Effect of temperature on resonant electron transport through stochastic conduction channels in superlattices

We show that resonant electron transport in semiconductor superlattices with an applied electric and tilted magnetic field can, surprisingly, become more pronounced as the lattice and conduction electron temperature increases from 4.2 K to room temperature and beyond. It has previously been demonstrated that at certain critical field parameters, the semiclassical trajectories of electrons in the lowest miniband of the superlattice change abruptly from fully localized to completely unbounded. The unbounded electron orbits propagate through intricate web patterns, known as stochastic webs, in phase space, which act as conduction channels for the electrons and produce a series of resonant peaks in the electron drift velocity versus electric-field curves. Here, we show that increasing the lattice temperature strengthens these resonant peaks due to a subtle interplay between the thermal population of the conduction channels and transport along them. This enhances both the electron drift velocity and the influence of the stochastic webs on the current-voltage characteristics, which we calculate by making self-consistent solutions of the coupled electron transport and Poisson equations throughout the superlattice. These solutions reveal that increasing the temperature also transforms the collective electron dynamics by changing both the threshold voltage required for the onset of self-sustained current oscillations, produced by propagating charge domains, and the oscillation frequency

Quantum Dynamics Study of Photoexcited Aniline

A model Hamiltonian based on the quadratic vibronic coupling model is developed to describe the photoinduced dynamics of aniline excited to the manifold of states comprising its first six singlet electronic states. The model Hamiltonian is parametrized by fitting to the results of extensive EOM-CCSD calculations and its validity tested through the calculation of the first two bands in the electronic absorption spectrum of aniline. It is found that two previously neglected 3p Rydberg states play an important role in the dynamics of aniline following excitation into the first two ¹ππ* states. Assignments of the vibrational structure seen in the experimental spectrum is made, and the role played by the Herzberg–Teller effect in excitation to the first ¹ππ* state is analyzed

Controlling Graphene Ultrafast Hot Carrier Response from Metal-like to Semiconductor-like by Electrostatic Gating

We investigate the ultrafast terahertz response of electrostatically gated graphene upon optical excitation. We observe that the photoinduced terahertz absorption increases in charge neutral graphene but decreases in highly doped graphene. We show that this transition from semiconductor-like to metal-like response is unique for zero bandgap materials such as graphene. In charge neutral graphene photoexcited hot carriers effectively increase electron and hole densities and increase the conductivity. In highly doped graphene, however, photoexcitation does not change net conducting carrier concentration. Instead, it mainly increases electron scattering rate and reduce the conductivity

Conformation Analysis of Ferrocene and Decamethylferrocene via Full-Potential Modeling of XANES and XAFS Spectra

Recent high-accuracy X-ray absorption measurements of the sandwich organometallics ferrocene (Fc) and decamethylferrocene (DmFc) at temperatures close to liquid helium are compared with new full-potential modeling of X-ray absorption fine structure (XAFS) covering the near-edge region (XANES) and above up to <i>k</i> = 7 Å^–1. The implementation of optimized calculations of the oscillatory part of the spectrum from the package FDMX allows detailed study of the spectra in regions of the photoelectron momentum most sensitive to differences in the molecular stereochemistry. For Fc and DmFc, this corresponds to the relative rotation of the cyclopentadienyl rings. When applied to high-accuracy XAFS of Fc and DmFc, the FDMX theory gives clear evidence for the eclipsed conformation for Fc and the staggered conformation for DmFc for frozen solutions at ca. 15 K. This represents the first clear experimental assignment of the solution structures of Fc and DmFc and reveals the potential of high-accuracy XAFS for structural analysis

Additional file 1: Table S1. of A retrospective paired study: efficacy and toxicity of nimotuzumab versus cisplatin concurrent with radiotherapy in nasopharyngeal carcinoma

Prognostic factors for overall survival (Univariate) (N = 104). Table S2. Prognostic factors for overall survival (multivariable) (N = 104). Table S3. Toxicities in stage III and IV patients with h-R3/RT and CDDP/RT (N = 78). Table S4. Assignment expressions for factors in the table of patients’ characteristics. Table S5. Patients’ compliance (104 cases). Table S6. Neoadjuvant chemotherapy was recommended by NCCN guidelines of Head and Neck Cancer. Table S7. General information for all 302 patients of CDDP/RT and h-R3/RT group. Table S8. Prognostic factors for Overall Survival of all 302 patients (Univariate). Table S9. Prognostic factors for Overall Survival of all 302 patients (Multivariable). (ZIP 437 kb

Additional file 2: Figure S1. of A retrospective paired study: efficacy and toxicity of nimotuzumab versus cisplatin concurrent with radiotherapy in nasopharyngeal carcinoma

