Context. Deep far-infrared (FIR) cosmological surveys are known to be affected by source confusion, causing issues when examining the main sequence (MS) of star forming galaxies. In the past this has ...typically been partially tackled by the use of stacking. However, stacking only provides the average properties of the objects in the stack. Aims. This work aims to trace the MS over 0.2 ≤ z < 6.0 using the latest de-blended Herschel photometry, which reaches ≈10 times deeper than the 5σ confusion limit in SPIRE. This provides more reliable star formation rates (SFRs), especially for the fainter galaxies, and hence a more reliable MS. Methods. We built a pipeline that uses the spectral energy distribution (SED) modelling and fitting tool CIGALE to generate flux density priors in the Herschel SPIRE bands. These priors were then fed into the de-blending tool XID+ to extract flux densities from the SPIRE maps. In the final step, multi-wavelength data were combined with the extracted SPIRE flux densities to constrain SEDs and provide stellar mass (M⋆) and SFRs. These M⋆ and SFRs were then used to populate the SFR-M⋆ plane over 0.2 ≤ z < 6.0. Results. No significant evidence of a high-mass turn-over was found; the best fit is thus a simple two-parameter power law of the form log(SFR) = αlog(M⋆) − 10.5 + β. The normalisation of the power law increases with redshift, rapidly at z ≲ 1.8, from 0.58 ± 0.09 at z ≈ 0.37 to 1.31 ± 0.08 at z ≈ 1.8. The slope is also found to increase with redshift, perhaps with an excess around 1.8 ≤ z < 2.9. Conclusions. The increasing slope indicates that galaxies become more self-similar as redshift increases. This implies that the specific SFR of high-mass galaxies increases with redshift, from 0.2 to 6.0, becoming closer to that of low-mass galaxies. The excess in the slope at 1.8 ≤ z < 2.9, if present, coincides with the peak of the cosmic star formation history.
In an empirical analysis of transposable element (TE) abundance within natural populations of Mimulus guttatus and Drosophila melanogaster, we found a surprisingly high variance of TE count (e.g., ...variance-to-mean ratio on the order of 10 to 300). To obtain insight regarding the evolutionary genetic mechanisms that underlie the overdispersed population distributions of TE abundance, we developed a mathematical model of TE population genetics that includes the dynamics of element proliferation and purifying selection on TE load. The modeling approach begins with a master equation for a birth-death process and extends the predictions of the classical theory of TE dynamics in several ways. In particular, moment-based analyses of population distributions of TE load reveal that overdispersion is likely to arise via copy-and-paste proliferation dynamics, especially when the elementary processes of proliferation and excision are approximately balanced. Parameter studies and analytic work confirm this result and further suggest that overdispersed population distributions of TE abundance are probably not a consequence of purifying selection on total element load.
Plant hormones and seed germination Miransari, Mohammad; Smith, D.L.
Environmental and experimental botany,
03/2014, Letnik:
99
Journal Article
Recenzirano
•Effects of plant hormones on seed germination with reference to proteomic and molecular biology studies.•The hormonal signaling pathways affecting seed germination.•The distribution of genes in the ...seed regulating different seed activities.•The effects of soil bacteria on the production of plant hormones and establishment of seedlings.•A complete set of details, which may affect seed biology during dormancy and growth.
Seed germination is controlled by a number of mechanisms and is necessary for the growth and development of the embryo, resulting in the eventual production of a new plant. Under unfavorable conditions seeds may become dormant (secondary dormancy) to maintain their germination ability. However, when the conditions are favorable seeds can germinate. There are a number of factors controlling seed germination and dormancy, including plant hormones, which are produced by both plant and soil bacteria. Interactions between plant hormones and plant genes affect seed germination. While the activity of plant hormones is controlled by the expression of genes at different levels, there are plant genes that are activated in the presence of specific plant hormones. Hence, adjusting gene expression may be an effective way to enhance seed germination. The hormonal signaling of IAA and gibberellins has been presented as examples during plant growth and development including seed germination. Some interesting results related to the effects of seed gene distribution on regulating seed activities have also been presented. The role of soil bacteria is also of significance in the production of plant hormones during seed germination, as well as during the establishment of the seedling, by affecting the plant rhizosphere. Most recent findings regarding seed germination and dormancy are reviewed. The significance of plant hormones including abscisic acid, ethylene, gibberellins, auxin, cytokinins and brassinosteroids, with reference to proteomic and molecular biology studies on germination, is also discussed. This review article contains almost a complete set of details, which may affect seed biology during dormancy and growth.
