Lipid and Protein Transfer between Nanolipoprotein Particles and Supported Lipid Bilayers.

A nanolipoprotein particle (NLP) is a lipid bilayer disc stabilized by two amphipathic "scaffold" apolipoproteins. It has been most notably utilized as a tool for solubilizing a variety of membrane proteins while preserving structural and functional properties. Transfer of functional proteins from NLPs into model membrane systems such as supported lipid bilayers (SLBs) would enable new opportunities, for example, two-dimensional protein crystallization and studies on protein-protein interactions. This work used fluorescence microscopy and atomic force microscopy to investigate the interaction between NLPs and SLBs. When incubated with SLBs, NLPs were found to spontaneously deliver lipid and protein cargo. The impact of membrane composition on lipid exchange was explored, revealing a positive correlation between the magnitude of lipid transfer and concentration of defects in the target SLB. Incorporation of lipids capable of binding specifically to polyhistidine tags encoded into the apolipoproteins also boosted transfer of NLP cargo. Optimal conditions for lipid and protein delivery from NLPs to SLBs are proposed based on interaction mechanisms

A new doubly discrete analogue of smoke ring flow and the real time simulation of fluid flow

Modelling incompressible ideal fluids as a finite collection of vortex filaments is important in physics (super-fluidity, models for the onset of turbulence) as well as for numerical algorithms used in computer graphics for the real time simulation of smoke. Here we introduce a time-discrete evolution equation for arbitrary closed polygons in 3-space that is a discretisation of the localised induction approximation of filament motion. This discretisation shares with its continuum limit the property that it is a completely integrable system. We apply this polygon evolution to a significant improvement of the numerical algorithms used in Computer Graphics.Comment: 15 pages, 3 figure

Finite-gap Solutions of the Vortex Filament Equation: Isoperiodic Deformations

We study the topology of quasiperiodic solutions of the vortex filament equation in a neighborhood of multiply covered circles. We construct these solutions by means of a sequence of isoperiodic deformations, at each step of which a real double point is "unpinched" to produce a new pair of branch points and therefore a solution of higher genus. We prove that every step in this process corresponds to a cabling operation on the previous curve, and we provide a labelling scheme that matches the deformation data with the knot type of the resulting filament.Comment: 33 pages, 5 figures; submitted to Journal of Nonlinear Scienc

Hamiltonian flows on null curves

The local motion of a null curve in Minkowski 3-space induces an evolution equation for its Lorentz invariant curvature. Special motions are constructed whose induced evolution equations are the members of the KdV hierarchy. The null curves which move under the KdV flow without changing shape are proven to be the trajectories of a certain particle model on null curves described by a Lagrangian linear in the curvature. In addition, it is shown that the curvature of a null curve which evolves by similarities can be computed in terms of the solutions of the second Painlev\'e equation.Comment: 14 pages, v2: final version; minor changes in the expositio

Metatranscriptome of human faecal microbial communities in a cohort of adult men

The gut microbiome is intimately related to human health, but it is not yet known which functional activities are driven by specific microorganisms\u27 ecological configurations or transcription. We report a large-scale investigation of 372 human faecal metatranscriptomes and 929 metagenomes from a subset of 308 men in the Health Professionals Follow-Up Study. We identified a metatranscriptomic \u27core\u27 universally transcribed over time and across participants, often by different microorganisms. In contrast to the housekeeping functions enriched in this core, a \u27variable\u27 metatranscriptome included specialized pathways that were differentially expressed both across participants and among microorganisms. Finally, longitudinal metagenomic profiles allowed ecological interaction network reconstruction, which remained stable over the six-month timespan, as did strain tracking within and between participants. These results provide an initial characterization of human faecal microbial ecology into core, subject-specific, microorganism-specific and temporally variable transcription, and they differentiate metagenomically versus metatranscriptomically informative aspects of the human faecal microbiome

Longitudinal Body Composition Changes in NCAA Division I College Football Players