Overall survival of stage II patients who received h-R3/RT or CDDP/RT. Figure S2. Overall survival of patients aged more than 60 years old who received h-R3/RT or CDDP/RT. Figure S3. Overall survival in stage III and IV patients with h-R3/RT and CDDP/RT. (ZIP 12 kb

Ampelopsin reduces the migration and invasion of ovarian cancer cells via inhibition of epithelial-to-mesenchymal transition

Ampelopsin has displayed anticancer activity in several types of cancers. However, no evidence has been reported for the direct effect of ampelopsin on ovarian cancer cell migration and invasion, and the underling mechanisms have not yet been clearly established. The aim of the present study was to investigate the influence of ampelopsin on the migration and invasion of ovarian cancer. Proliferation and viability of the ovarian cancer cells were detected by MTT assay. Migration and invasion of the cells were detected, respectively, by scratch wound healing assay and Transwell assay. The expression levels of epithelial-to-mesenchymal transition (EMT) markers were detected at the protein level after stimulation with ampelopsin. Then, the expression levels of NF-κB and p-IκBα were detected with western blot analysis. Meanwhile, an inhibitor of NF-κB was used to investigate the effect of ampelopsin. Finally, the expression of Snail was also detected. Proliferation, migration and invasion of the A2780 cells were all inhibited following the application of ampelopsin. Ampelopsin upregulated E-cadherin and downregulated N-cadherin and vimentin in a concentration- and time-dependent manner. Ampelopsin also exerted its ability to suppress the nuclear translocation of the NF-κB pathway. Administration of the inhibitor BAY11‑7082 confirmed the roles of NF-κB in the expression of EMT markers and its transcription factor. These results demonstrated that ampelopsin inhibited EMT and reduced the invasion of ovarian cancer cells via the NF-κB/Snail pathway

Optimizing Broadband Terahertz Modulation with Hybrid Graphene/Metasurface Structures

We demonstrate efficient terahertz (THz) modulation by coupling graphene strongly with a broadband THz metasurface device. This THz metasurface, made of periodic gold slit arrays, shows near unity broadband transmission, which arises from coherent radiation of the enhanced local-field in the slits. Utilizing graphene as an active load with tunable conductivity, we can significantly modify the local-field enhancement and strongly modulate the THz wave transmission. This hybrid device also provides a new platform for future nonlinear THz spectroscopy study of graphene

Transformation of Mercury at the Bottom of the Arctic Food Web: An Overlooked Puzzle in the Mercury Exposure Narrative

We show 2008 seasonal trends of total and monomethyl mercury (THg and MeHg, respectively) in herbivorous (<i>Calanus hyperboreus</i>) and predatory (Chaetognaths, <i>Paraeuchaeta glacialis</i>, and <i>Themisto abyssorum</i>) zooplankton species from the Canadian High Arctic (Amundsen Gulf and the Canadian Beaufort Sea) in relation to ambient seawater and diet. It has recently been postulated that the Arctic marine environment may be exceptionally vulnerable to toxic MeHg contamination through postdepositional processes leading to mercury transformation and methylation. Here, we show that <i>C. hyperboreus</i> plays a hitherto unrecognized central role in mercury transformation while, itself, not manifesting inordinately high levels of THg compared to its prey (pelagic particulate organic matter (POM)). <i>Calanus hyperboreus</i> shifts Hg from mainly inorganic forms in pelagic POM (>99.5%) or ambient seawater (>90%) to primarily organic forms (>50%) in their tissue. We calculate that annual dietary intake of MeHg could supply only ∼30% of the MeHg body burden in <i>C. hyperboreus</i> and, thus, transformation within the species, perhaps mediated by gut microbial communities, or bioconcentration from ambient seawater likely play overriding roles. Seasonal THg trends in <i>C. hyperboreus</i> are variable and directly controlled by species-specific physiology, e.g., egg laying and grazing. Zooplankton that prey on species such as <i>C. hyperboreus</i> provide a further biomagnification of MeHg and reflect seasonal trends observed in their prey

Wide-Gap Semiconducting Graphene from Nitrogen-Seeded SiC

All carbon electronics based on graphene have been an elusive goal. For more than a decade, the inability to produce significant band-gaps in this material has prevented the development of graphene electronics. We demonstrate a new approach to produce semiconducting graphene that uses a submonolayer concentration of nitrogen on SiC sufficient to pin epitaxial graphene to the SiC interface as it grows. The resulting buckled graphene opens a band gap greater than 0.7 eV in the otherwise continuous metallic graphene sheet