The second and third dielectric virial coefficients of 4He have been measured by the symmetrical gasexpansion technique of Buckingham, Cole and Sutter for six isotherms between 3,OO K and 17,68 K. The effects of helium adsorption are important, and are considered in detail. No temperature dependence of the second coefficient is seen at a level of 6b= &0,008 cm3mol-', and average values of the second and third coefficients are b = 0,006 (10) cm3 mol-and c = -5 (4) cm6 mol-', respectively. The uncertainty for b is relatively large because it has a systematic dependence on c: reanalysis of all the existing data shows that a more probable value of the third coefficient is c= -2 (1) cm6mol-', which when combined with our data gives b ( 3 K -18 K)= -0,001 (4) cm-,mol-'. The very small value suggests that theoretical calculations of the excess polarizability of the helium diatom need to be reconsidered. The small value and the small uncertainty of b indicate that future work to improve experimental values of the second density virial coefficient of 4He for this temperature range may without ambiguity make use of the methods of dielectric constant gas thermometry.

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Background The radial forearm free flap has classically been used in oral reconstructions, however, there has been research into an alternative option, the nasolabial flap. Surgical research is focussing more on quality-of-life outcomes to measure a successful recovery. Therefore, this review has a focus on QOL as well as functional outcomes. Aim To determine if there are better QOL outcomes between patients undergoing tongue reconstruction with the NLF or the RFFF. The quality and limitations of the included papers will be discussed. Method Four databases were searched using set search terms and inclusion/exclusion criteria. Fourteen final papers were assessed using a CASP checklist and a bias tool. Results Four papers lost patients to follow-up; one provided no information, and one excluded three patients from follow-up, leaving nine papers with complete follow-up data. Eight studies used subjective measurements for functional outcomes; two used objectives; three used both; and one study used objective measurements for speech, but no information was provided for swallowing. A variety of outcome measures were featured; despite this, all the papers found good functional and QOL results at follow-up. There were problems with bias throughout all the papers and several reoccurring limitations such as small sample size and the retrospective nature of all but one study. Conclusions Due to the significant amount of bias found, the low quality of literature available, and discrepancies between outcome measures, further research is needed in the form of a long-term prospective study with a larger cohort that includes some objective outcome measures.