Note on the calculation of transport properties of gas mixtures

As a result of recent theoretical studies on transport properties of gases by Hirschfelder, et al., and others, the dynamic viscosity (µ), the thermal conductivity (λ), and the mechanical diffusivity (D), as well as the dimensionless ratios Prandtl Number (Pr = C_p µ/λ, where C_p = specific heat at constant pressure), Schmidt Number (Sc =µ/ρD, where ρ = density), anq λ/ρC_pD may now be calculated rapidly and with a reasonable degree of accuracy both for pure gases and for mixtures of gases, provided that the temperature of the gases is not too low. This happy state of affairs does not seem to be realized by aeronautical engineers, and it is the purpose of the present note to call attention to it

The mechanics of film cooling-Part 1

Thin liquid wall films flowing under the influence of high-velocity turbulent gas streams were studied for the purpose of obtaining an understanding of the mechanics of film cooling. Conditions which insure liquid-film attachment to solid surfaces without loss of unevaporated liquid to the gas stream when simple radial-hole injectors are used were found; the maximum allowable coolant flow rate for a stable coolant film was determined (a stable coolant film is obtained when no unevaporated coolant is entrained by the gas stream as the result of interfacial disturbances); and a method for calculating the evaporation rate and the surface temperature for a stable inert coolant film was found

Theoretical Study of Electrical Conduction Through a Molecule Connected to Metallic Nanocontacts

We present a theoretical study of electron transport through a molecule connected to two metallic nanocontacts. The system investigated is 1,4 benzene-dithiolate (BDT) chemically bonded to two Au contacts. The surface chemistry is modeled by representing the tips of the Au contacts as two atomic clusters and treating the molecule-cluster complex as a single entity in an extended Huckel tight binding scheme. We model the tips using several different cluster geometries. An ideal lead is attached to each cluster, and the lead to lead transmission is calculated. The role of the molecule-cluster interaction in transport is analyzed by using single channel leads. We then extend the calculations to multi-channel leads that are a more realistic model of the tip's environment. Using the finite-voltage, finite temperature Landauer formula, we calculate the differential conductance for the different systems studied. The similarities and differences between the predictions of the present class of models and recent experimental work are discussed.Comment: 23 pages, 11 figures, accepted PR

UNIVERSITY ASSISTANCE IN BUILDING AGRICULTURAL RESEARCH INSTITUTIONS IN SOUTHEAST ASIA - A CASE ANALYSIS

Public Economics,

The gene complement of the ancestral bilaterian - was Urbilateria a monster?

Expressed sequence tag analyses of the annelid Pomatoceros lamarckii, recently published in BMC Evolutionary Biology, are consistent with less extensive gene loss in the Lophotrochozoa than in the Ecdysozoa, but it would be premature to generalize about patterns of gene loss on the basis of the limited data available