A comparison of incompressible limits for resistive plasmas

The constraint of incompressibility is often used to simplify the magnetohydrodynamic (MHD) description of linearized plasma dynamics because it does not affect the ideal MHD marginal stability point. In this paper two methods for introducing incompressibility are compared in a cylindrical plasma model: In the first method, the limit $\gamma \to \infty$ is taken, where $\gamma$ is the ratio of specific heats; in the second, an anisotropic mass tensor $\mathbf{\rho}$ is used, with the component parallel to the magnetic field taken to vanish, $\rho_{\parallel} \to 0$. Use of resistive MHD reveals the nature of these two limits because the Alfv\'en and slow magnetosonic continua of ideal MHD are converted to point spectra and moved into the complex plane. Both limits profoundly change the slow-magnetosonic spectrum, but only the second limit faithfully reproduces the resistive Alfv\'en spectrum and its wavemodes. In ideal MHD, the slow magnetosonic continuum degenerates to the Alfv\'en continuum in the first method, while it is moved to infinity by the second. The degeneracy in the first is broken by finite resistivity. For numerical and semi-analytical study of these models, we choose plasma equilibria which cast light on puzzling aspects of results found in earlier literature.Comment: 14 pages, 10 figure

Sustainability of Mahogany Production in Plantations: Does Resource Availability Influence Susceptibility of Young Mahogany Plantation Stands to Hypsipyla robusta Infestation?

Hypsipyla robusta Moore (Lepidoptera: Pyralidae), like many other moth species, shows selectivity when choosing host plants for its eggs. Four Meliaceae species (Khaya grandifoliola, K. ivorensis, Swietenia macrophyla, and Entandrophragma cylindricum) were established in a moist semideciduous forest in Ghana to study this selectivity at 12 and 21 months after planting. The analysis of variance (ANOVA) at a P-value of 0.05 was used to test the significance of differences in infestation by H. robusta between the species. H. robusta attacks were recorded by month 12 after planting in the field, and only Khaya spp. was attacked, with attacks evident on 15.5% of K grandifoliola and 6.6% K. ivorensis. Saplings in blocks closer to an older H. robusta infested K. grandifoliola stand had more infestation compared to saplings further away. The mean percentage of K. grandifoliola attacked was 38.9%, 38.9%, 13.3%, and 7.4% in 4 different plots located increasingly further away from the older infested plantation. A similar trend was found in K. ivorensis with 28.4%, 7.1%, 0.0%, and 0.0% in the plots located increasingly further away from the infested stand. These results indicate a higher number of shoot borer attacks at the edge of the plantation and in proximity to other infested plantations. After 21 months, the fastest-growing species and the fastest-growing individuals within the species were the most infested. K. grandifoliola recorded the fastest growth and most attacks followed by K. ivorensis and S. macrophylla. E. cylindricum recorded the least growth and no H. robusta infestation. After 21 months, the mean percentages of trees attacked were 59.1%, 23.7%, 5.6%, and 0.0% for K. grandifoliola, K. ivorensis, S. macrophylla, and E. cylindricum, respectively. Within species, the fastest-growing saplings experienced the most attacks. A positive correlation was observed between the plant size and H. robusta attacks (R2 = 0.76). Attacks resulted in the death of the apical shoot and the proliferation of multiple shoots in only the Khaya spp., with K. ivorensis recording a lower number of shoots than K. grandifoliola. These proliferated shoots were also attacked, and a positive correlation was observed between the number of proliferated shoots and H. robusta attacks (R2 = 0.84). These findings will assist plantation developers, forest managers, and investors in mahogany plantations to devise integrated pest management strategies to reduce the impact of Hypsipyla attacks on their plantations

Archetypal Reading of Fairytales

Tema je rada arhetipsko tumačenje bajke. Polazne pretpostavke istraživanja bile su moguće definicije bajki unutar kojih se pokušalo smjestiti jungovsku psihoanalitičku teoriju o arhetipovima na primjerima različitih likova svjetskih, europskih, kao i hrvatskih bajki. Ponajprije se bajka definira kao vrsta, a zatim je definiran pojam arhetipa, koji pripada psihoanalizi Carla Gustava Junga. Prema Jungovoj teoriji, arhetipovi su modeli osobnosti, „praslike“ i dio kolektivno nesvjesnoga te je u njima moguće pronaći simboliku za mnoge modele ponašanja svih ljudi. Cilj je rada proučiti psihoanalitičke stavove Carla Gustava Junga s obzirom na tumačenje arhetipova te primijeniti ta učenja na bajku i njezine likove. Predstavljeni su narativni čimbenici bajke te kako se njihova uloga uklapa u koncept arhetipskog čitanja, a poseban je naglasak stavljen na arhetipove Jastva, Anime, Animusa, Sjene i Persone, na temelju čijih su karakteristika i simbolike razvrstani mnogi likovi iz poznatih europskih i hrvatskih bajki. Svaki je arhetip predstavljen s psihoanalitičke strane, koristeći kao glavnu teorijsku literarnu jedinicu knjigu Jolande Jacobi Psihologija C.G.Junga, a u interpretaciji arhetipskih likova u bajkama knjigu Marie-Louise von Franz Interpretacija bajki

