Critical behaviour in the nonlinear elastic response of hydrogels

In this paper we study the elastic response of synthetic hydrogels to an applied shear stress. The hydrogels studied here have previously been shown to mimic the behaviour of biopolymer networks when they are sufficiently far above the gel point. We show that near the gel point they exhibit an elastic response that is consistent with the predicted critical behaviour of networks near or below the isostatic point of marginal stability. This point separates rigid and floppy states, distinguished by the presence or absence of finite linear elastic moduli. Recent theoretical work has also focused on the response of such networks to finite or large deformations, both near and below the isostatic point. Despite this interest, experimental evidence for the existence of criticality in such networks has been lacking. Using computer simulations, we identify critical signatures in the mechanical response of sub-isostatic networks as a function of applied shear stress. We also present experimental evidence consistent with these predictions. Furthermore, our results show the existence of two distinct critical regimes, one of which arises from the nonlinear stretch response of semi-flexible polymers.

Carbon content of Mnemiopsis leidyi eggs and specific egg production rates in northern Europe

The comb jelly Mnemiopsis leidyi is considered to be a successful invasive species, partly due to its high reproduction potential. However, due to the absence of direct carbon measurements of eggs, specific reproduction rates remain uncertain. We show that egg carbon is 0.22 ± 0.02 µg C and up to 21 times higher than previously extrapolated. With maximum rates of 11 232 eggs ind−1 day−1, largest animals in northern Europe invest ∼10% day−1 of their body carbon into reproduction. The comb jelly M. leidyi has received wide public and scientific attention during the last decades due to its commonly observed formation of bloom abundances in native and invaded areas (e.g. Costello et al., 2012; Riisgård et al., 2012). One of the traits suggested to be responsible for M. leidyi's invasion success is its high fecundity. At the northern end of its distribution range in native areas, M. leidyi has been shown to produce up to 9380 and 14 233 eggs ind−1 day−1 (Kremer, 1976a; Graham et al., 2009), with similar rates of 9910 eggs ind−1 day−1 for the native southern population in Biscayne Bay, FL, USA (Baker and Reeve, 1974). Within invaded European waters, rates of up to 3000 and 12 000 eggs ind−1 day−1 have been recorded for northern and southern populations, respectively (Zaika and Revkov, 1994; Javidpour et al., 2009). Since M. leidyi is a simultaneous hermaphrodite and fertilized eggs are produced on a daily basis during favorable conditions (Jaspers, 2012), M. leidyi can circumvent the Allee effect and efficiently seed new populations even from few founding individuals. Although

Saprophytic colonization of the bark by Neofusicoccum species mediates subsequent infection of grapevines through wounds

Botryosphaeriaceae species infect grapevines via wounds. A previous study isolated Botryosphaeriaceae at higher frequencies from the bark than the underlying wood of asymptomatic grapevines canes from vineyards,suggesting they were latent on surface tissues. This study investigated the colonization of the bark as a saprophytic link to infection of the underlying wood. The bark of trunks of Sauvignon blanc and Pinot noir potted vines were inoculated by spraying an area of 3 cm length with ~1 mL of a Neofusicoccum luteum or N. parvum conidial suspensions (10⁴/mL). Control vines were inoculated with sterile water. After 1 hour (T1), 2 days (T2) or 7 days (T3) a cut was made in the bark and through to the wood 1 cm above the inoculation area using a sterile scalpel. After 24 h, isolations were carried out from surface sterilized bark and wood. Infection incidence did not differ significantly between species or grapevine cultivar. Infection incidence of the bark was 100% and associated wood of the central inoculated section was 76.3%, 83.3% and 90.2% for T1, T2 and T3, respectively indicating bark infection progressed rapidly into the adjacent wood. Infection of bark and wood 1 cm above the inoculation point increased with incubation time, being 25% for bark and wood at T1 and 71% and 67% for bark and wood, respectively at T3. Infection of the bark and wood 1 cm below the inoculated area was 0%. This study showed that the pathogens remained latent in the bark and, when the cane was wounded, that the pathogen progressed towards the wound. Fluorescent microscopic observations of bark and underlying wood sections of shoots inoculated onto the bark, but without wounding, showed germinating conidia and mycelium in the bark near lenticels, and mycelia in the underlying wood, indicating that the pathogens had entered through lenticels

