The complex geometry of holographic flows of quiver gauge theories

We argue that the complete Klebanov-Witten flow solution must be described by a Calabi-Yau metric on the conifold, interpolating between the orbifold at infinity and the cone over T^(1,1) in the interior. We show that the complete flow solution is characterized completely by a single, simple, quasi-linear, second order PDE, or "master equation," in two variables. We show that the Pilch-Warner flow solution is almost Calabi-Yau: It has a complex structure, a hermitian metric, and a holomorphic (3,0)-form that is a square root of the volume form. It is, however, not Kahler. We discuss the relationship between the master equation derived here for Calabi-Yau geometries and such equations encountered elsewhere and that govern supersymmetric backgrounds with multiple, independent fluxes.Comment: 26 pages, harvmac + amssy

Gate Coupling to Nanoscale Electronics

The realization of single-molecule electronic devices, in which a nanometer-scale molecule is connected to macroscopic leads, requires the reproducible production of highly ordered nanoscale gaps in which a molecule of interest is electrostatically coupled to nearby gate electrodes. Understanding how the molecule-gate coupling depends on key parameters is crucial for the development of high-performance devices. Here we directly address this, presenting two- and three-dimensional finite-element electrostatic simulations of the electrode geometries formed using emerging fabrication techniques. We quantify the gate coupling intrinsic to these devices, exploring the roles of parameters believed to be relevant to such devices. These include the thickness and nature of the dielectric used, and the gate screening due to different device geometries. On the singlemolecule ( ~ 1 nm) scale, we find that device geometry plays a greater role in the gate coupling than the dielectric constant or the thickness of the insulator. Compared to the typical uniform nanogap electrode geometry envisioned, we find that nonuniform tapered electrodes yield a significant 3 orders of magnitude improvement in gate coupling. We also find that in the tapered geometry the polarizability of a molecular channel works to enhance the gate coupling

Gate Coupling to Nanoscale Electronics

The realization of single-molecule electronic devices, in which a nanometer-scale molecule is connected to macroscopic leads, requires the reproducible production of highly ordered nanoscale gaps in which a molecule of interest is electrostatically coupled to nearby gate electrodes. Understanding how the molecule-gate coupling depends on key parameters is crucial for the development of high-performance devices. Here we directly address this, presenting two- and three-dimensional finite-element electrostatic simulations of the electrode geometries formed using emerging fabrication techniques. We quantify the gate coupling intrinsic to these devices, exploring the roles of parameters believed to be relevant to such devices. These include the thickness and nature of the dielectric used, and the gate screening due to different device geometries. On the single-molecule (~1nm) scale, we find that device geometry plays a greater role in the gate coupling than the dielectric constant or the thickness of the insulator. Compared to the typical uniform nanogap electrode geometry envisioned, we find that non-uniform tapered electrodes yield a significant three orders of magnitude improvement in gate coupling. We also find that in the tapered geometry the polarizability of a molecular channel works to enhance the gate coupling

Towards a gauge invariant volume-weighted probability measure for eternal inflation

An improved volume-weighted probability measure for eternal inflation is proposed. For the models studied in this paper it leads to simple and intuitively expected gauge-invariant results.Comment: 16 pages, 3 figs, few misprints corrected, comments adde

Dual Actions for Born-Infeld and Dp-Brane Theories

Dual actions with respect to U(1) gauge fields for Born-Infeld and $Dp$-brane theories are reexamined. Taking into account an additional condition, i.e. a corollary to the field equation of the auxiliary metric, one obtains an alternative dual action that does not involve the infinite power series in the auxiliary metric given by ref. \cite{s14}, but just picks out the first term from the series formally. New effective interactions of the theories are revealed. That is, the new dual action gives rise to an effective interaction in terms of one interaction term rather than infinite terms of different (higher) orders of interactions physically. However, the price paid for eliminating the infinite power series is that the new action is not quadratic but highly nonlinear in the Hodge dual of a $(p-1)$-form field strength. This non-linearity is inevitable to the requirement the two dual actions are equivalent.Comment: v1: 11 pages, no figures; v2: explanation of effective interactions added; v3: concision made; v4: minor modification mad

Neoplasia at 10-year follow-up screening colonoscopy in a private U.S. practice: comparison of yield to first-time examinations

