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Volume 26(9);  September 15, 1940
Astronomy
A Note on the Variation of Delta Scuti
Theodore Eugene Sterne
Proc Natl Acad Sci U S A. 1940 September 15; 26(9): 537–541.
PMCID: PMC1078225
Galactic and Extragalactic Studies: VIII. A New Determination of the Period-Luminosity Curve
Harlow Shapley
Proc Natl Acad Sci U S A. 1940 September 15; 26(9): 541–548.
PMCID: PMC1078226
The Spectrum of BD +30°3639
P. Swings and O. Struve
Proc Natl Acad Sci U S A. 1940 September 15; 26(9): 548–553.
PMCID: PMC1078227
Galactic and Extragalactic Studies: IX. A Photometric Survey of 22,000 Galaxies in the Zone from δ = +41° to δ = +46°
Harlow Shapley and Rebecca B. Jones
Proc Natl Acad Sci U S A. 1940 September 15; 26(9): 554–561.
PMCID: PMC1078228
Botany
Synthesis of Thiamin by Excised Roots of Maize
J. Edward McClary
Proc Natl Acad Sci U S A. 1940 September 15; 26(9): 581–587.
PMCID: PMC1078235
Chemistry
Inhibition of Carboxylase by Thiazole Pyrophosphate
Edwin R. Buchman, Erik Heegaard, and James Bonner
Proc Natl Acad Sci U S A. 1940 September 15; 26(9): 561–563.
PMCID: PMC1078229
Genetics
THE EFFECT OF FAST NEUTRONS ON THE CHROMOSOMES OF TRADESCANTIA
Norman Giles
Proc Natl Acad Sci U S A. 1940 September 15; 26(9): 567–575.
PMCID: PMC1078232
CHROMOSOME HOMOLOGIES IN TWO SUB-SPECIES OF DROSOPHILA VIRILIS
Harrison D. Stalker
Proc Natl Acad Sci U S A. 1940 September 15; 26(9): 575–578.
PMCID: PMC1078233
LINKAGE STUDIES OF THE RAT (RATTUS NORVEGICUS): III
W. E. Castle and Helen Dean King
Proc Natl Acad Sci U S A. 1940 September 15; 26(9): 578–580.
PMCID: PMC1078234
Mathematics
On Homotopy Groups
Samuel Eilenberg
Proc Natl Acad Sci U S A. 1940 September 15; 26(9): 563–565.
PMCID: PMC1078230
Physics
On a General Rule Concerning the Half-Value Periods of Electron-Emitting Nuclei
Arthur E. Haas
Proc Natl Acad Sci U S A. 1940 September 15; 26(9): 565–567.
PMCID: PMC1078231
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