The suspected contradictory role of parental care in the adaption of planktonic calanoida to temporary freshwater

Calanoida have the highest number of species among Copepoda in marine plankton, but not in fresh water, where the greatest number are Cyclopoida. Freshwater Cyclopoida also live in more freshwater sites than Calanoida. This could be a consequence of an invasion of freshwater by marine Cyclopoida before Calanoida. Similar to Cyclopoida, but different from marine Calanoida, freshwater Calanoida females produce egg sacs and care for eggs. This strategy is common among all freshwater plankton, suggesting that the evolution of parental care is an obliged adaption to conquer fresh water. Calanoida, different from Cyclopoida, survive adverse conditions as resting eggs. This life-cycle constraint obliges eggs to survive their mother’s death and wait in the benthos for a certain period. The necessity of completing embryonic development and the hatching of eggs far from the mother’s protection may be responsible for the relatively lower evolutionary success of Calanoida in fresh water compared to Cyclopoida (which rest as juveniles, thus protecting eggs in any moment of their development). Therefore, the brooding of eggs appears to be the obliged solution for Calanoida’s final establishment in fresh water, but the dispersion of eggs on the bottom after the mother’s death and during the rest period is probably the weak point in Calanoida’s competition with Cyclopoida

High-Frequency-Induced Cathodic Breakdown during Plasma Electrolytic Oxidation

The present communication shows the possibility of observing microdischarges under cathodic polarization during plasma electrolytic oxidation at high frequency. Cathodic microdischarges can ignite beyond a threshold frequency found close to 2 kHz. The presence (respectively, absence) of an electrical double layer is put forward to explain how the applied voltage can be screened, which therefore prevents (respectively, promotes) the ignition of a discharge. Interestingly, in the conditions of the present study, the electrical double layer requires between 175 and 260 μs to form. This situates the expected threshold frequency between 1.92 and 2.86 kHz, which is in good agreement with the value obtained experimentally

RESTING CYSTS FROM COASTAL MARINE PLANKTON

Coastal plankton show fluctuations in abundance and species composition. Resting stage (cyst) production is a common strategy adopted by hundreds of plankton species to ensure reproduction and to avoid adverse conditions. During the resting period, these species are normally absent from the water column, and cysts produced in the plankton accumulate in the sediment where they wait for the return of suitable conditions. A portion of the cyst bank does not hatch, instead undergoing a dormancy that may extend for decades. Confined coastal areas accumulate cysts in sediment due to one or more possibilities, including reduced water movement/hydrodynamics, high population density, abundance of cyst-producing species, and the absence or scarcity of possible cyst consumers in the benthos. The pelagic-benthic nexus, which affects both the sediment and the water column (and possibly sea ice) is still poorly understood. In fact, the presence of cysts in the life cycle of organisms is likely to have considerable consequences for the ecology of coastal plankton, as well as the evolution and biogeography of species. This review aims to depict the presence (and even abundance) of resting stages in marine environments and their impact on ecosystem functioning. The review starts with a description of encysted resting stages in all marine planktonic taxa, listing a total of 501 species with known cysts, and methods and tools for their collection and study. The physiology and timing of the rest period is then described for various taxa, followed by a discussion of the evolutionary implications of resting. The presence of encysted stages in different realms and phyla of plankton suggests an ancient origin and a successive diversification of morphologies that, today, roughly characterise each taxa. Ecological and biogeographical implications stem from this general framework and support the hypothesis of seasonal occurrences of planktonic life in ecosystems where productivity is suspended for a long time (e.g. in polar seas). The potential to suspend or resume life has implications for human activities, such as the risk of translocations through ship ballast water and contamination of water and seafood with toxins but also the benefit of cysts for the production of aquaculture feed. The review concludes with perspectives on present knowledge and outstanding questions to address in future studies

Prosthetic bypass for restenosis after endarterectomy or stenting of the carotid artery

