Mechanical properties of viral capsids

Viruses are known to tolerate wide ranges of pH and salt conditions and to withstand internal pressures as high as 100 atmospheres. In this paper we investigate the mechanical properties of viral capsids, calling explicit attention to the inhomogeneity of the shells that is inherent to their discrete and polyhedral nature. We calculate the distribution of stress in these capsids and analyze their response to isotropic internal pressure (arising, for instance, from genome confinement and/or osmotic activity). We compare our results with appropriate generalizations of classical (i.e., continuum) elasticity theory. We also examine competing mechanisms for viral shell failure, e.g., in-plane crack formation vs radial bursting. The biological consequences of the special stabilities and stress distributions of viral capsids are also discussed

Concurrent Deficits in Behavior Inhibition, Non-verbal Working Memory and Psychological Sense of Time in ADHD

According to the Hybrid Model of Executive Function for Attention Deficit Hyperactivity Disorder (ADHD), hyperactive and combined types, a delay in behavior inhibition causes secondary deficits in four executive function; non-verbal working memory, verbal working memory, reconstitution and self-regulation of affect/motivation/arousal. The deficit in non-verbal working memory causes a deficit in psychological sense of time, which in tum impairs self-regulation in those with ADHD. This single case study investigated concurrent deficits in behavior inhibition, non-verbal working memory and psychological sense of time in a 1O-year-old male with ADHD, combined type. Three interrelated components of behavior inhibition were measured by the Continuous Performance Test-II, The Wisconsin Card Sorting Test, and the Stroop Test. Non-verbal working memory was measured by using the Rey-Complex Figure Test and Recognition Trial, and the psychological sense of time was measured by the Time Perception Test, which is a time reproduction task. The results of this case study supports the Hybrid Model of Executive Function as concurrent deficits in behavior inhibition, non-verbal working memory and psychological sense of time were found in a subject with ADHD, combined type. The implications of these findings for treatment and future research are discussed

Thermodynamics of nano-spheres encapsulated in virus capsids

We investigate the thermodynamics of complexation of functionalized charged nano-spheres with viral proteins. The physics of this problem is governed by electrostatic interaction between the proteins and the nano-sphere cores (screened by salt ions), but also by configurational degrees of freedom of the charged protein N-tails. We approach the problem by constructing an appropriate complexation free energy functional. On the basis of both numerical and analytical studies of this functional we construct the phase diagram for the assembly which contains the information on the assembled structures that appear in the thermodynamical equilibrium, depending on the size and surface charge density of the nano-sphere cores. We show that both the nano-sphere core charge as well as its radius determine the size of the capsid that forms around the core.Comment: Submitte

Quantum and thermal Casimir interaction between a sphere and a plate: Comparison of Drude and plasma models

We calculate the Casimir interaction between a sphere and a plate, both described by the plasma model, the Drude model, or generalizations of the two models. We compare the results at both zero and finite temperatures. At asymptotically large separations we obtain analytical results for the interaction that reveal a non-universal, i.e., material dependent interaction for the plasma model. The latter result contains the asymptotic interaction for Drude metals and perfect reflectors as different but universal limiting cases. This observation is related to the screening of a static magnetic field by a London superconductor. For small separations we find corrections to the proximity force approximation (PFA) that support correlations between geometry and material properties that are not captured by the Lifshitz theory. Our results at finite temperatures reveal for Drude metals a non-monotonic temperature dependence of the Casimir free energy and a negative entropy over a sizeable range of separations.Comment: 11 pages, 5 figure

Open innovation for sustainability: Lessons from the GreenXchange experience

Despite its rising popularity, open innovation has received relatively limited attention in the discussion of how to implement ‘green’ innovation, a fact which is of particular relevance within the context of the Rio+20 summit 2012. The GreenXchange (GX), which was launched in 2010 by Nike along with nine other organizations, is an important exception to this trend. The GX is a web-based marketplace for intellectual property (IP), which appears not to have lived up entirely to the original expectations set out at its creation. Other than Nike, only one other company – Best Buy – has agreed to place its IP assets on the GX and the vast majority of the posted IP cannot be used in the creation of commercial products. This paper explores in what ways the GX exemplifies both the usefulness and limitations of open innovation for sustainability and discusses the lessons that can be drawn from the GX experience in terms of the broader thinking on innovation, intellectual property and sustainability. It concludes by proposing ways that can help such initiatives be made to function better

