Microbial diversity in Baltic Sea sediments

This thesis focuses on microbial community structures and their functions in Baltic Sea sediments. First we investigated the distribution of archaea and bacteria in Baltic Sea sediments along a eutrophication gradient. Community profile analysis of 16S rRNA genes using terminal restriction length polymorphism (T-RFLP) indicated that archaeal and bacterial communities were spatially heterogeneous. By employing statistical ordination methods we observed that archaea and bacteria were structured and impacted differently by environmental parameters that were significantly linked to eutrophication. In a separate study, we analyzed bacterial communities at a different site in the Baltic Sea that was heavily contaminated with polyaromatic hydrocarbons (PAHs) and several other pollutants. Sediment samples were collected before and after remediation by dredging in two consecutive years. A polyphasic experimental approach was used to assess growing bacteria and degradation genes in the sediments. The bacterial communities were significantly different before and after dredging of the sediment. Several isolates collected from contaminated sediments showed an intrinsic capacity for degradation of phenanthrene (a PAH model compound). Quantititative real-time PCR was used to monitor the abundance of degradation genes in sediment microcosms spiked with phenanthrene. Although both xylE and phnAc genes increased in abundance in the microcosms, the isolates only carried phnAc genes. Isolates with closest 16S rRNA gene sequence matches to Exigobacterium oxidotolerans, a Pseudomonas sp. and a Gammaproteobacterium were identified by all approaches used as growing bacteria that are capable of phenanthrene degradation. These isolates were assigned species and strain designations as follows: Exiguobacterium oxidotolerans AE3, Pseudomonas fluorescens AE1 and Pseudomonas migulae AE2. We also identified and studied the distribution of actively growing bacteria along red-ox profiles in Baltic Sea sediments. Community structures were found to be significantly different at different red-ox depths. Also, according to multivariate statistical ordination analysis organic carbon, nitrogen, and red-ox potential were crucial parameters for structuring the bacterial communities on a vertical scale. Novel lineages of bacteria were obtained by sequencing 16S rRNA genes from different red-ox depths and sampling stations indicating that bacterial diversity in Baltic Sea sediments is largely unexplored

Pill Power: The Prequel

Goldin and Katz [2002], in an influential paper, argued that giving unmarried minors access to the contraceptive Pill was instrumental for women's professional advancement, because such access allowed marriage to be postponed. However, by 1960, married women could get the Pill and thence it is not clear why early marriage would interfere with the pursuit of professional interests. We explore the effects of this alternative, earlier, and common, route to the Pill. Using variation in state minimum-age marriage laws (EMA), we find that EMA precipitated marriage, delayed fertility within marriage, and improved the educational and occupational outcomes of women, especially non-college women. Thus, fertility control, marriage notwithstanding, emerges as a key enabler of women's educational and professional advancement.education, marriage, contraceptive pill, occupation

Predicting self-assembled patterns on spheres with multi-component coatings

Interactions between the components in many-body systems can give rise to spontaneous formation of complex structures. Usually very little is known about the connection between the interactions and the resulting structure. Here we present a theory for self-assembling pattern formation in multi-component systems, formulated as an analytic technique that predicts morphologies directly from the interactions in an effective model. As a demonstration we apply the method to a model of alkanethiols on spherical gold particles, successfully predicting its morphologies and transitions as a function of the interaction parameters. This system is interesting because it has been suggested to provide an effective route to produce patchy colloids.Comment: 5 pages, 4 figure

The Evolution of Giving: Considerations for Regulation of Cryptocurrency Donation Deductions

This Issue Brief looks at the rapidly growing area of cryptocurrency donations to nonprofit organizations. Given the recent IRS guidance issued on taxation of Bitcoin, specifically its decision to treat cryptocurrencies as property, questions now arise as to how charitable contributions of the coins will be valued for tax deductions. Though Bitcoin resembles most other capital gain property, its volatility, general decline in value, anonymity, and potential for abuse require specific guidance on valuation and substantiation so as to handle its unique nature and prevent larger deductions for charitable contributions than those to which taxpayers are entitled

Quantum Coherence as a Witness of Vibronically Hot Energy Transfer in Bacterial Reaction Centre

Photosynthetic proteins have evolved over billions of years so as to undergo optimal energy transfer to the sites of charge separation. Based on spectroscopically detected quantum coherences, it has been suggested that this energy transfer is partially wavelike. This conclusion critically depends on assignment of the coherences to the evolution of excitonic superpositions. Here we demonstrate for a bacterial reaction centre protein that long-lived coherent spectroscopic oscillations, which bear canonical signatures of excitonic superpositions, are essentially vibrational excited state coherences shifted to the ground state of the chromophores . We show that appearance of these coherences is brought about by release of electronic energy during the energy transfer. Our results establish how energy migrates on vibrationally hot chromophores in the reaction centre and they call for a re-examination of claims of quantum energy transfer in photosynthesis

Exceptional geometry and tensor fields

We present a tensor calculus for exceptional generalised geometry. Expressions for connections, torsion and curvature are given a unified formulation for different exceptional groups E_n(n). We then consider "tensor gauge fields" coupled to the exceptional generalised gravity. Many of the properties of forms on manifolds are carried over to these fields.Comment: 22 pp., plain tex. v3: improved reference

Evolution of robustness in digital organisms

We study the evolution of robustness in digital organisms adapting to a high mutation rate. As genomes adjust to the harsh mutational environment, the mean effect of single Imitations decreases, up until the point where a sizable fraction (up to 30% in many cases) of the Imitations are neutral. We correlate the changes in robustness along the line of descent to changes in directional epistasis, and find that increased robustness is achieved by moving from antagonistic epistasis between mutations towards codes where mutations are, on average, independent. We interpret this recoding as a breakup of linkage between vital sections of the genome, up to the point where instructions are maximally independent of each other. While such a recoding often requires sacrificing some replication speed, it is the best strategy for withstanding high rates of mutation