Tumour angiogenesis: the gap between theory and experiments.

A common experimental technique for viewing in vivo angiogenesis utilises tumours implanted into a test animal cornea. The cornea is avascular but the tumour promotes vascularisation from the limbus and the new blood vessels can be readily observed through the transparent cornea. Many of the early mathematical models for tumour angiogenesis used this scenario as their experimental template and as such assumed that there is a large gap, of the order of 2mm, between the tumour and neighbouring vasculature at the onset of angiogenesis. In this work we consider whether the assumption that there is a significant gap between the tumour and neighbouring vasculature is unique to intra-cornea tumour implants, or whether this characterises avascular tumour growth more generally. To do this we utilise a simple scaling argument, derive a multi-compartment model for tumour growth, and consider in vivo images. This analysis demonstrates that the corneal implant experiments and the corresponding mathematical models cannot generally be applied to a clinical setting.

Racial and behavioral cues in black and white children's perceptions of ambiguously aggressive acts.

To explore the way in which the interpretation of ambiguous social behavior can be influenced by racial stereotypes and cultural differences, 40 black and 40 white 6th-grade males were shown a variety of ambiguously aggressive behaviors performed by black and white stimulus figures. As predicted, both black and white preadolescents rated these behaviors as more mean and threatening when the perpetrator was black than when he was white. In contrast, rating of personal characteristics were in general determined by individual behavior rather than by group stereotypes, although blacks, whether they were the perpetrator or the recipient of the behaviors, were rated as stronger than their white counnterparts. Cultural differences between subject groups were apparent in the greater tendency of the white children to read threat into ambiguously aggressive behaviors involving no physical contact and to assume that the perpetrators of such behaviors were stronger than the recipients.

An exploratory study of the draw-a-person as a measure of racial identity.

The race of the figure drawn on the Draw-A-Person Test is proposed as a measure of acceptance of racial identity. Reliability and validity of this measure were explored in a two-part study. Part 1 confirmed the hypothesis that the race of the figure drawn is related to the race of the child producing the drawing. Comparison of the figures drawn by black (n = 157) and white (n = 167) children confirmed three other hypotheses based on the voluminous literature suggesting that black children are less accepting of their racial group membership than whites. These hypotheses were: (a) whites should be more likely to draw figures that are clearly white than blacks are to draw figures that are clearly black, (b) whites should be less likely to draw blacks than blacks are to draw whites, and (c) blacks should be more likely to avoid giving clear indication of the race of the figures they draw than are whites. Inter-rater reliability for the race of the figure drawn was .79. Five weeks after the initial drawing, a subsample of 28 black children drew a second figure and performed a picture choice task designed to assess acceptance of racial identity. The race of the figure drawn showed a test-retest reliability of .53 and correlated significantly with the other measure of racial identity (r27 = .39).

Field-compensated michelson spectrometers.

It was first shown by Pierre Connes (1956) that the resolution-luminosity product of a Michelson spec- trometer could be substantially improved by the technique of field compensation. In the present paper, various systems of field compensation are discussed, and an account is given of the tolerances allowed in their operation, together with their areas of usefulness.