Self-consistent bounces in two dimensions

We compute bounce solutions describing false vacuum decay in a Phi**4 model in two dimensions in the Hartree approximation, thus going beyond the usual one-loop corrections to the decay rate. We use zero energy mode functions of the fluctuation operator for the numerical computation of the functional determinant and the Green's function. We thus avoid the necessity of discretizing the spectrum, as it is necessary when one uses numerical techniques based on eigenfunctions. Regularization is performed in analogy of standard perturbation theory; the renormalization of the Hartree approximation is based on the two-particle point-irreducible (2PPI) scheme. The iteration towards the self-consistent solution is found to converge for some range of the parameters. Within this range we find the corrections to the leading one-loop approximation to be relatively small, not exceeding one order of magnitude in the total transition rate.Comment: 30 pages, 12 figure

Beyond behavior: Linguistic evidence of cultural variation in parental ethnotheories of children’s prosocial helping

This study examined linguistic patterns in mothers’ reports about their toddlers’ involvement in everyday household work, as a way to understand the parental ethnotheories that may guide children’s prosocial helping and development. Mothers from two cultural groups – US Mexican-heritage families with backgrounds in indigenous American communities and middle-class European-American families – were interviewed regarding how their 2- to 3-year-old toddler gets involved in help with everyday household work. The study’s analytic focus was the linguistic form of mothers’ responses to interview questions asking about the child’s efforts to help with a variety of everyday household work tasks. Results showed that mothers responded with linguistic patterns that were indicative of ethnotheoretical assumptions regarding children’s agency and children’s prosocial intentions, with notable contrasts between the two cultural groups. Nearly all US Mexican-heritage mothers reported children’s contributions and participation using linguistic forms that centered children’s agency and prosocial initiative, which corresponds with extensive evidence suggesting the centrality of both children’s autonomy and supportive prosocial expectations in how children’s helpfulness is socialized in this and similar cultural communities. By contrast, middle-class European-American mothers frequently responded to questions about their child’s efforts to help with linguistic forms that “pivoted” to either the mother as the focal agent in the child’s prosocial engagement or to reframing the child’s involvement to emphasize non-help activities. Correspondence between cultural differences in the linguistic findings and existing literature on socialization of children’s prosocial helping is discussed. Also discussed is the analytic approach of the study, uncommon in developmental psychology research, and the significance of the linguistic findings for understanding parental ethnotheories in each community

Fractal self-organization of bacteria-inspired agents

We develop an agent-based model as a preliminary theoretical basis to guide the synthesis of a new class of materials with dynamic properties similar to bacterial colonies. Each agent in the model is representative of an individual bacterium capable of: the uptake of chemicals (nutrients), which are metabolized; active movement (part viscous, part diffusive), consuming metabolic energy; and cellular division, when agents have doubled in size. The agents grow in number and self-organize into fractal structures, depending on the rules that define the actions of the agents and the parameter values. The environment of the agents includes chemicals responsible for their growth and is described by a diffusion-reaction equation with Michaelis-Menten kinetics. These rules are modeled mathematically by a set of equations with five dimensionless groups that are functions of physical parameters. Simulations are performed for different parameter values. The resulting structures are characterized by their fractal scaling regime, box-counting and mass-radius dimensions, and lacunarity. Each parameter influences the overall structure in a unique way, generating a wide spectrum of structures. For certain combinations of parameter values, the model converges to a steady state, with a finite population of agents that no longer divide. © 2012 World Scientific Publishing Company

Geometric invariant theory of syzygies, with applications to moduli spaces

We define syzygy points of projective schemes, and introduce a program of studying their GIT stability. Then we describe two cases where we have managed to make some progress in this program, that of polarized K3 surfaces of odd genus, and of genus six canonical curves. Applications of our results include effectivity statements for divisor classes on the moduli space of odd genus K3 surfaces, and a new construction in the Hassett-Keel program for the moduli space of genus six curves.Comment: v1: 23 pages, submitted to the Proceedings of the Abel Symposium 2017, v2: final version, corrects a sign error and resulting divisor class calculations on the moduli space of K3 surfaces in Section 5, other minor changes, In: Christophersen J., Ranestad K. (eds) Geometry of Moduli. Abelsymposium 2017. Abel Symposia, vol 14. Springer, Cha

State attachment variability across distressing situations in middle childhood

Contemporary research suggests that attachment has both a trait-like, stable component, and a state-like component that varies across contexts. In the current study, we assessed state attachment variability across comparably distressing situations in middle childhood. In two samples, children reported their expectations of maternal support in each situation. Additionally, we administered trait attachment and psychological well-being measures. Results indicated that, overall, children varied in their expectations across situations: more than half of the variance was explained by intra-individual differences across situations. Results revealed two components underlying variability: a Signal-and-Support component reflecting expectations of support-seeking and receiving, and a Back-on-Track component reflecting expectations of stress reduction and comfort. State attachment variability was related to individual differences in trait attachment: children who are more securely attached at the trait level, overall appear to vary less in their state attachment, likely due to their high mean state attachment scores across situations. When the mean state attachment scores are accounted for, more securely attached children seem to vary more, suggesting that their state attachment expectations are more sensitive to contextual fluctuations. Importantly, degree of state attachment variability explained psychological well-being over and above trait attachment

