Did incision of the Three Gorges begin in the Eocene?

Like the other large river systems that drain the area of the India-Asia collision, the Yangtze River was assembled through a series of Cenozoic capture events. These events are important for orogenic erosion and sediment delivery, but their timing remains largely unknown. Here we identify enhanced cooling in the Three Gorges region in central China, a key capture site during basin development, beginning at 40–45 Ma. This event is not visible in regional thermochronological data, but is near-contemporaneous with the onset of widespread denudation in the Sichuan Basin, just upstream of the Three Gorges. While we cannot rule out alternative explanations, the simplest mechanism that links these events is progressive capture of the middle Yangtze River by the lower Yangtze and the onset of incision in the Three Gorges. This model agrees with independent mid-Cenozoic estimates for the timing of middle Yangtze River diversion and capture, and provides a plausible outlet for large volumes of erosional detritus from the Sichuan Basin

Surface Roughness and Effective Stick-Slip Motion

The effect of random surface roughness on hydrodynamics of viscous incompressible liquid is discussed. Roughness-driven contributions to hydrodynamic flows, energy dissipation, and friction force are calculated in a wide range of parameters. When the hydrodynamic decay length (the viscous wave penetration depth) is larger than the size of random surface inhomogeneities, it is possible to replace a random rough surface by effective stick-slip boundary conditions on a flat surface with two constants: the stick-slip length and the renormalization of viscosity near the boundary. The stick-slip length and the renormalization coefficient are expressed explicitly via the correlation function of random surface inhomogeneities. The effective stick-slip length is always negative signifying the effective slow-down of the hydrodynamic flows by the rough surface (stick rather than slip motion). A simple hydrodynamic model is presented as an illustration of these general hydrodynamic results. The effective boundary parameters are analyzed numerically for Gaussian, power-law and exponentially decaying correlators with various indices. The maximum on the frequency dependence of the dissipation allows one to extract the correlation radius (characteristic size) of the surface inhomogeneities directly from, for example, experiments with torsional quartz oscillators.Comment: RevTeX4, 14 pages, 3 figure

Clustering dynamics of Lagrangian tracers in free-surface flows

We study the formation of clusters of passive Lagrangian tracers in a non-smooth turbulent flow in a flat free-slip surface as a model for particle dynamics on free surfaces. Single particle and pair dispersion show different behavior for short and large times: on short times particles cluster exponentially rapidly until patches of the size of the divergence correlation length are depleted; on larger times the pair dispersion is dominated by almost ballistic hopping between clusters. We also find that the distribution of particle density is close to algebraic and can trace this back to the exponential distribution of the divergence field of the surface flow.Comment: 5 pages, 5 Postscript figure

Comparative Erythrocyte Metabolism in Marsupials and Monotremes

Concentrations of ATP and DPG, activities of 10 enzymes and the glycolytic rates were measured in the erythrocytes of 11 species of marsupials and two species of monotremes. Mean DPG concentrations were greater in the erythrocytes of marsupials than those of eutherian mammals. The opposite is true of ATP. Significant findings from the results of enzyme activities were: high activity of hexokinase (7.39 + 0.82 EU/g Hb) in the short-beaked echidna, pyruvate kinase (37.49 + 1.0 EU/g) Hb in bridled nailtail wallaby and glucose-6-phosphate dehydrogenase (G6PD; 41.66 + 1.24 EU/g Rb) in black-striped wallaby. About 6- to 7-fold difference in the activity of G6PD levels between the two species of wombats was confirmed. Glucose phosphate isomerase activity was also shown to be twice as high in the red cells of the common wombat compared with those of the southern hairy nosed wombat. There were wide variations in the glycolytic rate among the species examined

Multiband tight-binding theory of disordered ABC semiconductor quantum dots: Application to the optical properties of alloyed CdZnSe nanocrystals

Zero-dimensional nanocrystals, as obtained by chemical synthesis, offer a broad range of applications, as their spectrum and thus their excitation gap can be tailored by variation of their size. Additionally, nanocrystals of the type ABC can be realized by alloying of two pure compound semiconductor materials AC and BC, which allows for a continuous tuning of their absorption and emission spectrum with the concentration x. We use the single-particle energies and wave functions calculated from a multiband sp^3 empirical tight-binding model in combination with the configuration interaction scheme to calculate the optical properties of CdZnSe nanocrystals with a spherical shape. In contrast to common mean-field approaches like the virtual crystal approximation (VCA), we treat the disorder on a microscopic level by taking into account a finite number of realizations for each size and concentration. We then compare the results for the optical properties with recent experimental data and calculate the optical bowing coefficient for further sizes

