Internal Gravity Waves Modulate the Apparent Misalignment of Exoplanets around Hot Stars

We propose that the observed misalignment between extra-solar planets and their hot host stars can be explained by angular momentum transport within the host star. Observations have shown that this misalignment is preferentially around hot stars, which have convective cores and extended radiative envelopes. This situation is amenable to substantial angular momentum transport by internal gravity waves (IGW) generated at the convective-radiative interface. Here we present numerical simulations of this process and show that IGW can modulate the surface rotation of the star. With these two- dimensional simulations we show that IGW could explain the retrograde orbits observed in systems such as HAT-P-6 and HAT-P-7, however, extension to high obliquity objects will await future three- dimensional simulations. We note that these results also imply that individual massive stars should show temporal variations in their v sini measurements.Comment: 6 pages, 2 figures, Accepted for publication in ApJ

InGaAsP p-i-n photodiodes for optical communication at the 1.3-µm wavelength

The preparation and properties of Cd-diffused p-n homojunction InGaAsP photodiodes designed specifically for operation at the 1.3-µm wavelength are described. At a reverse bias of 10 V, the dark current of these diodes was as low as 15 pA. The peak responsivity at 1.3-µm wavelength was 0.7 A/W. An impulse response (full width at half maximum) of 60 ps and a 3-dB bandwidth of 5.5 GHz were achieved.

Medium: An exploratory study of PR professionals in Taiwan

This paper seeks to explore the attitudes and practices of public relations (PR) professionals in using the Internet as a PR medium in Taiwan. Specifically, the paper addresses three research questions: (1) What do PR professionals think about the function of the Internet and the roles of online communication in comparison with those of offline communication in Taiwan? (2) Will IT-related corporations be more likely to have a wider scope of Internet applications than non-IT related corporations? (3) Do IT corporations perceive the role of PR differently from non-IT related corporations? Using a semi-structured questionnaire, we conducted in-depth interviews with eight corporations’ PR and marketing department professionals in Taiwan from May 18- June 18, 2001. The findings show that (1) Although the Internet is widely used by PR professionals, it does not alter media strategies significantly; (2) PR professionals in IT corporations tend to practise more Internet communication functions than those in non-IT related corporations; (3) IT corporations are more likely to support the management role of PR professionals, as compared to those in non-IT related businesses. The study suggests that the applications of the Internet vary according to industry type, business strategies and roles of the PR professionals within an organisation

Electrical Transport in High Quality Graphene pnp Junctions

We fabricate and investigate high quality graphene devices with contactless, suspended top gates, and demonstrate formation of graphene pnp junctions with tunable polarity and doping levels. The device resistance displays distinct oscillations in the npn regime, arising from the Fabry-Perot interference of holes between the two pn interfaces. At high magnetic fields, we observe well-defined quantum Hall plateaus, which can be satisfactorily fit to theoretical calculations based on the aspect ratio of the device.Comment: to appear in a special focus issue in New Journal of Physic

An Assessment of the Impact of the 1997-98 El Nino on the Asian-Australian Monsoon

Using state-of-the-art satellite-gauge monthly rainfall estimate and optimally interpolated sea surface temperature (SST) data, we have assessed the 1997-98 AA-monsoon anomalies in terms of three basic causal factors: basin-scale SST, regional coupling, and internal variability. Singular Value Decomposition analyses of rainfall and SST are carried out globally over the entire tropics and regionally over the AA-monsoon domain. Contributions to monsoon rainfall predictability by various factors are evaluated from cumulative anomaly correlation with dominant regional SVD modes. Results reveal a dominant, large-scale monsoon-El Nino coupled mode with well-defined centers of action in the near-equatorial monsoon regions during the boreal summer and winter respectively. The observed 1997-98 AA-monsoon anomalies are found to be very complex with approximately 34% of the anomalies of the Asian (boreal) summer monsoon and 74% of the Australia (austral) monsoon attributable to basin-scale SST influence associated with El Nino. Regional coupled processes contribute an additional 19% and 10%, leaving about 47% and 16% due to internal dynamics for the boreal and austral monsoon respectively. For the boreal summer monsoon, it is noted that the highest monsoon predictability is not necessary associated with major El Nino events (e.g. 1997, 1982) but rather in non-El Nino years (e.g. 1980, 1988) when contributions from the regional coupled modes far exceed those from the basin-scale SST. The results suggest that in order to improve monsoon seasonal-to-interannual predictability, there is a need to exploit not only monsoon-El Nino relationship, but also intrinsic monsoon regional coupled processes

Lagrangian Floer superpotentials and crepant resolutions for toric orbifolds

We investigate the relationship between the Lagrangian Floer superpotentials for a toric orbifold and its toric crepant resolutions. More specifically, we study an open string version of the crepant resolution conjecture (CRC) which states that the Lagrangian Floer superpotential of a Gorenstein toric orbifold $\mathcal{X}$ and that of its toric crepant resolution $Y$ coincide after analytic continuation of quantum parameters and a change of variables. Relating this conjecture with the closed CRC, we find that the change of variable formula which appears in closed CRC can be explained by relations between open (orbifold) Gromov-Witten invariants. We also discover a geometric explanation (in terms of virtual counting of stable orbi-discs) for the specialization of quantum parameters to roots of unity which appears in Y. Ruan's original CRC ["The cohomology ring of crepant resolutions of orbifolds", Gromov-Witten theory of spin curves and orbifolds, 117-126, Contemp. Math., 403, Amer. Math. Soc., Providence, RI, 2006]. We prove the open CRC for the weighted projective spaces $\mathcal{X}=\mathbb{P}(1,\ldots,1,n)$ using an equality between open and closed orbifold Gromov-Witten invariants. Along the way, we also prove an open mirror theorem for these toric orbifolds.Comment: 48 pages, 1 figure; v2: references added and updated, final version, to appear in CM