A note on Dolby and Gull on radar time and the twin "paradox"

Recently a suggestion has been made that standard textbook representations of hypersurfaces of simultaneity for the travelling twin in the twin "paradox" are incorrect. This suggestion is false: the standard textbooks are in agreement with a proper understanding of the relativity of simultaneity.Comment: LaTeX, 3 pages, 2 figures. Update: added new section V and updated reference

Quantitative Proteomic Analysis of Wheat Cultivars with Differing Drought Stress Tolerance

Using a series of multiplexed experiments we studied the quantitative changes in protein abundance of three Australian bread wheat cultivars (Triticum aestivum L.) in response to a drought stress. Three cultivars differing in their ability to maintain grain yield during drought, Kukri (intolerant), Excalibur (tolerant), and RAC875 (tolerant), were grown in the glasshouse with cyclic drought treatment that mimicked conditions in the field. Proteins were isolated from leaves of mature plants and isobaric tags were used to follow changes in the relative protein abundance of 159 proteins. This is the first shotgun proteomics study in wheat, providing important insights into protein responses to drought as well as identifying the largest number of wheat proteins (1,299) in a single study. The changes in the three cultivars at the different time points reflected their differing physiological responses to drought, with the two drought tolerant varieties (Excalibur and RAC875) differing in their protein responses. Excalibur lacked significant changes in proteins during the initial onset of the water deficit in contrast to RAC875 that had a large number of significant changes. All three cultivars had changes consistent with an increase in oxidative stress metabolism and reactive O2 species (ROS) scavenging capacity seen through increases in superoxide dismutases and catalases as well as ROS avoidance through the decreases in proteins involved in photosynthesis and the Calvin cycle

Childhood Maltreatment Predicts Poor Economic and Educational Outcomes in the Transition to Adulthood.

ObjectivesTo test whether childhood maltreatment was a predictor of (1) having low educational qualifications and (2) not being in education, employment, or training among young adults in the United Kingdom today.MethodsParticipants were from the Environmental Risk (E-Risk) Longitudinal Twin Study, a nationally representative UK cohort of 2232 twins born in 1994 to 1995. Mothers reported on child maltreatment when participants were aged 5, 7, 10, and 12 years. Participants were interviewed about their vocational status at age 18 years.ResultsThe unadjusted odds of having low educational qualifications or of not being in education, employment, or training at age 18 years were more than 2 times greater for young people with a childhood history of maltreatment versus those without. These associations were reduced after adjustments for individual and family characteristics. Youths who reported having a supportive adult in their lives had better education outcomes than did youths who had less support.ConclusionsCloser collaboration between the child welfare and education systems is warranted to improve vocational outcomes for maltreated youths

Abandoned Seabird Eggs as a Calcium Source for Terrestrial Gastropods

Birds’ use of terrestrial gastropods to supplement calcium for egg formation has been well documented, but the reverse, gastropods using avian eggshells as a calcium source, has not been recorded previously. We collected Arctic Tern, Sterna paradisaea, eggs, abandoned in July 2006, that were found to have many terrestrial gastropods on the surface, and it appeared as though the outer eggshell layers were removed. Using scanning electron microscopy, we compared “grazed” and “ungrazed” sections of the same shell with eggshells collected in 2005 that were not attended by snails. It appears as though the snails removed the outer eggshell layers, presumably to supplement their own shell growth

The XRCC1 phosphate-binding pocket binds poly (ADP-ribose) and is required for XRCC1 function

Poly (ADP-ribose) is synthesized at DNA single-strand breaks and can promote the recruitment of the scaffold protein, XRCC1. However, the mechanism and importance of this process has been challenged. To address this issue, we have characterized the mechanism of poly (ADP-ribose) binding by XRCC1 and examined its importance for XRCC1 function. We show that the phosphate-binding pocket in the central BRCT1 domain of XRCC1 is required for selective binding to poly (ADP-ribose) at low levels of ADP-ribosylation, and promotes interaction with cellular PARP1. We also show that the phosphate-binding pocket is required for EGFP-XRCC1 accumulation at DNA damage induced by UVA laser, H2O2, and at sites of sub-nuclear PCNA foci, suggesting that poly (ADP-ribose) promotes XRCC1 recruitment both at single-strand breaks globally across the genome and at sites of DNA replication stress. Finally, we show that the phosphate-binding pocket is required following DNA damage for XRCC1-dependent acceleration of DNA single-strand break repair, DNA base excision repair, and cell survival. These data support the hypothesis that poly (ADP-ribose) synthesis promotes XRCC1 recruitment at DNA damage sites and is important for XRCC1 function