OBJECTIVE: The objective of this study was to evaluate the results of prosthetic carotid bypass (PCB) with polytetrafluoroethylene (PTFE) grafts as an alternative to carotid endarterectomy (CEA) in treatment of restenosis after CEA or carotid artery stenting (CAS). METHODS: From January 2000 to December 2014, 66 patients (57 men and 9 women; mean age, 71 years) presenting with recurrent carotid artery stenosis ≥70% (North American Symptomatic Carotid Endarterectomy Trial [NASCET] criteria) were enrolled in a prospective study in three centers. The study was approved by an Institutional Review Board. Informed consent was obtained from all patients. During the same period, a total of 4321 CEAs were completed in the three centers. In these 66 patients, the primary treatment of the initial carotid artery stenosis was CEA in 57 patients (86%) and CAS in nine patients (14%). The median delay between primary and redo revascularization was 32 months. Carotid restenosis was symptomatic in 38 patients (58%) with transient ischemic attack (n = 20) or stroke (n = 18). In this series, all patients received statins; 28 patients (42%) received dual antiplatelet therapy, and 38 patients (58%) received single antiplatelet therapy. All PCBs were performed under general anesthesia. No shunt was used in this series. Nasal intubation to improve distal control of the internal carotid artery was performed in 33 patients (50%), including those with intrastent restenosis. A PTFE graft of 6 or 7 mm in diameter was used in 6 and 60 patients, respectively. Distal anastomosis was end to end in 22 patients and end to side with a clip distal to the atherosclerotic lesions in 44 patients. Completion angiography was performed in all cases. The patients were discharged under statin and antiplatelet treatment. After discharge, all of the patients underwent clinical and Doppler ultrasound follow-up every 6 months. Median length of follow-up was 5 years. RESULTS:No patient died, sustained a stroke, or presented with a cervical hematoma during the postoperative period. One transient facial nerve palsy and two transient recurrent nerve palsies occurred. Two late strokes in relation to two PCB occlusions occurred at 2 years and 4 years; no other graft stenosis or infection was observed. At 5 years, overall actuarial survival was 81% ± 7%, and the actuarial stroke-free rate was 93% ± 2%. There were no fatal strokes. CONCLUSIONS: PCB with PTFE grafts is a safe and durable alternative to CEA in patients with carotid restenosis after CEA or CAS in situations in which CEA is deemed either hazardous or inadvisable

Beam Wandering in the Atmosphere: The Effect of Partial Coherence

The effect of a random phase screen on laser beam wander in a turbulent atmosphere is studied theoretically. The method of photon distribution function is used to describe the photon kinetics of both weak and strong turbulence. By bringing together analytical and numerical calculations, we have obtained the variance of beam centroid deflections caused by scattering on turbulent eddies. It is shown that an artificial distortion of the initial coherence of the radiation can be used to decrease the wandering effect. The physical mechanism responsible for this reduction and applicability of our approach are discussed.Comment: 16 pages, 5 figure

Modelling biological invasions: individual to population scales at interfaces

Extracting the population level behaviour of biological systems from that of the individual is critical in understanding dynamics across multiple scales and thus has been the subject of numerous investigations. Here, the influence of spatial heterogeneity in such contexts is explored for interfaces with a separation of the length scales characterising the individual and the interface, a situation that can arise in applications involving cellular modelling. As an illustrative example, we consider cell movement between white and grey matter in the brain which may be relevant in considering the invasive dynamics of glioma. We show that while one can safely neglect intrinsic noise, at least when considering glioma cell invasion, profound differences in population behaviours emerge in the presence of interfaces with only subtle alterations in the dynamics at the individual level. Transport driven by local cell sensing generates predictions of cell accumulations along interfaces where cell motility changes. This behaviour is not predicted with the commonly used Fickian diffusion transport model, but can be extracted from preliminary observations of specific cell lines in recent, novel, cryo-imaging. Consequently, these findings suggest a need to consider the impact of individual behaviour, spatial heterogeneity and especially interfaces in experimental and modelling frameworks of cellular dynamics, for instance in the characterisation of glioma cell motility