Fussing About Fission: Defining Variety Among Mainstream and Exotic Apicomplexan Cell Division Modes

Cellular reproduction defines life, yet our textbook-level understanding of cell division is limited to a small number of model organisms centered around humans. The horizon on cell division variants is expanded here by advancing insights on the fascinating cell division modes found in the Apicomplexa, a key group of protozoan parasites. The Apicomplexa display remarkable variation in offspring number, whether karyokinesis follows each S/M-phase or not, and whether daughter cells bud in the cytoplasm or bud from the cortex. We find that the terminology used to describe the various manifestations of asexual apicomplexan cell division emphasizes either the number of offspring or site of budding, which are not directly comparable features and has led to confusion in the literature. Division modes have been primarily studied in two human pathogenic Apicomplexa, malaria-causing Plasmodium spp. and Toxoplasma gondii, a major cause of opportunistic infections. Plasmodium spp. divide asexually by schizogony, producing multiple daughters per division round through a cortical budding process, though at several life-cycle nuclear amplifications stages, are not followed by karyokinesis. T. gondii divides by endodyogeny producing two internally budding daughters per division round. Here we add to this diversity in replication mechanisms by considering the cattle parasite Babesia bigemina and the pig parasite Cystoisospora suis. B. bigemina produces two daughters per division round by a “binary fission” mechanism whereas C. suis produces daughters through both endodyogeny and multiple internal budding known as endopolygeny. In addition, we provide new data from the causative agent of equine protozoal myeloencephalitis (EPM), Sarcocystis neurona, which also undergoes endopolygeny but differs from C. suis by maintaining a single multiploid nucleus. Overall, we operationally define two principally different division modes: internal budding found in cyst-forming Coccidia (comprising endodyogeny and two forms of endopolygeny) and external budding found in the other parasites studied (comprising the two forms of schizogony, binary fission and multiple fission). Progressive insights into the principles defining the molecular and cellular requirements for internal vs. external budding, as well as variations encountered in sexual stages are discussed. The evolutionary pressures and mechanisms underlying apicomplexan cell division diversification carries relevance across Eukaryota

Plasmodium falciparum CRK4 directs continuous rounds of DNA replication during schizogony.

: Plasmodium parasites, the causative agents of malaria, have evolved a unique cell division cycle in the clinically relevant asexual blood stage of infection(1). DNA replication commences approximately halfway through the intracellular development following invasion and parasite growth. The schizont stage is associated with multiple rounds of DNA replication and nuclear division without cytokinesis, resulting in a multinucleated cell. Nuclei divide asynchronously through schizogony, with only the final round of DNA replication and segregation being synchronous and coordinated with daughter cell assembly(2,3). However, the control mechanisms for this divergent mode of replication are unknown. Here, we show that the Plasmodium-specific kinase PfCRK4 is a key cell-cycle regulator that orchestrates multiple rounds of DNA replication throughout schizogony in Plasmodium falciparum. PfCRK4 depletion led to a complete block in nuclear division and profoundly inhibited DNA replication. Quantitative phosphoproteomic profiling identified a set of PfCRK4-regulated phosphoproteins with greatest functional similarity to CDK2 substrates, particularly proteins involved in the origin of replication firing. PfCRK4 was required for initial and subsequent rounds of DNA replication during schizogony and, in addition, was essential for development in the mosquito vector. Our results identified an essential S-phase promoting factor of the unconventional P. falciparum cell cycle. PfCRK4 is required for both a prolonged period of the intraerythrocytic stage of Plasmodium infection, as well as for transmission, revealing a broad window for PfCRK4-targeted chemotherapeutics.<br/

The role of clathrin in post-golgi trafficking in toxoplasma gondii

Apicomplexan parasites are single eukaryotic cells with a highly polarised secretory system that contains unique secretory organelles (micronemes and rhoptries) that are required for host cell invasion. In contrast, the role of the endosomal system is poorly understood in these parasites. With many typical endocytic factors missing, we speculated that endocytosis depends exclusively on a clathrin-mediated mechanism. Intriguingly, in Toxoplasma gondii we were only able to observe the endogenous clathrin heavy chain 1 (CHC1) at the Golgi, but not at the parasite surface. For the functional characterisation of Toxoplasma gondii CHC1 we generated parasite mutants conditionally expressing the dominant negative clathrin Hub fragment and demonstrate that CHC1 is essential for vesicle formation at the trans-Golgi network. Consequently, the functional ablation of CHC1 results in Golgi aberrations, a block in the biogenesis of the unique secretory microneme and rhoptry organelles, and of the pellicle. However, we found no morphological evidence for clathrin mediating endocytosis in these parasites and speculate that they remodelled their vesicular trafficking system to adapt to an intracellular lifestyle

Evidence-based approach to thrombophilia testing

Thrombophilia can be identified in about half of all patients presenting with VTE. Testing has increased tremendously for various indications, but whether the results of such tests help in the clinical management of patients has not been settled. I use evidence from observational studies to conclude that testing for hereditary thrombophilia generally does not alter the clinical management of patients with VTE, with occasional exceptions for women at fertile age. Because testing for thrombophilia only serves limited purpose this should not be performed on a routine basis