Path Integral Monte Carlo Simulation of the Low-Density Hydrogen Plasma

Restricted path integral Monte Carlo simulations are used to calculate the equilibrium properties of hydrogen in the density and temperature range of $9.83 \times 10^{-4}\rm \leq \rho \leq 0.153 \rm gcm^{-3}$ and $5000 \leq T \leq 250 000 \rm K$. We test the accuracy of the pair density matrix and analyze the dependence on the system size, on the time step of the path integral and on the type of nodal surface. We calculate the equation of state and compare with other models for hydrogen valid in this regime. Further, we characterize the state of hydrogen and describe the changes from a plasma to an atomic and molecular liquid by analyzing the pair correlation functions and estimating the number of atoms and molecules present.Comment: 12 pages, 21 figures, submitted for Phys. Rev.

Formation and Interaction of Membrane Tubes

We show that the formation of membrane tubes (or membrane tethers), which is a crucial step in many biological processes, is highly non-trivial and involves first order shape transitions. The force exerted by an emerging tube is a non-monotonic function of its length. We point out that tubes attract each other, which eventually leads to their coalescence. We also show that detached tubes behave like semiflexible filaments with a rather short persistence length. We suggest that these properties play an important role in the formation and structure of tubular organelles.Comment: 4 pages, 3 figure

Processing of the papain precursor. Purification of the zymogen and characterization of its mechanism of processing.

The precursor of the cysteine protease papain has been expressed and secreted as propapain from insect cells infected with a recombinant baculovirus expressing a synthetic gene coding for prepropapain. This 39-kDa secreted propapain zymogen molecule is glycosylated and can be processed in vitro into an enzymatically active authentic papain molecule of 24.5 kDa (Vernet, T., Tessier, D.C., Richardson, C., Laliberte, F., Khouri, H. E., Bell, A. W., Storer, A. C., and Thomas, D. Y. (1990) J. Biol. Chem. 265, 16661-16666). Recombinant propapain was stabilized with Hg2+ and purified to homogeneity using affinity chromatography, gel filtration, and ion-exchange chromatographic procedures. The maximum rate of processing in vitro was achieved at approximately pH 4.0, at a temperature of 65 degrees C and under reducing conditions. Precursor processing is inhibited by a variety of reversible and irreversible cysteine protease inhibitors but not by specific inhibitors of serine, metallo or acid proteases. Replacement by site-directed mutagenesis of the active site cysteine with a serine at position 25 also prevents processing. The inhibitor 125I-N-(2S,3S)-3-trans-hydroxycarbonyloxiran-2-carbonyl-L-tyrosine benzyl ester covalently labeled the wild type papain precursor, but not the C25S mutant, indicating that the active site is accessible to the inhibitor and is in a native conformation within the precursor. Based on biochemical and kinetic analyses of the activation and processing of propapain we have shown that the papain precursor is capable of autoproteolytic cleavage (intramolecular). Once free papain is released processing can then occur in trans (intermolecular)

A Randomized Phase III Trial Investigating 2 Gy TBI Vs. Flu/2 Gy TBI Conditioning for HLA-Matched Related Donor Hematopoietic Cell Transplantation (HCT): Tempo of CD3 and NK Cell Engraftment Determines Relapse and Progression Free Survival in Patients with Hematologic

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How to have sex in a pandemic: the development of strategies to prevent COVID-19 transmission in sexual encounters among gay and bisexual men in Australia

Although many studies reported on decreases in sexual partner numbers among gay and bisexual-identifying men in the early period of the COVID-19 pandemic, few studies have explored COVID-19 risk-reduction strategies. Drawing on free-text responses in an online survey (from April to July 2020), we describe the ways in which men sought to minimise the risk of COVID-19 in sexual encounters. Partner selection was an important strategy, in particular, restricting sex to men they already knew. Accounts also indicate how participants assessed risk from potential sex partners based on symptoms, residential location, recent travel, work role, and number of other sexual contacts. Less common were in situ practices, such as avoiding kissing. Participants’ responses provide insight into creative community-based responses in the early months of the pandemic, some of which have resonances with early responses to HIV. Findings are discussed in relation to the concepts of ‘lay epidemiology’ and ‘counterpublic health’. In particular, we examine how risks and health are experienced and valued in relation to local knowledges, meanings, and practices; and how practices emerge in response to dominant public health discourses that produce an idealised public based on (hetero)normative assumptions