A new chiral electro-optic effect: Sum-frequency generation from optically active liquids in the presence of a dc electric field

We report the observation of sum-frequency signals that depend linearly on an applied electrostatic field and that change sign with the handedness of an optically active solution. This recently predicted chiral electro-optic effect exists in the electric-dipole approximation. The static electric field gives rise to an electric-field-induced sum-frequency signal (an achiral third-order process) that interferes with the chirality-specific sum-frequency at second-order. The cross-terms linear in the electrostatic field constitute the effect and may be used to determine the absolute sign of second- and third-order nonlinear optical susceptibilities in isotropic media.Comment: Submitted to Physical Revie

Dimensional analysis using toric ideals: Primitive invariants

© 2014 Atherton et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Classical dimensional analysis in its original form starts by expressing the units for derived quantities, such as force, in terms of power products of basic units M, L, T etc. This suggests the use of toric ideal theory from algebraic geometry. Within this the Graver basis provides a unique primitive basis in a well-defined sense, which typically has more terms than the standard Buckingham approach. Some textbook examples are revisited and the full set of primitive invariants found. First, a worked example based on convection is introduced to recall the Buckingham method, but using computer algebra to obtain an integer K matrix from the initial integer A matrix holding the exponents for the derived quantities. The K matrix defines the dimensionless variables. But, rather than this integer linear algebra approach it is shown how, by staying with the power product representation, the full set of invariants (dimensionless groups) is obtained directly from the toric ideal defined by A. One candidate for the set of invariants is a simple basis of the toric ideal. This, although larger than the rank of K, is typically not unique. However, the alternative Graver basis is unique and defines a maximal set of invariants, which are primitive in a simple sense. In addition to the running example four examples are taken from: a windmill, convection, electrodynamics and the hydrogen atom. The method reveals some named invariants. A selection of computer algebra packages is used to show the considerable ease with which both a simple basis and a Graver basis can be found.The third author received funding from Leverhulme Trust Emeritus Fellowship (1-SST-U445) and United Kingdom EPSRC grant: MUCM EP/D049993/1

Flow field prediction and analysis, project fire final report

Flow field, and convective and radiative heating predictions for NASA Fire project reentry package trajectorie

Geochemical and spectral characterization of naturally altered rock surfaces

The possibility of using the visible-near infrared region for compositional analysis of remotely sensed rock surfaces is studied. This would allow mapping rock type both on the Earth's surface and on other planetary surfaces. Reflectance spectroscopy, economic geology, optical depth determination, and X-ray diffraction mineralogy are discussed

Influence of damping on the vanishing of the electro-optic effect in chiral isotropic media

Using first principles, it is demonstrated that radiative damping alone cannot lead to a nonvanishing electro-optic effect in a chiral isotropic medium. This conclusion is in contrast with that obtained by a calculation in which damping effects are included using the standard phenomenological model. We show that these predictions differ because the phenomenological damping equations are valid only in regions where the frequencies of the applied electromagnetic fields are nearly resonant with the atomic transitions. We also show that collisional damping can lead to a nonvanishing electrooptic effect, but with a strength sufficiently weak that it is unlikely to be observable under realistic laboratory conditions

Influence of radiative damping on the optical-frequency susceptibility

Motivated by recent discussions concerning the manner in which damping appears in the electric polarizability, we show that (a) there is a dependence of the nonresonant contribution on the damping and that (b) the damping enters according to the "opposite sign prescription." We also discuss the related question of how the damping rates in the polarizability are related to energy-level decay rates

Investigation of Pitot tubes

Report describes the principles of operation and characteristics of some of the instruments which have been devised or used to measure both low and high speeds of aeroplanes. Since the pitot tube is the instrument which has been most commonly used in the United States and Great Britain as a speedometer for aeroplanes, it is treated first and somewhat more fully than the others

Problems and Prospects of Developing Countries in Forestry and Wood-Processing Industries. Report from an IIASA/UNIDO Workshop

This paper reports in a summary form on the discussions during a workshop organized by IIASA and UNIDO in January 1983. The workshop treated problems and prospects relating to developing countries in the sectors of forestry and wood-processing industries. The results of the workshop will be used in IIASA's project "Structural Change in the Forest Sector" and in UNIDO's work on its world-wide study on wood and wood processing industries. The invited participants came mainly from developing countries and from the two institutions mentioned. The issues raised during the meeting are summarized systematically in Figure 2. The main concern of the meeting related to the sustainability of the wood resources, over-exploitation and depletion and suitable counter-balancing measures, such as afforestation, reforestation, and more efficient use of available resources. Trade patterns were also discussed. A global trade model for forestry industry products was presented