac point into higher energy states. Further, the energy-resolved transient reflectivity spectra disclosed the energy loss rate of Dirac fermions at room temperature was about 1 meV/ps. These results are crucial to the design of Dirac fermion devices.
CTONG0806 assessed the efficacy of pemetrexed versus gefitinib as second-line treatment in advanced nonsquamous nonsmall-cell lung cancer (NSCLC) harboring wild-type epidermal growth factor receptor ...(EGFR).
Patients with locally advanced or metastatic nonsquamous NSCLC harboring wild-type EGFR, detected by direct sequencing, and previously treated with platinum-based chemotherapy were randomized to receive gefitinib (250 mg/day) orally or pemetrexed (500 mg/m2) i.v. on day 1 of a 21-day cycle until disease progression or unacceptable toxicity. The primary end point was progression-free survival (PFS). The Independent Review Committee (IRC) evaluated all pictorial data.
From February 2009 to August 2012, 161 patients were enrolled, and 157 were assessable (81 in the gefitinib arm, 76 in the pemetrexed arm). Baseline characteristics were balanced between the two arms. The median PFSs were 4.8 versus 1.6 months in the pemetrexed and gefitinib arms, respectively hazard ratio (HR) 0.54, 95% confidence interval (CI) 0.40–0.75, P < 0.001 as confirmed by IRC evaluation (5.6versus 1.7 months, HR 0.53, 95% CI 0.38–0.75, P < 0.001). The median overall survival (OS) showed a trend of superiority in the pemetrexed arm (12.4 versus 9.6 months, HR 0.72, 95% CI 0.49–1.04, P = 0.077). Quality-of-life assessment showed no marked difference between the arms. No unexpected adverse events were found. Of 108 patients with sufficient DNA samples, EGFR mutation status was re-tested by Scorpion amplification refractory mutation system (ARMS); 32 (29.6%) tested positive (19 in the pemetrexed arm, 13 in the gefitinib arm; median PFS: 8.1 versus 7.0 months, HR 0.94, 95% CI 0.43–2.08, P = 0.877).
CTONG0806 is the first trial to show significant improvement in PFS and an improved OS trend with pemetrexed compared with gefitinib as second-line setting treatment of EGFR wild-type advanced nonsquamous NSCLC. ARMS is superior to direct sequencing in excluding false-negative patients.
NCT00891579.
We report terahertz (THz) light-induced second harmonic generation, in superconductors with inversion symmetry that forbid even-order nonlinearities. The THz second harmonic emission vanishes above ...the superconductor critical temperature and arises from precession of twisted Anderson pseudospins at a multicycle, THz driving frequency that is not allowed by equilibrium symmetry. We explain the microscopic physics by a dynamical symmetry breaking principle at sub-THz-cycle by using quantum kinetic modeling of the interplay between strong THz-lightwave nonlinearity and pulse propagation. The resulting nonzero integrated pulse area inside the superconductor leads to light-induced nonlinear supercurrents due to subcycle Cooper pair acceleration, in contrast to dc-biased superconductors, which can be controlled by the band structure and THz driving field below the superconducting gap.
In this work, the electronic properties of phosphorene nanoribbons with different width and edge configurations are studied by using density functional theory. It is found that the armchair ...phosphorene nanoribbons are semiconducting while the zigzag nanoribbons are metallic. The band gaps of armchair nanoribbons decrease monotonically with increasing ribbon width. By passivating the edge phosphorus atoms with hydrogen, the zigzag series also become semiconducting, while the armchair series exhibit a larger band gap than their pristine counterpart. The electronic transport properties of these phosphorene nanoribbons are then investigated using Boltzmann theory and relaxation time approximation. We find that all the semiconducting nanoribbons exhibit very large values of Seebeck coefficient and can be further enhanced by hydrogen passivation at the edge. Taking pristine armchair nanoribbons and hydrogen-passivated zigzag naoribbons with width N = 7, 8, 9 as examples, we calculate the lattice thermal conductivity with the help of phonon Boltzmann transport equation and evaluate the width-dependent thermoelectric performance. Due to significantly enhanced Seebeck coefficient and decreased thermal conductivity, we find that at least one type of phosphorene nanoribbons can be optimized to exhibit very high figure of merit (ZT values) at room temperature, which suggests their appealing thermoelectric applications.
The coloration of some butterflies, Pachyrhynchus weevils, and many chameleons are notable examples of natural organisms employing photonic crystals to produce colorful patterns. Despite advances in ...nanotechnology, we still lack the ability to print arbitrary colors and shapes in all three dimensions at this microscopic length scale. Here, we introduce a heat-shrinking method to produce 3D-printed photonic crystals with a 5x reduction in lattice constants, achieving sub-100-nm features with a full range of colors. With these lattice structures as 3D color volumetric elements, we printed 3D microscopic scale objects, including the first multi-color microscopic model of the Eiffel Tower measuring only 39 µm tall with a color pixel size of 1.45 µm. The technology to print 3D structures in color at the microscopic scale promises the direct patterning and integration of spectrally selective devices, such as photonic crystal-based color filters, onto free-form optical elements and curved surfaces.