1. Growing recognition of the importance of climate extremes as drivers of contemporary and future ecological dynamics has led to increasing interest in studying these locally and globally important ...phenomena. 2. Many ecological studies examining the impacts of what are deemed climate extremes, such as heat waves and severe drought, do not provide a definition of extremity, either from a statistical context based on the long-term climatic record or from the perspective of the response of the system - are the effects extreme (unusual or profound) in comparison to normal variability? 3. A synthetic definition of an extreme climatic event (ECE) is proposed that includes ‘extremeness' in both the driver and the response: an ECE is as an episode or occurrence in which a statistically rare or unusual climatic period alters ecosystem structure and/or function well outside the bounds of what is considered typical or normal variability. This definition is accompanied by a mechanistic framework based on the concept that extreme response thresholds associated with significant community change and altered ecosystem function must be crossed in order for an ECE to occur. 4. Synthesis. A definition and mechanistic framework for ECEs is used to identify priorities for future research that will enable ecologists to more fully assess the ecological consequences of climate extremes for ecosystem structure and function today and in a future world where their frequency and intensity are expected to increase.
DNA methylation is among the best studied epigenetic modifications and is essential to mammalian development. Although the methylation status of most CpG dinucleotides in the genome is stably ...propagated through mitosis, improvements to methods for measuring methylation have identified numerous regions in which it is dynamically regulated. In this Review, we discuss key concepts in the function of DNA methylation in mammals, stemming from more than two decades of research, including many recent studies that have elucidated when and where DNA methylation has a regulatory role in the genome. We include insights from early development, embryonic stem cells and adult lineages, particularly haematopoiesis, to highlight the general features of this modification as it participates in both global and localized epigenetic regulation.
Large-scale electrolysis of water for hydrogen generation requires better catalysts to lower the kinetic barriers associated with the oxygen evolution reaction (OER). Although most OER catalysts are ...based on crystalline mixed-metal oxides, high activities can also be achieved with amorphous phases. Methods for producing amorphous materials, however, are not typically amenable to mixed-metal compositions. We demonstrate that a low-temperature process, photochemical metal-organic deposition, can produce amorphous (mixed) metal oxide films for OER catalysis. The films contain a homogeneous distribution of metals with compositions that can be accurately controlled. The catalytic properties of amorphous iron oxide prepared with this technique are superior to those of hematite, whereas the catalytic properties of α-Fe₁₀₀ -y-z Co y Ni z O x are comparable to those of noble metal oxide catalysts currently used in commercial electrolyzers.
We have reviewed the literature and have identified more than 100 diseases or conditions that are associated with raised concentrations of plasma total homocysteine. The commonest associations are ...with cardiovascular diseases and diseases of the central nervous system, but a large number of developmental and age‐related conditions are also associated. Few other disease biomarkers have so many associations. The clinical importance of these associations becomes especially relevant if lowering plasma total homocysteine by B vitamin treatment can prevent disease and so improve health. Five diseases can at least in part be prevented by lowering total homocysteine: neural tube defects, impaired childhood cognition, macular degeneration, primary stroke, and cognitive impairment in the elderly. We conclude from our review that total homocysteine values in adults of 10 μmol/L or below are probably safe, but that values of 11 μmol/L or above may justify intervention. Homocysteine is more than a disease biomarker: it is a guide for the prevention of disease.
C(1)‐Ammonium enolates are powerful, catalytically generated synthetic intermediates applied in the enantioselective α‐functionalisation of carboxylic acid derivatives. This minireview describes the ...recent developments in the generation and application of C(1)‐ammonium enolates from various precursors (carboxylic acids, anhydrides, acyl imidazoles, aryl esters, α‐diazoketones, alkyl halides) using isothiourea Lewis base organocatalysts. Their synthetic utility in intra‐ and intermolecular enantioselective C−C and C−X bond forming processes on reaction with various electrophiles will be showcased utilising two distinct catalyst turnover approaches.
C(1)‐Ammonium enolates have found widespread application for the enantioselective α‐functionalisation of carboxylic acid derivatives. This minireview highlights the recent advances in the generation of C(1)‐ammonium enolate intermediates by using isothiourea Lewis base organocatalysts and various precursors. The synthetic utility is showcased in intra‐ and intermolecular enantioselective C−C and C−X bond forming processes on reaction with various electrophiles utilising two distinct catalyst turnover approaches.