Many athletes seek to optimize body composition to fit the physical demands of their sport. American football requires a unique combination of size, speed, and power. The purpose of the current study was to evaluate longitudinal changes in body composition in Division I collegiate football players. For 57 players (Mean ± SD; Age=19.5 ± 0.9 yrs; Height=186.9 ± 5.7 cm; Weight=107.7 ± 19.1 kg), body composition was assessed via dual-energy x-ray absorptiometry in the off-season (March-Pre), end of off-season (May), mid-July (Pre-Season), and the following March (March-Post). Outcome variables included weight, body fat percentage (BF%), fat mass (FM), lean mass (LM), android (AND) and gynoid (GYN) fat, bone mineral content (BMC), and bone density (BMD). For a subset of athletes (n=13 out of 57), changes over a 4-year playing career were evaluated with measurements taken every March. Throughout a single year, favorable changes were observed for BF% (Δ=−1.3 ± 2.5%), LM (Δ=2.8 ± 2.8 kg), GYN (Δ=−1.5 ± 3.0%), BMC (Δ=0.06 ± 0.14 kg), and BMD (Δ=0.015 ± 0.027g·cm−2; all p<0.05). Across four years, weight increased significantly (Δ=6.6 ± 4.1kg), and favorable changes were observed for LM (Δ=4.3 ± 3.0 kg), BMC (Δ=0.18 ± 0.17 kg), and BMD (Δ=0.033 ± 0.039 g·cm−2; all p<0.05). Similar patterns in body composition changes were observed for linemen and non-linemen. Results indicate that well-trained collegiate football players at high levels of competition can achieve favorable changes in body composition, even late in the career, which may confer benefits for performance and injury prevention

Ricci Solitons and Einstein-Scalar Field Theory

B List has recently studied a geometric flow whose fixed points correspond to static Ricci flat spacetimes. It is now known that this flow is in fact Ricci flow modulo pullback by a certain diffeomorphism. We use this observation to associate to each static Ricci flat spacetime a local Ricci soliton in one higher dimension. As well, solutions of Euclidean-signature Einstein gravity coupled to a free massless scalar field with nonzero cosmological constant are associated to shrinking or expanding Ricci solitons. We exhibit examples, including an explicit family of complete expanding solitons which can be thought of as a Ricci flow for a complete Lorentzian metric. The possible generalization to Ricci-flat stationary metrics leads us to consider an alternative to Ricci flow.Comment: 17 pages, 1 figure; Revised version (organizational changes, other minor revisions and corrections, citations corrected and added), to appear in CQ

Stability of the human faecal microbiome in a cohort of adult men

Characterizing the stability of the gut microbiome is important to exploit it as a therapeutic target and diagnostic biomarker. We metagenomically and metatranscriptomically sequenced the faecal microbiomes of 308 participants in the Health Professionals Follow-Up Study. Participants provided four stool samples—one pair collected 24–72 h apart and a second pair ~6 months later. Within-person taxonomic and functional variation was consistently lower than between-person variation over time. In contrast, metatranscriptomic profiles were comparably variable within and between subjects due to higher within-subject longitudinal variation. Metagenomic instability accounted for ~74% of corresponding metatranscriptomic instability. The rest was probably attributable to sources such as regulation. Among the pathways that were differentially regulated, most were consistently over- or under-transcribed at each time point. Together, these results suggest that a single measurement of the faecal microbiome can provide long-term information regarding organismal composition and functional potential, but repeated or short-term measures may be necessary for dynamic features identified by metatranscriptomics

Rotational symmetry of self-similar solutions to the Ricci flow

Let (M,g) be a three-dimensional steady gradient Ricci soliton which is non-flat and \kappa-noncollapsed. We prove that (M,g) is isometric to the Bryant soliton up to scaling. This solves a problem mentioned in Perelman's first paper.Comment: Final version, to appear in Invent. Mat

Racial Disparities in Quality of Medication Use in Older Adults: Findings From a Longitudinal Study

The quality of medication use in older adults is suboptimal with a large percentage of individuals not receiving recommended care. Most efforts to evaluate the quality of medication use target high-risk drugs, appropriate treatment of prevalent chronic disease states, or a set of predefined quality indicators of medication use, rather than the patient. It is also suggested that racial differences in the quality of medication use may exist in older adults