Group and phase velocity mismatch fringes in triple sum-frequency spectroscopy

The effects of group and phase velocity mismatch are well-known in optical harmonic generation, but the non-degenerate cases remain unexplored. In this work we develop an analytic model which predicts velocity mismatch effects in non-degenerate triple sum-frequency mixing, TSF. We verify this model experimentally using two tunable, ultrafast, short-wave-IR lasers to demonstrate spectral fringes in the TSF output from a 500 $\mu$m thick sapphire plate. We find the spectral dependence of the TSF depends strongly on both the phase velocity and the group velocity differences between the input and output fields. We define practical strategies for mitigating the impact of velocity mismatches

The Inclusive-Exclusive Connection and the Neutron Negative Central Charge Density

We find an interpretation of the recent finding that the central charge density of the neutron is negative by using models of generalized parton distributions at zero skewness to relate the behavior of deep inelastic scattering quark distributions, evaluated at large values of Bjorken x, to the transverse charge density evaluated at small distances. The key physical input of these models is the Drell-Yan-West relation We find that the d quarks dominate the neutron structure function for large values of Bjorken x, where the large longitudinal momentum of the struck quark has a significant impact on determining the center-of-momentum of the system, and thus the "center" of the nucleon in the transverse position plane.Comment: 17 pages, 8 figures. Text of an invited talk presented by G. A. Miller at the 2008 Division of Nuclear Physics Meeting in Oakland. Prepared for Int. Journ. Mod. Phys.

A tool to aid redesign of flexible transport services to increase efficiency in rural transport service provision

This research was supported by the Research Councils UK Digital Economy programme award (reference: EP/G066051/1) to the dot.rural Digital Economy Hub, at the University of Aberdeen.Peer reviewedPublisher PD

Estimating the Long-term Contributions of Small Buisness Marketing Expenditures

While small business owners and managers typically recognize the long-term benefits of many types of capital expenditures, the potential long-term benefits of marketing expenditures are frequently overlooked. This situation is true even though expenditures on marketing frequently yield sales revenue to firms over several periods. This paper introduces and examines three relatively low-cost approaches that small business owners may use as aids in estimating the aggregate value of marketing expenditures

Process Upsets Involving Trace Contaminant Control Systems

Paradoxically, trace contaminant control systems that suffer unexpected upsets and malfunctions can release hazardous gaseous contaminants into a spacecraft cabin atmosphere causing potentially serious toxicological problems. Trace contaminant control systems designed for spaceflight typically employ a combination of adsorption beds and catalytic oxidation reactors to remove organic and inorganic trace contaminants from the cabin atmosphere. Interestingly, the same design features and attributes which make these systems so effective for purifying a spacecraft's atmosphere can also make them susceptible to system upsets. Cabin conditions can be contributing causes of phenomena such as adsorbent "rollover" and catalyst poisoning can alter a systems performance and in some in stances release contamination into the cabin. Evidence of these phenomena has been observed both in flight and during ground-based tests. The following discussion describes specific instances of system upsets found in trace contaminant control systems, groups these specific upsets into general hazard classifications, and recommends ways to minimize these hazards