Two-dimensional covalent triazine framework as an ultrathin-film nanoporous membrane for desalination

We computationally demonstrate that two-dimensional covalent triazine frameworks (CTFs) provide opportunities in water desalination. By varying the chemical building blocks, the pore structure, chemistry, and membrane performance can be designed, leading to two orders of magnitude higher water permeability than polyamide membranes while maintaining excellent ability to reject salts.Netherlands Organization for Scientific ResearchUnited States. Dept. of Energy (Contract No. DE-AC02-05CH11231)Deshpande Center for Technological Innovatio

Multilayer Nanoporous Graphene Membranes for Water Desalination

While single-layer nanoporous graphene (NPG) has shown promise as a reverse osmosis (RO) desalination membrane, multilayer graphene membranes can be synthesized more economically than the single-layer material. In this work, we build upon the knowledge gained to date toward single-layer graphene to explore how multilayer NPG might serve as a RO membrane in water desalination using classical molecular dynamic simulations. We show that, while multilayer NPG exhibits similarly promising desalination properties to single-layer membranes, their separation performance can be designed by manipulating various configurational variables in the multilayer case. This work establishes an atomic-level understanding of the effects of additional NPG layers, layer separation, and pore alignment on desalination performance, providing useful guidelines for the design of multilayer NPG membranes.National Science Foundation (U.S.) (grant number ACI-1053575)Netherlands Organization for Scientific Research (NWO

Giving to Government: Voluntary Taxation in the Lab

In the United States, there is widespread antipathy toward taxation, yet at the same time there are substantial voluntary donations to nonprofit organizations with missions that are parallel to those of many government agencies. In this paper we compare giving in the form of voluntary taxes paid to government agencies with giving in the form of voluntary donations to nonprofit organizations that have similar missions. In a laboratory experimental setting, subjects are given an endowment, and are given the opportunity to donate any part of the endowment to a government agency or to a nonprofit organization. We compare levels of giving to private and government organizations for four different causes (cancer research, disaster relief, education, and parks and wildlife) at three levels of government (federal, state and local). Within a session, subjects make 12 decisions: they complete all six separate decisions for each of two causes, selected randomly from the four listed above. We find that people are not averse to giving to government. On average, they give 22 percent of their budget to government when anonymity is ensured and giving is completely voluntary. However, they do show a preference for nonprofit charities by giving higher amounts for most causes and levels of government. The willingness to give is influenced by the cause and level of the organization, as well as perceptions of the organization

Heavy particle electroweak loop effects in extra-dimensional models with bulk neutrinos

One way to detect the presence of new particles in theories beyond the standard model is through their contribution to electroweak loop effects. We comment on the importance of a consistent inclusion of their mixing angles to ensure that the physical requirement of heavy particle decoupling is fulfilled. We illustrate our points by a detailed discussion of the lepton flavor changing effect mu-e-gamma, investigated recently by Kitano, in the Randall-Sundrum model. Our remarks are equally applicable to models with large compactified dimensions where bulk neutrinos are introduced to account for the observed neutrino oscillations.Comment: 13 pages; new citations added in Ref [3] and [11

Trapping Penguins with Entangled B Mesons

The first direct observation of time-reversal (T) violation in the $B\bar{B}$ system has been reported by the BaBar collaboration, employing the method of Ba$\tilde {\rm n}\!$uls and Bernab\'eu. Given this, we generalize their analysis of the time-dependent T-violating asymmetry ($A_{T}$) to consider different choices of CP tags for which the dominant amplitudes have the same weak phase. As one application, we find that it is possible to measure departures from the universality of $\sin(2\beta)$ directly. If $\sin(2\beta)$ is universal, as in the Standard Model, the method permits the direct determination of penguin effects in these channels. Our method, although no longer a strict test of T, can yield tests of the $\sin(2\beta)$ universality, or, alternatively, of penguin effects, of much improved precision even with existing data sets.Comment: 11 pages, 2 figures; refs. added; reframed with expanded discussions; version to appear in PLB; Metadata abstract updated onl

Possible evidence for the breakdown of the CKM-paradigm of CP-violation

Using primarily experimental inputs for S(B -> psi Ks), Delta M_Bs, Delta M_Bd, BR(B -> tau nu) and epsilon_K along with necessary inputs from the lattice, we find that the measured value of sin(2 beta) is smaller than expectations of the Standard Model by as much as 3.3 sigma, and also that the measured value of the BR(B -> tau nu) seems to be less than the predicted value by about 2.8 sigma. However, through a critical study we show that most likely the dominant source of these deviations is in B_d(s) mixings and in sin(2 beta) and less so in B -> tau nu, and also that the bulk of the problem persists even if input from epsilon_K is not used. The fact that kaon mixing and epsilon_K are not the dominant source of the deviation from the Standard Model has the very important consequence that model independent considerations imply that the scale of the relevant new CP-violating physics is below O(2 TeV), thus suggesting that direct signals of the new particle(s) may well be accessible in collider experiments at the LHC and perhaps even at the Tevatron.Comment: 6 pages, 8 figures. Added another fit and some more discussion showing that BR(B->tau nu) comes out in good agreement with predictions of the SM if the measured value of sin2beta is not used as an input. References adde

Weak phases from topological-amplitude parametrization

We propose a parametrization for two-body nonleptonic $B$ meson decays, in which the various topologies of amplitudes are counted in terms of powers of the Wolfenstein parameter $\lambda\sim 0.22$. The weak phases and the amplitudes are determined by comparing this parametrization with available measurements. It is possible to obtain the phase $\phi_3$ from the $B\to K\pi$ data up to theoretical uncertainty of $O(\lambda^3)\sim 1$. The recently measured $B_d^0\to\pi^0\pi^0$ branching ratio implies a large color-suppressed or penguin amplitude, and that the extraction of the phase $\phi_2$ from the $B\to\pi\pi$ data may suffer theoretical uncertainty more than the expected one of $O(\lambda^2)\sim 5$.Comment: 11 pages, 4 figure

A consistent picture for large penguins in D -> pi+ pi-, K+ K-

A long-standing puzzle in charm physics is the large difference between the D0 -> K+ K- and D0 -> pi+ pi- decay rates. Recently, the LHCb and CDF collaborations reported a surprisingly large difference between the direct CP asymmetries, Delta A_CP, in these two modes. We show that the two puzzles are naturally related in the Standard Model via s- and d-quark "penguin contractions". Their sum gives rise to Delta A_CP, while their difference contributes to the two branching ratios with opposite sign. Assuming nominal SU(3) breaking, a U-spin fit to the D0 -> K+ pi-, pi+ K-, pi+ pi-, K+ K- decay rates yields large penguin contractions that naturally explain Delta A_CP. Expectations for the individual CP asymmetries are also discussed.Comment: 24 pages, 8 figure

History Assisted View Authoring for 3D Models

3D modelers often wish to showcase their models for sharing or review purposes. This may consist of generating static viewpoints of the model or authoring animated flythroughs. Manually creating such views is often tedious and few automatic methods are designed to interactively assist the modelers with the view authoring process. We present a view authoring assistance system that supports the creation of informative view points, view paths, and view surfaces, allowing modelers to author the interactive navigation experience of a model. The key concept of our implementation is to analyze the model’s workflow history, to infer important regions of the model and representative viewpoints of those areas. An evaluation indicated that the viewpoints generated by our algorithm are comparable to those manually selected by the modeler. In addition, participants of a user study found our system easy to use and effective for authoring viewpoint summaries. Author Keywords 3D model; editing history; viewpoint authorin