ALBERT

Description: Although recent decades have been the warmest since 1850, and global mean temperatures during 2015 and 2016 beat all instrumental records, the rate of increase in global surface air temperature (GSAT) significantly decreased at the beginning of the 21st Century. In this context, we examine the roles of ice melting and associated increase in sea-water mass, both of which significantly increased at the same time as GSAT decreased. Specifically, we show that (1) the slowdown of the rate of increase in GSAT between the specific periods 1992–2001 and 2002–2011 exists in all three climate records analyzed and is statistically significant at the 5% level amounting between 0.029 and 0. 036 °C/yr and leaving an energy of 14.8 to 18.4 10 19  J/yr available; (2) the increase of the atmosphere-related ice melt between these two periods amounts to 316 Gt/yr which requires 10.5 10 19  J/yr, i.e. between 57% and 71 % of the energy left by the slowdown; and (3) the energy budget shows therefore that the heat required to melt this additional 316 Gt/yr of ice is of the same order as the energy needed to warm the atmosphere during the decade 2002–2011 as much as during the previous one, suggesting a redistribution of heat within the atmosphere-cryosphere system.

Description: As genes originate at different evolutionary times, they harbor distinctive genomic signatures of evolutionary ages. Although previous studies have investigated different gene age-related signatures, what signatures dominantly associate with gene age remains unresolved. Here we address this question via a combined approach of comprehensive assignment of gene ages, gene family identification, and multivariate analyses. We first provide a comprehensive and improved gene age assignment by combining homolog clustering with phylogeny inference and categorize human genes into 26 age classes spanning the whole tree of life. We then explore the dominant age-related signatures based on a collection of 10 potential signatures (including gene composition, gene length, selection pressure, expression level, connectivity in protein–protein interaction network and DNA methylation). Our results show that GC content and connectivity in protein–protein interaction network (PPIN) associate dominantly with gene age. Furthermore, we investigate the heterogeneity of dominant signatures in duplicates and singletons. We find that GC content is a consistent primary factor of gene age in duplicates and singletons, whereas PPIN is more strongly associated with gene age in singletons than in duplicates. Taken together, GC content and PPIN are two dominant signatures in close association with gene age, exhibiting heterogeneity in duplicates and singletons and presumably reflecting complex differential interplays between natural selection and mutation.

Description: Differential acoustic resonance spectroscopy (DARS) was developed to examine changes in the resonant frequencies of a cavity perturbed by the introduction of a centimetre-sized sample. Resonant frequency shifts, measured at different resonance modes and between empty and sample-loaded cavities, were used to infer the acoustic properties of the loaded samples in the low frequency range (0.5–2 kHz). To some extent, this laboratory-based measurement technique fills an experimental gap between the low-frequency stress–strain method (quasi-static to several kHz) and the ultrasonic transmission technique (hundreds of kHz to MHz). By means of an effective perturbation model against the DARS system, this study presents a Green's function-based theoretical derivation of an amended DARS perturbation formula under a general impedance boundary condition. Numerical and experimental results show that the amended DARS perturbation is able to reflect the DARS operation mechanism more accurately and more precisely than past efforts. In addition, inversion was performed by fitting the resonance frequencies, measured at various locations inside the DARS resonance cavity, in a least-square sense to estimate the acoustic properties of a test sample. Inversion implementation at different resonance modes makes it possible to perform direct dispersion analysis on reservoir rocks at different low-frequency bands. The results of this study show that the DARS laboratory device, in conjunction with the amended perturbation formula and the proposed inversion strategy, are useful tools for estimating the acoustic properties of centimetre-sized rock samples in the low frequency range.