Informal entrepreneurship in developing economies: the impacts of starting-up unregistered on firm performance

To advance understanding of the entrepreneurship process in developing economies, this paper evaluates whether registered enterprises that initially avoid the cost of registration, and focus their resources on overcoming other liabilities of newness, lay a stronger foundation for subsequent growth. Analyzing World Bank Enterprise Survey data across 127 countries, and controlling for other firm performance determinants, registered enterprises that started-up unregistered and spent longer operating unregistered are revealed to have significantly higher subsequent annual sales, employment and productivity growth rates compared with those that registered from the outset. The theoretical and policy implications are then discussed

Industry concentration and strategic trade policy in successive oligopoly

We study a policy game between exporting and importing countries in vertically linked industries. In a successive international Cournot oligopoly, we analyse incentives for using tax instruments strategically to shift rents vertically, between exporting and importing countries, and horizontally, between exporting countries. We show that the equilibrium outcome depends crucially on the relative degree of competitiveness in the upstream and downstream parts of the industry. With respect to national welfare, a more competitive upstream industry may benefit an exporting (upstream) country and harm an importing (downstream) country. On the other hand, a more competitive downstream industry may harm exporting countries.Financial support from the Norwegian Research Council, through the PETROPOL research programme, is gratefully acknowledged. The paper has been greatly improved by the suggestions of two anonymous referees. We also thank Hisashi Hokari and Frode Meland for valuable comments and suggestions

Identifying a gender-inclusive pedagogy from Maltese science teachers' personal practical knowledge

Teachers bring with them into the science classrooms their own gendered identitities and their views and perceptions about how boys and girls learn and achieve in science. This paper tries to explore the way in which fourteen Maltese science teachers use their own 'personal practical knowledge' to identify their views about gender and science and create their own individual gender-inclusive pedagogy. The study suggests that the science teachers focus more on the individuality of students and on the social and cultural background of the students in their classrooms rather than on gender. The teachers try to develop pedagogies and assessment practices which take into consideration the personal constructs of individual learners. The ideas for such a gender-inclusive pedagogy emerge from their common-sense experience in the classroom, their training as teachers and are closely interrelated to current ideas of social constructivism

Retrotransposon instability dominates the acquired mutation landscape of mouse induced pluripotent stem cells.

Induced pluripotent stem cells (iPSCs) can in principle differentiate into any cell of the body, and have revolutionized biomedical research and regenerative medicine. Unlike their human counterparts, mouse iPSCs (miPSCs) are reported to silence transposable elements and prevent transposable element-mediated mutagenesis. Here we apply short-read or Oxford Nanopore Technologies long-read genome sequencing to 38 bulk miPSC lines reprogrammed from 10 parental cell types, and 18 single-cell miPSC clones. While single nucleotide variants and structural variants restricted to miPSCs are rare, we find 83 de novo transposable element insertions, including examples intronic to Brca1 and Dmd. LINE-1 retrotransposons are profoundly hypomethylated in miPSCs, beyond other transposable elements and the genome overall, and harbor alternative protein-coding gene promoters. We show that treatment with the LINE-1 inhibitor lamivudine does not hinder reprogramming and efficiently blocks endogenous retrotransposition, as detected by long-read genome sequencing. These experiments reveal the complete spectrum and potential significance of mutations acquired by miPSCs.Patricia Gerdes, SueMei Lim, AdamD. Ewing, Michael R. Larcombe, Dorothy Chan, Francisco J. Sanchez-Luque, Lucinda Walker, Alexander L. Carleton, Cini James, Anja S. Knaupp, Patricia E. Carreira, Christian M. Nefzger, Ryan Lister, Sandra R. Richardson, Jose M. Polo, Geoffrey J. Faulkne

The PHENIX Experiment at RHIC

The physics emphases of the PHENIX collaboration and the design and current status of the PHENIX detector are discussed. The plan of the collaboration for making the most effective use of the available luminosity in the first years of RHIC operation is also presented.Comment: 5 pages, 1 figure. Further details of the PHENIX physics program available at http://www.rhic.bnl.gov/phenix