Why the idea of framework propositions cannot contribute to an understanding of delusions

One of the tasks that recent philosophy of psychiatry has taken upon itself is to extend the range of understanding to some of those aspects of psychopathology that Jaspers deemed beyond its limits. Given the fundamental difficulties of offering a literal interpretation of the contents of primary delusions, a number of alternative strategies have been put forward including regarding them as abnormal versions of framework propositions described by Wittgenstein in On Certainty. But although framework propositions share some of the apparent epistemic features of primary delusions, their role in partially constituting the sense of inquiry rules out their role in helping to understand delusions

Propagule and soil type affects the pathogenicity of Ilyonectria and Dactylonectria spp., the causal agents of black foot disease of grapevines

Black foot disease of grapevines is a significant economic issue for the viticulture industry worldwide. The disease is mainly associated with soil borne pathogen species within the genera Dactylonectria and Ilyonectria. The aim of this study was to determine the pathogenicity of different pathogen propagules, including chlamydospores, conidia and mycelium, to grapevine rootstocks grown in soil. A combination of nine isolates belonging to Dactylonectria and Ilyonectria genera, representative of the fungal species associated with black foot disease in New Zealand were used to inoculate grapevines in a field experiment. In the second experiment, the pathogenicity of the different propagules was assessed in different soil types, clay loam, silt loam and sandy loam soils. In the field experiment, chlamydospores and conidia resulted in higher disease incidence and severity at 0 cm above the grapevine stem base compared with mycelium. At 5 cm above the stem base, chlamydospores caused the greatest disease incidence compared with the other two propagules. Propagule type had no effect on shoot and root dry weights. In the pot experiment, soil type affected disease incidence and severity, with clay loam soil resulting in significantly greater disease incidence and severity than silt loam or sandy loam soils. Disease severity at 0 cm above the stem base was significantly higher with conidial inoculations compared with chlamydospore inoculations irrespective of soil type. Root dry weights were also affected with heavier roots from plants grown in sandy loam compared with silt loam and clay loam soils, however, shoot dry weight was greater in clay loam and sandy loam compared with silt loam soils. The results of the study confirmed that all propagule types were able to infect grapevine rootstocks when planted in inoculated soil and showed that although the pathogens were capable of infecting the rootstocks in all soil types, disease level was higher in the heavier clay loam soil. It is therefore recommended that growers either avoid planting in such soils or apply strategies to improve drainage and soil aeration

Schizophrenia and the progression of emotional expression in relation to others

Gaining an improved understanding of people diagnosed with schizophrenia has the potential to influence priorities for therapy. Psychosis is commonly understood through the perspective of the medical model. However, the experience of social context surrounding psychosis is not well understood. In this research project we used a phenomenological methodology with a longitudinal design to interview 7 participants across a 12-month period to understand the social experiences surrounding psychosis. Eleven themes were explicated and divided into two phases of the illness experience: (a) transition into emotional shutdown included the experiences of not being acknowledged, relational confusion, not being expressive, detachment, reliving the past, and having no sense of direction; and (b) recovery from emotional shutdown included the experiences of being acknowledged, expression, resolution, independence, and a sense of direction. The experiential themes provide clinicians with new insights to better assess vulnerability, and have the potential to inform goals for therapy

Transcription-associated breaks in Xeroderma Pigmentosum group D cells from patients with combined features of Xeroderma Pigmentosum and Cockayne Syndrome