Open innovation for sustainability: Lessons from the GreenXchange experience

Despite its rising popularity, open innovation has received relatively limited attention in the discussion of how to implement ‘green’ innovation, a fact which is of particular relevance within the context of the Rio+20 summit 2012. The GreenXchange (GX), which was launched in 2010 by Nike along with nine other organizations, is an important exception to this trend. The GX is a web-based marketplace for intellectual property (IP), which appears not to have lived up entirely to the original expectations set out at its creation. Other than Nike, only one other company – Best Buy – has agreed to place its IP assets on the GX and the vast majority of the posted IP cannot be used in the creation of commercial products. This paper explores in what ways the GX exemplifies both the usefulness and limitations of open innovation for sustainability and discusses the lessons that can be drawn from the GX experience in terms of the broader thinking on innovation, intellectual property and sustainability. It concludes by proposing ways that can help such initiatives be made to function better

Wheel-running activity modulates circadian organization and the daily rhythm of eating behavior

Consumption of high-fat diet acutely alters the daily rhythm of eating behavior and circadian organization (the phase relationship between oscillators in central and peripheral tissues) in mice. Voluntary wheel-running activity counteracts the obesogenic effects of high-fat diet and also modulates circadian rhythms in mice. In this study, we sought to determine whether voluntary wheel-running activity could prevent the proximate effects of high-fat diet consumption on circadian organization and behavioral rhythms in mice. Mice were housed with locked or freely rotating running wheels and fed chow or high-fat diet for 1 week and rhythms of locomotor activity, eating behavior, and molecular timekeeping (PERIOD2::LUCIFERASE luminescence rhythms) in ex vivo tissues were measured. Wheel-running activity delayed the phase of the liver rhythm by 4 h in both chow- and high-fat diet-fed mice. The delayed liver phase was specific to wheel-running activity since an enriched environment without the running wheel did not alter the phase of the liver rhythm. In addition, wheel-running activity modulated the effect of high-fat diet consumption on the daily rhythm of eating behavior. While high-fat diet consumption caused eating events to be more evenly dispersed across the 24 h-day in both locked-wheel and wheel-running mice, the effect of high-fat diet was much less pronounced in wheel-running mice. Together these data demonstrate that wheel-running activity is a salient factor that modulates liver phase and eating behavior rhythms in both chow- and high-fat-diet fed mice. Wheel-running activity in mice is both a source of exercise and a self-motivating, rewarding behavior. Understanding the putative reward-related mechanisms whereby wheel-running activity alters circadian rhythms could have implications for human obesity since palatable food and exercise may modulate similar reward circuits

Szenci Molnár Albert epigrammája a Scandell-antológiában

The composition of secondary organic aerosol (SOA) from the ozonolysis of C5−C8 cycloalkenes and α-pinene, as well as the effects of hydrocarbon precursor structure and particle-phase acidity on SOA formation, have been investigated by a series of controlled laboratory chamber experiments. A liquid chromatography−mass spectrometer and an ion trap mass spectrometer are used concurrently to identify and to quantify SOA components with molecular weights up to 1600 Da. Diacids, carbonyl-containing acids, diacid alkyl esters, and hydroxy diacids are the four major classes of low-molecular-weight (MW \u3c 250 Da) components in the SOA; together they comprise 42−83% of the total SOA mass, assuming an aerosol density of 1.4 g/cm3. In addition, oligomers (MW \u3e 250 Da) are found to be present in all SOA. Using surrogate standards, it is estimated that the mass fraction of oligomers in the total SOA is at least 10% for the cycloalkene systems (with six or more carbons) and well over 50% for the α-pinene system. Higher seed particle acidity is found to lead to more rapid oligomer formation and, ultimately, to higher SOA yields. Because oligomers are observed to form even in the absence of seed particles, organic acids produced from hydrocarbon oxidation itself may readily promote acid catalysis and oligomer formation. The distinct effects of carbon numbers, substituent groups, and isomeric structures of the precursor hydrocarbons on the composition and yield of SOA formed are also discussed

Nonspherical similarity solutions for dark halo formation

We carry out fully 3-dimensional simulations of evolution from self-similar, spherically symmetric linear perturbations of a Cold Dark Matter dominated Einstein-de Sitter universe. As a result of the radial orbit instability, the haloes which grow from such initial conditions are triaxial with major-to-minor axis ratios of order 3:1. They nevertheless grow approximately self-similarly in time. In all cases they have power-law density profiles and near-constant velocity anisotropy in their inner regions. Both the power-law index and the value of the velocity anisotropy depend on the similarity index of the initial conditions, the former as expected from simple scaling arguments. Halo structure is thus not "universal" but remembers the initial conditions. On larger scales the density and anisotropy profiles show two characteristic scales, corresponding to particles at first pericentre and at first apocentre after infall. They are well approximated by the NFW model only for one value of the similarity index. In contrast, at all radii within the outer caustic the pseudo phase-space density can be fit by a single power law with an index which depends only very weakly on the similarity index of the initial conditions. This behaviour is very similar to that found for haloes formed from LCDM initial conditions and so can be considered approximately universal.Comment: 8 pages, 7 figures, submitted to MNRA