Uncontrolled growth and diffused invasion are major causes of mortality in patients with malignant gliomas. Nodal has been shown to have a central role in the tumorigenic signaling pathways of ...malignant melanoma. In this study, we show that grade IV human glioma cell lines expressed different levels of Nodal, paralleled to the potential for cell invasiveness. Treatment of glioma cell lines with recombinant Nodal (rNodal) increased matrix metalloproteinase 2 (MMP-2) secretion and cell invasiveness. The ectopic expression of Nodal in GBM glioma cells that expressed Nodal at low level resulted in increased MMP-2 secretion, enhanced cell invasiveness, raised cell proliferation rates in vitro, increased tumor growth in vivo, and was associated with poor survival in a mice xenograft model. In contrast, the knockdown of Nodal expression in U87MG glioma cells with high Nodal expression level had reduced MMP-2 secretion, less cell invasiveness, lower tumor growth in vivo and longer lifespan in mice with U87MG/shNodal cell xenografts. In addition, Nodal knockdown promoted the reversion of malignant glioma cells toward a differentiated astrocytic phenotype. Furthermore, our data support the notion that Nodal may regulate glioma progression through the induction of the leukemia inhibitory factor (LIF) and Cripto-1 through activated Smad.
The Higgs mechanism, i.e., spontaneous symmetry breaking of the quantum vacuum, is a cross-disciplinary principle, universal for understanding dark energy, antimatter and quantum materials, from ...superconductivity to magnetism. Unlike one-band superconductors (SCs), a conceptually distinct Higgs amplitude mode can arise in multi-band, unconventional superconductors via strong interband Coulomb interaction, but is yet to be accessed. Here we discover such hybrid Higgs mode and demonstrate its quantum control by light in iron-based high-temperature SCs. Using terahertz (THz) two-pulse coherent spectroscopy, we observe a tunable amplitude mode coherent oscillation of the complex order parameter from coupled lower and upper bands. The nonlinear dependence of the hybrid Higgs mode on the THz driving fields is distinct from any known SC results: we observe a large reversible modulation of resonance strength, yet with a persisting mode frequency. Together with quantum kinetic modeling of a hybrid Higgs mechanism, distinct from charge-density fluctuations and without invoking phonons or disorder, our result provides compelling evidence for a light-controlled coupling between the electron and hole amplitude modes assisted by strong interband quantum entanglement. Such light-control of Higgs hybridization can be extended to probe many-body entanglement and hidden symmetries in other complex systems.
A new measurement of the reactor antineutrino flux and energy spectrum by the Daya Bay reactor neutrino experiment is reported. The antineutrinos were generated by six 2.9 GWth nuclear reactors and ...detected by eight antineutrino detectors deployed in two near（560 m and 600 m flux-weighted baselines） and one far（1640 m flux-weighted baseline） underground experimental halls. With 621 days of data, more than 1.2 million inverse beta decay（IBD） candidates were detected. The IBD yield in the eight detectors was measured, and the ratio of measured to predicted flux was found to be 0.946±0.020（0.992±0.021） for the Huber＋Mueller（ILL＋Vogel） model. A 2.9σ deviation was found in the measured IBD positron energy spectrum compared to the predictions. In particular, an excess of events in the region of 4–6 MeV was found in the measured spectrum, with a local significance of 4.4σ. A reactor antineutrino spectrum weighted by the IBD cross section is extracted for model-independent predictions.
Talins are adaptor proteins that regulate focal adhesion signaling by conjugating integrins to the cytoskeleton. Talins directly bind integrins and are essential for integrin activation. We ...previously showed that β1 integrins are activated in metastatic prostate cancer (PCa) cells, increasing PCa metastasis to lymph nodes and bone. However, how β1 integrins are activated in PCa cells is unknown. In this study, we identified a novel mechanism of β1 integrin activation. Using knockdown experiments, we first demonstrated that talin1, but not talin2, is important in β1 integrin activation. We next showed that talin1 S425 phosphorylation, but not total talin1 expression, correlates with metastatic potential of PCa cells. Expressing a non-phosphorylatable mutant, talin1(S425A), in talin1-silenced PC3-MM2 and C4-2B4 PCa cells, decreased activation of β1 integrins, integrin-mediated adhesion, motility and increased the sensitivity of the cells to anoikis. In contrast, reexpression of the phosphorylation-mimicking mutant talin1(S425D) led to increased β1 integrin activation and generated biologic effects opposite to talin1(S425A) expression. In the highly metastatic PC3-MM2 cells, expression of a non-phosphorylatable mutant, talin1(S425A), in talin1-silenced PC3-MM2 cells, abolished their ability to colonize in the bone following intracardiac injection, while reexpression of phosphorylation-mimicking mutant talin1(S425D) restored their ability to metastasize to bone. Immunohistochemical staining demonstrated that talin S425 phosphorylation is significantly increased in human bone metastases when compared with normal tissues, primary tumors or lymph node metastases. We further showed that p35 expression, an activator of Cdk5, and Cdk5 activity were increased in metastatic tumor cells, and that Cdk5 kinase activity is responsible for talin1 phosphorylation and subsequent β1 integrin activation. Together, our study reveals Cdk5-mediated phosphorylation of talin1 leading to β1 integrin activation is a novel mechanism that increases metastatic potential of PCa cells.
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