Background and Aims Prior studies assessing the yield of a second screening colonoscopy performed 10 years after an initial negative screening colonoscopy did not include a control group of persons undergoing their first screening colonoscopy during the same time interval. Our aim was to describe the incidence of neoplasia at a second screening colonoscopy (performed at least 8 years after the first colonoscopy) in average risk individuals and compare it with the yield of first screening examinations performed during the same time interval. Methods Review of a database of outpatient screening colonoscopies performed between January 2010 and December 2015 in an Atlanta private practice. Results A total of 2105 average risk individuals underwent screening colonoscopy, including 470 individuals (53.6% female; mean age 64.0 ± 3.9 years) who underwent a second screening examination. In those undergoing second screening, the mean interval between examinations was 10.4 years (±1.1; range 8-15 years). At second screening, the polyp detection rate (PDR), adenoma detection rate (ADR) and advanced neoplasm rate (ANR) were 44.7%, 26.6%, and 7.4%, respectively. Of 40 advanced neoplasms in 35 individuals, 33 (82.5%) were proximal to the sigmoid colon, and there were no cancers. During the same interval, 1635 individuals (49.4% female; mean age 52.6 ± 3.4 years) underwent their first screening colonoscopy. The PDR, ADR and ANR were 53.5%, 32.2%, and 11.7%, respectively. Of 243 advanced neoplasms in 192 individuals, 152 (62.6%) were proximal to the sigmoid colon, and there were no cancers. After adjustment for age, gender, body mass index, and endoscopist, PDR, ADR, and ANR were all lower at the second screening colonoscopies than at first-time colonoscopies (all p<0.001). Conclusions Despite being 10 years older, persons with a negative screening colonoscopy 10 years earlier had numerically lower rates of adenomas and advanced neoplasms at their second screening examination compared with patients in the same practice undergoing their first screening colonoscopy, and they had no cancers. The fraction of advanced neoplasms that were proximal to the sigmoid was high in both first and second screenings. These results support the safety of the recommended 10-year interval between colonoscopies in average risk persons with an initial negative examination

The Enhancon, Black Holes, and the Second Law

We revisit the physics of five-dimensional black holes constructed from D5- and D1-branes and momentum modes in type IIB string theory compactified on K3. Since these black holes incorporate D5-branes wrapped on K3, an enhancon locus appears in the spacetime geometry. With a `small' number of D1-branes, the entropy of a black hole is maximised by including precisely half as many D5-branes as there are D1-branes in the black hole. Any attempts to introduce more D5-branes, and so reduce the entropy, are thwarted by the appearance of the enhancon locus above the horizon, which then prevents their approach. The enhancon mechanism thereby acts to uphold the Second Law of Thermodynamics. This result generalises: For each type of bound state object which can be made of both types of brane, we show that a new type of enhancon exists at successively smaller radii in the geometry, again acting to prevent any reduction of the entropy just when needed. We briefly explore the appearance of the enhancon in the black hole interior.Comment: 22 pages, 2 figures, latex, epsfig (v2: Fixed trivial typos.

Direct characterisation of tuneable few-femtosecond dispersive-wave pulses in the deep UV

Dispersive wave emission (DWE) in gas-filled hollow-core dielectric waveguides is a promising source of tuneable coherent and broadband radiation, but so far the generation of few-femtosecond pulses using this technique has not been demonstrated. Using in-vacuum frequency-resolved optical gating, we directly characterise tuneable 3fs pulses in the deep ultraviolet generated via DWE. Through numerical simulations, we identify that the use of a pressure gradient in the waveguide is critical for the generation of short pulses.Comment: 5 pages, 4 figure

Public Price Reporting, Marketing Channel Selection, and Price Discovery: The Perspective of Cow/Calf Producers in the Dakotas

Cow/calf producers operating in the Dakotas were surveyed on their price discovery strategies, marketing channel preferences, and their perceptions of how regime change in the public price reporting system for fed cattle affected the beef industry in general and the cow/calf industry in particular. Survey results indicate cow/calf producers consider local institutions (auction barns, etc.) to be more reliable for price discovery than regional or national institutions (futures market, USDA public price reports, satellite auctions, etc.). The auction barn marketing channel is the preferred channel for marketing cattle and is considered the most reliable source of market information by producers. Dakota cow/calf producers perceive livestock mandatory price reporting as benefiting the beef industry in general, but consider public price reports to be less reliable than local sources of market information.beef supply chain, cow-calf marketing, marketing channel, price discovery, public price reporting, Livestock Production/Industries,