Structure

An exploration of ground’s connections to structure (joint-carving, naturalness). The notion of structure is often invoked in connection to ground, because grounding is understood to impose constraints on the ‘structure of reality’. There is another, technical sense of structure, sometimes captured with reference to the notion of ‘joint-carving’. Both of these senses of structure as well as their potential connections are discussed

Evolutionary Dynamics and Optimization: Neutral Networks as Model-Landscapes for RNA Secondary-Structure Folding-Landscapes

We view the folding of RNA-sequences as a map that assigns a pattern of base pairings to each sequence, known as secondary structure. These preimages can be constructed as random graphs (i.e. the neutral networks associated to the structure $s$). By interpreting the secondary structure as biological information we can formulate the so called Error Threshold of Shapes as an extension of Eigen's et al. concept of an error threshold in the single peak landscape. Analogue to the approach of Derrida & Peliti for a of the population on the neutral network. On the one hand this model of a single shape landscape allows the derivation of analytical results, on the other hand the concept gives rise to study various scenarios by means of simulations, e.g. the interaction of two different networks. It turns out that the intersection of two sets of compatible sequences (with respect to the pair of secondary structures) plays a key role in the search for ''fitter'' secondary structures.Comment: 20 pages, uuencoded compressed postscript-file, Proc. of ECAL '95 conference, to appear., email: chris @ imb-jena.d

Structure–property relationships of iron arsenide superconductors

Iron based superconductors sent material scientists into a renewed excitement reminiscent of the time when the first high-Tc superconductors were discovered 25 years ago. This feature article reviews relationships between structural chemistry and magnetic as well as superconducting properties of iron arsenide compounds, which are outstandingly rich and uniquely coupled. Particular attention is paid to the nature of the structural phase transitions of the parent compounds and their possible origins, on effects of doping on the crystal structures and on the coexistence of magnetic ordering and superconductivity. In spite of the many fascinating insights that have already enriched the research on superconductivity, many questions are still open and prove iron based superconductors to be a good recipe for future discoveries in this lively field

Structure of Sn_1-xGe_x random alloys as obtained from the coherent potential approximation

The structure of the Sn1-xGex random alloys is studied using density functional theory and the coherent potential approximation. We report on the deviation of the Sn1-xGex alloys from Vegard's law, addressing their full compositional range. The findings are compared to the related Si1-xGex alloys and to experimental results. Interestingly, the deviation from Vegard's law is quantitatively and qualitatively different between the Sn1-xGex and Si1-xGex alloys. An almost linear dependence of the bulk modulus as a function of composition is found for Si1-xGex, whereas for Sn1-xGex the dependence is strongly nonlinear

The Structure of 401(k) Fees

Increasingly, people are depending on 401(k) and similar defined contribution plans sponsored by their employers for their retirement income. As a result, participants in these plans also are paying more of their plans’ costs, ranging from administration and sales expenses to the cost of managing investments. These costs can take a substantial toll on retirement savings. Over a 30-year career, for example, paying an annual fee of 50 basis points can reduce the purchasing power of savings at the time of retirement by one-eighth. Employers who sponsor 401(k) plans have a fiduciary responsibility to ensure their plans’ fees are reasonable and communicated to participants. Recently, the Government Accountability Office reported that participants need more information and sponsors need to disclose this information more effectively to fulfill this responsibility. The Department of Labor is revising regulations to require sponsors to report the fees of their plans more clearly to their employees. Congress also has been holding hearings, inquiring if greater disclosure would help reduce costs within 401(k) plans...

Structure

The G-rich single-stranded DNA at the 3' end of human telomeres can self-fold into G-quaduplex (GQ). However, telomere lengthening by telomerase or the recombination-based alternative lengthening of telomere (ALT) mechanism requires protein loading on the overhang. Using single-molecule fluorescence spectroscopy, we discovered that lengthening the telomeric overhang also increased the rate of dynamic exchanges between structural conformations. Overhangs with five to seven TTAGGG repeats, compared with four repeats, showed much greater dynamics and accessibility to telomerase binding and activity and loading of the ALT-associated proteins RAD51, WRN, and BLM. Although the eight repeats are highly dynamic, they can fold into two GQs, which limited protein accessibility. In contrast, the telomere-specific protein POT1 is unique in that it binds independently of repeat number. Our results suggest that the telomeric overhang length and dynamics may contribute to the regulation of telomere extension via telomerase action and the ALT mechanism.343 NIH 1 DP2 GM105453 A/DP/NCCDPHP CDC HHS/United StatesDP2 GM105453/GM/NIGMS NIH HHS/United StatesES0515052/ES/NIEHS NIH HHS/United StatesF30 CA174323/CA/NCI NIH HHS/United StatesR01 ES015052/ES/NIEHS NIH HHS/United StatesR01 ES015632/ES/NIEHS NIH HHS/United StatesR01 ES015632/ES/NIEHS NIH HHS/United StatesR01GM65484/GM/NIGMS NIH HHS/United StatesUL1 TR000142/TR/NCATS NIH HHS/United States2015-06-10T00:00:00Z24836024PMC406794

Combinatorial Penalties: Which structures are preserved by convex relaxations?

We consider the homogeneous and the non-homogeneous convex relaxations for combinatorial penalty functions defined on support sets. Our study identifies key differences in the tightness of the resulting relaxations through the notion of the lower combinatorial envelope of a set-function along with new necessary conditions for support identification. We then propose a general adaptive estimator for convex monotone regularizers, and derive new sufficient conditions for support recovery in the asymptotic setting