Defects in the XPD gene can result in several clinical phenotypes, including xeroderma pigmentosum (XP), trichothiodystrophy, and, less frequently, the combined phenotype of XP and Cockayne syndrome (XP-D/CS). We previously showed that in cells from two XP-D/CS patients, breaks were introduced into cellular DNA on exposure to UV damage, but these breaks were not at the sites of the damage. In the present work, we show that three further XP-D/CS patients show the same peculiar breakage phenomenon. We show that these breaks can be visualized inside the cells by immunofluorescence using antibodies to either gamma-H2AX or poly-ADP-ribose and that they can be generated by the introduction of plasmids harboring methylation or oxidative damage as well as by UV photoproducts. Inhibition of RNA polymerase II transcription by four different inhibitors dramatically reduced the number of UV-induced breaks. Furthermore, the breaks were dependent on the nucleotide excision repair (NER) machinery. These data are consistent with our hypothesis that the NER machinery introduces the breaks at sites of transcription initiation. During transcription in UV-irradiated XP-D/CS cells, phosphorylation of the carboxy-terminal domain of RNA polymerase II occurred normally, but the elongating form of the polymerase remained blocked at lesions and was eventually degraded

Pharmacokinetics of amphotericin B after accidental overdose in an adult critically ill patient treated with plasmapheresis: a case report and review of literature

Amphotericin B is a broad-spectrum antifungal agent that is used in the treatment of systemic fungal infections. We describe the case of a 62-year-old female patient with recent aneurysmal subarachnoid hemorrhage who was treated for suspected ventriculitis and a fungal coinfection. Instead of liposomal amphotericin B (L-AmB), 465 mg (5 mg/kg) amphotericin B deoxycholate (DOC) was inadvertently administered, leading to refractory shock with multiple organ failure and requiring mechanical ventilation. Since an overdose of amphotericin B can lead to fatal consequences and has a half-life of 15 days, plasmapheresis was started. The serum concentration decreased from 1.32 µg/mL to 0.62 µg/mL before plasmapheresis, demonstrating a mean half-life of 49 hours. After two plasmapheresis sessions, the serum concentration further dropped to 0.26 µg/mL, demonstrating a mean half-life of 17 hours. In contrast, the third plasmapheresis session had no effect on serum concentration. The patient made a full recovery, potentially facilitated by enhanced amphotericin B elimination through plasmapheresis. Positive outcomes were previously reported in two adult patients treated with plasmapheresis. However, other reports without plasmapheresis described fatal outcomes in adult patients, albeit with a twofold overdose compared to the two patients successfully treated with plasmapheresis. Moreover, plasmapheresis itself carries risks such as hypocalcemia, metabolic alkalosis, and coagulation deficits. Consequently, the role of plasmapheresis in amphotericin B overdose is still debated

Cultivable microbiota associated with Aurelia aurita and Mnemiopsis leidyi

The associated microbiota of marine invertebrates plays an important role to the host in relation to fitness, health, and homeostasis. Cooperative and competitive interactions between bacteria, due to release of, for example, antibacterial substances and quorum sensing (QS)/quorum quenching (QQ) molecules, ultimately affect the establishment and dynamics of the associated microbial community. Aiming to address interspecies competition of cultivable microbes associated with emerging model species of the basal animal phyla Cnidaria (Aurelia aurita) and Ctenophora (Mnemiopsis leidyi), we performed a classical isolation approach. Overall, 84 bacteria were isolated from A. aurita medusae and polyps, 64 bacteria from M. leidyi, and 83 bacteria from ambient seawater, followed by taxonomically classification by 16S rRNA gene analysis. The results show that A. aurita and M. leidyi harbor a cultivable core microbiome consisting of typical marine ubiquitous bacteria also found in the ambient seawater. However, several bacteria were restricted to one host suggesting host-specific microbial community patterns. Interbacterial interactions were assessed by (a) a growth inhibition assay and (b) QS interference screening assay. Out of 231 isolates, 4 bacterial isolates inhibited growth of 17 isolates on agar plates. Moreover, 121 of the 231 isolates showed QS-interfering activities. They interfered with the acyl-homoserine lactone (AHL)-based communication, of which 21 showed simultaneous interference with autoinducer 2. Overall, this study provides insights into the cultivable part of the microbiota associated with two environmentally important marine non-model organisms and into interbacterial interactions, which are most likely considerably involved in shaping a healthy and resilient microbiota