Dimensional crossover of thermal conductance in graphene nanoribbons: A first-principles approach

First-principles density-functional calculations are performed to investigate the thermal transport properties in graphene nanoribbons (GNRs). The dimensional crossover of thermal conductance from one to two dimensions (2D) is clearly demonstrated with increasing ribbon width. The thermal conductance of GNRs in a few nanometer width already exhibits an approximate low-temperature dependence of $T^{1.5}$, like that of 2D graphene sheet which is attributed to the quadratic nature of dispersion relation for the out-of-plane acoustic phonon modes. Using a zone-folding method, we heuristically derive the dimensional crossover of thermal conductance with the increase of ribbon width. Combining our calculations with the experimental phonon mean-free path, some typical values of thermal conductivity at room temperature are estimated for GNRs and for 2D graphene sheet, respectively. Our findings clarify the issue of low-temperature dependence of thermal transport in GNRs and suggest a calibration range of thermal conductivity for experimental measurements in graphene-based materials.Comment: 18 pages, 4 figure

Controlling Excitations Inversion of a Cooper Pair Box Interacting with a Nanomechanical Resonator

We investigate the action of time dependent detunings upon the excitation inversion of a Cooper pair box interacting with a nanomechanical resonator. The method employs the Jaynes-Cummings model with damping, assuming different decay rates of the Cooper pair box and various fixed and t-dependent detunings. It is shown that while the presence of damping plus constant detunings destroy the collapse/revival effects, convenient choices of time dependent detunings allow one to reconstruct such events in a perfect way. It is also shown that the mean excitation of the nanomechanical resonator is more robust against damping of the Cooper pair box for convenient values of t-dependent detunings.Comment: 11 pages, 5 figure

Investigation of M1 transitions of the ground-state configuration of In-like Tungsten

Three visible lines of M1 transitions from In-like W were recorded using the Shanghai permanent magnet electron beam ion trap. The experimental wavelengths were measured as 493.84 $\pm$ 0.15, 226.97 $\pm$ 0.13 and 587.63 $\pm$ 0.23 nm (vacuum wavelengths). These results are in good agreement with theoretical predictions obtained using large-scale Relativistic Many-Body Perturbation Theory, in the form of the Flexible Atomic Code.Comment: 7 pages, 3 figure

Species specific exome probes reveal new insights in positively selected genes in nonhuman primates

Nonhuman primates (NHP) are important biomedical animal models for the study of human disease. Of these, the most widely used models in biomedical research currently are from the genus Macaca. However, evolutionary genetic divergence between human and NHP species makes human-based probes inefficient for the capture of genomic regions of NHP for sequencing and study. Here we introduce a new method to resequence the exome of NHP species by a designed capture approach specifically targeted to the NHP, and demonstrate its superior performance on four NHP species or subspecies. Detailed investigation on biomedically relevant genes demonstrated superior capture by the new approach. We identified 28 genes that appeared to be pseudogenized and inactivated in macaque. Finally, we identified 187 genes showing strong evidence for positive selection across all branches of the primate phylogeny including many novel findings

Using scanning electron microscopy and molecular data to discover a new species from old herbarium collections: The case of Phlomoides henryi (Lamiaceae, Lamioideae)

Phlomoides is one of the largest genera of Lamiaceae with approximately 150–170 species distributed mainly in Eurasia. In this study, we describe and illustrate a new species, P. henryi, which was previously misidentified as P. bracteosa, from Yunnan Province, southwest China. Molecular phylogenetic analyses revealed that P. henryi is found within a clade in which most species lack basal leaves. In this clade, the new species is morphologically distinct from P. rotata in having an obvious stem and, from the rest, by having transparent to white trichomes inside the upper corolla lip. In addition, micro-features of trichomes on the calyx and leaf epidermis can differentiate the new species from other species grouped in the same clade and a key, based on trichome morphology for these species, is provided. The findings demonstrate that the use of scanning electron microscopy can reveal inconspicuous morphological affinities amongst morphologically similar species and play an important role in the taxonomic study of the genus Phlomoides

Large Clones on Cliff Faces: Expanding by Rhizomes through Crevices

Background and Aims Large clones of rhizomatous plants are found in many habitats, but little is known about whether such clones also occur on cliff faces where environmental conditions are extremely harsh and heterogeneous. Methods Using molecular (intersimple sequence repeat, ISSR) markers, the genotypic composition of a cliff-face population of Oxyria sinensis in Sichuan, China, was investigated. Key Results The 98 O. sinensis ramets sampled belonged to 12 different genotypes (clones). The three most frequent clones were represented with 45, 22 and 12 ramets, respectively; the remaining nine were represented with only one to five ramets. The three largest clones spanned at least 2·7 m in the vertical direction and 4·6-6·9 m in the horizontal direction on the cliff face. Conclusions On the cliff face, large clones of O. sinensis are formed by rhizomes growing along the crevices. Expansion by rhizomes may help O. sinensis to exploit the patchy resources and support establishment and growth of new ramets. Moreover, rooted ramets connected by rhizomes may effectively reduce the susceptibility of O. sinensis to rock fall and erosion and thus greatly improve the chances for long-term survival. The multi-clone structure indicates that sexual reproduction is also important for the long-term persistence of O. sinensis populations on cliff

The First Mitochondrial Genome of the Living-Fossil Sawfly \u3cem\u3eMacroxyela ferruginea\u3c/em\u3e (Hymenoptera: Xyelidae, Macroxyelinae)

The living-fossil sawfly Macroxyela ferruginea (Xyelidae: Macroxyelinae) was one of the oldest species of Hymenoptera. We sequenced the mitochondrial genome, 15,465 bp in size. All 37 typical mitochondrial genes were possessed. There is only one rearrangement of gene order, where trnM and trnQ were shuffled. We also found this order was shared with Xyela sp., which also belongs to family Xyelidae. The 13 protein-coding genes of this sequence and the other 10 species from eight superfamilies in Hymenoptera were all used for phylogenetic analysis by maximum likelihood (ML) analysis and Bayesian inference (BI), with Ascaloptynx appendiculatus from Neuroptera as an outgroup. The topology demonstrated that M. ferruginea was sister to Xyela sp., supporting that they belong to one family Xyelidae

Inquiry web-based learning to enhance information problem solving competences in science

Early research on using web information indicates that secondary students fail to explore much web tools, use them naively and have serious difficulties to understand and integrate web information. In response to these challenges, the main goal of this research has been to design, implement and evaluate an instructional approach that helps students learn from web information. We have developed on-line learning materials which focus on specific curricular contents and provide specific scaffolds to help students accomplish web-based tasks and develop specific information problem-solving competencies. These scaffolds have intended to give support to students involved in information-seeking activities as they were asked questions, searched for information, organised and assessed their findings, and created rich representations of their newly-constructed understandings. We have designed a one year long study to investigate the depth and accuracy of 127 secondary students, as regards their content understanding as well as their development of information problem-solving competencies when using on-line resources to solve instructional tasks. Our research demonstrates that the experimental group performed computer-based activities statistically better than the control group. Our findings also suggest that students were able to develop accurate and in-depth understanding from web information if they could appropriately use search and managerial strategies. This research lends evidence to questions regarding the value of students engaging in on-line inquiry web-based learning to enhance content understanding and to develop more efficient information problem-solving competencies in secondary education